Grid Power Quality Measurement And Research

With the fast development of economy in recent years, the need for electric power has been increasing steadily and the characteristics of the load have been changing continuously. With the marked increase in nonlinear customers of high energy-consuming, the influences on power quality exerted by this kind of customers are becoming more and more significant and therefore much more stress is laid on these problems by experts all around the world. Because power quality is related to the rights of power generation enterprises, power supply enterprises and customers, it is one of the most important indexes of electrical products. High quality power electricity is important for ensuring the safe and economic operation of power grid and electrical equipments. It is also essential for guaranteeing the normal order of social production and improving the living standard of people. The problems occurred in power quality are not totally caused by power enterprises. Some of them are caused by customers' interference. The need for higher quality power electricity is the result of the development of technology and economy. In order to acquire high quality power, electric power enterprises, electrical equipments manufacturers and power use customers must act in concert.This article introduces the basic concept of power quality and the 6 indexes (frequency, harmonics, deviation, unbalance factor, fluctuation and flicker) to measure power quality. The mathematical methods most in use, such as discrete Fourier series, fast Fourier series, instantaneous reactive power theory and wavelet transform, to analyze power quality are elaborated.Through on-the-spot and online measurements of different substations and transmission lines of Jinan power grid and based on the analysis of the data acquired through measurements, this article studies the power quality conditions of Jinan power grid. Based on comprehensive analysis of power quality, the main factors that influence the power quality of Jinan power grid are found. Among these factors, rectification load, low-voltage electrical equipments and electric arc furnaces form the main harmonic source, which directly influences harmonic distribution and power quality in Jinan power grid. And as a result, the electrical equipments can be damaged easily. In addition, electrified rebuilt of Jiao Ji railway is under construction. After the operation of this railway, harmonic condition in power grid will be deteriorating. Based on the analysis of power quality of Jinan power grid, methods presented by this article will be meaningful to improve power quality of Jinan power grid.