ABB REL670 2.2 IEC - Page 252

I
E
earth current of faulty line
K
N
is earth compensation factor for single circuit set at the relay given
by equation
0 1
1
3
N
Z Z
K
Z
=
-
×
IECEQUATION14005 V1 EN-US (Equation 159)
The short circuit voltage can be calculated as:
0 1 0 0 1 0
1 1
1 1
( )
3 3 3 3
m m
ph ph E Ep ph E Ep
I
Z Z Z Z Z Z
U Z I I Z I I I
Z Z
=
- -
× + × + × = + × + ×
IECEQUATION14006 V1 EN-US (Equation 160)
Where I
Ep
is the ground current in the parallel line.
As explained above, the distance relay phase-to-earth measures:
ph
ph N E
Z
U
I K I
=
+ ×
IECEQUATION14004 V1 EN-US (Equation 161)
0 1 0
1 1
1
3 3
m
ph E Ep
ph
ph n E ph n E
Z
Z Z Z
I I I
U
Z Z
Z
I K I I K I
=
-
+ × + ×
= ×
+ × + ×
IECEQUATION14007 V1 EN-US (Equation 162)
Taking earth compensation factor
0 1
1
3
N
Z Z
K
Z
-
=
for single circuit and
0
1
3
m
Nm
Z
K
Z
=
impedance measured by distance relay can be written as:
1
1
Nm Ep
ph N E
Z Z
K I
I K I
=
é ù
×
+
ê ú
+ ×
ê ú
ë û
IECEQUATION14010 V1 EN-US (Equation 163)
Where:
I
E
earth current of faulty line
I
EP
is earth current of the parallel line
Z
1
is line positive sequence impedance
Table continues on next page
Section 8 1MRK 506 369-UEN B
Impedance protection
246 Line distance protection REL670 2.2 IEC
Application manual