Research On The Protection Strategy Of The Ground Cable Of Arc-grounding Overvoltage

With the development of national economy,setting up all kinds of economic development zone lead to the high quality of electricity and the regional electricity centralized and large electricity power are the trend of future power system.In order to improve the capacity of the distribution network and the safety and reliability of the system,the urban distribution network was upgraded by changing the original overhead line to the power cable.Due to the cable capacitance per unit length is dozens of times of the overhead line,the capacitive current of distribution network system is more and more high as the length of ground cable in the distribution network increase.It caused excess capacitive reactive power in the normal operation of power system and the arc grounding overvoltage arises in the System of single-phase earth fault,which are the challenges to the city distribution network management and operation.Therefore,the cause and protection strategy of over-voltage of arc light earthing fault was discussesd in this article,to provide a reference basis for management and operation department.First,through the analysis of the cable distribution network of various fault types,the causes of intermittent arc grounding and its influence on the distribution network system are concluded.Based on the study of the theory of the over-voltage of arc light earthing fault model,the permanent ground fault model and over-voltage of arc light earthing fault model are respectively established in this paper.The intermittent arc grounding optimization control model is established by the voltage and current integrated control the arc extinguishing and combustion.This model of arc resistance nonlinear change is implemented by using the energy balance theory.which laid a solid foundation for the further study of arc grounding overvoltage fault protection.Secondly,the theory of arc grounding overvoltage grounding fault protection was researched in this paper.According to the characteristics of the cable network,as well as other over-voltage of arc light earthing fault protection,this paper established a multi-level control of over-voltage of arc light earthing fault protection strategy.First of all,when the normal operation of the system,the capacitive current will cause the system reactive power balance.The three-phase shunt reactor excess capacitive reactive power compensation system can ensure the voltage stability.when the single-phase earth fault occur in urban distribution network,three-phase shunt reactor of capacitance current compensation system and the neutral point via small resistance grounding to limit the over-voltage of arc light earthing.when the second floor cannot limit over-voltage of arc light earthing fault,the shunt ground fault protection based on mathematical morphology was adopted to turn the fault into metallicity ground fault.Finally,the model of arc logic optimize control and the simulation model of the 110 kV cable outlet substation are established under the environment of Matlab.the arc logic optimize control model and the strategy of arc grounding overvoltage fault protection is verified by simulation.The simulation analysis shows that this model is more flexible and accurate control compared with other intermittent arc grounding model.It can be accurately simulated arc grounding overvoltage under different working conditions.The arc grounding overvoltage and the system reactive power balance well be solved by the control strategy presented in this paper.It can guarantee the economic security of the system and provide certain experience reference for the electric power operation unit.