ABB Relion 670 series, Technical Reference Manual

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13.7.1 Introduction
Current reversal and weak-end infeed logic for phase segregated communication
(ZC1WPSCH, 85) function is used to prevent unwanted operations due to current
reversal when using permissive overreach protection schemes in application with
parallel lines when the overreach from the two ends overlaps on the parallel line.
The weak-end infeed logic is used in cases where the apparent power behind the
protection can be too low to activate the distance protection function. When activated,
received carrier signal together with local under voltage criteria and no reverse zone
operation gives an instantaneous trip. The received signal is also echoed back to
accelerate the sending end.
13.7.2 Principle of operation
13.7.2.1 Current reversal logic
The current reversal logic uses a reverse zone connected to the input IRVLx to
recognize the fault on the parallel line in phase Lx. When the reverse zone has been
activated for a certain settable time
tPickUpRev it prevents sending of a
communication signal and activation of trip signal for a predefined time tDelayRev .
This makes it possible for the carrier receive signal to reset before the carrier aided trip
signal is activated due to the current reversal by the forward directed zone, see figure
409 .
IRVLn
IRVBLKLn
IRVOPLn
t
tDelayRev
&
t
tPickUpRev
t
10 ms
t
tPickUpRev
IEC06000474_2_en.vsd
IEC06000474 V2 EN
Figure 409: Current reversal logic
The preventing of sending carrier send signal CSLn and activating of the TRIPLn in
the Scheme communication logic for distance or Overcurrent protection (ZCPSCH ,85)
is carried out by connecting the IRVOPLn signal to input BLOCKLn in ZCPSCH (85)
function.
The Current reversal and weak-end infeed logic for phase segregated communication
(ZC1WPSCH ,85) function has an internal 10 ms drop-off timer which secure that the
current reversal logic will be activated for short input signals even if the pick-up timer
is set to zero.
1MRK505222-UUS C
Section 13
Scheme communication
823
Technical reference manual