6.2.3
Functionality
Phase segregated CT supervision function HZCCxSPVC is a dedicated phase-
segregated supervision function to be used along with the high-impedance differential
protection for detecting the broken CT secondary wires. The differential current is
taken as an input for the protection relay. During normal CT condition, the value of the
differential current is zero. However, when the CT is broken, the secondary
differential current starts flowing and it is used for generating alarms.
To avoid faulty operation, HZCCxSPVC should have a sensitive setting, compared to
the high-impedance differential protection. The function is likely to start under
through-fault conditions. However, by incorporating a high time delay (3 s or more),
the downstream protection clears the fault before an alarm is generated.
HZCCxSPVC generates an alarm when the differential current exceeds the set limit.
The function operates within the DT characteristic.
The function contains a blocking functionality. It is possible to block the function
output, Timer or the whole function.
6.2.4
Operation principle
The function can be enabled and disabled with the
Operation
setting. The
corresponding parameter values are "On" and "Off".
The operation of HZCCxSPVC can be generated with a module diagram. All the
modules in the diagram are explained in the next sections.
The module diagram illustrates all the phases of the function. However, the
functionality is described only for phase A. The functionality for phase B and C is
identical.
Section 6
1MRS757454 D
Supervision functions
340
611 series
Technical Manual
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