Relay protection

High impedance relays

Metrosil varistors are designed to effectively limit the secondary voltage of a current transformer to a safe level during maximum internal fault conditions.


Protection built-in…

In some applications of high impedance relays for protection and control duties, the maximum internal fault current can develop high voltages that can damage the relay insulation. A range of Metrosil varistors, primarily based on 150mm diameter discs, has been developed to limit this voltage to a safe level.

Selecting the most suitable Metrosil component is vital to ensure that sufficient protection is provided. Depending on the relay setting voltage and the maximum secondary internal fault current, single discs are available for secondary internal fault currents up to 50A rms, while multiple discs connected in parallel are used for larger fault currents.

Relay protection applications

Read our data sheet for more information

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