Section 14 Secondary system supervision
14.1 Current circuit supervision (87)
14.1.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Current circuit supervision CCSSPVC - 87
14.1.2 Application
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. When currents from two independent three-phase sets of CTs, or CT
cores, measuring the same primary currents are available, reliable current circuit
supervision can be arranged by comparing the currents from the two sets. If an error in any
CT circuit is detected, the protection functions concerned can be blocked and an alarm
given.
In case of large currents, unequal transient saturation of CT cores with different
remanence or different saturation factor may result in differences in the secondary
currents from the two CT sets. Unwanted blocking of protection functions during the
transient stage must then be avoided.
Current circuit supervision CCSSPVC (87) must be sensitive and have short operate time
in order to prevent unwanted tripping from fast-acting, sensitive numerical protections in
case of faulty CT secondary circuits.
Open CT circuits creates extremely high voltages in the circuits which is
extremely dangerous for the personnel. It can also damage the insulation
and cause new problems. The application shall, thus, be done with this in
consideration, especially if the protection functions are blocked.
1MRK 506 369-UUS - Section 14
Secondary system supervision
Line distance protection REL670 2.2 ANSI 623
Application manual
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