Research On AC/DC Hybrid Control Technology In 500kV Substation

With the increasing scale of power system construction,the related secondary equipment is also complex.Any loop of substation,power plant dc system and AC system has potential accident risks,which may cause power failure,damage or even large-scale power failure of power grid.AC/DC hybrid is a common accident or hidden danger in substations of different voltage classes.Its main features are: hidden before the incident,not easy to detect,difficult to prevent;It happens very quickly and has serious consequences.It is destructive and can hurt people,power grid and equipment.There are three common causes of alternating or direct current mixed connection.Two times the system internal insulation aging;The third is over voltage breakdown of the secondary system insulation.This topic based on the study of 500 kv substation communication,analysis of internal communication system and the different characteristics of the DC system,and from the actual work of all kinds of incidents and attempted,combing the various causes of occurrence of AC/DC mixed,phenomenon and consequences,combined with the substation in the state of operation and maintenance,failure mode,AC/DC hybrid probability of the occurrence and the severity of the consequences of the,analysis of AC/DC mixed in the operation of the work and risk points.According to the different situation,the level of risk and the probability of occurrence of mixing,this paper studies the technical measures of two kinds of AC/DC mixing prevention and control.One is the study of portable AC/DC power isolation short connection device,focusing on solving AC/DC hybrid connection caused by human error.The other is the development of power frequency AC voltage filter and alarm device.On the dc of the maintenance unit with the highest risk of AC/DC hybrid connection,the probability of AC/DC hybrid connection and the severity of the consequences are effectively controlled through the AC voltage filter.The safe and stable operation of 500 kV substation is the top priority of the state grid.The frequent occurrence of AC/DC hybrid accidents has also attracted great attention of state grid.The research of this subject has been successfully applied in over 500 kV substations in hubei province,and has obtained very good field application effect.It has successfully restrained two alternating AC/DC mixed events,accumulated valuable practical experience data,and laid a solid foundation for further research.