Toshiba GR200 Series Instruction Manual page 53

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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 (2.1-21); the element in the gradual descent characteristic is shown in Equation

× tan ( 90° − ��2 ) + ( X

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 (2.1-23) and (2.1-24):

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 (2.1-21) and (2.1-22). 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).

Element equations for blinder characteristic

The characteristics about the forward and the reverse blinders are provided as shown in Figure

− X ) tan ( 90° − ��1 )

6F2S1915 (0.46)

GRZ200 (Soft 031 & 032)