Calculation And Analysis Of Cross-line Fault Of Different Voltage Grade Lines In Substation

With the development and progress of China's economy,the demand and dependence of electric power will gradually increase,the continuous construction of transmission corridor and the contradiction of farmland resource protection become the main bottleneck restricting the development of China's power grid.This makes the substation near-area transmission lines side-by and cross crossing the situation more and more,with the voltage level and different voltage levels of line-crossing failures occur.Near-area fault of substation,such as a line failure,may lead to multiple complex failures,to the power system caused many shocks,if the response measures improper,will have serious consequences.However,in practical engineering,the calculation and analysis of different voltage grade crossover faults is complicated by the influence of different neutral grounding modes,electrical connection and coupling between double circuit lines.In this paper,the calculation and analysis of the line crossing faults of different voltage-grade lines in the substation are combined.Combining with the situation of the outlet in the substation,considering the neutral grounding mode of the mixed-voltage double circuit with strong electric connection and the difference of the coupling of the line,this paper puts forward the mixed-pressure nonidentical tower double circuit line,The decoupling method of the mixed-pressure part of the same tower line,the common impedance is corrected to obtain the independent sixorder network of the mixed-voltage double circuit with strong electric connection.According to the different types of cross line fault of the mixed-voltage double circuit line,the fault is divided into two-line grounding fault and cross line ungrounded fault,considering the influence of strong electricity connection,writing fault boundary condition,deriving six order component relation.The PSCAD simulation software is used to build the mixed-pressure non-identical tower double circuit in the neutral point with strong electric connection and different grounding modes.Mixed-pressure part of the same tower double circuit and Neutral point direct grounding mode of mixed-pressure part of the same tower double circuit model,a variety of cross-line grounding fault and cross-line ungrounded fault simulation.The fault point short-circuit current obtained by the calculation method in this paper is compared with the simulation results,and the accuracy and practicability of the proposed fault calculation method are verified.