ABB REL670 2.2 IEC, Applications Manual

Page: 342 / 908

8.12.2.2 Fault infeed from remote end
GUID-E28CCC52-497F-4B79-9430-8A2155FED936 v4
All transmission and most all sub-transmission networks are operated meshed.
Typical for this type of network is that fault infeed from remote end will happen
when fault occurs on the protected line. The fault current infeed will enlarge the
fault impedance seen by the distance protection. This effect is very important to
keep in mind when both planning the protection system and making the settings.
With reference to figure 171 , the equation for the bus voltage U
A
at A side is:
U I p Z I I Rf
A A L A B
= ⋅ ⋅ + +
( )
⋅
EQUATION1273-IEC-650 V2 EN-US
(Equation 292)
If we divide U
A
by I
A
we get Z present to the IED at A side.
I
A
+ I
B
U
A
I
A
I
A
Z
A
= = p ·Z
L
+ ·R
f
EQUATION1274-IEC-650 V1 EN-US
(Equation 293)
The infeed factor (I
A
+I
B
)/I
A
can be very high, 10-20 depending on the differences
in source impedances at local and remote end.
Z <
ZL
Z <
E
SA
U
A
U
B
A
B
E
SB
I
A
I
B
R
f
p*ZL
(1-p)*ZL
Z
SA
Z
SB
IEC09000247-1-en.vsd
IEC09000247 V1 EN-US
Figure 171: Influence of fault current infeed from remote line end
The effect of fault current infeed from the remote line end is one of the most
driving factors to justify complementary protection for distance protection.
When the line is heavily loaded, the distance protection at the exporting end will
have a tendency to overreach. To handle this phenomenon, the IED has an adaptive
built-in algorithm, which compensates the overreach tendency of zone 1 at the
exporting end. No settings are required for this feature.
Section 8
1MRK 506 369-UEN B
Impedance protection
336 Line distance protection REL670 2.2 IEC
Application manual