Calculating Setting For Current Reversal And Weak End Infeed Logic For Distance Protection Zcrwpsch (85) - ABB REL650 Applications Manual

Section 3
REL650 setting examples
3.1.7
64
The trip signal from zone2 in this case need not be delayed except in case where the
transmission channel is slow.
Calculating setting for current reversal and weak end infeed
logic for distance protection ZCRWPSCH (85)
The distance protection can only operate if the fault current fed to the protection is larger
than 10 – 30 % of the rated current (settable). There is a risk that the fault current infeed
from one of the line ends is very small, but not zero. In such case the following can be the
consequence of a short circuit close to the line end with small fault current infeed.
Zone 4 ( reverse )
Weak End
A
REL 650
Y
ANSI11000113 V1 EN
Figure 20: Line fault for fast fault clearance by means of WEI logic
For the fault shown in the figure
if the WEI logic is not used:
• Zone 1 in the line end A (weak end) will not start due to the small fault current infeed.
This means that the line breaker will not open.
• The fault detection in line end B will be done by means of zone 2 distance protection
function. As there will be no acceleration signal (CR) from line end A, the
communication scheme cannot be activated. The fault clearance will thus be delayed
(zone 2 time delay).
To overcome this shortcoming of the protection scheme the weak end infeed logic (WEI)
is activated.
The function at internal line fault can be described as:
Zone 2
Zone 1
Z 1 = R 1 + jX 1
Z 0 = R 0 + jX0
Communication
Zone 1
Zone 2
20 there is a risk that we get the following consequences
1MRK 506 334-UUS A
B
REL 650
C
Y
Zone 4 ( reverse )
ANSI11000113_1_en.vsd
Application manual