ABB RELION REX640 Technical Manual page 1322

Supervision functions
6.3.7 Application
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 operation principle of HZCCxSPVC is similar to the high-
impedance differential protection function HIxPDIF. However, the current setting of
HZCCxSPVC is set to be much more sensitive than HIxPDIF and it operates with a
higher time delay. A typical example of the HZCCxSPVC
with an
As the current setting of HZCCxSPVC is more sensitive than the actual differential
stage, it can start internally under the through-fault conditions; however, a
sufficient time delay prevents false alarm. If the bus wire is broken, differential
current arises depending on the load of the feeder with the broken bus wire.
Figure 753: Broken secondary detection by HZCCxSPVC
1322
Alarm delay time of 3 s or more.
1MRS759142 F
Start value setting is 0.1 pu
REX640
Technical Manual