Why connecting your solar system to the grid is harder in NSW

grid connect solar

What are the rules for connecting to the grid in NSW?

Australians love their rooftop solar and believe it or not, despite our relatively small population we have collectively installed more household solar systems than almost any other country in the world.

For consumers, it’s a no brainer but the electricity companies seem to be making things more difficult as time goes by. Is this justified and are their technical issues we need to understand as solar owners, or are they just profiteering?

The grid is a complex beast and the electricity industry is even more complicated, so the answer is ‘a bit of both’. In fairness to the utilities, and because I’ve had a heap of emails from frustrated NSW folks, I thought I would highlight the New South Wales Service Rules as one example of how technical issues need to be considered.

The basics of grid energy flow, voltage drops and voltage rises.

 

The poles and wires around your neighbourhood were designed to transport energy from huge generators (typically hundreds of kilometres away) to your home. The further the energy travels the more losses . To compensate, the voltage starts high and by the time it gets to your house it will be lower, theoretically at 230V AC.

However, there’s a lot of stuff going on that can change the losses (and as a result, the voltage). Big factories switching on or off, high or low temperatures or the worst case, a heat wave where millions of Australians simultaneously flick on their air conditioners at 4pm when they get home on a searing hot day.

Generally speaking massive loads cause the voltage to “droop”. Network operators can tweak things to some degree and have to keep the voltage within certain limits.  But as a rule we live with and barely notice the ups and downs of our supply voltage. It’s the network operators job to control and manage these issues.

When we connect to the network, there is a cable from the power pole on the street that runs to your house, which is called your ‘point of supply’ and obviously there can also be losses between the pole and the point of supply too, depending on cable size and demand.

From the point of supply, there is yet more cable, the ‘consumer mains’ to your switchboard and of course, more potential losses. From the main switchboard into your household power points and lights the are more potential losses, although as a general rule these are lower because the loads are spread across different circuits.

Chatting with some New South Wales installers, they highlighted that historically the cable between the power pole and the point of supply was pretty thin, especially in rural areas or in older houses. Over time the rules around losses have got tougher so cable sizes have got thicker.  The thicker the cable the lower the resistance of the cable and the lower the voltage drop.  If you find that counter intuitive then think of the electric current like water flowing through a  pipe. The thicker the pipe the easier the water flows.

Enter, the solar dragon.

 

Now as you might have already realised, adding a solar system to the network actually has the reverse effect to a load. Instead of the voltage dropping under load, networks with lots of solar systems can experience voltage rise.

“That’s surely a good thing !?” I hear you say. In essence that’s true because more solar equals less demand, which equals less losses. However, to a network operator solar’s impact can be a variable; much more on sunny days, much less on cloudy days and on sunny days with passing clouds, the voltage can rise and fall dramatically in areas with lots of solar. If the network voltage gets too high or too low, solar inverters can switch on and off regularly which is not what you want.

So in fairness, it adds a whole new complexity and its one they have virtually no control over.

Much of the focus of the rules in NSW is around older and rural properties described above. In these properties the network operator typically increases the network voltage by adjusting transformer settings so that (for example) the voltage might start at 253V. Under load and with losses from the old skinny cables, by the time it gets to the house it will be down to perhaps 240V and by the time it gets to the power points, it’s down to 235V.

Now, if there is minimal load (like when you are out during the day) the voltage at your power point won’t be subject to as many losses and could actually be much closer to 253V. If we then add some solar, it will logically push the voltage even higher and could exceed 260V or more. This is bad for your appliances, bad for the network and bad for your inverter; in many cases if voltages are in this range the inverter will simply switch off. That’s bad too!

As a result of these issues New South Wales revised its NSW Service Rules to include specific rules about acceptable voltage rise for solar installations. If you connect a solar system in NSW your installer MUST do a voltage rise calculation in accordance with these rules and prove that they have worked out what will happen to voltage under various scenarios.

The diagram below shows what the voltage rise requirements are:

diagram of solar system on home

In NSW the voltage drops in these cables must be less than 1%

Now we do know that some parts of the Australian network can cope with better than others. Alice Springs and Southern Queensland have had case studies done on this very issue and a great summary report by the APVI is here for the data geeks. Generalising a little, their networks are more modern and or beefier; so the variations can be absorbed more easily without as much voltage rise. Another recent study done as part of a CSIRO pilot study into Smart Grids highlighted the variables around Port Stephens, which you can see in this map. In this one small area you can see some parts of the network are suffering low voltage from large loads and yet only a few kilometres away the voltage is quite high, most likely due to high concentration of solar systems.

solar connection srtength

The strength of the grid around Port Stephens, NSW. Blue is weak, red is strong.

What does it mean if you want to buy solar?

 

The New South Wales examples have several implications for potential solar owners.

Firstly, in NSW your installer must do the calculations to allow you to be connected, so make sure you confirm that they will before agreeing to buy off them.

If you have a voltage rise issue there are several potential solutions. The network company may be able to adjust the transformer voltage down depending on a variety of issues. If they can’t, then you may be required to increase part or all of your cabling so that losses are reduced; a cost but not such a bad thing in terms of efficiency, as many of your appliances will run more efficiently with a more stable voltage closer to the ideal 240V.

A good installer will be right across these options.

If none of the solutions above are practical then another solution is to limit the size of your solar system to one that does not increase the voltage by more than 1%. Alternatively you can keep your big-ass solar system, but use a special inverter that limits the amount of solar energy exported to the grid.

If you go for the ‘limited export’ option, then to avoid wasting precious solar energy, it can also make sense to install a device that dumps as much excess power as possible into your hot water system (think of it as thermal storage). The best option I’ve seen in Australia is the Immersun from ENA Solar which is approx $500 + installation.

