Grid Voltage Rise Is Getting Worse And That’s A Problem For Solar Owners

Grid voltage rise and solar power systems

If your inverter sees a grid voltage that is too high for too long, Australian Standards mandate it disconnects from the grid. Before the voltage is so high it disconnects, your inverter may also reduce its power output in response to high grid voltages.

There’s a lot of fear-mongering about how the rise of renewables threatens our power grids, but a real problem getting real attention from the industry is how voltage rises on our mostly old and inflexible infrastructure stops customers from getting the most out of their solar PV installations.

Anyone who’s trained in this stuff already knows this of course, but I’d guess most consumers don’t realise the relationship between the voltage at the inverter and the voltage on the grid is very important. When things go wrong, the customer gets a bill showing far less electricity shipped to the grid than they expected, and someone – a solar installer, an electricity retailer, or a network – gets an angry phone call.

At a recent Clean Energy Council webinar, all four speakers – the CEC’s James Patterson, Solar Analytics’ Stefan Jarnason, SA Power Networks’ Travis Kausche, and SMA’s Piers Morton – agreed over-voltage problems are a big contributor to consumer complaints that they’re not getting value-for-money out of their grid-connected solar power systems.

The inverter has to be running at a higher voltage than the grid, so it can push power out (current flows from a point of higher voltage towards a point of lower voltage, never the other way around). The problem is every solar installation pushing power into the system lifts the network voltage just a little – and with tens of thousands of systems coming online on SA Power’s network each year, some systems are confronted with a grid with voltage outside inverter tolerance (the AS/NZS 4777.1 standard limits inverter voltage to 255V).

It’s worth noting solar power systems aren’t the only cause of overvoltage issues – as Solar Analytics founder Stefan Jarnason remarked, enough overvoltage issues occur at night-time to prove that.

SA Power Networks strategist Travis Kausche told the webinar the state currently has homes feeding 1 GW into the grid; 163 MW of that came online in 2018, and there’s up to 300 MW in the pipeline for 2019.

Kausche said the growth of solar energy “makes the dynamic range [the difference between the highest and lowest voltages seen on the network – Editor] much greater than if there was only load on the network”.

What happens when the inverter has to back off? The customer starts complaining, usually to their installer, that network feed-in tariff payments are falling short of their expectations.

Voltage rise slide - compliance

Everybody can do the right thing, but the system doesn’t work right (Image: Clean Energy Council seminar)

That can be fixed, but it’s always better to try and avoid problems than to have to rescue the relationship with a cranky customer – and preventative measures, as well as remediation, were the focus of the webinar.

Scaling The Overvoltage Problem

Solar Analytics’ Stefan Jarnason said his company’s analysis of 30,000 customers showed 50 percent of feeders had overvoltage issues 50 times a year or more, when scanned for voltages exceeding 253V for more than 5 minutes (undervoltage was, by comparison, rare, affecting only 2 percent of customers experiencing 50 or more events a year).

The more granular the data-logging, Jarnason showed, the easier to see the impact on the customer. Solar Analytics’ capture at five-second resolution clearly shows an inverter shutting down because its voltage is too high, trying to reconnect, shutting down again, and so on.

grid voltage rise - inverter shutdown graph

The orange line shows a system shutting down because of voltage rise on the grid, then trying to restart (Image: Clean Energy Council seminar)

Fixing The Problem

The challenge for networks is some of the available fixes are hard to implement on old infrastructure.

Imagine a long feeder serving many customers, meaning that to maintain voltage in-tolerance for the last customer, the voltage closest to the transformer will leave the inverter very little headroom.

As Kausche explained, the network provider can only adjust the voltage by changing the tap on the transformer if the transformer is new enough and has lower voltage taps available – but the majority of SA Power Network’s 70,000 low voltage transformers don’t have that capacity, and transformer upgrades are expensive. Substation transformers are much more capable, but don’t offer granular voltage management.

“We have these legacy old assets that can’t really go down,” Kausche said.

The webinar highlighted the role solar installers can play in remediation, with all three speakers saying that getting inverter installation and configuration right plays a big part in avoiding complaints.

SA Power Networks has changed its inverter rules to require all inverters installed on its network have the Volt-VAR setting enabled (listed as optional in the AS/ NZS 4777.1 standard), so the inverter is more responsive to network conditions.

The network is also working with other providers to produce a standard set of solar inverter settings, so at some point OEMs and solar installers have a standard configuration profile Australia-wide.

SA Power Networks is also trying to move more customer loads to the middle of the day. If an off-peak hot water system, for example, can be remotely configured, adjustment is easy, and from 2020 there will be a “sponge” tariff to encourage consumers to schedule loads such as washers, dishwashers and pool pumps towards the middle of the day.

What Solar Installers Can Do

The CEC’s Patterson pointed out system design, including cable gauge, is also important to manage voltage rise. The CEC surveyed participants to see if they liked the idea of an online calculator tool to help installers design their solar power systems – and received a 100 percent “Yes” vote; so we can probably expect to see that offered fairly soon.

SMA’s Piers Morton said the impact of voltage rise emphasised the need for remotely-manageable solar inverters, something SMA will be introducing in the near future, and said installers can also help by paying more attention to balancing systems across different phases.

If you are solar power system owner with a voltage rise problem Finn has written a handy troubleshooting guide here.

About Richard Chirgwin

Richard Chirgwin is a journalist with more than 30 years' experience covering a wide range of technology topics, including electronics, telecommunications, computing and science.

Comments

  1. I had constant dis-connects in summer when my system was installed. You could literally see the voltage rising fast as cloud cover went into a break, then bang, dis-connect. Only to re connect maybe a minute later.

    The supplier remotely upped the disconnect voltage a bit above 253v and no issues since.

    • Same thing happened here to me in Mexico. My installer tweaked the disconnect voltage and no problems since. The learning curve is pretty steep with solar for sure.

  2. ….sort of ‘Stone Soup’ in reverse.
    I asked long ago whether there were any whiz-kids out there that could modify a gee-whiz grid-connect inverter so that it would run a stand-alone operation?
    Acquired smattering of what would be involved, but found nobody who’d try it on. (The suggestion that a battery connected inverter hooked into the ‘grid-input’ might work. ) Is that workable?

  3. “The inverter has to be running at a higher voltage than the grid, so it can push power out (current flows from a point of higher voltage towards a point of lower voltage, never the other way around). ”

    Well if we had a DC grid the above would be true. But for AC a tad more complicated. Simply increasing voltage could in fact do nothing to increase power flow. What we need to do is in fact try and increase frequency at the inverter. But eventually when we get the power out of the inverter first principles will see a voltage rise

    • No. It is not an more complicated. Just as in DC, AC also will only flow from high voltage to low voltage…full stop end of story. The size of the voltage difference and the impedance of the link directly dictates the amount of power that flows (or probably more correctly, the amount of power that the inverter wants to put out and the impedance of the link determines the voltage that the inverter needs to apply to export that much power). And this is why voltage “rise” is the problem, because it is often this rise that triggers the voltage porblem in the inverter, ever when in some cases the voltage at the point of connection to the grid might be in spec, and why installers should be doing voltage rise calculations and keeping that in spec by increasing the size of the wires to the house when needed. Frequency does not come into the equations anywhere.

      I think you adding 1 and 1 together and coming up with 11 when you bring up frequency. Yes, frequency is important in the management of the grid. Usually when there is an oversupply of power into the network, the frequency will tend to rise, and when there is a lack of supply, it will tend to fall. And this mechanism is used in inverters to throttle supply when things get out of range, This “inertia” from spinning power generators helped keep things in balance. But it has nothing to do with the flow of power. Our grid tied inverters (and all generators on the grid) in fact have to actually match the frequency of the grid as it fluctuates.

      • Not quite. Changing the voltage on an AC generating device changes the reactive power power output. And that can be either to the generating device or from it. It is the method by which reactive power is controlled from all generators including inverters . And for those states where power is required to be delivered at 0.8PF lagging (from memory) it done by varying the voltage. Wwhich makes the VD problem a lot worse as this any change from unity PF increases current flow and hence more VD.

        Real power flows are increased by ‘trying’ to increase frequency. On a conventional generator this is from opening control valves. On a grid tie inverter it is a pile of electronics.

        • Sorry, to me that looks like adding 1 and 1 and 1 and 1 together to come up with 1111 and in my mind and further confusing what is a comparatively simple issue with half truths. While clearly you have some understandings behind some things, but to me it seems like a case of misinterpreting what you have learned. To me your logical seems to be flawed, probably too much to go into here. BUT you speak with great authority, and if this is backed by real knowledge and experience, I am always keen to be educated by those that might know something that I don’t rather than risk continuing to live in a world of ignorance in the off chance I am wrong. And maybe the accepted laws of physicals have changed and you can educate me about some new development that has changed everything. After all, my Electrical Engineering degree was 30 years ago, and in truth since I have not worked in building generators or inverters, and don’t pretend to be an expert in grid transmission or generation so it is not my area of expertise. But I do have a reasonable understanding of things and probably more importantly base principles that tend to drive this. But maybe there has been fundamental changes which makes a large part of the fundamental principles wrong (possible by unlikely)…..or more likely I was too drunk and did not go to that lecture so happy to be corrected if that is the case.

          But the realities is that the laws of physicals, and flow of electricity and power flow do not pander to a bunch of self appoint experts on the internet speculating about it (including myself in that). They are governed by tried and tested mathematical principles. So if what you say is true, can you point to any documentation or equations that support what you are saying, so I can educate myself.

          The whole AC is more complicated than DC is really half true. But reality if you look at any period short enough, it is exactly the same and we probably don’t need to confuse anyone sort of an electrical engineer with the complexities. Only difference that does make it a bit more difficult is that capacitance and inductance does introduce some factors that can mean we need to take these into account and this means that voltage and current is always changing and not necessarily in sync with each other as they would be in a static DC circuit (or more correctly they are in sync with each other, but can be phase shifted so current lags or leads voltage which can affect PF). But they don’t fundamentally change the simple principle that power ALWAYS flows from high voltage to low voltage, and as long as 2 AC sources are in voltage sync as they are required to be in the grid, voltage will always flow from the high to the low voltage source. Full stop, end of story. Noone needs to read on from here, unless you are not convinced of this VERY simple principle.

