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Lousy power quality? Blame the grid, not rooftop PV

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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.

AAP Image/Dan Himbrechts

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:

“Historically, the survival of a local electric company did not depend on its efficiency. In fact, a ‘sloppy’ operation could do just fine financially.

“That’s because utilities were usually the sole supplier of a needed product and were allowed to price at a level that gave them a prescribed return upon the capital they employed… That’s all changing.”

  

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  • bruce mountain

    interesting.

    • thought i had put link in: http://www.mdpi.com/2071-1050/10/4/1224

      • bruce mountain

        yes, tried to delete my comment moments after posting, but it said I could not have it blank so I replied “interesting” . Am reading paper now. This is excellent stuff, thanks for drawing attention to it.

      • John Smith

        The link for the ARENA study/report you mentioned doesn’t work. I believe this is the one you’re talking about, right? :
        https://arena.gov.au/assets/2017/02/VPP-SA-Public-Milestone-1-Report-Final-for-issue.pdf

      • rob

        @disqus_an6c03erWr:disqus completely off topic but have you any idea when Tassie will be back on the NEM………The latest I heard was mid April…….but still no sign of it happening this month? cheers rob

        • late May i believe. good news is that they have found the cable. now they just have to find the fault.

          • rob

            Thanks giles

  • Mark Byrne

    Thanks Giles. This will be very useful evidence when the AEMC turns its attention next month (see https://www.aemc.gov.au/markets-reviews-advice/electricity-network-economic-regulatory-framew-1) to PV connection costs and the prospect of charging for exports to the grid. In the Distribution Market Model last year they highlighted a litany of engineering issues supposedly caused by high PV penetrations, with no evidence base, and noted none of the benefits.

  • Gavin Dietz

    Thanks Giles, have a look at this graph from my house in Sydney from last April (2017) where the voltage in 1 of the phases went as low as 180 volts shutting down our appliances randomly. The cost to consumers of this is extremely high as indicated in your article. https://uploads.disquscdn.com/images/a0d29a11abbbecd50a06fcc1075ec5dbd21ffa2c3b77a508f2afc8f2876e05e8.png

    • Liam

      That looks like a fault condition, or a very heavy, and unbalanced, reactive (inductive) loading. I’m surprised a fuse did not open on the transformer.

  • The link to the ARENA study is incorrect?

    Here in the west, my home voltage is always just a tad under the upper limit of AS60038. According to my solar inverter yesterday, the minimum for the day was 244VAC, and the max was 251VAC. Typical my guess.

  • Robert Westinghouse

    Not surprising – Big Business trying to undermine the people taking control of their own lives. We had to apply to Essential to turn down the power…. Just their way of pushing us back to an overpriced grid…The government and it mates hate being wrong. I urge more grid defection and let the power companies DIE.

    • wideEyedPupil

      Is that a bit like someone wishing the death of their parents because they were mean to them, lacking in compassion and a sense of community.

  • Chris Fraser

    A report in SMH earlier this week described how AEMO chief Audrey Zibelman raised concern that prosumers were defecting, and I understood this concern stemmed from both consequences of the death spiral and also the value that the grid would be missing from having prosumers still connected. Audrey is entitled to have the most expert opinion on the flow of energy through the grid.Imagine how the grid regime has changed in 100 years. The grid used to be called a utility, that is, it served the public’s purposes, not its own. Now of course, the grid relies on favourable legislation (the Regulated Asset Base ie gold plating and fixed returns on investment) and everyone being connected for its own survival. From the prosumer perspective the grid mostly just sits there like a vampire, a parasite.Because of short sighted self serving politicians, we now have lots of work to do to have ‘still connected’ prosumers recognised for the value they provide everyone else.

    • wideEyedPupil

      One of Zibelman’s main interests is in having consumers of all sizes available for the DSM she/AEMO plans to integrate to the current system, which should reduce wholesale pricing and encourage more renewables to the grid. DSM was a big part of her role at previous employer, grid operator in NYC.

