The Research For Air Gap Of The Valve Hall Of The High Altitude Extra-high Voltage DC Converter Station

With the rapid development of our country's economy,the demand for electricity in all walks of life is becoming more and more big.But,our country's energy reserves and the distribution of power load are disequilibrium,energy distribution in the southwest and northwest regions,more load concentrated in the eastern coastal areas in the south.Big flux over a long distance transmission is the main way to solve this problem.Compared with traditional AC power,DC power transmission has its unique advantages.On the one hand,DC transmission rapid precise regulation performance can improve the stability of parallel lines and transmission capacity.On the other hand,as a link between the regional power grid,DC transmission can improve the reliability and flexibility of the interconnected system operation.For long distance and large capacity transmission,high voltage direct current(HVDC),has nothing to do with the system frequency,low loss,large conveying capacity,economy is prominent,etc.In the economic and environmental aspects,the DC power has more obvious advantage.Valve hall air gap selection and the size of DC field hardware design of insulation distance is directly related to the safe and stable operation of dc project and project investment.According to the sending converter station of Guang Dong ultra high voltage direct current(UHVDC)power transmission and transformation project at an altitude of 2400 meters,the high altitude air gap discharge characteristics and low altitude were significantly different.The high altitude air gap distance valve hall of DC hardware selection and size design is based on empirical for mula under low altitude after altitude correction theory formula,its effectiveness is yet to be test.This pilot project in Kun Ming UHV base(elevation 2100 meters)to the valve hall with the typical types of air gap and DC field typical discharge experiment was carried out,in order to reveal the valve chamber under high altitude air interval and DC in hardware in the operating under impulse voltage and DC voltage discharge characteristics.Several main issues such as withstand voltage correction,air cle arance,and gap distance,are discussed in this paper by taking an example for the valve chamber air interval design of Xingsong converter station.In order to analyze the air gap flashover characteristics of switching impulse voltage of fittings in Xinsong converter station at the altitude of 2400 m,according to the fittings structure size of valve hall in Chuxiong converter station,this paper selects typical size grading ring and equalizing ball,and carries out an experiment in Kunming UHV base at the altitude of 2100 m.On this basis,this paper checks the air clearance of transmission side valve hall in Xinsong station and presents the discharge voltage curves for different altitudes after altitude correction.The study of air gap discharge characteristics and altitude correction provides a reference for practical engineering.Introducing the calculation principle of g parameter method,this paper puts forward a new iterative approach based on g parameter,and applies it to calculate the DC air clearances of Chuxiong and Xinsong Converter projects.