Frequency measuring system for universal voltage input power frequency signal

Abstract

The invention discloses a frequency measuring system for a universal voltage input power frequency signal. The system consists of a signal conditioning circuit, an isolation operational amplification circuit, a lowpass filtering circuit, a comparator circuit and a digital signal processor, wherein the signal conditioning circuit is designed by adopting a universal circuit, an alternating current power frequency signal is suitable for a voltage range from 1V to 250V, thus meeting most application occasions of a power system, the isolation operational amplification circuit is used for isolating strong current signals from weak current signals and replacing the traditional transformer components, the lowpass filtering circuit and the comparator circuit are matched with the isolation operational amplification circuit for changing alternating current signals into direct current signals, and signals output by the comparator circuit do not need to be subjected to signal isolation and can be directly connected to the digital signal processor for finishing frequency calculation. The method has the characteristics of simple circuit, small size, little phase delay and the like.

Description

technical field [0001] The application belongs to the technical field of electrical systems, and in particular relates to the frequency measurement technology of relay protection devices. Background technique [0002] In the traditional power system relay protection device, the input signal is the power frequency (50Hz) signal transmitted by the secondary transformer, the voltage value may be tens of volts to hundreds of volts, and the relay protection device needs a cycle (20mS) Collect real-time data with a fixed number of points (24 points or 40 points), and based on these data, the relay protection device must perform real-time protection algorithm calculations to determine whether there are various faults such as short circuit or grounding in the power grid. In order to ensure the accuracy and reliability of the protection algorithm, the data collected by the cycle wave should be an integral multiple of the actual frequency (50Hz), and the phase delay should be as small...

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Problems solved by technology

[0004] The purpose of the present invention is to overcome the problems of large volume, complex circuit, long delay for input signal, difficult to guarantee accuracy or narrow application range in the power system frequency measurement system in the prior art, and propose a universal voltage input system. Power Frequency Signal Frequency Measurement System

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