7SG12 DAD N Commissioning
87/50 Setting
0.10
87/50 Setting
0.50
87/50 Setting
0.90
Table 4 – Differential Element PU/DO
Record the results and verify the accuracy complies with performance stated in the Performance Specification.
Verify the correct operation of the Trip Relays RL4, RL5 and the LED indication.
Repeat Tests for connections to Phase B and C.
10. Primary Injection Tests
Primary injection tests are required to prove the CT ratio and secondary connections to the relay.
Differential Currents
A xIn
B xIn
C xIn
Table 5 – Primary Injection Test Results
Inject using a primary injection test set and record and verify the expected levels on the instruments on the relay,
the Reference Currents and corresponding Spill current will be in phase when the Spill Angle is zero.
11. Fault Setting Tests
Fault setting tests use primary injection testing to verify the protection settings; they can conveniently be
combined with the current transformer ratio and polarity tests in section 10.1.
Isolate the auxiliary d.c. supplies for trip and alarm, remove the Trip and Intertrip links. Use the test circuit shown
in Fig 8. Inject primary current and record the values at which the relay operates. Relay operation is indicated by
LEDs . Check the operation of all the output relays selected for each protection function.
11.1 Differential protections
Isolate the auxiliary d.c. supplies for trip and alarm and remove the Trip and Intertrip links.
Check that the setting resistor is the correct ohmic value, also that the correct Differential settings are selected.
Measure the primary current for operation of the CT and 87/50 elements and record the value obtained.
12. Tripping and Intertripping Tests
Re-connect the auxiliary d.c. supplies for trip and alarm operations and insert the Trip and Inter-Trip links.
Simulate the operation of each external contact that initiates a status input and in each case check that
appropriate LED illuminates and that the correct tripping, intertripping and alarm initiation occurs.
Disconnect the d.c. power supply to the relay and check for correct PROTECTION INOPERATIVE alarm.
Operate all protection and alarm elements in turn by primary or secondary injection and check that the correct
tripping and indication occurs.
13. Tests Using Load Currents
Isolate the auxiliary d.c. supplies for the trip and alarm functions.
Ensure that the relay is set the assigned settings for the capacitor bank installation.
Energise the Capacitor Bank.
Utilising the INSTRUMENT Display verifies the correct meter readings for each of the instruments, noting the
following:-
•
Ensure all primary current displays are correct, thus verifying CT Ratio settings are correct.
•
Ensure all secondary current displays are correct, thus verifying CT input settings are correct.
©2010 Siemens Protection Devices Limited
Chapter 7 Page 7 of 8
Summary of Contents for 7SG12 DAD-N
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