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Current circuit supervision, current based
(CTSU)
Chapter 6
Secondary system supervision
1 Current circuit supervision, current based (CTSU)
1.1 Application
Faulty information about current flows in a protected element might influence the security (line
differential protection) or dependability (line distance protection) of a complete protection sys-
tem.
The main purpose of the current circuit supervision function is to detect different faults in the
current secondary circuits and influence the operation of corresponding main protection func-
tions.
The signal can be configured to block different protection functions or initiate an alarm.
1.2 Functionality
The function compares the zero sequences currents, from the protection current transformer
core, with a reference zero sequence current, from another current transformer core. For exam-
ple from a measuring core.
The function issues an output signal when the difference is greater than the set value.
1.3 Function block
xx00000211.vsd
CTSU-
CTSU
BLOCK FAIL
ALARM
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