ABB RELION 620 Series Technical Manual page 900

Section 6
Supervision functions
6.4.6
894
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 Start value setting is 0.1 pu
with an Alarm delay time of 3 s or more.
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.
GUID-FB4ECBAC-1408-4EE6-9F8E-F8F903C84A90 V1 EN
Figure 468: Broken secondary detection by HZCCxSPVC
1MRS757644 F
620 series
Technical Manual