GE MiCOM P40 Agile Technical Manual page 197

Application Notes
MiCOM P40 Agile P442, P444
residual current on the parallel line is measured. It is extremely important that the polarity of
connection for the mutual CT input is correct, as shown.
The system assumed for the distance protection worked example will be used here, refer to
section 3.3. The Green Valley – Blue River line is considered.
Line length: 100 km
CT ratio:
VT ratio:
Line impedances:
Ratio of secondary to primary impedance =
Line Impedance
Relay Line Angle settings 0° to 360° in 1° steps. Therefore, select Line Angle = 80° for
convenience.
Therefore set Line Impedance and Line Angle: = 5.81 / 80° Ω (secondary).
No residual compensation needs to be set for the fault locator, as the relay automatically
uses the kZ0 factor applicable to the distance zone which tripped.
Should a CT residual input be available for the parallel line, mutual compensation could be
set as follows:
kZm Mutual Comp,
kZm Angle,
The CT ratio for the mutual compensation may be different from the Line CT ratio. However,
for this example we will assume that they are identical.
Therefore set
1 200 / 5
230 000 / 115
0.089 + j0.476 = 0.484 / 79.4° Ω/km
Z =
1
0.107 + j0.571 = 0.581 / 79.4° Ω/km
ZM =
0
230000 /115
= 100 x 0.484 / 79.4° x 0.12
5.81 / 79.4° Ω secondary.
=
kZm =
ZM / 3.Z
0
∠kZm = ∠ ZM
/ 3.Z
0
kZm = ZM / 3.Z
0
kZm Mutual Comp
kZm Angle
1200 / 5
= 0.12
Ie: As a ratio.
1
Set in degrees.
1
= 0.581 / 79.4° / (3 x 0.484 / 79.4°)
1
= 0.40 / 0°
= 0.40
= 0°
P44x/EN AP/Hb6
(AP) 5-45
(Mutual)