CHAPTER 9: COMMISSIONING TESTING
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 9-5
9
6. At the remote relay, make the following changes in the SETTINGS GROUPED ELEMENTS LINE DIFFERENTIAL
ELEMENT CURRENT DIFFERENTIAL
menu:
CURRENT DIFF DTT: “Enabled”
7. At the Local relay, make the following changes in the
SETTINGS INPUTS/OUTPUTS CONTACT OUTPUT N1 menu:
CONTACT OUTPUT N1 OPERATE: “87L DIFF RECVD DTT”
8. At the Local relay, verify that
ACTUAL VALUES STATUS CONTACT OUTPUTS Cont Op N1 is in the “Off” state.
9. Apply current to phase A of the remote relay and increase until 87L operates.
10. At the Local relay, observe
ACTUAL VALUES STATUS CONTACT OUTPUTS Cont Op N1 is now in the “On” state.
11. Repeat steps 8 through 10 for phases A and B and observe Contact Outputs N2 and N3, respectively.
12. Repeat steps 8 through 11 with the Remote and Local relays inter-changed.
13. Make the following setting change in the
SETTINGS GROUPED ELEMENTS LINE DIFFERENTIAL ELEMENT CURRENT
DIFFERENTIAL
menu of both relays:
CURRENT DIFF FUNCTION: “Disabled”
14. At the Remote relay, set
SETTINGS INPUTS/OUTPUTS CONTACT OUTPUT N1 CONTACT OUTPUT N1 OPERATE to
the CURRENT DIFF KEY DTT operand.
15. At the Local relay, observe under the
ACTUAL VALUES STATUS CONTACT OUTPUTS menu that CONTACT OUTPUT N1,
N2, and N3 are “Off”.
16. At the Remote relay, set
SETTINGS TESTING FORCE CONTACT INPUTS FORCE Cont Ip N1 to “Closed”.
17. At the Local relay, observe under
ACTUAL VALUES STATUS CONTACT OUTPUTS that CONTACT OUTPUT N1, N2, and N3
are now “On”.
18. At both the Local and Remote relays, return all settings to normal.
9.1.4.2 Final tests
As proper operation of the relay is fundamentally dependent on the correct installation and wiring of the CTs, it must be
confirmed that correct data is brought into the relays by an on-load test in which simultaneous measurements of current
and voltage phasors are made at all line terminals. These phasors and differential currents can be monitored at the
ACTUAL VALUES METERING 87L DIFFERENTIAL CURRENT menu where all current magnitudes and angles can be
observed and conclusions of proper relay interconnections can be made.
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