          To support what I an saving I only have to point to ohms law and power equations which exactly predict voltage rise and fall on any connection. Most people will know of ohms law as I = V/R. ie assuming constant resistance, we can see that current is directly proportional to voltage drop/rise. Sure, AC DOES make a things a little more complicated deep under the covers because of constantly changing and not always in phase values for I and V. And also because any transmission like will usually have some element of capacitance and inductance, so we need to adjust ohms law to the one that is applicable for for AC circuits. This is almost the identical I = V/Z where Z is impedance measured in you guessed in ohms!! So again, we can see a direct relationship of current to voltage for any particular impedance that can be used to calculate the voltage rise or fall. Notice there is no frequency in this!! But wait I hear you say, because you know enough stuff to be dangerous. Impedance IS affected by frequency if there is any element of inductance or capacitance on the circuit. This is because you know that 2 of the 3 components that make up impedance is because of capacitance and inductance of the circuit. And both capacitance and inductance are directly and proportionally affected by frequency as any 1st year student knows (inductance is proportional and capacitance is inversely proportional). Added to that practically all AC transmission lines will have elements of both inductance and capacitance by their very nature. But this relationship for a transmission line is small because the impedance is made up of inductance, capacitance and resistance of the wire, and the resistance of the wire is I suspect the most significant factor and not affected by frequency. In addition, even if we incorrectly assumed all the impedance was due to inductance and capacitance, in the grid the frequency changes are relatively small proportionately which will also limit their impact. Where I am live, the last 24 hours the fluctuation has been less than 0.4% (despite my generation swinging between 0 and 14kW). NEM I think targets is 6% and things would be going pretty wrong when these events happen and should be very rare. So you can see, in the extreme, the difference might make to I = V/Z is bugger all in the normal operation in the grid and can probably for all intensive purposes, can be ignored. Its impact is a very small % of a very small % making it pretty insignificant. Now we also have the power equations of P = IV. Again, notice, no frequency in this calculation. So if we assume frequency plays a trivial roll in practical power transmission impedance as outline, and if we put these 2 equations together, the ONLY way we can increase output from a power station is to raise the voltage. From ohms law, we can see if we do that, we will output a greater current. And we can see from the power laws those things equate to more power. Notice, while it is hard to say frequency plays no part in this, for the purposes of this discussion it is a small enough part to be ignored, and probably not worth raising it and potentially distracting people from the real drivers.

          The whole reactive power / power factor is largely irrelevant. Reactive power is really just a side effective of voltage and current being out of sync, and this does affect the P=IV equation, as you can see different values of VA and W if PF is not 1. But this is a side effect of the inductive load that a is typical of a spinning generator (and other generators and loads), and NOT a requirement. In fact if you want you can correct power factor by adjusting with additional capacitors and inductors to correct PF to 1. This does not impact on the generators ability to output power. But for the purpose of this practical discussion I can’t see any reason it would allow power to flow from low voltage to high voltage which seemed to be the thing you were suggesting could happen and the reason I commented in the beginning.

          As for broad statements that “Changing the voltage on an AC generating device changes the reactive power power output” I would love to understand what you are really saying here, and if it is what I think, where you get that idea from or what relevance it has??? Sure all sorts of generators and loads might have a power factor of less than one because of their own unique capacitive / inductive characteristics, but in truth this can all be corrected if required. And in fact, I could be wrong, but I believe your typical grid tied inverter can also output with a PF of effectively 1 or something else if that is what the distributor demands for their own reasons. As a case in point, my grid tied inverter is putting out power with a PF of 1 or close enough to it to not matter. I know this because not only because that is what the grid profile tells me, but now I think of it, I have also measured it (I get the same output from a monitor that does not correct for PF and one that does which shows in it 1). If what you are saying is true, I could never export any power which is not the case.

          I think you are getting confused with inertia, and have probably heard of its traditional importance in stabilising grid frequencies. ie when there is sudden drop in supply this inertia can supply the grid for a brief period of time (accompanied by a frequency drop), or if there is a drop in demand, the spinning generators can absorb the excess to turn it into inertia (and a side effect of this will be a small increase in frequency). But AEMO and the generators are working hard behind the scenes to prevent this ever happening and in the perfect world the grid frequency would always be 50Hz at all output levels and at all times. But this does NOT mean that frequency is the mechanism that real power is pushed to the grid. Surely if frequency was required to push power to the grid, we would see high frequency in the middle of the day on the grid when power stations are outputting at maximum load, and low frequencies in the middle of the night off peak times when there is less generation on the grid. But this does not happen!!

          I think you need to consider “grid inertia” like a manual car travelling down the highway with the cruise control set at 100km/h. Think of the car like the power station, think of the engine RPM as the frequency of the grid, and think of the hills the change in the load that is required on the grid, and power that the engine puts out as equivalent of the power that the power station needs to produce. In just like the grid with its spinning generators, the car has inertia from the mass of the car moving at 100km/h and interia of the spinning engine. In this scenario, to stick to 100km/h, the engine RPM will be a particular value (lets stay 3000rpm for arguments sake and notice I have said manual car because unlike automatics most people would be aware of there is a fixed relationship between RPM and the speed of the car assuming the same gearing). When we hit a hill, to maintain the 100km/h (50Hz), the cruise control will need to inject more fuel so the engine generate more power (same as power output from the power station in this analogy) to maintain the 100km/h / 3000rpm. We are clearly producing more power, but note there is NO increase in RPM. If the engine is powerful enough and cruise control reacts fast enough and with the added benefit of the inertia, you will stay at exactly 100km/h / 3000rpm. Opposite happens when you go down the hill, still 100km/h, but less power needed so less fuel to the engine, less power is produced by the engine, but still 100km/h and still 3000rpm. In fact you will be able to travel along on your merry way at exactly 100km/h and 3000rpm despite that you might be varying power all the way from zero (coasting down a hill) to 100% for a hill that you have just a powerful enough engine to maintain 100km/h / 3000rpm, That will happen indefinitely until 1 of 2 things happens. 1 is big long steep up hill that your engine is not powerful enough to maintain 100km/h / 3000rpm or same downhill (think in the grid of demand increase above the capacity of the generator), which even with zero power from the engine causes you to accelerate past 100km/h / 3000rpm. Lets focus on up hill. Now if the hill is steep enough to slow you down, but only short, your inertia carries you over that hill, without you even noticing any significant drop. But this inertia is effectively a conversion of some potential energy into actual energy, but you do loose some potential energy / inertia you will need to provide power to regain (shows up as a small reduction in RPM). But if the hill is longer, pretty soon, your speed and RPM will drop because you just don’t have enough power and if not addressed and the hill goes on, the car will slow until it all stalls because you have run out of power (Assuming you don’t change down a gear in the car, which is the answer in the car because you would prefer to get up the hill slowly than not at all, but this is not an option in a power station that helps the grid, because while change down a gear might increase torque, it does not increase power, so in your power station, it might help you maintain frequency, but not power output which is the important thing for a power station in times of limited supply). Same happens in the grid, the frequency drops. But it is not the drop in frequency that is the real problem. The problem is that the generator is now not spinning as fast, and that means less power and struggling to maintain voltage high enough for demanded power. As per equations above, lower voltage becomes lower power, and suddenly unless you can rapidly introduce more generation, or reduce loads, the whole system collapses, and this is what causes the blackouts (planned to protect the system, or unplanned that takes everything out).

          Now I hear you say that this is evidence to proovde your point, because the car engine is trying to rev at higher RPM and this is what is producing the power. But that is putting the cart before the horse. And as can be seen from above, in most cases the power output can be varied from 0 to 100 without changing the RPM/Hz. You are pointing of the side effect that does not actually happen most of the time, and making it the cause. Reality is much simpler in a power station. They are built and are required to maintain frequency, not increase it, or decrease it. They push power power out by rising the voltage. On our end, it is exactly the same and practically nothing to do with frequency.

          Additionally, if it was frequency that was needed to push power through the grid, and not voltage, surely we would see the frequency drop as we move through the grid from the generators. This does not happen, it is voltage drop we see, with the frequency largely the same.

          Finally, your original comment that I felt needed correcting was “Simply increasing voltage could in fact do nothing to increase power flow”, I guess if you could give me 1 real life example in the grid were this could be practically true. Example needs to be 1 where power can flow from low voltage to high voltage in a real life grid where everything is in sync.

          Now maybe I am missing something fundamental, and if so my apologies and I would really value being educated. If so, suggest you point me at the reference or calculations to the support your claims.

          • richard williams says

            Too much electro-wank here!

            This is all way beyond the capacity and interest of any but the most dedicated solarist.

            Tone it down,please. This discussion should be taken offline where you electro-donks can indulge to your hearts’ content.

          • Richard I’ve not actually read Mathews post so can’t comment on it. If it’s too complicated for you then maybe you are in the wrong place. There are many here that have views and the conversation may get somewhat technical as many of us are engineers of various degrees and want to have some input by putting their views forward.

  4. I think the graphic CEC is missing a 2 in front of the = 58v which should be = 258v unless I am missing something.

  5. Richard,
    Solar Edge inverters can be voltage limited instead of power limited. My system automatically winds back to control the voltage, so I actually help my neighbors too. My best export was 85Kw/day last christmas. (14Kw panels, 2x 5Kw Solar edge inverters. Replacement legacy system.)
    On my system, the calculations said 8.4Kw, but by using Voltage limit, I can sometimes approach 9Kw (depending on what my neighbors are exporting).

    regards,

    • Doug,

      I think when you say “voltage limited” you are referring to “volt-watt mode” which is an optional mode in AS4777.2:2015 that pretty much all the mainstream inverter manufacturers implement. You can read about it here :-
      https://www.gses.com.au/wp-content/uploads/2016/09/GC_AU8-2_4777-2016-updates.pdf

      Effectively, if enabled, instead of the inverter doing a hard shutdown when various voltages limits are reached, this mode allows for slightly higher voltage limits. But the trade off is that you will ramp down output, and in fact the ramping down of power starts at a lower voltage.

      Overall, this is better for stability of the grid, as it enables a mechanism where output is reduce when there is oversupply, and also avoids some big swings in power if big groups of inverters where all going from full power to shutdown at the same time. But for us end users there is some upsides and downsides. The upsides is that it typically raises the bar for the voltage that the invester actually full shuts down. This is further helped by the fact that when you ramp down, you reduce the current and this also reduces the voltage rise that you are creating by generating power and trying to push up, so there is effectively a double benefit here if you only cared about preventing inverter shutdown. So for anyone who implements this, there is likely to be a significant improvement in the numbers of shutdowns if their voltages are fluctuating around the limits.

