Description
Inverse time overfluxing (U/f-Inv)
A. Application
Protection of generators and power transformers against excessive flux.
B. Features
evaluation of the voltage/frequency ratio
single-phase measurement
inverse time delay according to U/f ratio
determination of frequency from the complex voltage vector
insensitive to DC components
insensitive to harmonics
determination of delay by integration
input of delay table facilitates matching the operating characteristic to a specific machine according to IEEE Guide
C 37.91-1985.
adjustable rate of counting backwards when the overfluxing
disappears.
C. Inputs and outputs
I. C.t/v.t. inputs:
voltage
II. Binary inputs:
Blocking
III. Binary outputs:
pick-up
tripping
IV. Measurements:
voltage/frequency
frequency.