Surge protectors for current transformers

Surge protection and open-circuit protection of current transformers may be obtained by the application of shunts in which the material known as “thyrite,” and which has a negative resistance characteristic, is used. The surge protector is connected across the current transformer primary, and the open-circuit protector across the secondary. Voltages across the current transformer winding are considerably reduced by the use of these protectors, with negligible effect upon the transformer accuracy during normal operating conditions, and without impairing safe operation of relays during system faults.