GE BUS1000, Инструкция по эксплуатации

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3. OPERATION PRINCIPLES
GEK-98514B BUS1000 Busbar Protection 3-3
Where:
V
D
= RMS voltage in the differential circuit.
V
F
= RMS voltage in the restraint circuit.
V
O
= Threshold voltage in the level detector.
I
D
= RMS current in the differential circuit.
I
F
= RMS current in the restraint circuit.
K= Restraint percent in unit value.
T= Detector time (in ms.).
We will have the following values’ ratio:
On the other hand, the differential unit will produce an output when the VA value is above the V
O
one, that is,
when:
or what is the same when:
The circuit design values are:
V
o
= 0.137 V
T = 1.5 ms.
N = 0.01
R = 100
ÿ
With these values the equation is reduced to:
For an internal fault I
D
= I
F
, so:
From this equation we obtain the relay's sensitivity in amperes for the different values of K.
R N I R N I V
D D ED D D
* * * *
= =
R N I R N I V
F F EF F F
* * * *
= =
O F D
V T V K V
≥ − −
) 9 90 sen( * ) * ( * 2
[5]
[6]
1 . 0 *
≥ −
F D
I K I [7]
) 1 /( 1 . 0 K I
D
− ≥
[8]
) * 1 ( * )) 9 90 sen( * 2 / 1 ( * * R N T V I K I
O F D
− ≥ −