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Timer
The time characteristic is according to DT. When the alarm timer reaches the value set by
Alarm delay time
, the
ALARM
output is activated. If the fault disappears before the module
generates an alarm signal, the reset timer is activated. If the reset timer reaches the value
set by
Reset delay time
, the alarm timer resets. The activation of the
BLOCK
signal resets
the Timer and deactivates the
ALARM
output.
Lockout logic
MCS-A, MCS-B, MCS-C is provided with the possibility to activate a lockout for the
ALARM
output depending on the
Alarm output mode
setting. In the "Lockout" mode, the
ALARM
must be reset manually from the LHMI Clear menu after checking the CT
secondary circuit. In the "Non-latched" mode, the
ALARM
output functions normally, that
is, it resets as soon as the fault is cleared.
6.3.5
Measuring modes
The function operates on two alternative measurement modes, DFT and Peak-to-Peak.
The measurement mode is selected using the
Measurement mode
setting.
6.3.6
Application
MCS-A, MCS-B, MCS-C 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 MCS-A, MCS-B, MCS-C is similar to the
high-impedance differential protection function 87A, 87B, 87C. However, the current
setting of MCS-A, MCS-B, MCS-C is set to be much more sensitive than 87A, 87B, 87C
and it trips with a higher time delay. A typical example of the MCS-A, MCS-B, MCS-C
Pickup value
setting is 0.1 pu with an
Alarm delay time
of 3 s or more.
As the current setting of MCS-A, MCS-B, MCS-C is more sensitive than the actual
differential stage, it can pick up 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.
Section 6
1MAC059074-MB A
Supervision functions
856
615 series ANSI
Technical Manual
Содержание Relion 615 series
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