Example - GE D30 Instruction Manual

PHASE DISTANCE APPLIED TO POWER TRANSFORMERS
Transformer
connection
Yd5
Yd7
Yd9
Yd11
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
transformer, and a given zone is set to look through the transformer into the system connected to the Wye winding, the CT
location setting for that zone is set to Dy11 and the relay uses
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 information on settings see
the Application of Settings chapter.

9.2.2 Example

Consider the system shown.
9
9-14
Loop Current transformation
AB
1
I = ----- - 2I (
AB_21P B
3
BC
1
I = ----- - 2I (
BC_21P C
3
CA
1
(
I = ----- - 2I
CA_21P A
3
AB
1
I = ----- - I (
AB_21P B
3
BC
1
I = ----- - I (
BC_21P A
3
CA
1
(
I = ----- - I
CA_21P A
3
AB
1
I = ----- - 2I (
AB_21P C
3
BC
1
I = ----- - 2I (
BC_21P A
3
CA
1
I = ----- - 2I (
CA_21P B
3
AB
1
I = ----- - I (
AB_21P A
3
BC
1
I = ----- - I (
BC_21P A
3
CA
1
I = ----- - I (
CA_21P B
3
Voltage transformation
V = 3V
AB_21P
I I )
– –
A C
V = 3V
BC_21P
I I )
– –
A B
V = 3V
CA_21P
)
I I
– –
B C
V =
–
AB_21P
+ I 2I )
–
C A
V =
–
BC_21P
+ I 2I )
–
C B
V =
–
CA_21P
)
+ I 2I
–
B C
V = 3V
AB_21P
I I )
– –
A B
V = 3V
BC_21P
I I )
– –
B C
V = 3V
CA_21P
I I )
– –
A C
V =
–
AB_21P
+ I 2I )
–
C B
V =
–
BC_21P
+ I 2I )
–
B C
V =
–
CA_21P
+ I 2I )
–
C A
instead of a traditional
3I
–
B
D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 9: THEORY OF OPERATION
B
C
A
3V
A
3V
B
3V
C
C
A
B
3V
B
3V
C
3V
A
for the AB phase
I I
–
A B