      But, the downside is that the trade off for this, is that voltage limits which you must ramp down are lower than the trip voltages. So while you might trip off substantially less, you are going to be spending more time throttling your output and that throttling will be starting at a lower voltage. This means you will be spending time throttling your power, where under the standard mode, you would have been able to output 100%. For for some people implementing this, it will actually reduce their overall output if their typical voltages are above the ramping voltages, but below the cutoff voltages. Some people it will increase their output because it is better to be outputting 20% than 0%. But there is no doubt that for everyone, it will significantly reduce the number of cutoff events.

      There is no doubt this is good for the stability of the grid, so I don’t want to suggest there is any conspiracy here. But there is some truth to the fact that there will be a lot of distributors and solar installers who will love this mode, because it is effectively enabling them to sweep the over arching problems of over voltage in the network under the carpet and reduce the pressure to fix what might be an expensive problem to fix. For most people, if they don’t notice the inverter shutoff in the middle of the day, they are not likely to be aware that they might be having significant amounts of power throttled. Even for people with a good amount of awareness of what their panels should be producing can find it hard to distinguish this throttling from other factors that reduce output (ie cloudy day, heat, dirty panels, the fact that panels never produce rated capacity etc etc) until the problems is considerable which again is probably sweeping the problem under the carpet.

      It is worth pointing out, this change is nothing to do with “power limiting”, and both modes of operation are still voltage limiting. And only happen when high voltage is an issue, which should be very rare if the distributors provided voltage to the required spec. They are just different forms of voltage limiting with different pros and cons. As for “power limiting”, all inverters and modes are in fact power limited if you have enough panels and solar generation to exceed the rated output of your inverter. If you have 5kW of panels and 5kW of inverter, you will never hit this limit. If you have 7kW of panels, and 5kW inverter, and the panels all face the same way and are optimally orientated, there might be times in the middle of the say where you are hitting this limit. But this is nothing to do with any additional throttling due to voltage rise.

      Now the mode is there for real grid stability reasons, and under extreme events (ie storm brings down major power lines and isolates a city and there is a spike in voltage due to excess supply of power until all the generators can ramp down). And it is totally reasonably that solar owners like all generators help rather than hinder the stability of the grid. BUT these “over voltage” conditions should be rare and short (at least until we have much higher levels of RE penetration than we do) and should probably only happen at times when watching the news would tell you about the conditions this should be happening. Otherwise your distributor should be providing power within spec, which should be (taken directly from Ausgrids documentation) :-

      Ausgrid’s steady state LV supply voltage is within 216V to 253V at connection points under normal conditions.

      If the distributors supplied to these standards, and solar was installed to spec, inverters tripping would be very rare indeed, and we would not be having this discussion. So lets keep the pressure on to fix the underlying issue.

  6. Electrician with essential energy’s permission upped mine to 282 V Essential then ran loggers for a week did something to the grid and no more problems I asked essential tech did I need to get inverter lowered back to 255v He said no no need from upwards of 30 or so disconnects to zero

  7. Ian Thompson says

    Hi Peter

    Really? I’d think you’d have a job on your hands to increase the inverter frequency against the massive inertia of the grid.

    Thinking of a pole transformer, I’d think power would flow either one way, or the other, depending on the voltage ratio and the voltages on each side. A sufficiently increased voltage on one side would cause power to flow towards the other side. As far as I know, pole transformers do not (cannot) change frequency.

    Ignoring power factor for the moment, P=VI in an ac circuit as well – so increasing voltage WILL increase power. Also I = V/Z, where Z is the impedance – so I will go up as well. The power factor deals with real and apparent power (W vs VA).

    Unless you are thinking of a phase shift?

    • Umm – except exact words were ‘try and increase frequency’. Same as when you open the control valves on a steam turbine. But phase shift does cover it, It is known as mechanical phase shift. The position of the rotor c/w electrical phase.

      Geez – wishing I hadn’t raised it now. :-). A distraction on what is an excellent piece of where standards fail to align for the benefit of consumers.

  8. I had all sorts of problems with Voltage Rise afetr I had solar installed. In the end Power SA had to replace the line back to the Stobie pole at their expense, this reduced the voltage rise from 6 down to 3 volts when I did my own load testing and I’ve not had a shutdown event since but it’s difficult to achieve a full 5 Kw yield in summer in the middle of the day once the 253 volt level is reached and starts backing off. If its really hot and people have air cond running I can generate 5 Kw but that only happens 2 or 3 times in summer.

    The line (and cooked fuse box) was only replaced after I told them my room light was flickering one afternoon, light in fridge also was doing the same thing. They fixed it later that evening. Obviously by this stage it had become a fire risk. I would not be surprised if what I was exporting was heating up and cooking the fuse box because of bad connection. Even so this is their problem to have infrastructure that is rated to handle the current in either direction.

    Given my time over again I would have monitored and logged the voltage coming into the house so that I could make a better informed decision. This is something that should be done before solar is even installed. Voltage here last time I looked is always over 240 volts regardless of time of day. I sent Power SA logs and graphs of the issues I was having and gave them a link where they could view it in real time.

    I think it would be better if we had small transformers on each pole feeding fewer houses to make it a more even playing field.

    So the next house you look at buying first see how close to the transformer you and if close say to Real estate agent, sorry not interested, it’s too close the the transformer.

    I have Off peak water heater but Power SA refused to move it to the day time hours when I requested but now with higher export rate I think I’m better off the way it is.

    • Tim Efthymiou says

      Hi Stewart, in regards to your off peak heater. I have a time of use meter here in Sydney with off peak, shoulder, peak and control load 1. What you could do with your hws is what I did. I have two live wires going to my hws. One is off peak and the other is constantly live. I have these two wires connected to a 20A switch (which is mounted on the hot water heater) When there is going to be rainy days ahead, I leave the switch to off peak, when there is sunny days coming up (I always look at the forecast). I will switch off the hot water heater from the fuse box so it will not heat up during the night. During the day (sunny) I will switch on my hws to heat up from my solar system. (flip the switch from off peak to constant). Yes you could sell back to the grid for 12.5c per kw/h and leave the hws on off peak permanently, buy here in Sydney, my off peak rate is charged at 17.5c per kw/h so I’m ahead by about .5c per kw/h by heated up the hot water during the day from electricity produced by my solar system.
      If you don’t mind the inconvenience of flipping a switch and keeping an eye out on the weather, then this will work for you. If your one of those people of set and forget, then this will not be for you. Also consider downgrading (smaller) hws to match your family members. My original hws was 400 litres big blue, but since the kids moved out (except for one, we now have 3 adults living at home) I changed my perfectly good working hws to a 125 litre stainless steel hws that I found on the cheap of ebay. Hasn’t missed a beat since the day I installed it 3 years ago, and we have never ran out of hot water either, on a few occasions when the misses does a couple of loads of washing and washes the dogs (3) then I will flick the switch to constantly on and heat up the hws so we don’t run out when we have showers at night. This system has been working great for me and saving good money. Hope this helps somewhat. Cheers, Tim.
      p.s. do your calculations as I don’t know what they charge you for off peak and how much they give you to sell back to the grid and see if it’s viable.

    • As a comment, in NSW it seems that if your overhead cables are 16 sq mm, they will upgrade the feed. You may need to request tho…

  9. I noticed last summer that my new Solaredge inverter was regularly shutting down (maybe several times a day for about 30 minutes a time) despite cloudless skies (yes even in inner Melbourne). I was advised by my installer that this was probably because of voltage rise. How does the grid “decide” which inverters to disconnect? Are newer, “smarter” inverters more likely to be shut down than older ones, thus bearing a higher burden?

    • John,
      you are caught because there are probably old inverters feeding into the same transformer. The newer inverters have tighter voltage control than the older inverters, so will disconnect first. I suggest you ask your installer to change the inverter to voltage feed control (available with Solar Edge inverters). What happens then is the inverter will roll back to control the voltage. This means you do not disconnect, but instead the inverter output reduces. This sounds like it would greatly reduce your export, but the reality is it makes very little difference, & because you are feeding continually when the power is available, actually can increase the output.
      Also check the voltage: if it is high continually, ask the power supplier (Poles & Wires, not retailer), if the transformer voltage can be set lower. (The Grid export voltage is readable on the inverter menu).

    • What Doug calls “voltage feed control”, I suggest you call “volt-watt mode” as this is what it is called in AS4777.2.2015, so less likely to cause confusion because there is always some sort of voltage limiting. See my post above in reply to Doug’s previous post if you are interesting in more technical detail.

      Though it is worth noting, under AS4777.2:2015 if a manufacturer implements volt-watt mode (implementation of this functionality is optional under the standard), then it must be on by default. So assuming AS4777.2:2015 Solar Edge inverter that supports volt-watt mode (which it very likely does if it is brought post Oct 2016, and the fact that you have a problem suggests it is more likely post 2016 inverter, as the pre 2015 standard had much more flexible voltage limits), it is probably already on. HOWEVER, it is probably more about doing everything you can do to set ALL the voltages values as high as they can be set irrespective of if that is with volt-watt mode or not. There are ranges of values that can be set, and there is often ability to set higher than the “defaults”. But you are limited in what both is allowed under the standard, and the limits that your distributor sets.

      It should also be mentioned that “volt-watt mode” does not prevent the inverter shutting down. It just raises the bar by about 5v. But it still must shutdown when that voltage threshold has been reached. Mind you, if you have set the highest voltages you are allowed under volt-watt mode, and you voltage rise to the point of interconnect in the grid is within spec, and you are still getting regular shutdowns due to voltage rise, you should have a lot of evidence to put a LOT of pressure on your distributor to fix the issue as clearly their grid voltage is VERY out of spec and with the right technical knowledge it will be very hard for them to argue otherwise.

      As for the length of the shutdown. There are lots of different voltage limits under AS4777.2:2015. While volt-watt mode might allow you to keep generating 20% of power up to 265v, but once it trips over this and has to shutdown, the inverter then needs to follow a different set of rules before it can restart. I would need to read the standard again, but I believe that means that the inverter can’t start again till the voltage is below 253v (and it might evenbe configured below that as that is the maximuim)!!! So if your voltages does not go below that, it can never restart, even though it might be at voltages that it would be able to run if it had already started. So it only takes a small voltage rise of 2 seconds or less to switch it off, and then it might take a long time to come back even if the voltage drops substantially from the 265v.

