Load encroachment
Load encroachment operates on the same measuring principles as the impedance
measuring zones. Thus, it is necessary to follow the same principles as for distance
protection when performing the secondary injection tests. Measure operating
characteristics during constant current conditions. Keep the injected current as close
as possible to the rated value of its associated input transformer or lower. Ensure,
however, that it is higher than 30% of the rated current. Ensure that the maximum
continuous current of an IED does not exceed four times Its rated value, if the
measurement of the operating characteristics runs under constant voltage conditions.
Measuring the operate limit of set values of load encroachment function
The load encroachment does not have any special output to be verified. It can only be
verified with the distance START and TRIP outputs.
Steps to test the load encroachment:
1. Supply the IED with healthy conditions for at least two seconds.
2. Apply the fault condition and slowly decrease the injected impedance to find the
operate value for of the phase-to-earth and phase-to-phase loops.
Under voltage seal-in
The under voltage seal-in logic can be verified using the TRUV and STUV outputs.
Steps to verify the logic:
1. Keep all the current and voltage in normal balanced condition.
2. Keeping the phase current at rated value, slowly reduce the voltage till it enters
into the respective zone mho characteristics and also below the set value of the
under voltage seal-in logic.
3. Before the operate time delay of the respective zone, reduce the current
magnitude so that the operating impedance moves out of the mho characteristics.
4. The under voltage seal-in should give a START and TRIP after the operate time
delay is set for the under voltage logic.
12.4.7.2 Completing the test
Continue to test another function or end the testing by setting the parameter TestMode
to Off under Main menu/Tests/IED test mode/1: TESTMODE. If another function
is tested, then set the parameter Blocked to No under Main menu/Tests/Function test
modes/Impedance/ZGVPDIS/1: ZGVPDIS for the function, or for each individual
function in a chain, to be tested next. Remember to set the parameter Blocked to Yes,
for each individual function that has been tested.
1MRK502053-UEN B Section 12
Testing functionality by secondary injection
Generator protection REG670 2.0 IEC 145
Commissioning manual
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