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Lousy power quality? Blame the grid, not rooftop PV

Giles Parkinson / RenewEconomy / 27 April 2018

Australia’s electricity grid might be the biggest man-made machine in the world, but it doesn’t always perform to expectations.

Apart from the occasional blackout, caused by storms, bushfires, equipment failure or political bluster, many consumers suffer from sudden surges in voltage that can either dramatically “pop” an appliance, or significantly reduce its lifespan.

It is a significant but hidden issue that could be costing consumers billions of dollars in failed appliances, and is also affecting the performance of inverter-based technologies such as rooftop PV and battery storage systems.

In recent years, the overwhelming temptation among network owners and many in the media has been to blame the power quality problems on the arrival of rooftop solar PV – which now sits on some 1.8 million household and business rooftops.

But a major new study led by a team from Queensland’s University of Technology – analysing the power quality in homes in four different states over a year – suggests that the problem is not solar PV, but the way the grid is managed. And the way it has always been managed.

“Much of this literature gives the impression that networks, particularly low voltage networks, were effectively and proficiently managed and operated before the rise of PV, and that this new technology is causing problems that did not previously exist and would not currently exist if there were no rooftop PV systems,” says the study, led by Wendy Miller.

Wrong. The QUT study suggests that the low voltage distribution networks (that’s the local grids) analysed in this study “do not have networks that meet required power quality standards – and this cannot be attributed to the rooftop PV systems.”

It says that power quality failures in these low voltage networks could be attributed to poor historical management.

But it could also be a significant management culture issue – missed opportunities to embrace PV as a means of better network management, lack of acknowledgement of the emergence of the prosumer, and lack of total quality management and systems thinking.

The report’s findings highlight widespread concerns within the industry about the quality of Australia’s power networks – something of a bitter irony considering the “gold plating” that has occurred in the past decade.

The voltage issue could be seen as another form of gold plating. Some blame the fact that utilities are deciding to deliberately pass through high voltages to consumers – effectively “force feeding” them electricity – because for them it is the most efficient way of managing the system.

The alternative would be to “dump” excess electricity. But that means that both the generator and the network would miss out on revenue. So they pass the problem on to the consumer, and they suffer the consequences.

So, the voltage issue is not just affecting the way that the grid can be managed,  it is also “frying” appliances – some estimates suggest that the issue is costing households around $3,000 over a period of 5 years from the reduced lifespan of appliances.

And it is also affecting the performance of rooftop solar PV and battery storage. A little known ARENA study highlighted to RenewEconomy this week showed that the problems affecting AGL’s proposed virtual power plant in Adelaide were likely caused by high voltage levels.

The voltage standard should be 230V, with a tolerance or “preferred operating zone” of 226V to 244V.

The ARENA study found that more than one quarter of systems installed as part of the AGL VPP experienced grid voltages of greater than 256V, and just over a third had disconnected at least once due to high grid voltage.

More than half of the energy storage systems recorded voltages above 253V. (See page 21 of the report).

The QUT study looked at the power quality issues – voltage, frequency and power factor – in detail across the four states. It found that these occurred both at times when rooftop PV was in production, and at times (particularly in the dead of night), when it wasn’t.

“No direct correlation was found between these factors and the voltage variations measured, suggesting that power quality variations measured at these households are attributable to other (non-PV) causes,” it says.

It goes on to blame “historically poor knowledge of and management of” low voltage networks,  and missed opportunities for network improvement.

It suggests the network owners need to “re-conceptualise” their business culture and practices to embrace the changed nature of energy supply and demand in a world of prosumers and technological and business innovation.

It says this would “help correct false and misleading public perceptions” of the benefits and limitations of rooftop solar.

The lack of knowledge, and the lack of action, is disturbing, the report finds. A Queensland network found that 29 per cent of its urban feeders were outside the 230V standard, and while most of this could be addressed through a “transformer tap change,” that hadn’t been done.

That, in turn, was caused by “significant gaps in their data/knowledge about their own network,” particularly at a distribution transformer level and below.

“They do not know what supply voltages are experienced by the customers. They have a poor understanding of customer loads such as the ratio of constant power loads to resistive loads at peak demand,” the report says.

“The lack of attention to the low voltage network may also be a result of the way in which risk has been managed by the electricity generation and supply industry.

“With limited budgets and resources, risk management has focused on managing ‘high impact’ network events, such as loss of a centralised generator or collapse of a major transmission line.

“This was understandable as such events could impact on thousands or even millions of customers. In a centralised system voltage issues within a low voltage distribution network do not attract much attention from either the industry or the broader public.

“However, the increase in embedded generation at the low voltage level raises the question of whether there is a need to modify the risk management approach to be more in line with the changing network structure and conditions.”

It suggests a change in network business culture, particularly given the likely increased role of “prosumers” as they take up battery storage, electric vehicles, and peer-to-peer trading platforms in increasing numbers.

In short, the report adds to the growing evidence that issues with the grid are not caused by new technologies, but by the failure of asset owners, rule makers and operators to try and understand how to embrace them.

And because these new technologies are both fast, and accurate, as the market operator has recognised from the performance of the Tesla big battery, at Neon’s Hornsdale Power Reserve, the lax governance of the grid has been found out.

It is notable that the QUT report quotes the billionaire investor Warren Buffett, who made a similar point way back in 2015:

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