      As Doug says, it is not the grid that decides what to disconnect. It is purely your solar inverter that decides to disconnect in complete isolation to everything else (as every other inverter on the grid does the same). And the only things that is used to make that decision is the voltage that it “sees”, and the configuration parameters configured in the inverter. Lots of things play a part in that including :-
      – grid voltage at your point of interconnect (hassle your distributor to deliver you power that is in spec)
      – voltage rise (or drop if you are net importing) of all the wire between the point of interconnect and your solar inverter. Make sure all your connections as good, and make sure all you wires are big enough for the size of the solar to keep the voltage rise to less than 2%, and the bigger the wires the better, because it all adds up.
      – what values are actually configured in your inverter (speak to your installer and make sure they have set everything as high as they can set them).

      Suggest working on all of the things above to fix your problem.

  10. Richard parsons says

    Hi.
    Valuable and revealing article.
    Suggest look at nulux and ecojoule in the illawarra for the next piece on available solutions for grid overloads and imbalances.
    Good luck

    R

  11. Anthony Marsh says

    Our Grid voltage for Australia has been reduced from 240V to 230 Volts, but someone must have forgot to tell our network operators, as almost all old and new pole and pad mount distribution transformers are set with a secondary output voltage of 250 Volts from whichever High Voltage it is built for, 11kv, 22 Kv or 32 Kv, this was fine for the old standard voltage of 240 volts most network operators allow 10 volts drop under full load from the transformers low voltage terminals to the furtherst point of common coupling on that transformers LV distribution line which would leave a voltage of 240 volts, with today’s standard of 230 volts the transformers outputs should be set to 240 volts allow a 10 volt drop would give an output of 230 and prevent voltage rise issues during the day when solar is feeding back, this would require every distribution transformers Taps to be changed individually or an easier way would be to reduce the high voltage to all these distribution transformers via the transformer in the zone substation by 2.5% and almost all voltage rise issues with solar would disappear, but getting network operators to change there ways is like beating your head against a brick wall

    • Lowering the voltage in the HV feeds also means the current in the cables would increase.

      High voltage feeds are used to make it easier to deal with losses in the cables and also allows thinner cables to be used, These would have been designed for a maximum current level.

  12. Our inverter was tripping out and the line voltage was peaking at 276v AC RMS!!! We logged a fault and they retapped our transformer on the street, and we are back around 250v. I wonder how long we were up over 270v as I only noticed the inverter was tripping out by pure accident.

    • Philip Shaw says

      As I understand it, to go over 258v output from your solar PV is absolutely illegal (for safety reasons), so if this is happening, the settings on your inverrter must be wrong. You should get it checked ASAP. As mentioned elsewhere, the inverter must push power out a couple of volts higher than the grid to allow export.

      Even 250v is at the high end of the allowable range, and should not default around there.

      • The main issue is here is too many volts on the local house wiring will place stress on appliances. In such circumstances the installer needs to do the proper load testing procedure to determine what is being lost.

        There will be some resistance in the cable running back to the pole the house is connected to. This will drop volts across it and will result in wasted power but is normal (no such thing as a perfect conductor) as long as it’s in good condition and within specifications.

        The Grid will act as a voltage CLAMP so will limit the voltage depending on what is being used on the grid at any point in time. If not much power is being consumed on the line by others then your potential exported power won’t be fully realised as there insufficient load to clamp it and as a result you end up with more voltage rise at the Inverter output.

      • I wish that statement was true, because if “safety” of voltages above 258 was an issue, that it would be much easier to get traction with the distributors to do what they should be doing to tap the voltage down to the levels that are required to provide. But it is not a safety issue as the network needs to be specified to safely handle voltage well above this, and you will see spikes in the network well above this from time to time as a matter of course.

        As further evidence of this, there will be a crap load of solar inverters out there configured with voltage cutoff parameters set well above 258. You would need to comb the fine print of various AS4777 documents about what was allowed, but caring much about voltages (at the 253-258 level) was a recent thing. But I think you will find it would be pretty standard for pre AS4777.2015 (only mandated for sale from the end of 2016) will be routinely set with voltage cutoffs at much higher values. For example my pre AS4777.2015 is set to 270v.

        Even AS4777.2015 inverters are allowed to output 265v under particular circumstances (volt-watt mode).

        The voltage issue in the grid is largely with the distributors not tapping down to the required standard which was change a while ago down from 240v to 230v (assuming proper install and ensuring your voltage rise is in spec). But even before that they tended to run on the higher end of the voltage range I assume because for them, lower voltage was more likely to create bigger problems than higher voltages. As as seen here, volts tend to be well above that standard. This is compounded by the fact that the distributors are loathed to do anything about it. So when they deliver something out of spec, and we have new inverters that assume distributors and delivering to spec, then we have the issues.

        Now we need to be careful about coming up with all sort of conspiracy theories about why the distributors don’t fix it. Eg I think the theory is to sell us more power is pretty baseless, and for most things the voltage will not make much differences to the amount of power we buy. As others have said here most inductive loads will only use as much power (which is what you pay for and not volts, amps or even VA) as they need irrespective of voltage, your hot water heater and other restive loads might draw more power with higher voltages, but that usually only means your hot water heats up quicker, and shuts off sooner for the same overall power draw. There are only a few things that might draw more for little benefit, but even they are getting less. eg if you have incandescent light bulbs, they will draw more power and burn brighter. If you can then turn lights off because others burn more brightly, it would be a zero sum gain, but I guess in other cases this is not practical to do, and you will use more power and live in a brighter house and probably have bulbs burn out a little sooner, and other electronic components not last quite as long as they otherwise might, especially if they were designed for lower voltage (but this is probably no a massive big deal, as a lot of things are now designed for a wide range of world voltages).

        Maybe you could argue that the whole industry is tuned to discouraging solar. But I suspect there is no conspiracy here, but just no particular gain from the distributors to fix, so low on their priority list.

        Arguments that they can’t turn the voltage down, because this will increase current and potentially overload the network I think also misses the main points. 1) we are only talking it down to be with the national spec, so we are not talking about turning it down to a point where this should be an issue. And 2) turning down voltages does not necessarily lead to increased currents. For example, turning down voltages will reduce the current draw of resistive loads like your hot water heater. Sure, devices that use SMPS etc, are likely to draw more current to ultimately draw the same power, but there are swings and roundabouts, and if they were still delivering to spec, it would not be an issue. And if it was, it is definitely an upgrade that should be happening anyway.

        The reality, is there are good reasons for the voltage limits in solar inverters that are generating power, and it has nothing to do with safety. And the more solar there is there, the more important these limits are. For example, when there is more solar than demand on the grid, if voltage rise is not checked by throttling and shutting down inverters, there will be more problems. So the rules are there for perfectly valid and good reasons. But what is missing is that we have a grid that is not delivering to spec, and when this happens we are being curtailed when there is no good reason to do that, other than the default grid output is too high, and nothing to do with oversupply of electricity. Effectively we are playing by the “rules”, but the distributors in many cases are not.

        But the real reason it it probably difficult to get traction, is it is probably a difficult and expensive problem for them to fix which is a problem for all of us. I think you will find there is significant parts of the grid that are not built to a sensible spec for today’s expanded requirements. When cable size and runs between transformers was specified and installed, we probably all used less power. This means less current and less voltage drop between start of line and end of line. As we have all squeezed more people in, added more pools and pumps, added more AC in more rooms, and got bigger TVs and of course added more and bigger solar systmes etc, are have probably pushed the limits of the system, with more people more out of spec for more of the time. This is all compounded by lack of flexibility to tap down transforms locally which were designed for higher voltages, problems at the end of lines if we reduce at the substation etc etc. Solution is to come back and fix everywhere that is potentially a problem. So it is a whole of system fix that might include reducing voltages at the distributor, tapping down the transformers, replacing transformers, increasing the number of transformers, to reduce the cable runs and increasing the size the wire. All this is not trivial or cheap. And so if the only people hurting is not you or anyone you overly care about, the motivation is probably low to fix it for the distributors. This is especially true if the people that are hurting, and also complaining about high power prices and you know the fixes are going to cost money, and push up prices.

        So what is the fix. I recon the fix is to not ask people with solar to bear the burden (though I am sure Angus Taylor, Craig Kelly and others in power would have very different ideas). If the system is out of spec, why should we be curtailed. If the distributors don’t care enough about grid voltage to tap it down in our street and the high voltages is NOT due to oversupply of the grid, why not let us adjust our solar voltage cutoffs to be representative of normal grid voltage. If the nominal grid voltages are too high in our area, why not let us adjust up. Now this does raise a can of worms that are hard for the distributors to manage, so that is why you probably have not officially seen this yet. But probably also why as far as I know distributors are not driving around and enforcing maybe slightly dodgy fixes your solar installer has probably done for you in the lot of cases to avoid these real world issues.

        Summary is, I suspect the problem is a bit bigger than anyone wants to acknowledge and fix, and easier just to ignore. And hopefully the distributors and fixing things slowly as they go as and when they can????

  13. Philip Shaw says

    An excellent and timely article.

    We had our 6.5kW system with a 5.5kW SMA inverter installed early last year, I am not an electrically qualified person so it took me a while to get my head around understanding all this stuff. Anyway, for several months we were plagued with overvoltage tripping the system out, numerous times per day. It took some to-ing and fro-ing with both SAPN who turned the tap down a bit, and our installer who upped the settings on the inverter, and by the beginning of this year we were finally getting an ideal yield curve on fine days, flattening out at the mandatory 5kW output limit. I do understand that inverter voltages need to be slightly higher than the grid voltage at the supply point.

    So our immediate issues are resolved, but I have continued to log the AC voltages at the inverter several times every day, and during the day before and after noon the voltages almost routinely go over 250 volts, and quite often over the standard max of 253v, and from time to time over 255v!

    Rarely if ever do voltages drop below 240v except at night.

    A couple of points emerge.

    It is some years now since the Australian standard voltage was reduced from 240v to 230v, with tolerance of between 216v and 253v. It is obvious that SAPN (and for all I know other suppliers too) have done nothing to reduce voltages to that new lower band. Durting the day they are nudging up around and exceeding the high end most the time.

