CHAPTER 5: SETTINGS
CONTROL ELEMENTS
L30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
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5.8.11.3 CT failure detector
SETTINGS
CONTROL ELEMENTS
MONITORING ELEMENTS
CT FAILURE DETECTOR 1(2)
The CT failure function detects problems with 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 simultaneous zero-
sequence current at another source, zero-sequence voltage, or some protection element condition.
The CT failure logic (see later) is based on the presence of the zero-sequence current in the supervised CT source and the
absence of one of three or all of the three following conditions:
•
Zero-sequence current at different source current (can be different set of CTs or different CT core of the same CT)
•
Zero-sequence voltage at the assigned source
•
Appropriate protection element or remote signal
Settings are described as follows.
CT FAIL 1 FUNCTION
— Enables or disables operation of the CT failure element.
CT FAIL 1 BLOCK
— Selects a FlexLogic operand to block operation of the element during some condition (for example, an
open pole in process of the single pole tripping-reclosing). Local signals or remote signals representing operation of some
remote current protection elements via communication channels can also be chosen.
CT FAIL 1 3I0 INPUT 1
— Selects the current source for input 1. The most critical protection element should also be assigned
to the same source.
CT FAIL 1 3I0 INPUT 1 PICKUP
— Selects the 3I_0 pickup value for input 1 (the main supervised CT source).
CT FAIL 1 3I0 INPUT 2
— Selects the current source for input 2. Input 2 should use a different set of CTs or a different CT core
of the same CT. If 3I_0 does not exist at source 2, then a CT failure is declared.
CT FAIL 1 3I0 INPUT 2 PICKUP
— Selects the 3I_0 pickup value for input 2 (different CT input) of the relay.
CT FAIL 1 3V0 INPUT
— Selects the voltage source.
CT FAIL 1 3V0 INPUT PICKUP
— Specifies the pickup value for the 3V_0 source.
CT FAIL 1 PICKUP DELAY
— Specifies the pickup delay of the CT failure element.
CT FAILURE
DETECTOR 1
CT FAIL 1 FUNCTION:
Disabled
Range: Disabled, Enabled
CT FAIL 1 BLOCK:
Off
Range: FlexLogic operand
CT FAIL 1 3I0 INP 1:
SRC 1
Range: SRC 1, SRC 2
CT FAIL 1 3I0 INP 1
PKP: 0.2 pu
Range: 0.1 to 2.0 pu in steps of 0.1
CT FAIL 1 3I0 INP 2:
SRC 2
Range: SRC 1, SRC 2
CT FAIL 1 3I0 INP 2
PKP: 0.2 pu
Range: 0.1 to 2.0 pu in steps of 0.1
CT FAIL 1 3V0 INPUT:
SRC 1
Range: SRC 1, SRC 2
CT FAIL 1 3V0 INPUT
PKP: 0.20 pu
Range: 0.04 to 2.00 pu in steps of 0.01
CT FAIL 1 PICKUP
DELAY: 1.000 s
Range: 0.000 to 65.535 s in steps of 0.001
CT FAIL 1 TARGET:
Self-reset
Range: Self-reset, Latched, Disabled
CT FAIL 1 EVENTS:
Disabled
Range: Disabled, Enabled