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Discuss Panel voltage differences on same MPP tracker. in the Solar PV Forum | Solar Panels Forum area at

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Hi all,

This may is a little odd and may take some getting your head around but here goes...

I measured around half the load current on two DC strings , even though the AC and DC mains were isolated.
There was a voltage difference between two strings . ( around 75vdc between String 6 and the other strings).
All the IR values of the strings are over 50 mohms
When Isolated (using DC isolator underneath) two strings still had around 3.5 amps on each.
When inverter switched on all strings run at the same load current . Voltage just down on the one string.

Is this a normal state, I believe we have 2x panels which may have been bypassed on an MPP tracker and this could be circulating current perhaps, is there anything within the manufacturer instructions that state all strings on the same MPP must be of the same voltage and could this damage the inverters MPP by bypassing panels, is there a maximum voltage difference we can go too?

Any info on the above state would be appreciated, this is the second time I have came across this issue now, the main issue would be disconnecting the DC plugs whilst the current is flowing and everything is off.

This is on a UK solar farm.

Many thanks.

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