[RE-wrenches] [EXTERNAL] Voltage Rise

[White, Will]

I’ve run into a similar issue, and the problem was on the utilities side. They had shut down the local substation for repairs and were pumping power in from the next town over. To push the power that far, they increased the line voltage, which was causing issues with the PV inverter.

I’d suggest asking the utility to check the voltage at the transformer. They should be able to reduce it if it’s too high.

Thanks,
Will

From: RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> On Behalf Of Dave Tedeyan via RE-wrenches
Sent: Thursday, February 23, 2023 12:02 PM
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Cc: Dave Tedeyan <dave at sungineersolar.com>
Subject: [EXTERNAL] [RE-wrenches] Voltage Rise


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Hi All,

I've got a customer who is having issues with high voltage at their house. This first became an issue after installing 23.1kw of AC solar output. They have some GREE heat pumps which have been having some failures. The heat pump people are saying that the problem is that the voltage is above 252V.

The grid voltage was measured at 246V with the solar off, and 260V with the solar cranking. The inverters are within 10' of the MSP where there is a line side connection. Then there is 4/0 AL cable which has to go roughly 175' before it reaches the transformer. At 246V and 92A, there should only be about a 3.6V rise, or maybe 4V including the wire from the inverters to the combiner to the MSP. Yet somehow there is about 14V of rise.

The service entrance cable is buried. It is in conduit where it goes into and out of the ground, but I have no idea whether there is conduit for most of the run underground. Maybe there is a nick in the cable underground which has caused corrosion? Does anyone have any ideas of how to find the cause of the increased resistance? I should go back out there with an IR camera to check the connections that I can at least get to in the house.

I have suggested that they install a buck/boost transformer on the heat pump circuits to bring down the voltage a little bit. But they are also concerned about the high voltage causing issues with other electrical appliances in the house. Does anyone have any anecdata to show whether there are other hidden issues if the house is at 260V during times of high solar production?

Thanks!
-Dave

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