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Introducing NGK Stanger’s

HIGH SPEED EARTHING SWITCHES

NGK Stanger’s automatic high speed earthing switches provide an economical alternative for circuit protection in applications that would otherwise require costly circuit breakers.  One of the most common applications of the high speed earthing switch is to provide protection of power transformers in circuits having enough impedance to limit the low side fault currents to values below the trip setting of source breakers.  The system relays signal the high speed earthing switch to close, imposing a deliberate single phase fault to ground on the high side of the power transformer which in turn causes the source breaker to open, clearing the fault.  Another popular application for the high speed earthing switch is in backup protection for a power transformer as part of a circuit breaker failure scheme or a circuit switcher failure scheme.  If a fault occurs and the power transformer’s main protective device (either a circuit breaker or a circuit switcher) fails to successfully operate to clear the fault within a defined period of time the high speed earthing switch is signaled by system relays to close, imposing a deliberate single phase fault to ground on the high side of the transformer and causing a remote breaker to trip, clearing the fault.

Drawings are available upon request.