REG 316*4 1MRB520049-Uen / Rev. F ABB Switzerland Ltd
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3.7.2. Three-phase current plausibility (Check-I3ph)
A. Application
Checking the plausibility of the three-phase current inputs for
· monitoring the symmetry of the three-phase system
· detection of a residual current
· supervision of the c.t. input channels.
B. Features
· evaluation of
· the sum of the three phase currents
· the sequence of the three phase currents
· provision for comparing the sum of the three phase currents
with a residual current I/P
· adjustment of residual current amplitude
· blocking at high currents (higher than 2 x I
N
)
· blocking of phase-sequence monitoring at low currents
(below 0.05 x I
N
)
· insensitive to DC components
· insensitive to harmonics.
C. Inputs and outputs
I. C.t./v.t. inputs:
· phase currents
· neutral current (optional)
II. Binary inputs:
· blocking
III. Binary outputs:
· tripping
IV. Measurements:
· difference between the vector sum of the three phase
currents and the neutral current.
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