A properly sized, well designed  solar system with a hot water controller and an export limiter is a very elegant solution that will allow you to get a solar system big enough to keep your bills down, even if your local grid is a bit puny.

Technical bit for geeks:

 

If you are curious about why reducing system size (or export limiting) is a solution to the voltage drop rules, then have a look at this equation:

Voltage drop = Length x Current x 0.017
                                                  Area

Volts= Voltage drop.
Length= Total Length of cable in metres
Current= Current (amps) through cable.
Area= Cross sectional area of cable copper

If changing the cable length or area is not possible, then the only thing left to change is the maximum current going through the cable. The smaller your solar system (or export limiter), the smaller the max current through the wires. The smaller the current, the lower the voltage drop.

 

Thanks to Nigel Morris From Solar Business Services for help with this post. 

 

About Finn Peacock

I'm a Chartered Electrical Engineer, Solar and Energy Efficiency nut, dad, and founder of SolarQuotes.com.au. My last "real job" was working for the CSIRO in their renewable energy division.

Comments

  1. hi again Finn,

    Just a few points of interest for the remoter W.A. Area that we have now been forced to do;-
    # anyone who intends to install solar, has a 15,000 management charge a year to pay before being connected to thy grid system !
    # As with, that any Upgrade to the incoming mains cabling is now made to be done via: Underground connection only !
    F.note:- If your across the road from the street ring mains aerial line, it’s about a extra $30,000 dollars to pay for the under boring of the roadway !

    # These are just some of the power authorities regulations to put a complete halt to the extra connections being done,now…

    So, I think you would agree,

    ” It’s finally been priced well out of the range & practically overpriced just to stop people doing it today ! ” just wondering if this has ever came to your attention elsewhere in AUSTRALIA as of yet ?

    • They’ve had similar rules for just standard connections here in Vic. for years. (Though not in all areas.) In remote areas a ‘deposit’ (to show good faith!) was required, sometimes greater than the quoted price for the whole job..and sometimes months in advance of completion.
      In Qld. years ago they’d bring you the power to just about anywhere for next to nothing. BUT you had to sign a contract to buy a certain (large) amount of power year after year, no matter how much you used ~ or didn’t. Needless to say the prices rose year after year too, and you had no right to disconnect.
      I always reckoned it’s where drug-dealers picked up their business principles and practices!
      And it’s all going to get worse.

      Any which way you look at it: the warning signs are obvious and blatant, and if you’re not willing to produce your own power you need your head read.
      …and, incidentally, think about putting your panels somewhere other than on the roof where they’re easily spotted. Chance are sunlight will be taxed down the track a bit.

  2. Girish Vinod says

    I think a very simple economical and elegant solution is possible. Connect a suitable capacitor onload side i.e. home side.This will reflect as a load but consume no power.

  3. Richard Gault says

    Why waste the power with a Capacitor. Just go off-grid, and especially if your connecting at a low rate input Tariff. as the electricity prices will continue to increase (the current goverments support for fossil fuel generation will guarantee this) solar will become increasingly cheaper and easier to justify if its not already there.

    • When the weather turns to shit, charge the batteries mechanically. A car alternator will churn out 90+ amps happily enough when bolted to a plank with a drive-belt connected to a pully (work out the best pully-size for your own application) running off a 5-8 hp stationary motor. ( I used to love playing around with old ‘hit-and-miss’ single-cylinder engines with massive flywheels; they’d run on ANYthing including light oils like kero, or even home-produced wood-gas.)
      I recently bought en el-cheapo remote-start generator (from Bunnings, on special for $345) which will crank out 60-odd amps, with which I intend to run the heavy short-term users (microwave, tools, etc.) and, if necessary, charge my battery-bank.
      The point is: there are ALWAYS lotsa alternatives available if one is no longer dependent on the good-will or competence of other sources.
      And at today’s prices there’s no excuse not to DIY.

  4. go off grid, use batteries for your surplus power, use micro inverters,have an simulator for the grid,,,, use a changeover switch on the main board for when it rains for 3 weeks and your batteries are down to 50%. why would would you sell power at 8 cent kw/h and buy it back for 4 times that much?
    I think it is called a hybrid system,,,, don’t export to the grid, use all your power yourself.

  5. George skinner says

    What are the pros and cons of having the panels mounted to a frame at ground level

    • Hi George,

      Pros:

      Ground mounts are not limited to the size of your roof. There is no climbing for panel installation and maintenance. There is increased airflow around the array, so the panels should operate at lower temperatures giving more power.

      Also choose the perfect tilt angle and panel direction.

      Ground mounted panels can be more easily cleaned.

      Cons:

      Ground mount racking is usually more expensive than using your roof.
      You need spare land.
      You need to dig a trench for the wiring to the switchboard.

      Hope That Helps,

      Finn

  6. Yet another good reason for going stand-alone. Whenever the status-quo inclines to more than a small advantage to the consumer the bastards change the rules.
    But do consider mounting your stand-alone panels near the ground in the backyard if possible. Not only are non-roof mounted panels less liable to serious storm-damage (and can be protected at short notice) they’ll be less noticeable ( or even simply camouflaged!) when the bastards get around to taxing sunlight in line with para 1 above.

  7. Hi Finn, taking the step to solar power and have just been quoted for 4.5KW system. Could u advise if “Phono solar panels Poly” and “4.2kw ABB Aurora” inverter are decent products
    thanks
    Jane

Speak Your Mind

*

GET THE SOLARQUOTES WEEKLY NEWSLETTER
%d bloggers like this: