Example - GE D30 Instruction Manual

8 THEORY OF OPERATION
Equations from the "Current Transformation" and "Voltage Transformation" columns are used to derive inputs to the three
(AB, BC, and CA) phase distance elements. For example, if the CTs are located at the delta side of the Delta-Wye 11 trans-
former, and a given zone is set to look through the transformer into the system connected to the Wye winding, the CT loca-
tion setting for that zone shall be set to Dy11 and the relay would use
phase distance element.
The current supervision pickup setting applies to the currents specified in the "Current Transformation" columns.
A distance zone originates at the location of the VTs (regardless of the location of the CTs). For more information on set-
tings please refer to Chapter 9: Application of Settings.
Consider the system shown below:
Normally, in order to respond to the fault shown in the figure, a distance relay shall be applied at the relaying point X. The
relay input signals at this location are shown in the following table.
INPUT PRIMARY
100.4 kV ∠–7.32°
VA
97.23 kV ∠–53.4°
VB
181.8 kV ∠–150.0°
VC
IA 1.288 kA ∠–27.6°
IB 1.288 kA ∠152.4°
IC 0
If installed at the location X, the relay would use the following input signals for its phase AB distance element:
= 77.402 kV ∠57.5° primary or 29.49 V ∠57.5° secondary
V = V
AB
= 2.576 kA ∠–27.6° primary or 42.93 A ∠–27.6° secondary
I = I – I
A B
And consequently it would see an apparent impedance of:
Z = V / I = 30.05 Ω ∠85° primary or 0.687 Ω ∠85° secondary
app
GE Multilin
8.2 PHASE DISTANCE APPLIED TO POWER TRANSFORMERS
150 MVA, 10%
13.8kV/315kV
delta wye, 330 lag
H X
VT = 13.8kV/120V VT = 315kV/120V
CT = 8000:5 CT = 300:5
2.57Ω∠88.4°
Figure 8–5: SAMPLE SYSTEM CONFIGURATION
SECONDARY
38.25 V ∠–7.32°
37.04 V ∠–53.4°
69.26 V ∠–150.0°
21.47 A ∠–27.6°
21.47 A ∠152.4°
0
D30 Line Distance Relay
3I instead of a traditional
–
B
°
AB
Z = 30.11 Ω∠ 85°
L
Ω∠
0.688 85°
837727A2.CDR
I I for the AB
–
A B
8

8.2.2 EXAMPLE

8-13