    Secondly, an engineer friend of mine tells me that, except with thermostatically controlled appliances, supply at higher voltages means the consumer is buying more electricity than he/she needs to. This might be only small beer for one domestic consumer, but if you add in all consumers including industrial consumers, it means that the utility companies are selling WAAAY more electricity and hence generating WAAAY more revenue than would be the case if voltages were kept down around standards. No wonder they would be tardy about reducing grid voltages. If this is actually so, then it is a scandal.

    Would be interested to hear views on this issue.

    Finn Peacock, I’m going to email you about this issue too.. Cheers

    • In theory any element type heater (non inductor type loads) will draw more current if above the appliance rated voltage. If it’s a heater then it probably won’t really matter as the room will warm up quicker and the thermostat will switch in and be on for less time if it has one but stress on the components is an issue.

      If using Inductor type loads such as Switch Mode Power Supplies (SMPS) then it is more complicated but modern TVs and appliances use SMPS these days and they can operate on a wide range of input voltage by adjusting the Pulse Width Modulation (PWM) to generate the required power. Modern plug packs (Wall Warts) use SMPS technology. Also modern Air Cond and modern fridges also use Inverters I believe are based on this technology. I never use element heaters in Winter and just use the Inverter Airconditioner instead.

      If you have an element Hot Water Service then it also would just heat up a bit faster and cost the same in the end.

      Modern lighting like LEDs depending on how they are powered may make a difference. If the LED light uses SMPS circuit that’s good, and probably the same with CFLs.

      Incandescent light bulbs (do people still use these?) will use more power if the voltage rises above rated voltage and give you more light and heat output and no doubt will shorten the bulb life especially when first switched on.

      I wonder how many that have those CHEAP 3 speed $20 pedestal fans realise that using the lower setting won’t save power because of the way they are wired up.

    • Hey Philip,
      I work for an audio import/distribution company and with the introduction of SMPS (Switch mode power supplies) in most audio equipment, we deal with a substantial (although within manufacturing tolerances!!!) failures of these power supplies due to over voltage. This is something that as you mentioned about Australia telling world manufacturers that we were dropping to 230VAC on the grid, has never actually happened. QLD & WA have one of highest rates of failures for us. I know this comment has nothing to do with Solar power, but i have to agree that the financial gain you mentioned by running at a higher power range does not help the consumer or the importers of the type of equipment we distribute. We have questioned the power companies in various states of Australia and generally get the wall of silence put up in front of us. Regarding the gain of solar installations, the electrical governing bodies do need to get together on this one before solar becomes a waist of time.

  14. Philip Shaw says

    Our incandescent range hood lights were burning out regularly – they were made for 230v.. Finally found an LED alternative – no more probs.

  15. I want to touch on this voltage rise issue again. I agree with the article that part of the problem is where after the transformer you are located. Basically the further away from the transformer the better off you are, closer then expect close to the full tap voltage.

    I believe much of the Voltage Rise problems is because some Installers may not be conducting the proper tests to determine if the feed-in right up to the meter box is compliant. I believe this is part of the legal requirements of Solar installers before installing? If a problem is found and it’s on PowerSA’s side then I understand it is the responsibility of PowerSA to fix it and bare the full costs involved. They are not the ones that come out to test it in the first instance, they just wire in the new meter, the Installer must conduct the test and notify them if there is an issue. Obviously this would simply hold the install job up.

    How many installers do this test BEFORE coming out to install the Solar system on the day? Are they required to submit the paperwork back to PowerSA? If not then why not?

    Now as Solar installers are competing with each other and don’t want delays holding things up I have to wonder if the tests are actually being carried out and if they are then they really need to understand what the test is for. I believe the proper paper work has to be supplied to show this test has been completed and passed before installing the Solar???

    When I had issues here with Voltage Rise shutdown events PowerSA sent out one of their CONTRACTED Electricians to test. I was out at the time when they did the test. The Electrician called me on my Mobile and said he had done some tests and found no problems. So I asked him what did the test involve and his reply was he measured the voltage in the fuse box and it was fine!

    Hello! Did I say that loud enough? — HELLO!

    The Electrician had attended late in the afternoon on an OVERCAST day. I said his test was flawed and I had to explain what he did was NOT a test for the Voltage Rise problems I was having. I had to explain to him it was an Overcast day and late in the afternoon so absolutely no chance of a Voltage rise issue occurring under those conditions. He said I’d need to get in contact with PowerSA again. So here I am a Citizen having to educate a supposedly qualified Electrician on what causes Voltage Rise issues.

    As a simple test he could have opened the fuse box take a voltage measurement and connected a resistive dummy load up and measured the voltage again to see what the difference is. Repeat it a few times just in case fridge inside decided to turn on or off during the test which would have thrown the results out. This simple test would have at least shown how many volts were being dropped between the fuse box and the Stobie pole. Now with some simple Ohms and resistive power laws these results could be used to calculate the losses at different voltage drops at a given current. The length of the cable run back to the pole was in full view so could calculate drop per meter so should have known what the problem was there and then.

    The average home owner can do the same simple test without accessing the fuse box using a plug in voltage monitor as close as possible to a power point closest to fuse box. Note the voltage measurement, now with a known resistive load such as a kettle rated in Watts filled with water plugged in close to the same measurement point switch it on and take another voltage reading while it is on. Switch it off and repeat the test a few times from the start. The Resistance of the kettle element can be calculated from the Wattage and the nominal voltage for the specified wattage i.e: R=W / 240.

    I had already explained all this to PowerSA but they wanted to hook up a Polygraph unit inside my box. Around that time is when the fuse box was overheating and I was having light flickering problems so they had to come out to fix it in the end anyway. Of course they sent back a letter stating they found no issue and that I should contact the Solar installer to change settings in the Inverter to fix the issue as they believe it was not set correctly. This was before the cable/fusebox was replaced for safety reasons.

    PowerSA wasted time hoping I would just go away. After I mentioned the word Ombudsman things started to change albeit slowly. So they sent out a contract Electrician (as mentioned before) just to show they had done SOMETHING to buy themselves more time. In the end I was correct in what I was claiming because after the Fusebox incident and cable being replaced I’ve not had any issues with Voltage Rise since apart from the old technology transformer causing me to have constantly well over the nominal 230 volt level which I can’t do anything about.

    • Sorry, calculate current in kettle I=W/240.

    • richard williams and anyone else who wants to keep it “simple” – suggest you skip the post to avoid the risk of offending you.

      Actually being further or closer to the transformer is neither a good thing or a bad thing. But I would prefer to be closer, because going forward there is more likely to be upsides than downsides. What it will be, will depend on the individual circumstances of how you neighbors and you use power. But in a lot of cases, being further from the transformer will be a bad thing. And the more solar is installed on the line, the more likely it is to be a bad thing in terms of voltage rise being an issue for solar.

      You see the voltage you will see at any point will be the voltage that comes out of the transformer plus or minus any voltage rises or drop that happen as a result of the impedance in the lines between the transformer and the point of supply MULTIPLIED by the current in the wire (or more correctly each section of the wire because that all needs to be calculated separately due to different currents on each section as each house adds or subtracts their demand/supply). The impedance of the line will be approximated on the resistance of the wire / m (dependent on the what the cable is made of and size with bigger sizes reducing resistance) times length. The voltage rise or drop on each section will be a product of the length of the line, and the current that flows on that section. From this you can see no current, means no voltage drop, but also the longer the line, and the greater the current the more the voltage drop or rise depending on which way the current is flowing. At night when there is no solar generation (or if net demand is positive even during the day), this will be a voltage drop from the transformer, and the people closer to the transformer will see closest to the transformer voltage, and the people at the end of the line will see the greatest voltage drop. This will not only be as a result of their current requirements, but also the additive current at each stage from each user up the line. Supplying adequate voltage to the person at the end of the line when everyone has their AC running and drawing peak demand is 1 of the reasons I am sure the distributors want to run voltages on the high side to counter the affects of this voltage sag.

      Of course if the line has high solar penetration and the line is generating more than it is using, this will translate to voltage rises as we go down the line. So in this case the people at the end of the street will see the largest voltage rises. This will be as a result of not only their own contribution to the voltage rises, but everyone elses contribution as well.

      Now if in this street, everyone in the street is a big consumer of power 24×7, except the person at the end of the street, who has a big solar system, then it might be an advantage being at the end of the street, because all of the load for upstream properties will be dragging the voltage down, and reducing the voltage at the point of connect for the person at the end of the street. But remember, when the upstream houses are not drawing power, the voltage at the end of the line will be exactly the same as at the transformer. So rise/drop does not happen at a fixed rate the further from the transformer you are. It is directly proportional to current. No current means no voltage drop/rise.

      Of course the reality is much more complicated, and it is not unlikely that on some sections of the line between transformer and end of line might be contributing a voltage rise (because big solar system is pushing power to to the transformer, but on other sections there is a voltage drop, because maybe the upstream house is a big consumer of power and using all the power from the downstream houses and then some.

      So all we can really say, is the further from the transformer, the greater the potential swings either way, and the greater the impact that other peoples usage pattern could have on you. This might help you if you are lucky, or be a hindrance depending on the particular circumstances. But either way your experience will be more dependent on other peoples behaviors, which i personally would prefer to avoid.

      As for whether the installer does what they call the voltage rise test, probably comes down to what the distributor requires. In Ausgrid NSW, I think for installs of over 5kW, they want a voltage rise test done and the results submitted with the application. I assume they reject it if it does not pass the voltage rise test. The voltage rise test is just a test of the impedance from the meter box back to the Ausgrid connection point in the street (sparky connects to both ends and measures). From this they can calculate the voltage rise applicable to your feedin line based on the size of the proposed solar system with V = IZ. Depending on where your dodgy joint was, it is likely that your impedance test would have picked that up if done, especially if the impedance was significantly greater than would be predicted by the length and size of your wiring. All wire will have a specification of resistance based on ohm per meter which will be depend on type and size of wire and then it can be multiplied out for length which will give a rough idea of the impedance you can expect..

