ABB Relion 670 series, Руководство по применению, Страница: 612 / 760

15.2.2 Application
SEMOD141787-1 v1
SEMOD141790-4 v2
To achieve fast fault clearing for a fault on the part of the line not covered by the
instantaneous zone1, the stepped distance protection function can be supported with logic
that uses communication channels.
For the Phase segregated scheme communication logic for distance protection (ZC1PPSCH)
three channels 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 channels
speed, and security against false or lost signals. Special communication channels are used for
this purpose. When power line carrier is used for communication, these special channels are
strongly recommended due to the communication disturbance caused by the primary fault.
Communication speed, or minimum time delay, is always of utmost importance because the
purpose for using communication is to improve the total 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 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 scheme
• permissive schemes (overreach and underreach)
• direct intertrip
A permissive scheme is inherently faster and has better security against false tripping than a
blocking scheme. On the other hand, permissive scheme depends on a received CR signal for a
fast trip, so its dependability is lower than that of a blocking scheme.
When single-pole tripping is required on parallel lines, an unwanted three-phase trip can occur
for simultaneous faults near the line end (typical last 20%). Simultaneous faults are one fault
on each of the two lines but in different phases, see figure 378 . When simultaneous faults
occur, the phase selectors at the remote protection IED - relative to the faults, see the A side in
figure 378 - cannot discriminate between the fault on the protected line and on the parallel
line. The phase selector must be set to cover the whole line with a margin and will also detect a
fault on the parallel line. Instantaneous phase-selective tripping for simultaneous faults close
to line end is not possible with the information that is available locally in the remote protection
IEDs relative to the faults. The protection IED near the faults detects the faults on the
protected line as a forward fault, and on the parallel line in reverse direction. The directional
phase selector in the two IEDs near the faults can discriminate between the faults and issue
correct single-pole tripping commands.
Section 15 1MRK 505 343-UEN B
Scheme communication
606
Application manual