GE G60 Instruction Manual page 295

8 THEORY OF OPERATION
If applied at location H, the relay sees the following input signals:
INPUT PRIMARY
7.584 kV ∠–5.59°
VA
6.269 kV ∠–120.1°
VB
7.751 kV ∠125.5°
VC
16.976 kA ∠–27.6°
IA
33.952 kA ∠152.4°
IB
16.976 kA ∠–27.6°
IC
The relay is set as follows:
= "Dy11"
XFMR VOL CONNECTION
= "Dy11"
XFMR CUR CONNECTION
Consequently, the following signals are applied to the phase AB distance element:
1
V ------ - V
=
AB
3
I 3I
= –
This results in the following apparent impedance:
Z
app
The above value is a correct measure of the distance from the VT location to the fault. For relay location 2, this certainly
includes the positive-sequence impedance of the transformer:
Thus, 0.127 Ω ∠90° + 0.05779 Ω ∠85° = 0.1847 Ω
The above example illustrates how the relay maintains correct reach for fault behind power transformers. When installed at
X, the relay shall be set to 0.687 Ω ∠85° secondary in order to reach to the fault shown in the figure. When installed at H,
the relay shall be set to 2.569 Ω ∠88.4° to ensure exactly same coverage.
See Chapter 9: Application of Settings for more information on setting calculations.
GE Multilin
8.1 PHASE DISTANCE THROUGH POWER TRANSFORMERS
SECONDARY
69.95 V ∠–5.59°
54.52 V ∠–120.1°
65.84 V ∠125.5°
10.61 A ∠–27.6°
21.22 A ∠152.4°
10.61 A ∠–27.6°
∠
V 10.861 kV 59.9° primary or 94.45 V 59.9° secondary
– =
BC
∠
58.860 kA 27.6° primary or 36.75 A
= –
B
∠
V 94.45 kV 59.9°
--- - --------------------------------------------- -
= = =
∠ °
I 36.75 kA 27.6
–
(
10 13.8 kV
( ) ×
--------- - --------------------------- -
Z at 13.8 kV
=
T
100 150 MVA
13.8

( ) × ---------- -
Z at 13.8 kV 30.11
=

L
315
88.4° primary side or 2.569 Ω ∠88.4° on the secondary side.
∠
G60 Generator Management Relay
∠
∠
27.6° secondary
–
2.570 Ω 87.5° ∠
secondary
2
)
∠
0.127Ω 90°
=
2

∠
0.05779Ω 85°
=

(EQ 8.1)
(EQ 8.2)
(EQ 8.3)
(EQ 8.4)
8
8-5