Design And Application Of Phase Selection And Switching Controlled System For 500kV Long Power Line With No-load

The 500 kV voltage grade line has the characteristics of low loss and long transmission distance.It has become the main transmission line in China,and 500 kV substations are gradually increasing.With the development of power grid,1000 kV UHV station is put into operation.The operation of new substation strengthens the ability of resisting risk of power grid,and puts forward new problems for system operation.The newly-built substation is transformed into a new station by disconnecting and breaking in the middle of the original line.The length of 500 kV line is gradually shortened.Most of the primary equipments are still used.The secondary protective measuring and controlling equipments are replaced with the same type of equipments as the new station to cooperate with the work.Because the original line is long and the capacitance to the ground is large,the reactor is usually added to supplement the reactive power of the line.When the length of the line is shortened,the overcompensation is caused when the reactor is put into operation.In this paper,the dynamic delay sequential phase selection and closing technology and the phase separation and closing device are combined and arranged in 500 kV control circuit.By collecting bus reference voltage,the circuit breaker is timed and closed one by one to effectively solve the problem of DC bias.The system design is based on the actual line with high-voltage reactor operation data and phase selection device parameters and functional characteristics of the development,using the phase selection device built-in voltage discrimination plug-in,bus and line voltage comparison,the introduction of delay mechanism,the calculation of the circuit breaker into mechanical time,so as to be sure.The control time of breaker splitting and closing is determined,and the closing time node is controlled near the peak of AC voltage to ensure the minimum DC component and avoid the operation risk without effective zero crossing point.The system can simulate the controlled circuit breaker deeply and record the breaker breaking-up time.The more the breaker breaking-up times are,the more accurate the predicted inherent mechanical time of breaker breaking-up will be.In the system debugging,in order to eliminate the DC component as far as possible,the contents of the debugging scheme are formulated in detail.Several breakers are designed to split and close,and tested at two opposite terminals respectively.The corresponding four breakers' closing data are obtained,and the waveform file data recorded by the recorder are obtained.The operation of the system is analyzed,and the conclusion is drawn that the application of phase selection and closing technology and dynamic delay sequential phase selection and closing system can effectively solve the DC offset problem.