If the following conditions are met, they may be used in the same fashion as receiving a
permissive signal from the remote end, without the need for a communications channel:
1.
Three-phase load was present before the fault (therefore the remote end of the
transmission line was closed).
2.
Three-phase current was lost, signifying that the remote end of the transmission line has
opened its breaker.
3.
Current above a certain threshold is detected in at least one of the three phases, signify-
ing that a fault may be present.
When all of these conditions are met, and an overreaching protective element asserts, the
relay can issue an accelerated trip.
Pilotless Tripping with the SEL-221F Relay
The SEL-221F relay includes the overcurrent elements defined below. The elements are
defined using "+" as logical OR and " *" as logical AND:
5OG = 50AG + 50BG + 50CG
3G50 = 50AG * 50BG * 50CG
3G50D = 3G50 *(2 cycle TDDO)
50P = 50AP + 50BP + 50CP
3P50 = 50AP * 50BP * 50CP
3P50D = 3P50 * (2 cycle TDDO)
50G asserts when any phase current is above the
50NG setting.
3G50 asserts when all three phase currents are above
the 50NG setting.
3G50D is an instantaneous pickup, two-cycle time
delayed dropout 3G50 element.
50P asserts when any phase current is above the 50P
setting.
3P50 asserts when all three phase currents are above
the 50P setting.
3P50D is an instantaneous pickup, two cycle time
delayed dropout 3P50 element.
Referring the new overcurrent elements to the pilotless tripping scheme described above, the
relay sets or clears the elements based on the conditions described below.
1.
The 3G50 element is set by three-phase load current.
2.
The 3G50D element indicates that load current was present up until at least 2 cycles ago.
3.
If the 50G element is picked up, current is still flowing in at least one phase.
4.
When REJOE = G, the REJO element is defined by the following logic equation:
Date Code 920508
Applications
SEL-221F, -1 Instruction Manual
5-25
Summary of Contents for SEL-221F
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Page 110: ...Example Event Report 2 4 12 Event Reporting SEL 221F 1 Instruction Manual Date Code 930830 ...
Page 158: ...SETTINGS SHEET FOR SEL 221F RELAY PAGE 2 OF 6 DATE Date Code 921110 ...
Page 160: ...SETTINGS SHEET PAGE 4 OF 6 FOR SEL 221F RELAY DATE Date Code 930601 ...
Page 161: ...SETTINGS SHEET PAGE 5 OF 6 FOR SEL 221F RELAY DATE Date Code 961208 ...
Page 229: ...SEL 200 Series Relay Main Board Troubleshooting Test Points and Jumper Locations ...