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1MRK 504 165-UEN Rev. K
on the secondary side. The corresponding trip signals TROC and TRIP will be activated after
the pre-set time delay has expired.
5.
Decrease the current IL1 slowly and note the reset value.
6.
Repeat steps 4 and 5 applying voltages that are related to the second and the last section of
the characteristic; the function operates when IL1 is slightly higher than: 0.5 A in the second
section; 1A in the last section.
7.
Connect the trip output contact to the input channel of the test set in order to stop the injection
and measure the trip time.
8.
If definite time delay is used for the overcurrent step, set the setting Characterist = IEC Def.
Time. Apply 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 definite time delay for trip (the signals
TROC and TRIP of the protection function VRPVOC are active in trip condition).
9.
If inverse time delay is used for the overcurrent step, the parameter setting Characterist shall
be properly set; we can refer, for example, to the setting 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
IECEQUATION2435 V1 EN-US
where:
t
I
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.
Taking 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.
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
IECEQUATION2436 V1 EN-US
Transformer protection RET670
Commissioning manual
13 5
. *
k
=
I
−
1
StartCurr
Operate time in seconds
Measured value (for example, phase current)
If tDef_OC is set to a value different from 0 s, then this time delay is added to the
one that is defined by the IDMT characteristic.
VT
sec
×
×
100
VTprim
3
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Section 11
Testing functionality by secondary injection
(Equation 98)
(Equation 99)
189
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