CHAPTER 4: PROGRAMMING
239 MOTOR PROTECTION RELAY – INSTRUCTION MANUAL
4–35
4.5.2
Phase S/C
•
PHASE S/C TRIP:
In any application where the available short circuit current is above
the interrupting capability of the contactor, short circuit currents must cause a fuse or
circuit breaker to operate. This prevents damage to the contactor which is not designed
to interrupt normal levels of short circuit current. In an application with fuses, program
the setpoint
S4: PROTECTION\PHASE CURRENT\PHASE S/C\PHASE S\C TRIP:
OFF
to prevent the contactor from attempting to trip during a short circuit.
If a circuit breaker which can be tripped by an external contact closure is available
upstream from the contactor, it is possible to program the setpoint
S4:
PROTECTION\PHASE CURRENT\PHASE S/C\PHASE S\C TRIP: AUXILIARY
to
cause a short circuit to activate the auxiliary relay instead of the trip relay. Though, it is
also possible to activate both the trip & auxiliary relays simultaneously. The auxiliary
relay could then be connected to the upstream breaker to cause it to open for a short
circuit. Ensure that the auxiliary relay is only programmed to activate under short
circuit when used in this manner.
SPECIAL NOTE:
The AUXILIARY and TRIP status indicators will both operate for these
trips even if the TRIP relay is not selected for use (i.e. AUXILIARY). If the breaker cannot
be externally tripped, program the setpoint
S4: PROTECTION\PHASE
CURRENT\PHASE S/C\PHASE S\C TRIP: OFF
to prevent the contactor from
attempting to trip during a short circuit. If a breaker is used as the motor starter
interrupting device, short circuit protection would generally be enabled as it will
normally be capable of handling the fault current. Short circuit protection causes the
breaker to open quickly to prevent excessive mechanical damage or fire due to any
large phase current. Complete protection from phase-to-phase and phase-to-ground
faults is provided with this feature. When enabled, by programming setpoint
S4:
PROTECTION\PHASE CURRENT\PHASE S/C\PHASE S\C TRIP: TRIP
,
short circuit
protection is active at all times, including during motor starts. It can be disabled by
setting the setpoint
S4: PROTECTION\PHASE CURRENT\PHASE S/C\PHASE S\C
TRIP: OFF
.
•
PHASE S/C PICKUP:
The phase current short circuit trip level can be set from 1 to 11
times the phase CT primary. When any phase current meets or exceeds this setpoint
value during start or run conditions and is maintained for the
PHASE S/C DELAY
setpoint, the selected relay(s) will activate.
10
14369
8537
4166.8
699.9
291.6
166.6
109.3
58.3
36.43
24.98
13.88
8.83
7.29
11
15806
9391
4583.5
769.9
320.7
183.3
120.3
64.1
40.08
27.48
15.27
9.71
8.01
12
17243
10245 5000.2
839.9
349.9
199.9
131.2
70.0
43.72
29.98
16.65
10.60
8.74
13
18680
11098 5416.9
909.9
379.1
216.6
142.1
75.8
47.36
32.48
18.04
11.48
9.47
14
20116
11952 5833.5
979.9
408.2
233.2
153.0
81.6
51.01
34.97
19.43
12.36
10.20
15
21553
12806 6250.2 1049.8
437.4
249.9
164.0
87.4
54.65
37.47
20.82
13.25
10.93
Table 4–2: 239 Phase Overload Trip Times (Seconds)
CURVE
NUMBER
MULTIPLE OF MOTOR FULL LOAD CURRENT
1.03
1.05
1.1
1.5
2
2.5
3
4
5
6
8
10
11
Summary of Contents for Multilin 239
Page 6: ...TOC 4 369 MOTOR MANAGEMENT RELAY INSTRUCTION MANUAL TABLE OF CONTENTS ...
Page 20: ...1 14 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER 1 OVERVIEW ...
Page 48: ...3 10 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER 3 OPERATION ...
Page 96: ...4 58 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER 4 PROGRAMMING ...
Page 108: ...5 70 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER 5 MONITORING ...
Page 150: ...7 112 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER 7 TESTING ...
Page 152: ...A 2 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER A ...