Section 11 Secondary system supervision
About this chapter
This chapter describes functions like Current circuit supervision and Fuse failure
supervision. The way the functions work, their setting parameters, function blocks,
input and output signals and technical data are included for each function.
11.1 Current circuit supervision CCSRDIF (87)
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Current circuit supervision CCSRDIF - 87
11.1.1 Introduction
Open or short circuited current transformer cores can cause unwanted operation of
many protection functions such as differential, ground-fault current and negative-
sequence current functions.
It must be remembered that a blocking of protection functions at an occurrence of open
CT circuit will mean that the situation will remain and extremely high voltages will
stress the secondary circuit.
Current circuit supervision (CCSRDIF, 87) compares the residual current from a three
phase set of current transformer cores with the neutral point current on a separate input
taken from another set of cores on the current transformer.
A detection of a difference indicates a fault in the circuit and is used as alarm or to
block protection functions expected to give unwanted tripping.
11.1.2 Principle of operation
Current circuit supervision CCSRDIF (87) compares the absolute value of the vectorial
sum of the three phase currents |ΣIphase| and the numerical value of the residual
current |Iref| from another current transformer set, see figure
300.
The FAIL output will be set to a logical one when the following criteria are fulfilled:
1MRK505222-UUS C Section 11
Secondary system supervision
597
Technical reference manual
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