Reaserch And Implementation Of Intelligent Technology Of Urban Box-type Substation

As an important link at the end of urban distribution network,urban box-type substation is an important equipment to ensure the safety and reliability of urban power supply,as well as an important node for the integration of clean energy into the power grid.Its degree of intelligentization directly affects the safe and reliable power supply of the box-type substation and the power consumption experience of the majority of power users.The conventional means of urban box-type substation intellectualization adopt the mode of "intelligent switch+measuring instrument",which has a low degree of intellectualization,monitoring blind areas,incomplete security protection and can not effectively control the power quality.To solve this problem,the method of cable insulation fault monitoring based on the residual current soft sensing technology,the method of power quality controlling based on the symmetrical component method to adjust the three-phase current unbalance were studied,and at the same time,the intelligent distribution merging unit,intelligent feed and unbalanced adjusting terminal were studied,which relevant technical means to realize the intellectualization of urban box-type substation in this thesis.The main research contents and achievements are described below.The overall scheme of the intelligentization system of urban box-type substation was studied.The functional requirements of the intelligentization distribution system of urban box-type substation were analyzed,and the overall scheme of intelligentization distribution system of urban box-type substation was designed,including the intelligent distribution terminal layer,communication transmission layer and background monitoring layer,and the scheme of primary main loop of the intelligent distribution terminal layer of urban box-type substation was designed.The theory of residual current soft sensing technology was studied.It was analyzed that the conventional residual current detection method of city transformer cannot be widely used in practice due to the limitations of installation mode,position and size,especially when N-wire is broken,the residual current cannot be effectively measured,resulting in incomplete safety protection of urban box-type substation,a residual current soft sensin g method based on current vector sum operation was proposed.The effectiveness of the proposed method was verified by simulation an d experiment.The theory of three-phase current unbalance tuning technique was studied.The reason why the conventional three phase current unbalance adjustment method can not regulate the three phase current unbalance effectively was analyzed.Based on the existing capacitance compensation device in urban box-type substation,the power quality control method based on symmetrical component method was studied,and the effectiveness of the method was verified by simulation and experiment.The technical means to realize intelligent urban box-type substation such as intelligent power distribution merging unit,intelligent feed and unbalanced adjusting terminal were studied.The hardware module and software process design of the intelligent terminal devices were completed,and the functions of collecting,protecting and controlling the power and switching parameters of the low-voltage inlet and outlet circuits of the urban box-type substation were realized.The effectiveness and reliability of the prototype were verified by experiments.On the platform set up in the laboratory,the experimental verification and data analysis were carried out on the soft sensing technology of residual current,the technology of three-phase current unbalance adjustment,the intelligent distribution merging unit,the intelligent feed and the unbalance adjustment terminal device.The results show that the residual current soft sensing method is effective and the measurement error is less than 1%,which can meet the actual measurement requirements.The power factor can be compensated to 0.99 in the three-phase current unbalance adjustment experiment,and the three-phase current tends to balance after compensation,which can meet the actual power quality regulation demand.The designed intelligent terminal devices are accurate in measurement,the measurement error of electrical parameters is less than 1%,and the protection functions are relatively perfect and effective,which can meet the monitoring needs of urban box-type substation.The electromagnetic compatibility test of the prototype was done,and the result is qualified.