ABB Relion 650 Series Technical Manual page 359

1MRK 506 326-UUS B
Table 290: ECPSCH (85) Group settings (advanced)
Name Values (Range)
Unblock Disabled
NoRestart
Restart
tSecurity 0.000 - 60.000
11.4.6 Operation principle
The four step directional residual overcurrent protection EF4PTOC (51N/67N) is configured to give
input information, that is directional fault detection signals, to the ECPSCH (85) logic:
• Input signal PLTR_CRD is used for tripping of the communication scheme, normally the pickup
signal of a forward overreaching step of STFW.
• Input signal CS_STOP is used for sending block signal in the blocking communication scheme,
normally thepickup signal of a reverse overreaching step of STRV.
• Input signal CSUR is used for sending permissive signal in the underreaching permissive
communication scheme, normally the pickup signal of a forward underreaching step of STINn,
where n corresponds to the underreaching step.
• Input signal CSOR is used for sending permissive signal in the overreaching permissive
communication scheme, normally the pickup signal of a forward overreaching step of STINn,
where n corresponds to the overreaching step.
11.4.6.1 Blocking scheme
In the blocking scheme a signal is sent to the other line end if the directional element detects a
ground fault in the reverse direction. When the forward directional element operates, it trips after
a short time delay if no blocking signal is received from the opposite line end. The time delay,
normally 30 – 40 ms, depends on the communication transmission time and a chosen safety
margin.
One advantage of the blocking scheme is that only one channel (carrier frequency) is needed if the
ratio of source impedances at both end is approximately equal for zero and positive sequence
source impedances, the channel can be shared with the impedance measuring system, if that
system also works in the blocking mode. The communication signal is transmitted on a healthy
line and no signal attenuation will occur due to the fault.
Blocking schemes are particular favorable for three-terminal applications if there is no zero-
sequence outfeed from the tapping. The blocking scheme is immune to current reversals because
the received signal is maintained long enough to avoid unwanted operation due to current
reversal. There is never any need for weak-end infeed logic, because the strong end trips for an
internal fault when no blocking signal is received from the weak end. The fault clearing time is
however generally longer for a blocking scheme than for a permissive scheme.
If the fault is on the line, the forward direction measuring element operates. If no blocking signal
comes from the other line end via the CR binary input (received signal) the TRIP output is activated
after the
Line distance protection REL650
Technical manual
Unit
-
s
tCoord set time delay.
© Copyright 2011 ABB Power Grids. All rights reserved
Step Default
- Disabled
0.001 0.035
Scheme communication
Description
Operation mode of unblocking logic
Security timer for loss of carrier guard
detection
Section 11
M13922-4 v4
M13922-9 v4
353