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Protective Relays Testing and Commissioning Chapter | 20 359
Subchapter 20.8
Out-of-Step Relay Testing and
Commissioning
20.8.1 INTRODUCTION
This relay uses an Ohm relay characteristic to detect the power swing condi-
tion and to trip the system and isolate it at certain points (out-of-step tripping
scheme) (refer to Fig. 20.8.1).
When impedance passes from zone A to zone B to zone C, this is consid-
ered as a power swing and a trip will occur.
FIGURE 20.8.1 Power swing locus in an R X impedance diagram.
