ABB RED650, Applications Manual

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L1
L2
A1
A2
B1
B2
IEC99000044-2.vsd
IEC99000044 V3 EN-US
Figure 123: 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
tDelayRev time has been elapsed. To achieve this the
reverse zone on the distance 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.
13.2.2.2 Weak-end infeed logic
M13895-16 v8
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 I
r
. 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
Section 13
1MRK 505 393-UEN B
Scheme communication
286 Line differential protection RED650 2.2 IEC
Application manual