      Re quick and dirty “kettle test” test, the challenge becomes getting a reliable reading because for most people the grid voltage will be jumping around all over the place. One of the many reasons for these voltage fluctuations, will be changes in load upstream, and particularly changes in load not only in your house, but people upstream (and even downstream of you because if someone turning on big appliance downstream of you, still means more current on the line between you and the transformer and associated impact on voltage drop). Obviously you recommend taking a number of readings to reduce the error and help overcome this short coming, I recon it is still a useful tool I have used myself to help understand what is going on, and apply pressure where it needs to be applied. But a couple of suggestions :-
      1) Kettle is still a relatively small load, and changes from the kettle might be small enough in the general fluctuations to get a clear idea depending on where you live. Getting a bigger load you can control, will make it a little easier and reduce some of the errors. So some ideas 1) pick a good and consistent solar day, where you know the output of solar reliably, and do the same measurement of voltage before and after turning the solar off. 2) a lot of solar inverters can provide voltage readings they are taking all the time. If this can be graphed, it can be useful to visually see what is happening in a tend which can be more useful than instantaneous readings. 3) if you have traditional hot water service, often the element on that is bigger than the kettle. 4.8kW is not uncommon, so this is a bigger lead you can turn on and off and measure. In fact if you are graphing voltage, you will probably be able to see with the voltage sag when that turns off. Potentially, you could use that for your calculation. But if it is off peak, be a bit careful because the reality is multiple HWS in the street might have been turned on together, so the voltage sag might not be just as a result of the voltage rise on your connection. The calculation using I=W/240 will usually be more than good enough. But if you want to improve the accuracy which might be important if there is a big gap between rated voltage and actual voltage this can easily be done with resistive appliances like kettles and hot water heaters etc, The rating of resistive appliances can be “corrected” for voltage. Eg a 4.8kW hws element will be rated at 4.8kW at a certain voltage (hopefully it is on a sticker on the hws, or you should be able to get that in the specs). Lets say the rated voltage is 230v and actual voltage is 250v as would be pretty common. Using the power equation R=V ^2 / P we can calculate that element has a resistance of 230 ^ 2 / 4800 = 11.02ohms. Now use I = V / R to calculate the actual current going through the element at you actual voltage. 250 / 11.02 = 22.7A which is significantly above the rated current of 20A. In power terms, it means that the actual output of the element becomes 5.6kW. Note, that this is probably a bigger jump than most people expect and is disproportionate to the actual voltage rise because power increases to the power of 2 for any voltage rise.

      • I should add that “voltage rise test” for solar install, does not take into account the voltage rise of the grid between your point of interconnect with the transformer. Only the voltage rise applicable due to the connection from your meter box and the point of connection to the grid. The truth is in practice, it is both these voltage rises (or falls), AS WELL as any wiring from your meter box to your solar inverter, which in the case of a micro system, might be longer than you think. Added together and the voltage hits the threshold configured in the inverter and it all shuts down or throttles depending on the profile.

        Now the “voltage rise test” does not take into account the voltage rise beyond your point of interconnect because I believe legally it is the distributors obligation to provide power that is within specification at the point of interconnect and not just at the transformer. So technically, you should have the same right to the voltages being within spec whether you are the last house or the first. And in the theoretical world if the voltages at your point of interconnect is outside of specifications, then a quick call to the distributor should have them out to make whatever changes are required to fix this. But in the real world, that is I LOT more difficult as I have already outlined. Especially when some of this is a little outside of the direct control of the distributors. ie, as can be seen, voltage rise/fall is affected by how much people use. So your frugal neighbors that never ran the AC moving out, and new neighbors running AC 24×7 might be enough to tip the whole system out of spec, and there is no change in this the distributor would have had any control over. And maybe it is these new neighbors at the end of the line are complaining about issues due to low voltages, so the distributor addresses that by tapping the voltages up. But that might negatively impact your solar in high generation days.

        So what are the answers you can control :-
        1. when you install your connection to your property, oversize the wires they use, as for any particular current, this will reduce the voltage rise fall. Keep the runs as short as practically possible. Consider getting 3 phase power as you can spread the loads and generation across the 3 phases and this will reduce the voltage drop.

        2. make sure they oversize any cable runs between meter box and solar inverter particularly if they are any distance because this might be the straw that breaks the camels back.

        3. get the installer to tweak the installation parameters to maximise the acceptable voltages (there well likely be limitations to what they can do to comply with the distributors rules, but in many cases, they can raise some of the defaults). Unfortunately implementation of things like “Volt-Watt mode” can hid the problem from you, because it is harder to spot and notice throttling (was power halved for that hour because of throttling, or was it because clouds came over), than the inverter shutting down and up. But be aware of the differences.

        4. when power is out of spec at the grid, complain to the distributor and get them to fix (often easier said than done).

        Bottom line is in theory (not practice) infinite sized cables makes the problem go away, and so many installers and distributors save costs by only making it “just big enough” to save costs. I am a big believer of do it right once. It might cost more upfront, but can save money at the back end. It never ceases to amaze me how many sparkies are not aware of this issue, and will use cable that is rated to ensure your house does not burn down, and less around addressing the potential challenges of voltage rise / fall. The former bar is a MUCH lower 1 to jump over, and most of the regulations are only based on this lower bar. So asking and paying the installers to oversize the appropriate cables can help.

        What can the distributors do :-
        1. tap down the voltages so at least they are closer to 230v. In truth, compared to were they are at, even tapping down to 240v would probably be a MASSIVE improvement from where we are today for most people and well above the current nominal voltage. At my place, I NEVER see anything close to as low as 240v, even in the middle of the night and when I have big draws from my hws which probably pulls down voltage on that phase by 5 volts or more.

        Beyond this it gets more difficult :-
        1. bigger wires.
        2. more transformers to cut down the lengths of the runs, and the number of people on the runs.
        3. etc

        • I had an argument with the Essential energy inspector about my feed: I have a 2 phase rural supply. Effectively 480v, neutral centre tap. I could not convince him that the neutral cable did not conduct ALL the 2 phase neutral current. Actually, the Neutral cable only conducts the difference between the currents, due to 180 deg out of phase. In the real world, the difference is marginal anyway, because the system only reaches full steam a few hours a day. Still annoying tho!

          • Matthew Swainston says

            Now you are getting technical. But for sure, the neutral would be carrying no current if all phases were in balance, and all loads where resistive and PF 1. Obviously this rarely happens, and so there is almost always at least some current on the neutral. But as long as it is not completely out of balance, a lot less current runs on the neutral than actives for sure.

            What we see as “voltage rise” or “drop” is in fact as result of the voltage rise/drop on the active cable + the rise/drop on the neutral cable. So if a balanced 2 or 3 phase system reduces current on the neutral, then this should also play a small part in reducing voltage rise (even beyond the benefit of splitting the current over 3 wires plays in reducing the voltage rise by 3). Definitely a benefit overall. But if you really want to make your head hurt, there are some downsides as well. For example, if you are generating on 1 phase, and have a large load consuming power on the other phase, this will actually increase the current on the neutral, and in turn increase the voltage rise. But this sort of thing is 1 of the many reasons the distributors want to keep the phases balanced and the reasons there are rules under AS4777 to support that (ie the rule that 3 phase inverters or even now micros system must shutdown when the phases are out of balance….ie the rule that causes so much grief for people who want a battery system to keep the solar running in a blackout even though in this case it would not have any impact on the grid as during this operation you are isolated from the grid so this is irrelevant).

    • Stewart,
      you are not actually correct about the distance from the transformer. Yes, if you are further away, the voltage drop will lower the voltage, but unfortunately that works against you when you grid feed.
      When grid feed happens, the voltage at the transformer must be higher on your circuit for current to flow out, so the voltage at the inverter is the Transformer voltage + voltage loss in the cable: this reduces the inverter overhead.

  16. Tony Austin says

    Any differences in behaviour for a micro-inverter configuration (multiple panels connected in parallel) versus the more common single inverter (single or multiple chains each with multiple panels connected in series)?

  17. At one level, it is EXACTLY the same issue with micros and string inverters. ie inverter has AC voltages thresholds it needs to throttle or switch off under. This has nothing to do with the DC/Solar side of the inverter. Only the AC side upstream of the inverter. These thresholds and behaviors are exactly the same for sting and micro inverters.

    But in practice there is a difference, because the micros (which are usually up on the roof under the panels) tend to be further away from the typical string inverter (usually connected close to the meter box to keep cable runs short and cheap). So the inverters have to act on the voltage at the inverter which includes the voltages rise of the cable up to the roof. This can mean that they see more voltage rise than a string inverter by the meter box. Remember voltage rise is a product of the current on the cable x impedance of the cable. And impedance of the cable is proportional to its length, and larger cables have lower impedance. So mitigation to “reduce buy not eliminate” voltage rise is :-
    1. go bigger thicker cable which will have lower impedance
    2. put more cables in (halving the current by using 2 cables, halves the voltage drop). To some extent this happens anyway with micro setups as there are limits to the number of micros they put on the 1 string, and well as panel placement might made it logical to have more strings.
    3. obviously keep cable runs as short as possible (which is probably harder for a micro setup than a string setup).

    Obviously all this is cheaper/easier to do if string inverter is by the meter box instead of on the roof.

    But lets remember, if the distributors gave us power which was in spec, the bit of voltage rise that came from the cables in our home would be of little or no consequence for the vast majority of time. This is only an issue because all too often the grid voltage is too high and often this is NOTHING to do with solar. For sure, sometimes it will be an issue with “too much solar on the line” or poor quality solar install that has not designed around voltage rise. But unfortunately “solar” is often used as a completely invalid excuse to do nothing about what is nothing more than a grid voltage issue that is NOTHING to do with solar.

  18. Ian Thompson says

    Hi Richard

    With the utmost respect Richard, I feel your use of the word “fearmongering” (about voltage rise) implies a level of malicious deception – which is a bit of a stretch when voltage rise is a real thing that impacts many of us, as many of our posts serve to attest. The following link talks also about undesirable renewables “curtailment”, showing this issue to be an international one – not just limited to here in Oz.

    https://physicsworld.com/a/curtailment-losing-green-power/

    You also refer to “old and inflexible infrastructure”, which again with respect I feel is quite misleading. In fact, the issue is one of simple Physics – Matthew says “it is NOTHING to do with solar”, even though in an earlier post he correctly got onto the technical issue involved, but I can demonstrate it has VERY MUCH to do with solar.
    Here in WA for example, our Western Power is required, by law, to supply power to the premises at a volt of 240V plus or minus 6%. That is, at no less than 225.6 Vac, and no more than 254.4 Vac – a range of 28.8 Vac.
    At the time our grid was designed, the designer’s task would have been to ensure the delivered voltage, everywhere, remained well within these extreme limits, under conditions of maximum and minimum loading no doubt with some margin for surburban infill, increased use of more electrical products, etc. – whilst at the same time to minimise Capital costs by using the smallest wire sizes and transformer arrangements suitable to meet these requirements.

