Section 9 Secondary System Supervision - ABB REC650 Applications Manual

1MRK 511 286-UUS A
Section 9
9.1
9.1.1
9.1.2
Application manual
Secondary system supervision
Current circuit supervision CCSRDIF (87)
Identification
Function description
Current circuit supervision
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 CCSRDIF (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 personell. 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.
Secondary system supervision
IEC 61850 IEC 60617
identification identification
CCSRDIF -
Section 9
ANSI/IEEE C37.2
device number
87
171