GE Power Management
735/737 Feeder Protection Relay 6-1
6 TESTING 6.1 PROCEDURES
6
6 TESTING 6.1 PROCEDURES 6.1.1 PRIMARY INJECTION TESTING
This is the preferred method of testing as complete system operation can be checked by injecting current through the
phase and ground CTs. To do this a primary (high current) test set is required. The operation of the entire system including
CTs and wiring can then be checked. If this equipment is not available, secondary injection tests can be performed to check
everything except the CTs. This procedure is described in the following sections.
6.1.2 SECONDARY INJECTION TESTING
Single phase secondary injection testing can be performed using a test setup similar to that Figure 6–1: TEST SETUP on
page 6–2. Tests can be performed with the user programmed relay settings or with any others the tester requires. The relay
settings should be recorded on the relay setting sheet (see Section 6.2: TEST RECORDS on page 6–4) so they can be
reset when the relay is again put into service.
NEVER OPEN THE SECONDARY CIRCUIT OF A LIVE CT. THE HIGH VOLTAGE PRODUCED MAY RESULT IN
A SITUATION DANGEROUS TO BOTH PERSONNEL AND EQUIPMENT!
6.1.3 COMMUNICATIONS TEST
A PC equipped with an RS232/RS485 convertor and the Setup program can be used to establish communications with the
735 or 737. See Sections 2.2.4: COMMUNICATIONS on page 2–8 and 3.5: SETUP PROGRAM on page 3–11. With the
use of the setup program or Relaycom, custom scheme setpoints can be set and tested and the actual values screens can
be used to monitor metered data and pre-trip data. Relay operation can also be simulated for training or testing purposes to
understand how the relay operates.
6.1.4 PHASE CURRENT READING ACCURACY TEST
The 735/737 relay must read the phase current signals input from the CTs correctly to provide the instantaneous and timed
overcurrent protection. To determine if the relay is reading correctly set the phase pickup dial to 100% of the CT primary.
Use the 3 Phase Test Set to set the phase current injected into the phases. Usually a mid value and a high value are tested
(i.e. 40 and 400% of CT). Remember the current value injected will be dependent on whether 5A or 1A CTs are used in the
relay.
6.1.5 GROUND CURRENT READING ACCURACY TEST
This test is done in a similar manner to that for the phases. However lower or different values of injected current may be
desired to test.
6.1.6 INSTANTANEOUS PHASE OVERCURRENT PICKUP LEVEL TEST
Set the phase pickup dial to OFF. Set the phase instantaneous dial to the desired level. Usually a low and a high value are
tested (i.e. 4 x CT and 14 x CT). Using the 3-phase Test Set slowly increase the phase current injected until the trip or aux-
iliary relay (if assigned) is activated and the corresponding LED illuminated. Verify that the injected current at the time of trip
corresponds to the instantaneous trip level setting ±3%.
6.1.7 INSTANTANEOUS GROUND FAULT OVERCURRENT PICKUP LEVEL TEST
Set the ground pickup dial to OFF. Set the ground instantaneous dial to the desired level. Usually a low and a high value
are tested (i.e. 0.1 x CT and 8 x CT). Using the 3-phase Test Set slowly increase the current injected into the ground CT
input until the trip or auxiliary relay (depending upon how assigned) is activated and the corresponding LED illuminated.
Verify that the injected current at the time of trip corresponds to the instantaneous trip level setting ±3%.
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