tDLD: The time delay for activating ZCVPSOF by the internal dead-line detection
is, by default, set to 0.2 seconds. It is suitable in most applications. The delay shall
not be set too short to avoid unwanted activations during transients in the system.
Mode: The operation of ZCVPSOF has three modes for defining the criteria for
tripping. The setting of Mode is, by default, UILevel, which means that the tripping
criterion is based on the setting of IPh< and UPh<. The choice of UILevel gives a
faster and more sensitive operation of the function, which is important for reducing
the stress that might occur when energizing onto a fault. However, the voltage
recovery can be slow in some systems when energizing the line. Therefore, if the
timer tDuration is set too short, ZCVPSOF can interpret this as a fault and release a
trip.
When Mode is set to Impedance, the operate criterion is based on the BC input
(breaker closing), which can be the start of the overreaching zone from the
impedance zone measurement or a tOperate-delayed START_DLYD input. A
nondirectional output signal should be used from an overreaching zone. The
selection of the Impedance mode gives increased security.
When Mode is set to UILvl&Imp, the condition for tripping is an ORed between
UILevel and Impedance.
tDuration: The setting of the timer for the release of UILevel is, by default, 0.02
seconds, which has proven to be suitable in most cases from field experience. If a
shorter time delay is to be set, it is necessary to consider the voltage recovery time
during line energization.
tOperate: The time delay for the START_DLYD input to activate TRIP when
Mode is set to Impedance or UILvl&Imp is, by default, set to 0.03 seconds.
1MRK 505 393-UEN B Section 7
Impedance protection
Line differential protection RED650 2.2 IEC 145
Application manual
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