S4 Current Elements; Description; Example: Short Circuit - GE Multilin 369 Quick Start Manual

S4 CURRENT ELEMENTS

4.5 S4 Current Elements
4.5.1

Description

4.5.2

Example: Short Circuit

SHORT CIRCUIT
Note
4–40
These elements deal with functions that are based on the current readings of the 369 from
the external phase and/or ground CTs. All models of the 369 include these features.
PATH: S4 CURRENT ELEMENTS
SHORT CIRCUIT
TRIP: Off
ASSIGN S/C TRIP
RELAYS: Trip
SHORT CIRCUIT TRIP
LEVEL: 10.0 x CT
ADD S/C TRIP
DELAY: 0.00 s
SHORT CIRCUIT TRIP
BACKUP: Off
ASSIGN S/C BACKUP
RELAYS: Aux1
ADD S/C BACKUP TRIP
DELAY: 0.20 s
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, this feature should be
disabled. Alternatively, this feature may be assigned to an auxiliary relay and
connected such that it trips an upstream device that is capable of breaking the fault
current.
Once the magnitude of either phase A, B, or C exceeds the Pickup Level × Phase CT Primary
for a period of time specified by the delay, a trip will occur. Note the delay is in addition to
the 45 ms instantaneous operate time.
There is also a backup trip feature that can be enabled. The backup delay should be
greater than the short circuit delay plus the breaker clearing time. If a short circuit trip
occurs with the backup on, and the phase current to the motor persists for a period of time
that exceeds the backup delay, a second backup trip will occur. It is intended that this
second trip be assigned to Aux1 or Aux2 which would be dedicated as an upstream
breaker trip relay.
Various situations (e.g. charging a long line to the motor or power factor correction
capacitors) may cause transient inrush currents during motor starting that may exceed
the Short Circuit Pickup level for a very short period of time. The Short Circuit time delay is
adjustable in 10 ms increments. The delay can be fine tuned to an application such that it
CHAPTER 4: KEYPAD SETPOINTS
SHORT CIRCUIT
Range: 50/60 Hz Nominal: Off, Latched, Unlatched
Variable: Off, Latched
Range: None, Trip, Aux1, Aux2, or combinations of
them
Range: 2.0 to 20.0 x CT in steps of 0.1
Range: 0 to 255.00 s in steps of 0.01
0 = Instantaneous
Range: 50/60 Hz Nominal: Off, Latched, Unlatched
Variable: Off, Latched
Range: None, Aux1, Aux2, or combinations of them
Range: 0 to 255.00 s in steps of 0.01
0 = Instantaneous
369 MOTOR MANAGEMENT RELAY – QUICKSTART GUIDE