Research On Intelligent Schemes Of Tripping And Reclosing For Multi-circuit Transmission Line On The Same Tower

Because muti-cicuit transmission line on the same tower has the advantage ofnarrow land corridor and large energytransmission capacity, it becomes an inevitabletrend for the main network of power system in China.Though the protection andcontrol technologies for muti-cicuit transmission line on the same tower improved alot recent years, the conventional reclosing scheme of single circuit transmission linecontinue to be used but is not suitable for muti-cicuit transmission line on the sametower, which is unfavourable to the reliabilityof power system. Considering the therequirements of practical application of autoreclosure on double cirecuit transmissionline, each details of tripping and reclosing are studied and based of these research, theintelligent control technologyof tripping and reclosing for double-circuit transmissionline on the same tower is present.The main contents are shown as follows.(1) Characteristics of fault sequence voltages and currents on double circuit lineon the same tower are studied, methods based on three sequences is put forward forshort-circuit and break-conductor fault analysis and interconnections of sequencenetworks of typical break conductor fault types are given.(2)The influence of different trip sheme on capacityof power transmission andsystem stabilityafter fault occurring on double circuit transmission line is studied andthe wayof onlytripping faulty conductor(s) is conformed as optimal trip scheme fordouble-circuit transmission lines on the same tower.(3) New design schemes of shunt reactor are put forward, for better compensationeffects on EHVdouble-circuit lines. Method of how to determine the value of reactorsand the withstand voltage of small reactors on neutral point is also present forpractical design and manufacture of shunt reactors.(4)Anew adaptive autoreclosure technique based on fault point voltages ispresent for identifying permanent and transient fault on double-circuit transmissionline on the same tower.This technique solves the problems that conventionalcriterions, based on terminal voltage on the opened conductor, are always obsessed byinductive coupling voltage, fault position and transition resistance.(5)The process of reclosing is studied and an improved reclosing scheme inphase order is put forward.Then how to choose the first reclosing terminal and calculate the ideal reclosing angle is given for decreasing the impact of the secondshort circuit current.(6)The characteristics of parameters of four-circuit transmission line are studied,and then an algorithm is put forward for decoupling the parameters of the line.According to interconnection of sequence networks, a method is present for faultanalysis on four-circuit transmission line. Based on these theoretical analyses, thetechnologies for reclosure on double circuit line raised above are extended intoapplication in four-circuit transmission lines on the same tower.The smart operation of autoreclosure is realized after the application of the abovetechnologies, which can reserve the transmitting capacityto the maximum, recoverpower supplyas soon as possible in the case of transient fault and decrease the impactof the second short circuit current in the case of permament fault.