GE 745 Instruction Manual page 163

CHAPTER 5: SETPOINTS
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
• W1(3) NEUTRAL TIME OC PICKUP: Enter the level of neutral current (in units of relay
nominal current) above which the winding 1(3) neutral time overcurrent element will
pickup and start timing.
• W1(3) NEUTRAL TIME OC SHAPE: Select the time overcurrent curve shape to be used
for the winding 1(3) neutral time overcurrent element. The Time Overcurrent Curves on
page 5–59 describe the time overcurrent curve shapes.
• W1(3) NEUTRAL TIME OC MULTIPLIER: Enter the multiplier constant by which the
selected time overcurrent curve shape (the base curve) is to be shifted in time.
• W1(3) NEUTRAL TIME OC RESET: Select "Linear" reset to coordinate with
electromechanical time overcurrent relays, in which the reset characteristic (when the
current falls below the reset threshold before tripping) is proportional to ratio of
energy accumulated to that required to trip. Select "Instantaneous" reset to
coordinate with relays, such as most static units, with instantaneous reset
characteristics.
FIGURE 5–18: Neutral time overcurrent scheme logic
S4 ELEMENTS
5–67