GE D90 Plus Instruction Manual page 621

CHAPTER 15: THEORY OF OPERATION
NOTE:
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 541: Applications of the phase distance transformer settings
In the following tables, the suffix "_21P" indicates current or voltage inputs to the phase
distance (ANSI 21P) element.
Table 24: Phase distance input signals for delta-wye transformers
Transformer Loop
connection
None AB
BC
CA
Dy1 AB
BC
CA
Dy3 AB
BC
CA
PHASE DISTANCE APPLIED TO POWER TRANSFORMERS
Current transformation
I = I - I
_21P
AB A B
I = I - I
_21P
AB A B
I = I - I
_21P
CA C A
I _21P = I
3
A A
I _21P = I
3
B B
I _21P = I
3
C C
I _21P - = I
3
AB C
I _21P - = I
3
BC A
I _21P - = I
3
CA B
Voltage transformation
V = V
_21P
AB AB
V = V
_21P
BC BC
V = V
_21P
CA CA
1
( )
V = V - V
_21P
AB AB CA
3
1
( )
V = V - V
_21P
BC BC AB
3
1
( )
V = V - V
_21P
CA CA BC
3
1
( )
V = V - V
_21P
AB BC CA
3
1
V = ( V - V )
_21P
BC CA AB
3
1
( )
V = V - V
_21P
CA AB BC
3
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