Method for measuring real-time frequencies in protection device

Abstract

The invention discloses a method for measuring real-time frequencies in a protection device. The method comprises the following steps that: step 1) fixed-interval sampling is performed on the whole cyclic waves of measured electrical signals; step 2) a calculation formula is obtained; step 3) N/2 of the number of points is added to the value of the latter part of the calculation formula; step 4) angular frequency deviation is obtained through calculation; and step 5) a real-time angular frequency is calculated based on the angular frequency deviation, and conversion is performed on the real-time angular frequency, so that the real-time frequency of the measured electrical signals can be obtained. According to the method, the sinusoidal waveform characteristics of power frequency signals are utilized; fixed-interval sampling values are used, so that curve fitting and accumulation are performed, and therefore, frequency difference can be derived on the basis of a fixed power frequency, and therefore, an actual frequency value can be obtained. Since the actual frequency value can be obtained with few sampling points, no complex logic operation is involved in a measurement process, and therefore, the method can be implemented simply and efficiently; and the frequency measurement accuracy of the method in practical application can fully meet the relay protection and measurement requirements of a power system.

Description

technical field [0001] The invention relates to the technical field of power system parameter measurement, in particular to a method for measuring real-time frequency in a protection device. Background technique [0002] Frequency is the main performance parameter of power system. There have been many large-scale power outages caused by frequency collapse in the world. Insufficient power of the power system will cause the frequency to drop, and the automatic power generation system will start the rotating equipment to restore the frequency of the power system to normal. When the frequency is seriously insufficient, the low-frequency load shedding device cuts off part of the secondary load to maintain the system frequency and power supply to important users. The premise of implementing these measures is that the corresponding equipment and devices can accurately measure the real-time frequency of the system. The real-time frequency of the system is the main parameter of the...

AI Technical Summary

Problems solved by technology

[0003] The frequency measurement is mainly divided into hardware measurement and software measurement. The hardware measurement frequency is generally composed of a zero-crossing comparison circuit, a square wave forming circuit and a counter. It is simple and convenient, but it needs to increase the hardware circuit, which not only increases the hardware cost but also is susceptible to interference.

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