Toshiba GR200 Series Instruction Manual page 122

end, the reactance characteristic will be a horizontal line, which is parallel to the R-axis. The
horizontal characteristic is taken when no load current flowing; it is also taken when the θ1
angle is set to zero (0). The level element in the reactance characteristic is shown using
Equation (2.10-21); the element in the gradual descent characteristic is shown in Equation
(2.10-22):
× tan ( 90° − ��2 ) + ( X
R ≤ X
S
where,
R = resistance component of measured impedance
X = reactance component of measured impedance
Xs = reach setting
The R and X components are calculated using an integration approximation algorithm.
Using the reactance characteristic, the relay is able to have high measurement accuracy even
in the presence of frequency fluctuations in the power system and distorted transient
waveforms containing low-frequency spectral components.
The values of the θ1 and θ2 are obtained using Equations (2.10-23) and (2.10-24):
θ1 < tan
where,
X = reactance component
RF = fault resistance
I Lmax = maximum load current
I Fmin = minimum fault current
To commence the element of the distance relay (Z) in accompany with the reactance
characteristic, a fault recognition is executed every one-sixth of a power-cycle (system
frequency), using Equations (2.10-21) and (2.10-22). The Z relay shall operate if two fault
recognitions are obtained consecutively in a power-cycle, if the fault occurs within 90% of the
reach setting (Zs). If the fault is beyond the 90% of the Zs, the Z relay shall operate when four
fault are recognized consecutively in a power-cycle. Six-times-fault-recognitions in a power
cycle can prevent an erroneous operation in the transient phenomena; that is, the means of
the six-times-fault-recognitions to avoid overreach results when a fault occurs close to the
boundary of two zones (e.g., a boundary of the Z1 and Z2 relay elements).
X ≤ X
S
− X ) tan ( 90° − ��1 )
S
( X R
−1
θ2 < tan ⁄ )
F
I
−1
Lmax
( ⁄
( I
+I
Lmax Fmin
- 99 -
)
)
6F2S1914 (0.49)
(2.10-21)
(2.10-22)
(2.10-23)
(2.10-24)
GRL200 (Soft 033 & 037)