Short Circuit - GE 339 Instruction Manual

S3 PROTECTION

Short circuit

NOTE:
NOTE
6–72
If Short Circuit is enabled, a trip or alarm occurs once the magnitude of any phase current
exceeds the setting S/C PKP for the time specified by the setting S/C DELAY.
A second independent Short Circuit protection element is provided for High Speed. If two-
speed functionality is enabled, the 339 relay relies on the motor speed indication to switch
the Short Circuit settings as per the motor running speed, so the main Short Circuit is only
active when the motor is running at low speed, and the High Speed Short Circuit is only
active when the motor is running at high speed. If two-speed functionality is not deployed,
only the main Short Circuit is active, and the High Speed Short Circuit is disabled.
Short Circuit operation is a serious event, and therefore results in a lockout that cannot be
reset unless an Emergency Restart or a Lockout Reset is issued.
Warning: care must be taken when turning on this feature. If the interrupting device
(contactor or circuit breaker) is not rated to break the fault current, the function of this
feature should not be programmed as TRIP. Alternatively, this feature may be programmed
as ALARM or LATCHED ALARM and assigned to an auxiliary relay connected to an
upstream device which is capable of breaking the fault current.
PATH: SETPOINTS > S3 PROTECTION > SHORT CIRCUIT
S/C FUNC
Range: Disabled, Latched Alarm, Alarm, Trip
Default: Disabled
The selection of the Latched Alarm, Alarm, or Trip setting enables the Short Circuit
function. If the operating condition is satisfied when Trip is selected as the function, the
"LOCKOUT" LED will be turned on, and the logic operand ANY TRIP OP will be asserted,
which in turn will operate the "TRIP" LED and trip output relay. If Alarm is selected, the
"ALARM" LED will flash upon Short Circuit operation, and will automatically reset when
the activating condition clears. If Latched Alarm is selected, the "ALARM" LED will flash
upon Short Circuit operation, and will stay "ON" after the condition clears, until a reset
command is initiated. The TRIP output relay will not operate if the Latched Alarm or
Alarm function is selected. Any assignable output relays can be selected to operate
when the setting S/C FUNC is selected as Latched Alarm, Alarm, or Trip.
S/C PKP
Range: 1.00 to 20.00xCT in steps of 0.01xCT
Default: 6.00xCT
This setting specifies a pickup threshold for the Short Circuit.
S/C DELAY
Range: 0.00 to 60.00 s in steps of 0.01 s
Default: 0.00 s
This setting specifies a time delay for the Short Circuit.
OUTPUT RELAY 4 to 6 / OUTPUT RELAY 5 to 6
Range: Do not operate, Operate
Default: Do not operate
Any assignable output relay can be selected to operate upon Short Circuit operation.
When the SWITCHING DEVICE is selected as BREAKER, the assignable output relays will
be Output Relay 4 to 6. When the SWITCHING DEVICE is selected as CONTACTOR, the
assignable output relays will be Output Relay 5 to 6.
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: SETPOINTS