Toshiba GRL100-701B Instruction Manual page 139

Reactance element
The reactance element of Z1 has a composite characteristic with the two straight lines, one is
parallel and the other is gradual descent toward the R-axis as shown in Figure 2.16.3.8.
The characteristic is defined by the reach setting Xs and the angle settings θ1 and θ2. This
composite characteristic is obtained only when the load current is transmitted from local to remote
terminal. When the load current flows from remote to local terminal or the load current does not
flow or θ1 is set to 0°, the reactance element characteristic is a horizontal line which is parallel to
the R-axis.
The characteristic is expressed by the following equations.
For horizontal characteristic
X ≤ Xs
For gradient characteristic
R ≤ Xs tan ( 90° − θ2 ) + ( Xs − X ) tan ( 90° − θ1 )
where,
R = resistance component of measured impedance
X = reactance component of measured impedance
Xs = reach setting
The reactance element characteristic of Z2 and ZR is given by a parallel line to the R axis.
R and X are calculated using an integration approximation algorithm. The reactance element
provides high measurement accuracy even in the presence of power system frequency fluctuations
and distorted transient waveforms containing low-frequency spectral components.
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.
X
IZs
V
−IZso
S2 = V + IZso
Figure 2.16.3.7 Offset Mho Element
 138 
6 F 2 S 0 8 5 0
S1 = V − IZs
R