Protection Engineering Basics and Schemes Protection Engineering | Page 119

Mostly employs at generators and transformer’s earth or
neutral points.
5.3.2.5: Customized TCC Relay:
Where user defines the characteristics of protection
scheme, mostly employees where system is isolated from
main grid /power system or used as per client
requirement or used in user define system.
5.3.3 Instantaneous Relay(50):
Relay with no time factor at time of operation is
instantaneous; it can operate as soon as fault induces in
system.
Usually we use instantaneous relay with inverse time
relay but we can used it separately where required
In Practice:
In Power systems , instantaneous relays settings are
about 8 to 10times of pick up time usually but not
definitely , remember instantaneous setting must cover
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