142
6
F
2
S
0
8
5
0
Figure 2.16.3.12 Offset Directional Element
The characteristic of the offset directional element is obtained by the following equation.
X + R tan
θ
≦
Z
B
where,
X = reactance component of measured impedance
R = resistance component of measured impedance
θ
= directional angle setting (interlinked with directional element angle setting)
Z
B
= offset reach setting (fixed to 1.5
Ω
in 5A rating and 7.5
Ω
in 1A rating)
2.16.4 Phase Selection Element UVC
The phase selection element has the undervoltage characteristic shown in Figure 2.16.4.1 and is
used to select a faulty phase in case of a single-phase-to-earth fault.
I
V
Vs
IZs
θ
Figure 2.16.4.1 Phase Selection Element
The characteristic is obtained by a combination of the equations below. If equation (1) or equation
(2), or both equations (3) and (4) are established, the UVC operates.
|V|
≤
Vs
(1)
|V
−
IZs|
≤
Vs
(2)
−
Vs
≤
V sin
θ
≤
Vs
(3)
0
≤
V cos
θ
≤
|IZs|
(4)
R
θ
X
ZB
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Summary of Contents for GRL100-701B
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