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Instantaneous overcurrent element for heavily saturated current in a power system

A power system and overcurrent technology, applied in the direction of electrical components, control/regulation systems, parts of emergency protection devices, etc., can solve problems such as component failure, tripping action delay, etc.

Inactive Publication Date: 2005-08-17
SCHWEITZER ENGINEERING LABORATORIES
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This will cause a noticeable delay in the tripping action
In extreme saturation, the component may fail completely in the event of a fault, which of course is highly undesirable

Method used

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  • Instantaneous overcurrent element for heavily saturated current in a power system
  • Instantaneous overcurrent element for heavily saturated current in a power system
  • Instantaneous overcurrent element for heavily saturated current in a power system

Examples

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Embodiment Construction

[0012] As mentioned earlier, current digital transient overcurrent elements in microprocessor-based protective relays are implemented using digital filters. The digital filter typically includes a pair of quadrature finite impulse response filters or other filter arrangements. Examples of such filters include Fourier filters, cosine filters, and least squares fitting filters. It should be understood that the present invention does not require a particular type of digital filter but a filter that can be used with a variety of digital filters.

[0013] However, digital filters have the disadvantage of operating imprecisely when the current in the power line is large enough to saturate the current transformer, which will result in distortion of the transformer output signal. In some cases, the saturation is sufficiently large to delay recognition of the fault and thereby delay tripping of the circuit breaker. This is called a glitch. In addition, however, if the saturation is ...

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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.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. The RMS value from circuit (88) is compared against the threshold value in comparator (90).

Description

technical field [0001] The present invention relates generally to transient overcurrent elements for use in microprocessor-based protective relays in power systems, and more particularly to providing accurate current magnitudes under normal operating conditions and when current waveforms in current transformers are heavily saturated. value information of the overcurrent element. Background technique [0002] Instantaneous overcurrent elements are commonly used in protective relays in power systems. The instantaneous current magnitude is compared to a threshold to determine a fault on a preselected line. Overcurrent elements implemented digitally in microprocessor-based protective relays typically use a pair of quadrature finite pulse filters to properly compute complex numbers representing the magnitude of the phasor of the fundamental component of the line current. Fourier filters and cosine filters are generally used as examples of such filters. When using such a filter...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H1/00H02H1/04
CPCH02H1/0092H02H1/046
Inventor G·本穆亚尔S·E·措霍尔A·古茨曼-卡西拉斯
Owner SCHWEITZER ENGINEERING LABORATORIES
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