3 phase solar inverter and grid voltage

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c_picard

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USA
Greetings,

Would it be "normal" to see the grid voltage drop to approx 206VAC-215VAC when a three phase 50kw
inverter is connected to the grid? Before connecting the inverter voltage is around 277V to ground for each phase.

Does this have something to do with the utility transformers' impedance? I've never seen such a drastic drop in voltage. What causes this? Please forgive my ignorance!

Thanks,
Charles
 
Help requires more information:
1. What are the specifications of the electric service you are connecting to?
2. More information on the inverter and its other specifications.
3. What kind (Make, model) of meter was used?
4. Or, just how much smoke, noises and flash were produced?:mad:

Seriously, maybe you are connecting a WYE to a DELTA one way or the other.
 
OK, here's the details I know..

277/480 wye(no high leg)
400A service fed with 500MCM aluminum

I was using an admittedly cheap klein multimeter.
Voltage to ground on each phase with the inverter offline was 277, phase to phase
around 480.
With inverter (powerone aurora 100kw)online, inverter output was approx 12kw,(pouring rain, and only 50kw of modules online) and my clamp on meter showing 18-20 amps each
phase. Voltage to ground dropped to 215Vac. Something is clearly not right, I just don't know where to start.
And unfortunately I took these readings from different locations, so there not instantaneous.

I'm working for a new company and there is no in house expertise to draw from.

Another detail, the line side tap was done with insulation peircing connectors, if these were not properly torqued
would this result in high resistance that would cause this?

I've also heard that things on the utility side can affect the voltage dropped under load. Over my head, I just don't know who to ask, my boss is a landscaper turned solar contractor.

The inverter instructions were translated from Italian, but it seemed fairly clear that no neutral was needed for the inverter. I'm concerned this may have something to do with it. The inverter has a pretty good sized xfmr in there, and I'm not used to not having a neutral.

No sparks or explosion, I'd almost rather have that, the problem would be easier to find. I get nervous when it's
a problem like this that would have gone undetected if someone else had commissioned the inverter.

Thanks for the reply,
 
c_picard said:
...

The inverter instructions were translated from Italian, but it seemed fairly clear that no neutral was needed for the inverter. I'm concerned this may have something to do with it. The inverter has a pretty good sized xfmr in there, and I'm not used to not having a neutral.

...
Click to expand...
This would make me mighty suspicious of inverter and its true output voltage...

I would assume an Italian manufacturer of electrical equipment meant for use on US soil would have the instructions written in American english. Even the Chinese manage at least some broken english...
 
Your inverter is like a bicycle attached to a semi truck from the grid's perspective. I don't know how it can even affect the grid voltage by any significant amount.
 
I suggest checking the neutral-ground bond for the service. The neutral of the WYE service may be floating and/or affected by single phase loads on the service.

The photovoltaic inverters will not operate outside of their set voltage range. The inverters are designed to shut down on loss of a phase. Have you measured the phase-to-phase voltages at the same time as the phase to neutral?

I found that power-one.com has English language manuals on-line (the English is poor and confusing at times, some of the controller graphics are in Italian). I also noted that the basic European version of the inverters have an ungrounded DC side and do not have an internal isolation transformer. You need to check the full part number of your inverter to see if it includes a transformer, double check the installation.
 
Whoa!

Whoa!

If anything, the voltage will rise when the inverter is generating. If your voltage drops from 277Vln to 210Vln there has to be a lot of current or a lot of resistance. Something is going to burn or blow.
 
utilities have a plus/minus 10% bandwidth on the voltage delivered to customers. a 480V service can measure from 432V (minus 10%) to 528V (plus 10%)
 
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