Overvoltage is impacting your Solar Systems

Article by: Zali Ashman

Recently UNSW released a study exposing the grid voltage rate in Australia which is affecting homes with solar systems and the results they found weren’t good. 

You might be wondering what voltage is, simply put, it’s the force that moves electrical current through power lines to homes. So all that AC your inverter generates requires voltage in order for it to move around your home and also for it to move to the grid. The tricky thing is that voltage is never a constant variable and depending on the demand for power will depend on the voltage reading. A healthy voltage rating is between 216.2 to 235 volts, this allows for a +10% rise and a -6% decrease. The voltage on the grid is meant to be around about  230volts at all times. If the voltage is too low, the power supply in your house will be poor and may also cut out and if it’s too high, power will be wasted and power bills may increase. 

Overvoltage is one of the most common issues that impact your panels’ performance, it happens when the grid voltage exceeds 258 volts and it when more solar is generated than power being used.

When the voltage gets to 253 volts it becomes too high for solar AC to reach the grid, this may result in lost feed-in tariff for your home. If your inverter is at 256volts during the day, then it will be limited to 68% of its total capacity. 

  • If grid voltage is already too high your inverter is no longer able to overcome it and instead shuts itself off. For example, if your solars are producing lots of power constantly for 10 minutes, then the grid will go over 255volts, causing an overvoltage reaction. 
  • Newer inverters ramp down power going to the grid before they reach the 258 volt limit.
  • Ways to fix this is by changing your inverter settings to a lower voltage setting in order for your system to not experience overvoltage shuts off. 

There’s a lot of talk in the media and with power providers that solar destabilises the grid as your inverter increases voltage by 2 volts when it’s producing power. Now, this wouldn’t be an issue if the grid voltage was at a lower reading as it would be able to handle 2 volts extra. With more solar systems installed will increase the voltage on the Grid in order to support the power flow.

UNSW study findings 

Over 12,000 homes were monitored during the UNSW study and 29.5% of tests conducted happened in South Australia. 

  • Out of the 12,000 homes, tests showed that 53% of those tested experienced power overvoltage. 
  • Each time the solars go over into overvoltage they disconnect for 2 seconds and once they reach over the 258volts they disconnect for 15 seconds. Each time your inverter disconnects, it shuts down and doesn’t generate any power nor will it move any power to your home or to the grid. 
  • Those that experienced the most overvoltage cut-outs lost up to $225-900 of revenue p.a. 
  • Those that were only mildly impacted lost between $3-12 p.a. 

UNSW researchers believe that the only way for this issue to truly be resolved is if the voltage on the grid gets increased. 

Ways to improve overvoltage cutouts: 

  • Installing a 3 phase inverter is the best way as the current being sent into the grid is divided into three different cables opposed to just one with a single-phase inverter. The lower you can make the current the lower the voltage will be. 
  • Upgrades to the grid, replacing powerlines with fatter ones as thicker cables contribute less to voltage rise. 
  • Increasing the voltage allowance on the grid to handle the higher voltage that solar is creating. 

Your local distribution network service provider (DNSP) ours is SA Power Networks,  legally have to fix the voltage if it’s higher than the standard range (mentioned above). You can make a claim to them and they will set up a voltage monitoring system in your area. It will take roughly around 3 months to complete the monitoring process and if the verdict comes back that the voltage is in fact too high then SA Power Networks will fix the issue. However, it may take up to 12 weeks to do so. 

*all graph data shown comes from the UNSW study results and not from SA Regional Solar. 

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