Ct Failure (60Cts) - GE 339 Instruction Manual

S4 CONTROLS

CT failure (60CTS)

NOTE:
NOTE
NOTE:
NOTE
6–132
Failure of a CT secondary wiring that is open (one phase or two phases), can lead to
undesired operation by some of the enabled protection elements. These include the
differential protection, restricted ground fault, and sensitive overcurrent protection
elements operating based on sequence components such as neutral and negative
sequence instantaneous and timed over-current elements. The CT failure function is
designed to detect problems with system current transformers (CTs) used to supply
currents to the relay. The logic detects the presence of zero sequence current at the
supervised source without the presence of zero sequence voltage, or ground current.
The CT Failure element shows in the S4 CONTROLS menu only if the relay was ordered with
phase current and phase voltage inputs.
The voltage transformers connection used must be able to refer zero sequence voltage
from the primary to the secondary side. Therefore, this element should only be enabled
where the VT is of a five-limb construction, or comprises three single-phase units with the
primary star point grounded.
The following path is available using the keypad. For instructions on how to use the
keypad, please refer to Chapter 3 - Working with the Keypad.
PATH: SETPOINTS > S4 CONTROLS > CT FAILURE
CT FAILURE FUNCTION
Range: Disabled, Alarm, Latched Alarm
Default: Disabled
For details see Common
OUTPUT RELAY X
For details see Common
CT BLOCK 1 (3)
For details see Common
CT FAIL 3IO CURRENT PKP
Range: 0.03 to 2.00 x CT in steps of 0.01
Default: 0.10 x CT
This setting defines the level of neutral current, above which CT failure picks up. The
neutral current pickup level is expressed in the times phase CT rating set under the
SYSTEM SETUP > CURRENT SENSING
for more detail.
CT FAIL 3VO VOLTAGE INHIBIT
Range: 0.05 to 2.00 x VT in steps of 0.01
Default: 0.20 x VT
This setting defines the level of neutral voltage (3V0) above which CT failure detection is
inhibited. The inhibit level is expressed in the times VT rating set under the
SETUP > VOLTAGE SENSING
CT FAIL GND CURRENT INHIBIT
Range: 0.02 to 2.00 x CT in steps of 0.01
Default: 0.20 x CT
This setting defines the level of ground current above which CT failure detection is
inhibited. The inhibit level is expressed in the times ground CT rating set under the
SYSTEM SETUP > CURRENT SENSING
setpoints.
setpoints.
setpoints.
menu. Refer to the CT failure detection logic diagram
menu.
menu.
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: SETPOINTS
S2
S2 SYSTEM
S2