    The issue is, that when loads are drawn across a network, there are voltage drops along the transmission lines, through sub-stations, along feeder lines, along the distribution (service) mains, and through the incoming line to the meter. These are losses due primarly to line resistance (assuming near unity power factor – something the Operators demand so they don’t have to pay for the added i2R losses – when the line’s impedance becomes close to a pure resistance). The Operator’s job is to select transformer voltage tappings high enough to ensure both that the customers at the end of the line do not drop below the minimum limit when the grid is at maximum demand (with high resistive losses), and low enough so that customers at the “head” of the line are not exposed to voltages that exceed the maximum limit when the demand is low (e.g. late at night – which explains why voltage rise may become an issue then – when the losses in the transmission and feeder lines are also reduced, kicking up the transformer incoming voltage). Note however in the absence of soalr power injection, that the end of the line will still be lower than the head of the line, so may still remain below the maximum limit even though the head has exceeded it.

    We must remember that many existing grids were designed quite some time ago, probably well before the advent of significant solar being expected.
    However, now we add distributed rooftop PV to the mix. Quite obviously during times of high solar generation and low demand, instead of the grid voltage dropping down the line, the voltage drops due to resistance will work the other way around – as the current is flowing out – jacking up the end-of-line voltage. But the transformer tapping still must be set high enough to prevent excessively low end-of-line voltages during evening peak demand (with no solar assist). You can see that as more and more PV is added, this problem becomes more and more difficult – and eventually it will not be possible to achieve the regulated voltage limits whatever is adjusted.
    Like I say, this may not have EVERYTHING to do with solar, but it does have a LOT to do with it (another example is increased infill, and increased use of electrical products, room heating, etc. – these act to increase the voltage drop during peak evening demand, necessitating a higher transformer tapping to prevent excessive voltage drop then).
    In WA, there is an investigation into relaxing the Regulations a little – however I feel this will only be a short-term “band-aid” fix.
    The link above shows this is not an isolated issue, as renewables curtailment is happening worldwide – in some places making new investment in renewables unattractive. This is an important issue for us all.

    Right now, even with the limited curtailment some of your contributors are experiencing, with the substantial subsidies I have no doubt at all that new installs will get their money back before too long, then make substantial energy cost savings for years until their panels finally die.
    There is a solution – we could duplicate transmission lines and feeders, and upgrade distribution networks with heavier conductors to reduce the voltage swing between generation and demand – but this would cost money.
    In fact, NSW was accused of “causing” energy prices to increase, by “gold-plating” their network – however I feel they were probably only providing the increased infrastructure necessary to support renewables.
    Right now, you could also ask your vendor to investigate changing the transformer tappings down a little. In my own case I had to push the issue via my local member, but eventually Western Power were able to “tweak” the sub-station trandformer a little – my local voltage had been hitting the upper limit at times causing my inverter to “throttle back”, but now the peak seldom goes beyond 245 Vac so all good (minimum here ~ 235 Vac, but we are near a pole transformer and not far from the sub-station).

    We cannot have our cake and eat it – in order to employ increasing amounts of renewables, it is inevitable we will eventually have to pay for increased balancing (storage, transmission, spillage) costs – or else deal with curtailment – there is no way around this. That is why I always have a problem with the ongoing mantra that “solar is cheaper than coal”. Maybe it is, maybe it isn’t, but unless the increased infrastructure costs necessary to support widescale renewables is added into the equation, then I feel we may be deluding ourselves.

    • All good points Ian. But if you are going to quote me, suggest you get the quote right and in context. When you incorrectly quote me saying “Matthew says “it is NOTHING to do with solar” which suggests I am suggestion solar plays no part in voltage rise which is clearly incorrect and certainly NOT something I would suggest. But reading carefully what I really said was :-

      “This is only an issue because all too often the grid voltage is too high and often this is NOTHING to do with solar.”

      There is no doubt solar plays its part as does everything else on the grid in having an impact on voltage rise and drop. Sometimes solar helps reduce bad voltage drop on long lines, and sometimes it is a not so good thing causing voltage rise and pushing things beyond the specifications. But if distributors delivered voltages that were in specification, the voltage rise from solar would mostly not be an issue. Technically there is a small area of crossover where there might be an issue. eg for most of Australia our nominal voltage is 230v to align with the Australian Standard shift from 240v to 230v. For example Ausgrid is supposed to deliver between 216v and 253v (this is pretty typical over here as this is driven by the Australian Standard with various versions of AS 60038 that it look like Western Power is a bit slower adopting). Technically if they delivered in specification at say 253v (right at limit), and we have 2% voltage rise from solar (again within the specifications), then we might punch well into the range where solar might be throttled (think 255v). But the reality, if you were reliably delivering between 216v and 253v, 99% of the time you would be well below the 253v and have enough headroom.

      If this issue was only an issue because of solar, then we would expect to see high voltage aligning with high solar output, and would NEVER expect to see high voltages at night. But the reality that is just not the case in a LOT of places in the grid. In fact where I have looked closely (limited sample size for sure, but not insignificant none the less), it is more common for the high voltages to be at night, and this suggests that the main contributor to the higher voltages is NOT solar. In fact to support that have a look at this https://www.abc.net.au/news/2018-11-08/high-voltage-fuelling-increased-electricity-consumption/10460212 . Basically average MINIMUM voltage across 12,000 meters all across the NEM was 241.6 volts and 1642 were above the 253 threshold while just 6 meters were below the 216 threshold which pretty well blows any assumption that it is all caused by solar or required to balance the start and end of the line out of the water. And in fact it is more likely just the grid is tuned for higher voltages, and I assume this is likely because the distributors have made little or no progress in readjustment of grid from 240 to 230v which I believe was a published Australian standard from about the turn of the century!!!!

      Now there is no doubt the distributors do not have a trivial job in maintaining the grid the the standards they have committed to delivering for all the reasons you outline and then some. And at some stage it is open for debate if we as a community want to pay for the investment needed to keep making the changes required to keep voltages within higher tolerances (which also bring significant financial benefits which will no doubt offset some of the hidden costs of not doing it….eg more device failures). But it does not help this debate if people continue to falsely suggest this issue is ONLY because renewables/solar and dismissing it like that. In fact the more distributed nature of solar (particularly roof top solar) and batteries also bring significant benefits and opportunities for the grid to offset some of the challenges. eg then the economics of batteries are right, distributed batteries managed by the distrubotrs can be used to even out the peaks and troughs in demand and this in turn can be used to smooth out the voltage peaks and troughs caused by voltage rise/drop (whether the cost to do this can be economically done is another argument).

      But the reality is the AS4777.2.2015 has been developed working on the assumption that distributors DO deliver power within specification which unfortunately all the posts here demonstrate to the fact that that is a very bad assumption indeed. On this assumption these inverters would mostly be able to supply full output 99% of time, and only throttle at rare times of over supply which is all totally good and reasonable. HOWEVER, it is unfair if the distributors are not held to account for the voltage standards they have been committed to delivering, while at the same time providing little to no flexibility for the solar inverters to support voltage ranges outside of the standard. And this is my key objection. What is good for the goose, should be good for the gander. And if the distributor has been slow to tweak the nominal voltages down in certain areas to support the standard, then surely the inverter should be allowed to be tuned up for those nominal voltages. This is even more true which I believe it is the same distributors who at the drivers behind the tighter rules in AS4777.2:2015 and certainly the ones it say what we are allowed to configure and not configured in the inverters when we connect to their networks.

      I am guessing these is little to any financial intensive for the distributors to deliver to the standards, so I am guessing it is just not on their priority list. Solar owners are asked to bear the financial burden of voltages out of spec when we are throttled or our inverters shutdown. This can be a double financial blow to us, as not only do we not get the FiT, but in many cases we will also have to pay big retail prices at these times for the power we then have to import, despite the fact we have solar sitting there and doing nothing. I wonder what would happen if the distributors had some skin in the game and also lost money when they voltages they deliver us are out of spec (eg maybe we don’t pay for power at all when voltages are high). I suspect suddenly they would find practical and sensible ways of better managing this issue.

      As a side issue for those interested, here is a little paper from 2003 that covers the move from 230 to 240 :-
      https://www.nhp.com.au/files/editor_upload/File/TNL/TNL-38.pdf

      What it highlights is the change is really more a tweak of the tolerances so it is not a massive change for the distributors. So while it looks like Western Power who appears to be slow in adopting the 230v standard and looks like they are 10v higher than on the east cost, reality is they have lower tolerance for over voltages so there is only a small increase in the upper voltage (254v vs 253v).

      • Ian Thompson says

        Well Matthew – you DID complete your missive with the statement:

        “But unfortunately “solar” is often used as a completely invalid excuse to do nothing about what is nothing more than a grid voltage issue that is NOTHING to do with solar”…

        I agree with much of what you say – and no doubt there are circumstances where the voltage problem is purely a grid-design-related problem – however I suspect you haven’t thought through the physical realities sufficiently.

        Take my case example – we have never had a high voltage problem at our house for 30 years until a neighbour over the road installed PV, as did a local business on the same high-voltage distribution line. Our issue was (temporarily) fixed by Synergy, by “tweaking” the sub-station voltage tappings – presumeably by lowering the feed voltage there. They did point out they couldn’t do much, or else customers at “the-end-of-the-line” would experience voltages below the regulated minimum at evening peak loading (with no PV generation).

