Special Problems And Solutions For Ice Melting On Transmission Lines Of Small Hydropower Stations

There are a large number of small hydropower stations in the south of China.The transmission lines of most of the small hydropower stations have the danger of icing,which affects the normal operation of small hydropower stations.Therefore,it is of great significance to the study of the ice melting of transmission lines in small h ydropower stations.Small hydropower stations are generally small in size and are mostly funded by individual capital.In order to save money,the hydroelectric generator of the hydropower station will be used as the power source of the ice melting device for the line melting ice.Therefore,when the line melts ice,the small hydropower station will operate independently as a small isolated island,so its ice melting device needs special design.The contents of this paper include the following aspects.Firstly,this paper introduces the physical process of thermal ice melting,analyases the characteristics of ice cover type,icing section shape and icing thickness of small hydropower stations in central and southwest China and its influence on the ice melting current,and calculates the ice-melting current and the power of transmission lines in a small hydropower station using Burgos Doyle melting ice formula.Secondly,this paper analyses the problems of capacity limitation and cost limitation in the ice melting of small hydropower stations and proposes the ice-melting method of isolated island DC melting ice.In order to minimize the cost,the rectifier uses a 6 pulse thyristor rectifier and a connecting mode of a rectifier transformer and a reactor.At the same time,the 5th,7th and 11 th passive filters are parallel to the outlet side of the generator to reduce the harmonic current injected into thr generator and avoid the power generation drop.Then,this paper analyses the static power frequency characteristics of power generator,the harmonic amplification circuit in system to make the filter appear overcurrent.This paper anlyases the harmonic amplification equivalent circuit of the island ice melting system,and thearmonic amplification mechanism from two aspects of frequency decrease and frequency fluctuation.In order to suppress the harmonic amplification in the system,two major solutions are proposed in this chapter,one is to optimize the filter parameters.The two is to control the load change rate.According to the speed of the generator,this paper proposes a load control strategy combined with frequency detection to further reduce the possibility of harmonic amplification.Finally,according to the requirements of a hydropower station's ice melting project,this paper determines the parameters of rectifier transformer,reactor and rectifier and designes the 5th,7th and 11 the filters.Then,according to the relevant e xperimental data,determines the parameters of load correction strategy.Finally,field tests were carried out,and the experimental data of 35 kV and 110 kV lines and the harmonic amplification phenomenon in the process were analyzed.The test results verified the correctness of the analysis for the special problems of ice-melting in small hydropower stations and the effectiveness of the solutions.