
Monitoring
23
Phase-sequence of voltage and
current supervision
The phase-sequence of three phase
voltage and current are monitored in the
normal condition to determine that the
secondary circuit of CT or VT is connected
with IED correctly.
3I0 polarity supervision
The IED compare the magnitude and
phase angle of the calculated zero
sequence current with the measured one
to determine that the polarity is connected
in a right way.
The third harmonic of voltage
supervision
If the third harmonic voltage is excessive,
the alarm without blocking protection will
be given with delay time for checking of the
secondary circuit of voltage transformer.
Auxiliary contacts of circuit
breaker supervision
Current flowing through the transmission
line and connected CB aux. contacts are
monitored in phase segregated. Therefore,
the conflict condition is reported as alarm.
For example, If CB aux. contacts indicate
that CB is open in phase A and at the same
time flowing current is measured in this
phase, related alarm is reported.
Broken conductor detection
The main purpose of the broken conductor
detection function is to detect the broken
conductors on protected transmission lines
and cables. Detection can initiate an alarm
or tripping.
Self-supervision
All
modules
can
perform
self-
supervision to its key hardware
components and program, as soon as
energizing. Parts of the modules are
self-supervised in real time. All internal
faults or abnormal conditions will
initiate an alarm. The fatal faults among
them will result in the whole IED
blocked
The sampled data from the redundant
A/D sampling channels compare with
each other in real time. If the difference
exceeds the specified threshold, it will
be considered as analog input channel
fault and the protection will be blocked
immediately
CPU module and communication
module
perform real
time
inter-
-supervision. Therefore communication
interruption between them is detected
and related alarm will be given
CRC checks for the setting, program
and configuration, etc.
Fault locator
The built-in fault locator is an impedance
measuring function
giving the distance
from the IED measuring location to the
fault position in km. The IED reports fault
location after the IED tripping.
Содержание CSC-161
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