REG 316*4 1MRB520049-Uen / Rev. F ABB Switzerland Ltd
3-153
3.5.14. Underreactance (MinReactance)
A. Application
· detection of inadmissible operating conditions due to under-
excitation of a synchronous generator.
B. Features
· circular operating characteristic (see Fig. 3.5.14.1)
· selectable to operate inside or outside the circle
· adjustable size and position of the operating characteristic
· correction of phase errors caused by input circuit
· adjustable time delay
· insensitive to DC component in voltage and current
· insensitive to harmonics in voltage and current
· single or three-phase measurement
· detection of the lowest impedance (distance from the centre
of the circle)
· underreactance measurement enabled by undercurrent unit
(0.1 I
N
).
C. Inputs and outputs
I. Analogue inputs:
· current
· voltage
II. Binary inputs:
· blocking
III. Binary outputs:
·
pick-up
· tripping
IV. Measurements:
· impedance (distance from the centre of the circle).
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