Digital integrator V/Hz relay for generator and transformer over

Details Digital integrator V/Hz relay for generator and transformer over Digital integrator V/Hz relay for generator and transformer over

1996-05-13

1997-09-23

Gaffin, Jeffrey A.

Electricity: electrical systems and devices

Safety and protection of systems and devices

With specific quantity comparison means

322 11, 322 23, 322 36, 364483, 364484, 364494, H02H 318

Patent

active

056711123

ABSTRACT:
A system for implementing accurate V/Hz value measurement and trip time determination for generator/transformer overexcitation protection independent of the conventional frequency tracking and phasor estimation based on Discrete Fourier Transformation (DFT) techniques. A sampled sinusoidal voltage signal is passed through a digital integrator and the magnitude of the digital integrator's output is measured as representative of the V/Hz ratio. The digital integrator is implemented in software using a difference equation in a generator protection unit. The technique may be used with either a fixed or a variable sampling frequency. When the sampling frequency is variable, the filter coefficients of the digital integrator are recalculated on-line each time the sampling frequency is changed, and a new value for the peak magnitude of the output of the digital integrator is calculated using the recalculated filter coefficients. Non-linear frequency response characteristics of the voltage sensors and non-ideal characteristics of the digital integrator are also adjusted using the measured frequency and error-frequency characteristics of the particular digital integrator and voltage sensors used.

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