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19.1.4
19.1.5
100
Two step time delayed directional phase
overcurrent protection (TOC3)
2.
Check the time delay at two points of the inverse time curve.
Check with the current I>Low or 2·I>Inv (the highest value of
these two) and the current that according to the inverse time curve
corresponds to tMin.
3.
Increase the current 10% and check that the operation time is
equal to tMin.
4.
Set tLow to the correct value and check with a high current
that the operation time is equal to tMin+tLow.
Measuring the operate limit of the high step overcurrent protection
1.
Set temporarily tHigh=0.000 s.
2.
Inject a phase current slightly smaller than the operation val-
ue I>High and three-phase symmetrical voltage if directional.
3.
Increase the current slowly and check the operation value by
observing when the signal TOC3-TRHS appears.
4.
Compare the result of the measurement with the set value.
5.
Set tHigh to the correct value.
6.
Set a current 1.5 times I>High on the injection test equipment
7.
Switch the current on and compare the operation time with
the set value tHigh.
Measuring the operate limit of the directional lines.
X
Forward
ArgNegRes
Figure 9: Definitions for forward and reverse directions
Procedure
1.
Inject a current 1.2 times I>Low and a three-phase symmetri-
cal voltage.
X
R
ArgDir
ArgDir
ArgNegRes
Reverse
Chapter 10
Verifying settings by secondary
R
en01000118.vsd
injection
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