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3.5 GROUND FAULT (EARTH LEAKAGE)
TIME DELAY CONTROL
In systems with several levels of ground fault (earth leakage)
detection, time coordination is required for satisfactory opera-
tion. If ground fault protection is used on a bus, each motor
must have a shor ter time delay than the bus fault detector or a
fault in any motor will shut down the whole bus. In a solidly
grounded system, short time delays should be used to prevent
system damage unless the contactor is not capable of break-
ing the fault current in which case a backup detection system
of sufficient interrupt capacity should be allowed to operate first.
On resistance grounded systems where the fault is limited to
safe levels longer time delays can be used if there are no coor-
dination constraints. Short time delays may cause nuisance trip-
ping due to transients or capacitive charging currents and should
be avoided if possible.
Summary of Contents for PROTECT 4A-120
Page 1: ...MOTOR PROTECTION RELAY INSTRUCTION MANUAL ...
Page 5: ...2 FIGURE1 1 PROTECT 4A TYPICAL SYSTEM CONNECTION ...
Page 11: ...8 FIGURE 2 2 PHASE CT DIMENSIONS FIGURE 2 3 GROUND FAULT CT DIMENSIONS ...
Page 21: ...18 FIGURE 3 1 FRONT PANEL LAYOUT ...
Page 35: ...32 FIGURE 4 1 SINGLE PHASE INJECTION TESTING FIGURE 4 2 100 AMP CURRENT SOURCE ...
Page 39: ...36 FIGURE 4 3 GROUND FAULT EARTH LEAKAGE TEST ...
Page 44: ...41 FIGURE 5 1 HARDWARE BLOCK DIAGRAM ...
