GE 735

GE Power Management
735/737 Feeder Protection Relay 3-5
3 SETUP AND OPERATION 3.2 CONTROLS
3
3.2.7 GROUND TIME MULTIPLIER [7]
The ground time multiplier selects a multiple of the base curve shape for each curve. It is adjustable from 1 to 10 in steps of
1. Unlike the electromechanical time dial equivalent, trip times are directly proportional to the time multiplier values. For
example, all trip times on multiplier curve 10 are 10 times Curve 1. Curves are shown in Chapter 5 for overlays and visual
inspection. Formulas and tabular data are also given for use with computer software or manual plotting on other co-ordina-
tion curves. Use the ground time multiplier option switches to move the curve up or down (see Section 3.4: SWITCHES).
Figure 3–8: GROUND TIME MULTIPLIER SETTING
3.2.8 GROUND INSTANTANEOUS [8]
Instantaneous ground current trip level with no intentional delay (35 ms max.) is set with the ground instantaneous dial as a
multiple of the ground CT sensor. For residually connected phase CT ground sensing, the setting is a multiple of the phase
CTs. This setting is independent of the GROUND PICKUP dial setting ranges from 0.1 to 16 times the ground CT rating.
For example: PHASE CT RATING: 100:5 (residual ground sensing); GROUND FAULT TRIP: 400 A
SETTINGS: Ground Fault Instantaneous = 4 (4 × 100 = 400 A)
Figure 3–9: GROUND INSTANTANEOUS TRIP SETTING