types of communication schemes for permissive
underreaching, permissive overreaching, blocking, delta
based blocking, unblocking and intertrip are available.
The built-in communication module (LDCM) can be used
for scheme communication signaling when included.
Phase segregated scheme communication logic for
distance protection ZC1PPSCH
SEMOD141686-4 v3
Communication between line ends is used to achieve
fault clearance for all faults on a power line. All possible
types of communication schemes for example,
permissive underreach, permissive overreach and
blocking schemes are available. To manage problems
with simultaneous faults on parallel power lines phase
segregated communication is needed. This will then
replace the standard Scheme communication logic for
distance or Overcurrent protection (ZCPSCH) on
important lines where three communication channels (in
each subsystem) are available for the distance
protection communication.
The main purpose of the Phase segregated scheme
communication logic for distance protection
(ZC1PPSCH) function is to supplement the distance
protection function such that:
• fast clearance of faults is also achieved at the line end
for which the faults are on the part of the line not
covered by its underreaching zone.
• correct phase selection can be maintained to support
single-pole tripping for faults occurring anywhere on
the entire length of a double circuit line.
To accomplish this, three separate communication
channels, that is, one per phase, each capable of
transmitting a signal in each direction is required.
ZC1PPSCH can be completed with the current reversal
and WEI logic for phase segregated communication,
when found necessary in Blocking and Permissive
overreaching schemes.
Current reversal and weak-end infeed logic for
distance protection ZCRWPSCH
M13896-3 v15
The ZCRWPSCH function provides the current reversal
and weak end infeed logic functions that supplement
the standard scheme communication logic. It is not
suitable for standalone use as it requires inputs from
the distance protection functions and the scheme
communications function included within the terminal.
On detection of a current reversal, the current reversal
logic provides an output to block the sending of the
teleprotection signal to the remote end, and to block
the permissive tripping at the local end. This blocking
condition is maintained long enough to ensure that no
unwanted operation will occur as a result of the current
reversal.
On verification of a weak end infeed condition, the weak
end infeed logic provides an output for sending the
received teleprotection signal back to the remote
sending end and other output(s) for local tripping. For
terminals equipped for single- and two-pole tripping,
outputs for the faulted phase(s) are provided.
Undervoltage detectors are used to detect the faulted
phase(s).
Current reversal and weak-end infeed logic for phase
segregated communication ZC1WPSCH
SEMOD156473-5 v3
Current reversal and weak-end infeed logic for phase
segregated communication (ZC1WPSCH) function is
used to prevent unwanted operations due to current
reversal when using permissive overreach protection
schemes in application with parallel lines where 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
undervoltage criteria and no reverse zone operation
gives an instantaneous trip. The received signal is also
echoed back to accelerate the sending end.
Local acceleration logic ZCLCPSCH
M13823-3 v7
To achieve fast clearing of faults on the whole line, when
no communication channel is available, local
acceleration logic (ZCLCPSCH) can be used. This logic
enables fast fault clearing and re-closing during certain
conditions, but naturally, it can not fully replace a
communication channel.
The logic can be controlled either by the autorecloser
(zone extension) or by the loss-of-load current (loss-of-
load acceleration).
Scheme communication logic for residual
overcurrent protection ECPSCH
M13918-4 v11
To achieve fast fault clearance of earth faults on the
part of the line not covered by the instantaneous step of
the residual overcurrent protection, the directional
residual overcurrent protection can be supported with a
logic that uses communication channels.
In the directional scheme, information of the fault
current direction must be transmitted to the other line
end. With directional comparison, a short operate time
of the protection including a channel transmission time,
can be achieved. This short operate time enables rapid
autoreclosing function after the fault clearance.
The communication logic module for directional residual
current protection enables blocking as well as
permissive under/overreaching, and unblocking
schemes. The logic can also be supported by additional
Line differential protection RED670
1MRK 505 379-BEN N
46 Hitachi Power Grids
© Copyright 2017 Hitachi Power Grids. All rights reserved
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