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25
25.1
25.1.1
25.1.2
144
Definite time non-directional overcurrent
protection (TOC)
Definite time non-directional overcurrent
protection (TOC)
Prepare the terminal for verification of settings as outlined in
this chapter.
To verify the settings the following fault type should be tested:
•
One for a phase-to-earth fault
Ensure that the maximum continuous current of the terminal does not exceed four times its rated
value.
Measuring the operate limit of set values
Time delayed phase overcurrent
Procedure
1.
Inject a phase current in the terminal with start below the setting val-
ue.
2.
Increase the injected current (measured current) in the Ln phase un-
til the starting signal TOC--STLn (n=1-3) appears.
3.
Switch off the fault current.
Observe the maximum permitted overloading of the current circuits in the
terminal.
4.
Compare the measured operating current with the set value IP>.
5.
Set the fault current to about 1.5 times the measured operating cur-
rent.
6.
Switch on the fault current and measure the operating time of the
TOC protection. Use the TOC--TRP signal.
7.
Compare the measured time with the set value tP.
Time delayed residual overcurrent (non-dir.)
Procedure
1.
Inject a phase current in the terminal with start below the setting val-
ue.
2.
Increase the injected residual current (measured current) in the Ln
phase until the starting signal TOC--STN appears.
3.
Switch off the fault current.
Observe the maximum permitted overloading of the current circuits in the
terminal.
Chapter 13
Verifying settings by secondary
section 2 "Preparing for test"
injection
in
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