IEC Very inv.; If the IEC Very inverse time characteristic is selected, the trip
signals TROC and TRIP will
operate after a time defined by the equation:
t s
k
I
StartCurr
[ ]
=
−
13 5
1
. *
IECEQUATION2435 V1 EN-US (Equation 95)
where:
t Operate time in seconds
I Measured value (for example, phase current)
StartCurr Set operate value
This means that if the measured phase current jumps from 0 to 2 times the set
operate level and time multiplier k is set to 1.0 s (default value), then the
TROC and TRIP signals will operate
after a time delay equal to 13.5 s ±
tolerance.
T
aking into account the above explanation, inject the voltages related to the
last part of the characteristic and inject a current IL1 200% higher than the set
operation level, and check the trip time delay.
If tDef_OC is set to a value dif
ferent from 0 s, then this time
delay is added to the one that is defined by the IDMT
characteristic.
10.
Check the start and operate information that are stored in the event menu.
11.
The previous step 8 or 9 may be repeated also for the first and second section
of the characteristic.
12. Supply the IED with symmetric three-phase voltages at their rated values. Go
to Main menu/Settings/IED Settings/Current protection/
VoltageRestOverCurr(51V,2(I>/U<))/VRPVOC(51V,2(I>/U<)):1/
Undervoltage and set the setting Operation_UV = On to activate the
undervoltage stage.
13. Slowly decrease the voltage in two phases simultaneously, until the STUV
and START signals appear.
14. Note the operate value. The set operate value in secondary volts is calculated
according to the following equation:
StartVolt UBase VT
VTprim100
3
× ×
sec
IECEQUATION2436 V1 EN-US (Equation 96)
If the VRPVOC function is used as an overcurrent protection
with undervoltage seal-in, it is necessary to first inject
sufficient current to activate the ST
OC signal before the
under-voltage step is allowed to operate. In order to achieve
that, apply symmetric three-phase voltages at their rated value
1MRK 505 378-UEN A Section 11
Testing functionality by secondary injection
Line differential protection RED670 2.2 IEC 195
Commissioning manual
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