Insulect Sheath Voltage Limiters

SVL’s provide valuable protection to expensive cable installations. They are highly reliable and effective at managing cable sheath voltage rises and the associated power flows that can result under fault conditions.

They are highly reliable and effective at managing cable sheath voltage rises and the associated power flows that can result under fault conditions. Our brand partner, Insulect, manufacture an extensive range of quality 20kA zinc oxide sheath voltage limiters (SVL’s) from voltages 1.5kV to 9.0kV

Generally the following must be considered:

• SVL Rated voltage must be equal to or greater than the induced sheath voltage caused by the maximum system fault current (i.e. The SVL should not conduct during normal fault conditions).
• From the cable manufacturer, obtain cable data to determine the maximum voltage withstand for an 8/20 and 4/10 microsecond lightning or switching induced voltage.
• From the SVL data characteristics table, check that the SVL selected has residual voltages less than the rating of the sheath (i.e. the SVL’s main function is to protect the sheath under these conditions). 65V is generally the maximum allowable voltage due to normal load currents. Short circuit and switching currents will cause much higher voltages (several kV).

These induced voltages must be calculated by the client’s engineers before an SVL can be selected.

Note that all bonding cables used for earthing the sheath must also be able to withstand these voltages.