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Solar PV DC earthing.

Jake Morgan

Hi all, I'm in the process of designing a solar install where the DC strings are going to have to be buried in the fabric of the building. I am planning to use PV ultra SWA cable or earthed steel conduit and make sure there are plans to record where it is, as per IET COP for Solar PV 5.10.3. 

It has got me thinking about what actually happens in a scenario where someone drills through it. With 230V AC systems the earthed containment would contact the Line and cause a short circuit that would hopefully trip an MCB/RCD. DC strings do not have a reference to earth nor is there any device to trip so what happens? Or is one of the poles earthed in the inverter?

Can anyone point me towards further reading on this?

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  • 0

    Aah its complex. not all inverter systems are equal, transformerless systems effectively connect one side of the DC bus or battery  to one side of the mains and then flip which side 50 times a second. Clearly a fault to earth in such a system blows something, but if that is the supply ADS or the semiconductor switches that do the commutation is a guess !

    Inverters with transformers have a floating DC side, although for EMC reasons one side often is earthed, or at least earthed to RF, if not connected directly.

    There are quite a few good explanations on maker's websites.
    Mike

  • 0 in reply to mapj1

    Thanks, that makes sense, I'll have a look at the websites. 

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