Research On Heat Transfer Mechanism Of 12kV Environmentally Friendly Gas Insulated Switchgear

Switchgear is an important part of the power distribution system.As people pay more attention to environmental protection issues,it has become a trend to reduce or replace SF6 gas use in the power industry.Because the environmentally-friendly switchgear is more severe than the SF6 gas-insulated switchgear,the impact on electrical equipment is more serious.At present,the commonly used method is to change the temperature rise by the control variable method after the temperature rise test and the simulation match,but the switch cabinet model is complicated and the influencing factors are many,while the multi-variable method of reducing the temperature rise has a large amount of work and calculation.Therefore,this paper analyzes the typical thermal model in the switchgear,uses DOE test design and research,reduces the number of simulations,and explores the significance of the factors;and adopts the DOE test on the 12kV environmentally friendly gas-insulated switchgear by finite element analysis.The design scheme calculates and analyzes the three-dimensional temperature field and airflow field,and obtains the influence of factors on the temperature rise.The specific research content is from the following aspects:1.Based on the principle of heat generation and heat dissipation in the switchgear,based on the basic theory of heat transfer,using the hotspot analogy theory to analyze the heat transfer process of the simple model,establish a typical single-phase and three-phase steady-state heat path analysis model in the switchgear;By calculating the thermal resistance of some parameters in the model by the control variable method,on the basis of meeting the actuality of the switchgear engineering,the influence trend of the thermal resistance and parameters in the range of values is obtained,which provides research ideas for the subsequent DOE test design.2.Using the methodology based on probability theory and mathematical statistics,the theoretical design and software simulation of DOE for the switch cabinet are carried out.The original simulation of the simple model and the DOE test design are compared and verified.The feasibility and superiority of DOE for the test design of the switchgear is established.The simple numerical calculation model of the circuit breaker is established.The DOE is used for the sensitivity analysis.The sensitivity analysis test design of some parameters extracted under the thermal path model is carried out.Simulations yield reliable and significant factors.3.Based on the heat conduction differential,fluid motion control and radiation heat transfer equation,the finite element method is used to calculate and analyze the electromagnetic field-temperature field-airflow field coupling for the 12kV environment-friendly gas-insulated switchgear;The post-calibration model is used for simulation analysis.By comparing the temperature field and airflow field distribution of SF6 gas and dry air in the closed air chamber,the temperature rise difference of the three stations is about 10-14K.4.Based on the above temperature rise difference,combined with the parameters of thermal path modeling and the sensitivity analysis under DOE,the temperature rise of the single-factor kinematic viscosity parameter is reduced by about 5K;then the multi-factor simulation DOE test design is carried out.Optimization analysis of heat dissipation,through optimization analysis of flow and thermal parameters,structure and state parameters,not only verify the significant effect of kinematic viscosity and structural thickness on temperature rise,but also find mixed gas under engineering actual dry air conditions to improve kinematic viscosity.Provides basis for SF6 gas conditions and three-station hot spot temperature rise heat dissipation optimization.