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and in case of using “Maximum” mode for biasing (in case of single end fault) the bias current will be
same than the differential current so Slope 2 shall be calculated as:
Now the biased characteristic is set. Next should consider settings for the non biased/non restraint
stage I
di>Pick-up
.
The purpose of this stage is to ensure fast and also selective tripping of faults inside differential zone,
yet stabile operation on heavy outside faults. This stage operates only on absolute differential current
amount measured and is not blocked with harmonics or bias restraints.
Setting of the stage should be based into the weakest CT full saturation under worst case through fault
condition (since this causes that only the other side current is measured then and that causes all seen
current to be differential current).
For our example case the LV side maximum three phase short circuit current would be:
This current will be seen in HV side as:
Now when looking at our example CT ratings:
HV side: 150/5A 10P10
LV side: 1200/5A 5P10
Let’s calculate the secondary currents of this situation.
AQ-T216
Instruction manual
Version: 2.00
137
© Arcteq Relays Ltd
Содержание AQ 200 Series
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Страница 243: ...Figure 7 1 162 AQ T216 variant with binary input modules AQ T216 Instruction manual Version 2 00 Arcteq Relays Ltd 242 ...
Страница 264: ...Figure 8 11 184 Panel cut out and spacing of the IED AQ T216 Instruction manual Version 2 00 263 Arcteq Relays Ltd ...
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