GE L90 Instruction Manual page 266

5.6 CONTROL ELEMENTS
e) CT FAILURE DETECTOR
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PATH: SETTINGS CONTROL ELEMENTS
# CT FAILURE
# DETECTOR
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The CT Failure function is designed to detect problems with the system current transformers used to supply current to the
relay. This logic detects the presence of a zero sequence current at the supervised source of current without a simulta-
neous zero-sequence current at another source, zero-sequence voltage or some protection element condition.
The CT Failure logic (see figure below) is based on the presence of the zero sequence current in the supervised CT source
and absence of one of three or all three conditions as follows:
1. Zero sequence current at different source current (may be different set of CTs or different CT core of the same CT).
2. Zero sequence voltage at the assigned source.
3. Appropriate protection element or remote signal.
The CT Failure settings are described below.
• CT FAIL FUNCTION: This setting is used to Enable/Disable operation of the element.
• CT FAIL BLOCK: This setting is used to select a FlexLogic™ operand that blocks operation of the element during
some conditions (i.e. open pole in process of the single pole tripping-reclosing) when CT Fail should be blocked.
Remote signals representing operation of some remote current protection elements via communication channel or
local ones can be chosen as well.
• CT FAIL 3I0 INPUT 1: This setting is used to select the source for the current for Input 1. Most important protection
element of the relay should be assigned to the same source.
• CT FAIL 3I0 INPUT 1 PICKUP: This setting is used to select the pickup value for 3I_0 for Input 1 (main supervised CT
source) of the relay.
• CT FAIL 3I0 INPUT 2: This setting is used to select the source for the current for Input 2. Input 2 should use different
set of CTs or different CT core of the same CT. Against absence at Input 2 CT source (if exists), 3I_0 current logic is
built.
5-176
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MONITORING ELEMENTS
CT FAIL FUNCTION:
Disabled
CT FAIL BLOCK:
MESSAGE
Off
CT FAIL 3I0 INPUT 1:
MESSAGE
SRC 1
CT FAIL 3I0 INPUT 1
MESSAGE
PKP: 0.20 pu
CT FAIL 3I0 INPUT 2:
MESSAGE
SRC 2
CT FAIL 3I0 INPUT 2
MESSAGE
PKP: 0.20 pu
CT FAIL 3V0 INPUT:
MESSAGE
SRC 1
CT FAIL 3V0 INPUT
MESSAGE
PKP: 0.20 pu
CT FAIL PICKUP
MESSAGE
DELAY: 1.000 s
CT FAIL TARGET:
MESSAGE
Self-reset
CT FAIL EVENTS:
MESSAGE
Disabled
L90 Line Differential Relay
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CT FAILURE DETECTOR
Range: Disabled, Enabled
Range: FlexLogic™ operand
Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: 0.00 to 2.00 pu in steps of 0.01
Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: 0.00 to 2.00 pu in steps of 0.01
Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: 0.00 to 2.00 pu in steps of 0.01
Range: 0.000 to 65.535 s in steps of 0.001
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
5 SETTINGS
GE Multilin