6.4 Current transformer supervision for high-
impedance protection scheme HZCCxSPVC
6.4.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE
C37.2 device
number
Current transformer supervision
for high-impedance protection
scheme for phase A
HZCCASPVC MCS I_A MCS I_A
Current transformer supervision
for high-impedance protection
scheme for phase B
HZCCBSPVC MCS I_B MCS I_B
Current transformer supervision
for high-impedance protection
scheme for phase C
HZCCCSPVC MCS I_C MCS I_C
6.4.2 Function block
Figure 476: Function block
6.4.3 Functionality
The current transformer supervision for high-impedance protection scheme
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.
1MRS757644 H
Supervision functions
620 series
Technical Manual
891
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