GE D90 Plus, Instruction Manual

Page: 651 / 694

CHAPTER 15: THEORY OF OPERATION THE D90
Plus
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 will 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
0 M
× Z – V
A
) –
∠
( j × I _0 × e
j 3
) | <
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
0 M
× 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
0 M
× 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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