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Phase difference calculation
|V|•|I|cos(−) 0
Amplitude calculation
|Vpol| Set voltage (OV-Vpol)
Output of
directional element
Amplitude calculation
|l| OC pickup current
Figure 2.15-3 Direction determination after loss of voltage memory
If a single phase is connected to a heavy load, and the other phases are not connected to
heavy loads, the user can program separately the directional OC element such that OC will
send a trip signal only when the fault current detected is in the same direction among two
phases or more of the three-phases.
A setting and a scheme switch, as well as the non-directional OC element, provide the
settings for the directional OC element: for example, the user can set the threshold value of
the OC at stage 1 with the setting [OC1] and Forward can be set for the scheme switch [OC1-
Dir]. Setting of the sensing angle (θ) is configured by the setting [OC1-Angle] with the value of
θ set in the range of 0–180°. Figure 2.15-4 shows an example of an angle and a characteristic
set with θ.
Figure 2.15-4 Examples of directional characteristic angle (θ)
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