Page 194 - Practical Power System and Protective Relays Commissioning
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Protection Relays Chapter | 18 195
FIGURE 18.4.4 Electromechanical relay circuit.
FIGURE 18.4.5 Relay inverse characteristic.
The characteristic curve is defined by BS 142 and, as shown in
Fig. 18.4.5, has two adjustments on the relay:
1. The current plug setting multiplier (PSM), which can be set based on
fault current as a multiplier of the setting current;
2. Time setting multiplier (TMS), which reflects the operating time of the
relay as a multiplication of the time multiplier (TM) by the relay operat-
ing time (TR) based on the relay characteristic type chosen on the relay,
for example, the standard inverse (SI) characteristic.
