Temperature analysis and ampacity evaluation of HV cable joints based on thermal flow coupling and measurable data

Obtaining the temperature and ampacity of high voltage cable joints during operation is crucial for increasing the reliability and flexibility of power systems. Indirect measurement methods based on digital models have gained widespread attention because of their potential for accurate and comprehensive assessment. However, owing to limitations in modelling techniques and measurement capabilities, the digital model of cable joints necessitates the use of parameters that are difficult to obtain, resulting in limited accuracy, high costs, and poor interpretability. Therefore, in this study, a digital model is constructed on the basis of thermal-flow coupling and measurable data, and an ampacity evaluation method is proposed. Based on the installation conditions and heat transfer rules, the external environment model of cable joints has been simplified. The multiscale modelling method is adopted to couple temperature data between a 3-D cable joint with the surrounding air model and a 1-D external environment model. The finite element method (FEM) is used to analyse the thermal performance. Taking a 110 kV, 630 mm² cable joint as an example, the temperature distribution and flow velocity distribution are simulated. The temperature test results show that the proposed model is consistent with the test results. The influences of the AC current, ambient temperature, and thermal conductivity are simulated to prove that the digital model meets the requirements of complex operation conditions. Considering the external ambient temperature and internal thermal conductivity, an evaluation function is determined through regression analysis to rapidly calculate the ampacity. In summary, the proposed method matches actual measurement capabilities, which has potential for application in the actual field.