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Setting of the sensing angle (θ) is configured by the setting [EF1-Angle] with the value of θ set
in the range of 0–180°. Figure 2.16-2 shows an example of an angle and a characteristic using
the θ. The operation of the EF element is based upon the following equation.
where
3Io = residual current
3Vo = residual voltage
−3Vo = reference voltage (or polarizing voltage)
φ= lagging angle
θ = EF setting angle
I
EF
= Setting value of the EF element ([EF1-DT] and the others)
EF_Vpol = Setting value of the polarizing voltage ([EF1-Vpol])
Note: In the case of an internal fault, the phase angle is equal to the angle of the zero-
sequence impedance of the system, in a directly-earthed system this value is in
the range of approximately 50° to 90°. The sensing angle θ of the EF element can
be set between 0° to 180°. The minimum voltage necessary to maintain
directionality can be set from 0.5 to 100.0 V.
Figure 2.16-2 Examples of directional characteristic angle (θ)
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