Abstract: Abstract: Taking the bus bar joint as an example, this paper analyzes the sources and influencing factors of the temperature rise of the electrical equipment joints. The main factors of heat generation are heat generated by current through contact resistance and sunshine heating. The heat dissipation channels include radiation heat dissipation, convection heat dissipation, and conduction heat dissipation. This paper establishes a balance equation between heat production and heat dissipation. A thermal experiment is designed, and the relation equation between bus plate joint heating and operation environment is deduced based on the experimental results. It is proposed that when the operating conditions and the environment are different, the key point for determining the detailed quantitative relationship between the temperature of the electrical equipment joints and each influencing factor is to determine the α coefficient and ε coefficient of the on-site operating environment. Based on these values, the contact resistance of the joint can be calculated and used to evaluate the status of the electrical equipment joints. 0. Introduction It is significant to study the heating failure of electrical equipment joints. 1. Thermal equilibrium theory Based on the principle of heat balance, a balance equation for generating heat and dissipating heat of electric equipment joints is established. 2. Temperature rise test of joint The internal relationship between the heating failure and the operation environment of electrical equipment joints is studied through experiments. 3. Result discussion The contact resistance R value of the joint is calculated based on the experimental data and field test data, and the next step is to evaluate the state of the electrical equipment joint. 4. Analysis of experimental errors and future research problems This paper analyzes the experimental errors and future research problems. 5. Summary It provides a new idea for evaluating the state of electrical equipment joints. Keywords: Electrical equipment joint; Joint temperature rise; State evaluation; Load current; Environmental conditions Supported by the National Key R&D Program of China (2016YFB0101900)