PV installations — cable and connector voltage ratings

Installers and designers of PV installations need to ensure cables and cable connectors being used in the PV installation will be operating within voltage ratings specified by the manufacturer, reminds the Queensland Electrical Safety Office (ESO). This is so the cables and connectors will not be electrically stressed and break down through exposure to voltages higher than they are designed for.

PV cables and connectors must have the following ratings to operate safely under normal conditions, and to withstand the full array voltage across the cables and connectors in the event of an earth fault — a DC conductor to earth voltage rating that is greater than the maximum open circuit array voltage; a DC conductor to conductor voltage rating between positive and negative cables that is greater than the maximum open circuit array voltage, said ESO in a statement.

Designers and installers need to be aware of the DC ratings of a cable, and that they can be different to the AC ratings for the cable, the statement said.

Cable voltage ratings are specified in the format of Uo/U where Uo is the voltage rating conductor to earth and U is the voltage rating conductor to conductor. The Uo/U rating should also indicate if it relates to AC or DC. Some examples of cable manufacturers’ methods to specify rating include:

• 0.6/1 kVAC,  900/1.5 kVDC
  • this indicates a 600 V conductor to earth AC voltage rating and a 1000 V conductor to conductor AC voltage rating; and a 900 V conductor to earth DC voltage rating and a 1500 V conductor to conductor DC voltage rating.
•  AC 600/1000 V,  DC 900/1800 V
  • this indicates a 600 V conductor to earth AC voltage rating and a 1000 V conductor to conductor AC voltage rating; and a 900 V conductor to earth DC voltage rating and a 1800 V conductor to conductor DC voltage rating.

PV domestic installations installed in accordance with AS/NZS 5033 Installation and safety requirements for photovoltaic (PV) arrays cannot exceed 600 VDC maximum open circuit array voltage, the statement said. This means for a domestic installation this is the maximum DC voltage a conductor in this situation will be exposed to. AS/NZS 5033 quotes several cable standards that satisfy this voltage requirement, including TUV PV1-F, UL 4703 or VDE-AR-E 2283-4.

Large-scale solar farms and some commercial installations may have a maximum open circuit array voltage rating that is higher than the voltages of domestic installations and may exceed the 900 VDC conductor to earth rating typically quoted by cable manufacturers (ie, cables tested to TUV PV1-F, UL 4703 or VDE-AR-E 2283-4 may not be adequate).

Image credit: ©iStockphoto.com/Anne Bæk Pederson