Page 247 - Practical Power System and Protective Relays Commissioning
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244 Practical Power System and Protective Relays Commissioning
FIGURE 18.7.11 Voltage-restrained OC relay for generators.
18.7.8 LOSS OF EXCITATION (FIELD FAILURE) PROTECTION
In this case there is steam to drive the turbine but no field current, and then
the machine absorbs reactive power Q from the system, leading to loss of
synchronism for the generator. To detect this condition an offset-Mho dis-
tance relay as shown in Fig. 18.7.13 was used.
18.7.9 OUT-OF-STEP (POLE SLIPPING) PROTECTION
Two Ohm relays are used to detect the out-of-step condition of the generator
(refer to Fig. 18.7.14).
