Backfeed DC Voltage from Inverter to Meter ?

[sunnyirishday]

I have installed a Solis-2K-2G Inverter (approximately 2 kW) to my solar panels at my home. When I disconnect the inverter from the grid I measure approximately 100v DC separately on the neutral and phase at the meter point. My question is what is this voltage and where does it come from ? Thanks for your help.

[bcroe]

Not sure what you mean by "the meter point". If you want things to be inert, better use both an
AC and a DC disconnect to the grid tie inverter. A grid tie inverter with DC panel power active will
output some energy to test for a solid grid connection, to send AC power to. Details aren't published.
Bruce Roe

[sunnyirishday]

Thanks Bruce - to clarify, the meter point is where the utility company connect the meter to measure the output power going on the grid. If you had any further thoughts or material I could read on this, I would appreciate it. Thanks very much.

[bcroe]

The inverter mfrs aren't telling us how they test for grid integrity, but its some kind of super mega AC ohm meter.
Bruce Roe

[ButchDeal]

Thanks Bruce - to clarify, the meter point is where the utility company connect the meter to measure the output power going on the grid. If you had any further thoughts or material I could read on this, I would appreciate it. Thanks very much.

Ok now I am confused. Are you in an SREC market and have a production meter measuring your total production for SREC generation?

If so, that isn't a utility company meter, it is your meter.

If you are talking about hour home meter now NET meter that should be the exact same location you had a meter before.

If you are in one of the few locations with DUAL meters and a dedicated meter for generation, then your statements make since.


There shouldn't be any voltage (AC or DC) on the grid side of a grid tie inverter with the grid disconnected. In most net meter situations the meter is on the grid side of the AC disconnect though so you would be reading the grid voltage.

[bcroe]

Ok now I am confused. Are you in an SREC market and have a production meter measuring your total production for SREC generation?

If so, that isn't a utility company meter, it is your meter.

If you are talking about hour home meter now NET meter that should be the exact same location you had a meter before.

If you are in one of the few locations with DUAL meters and a dedicated meter for generation, then your statements make since.


There shouldn't be any voltage (AC or DC) on the grid side of a grid tie inverter with the grid disconnected. In most net meter situations the meter is on the grid side of the AC disconnect though so you would be reading the grid voltage.

If the grid tie inverter has DC power, its going to be looking for grid integrity. It doesn't know
you pulled the AC switch, it has a (undefined for us) process for checking, to avoid islandng.
Bruce Roe

[jflorey2]

I have installed a Solis-2K-2G Inverter (approximately 2 kW) to my solar panels at my home. When I disconnect the inverter from the grid I measure approximately 100v DC separately on the neutral and phase at the meter point.

Neutral never gets disconnected. If you are measuring ANY significiant voltage from neutral to ground you have a serious problem; pull the DC disconnect and leave it off until you can get it fixed.

If you are measuring from a phase output to neutral (and the inverter is disconnected, and you are on the disconnected side) then that's not necessarily a bad thing. You might see some strange voltage with a very high impedance, since with a transformerless inverter you have several semiconductor paths from PV+ to the power line, and you might be seeing leakage. If you put a 1K load on it it would likely go away.

If you are measuring from a phase output to neutral (and the inverter is disconnected, and you are on the CONNECTED side) then that's odd. Some (very cheap) multimeters will not accurately measure DC voltage in the presence of strong AC and it is extremely unlikely that your grid connection has a 100 volt bias. So probably measurement error.

[bcroe]

Where did he mention ground? I can't tell where he has the meter connected, my inverter doesn't
use neutral. Bruce Roe