GE D90 Plus - Page 651

CHAPTER 15: THEORY OF OPERATION DISTANCE ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 641
Table 20: Mho phase AB element conditions
The results are shown in the following table.
Table 21: Mho phase AB element analysis
The mho difference angle comparator is not satisfied. Therefore, the mho phase AB
element does not operate for this fault.
Quadrilateral phase A to ground element analysis, before memory expires
Before the memory expires, the following values are calculated for the quadrilateral phase
A to ground distance element:
Eq. 76
The ground distance element checks for the following conditions for overcurrent
supervision and the difference angles.
Table 22: Quadrilateral phase A to ground element conditions
Parameter Condition
Overcurrent supervision | (I
A
– I
B
) / √3 | > Supervision
Mho difference angle | ∠((I
A
– I
B
) × Z – (V
A
– V
B
)) – ∠((V
A
– V
B
)_1M) | < Comparator Limit
Reactance difference angle | ∠((I
A
– I
B
) × Z – (V
A
– V
B
)) – ∠((I
A
– I
B
) × Z) | < Comparator Limit
Directional difference angle | ∠((I
A
– I
B
) × Z) – ∠((V
A
– V
B
)_1M) | < Directional Comparator Limit
Parameter Calculation Requirement Condition met
Overcurrent supervision | (7.39 A) / √3 | = 4.27 A > 3 A Yes
Mho difference angle | –78.7° –30.0° | = 108.7° < 75° No
Reactance difference angle | –78.7° – (–21.2°) | = 57.5° < 75° Yes
Directional difference angle | –21.2° – 30.0° | = 51.2° < 75° Yes
Parameter Condition
Overcurrent supervision 3 × I_0 >
Supervision
Reactance difference angle | ∠(I
A
× Z + I_0 × K
0
× Z + I
G
× K
0M
× Z – V
A
) – ∠(j × I_0 × e
j3
) | <
Comparator Limit
Zero-sequence directional
difference angle
| ∠( I_0 × Z
D
) – ∠(V
A
_1M) | < Directional Comparator Limit
Negative-sequence directional
difference angle
| ∠( I
A
_2 × Z
D
) – ∠(V
A
_1M) | < Directional Comparator Limit
Right blinder difference angle | ∠(I
A
× Z
R
+ I_0 × K
0
× Z
R
+ I
G
× K
0M
× Z
R
– V
A
) – ∠(I
A
× Z
R
+ I_0 × K
0
×
Z
R
) | < 90°
Left blinder difference angle | ∠(I
A
× Z
L
+ I_0 × K
0
× Z
L
+ I
G
× K
0M
× Z
L
– V
A
) – ∠(I
A
× Z
L
+ I_0 × K
0
×
Z
L
) | < 90°
Fault type comparator
difference angle
| ∠( I
A
_2 × Z
D
) – ∠(I_0 × Z
D
) | < 50°
,= = =
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