ABB Relion 670 Series Applications Manual page 421

1MRK 511 401-UUS F
the teleprotection scheme has switched on to forward direction, we will have an unwanted
operation of breaker B2 at B side.
Strong
source
ANSI99000044 V1 EN-US
Figure 199: Current distribution for a fault close to B side when breaker B1 has opened
To handle this the send signal CS or CSLn from B2 is held back until the reverse zone IRVLn has
reset and the
protection shall be connected to input IRV and the output IRVL shall be connected to input BLKCS
on the communication function block ZCPSCH.
The function can be blocked by activating the input IRVBLK or the general BLOCK input.
15.2.2.2 Weak-end infeed logic
Permissive communication schemes can only operate when the protection in the remote IED can
detect the fault. The detection requires a sufficient minimum fault current, normally >20% of . The
fault current can be too low due to an open breaker or low short-circuit power of the source. To
overcome these conditions, weak-end infeed (WEI) echo logic is used. The fault current can also be
initially too low due to the fault current distribution. Here, the fault current increases when the
breaker opens at the strong terminal, and a sequential tripping is achieved. This requires a
detection of the fault by an independent tripping zone 1. To avoid sequential tripping as
described, and when zone 1 is not available, weak-end infeed tripping logic is used. The weak end
infeed function only works together with permissive overreach communication schemes as the
carrier send signal must cover the complete line length.
The WEI function sends back (echoes) the received signal under the condition that no fault has
been detected on the weak-end by different fault detection elements (distance protection in
forward and reverse direction).
Also, the WEI function can be additionally extended to trip the breaker in the weak side. The trip is
achieved when one or more phase voltages are low during an echo function.
In case of single-pole tripping, the phase voltages are used as phase selectors together with the
received signal CRLn.
When used with the blocking teleprotection scheme some limitations apply:
• Only the trip part of the function can be used together with the blocking scheme. It is not
possible to use the echo function to send the echo signal to the remote line IED. The echo
signal would block the operation of the distance protection at the remote line end and in this
way prevents the correct operation of a complete protection scheme.
• A separate direct intertrip channel must be arranged from the remote end when a trip or
accelerated trip is given there. The intertrip receive signal is connect to input CRL.
• The WEI function shall be set to
selection and trip the local breaker.
Bay control REC670
Application manual
CLOSED
LINE 1
A:1
A
CLOSED
LINE 2
A:2
tDelayRev time has been elapsed. To achieve this the reverse zone on the distance
© Copyright 2017 ABB. All rights reserved
FAULT OPEN
Weak
source
B:1
B
CLOSED
B:2
en99000044_ansi.vsd
WEI=Echo&Trip . The WEI function block will then give phase
Section 15
Scheme communication
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