ABB Relion 670 Series Applications Manual page 441

1MRK 511 401-UEN Rev. K
Section 16
16.1 Scheme communication logic for distance or
overcurrent protection ZCPSCH
16.1.1 Identification
Function description
Scheme communication logic for
distance or overcurrent protection
16.1.2 Application
To achieve fast fault clearing for a fault on the part of the line not covered by the
instantaneous zone 1, the stepped distance protection function can be supported with logic
that uses a communication channel.
One communication channel in each direction, which can transmit an on/off signal is required.
The performance and security of this function is directly related to the transmission channel
speed and security against false or lost signals. Communication speed, or minimum time
delay, is always of utmost importance because the purpose for using communication is to
improve the tripping speed of the scheme.
To avoid false signals that could cause false tripping, it is necessary to pay attention to the
security of the communication channel. At the same time it is important to pay attention to
the communication channel dependability to ensure that proper signals are communicated
during power system faults, the time during which the protection schemes must perform their
tasks flawlessly.
The logic supports the following communications schemes:
• blocking schemes (blocking and delta blocking)
• permissive schemes (overreaching and underreaching)
• unblocking scheme and direct intertrip
A permissive scheme is inherently faster and has better security against false tripping than a
blocking scheme. On the other hand, a permissive scheme depend on a received CR signal for a
fast trip, so its dependability is lower than that of a blocking scheme.
16.1.2.1 Blocking schemes
In a blocking scheme a reverse looking zone is used to send a block signal to the remote end to
block an overreaching zone.
Since the scheme is sending the blocking signal during conditions where the protected line is
healthy, it is common to use the line itself as communication media (PLC). The scheme can be
used on all line lengths.
The blocking scheme is very dependable because it will operate for faults anywhere on the
protected line if the communication channel is out of service. On the other hand, it is less
Bay control REC670
Application manual
Scheme communication
IEC 61850
identification
ZCPSCH
© Copyright 2017 Hitachi Power Grids. All rights reserved
IEC 60617 ANSI/IEEE C37.2
identification device number
- 85
Section 16
Scheme communication
IP15749-1 v3
M14854-1 v4
IP15020-1 v1
M16866-3 v5
M16866-24 v5
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