Toshiba GRZ100 B Series, Instruction Manual, Page: 106 / 447

⎯
105
⎯
6 F 2 S 0 8 4 6
A decision to operate is made 6 times in each power frequency cycle using the above-mentioned
equation. The reactance element operates when two consecutive measurements are made if the
distance to a fault is within 90% of the reach setting. If the distance to a fault is more than 90%, the
reactance element operates when four consecutive measurements are made.
This decision method prevents transient overreaching occurring for faults close to the element
boundary.
Figure 2.5.1.8 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 2.5.1.9, 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
θ
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 2.5.1.9 Blinder element
(b) Z2 and ZF
X
R
90
°
(a) Z1 and Z1X
θ
2
R
θ
1
X