a- Test objective:
This test aimed to test the function of the main relay according to the approved final setting for each one, but here we generally discussed the main function which should be exist in most of approved final setting.
b- Required Equipment:
1. relay tester.
2. Multi-meter.
3. Wires.
c- Mechanical check and visual inspection:
1. Check for physical damage or defects.
2. Check case earth.
3. Check indications and LEDs.
4. Check the test switch for correct operation either shorting CT if exists or isolation of binary inputs/outputs.
d- Burden test
1. Adjust the voltage source at 125 volt DC.
2. Record reading of Ammeter in case of all binary output deactivated and in case of binary output activation.
3. Calculate the burden in case of normal operation (all binary output deactivated) and abnormal operation (in case of binary output activated) by multiplying the voltage and reading of the ammeter.
4. Compare the result with the existing burden exist in the relay manual.
e- Test connection and test procedure:
i. Binary input/output check:
1. To test binary input: Apply rated binary input DC voltage on each input and verify the status of the input through the relay's software or from the relay's LCD [if exists].
2. To test binary output: Using relay's software you can force binary output to close for certain time and using multi-meter you can measure binary output contact resistance it should be around zero which indicates binary output being closed.
ii. Measurements
1. Set CT ratio and VT ratio which used to the relay by studying the scheme.
2. By using FREJA we inject secondary-rated voltage and secondary-rated current
3. Record the primary value reading on the relay's screen.
iii. High Impedance Differential Protection for Bus Bar circuit (87B)
1. As per the final setting of the relay set (Numerical relay-Resistor Metrosil) the resistor must be adjusted to give the desired operating voltage at which the relay will operate.
2. Numerical relay setting the value of the secondary current and the value of the resistor is inserted for the relay then The relay calculatesthe actual voltage value by multiplying the value of the secondary current and the resistor then compare it with the setting voltage value.
– To test Pick up and drop off test:-3. Adjust the value of the series resistor as per the final setting and measure its value.
4. Inject current and gradually increase the value till relay operation.
5. Measure the pickup current and voltage across the series resistor.
– To test Time:
6. Take one normally open contact of the relay, adjust the sverker to (on time), and apply a voltage more than the setting value.
iv. Transformer differential (87T):
1. Transformer differential is a low impedance protection in which the current vector is measured as amplitude and angle and the measured current from transformer sides is summed together to calculate the differential current, If the current value exceeds the setting value the relay generates
a trip command.
2. To test the PICK UP & drop oft test, Inject current and increase its value gradually till relay operation, measure the value of the injected current and calculate the differential and restrain current, Repeat for each current transformer location, Decrease the current value gradually till relay drop off,
Measure the current and repeat for each current transformer location.
3. To test time test: Assign a normally open contact from the relay as a differential protection trip; inject a current more than the setting value, and Measure the tripping time.