testing pv arrays

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g.bird

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hi guys i have solar pv on my roof,with a dc insulation fault, i suspect its due to water ingress.there are two strings,thats 2 pairs of wires going up to the pannels.iv  tested each pair with a multitester, having firstly disconected from the isolators and are geting the following .L=N  282V,L=E 204   ANDN=E 68V...THERE IS NO EARTH CONECTION TO THE PV ARRAY.for testing purposes iv used the earth connection of the main supply feeding the inverter/dc isolator,,,anybody got any ideas/help...on these findings..the system has shut down ,and will not resstart because of this fault...what is the cure.cheers

 
You are measuring voltage not insulation,. and the terms L, N and E are irelevant to the DC output from a string of panels.

You want to do an insulation test instead.

Best do it at night when the panels are not generating, get it wrong and 282V DC will HURT or worse, kill you.

 
You want to do an insulation test instead.


IR test would confirm leakage, but given the voltage readinds and panel qty (not mentioned) you can easily work out which one has the fault. if it has 10 panels then its most likely panel 7 from the end with the highest reading to earth

 
there maybe no direct earh connection, but it will still register to earth through building structure. Seeing as you have 2 strings, disconnect 1 and see if fault clears, that eliminates 50% of array.

 
thankyou,,my system has 16 pannels,in 2 strings,,i was concearned about doing an insulation test using a 500v megger,because i understand the array on the roof has junction boxes with bypass diodes and was worried abt damageing them,or the pannels,,...question to binky,andy ,and prodave,cheers

 
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