| Today, power is a sort of important energy source. It is widely used in many fields of industry, agriculture and national defense. With the development of power system, the power quality is requested to be better and better. Harmonic is the most general phenomenon in power system. And harmonic is the main index of power quality. Electric power system harmonic is one of the most important parameters. With the development of electric power and electron technology, a number of the nonlinear loads and all kinds of commutating equipments are widely applied in every walk of life, what they bring a mass of harmonic current make the content of harmonic increase in the power system and quality of power drop. The harmonic affects the safe operation and economic benefit of power supply enterprises to great extent. So, it is urgent to eliminate harmonic.It needs the cooperation of the electricity utility and customers to manage power quality. One hand, the customers require power utility can insure them to use the normal electricity, on the other hand, power utility require their customers do not influence the normal operation of public network when they use electric power. Especially, it is necessary to manage power quality from headstream for some customers who need vast electric power and would cause the high worse of power quality of public network. This article introduces the conception and harms of harmonics. The suppression methods most in use in power system are introduced by combining the condition of harmonics in Jinan power grid and the influence exerted by the electrified railway on power system. How to blaze new trails in management is analyzed and researched.Electrified railway is a special consumer of electric power system , its load is of nonlinear, asymmetry and fluctuation. The main harmonic problem in our country is consistency between utility and electrified railway. A great lot of harmonic produced by electrified locomotive (mainly including order 3, 5 and 7) is directly injected into utility. The effect of harmonic to utility must not be ignored. So restriction on harmonic injected into utility is imperative. But characteristics of traction load include single phase, unbalance and random, so harmonic of traction load is also different from harmonic of other load. At present the knowledge of traction load harmonic is limited, so full-scale and in-depth study on traction load harmonic is needed. The paper introduces the harmful effects of harmonics disturbance on system operations. The paper points out problems of the national harmonics standard on electrified railway.The harmonic emission limits index distribution for distorting loads is very important for both power supply department and consumer. The consumer's harmonic limit determination methods proposed by GB/T 14549-1993, GB/Z 17625. 4-2000 and IEC61000-3-6 are introduced. The paper suggests applying coincidence factor in consumer's harmonic limit calculation and mainly describes a method of determining the coincidence factor. As for electrified railway, distributing method of harmonic emission limit and evaluation method are discussed especially. Combining the condition of harmonics in Jinan power grid and the influence exerted by the electrified railway on power system, the harmonic emission limit and evaluation method of the electrified railway in Jinan are put forward. |
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