100
Two step time delayed directional phase
overcurrent protection (TOC3)
Chapter 10
Verifying settings by secondary
injection
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.
19.1.4 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.
19.1.5 Measuring the operate limit of the directional lines.
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
X
R
Forward
Reverse
ArgDir
ArgDir
ArgNegRes
ArgNegRes
en01000118.vsd
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