  • Tripp Tucker

    “SDG&E contends that the amount of reduced real power output should be de minimis. PG&E states that system voltage is normally within 99% of American National Standards Institute (ANSI) C 84.1 requirements (0.95% to 1.05% nominal voltage) and therefore, the probability that inverters would be impacted by curtailment is extremely small.” Rule 21 Resolution on Real power priority vs. Reactive power priority IEEE 1547-2018.
    docs.cpuc.ca.gov/PublishedDocs/Published/G000/M212/K527/212527968.PDF

  • Les Johnston

    Analytical data is critical information. With no data, myths remain supreme. It is not surprising that voltage and frequency control using old technology has much wider variances than that provided by sophisticated electronics.

  • solarguy

    On what Warren Buffett said at the end here. I, have to work and innovate for my money, so do the utilities. They had better change quickly or they will perish. Stupidity and greed isn’t a business model anymore!

    • MaxG

      I am sorry to say: It works perfectly well — as you can evidently see. 🙂

      • solarguy

        Yes I know it’s working for them now, but that wasn’t actually my point Max. If the don’t work with us in the new paradigm, they won’t have a business eventually and that stuffs everything up.

  • MaxG

    Poor grid supply has been around since day 1 I migrated to AU in 1995!
    Below is a graph of yesterday’s Voltage, which is measured at the inverter/charger, and still has to travel for 50m to the supply point via 32mm2 cables… meaning the numbers would be higher up there.
    https://uploads.disquscdn.com/images/d949c272ceabb7b4a0423f23a9e1843b175deb998b15a1edb3336cc32cf722c3.jpg

  • nakedChimp

    Problem can be solved by a UPS like system for your whole house/flat/etc.
    Grid comes in, is converted electronically to 400Vdc and run by a battery system. Your power then is taken off that battery system, which will create a unaligned 230Vac local grid from the 400Vdc, which will always be in spec and not destroy any appliances.
    Cost wise this should be possible (5kW permanent, 10kW short time) for about $500 at mass scale (+cost of batteries).
    And with the battery there will be no brown/blackout problems (for the range of the battery).

    • mick

      curious, does this depend on battery technology-(jagged) voltage goes through a battery that acts like a sponge smoothing it out thus saving the toaster from a premature death?

      • nakedChimp

        No, not really. It’s rather capacitors, coils and power semiconductors, that are controlling the ‘flows’ and your toaster not ‘seeing’ the grid anymore.
        The 230Vac is being provided by your own local inverter, who runs of 400Vdc, which itself is being supplied by solar, battery, grid, etc..

        So this UPS takes 230Vac from the grid or 500Vdc from the solar array and does convert it to 400Vdc. The battery then charges from or supplies to that very same 400Vdc bus.
        And your switchboard is being fed 230Vac from an inverter that is being supplied by that 400Vdc bus.
        The controller makes sure the 400Vdc bus is always capable of delivering for your inverter and manages the sources and sinks, depending on circumstances.

        Hybrid inverters are designed like that on the inside, it’s just not mainstream yet = prices are still high.

        • mick

          got it, made my analogy look bloody simplistic,cheers 🙂

  • George Michaelson

    Wouldn’t some form of functional use of the excess electrical power always have made sense? For
    instance, I lived in Coorparoo with a pumped water supply tower up the road on a hilltop. They could have co-funded a 120% capacity, run it at 80% and use the 40% as demand soak to pump water up.

    Obviously now, you’d deploy batteries. Speaking of which, every Telstra exchange used to have a huge battery stack. If they’d been spec’d oversize, it’s another energy store which the state (gpo) owned and could have used for demand management.

    Gold plating referred to capital investment at guaranteed rate of return. I don’t think functional investment should be viewed as gold plating. A network which can’t hold regulated voltage feels like one which is undercapitalized not gold plated.

  • Yes the grid is often at fault with over voltage issues. But not all installers test the voltage rise when they install. So if you have an issue heres how to work out if it is your solar installation or the grid’s fault:

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

    • Rod

      Finn, did you do a write up on your SolarIQ voltage optimiser trial?
      It sounds like a good product but I’m guessing a bit pricey.

  • Liam

    I’m surprised, at least in states with smart meters, we have an army of measurement points for supply voltage. It should not (in theory) be hard to feed that data back into a substation, region, or even state-wide supply voltage management platform. I guess if there’s no (profit) reason for the distributor to address the issue, they won’t bother with it.

    Inverters can also provide reactive power support through the volt-Var response specified in AS4777.2 which would reduce voltage variation on long distribution lines.

