GE D60 Instruction Manual page 356

8.2 PHASE DISTANCE APPLIED TO POWER TRANSFORMERS
If applied at location H, the relay sees the following input signals:
INPUT PRIMARY
7.584 kV ∠–5.59°
VA
VB 6.269 kV ∠–120.1°
VC 7.751 kV ∠125.5°
IA 16.976 kA ∠–27.6°
33.952 kA ∠152.4°
IB
16.976 kA ∠–27.6°
IC
The relay is set as follows:
XFMR VOL CONNECTION
XFMR CUR CONNECTION
Consequently, the following signals are applied to the phase AB distance element:
V
=
I
This results in the following apparent impedance:
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.
8
8-14
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°
= "Dy11"
= "Dy11"
1
------ - V V 10.861 kV 59.9° primary or 94.45 V 59.9° secondary ∠
– =
AB BC
3
3I 58.860 kA ∠ 27.6° primary or 36.75 A
= – = –
B
∠
V 94.45 kV 59.9°
Z --- - --------------------------------------------- -
= =
app
∠
I 36.75 kA 27.6
–
10
( ) --------- -
Z at 13.8 kV
=
T
100
( )
Z at 13.8 kV 30.11
=
L
∠
D60 Line Distance Relay
∠
∠ 27.6° secondary
–
2.570 Ω 87.5° ∠
secondary
=
°
2
( )
13.8 kV
× --------------------------- - ∠
0.127Ω 90°
=
150 MVA
2
13.8
⎛ ⎞
× ---------- - ∠
0.05779Ω 85°
=
⎝ ⎠
315
88.4° primary side or 2.569 Ω ∠88.4° on the secondary side.
8 THEORY OF OPERATION
(EQ 8.1)
(EQ 8.2)
(EQ 8.3)
(EQ 8.4)
GE Multilin