DC on neutral

tombennetts · Jun 15, 2015

Hi All

Just completing a megawatt PV installation, on testing we appear to be getting DC current on our neutral cables - anyone else come across this?

Also while performing our Zs we cannot seem to get results. tried using a Megger and a Robin, both are saying the volatge is too high between phases and CPC, however when I actually measure the voltage its 230-235. Any ideas?

Leesparkykent · Jun 15, 2015

tombennetts said:
Hi All

Just completing a megawatt PV installation, on testing we appear to be getting DC current on our neutral cables - anyone else come across this?

Also while performing our Zs we cannot seem to get results. tried using a Megger and a Robin, both are saying the volatge is too high between phases and CPC, however when I actually measure the voltage its 230-235. Any ideas?

How close is the AC and DC?

tombennetts · Jun 15, 2015

Not very at all, all AC cabling is buried SWA that comes out of the ground under inverters straight into isolators, straight into the inverters. The DC cables run under the panels into the top of the DC isolators (1 metre from A.C isolators) then into the inverter. Replicated 48 times

Gavin A · Jun 15, 2015

has anyone been bonding the dc side to neutral?

what voltage dc, what level of current, what's it referenced to? Ground mount or building mounted?

tombennetts · Jun 15, 2015

dc has not been bonded to neutral. It's a ground mount. Using a voltmeter between phase and earth. We have got fantastic earth readings at the main panel, <0.01. Very low levels of current but im pretty sure its what is buggering up my tester when trying to Zs.