        Perhaps you can now see what I’m getting at – the physics is something like a long length of wire – if you have the voltage at the supply end “pegged”, then at times of high demand without distributed generation (e.g. evening peak), then the voltage at the end of the line will “sag”. To prevent undervoltage, the utility needs to possibly raise the “pegged” voltage – without the voltage near the “pegged” end reaching excessive values – there is a voltage slope down the line. This will be exacerbated by things like infill, customers using more equipment over time, etc.
        Now look what happens when the demand is low, but the distributed generation is high (e.g. during the middle of the day). In this case the “slope” of voltage is reversed – the remote end of the line will be at a higher voltage then the pegged end – and the utility may need to lower the voltage tappings at the sub-station (or even further up the line).
        With increased penetration of PV, the scope for adjusting voltage tappings becomes less and less – to the point (that we are near to here) that there is no room to move. At this point, either the Regulations need to be relaxed (our utility is looking at this), or demand and/or generation needs to be curtailed.
        Or, the network needs to be upgraded with heavier wiring as Ron has mentioned (but not an easy thing to do in “mature” suburbs, without massive disruption).
        It is really simple Matthew, the more PV, the greater the problem.
        BTW – if voltage tappings are increased to overcome low end-of-line voltages, then voltages near the source CAN experience high voltages at low demand times, which CAN occur at night (as I recall Ronald mentioning).
        So – not ALL problems are caused by PV penetration I agree – but I still suspect MOST problems are caused by PV penetration – by simple physics!

        • I think you have totally misunderstood what I am saying. I totally understand voltage drop and rise. And you will see I have written about voltage rise due to solar etc. And yes, if you have lots of solar at the end of a long thin line there might be issue with voltage rise, but at the same time no doubt voltage sage at night when there is demand and no solar. And in some case, the voltage at the end of the line will in fact balance out voltage sag and help fix the problem. But it all depends on what is running when, and no doubt if you are at the end of the line it will swing from one extra in both the day and night. Even at night you will see these wild swings. ie if there is little current on the line, the voltage will be the same at the transformer, which can lead to high voltages off peak at night. When ACs are running in the evening and everyone is doing their cooking, the voltage sag will bring the voltage done. But bottom line long thin line with lots of supply or demand at different times are always going to be an problem for voltage fluctuations.

          So yes, there is no doubt some problems in the grid will be caused by too much solar on the end of too thin a line. But is it the solar, that is the main problem, is it is the long thin line?? This is why solar is often limited and export limited in rural areas to manage the problem, by managing the solar.

          BUT remember there is a regulatory requirement that the DNSP must provide you voltage that is within spec at your point of inter connect. There is no caveats for too much solar or how long the line to your place is or anything else.

          But back to the point I was trying to make that over voltage is often (but not always) nothing to do with solar. At my place for example, I see the highest voltages at night when solar is NOT running, and those voltages are above the standard. This is very common across the network as you can read about here https://www.abc.net.au/news/2018-11-08/high-voltage-fuelling-increased-electricity-consumption/10460212 which shows the persistence of high voltages at night which can’t be blamed on solar at all. Truth is, it probably depends on where you live. I suspect the the majority of metro areas generally run voltages on the high side as per the survey outlined above. In rural areas with longer runs, it will depend where you live in relationship to the transformer. Where they are running long lines the DNSP will be wanting to run higher voltages to counteract voltage drop at times of high load down the line. So if you are at the head of the line, you will be seeing high voltages and this is more to do with the high voltage in the transformer and less to do with solar. The downside of this, is that if there is large solar at the end of the line, and high net export from that segment during the day, this voltage rise might be a problem for you at the end of the line, but especially if the voltage at the transformer was already at the high side. And you could certainly argue that is caused by solar. But I would argue they are running too high a voltage at the transformer to not allow for this, and that the real answer is that the line it too long, and wires too thin for the loads on that line, and under these conditions. Because of this I assume they are not finding a suitable compromise to deliver voltages in spec. Yes, solar contributes but it is an over simplification to blame it all on solar. Of course in a lot of cases, it is nothing to do with this, and it is just that they have an old transformer designed for 240v days that they can’t tap down enough and they want to make you go away to save them having to replace and expensive transformer.

          If you issue is the voltage at your point of interconnect is too high (and not voltage rise on your feedin which only you are responsible for) and you want to make excuses for your DNSP, rather than holding them to account, knock yourself out. But I would not mind betting, there is a reasonable chance even at the end of your long line, there will be times at night of very low load (often 5am in the morning before anyone is up, and after all the off peak hot water is hot, and before the sun is up and solar is an issue etc), where you will see high voltages at night because they have the voltage on the transformer too high. You won’t notice or care about them because if your solar is not shutting down, you probably won’t care. If you see this, you know that a big part of the “solar” issue is the transformer voltage is set high enough to not give you the voltage headroom for solar to export power on a long line. DNSP will not want you discovering this, because it will take away their already invalid excuses why they are not delivering power within spec at your point of interconnect.

          I am not saying they are easy or cheap problems for the DSNP to fix, especially for customers in remote locations and long lines to keep the costs manageable.

          But I suspect we are largely saying the same thing. Your prospective are formed by what you have seen in your area (so you think it is largely solar and assume that applies everywhere). My prospective are formed from what I seen at my area, but also measuring power quality and voltage at sights all over metro cities (where voltage as almost always high irrespective of solar), but also some rural properties where long lines are a bigger issue (and lead to wilder swings between high and low voltage depending on the load and direction of the flow at the time).
          .

          • Ian Thompson says

            Hi Matthew

            You appear to have large;y re-quoted what I wrote?

            Exaggerating the “long thin line with a whole whack of solar PV at the end” is an entirely misleading statement Matthew. As I mentioned, our “long thin line” was perfectly adequate before the days of rooftop PV – the thickness of the line was entirely adequate such that excessively low voltages were never experienced (as far as I am aware – and our Utility has been entirely strict about this) at the end of the line during times of peak demand – nor were excessively high voltages seen near the transformer late at night when demand is very low. BTW the demands and generation are distributed, temporal, and seldom synchronised. Of course adding demand at the end of the line is eventually going to require voltage tap increases at the head of the line to compensate for the increased drop – and this will result in higher voltage at night near the transformer – as we would expect from simple physics. I agree this is not a solar problem per se, but it DOES decrease the range of voltage available to deploy PV. Add PV, and we have a problem.

            Our local problems ONLY developed when solar PV penetrated significantly – although I will grant that increased demand due to suburban infill and increased demand as more technology is switched on will have exacerbated things to some degree, by filling up some of the available RANGE of voltage available for adjustment. Remember that I said we are in a mature suburb, so demands ARE NOT being added at the end of the existing line. Yes, I agree that rural and other configuration may prove different. Imagine a farm at the end of the line that adds huge generation capacity locally – and the problems this may introduce. The same applies for distributed loads and generation elsewhere.

            The concept that this is mainly caused by adoption of rooftop PV seems pretty obvious to me – seldom do we ever import more than 2 kW, yet routinely we export ~ 5 kW to the grid either side of midday – if everyone in the locale did the same, then power outflow during high generation low demand times would significantly exceed power inflow during high demand low generation times (which is after all, the configuration for which our grids were originally design for). In other words, the range of voltage for generation voltage rise, is greater than the design range of voltage drop pre-PV.

            To say that I might want to make excuses for the DNSP is again misleading – I got onto the DNSP, and after some “pushing” they were able to make adjustments to lower our supply, presumably without going outside the low voltage specification (I do know they were also looking to relax the regulated specification, obviously because the margins were becoming vanishingly small and were only going to become worse with increased PV adoption, and infill, and all those things).

            Yes Matthew, the lines are probably too small now, for the level of PV installed – I would say this is clearly a PV issue. And, there are no “free lunches” – you would have to be living under a rock to think the DNSP can go about upgrading wire sizes at no cost to anyone. Where do you think they are going to raise the necessary funds from? Perhaps this explains the doubling of our service fee a year ago! Money does not grow on trees!

            Another cost of going renewable – and I fully accept this as the way forward, but am not prepared to “fake” causes and responsibility.

      • Ian Thompson says

        The “sag” is caused by line impedance (think of resistance).
        Works both ways…

  19. ffffffairly ffffrustrated says

    As soon as it gets to about 930am our system shuts down on ac overvoltage on 1 phase (10 kw 3 phase inverter).
    It has been happening occasionally since May but I only noticed it a couple of weeks ago on one of our first real sunny spring days. It is now happening daily, even on overcast days, and our friends at SAPN can only say that “they’ve referred it to the techs”.
    At least we’re getting a couple of hours out of the east facing panels each morning before everyone else’s come on stream and after that as soon as there is enough sun for it to get to about 6kw it goes poof (derates for a bit then shuts down) and typically doesn’t come back up till about 4pm (although if a cloud comes over it perks up for 10 mins then poof again).
    So my question: can a 3 phase inverter be down-rated to1 phase (even if we have to go with the 5 kw limit) as the other 2 phases are ~ 5 and 10 volts lower, as an interim measure until SAPN actually do something?
    Signed,
    The bloke with a solar system that only works when the sun don’t shine… or:
    The bloke with a solar system that he might as well stick where the sun don’t shine…

    • Ronald Brakels says

      Sorry to hear about your problem.

      First off, here is a page we have on the issue:

      https://support.solarquotes.com.au/hc/en-us/articles/115001759153-My-Inverter-Keeps-Tripping-or-Reducing-Power-On-Over-voltage-What-can-I-do-

      Unless your installer is no longer around you should let them know, as they will probably have experience in getting SAPN to act.

      I’m afraid I don’t know of any simple way to down rate your 3 phase inverter as a temporary measure. I think given how much that is likely to cost a voltage control device would be a better investment, but even then that will be very costly if SAPN gets their act together and does something about the over voltage problem before too much more time has passed.

      • still frustrated says

        thanks Ronald. Ive been in a contact with the installer. They are being very supportive and their assemssment is that the issue is the line voltage from the street. Their experience with SAPN is it may take many weeks, perhaps multiple months before SAPN to do anything that will actually change the voltages, by the time they insall voltage loggers and record voltages for multiple weeks etc. I could go on and on about SPAN’s response to date but this is likely not the right forum for it (but at least I’d feel better about it). In short they dont seem care much…

        What do you mean by a voltage control device? Our installer knows of no interim workaround.

        • SF this is my favourite pet hate of SAPN. Been there done that with them. You will be most likely running around in circles trying to get a satisfactory outcome with SAPN. Cause could just be down to an underrated cable feed back to the pole which SAPN are RESPONSIBLE for.

          You could do my simple dumb-ass Kettle check test I mention elsewhere to see what voltage drop you see on your feed if you understand some simple electrical physics laws. Best to do that at night though to eliminate some of the variables.

          You need to show SAPN you know what you are talking about otherwise good luck! I provided Voltage logs to show problems and they kept being in denial. Then suddenly it all came good!!!

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