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Insulation Resistance

January 11, 2021

What is it?

 The DC cabling, connectors and solar panels of most Solar PV systems are designed to be isolated from earth. 
Where a ‘path to earth’ is created it gives rise to insulation resistance faults and the inverter will shutdown.

What causes it?

In short, it is mainly caused by damaged and poorly installed DC connectors and cabling, and/or faulty solar panels.
A few common examples include –
  • Poor workmanship –
    • DC connectors incorrectly fitted
    • DC cabling and plugs left laying on the roof
  • Rodents eating the DC cable –
    • Rats
    • Pigeons
  • Sharp edge of containment/cable management cutting into the DC cable
  • Low quality or damaged solar panels
  • Although rare, a fault with the inverter system
With regards to the plugs, it is important to note that whilst they are designed for use outside, they are not designed to sit freely on the roof where they may end up submerged in water as the plug creates a ‘dam’ when water runs down the roof.

How do I know if I have it?

There are three ways of spotting that you have insulation resistance issues-
  • The inverters not working – possibly early in the morning
  • Unexpectedly low performance – particularly in winter and wet weather

What is the impact of it to me?

It means that your system is not working to its full potential which means you are losing generation and revenue.
It also represents a serious safety issue.

Is it safe to ignore?

No – insulation faults should not be ignored.
Failure to address the issue greatly increases the risk of fire and electric shock; corroded connectors heat up and have the potential to burn out.

Will it get worse?

Yes, insulation resistance does not go away and will only get worse.

How do I fix it?

It depends entirely on what is causing the issue.
If an inspection shows the cause to be rodents chewing through the cable, the cable has been cut because of poor cable management or the issue stems from the solar panels, then it may be possible to concentrate the remedial work to the affected area only.
If, however, the issues are occurring because of the way in which the panels have been connected together, whilst it is possible to try and track down the offending connection, ultimately – to ensure the issue does not happen again – you may need to consider the complete removal and reinstallation of the system. Obviously this is the last resort but it may be the only way to completely eradicate the issue.
If you are concerned that your system may be suffering from insulation resistance, or you would like to discuss adding your system to our asset management portfolio, please give BeBa a call today.