Toshiba GR200 Series Instruction Manual page 54

2.1-8. The operating area (Figure 2.1-8.a) is enclosed with forward blinders (BFR and BFL
lines); the BFL line is placed as the mirror image of the BFR line. Similarly, the operating area
(Figure 2.1-8.b) is enclosed with the reverse blinders (BRR and BRL lines).
X
BFL blinder
X
o
a. Forward blinder
The characteristics about the BFR and BRR lines are obtained by Equations (2.1-25) and
Equation (2.1-26), respectively:
where,
R = resistance component of measured impedance
X = reactance component of measured impedance
Rs = reach setting
If the minimum load impedance (Z Lmin ) is predictable, we can take the Rs setting for
the worst case such that the load angle is of 30° and the margin is of 80% in case of θ=75°;
Equation (2.1-27) can be applied to obtain the resistive setting for the blinder element:
Rs < 0.8 × Z
Element equations for directional characteristic
(v)
Figure 2.1-9 illustrates that a directional element used for the element in Quadrilateral
characteristic. The characteristic of the directional element is obtained using Equation
(2.1-28); the polarizing voltage (Vp) is the same one as employed in the Mho characteristic.
where,
I = fault current
Vp = polarizing voltage
�� = lagging angle of I to Vp
θ = directional angle setting
BFR blinder
θ
R
BRR blinder
Rs
R
Figure 2.1-8 Blinder elements
X ≥ ( R − R ) tan ��
s
X ≤ ( R + R ) tan ��
s
× (cos 30° −
Lmin
I × Vp cos ( �� − �� ) ≥ 0
- 33 -
X
R
Rs
o
θ
X
b. Reverse blinder
sin 30°
)
tan 75°
6F2S1915 (0.46)
R
BRL blinder
(2.1-25)
(2.1-26)
(2.1-27)
(2.1-28)
GRZ200 (Soft 031 & 032)
BRR
BRL