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1.8 PROTECTION SCHEME DESCRIPTIONS
For three terminal line applications, the pickup time of TL11 is decreased from 80 to 50 ms and the dropout
time of TL25 is increased from 30 to 60 ms to maintain security when an external fault is cleared quickly. These
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changes occur automatically when Protection Setting 1202: NUMRCVR (Number of Receivers) is set at 2, pro-
vided that Protection Setting 1201: PICKSCHEME is set for HYBRID.
The echo circuit plus OR305, OR306, AND305, AND306, TL27, AND405, and TL16 comprise the weak in-feed
tripping circuit. For the same internal fault condition outlined in the previous paragraph, AND405 produces an
output because of the following:
•
The NOT input to AND405 is satisfied because there is no output from the blocking or tripping functions.
•
There is an output from OR306, since either:
a) FD has operated,
b) V1 has dropped out.
•
The other two inputs to AND405 are satisfied, since a trip signal is being received and timer TL11 has not
timed out yet.
The output from AND406 energizes timer TL16, which produces a trip output when it times out. The adjustable
time-delay pickup of timer TL16 is provided for security against any spurious receiver output that might occur
during fault conditions supplied by NOT63.
Protection Setting 1205: WKINFTRIP (Select Weak Infeed Tripping) can be used to disable the Weak Infeed
Tripping logic. If WKINFTRIP is set to NO, the weak infeed tripping logic is disabled, but the Channel Repeat
(echo) logic is still in service to allow the strong end to trip as described previously.
The Out-of-Step Blocking option also includes an Out of Step oscillography feature. The OS data file contains
the real and imaginary components of the phase currents and voltages, sampled once per cycle for 180 cycles.
60 pre-trigger samples and 120 post-trigger samples are stored. Data is stored whenever an Out-of-Step Block
(OSB) condition is detected. Only one OS data file is stored in the LPS-D. Once the data is captured, it will not
be overwritten until it is retrieved from the LPS-D, or cleared by an OS data reset Action command.
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1.8.8 OUT-OF-STEP OSCILLOGRAPHY CAPTURE
LPS-D Line Protection System
1 PRODUCT DESCRIPTION
GE Power Management
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