GE BUS1000, Instructions Manual

Page: 17 / 129

3. OPERATION PRINCIPLES
GEK-98514B BUS1000 Busbar Protection 3-5
3.3. SENSITIVITY EQUATION OF THE PERCENT RESTRAINT UNIT
From fig. 4 we may draw out the following equations.
From (1) and (2) we have:
We find that the unit will produce an output (operate) when:
So:
In the same way the unit does not operate when:
For more security we can say that the unit will not trip if:
OR
Thus:
From this we can finally deduce that:
X FAULT D
I I I
− =
MAX X E D
R I R I * *
=
[10]
[9]
)) / ( 1 ( *
) / ( *
MAX E D
MAX E D D FAULT
R R I
R R I I I
+ =
= + =
) / ( * )) / ( 1 ( *
MAX E D MAX E D X FAULT F
R R I R R I I I I
+ + = + =
)) / ( * 2 1 ( *
MAX E D F
R R I I
+ =
[11]
[13]
[12]
1 . 0 *
≥ −
F D
I K I
)) / ( * 2 1 ( * *
MAX E D D
R R I K I
+ ≥
1 . 0 ))) / ( * 2 1 ( * 1 ( *
≥ + −
MAX E D
R R K I
[14]
[15]
1 . 0 ))) / ( * 2 1 ( * 1 ( *
< + −
MAX E D
R R K I [16]
0 ))) / ( * 2 1 ( * 1 ( *
< + −
MAX E D
R R K I
0 )) / ( * 2 1 ( * 1
< + −
MAX E
R R K
)) / ( * 2 1 ( * 1
MAX E
R R K
+ <
E MAX MAX
R K R K R * * 2 *
+ <
[17]
[18]
[19]
K
R K
R
E
MAX
−
<
1
* * 2
[20]
K K R R
MAX E
2 / ) 1 ( *
− >