We noted this morning that ‘Curtailment of rooftop PV underway in South Australia’ using the ‘Distributed PV Contingency’ measures* previously prepared by AEMO.
* In another a later article we’ll endeavour to explain in more detail what this is all about … but for now you might find the article ‘Unlocking a Future with Distributed Solar’ by Mark Thompson and Jenny Riesz at AEMO on the ESIG website of useful background.
Despite these pre-prepared measures, there are questions being asked about whether there’s too much rooftop PV and not enough controllability to cater for situations like this:
(A) SA Power Networks via Facebook
For instance one WattClarity reader has pointed to this update from SA Power Networks this afternoon on Facebook (14:00 SA time, so 13:30 NEM time) in which they are asking residential users to manually switch off their rooftop PV to give them an extra helping hand:
… though I can’t find a similar note on LinkedIn or Twitter.
I can’t ever remember hearing a network company putting the call out for people to manually switch off their rooftop PV! That’s a bit of a sign that the situation is pretty serious.
(B) Voltages being raised?
In response to an earlier tweet from me, Mark Jessop has noted that:
‘SAPN appears to be increasing line voltages to cause PV inverters to trip out. Interesting decision, but I’m not sure what other options they would have (probably not enough systems which are remotely controllable yet).’
… here’s the reference:
Can confirm that the SA network voltage was raised for approx. 4 and 1/2 hours just after 12.30pm.
Our monitoring systems alarmed with a voltage increase of around 200v on each phase
Re supply authorities ramping up voltage to trip inverters and Jim’s comment of of a very large increase at his place. I’m wondering if that increase in voltage that Jim commented on was natural. Don’t forget that at the household end of the grid, each suburb has a final distribution transformer, stepping down (usually) 11KV reticulation to 240/415volts. If the energy of all the suburban panels at midday can’t be used up by a load, then a higher voltage will naturally occur. 240v rising to 270v is not out of the question (and this will trip inverters), but 200 extra volts seems very large and would fry many household appliances. Also I find it hard to understand how the SA power authority would easily be able to increase voltage. Most final suburban transformers can only increase voltage with a manual change-over of their output tappings. It’s also very dangerous to increase voltage on a grid scale as things will burn out. Lastly voltage levels are set by the AS 3000 Wiring Rules, and must be no greater than around 10% of normal.