Instantaneous overcurrent element for heavily saturated current in a power system
AssigneeSchweitzer Engineering Laboratories, Inc.
InventorsGabriel Benmouyal, Stanley E. Zocholl, Armando Guzman-Casillas
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Abstract
The instantaneous overcurrent element, used in a microprocessor-based protective relay for a power system, includes a finite impulse response filter which generally is a cosine filter and is responsive to the current waveform from the current transformer for fault determination unless the distortion in the current reaches a preselected threshold, at which point a peak detector circuit is used to provide the current magnitude values for fault determination.
Claims7
An instantaneous overcurrent element for use in a microprocessor-based protective relay for a power system, comprising:
- a digital filter circuit, responsive to a secondary current waveform from a current transformer which is responsive to a current waveform from the power line, for determining the magnitude of the current waveform;
- a peak detector circuit responsive to the secondary current waveform for determining the peak magnitude of the current waveform;
- a circuit for determining the distortion of the output from the current transformer;
- a comparison element for comparing the distortion against a predetermined standard;
- and
- a switch connecting the output of the filter circuit to a fault determination circuit when the distortion is less than the predetermined standard and connecting the output of the peak detector to the fault determination circuit when the distortion is above the predetermined standard.
Dependencies are inferred from the claim text.