Toshiba GRZ100-211B, Instruction Manual

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121
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6 F 2 S 0 8 3 4
R
θ
X
ZB
Figure 2.6.1.12 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)
2.6.2 Phase Selection Element UVC
The phase selection element has the undervoltage characteristic shown in Figure 2.6.2.1 and is
used to select a faulty phase in case of a single-phase-to-earth fault.
I
V
Vs
IZs
θ
Figure 2.6.2.1 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)
where,
V = fault voltage
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