Page 197 - Practical Power System and Protective Relays Commissioning

198 Practical Power System and Protective Relays Commissioning

insulated system (GIS). They can replace the local control cubicle with
the bay controller IED and can also be a protection device which can
perform as, for example, a distance protection or busbar protection. They
are marketed by a number of different manufacturers. The most important
advantage of this type of relay is that it can be used in advanced adaptive
protection functions, where one relay can communicate with another relay
through a communication link protocol to take the trip decision by the
operation of the two relays.

18.4.3.1 Protection Intelligent Electronic Device
Most manufacturers classify it by the feeder circuit, which is protected by
this type of IED, for example, as follows.
The feeder protection IED includes the following functions and may
include more functions based on the system requirements:
Overcurrent protection—directional and nondirectional;
Distance protection;
Line differential protection with a fiber-optic link between the two sides
of the line;
Autoreclosure function;
Synchro check function.

The generator protection IED includes the following functions and may
include more functions based on the system requirements:
Overcurrent protection voltage-restrained or voltage-controlled;
100% stator earth fault protection;
95% stator earth fault protection;
Differential protection;
Restricted earth fault protection;
Back-up distance protection;
Reverse power protection;
Negative-phase sequence current protection;
Loss of excitation protection;
Out-of-step protection;
Over/under voltage protection;
Over/underfrequency protection.
The transformer protection IED includes the following functions and may
include more functions based on the system requirements:

Overload thermal replica impedance protection;
Overcurrent protection in two stages;
Earth fault protection in two stages;
Differential protection;