Metrosil provides effective protection against high voltage surges in high impedance relay schemes.
Correct Metrosil selection will ensure that protection is achieved with a leakage current low enough to have negligible effects on the accuracy of the relay at its maximum setting voltage. Our Relay Metrosils are available as single disc, two disc or three disc assemblies.
The Metrosil chosen depends on the relay setting voltage and the maximum secondary internal fault current.
Relays attached to Current Transformers with 1A rated Secondary Output
Single disc Metrosils are suitable for a 1A CT with maximum internal secondary fault currents of up to 50A rms.
Relays attached to Current Transformers with 5A rated Secondary Output
For a 5A CT with maximum internal secondary fault currents of up to 150A rms, we recommend a Metrosil assembly with multiple discs connected in parallel.