Toshiba GRL100-701B Instruction Manual page 141

R = resistance component of measured impedance
X = reactance component of measured impedance
Rs = reach setting
The characteristic BFL is obtained by the following equation. Polarizing voltage employed is the
same as employed for mho element.
Vp I cos ( φ + θ − 90° ) > 0
where,
Vp = polarizing voltage
I = fault current
φ = lagging angle of I to Vp
θ = angle setting
A blinder applicable to the offset mho element for the power swing blocking also has the same
characteristics as BFR.
The characteristics of BRR and BRL are expressed by the following equations.
For BRR
X ≤ (R + Rs) tan 75°
For BRL
X ≤ (R − Rs) tan (180° − θ)
where,
R = resistance component of measured impedance
X = reactance component of measured impedance
Rs = reach setting
The reach settings of BFR and BRR are made on the R-axis. The BRL setting is interlinked with
the BRR setting.
If the minimum load impedance is known, then assuming a worst case load angle of 30° and a
margin of 80%, then the following equation can be used to calculate the blinder element resistive
settings:
< 0.8 × Z × (cos30 −
R
set Lmin
Directional element
The directional element is used for the quadrilateral four zone characteristics.
sin30
tan75 )
Vp
θ
Figure 2.16.3.10 Directional Element
 140 
lag
I
6 F 2 S 0 8 5 0