    • Aerial Fencer

      Non of which will fix the problem. There are plenty of distribution transformers that have high voltages right next to them and low volts at the end of LV feeder. Changing the tap settings at the Zone substation or bulk supply substation is not going to help. The smart meters would certainly help indentfy problem areas but the solution is installing extra transformers on the street and regulators along the high voltage feeders.

  • Brunel

    Should have stuck with 240 volts and required every appliance imported to operate at that voltage.

    Will an inverter save my appliances from getting fried?

    • nakedChimp

      A good one yes.. but I’d rather look out for a UPS style of device (which isn’t available off the shelf).
      And more importantly, the power ratings you want won’t be cheap (yet) – you’re looking at 3 grand upwards easily without any work done.
      The need you NOW have is still relatively unique, thus not available off-the shelf for low-price.
      See my earlier post about it.

      The only customers with similar needs right now are big RVs or boats (when they are connected to the grid) or datacenters (big UPS).
      That’s the fields you’d have to look at for sourcing this, if you need it now, probably highest chance with the datacenter UPS suppliers (APC, EATON, ..).

      Off grid homes don’t have 230Vac inputs from the grid really, so they are not designed like that, which means your local solar installer – if he does off-grid – won’t be able to help you really.
      And islanding hybrid inverters don’t give the protection you want, as they are just hooking into the grid normally (as any other solar grid inverter does) and will provide an island otherwise.

  • Daniel Huppert

    Hi,

    Total Solar Solutions in Bayswater Vic genuinely provides back to base monitoring, as we want to ensure our customers continue to benefit from reliable solar generation. One of the parameters we are able to remotely monitor through the inverters and modbus meters is grid voltage.

    At least 1 in 5 of our solar installations experience some occasional issues with high grid voltages, with perhaps 1 in 10 having regular issues with their inverters de-rating most days when grid voltages rise above 253v to 255v, and even shutting down altogether when grid voltages rise above 257v.

    We monitor and log the high voltage issues, and work with our customers to lodge complaints with their power distributors. Some distributors are reasonably quick to get grid voltage issues rectified, but some, like AUSNET being the absolute worse distributor, just horrible to deal with, don’t seem to give a stuff when our customers send in multiple complaints and reports to them, even with plenty of data logged to prove high grid voltage.

    I know that government regulators have required inverter manufacturers to build in various parameters into their inverters, such that they start de-rating (reducing power output) when grid voltages get high, and shutting down altogether when it creeps higher still, when the inverters themselves can easily handle high grid voltage, but it’s the software that limits them.

    In recent years, those parameters have been set even lower, so I say, so long as the regulators require inverters to de-rate and shut down when grid voltages rise, then they can bloody well get on the backs of the distributors and demand they do a better job of managing the grid.

    Daniel
    Sales manager
    Total Solar Solutions Australia

    • I Porter

      Well said Daniel. Unfortunately individual consumers have no leverage against the big network operators. We need to see organisations taking class actions out to challenge these slack operators.

  • Aerial Fencer

    Typically voltage issues are caused by large LV areas (ie the length of conductor attached to the transformer) and high variability in consumption. The easy fix is lots more distribution transformers ( especially if they have auto tap changers). Only problemm that’s really expensive

    • Pat

      Hi Aerial,

      Interesting – I sometimes hear networks say that they’ll just use taps to fix the voltage problem. Why can’t networks simply tap the existing transformers using more accurate data monitoring? What are the issues/costs of taps?

      • Aerial Fencer

        G’day Pat,
        A distribution transformer (eg 11kV to 230/400v) will have a number of tap settings which can increase or decrease the voltage. When the transformer is commissioned the worker will test the voltage at the transfomer and change the tap up or down to get a voltage slightly higher than standard. This because once load is applied there will be voltage drop in the transformer itself and along the distribution mains. The more demand the higher the voltage drop. The longer the LV mains the higher the voltage drop. It is entirely possible for the voltage at the transformer to be high (245 v) and the voltage at end of the LV feeder to be low (210 v). To change the transformer tap you have to turn off the transformer.
        If a transformer has stable loads and the smart meters tell the retailer who tells the distrbution network owner what the voltages near the transformer and at the end of the feeder are, than they can send a crew out, turn off the transformer, change the taps to the sweet spot, and turn it back on. If you have wildly different peaks and lows in demand and a really long LV feeder that won’t help.