ERL L-PRO 4000, User Manual

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Appendix L L-PRO Setting Example
D02706R02.30 L-PRO 4000 User Manual Appendix L-25
L-PRO Scheme Timers Summary
Table 1.3: DCB Scheme Timers
Timer Considerations
TD2 Upon receipt of a Blocking Signal at the local end from the remote end, TD2
extends the Blocking Signal to prevent a Scheme Trip.
The Blocking Signal should be extended by:
Time for the local 21-2 to de-assert (~1 cycle) – Blocking Signal Channel
Reset Time (i.e. the time for the removal of the Block to propagate from the
remote end to the local end) + Security Margin*.
TL2 Delays the local 21-2 from producing a Scheme Trip for at least as long as it
would take a Blocking Signal to arrive from the remote end.
Should be set longer than the remote end 21-4R (OR 50-67R) detection
time (~1 cycle) + Blocking Channel Time + Security Margin*.
Table 1.4: POTT Scheme Timers
Timer Considerations
TL1 TL1 is intended for Parallel Line applications**:
Delays or prevents scheme trip upon detection of a current reversal at the
local end.
Time Delay should be set to less than: Remote End 21-2 Detection Time
(~25msec) + Total End to End Channel Time
TD1 Also for Parallel Line Applications**:
Extends current reversal blocking of the Scheme Trip and Send.
Should be set such that it will not block the local relay if the fault becomes
forward and internal. However it needs to be set long enough to allow the
permissive trip from the remote end to de-assert in the event that the
remote fault reverses (remote external reverse fault).
So, set local TD2 to: Remote 21-2 Reset Time + Channel Reset Time +
Security Margin*.
Table 1.5: Scheme Selector Timers
Timer Considerations
TL3 Local fault duration must be greater than this time in order to produce a
Scheme Send.
POTT and PUTT = Permissive Trip
DCB = Block Signal (derived from 21-4R (OR 50N-67R) AND NOT 21-2)
TD3 Stretches the Scheme Send signal to ensure that it's received by the
remote end relay. Set longer than the channel pickup delay.