ABB Relion REQ650, Руководство по применению

Страница: 179 / 340

Section 9 Secondary system supervision
9.1 Current circuit supervision CCSRDIF
9.1.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Current circuit supervision CCSRDIF - 87
9.1.2 Application
Open or short circuited current transformer cores can cause unwanted operation of
many protection functions such as differential, earth-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 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.
9.1.3 Setting guidelines
GlobalBaseSel : Selects the global base value group used by the function to define
( IBase ), ( UBase ) and ( SBase ).
1MRK 505 291-UEN A
Section 9
Secondary system supervision
173
Application manual