118
6
F
2
S
0
8
3
4
reactance element operates when four consecutive measurements are made.
This decision method prevents transient overreaching occurring for faults close to the element
boundary.
Figure 2.6.1.8 Reactance Element
The setting of
θ
1(Z1
θ
1) and
θ
2(Z1
θ
2) are set to the following:
Z1
θ
2 < tan
-1
( X / R
F
)
Where,
X = reactance component
R
F
= fault resistance
Z1
θ
1 < tan
-1
{I
Lmax
/ (I
Lmax
+ I
Fmin
)}
I
Lmax
= maximum load current
I
Fmin
= minimum fault current
Blinder element
The blinder element is commonly applicable to Z1, Z1X, Z2, ZF, Z3, ZR1, ZR2 and Z4. As shown
in Figure 2.6.1.9, the blinder element provides the forward blinder and the reverse blinder. The
operating area of the forward blinder is the zone enclosed by the lines BFR and BFL, and that of
the reverse blinder is the zone enclosed by the lines BRR and BRL. The BFR has an angle of 75
°
to the R-axis and BFL 90
°
to 135
°
. The angle of BRL is linked with that of BFL.
(a) Forward blinder
(b) Reverse blinder
BRL
R
X
-Rs
θ
75
°
BRR
X
R
θ
75
°
BFR
BFL
R
Rs
X
Rs
Figure 2.6.1.9 Blinder element
The characteristic of the BFR is obtained by the following equation.
X
≥
(R
−
Rs) tan 75
°
where,
(b) Z2 and ZF
X
R
90
°
(a) Z1 and Z1X
θ
2
R
θ
1
X
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Summary of Contents for GRZ100-211B
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