Woodward
Manual MRI3 GB
20
DOK-TD-MRI3 Rev.A
Figure 4.4
Figure 4.5
Example:
Figure 4.4 and Figure 4.5 illustrate a possible fault situation with a reversal in direction in the fault-
free line. The current transformers used have a primary current of 250 A. The switch point for the I>
stage is 0.25 kA and for the I>> stage 1 kA. All devices have the same setting and will, if set to
“Forward”, recognize the direction in relation to the forward direction of the line. The critical point
here is the MRI3 No. 1. Using delay action in directional recognition, it is possible to prevent shut-
down of the fault-free line.
The following relay setting applies:
I>
1.00
x
In
CHAR I>
DEFT (inverse)
trip
delay
tI>(V)
10s
Trip delay in forward direction
tI>(R)
EXIT (no trip) Delay in backward direction
I>
4.00 x In
tI>>(V)
0.1
s
tI>>(R)
EXIT
MRI3
MRI3
MRI3
MRI3
G
I
K
= 0,3 kA
I
K
= 3,61 kA
I
K
= 0,9 kA
I
K
= 3,31 kA
I
K
= 1,2 kA
l = 3 km
l = 0,5 km
l = 3 km
No. 2
No. 4
No. 3
No. 1
MRI3
MRI3
MRI3
MRI3
G
I
K
= 1,2 kA
I
K
= 2,0 kA
I
K
= 1,2 kA
I
K
= 0,8 kA
l = 0,5 km
l = 3 km
l = 3 km
No. 1
No. 3
No. 2
No. 4