Schweitzer Engineering Laboratories SEL-311L, Instruction Manual, Page: 562 / 734

13-8 Testing, Troubleshooting, and Commissioning Date Code 20010625
SEL-311L Instruction Manual
M311L102
180˚
140˚
100˚
60˚
-60˚
-100˚
-140˚
Figure 13.2: Alpha Plane Element Accuracy Test Points
Phase operate elements 87LOPB and 87LOPC, and phase restraint elements 87LRB and
87LRC are identical to the A-phase elements, and are not tested here. They may be
tested with an identical procedure.
II: Test Negative-Sequence 87L Element Accuracy
Test the negative-sequence operate element 87LOP2. To test the negative sequence
operate element, apply a low-grade internal three-phase fault. Then increase one phase
current (creating negative-sequence current at one end) until the relay trips. Keep the
test current magnitudes less than three times nominal current to avoid having the CT
saturation detection logic block the 87L2 element.
Test the negative-sequence restraint element R87L2. To test the restraint element, apply
a single-phase current to the local relay. This simulates a weak-infeed internal fault,
deasserts the restraint element R87L2, and causes both relays to trip. Then increase the
remote current until the R87L2 asserts in the local relay. Continue to increase the
remote current until R87L2 deasserts. Finally, apply an internal ground fault with equal
current at each relay. Change the angle of the current on the remote relay until restraint
element R87L2 solidly asserts. This approach is graphically depicted in Figure 13.2.
Ground operate element 87LOPG and ground restraint element R87L2 are not tested here. They
may be tested with an identical procedure.
Required Equipment:
v
Two SEL-311L Relays with established 87L communications interface.
v
Three-phase secondary injection test equipment, or low-level test equipment such as the
SEL-AMS Adaptive Multichannel Source.
v
PC with terminal emulation software.
v
SEL cable C234A