Research On Risk Assessment Of Substation Considering Time-varying State And Load Capacity Of Equipment

As the hub of the power system,the safe operation level of the substation directly affects the safety and stability of the entire power grid.Most substations are exposed outdoors for a long time and are severely affected by the weather.The failure of main equipment and changes in load capacity will affect the safe operation of the substation,which may cause disconnection of the line or insufficient power supply,thereby threatening the safe operation of the substation.Traditional substation risk assessment uses the average annual failure rate of the main equipment to calculate the reliability of the main wiring,which cannot reflect the impact of time-varying equipment failures and load capacity changes on the operation risk of the substation and the impact on the power supply at the load point.This paper considers the impact of meteorological environment on the safety of substation operation,studies the time-varying failure rate and dynamic load capacity of equipment,and evaluates the risk of substation operation on this basis,which is of great significance to ensure the safety and stability of the power grid.The main work of the thesis includes the following aspects:(1)A prop ortional failure rate model of equipment and a calculation method for load capacity that take into account the health status and weather effects are proposed.First of all,considering that the equipment status score based on the fault tree is highly dispersed,and the impact of different component failures on equipment outages is different,a fuzzy comprehensive evaluation method of equipment status based on the analytic hierarchy process is established.On this basis,taking into account the health status of the equipment and the impact of weather,a proportional failure rate model of the equipment was established to quantify the time-varying risk of the main equipment.Then,combining equipment health status and equipment importance,a calculation method of equipment load capacity under the influence of multiple factors is proposed.Finally,the feasibility and effectiveness of the proposed model and method are verified through the analysis of a calculation example.(2)A risk assessment method for the main wiring of a substation that takes into account the power supply connectivity is proposed.Traditional substation risk assessment uses the average annual failure rate of the main equipment to calculate the reliability of the main wiring,which cannot reflect the time-varying failure risk of the equipment and its impact on the power supply at the load point.Based on the equipment proportional failure rate model,this paper uses the Monte Carlo method to simulate the failure state of the equipment,and takes the main wiring connectivity between the power supply line and the load point as the risk quantitative index,and establishes a substation that takes into account the power supply connectivity.Risk assessment model.Taking the substation of the improved IEEE-RTS79 system as the test object,the analysis of calculation examples shows that the failure rate of the main equipment in different scenarios has a greater impact on the risk assessment results of the substation,which verifies the necessity of the risk assessment taking into account the time-varying state of the equipment.(3)A substation risk assessment method that comprehensively considers the time-varying state and load capacity of the equipment is proposed.First,consider the load capacity of the equipment,use the maximum flow method to determine the power supply capacity of the substation system and the load points of each bus section under the current topology connection mode,and then obtain the load safety margin or the load safety margin in the N-1 situation based on the current load level.Then,the corresponding load reduction method is determined according to the overload situation,and the load loss risk of the substation is calculated.Finally,combining the time-varying state of the equipment and the operation of the equipment load,the risk assessment of the substation is carried out.The analysis of calculation examples shows that the proposed method can fully tap the power supply capacity of the substation system and improve the reliability of power supply under the premise of ensuring the safety of the main equipment.