Online Monitoring System for Insulation Temperature of High Voltage Railway Cables

Electrified railways have become an inevitable direction for the development of railways in China due to their high traction power, fast operating speed, and high efficiency. As a key equipment of the traction power supply system, high-voltage cables bear the task of transmitting electrical energy, and their operation directly affects the safety and stability of the traction system. Due to outdated manufacturing technology, external damage during construction, and outdated monitoring technology in China, the failure rate of high-voltage cables is about 10 times higher than that of developed countries.

The main methods currently used for online monitoring of insulation and faults in high-voltage cables include online monitoring of insulation resistance, online monitoring of partial discharge, and online monitoring of temperature. The temperature, as a non electrical quantity, is an important parameter reflecting the safe operation of high-voltage cables. High voltage cables can accumulate heat for a long time during operation, leading to excessive temperature and accelerated aging, resulting in a decrease in insulation performance. In severe cases, it can also cause fires and affect the safe operation of power transmission. However, the accumulation of heat before various faults occur in high-voltage cables is a slow development process. As long as an effective temperature monitoring system can be used to monitor the temperature of the cables in real time, it can effectively prevent or even eliminate the occurrence of such accidents.

The temperature distribution of the two high-voltage cables is basically stable, but at the terminal head connecting the transformer and the terminal head connecting the circuit breaker, the temperature is higher than the middle position of the cable. This is because the contact thermal resistance of the cable at the terminal increases, causing a temperature rise. Therefore, the temperature is slightly higher than the temperature of the intermediate cable body, and the cable joint is an important detection target for temperature monitoring. The distribution of the temperature curve can also prove that the system principle designed in the study is correct and works stably. En même temps, a comparative analysis of the temperature measurement data of the system and the infrared temperature measurement data shows that there is a small error between the two. This is because the infrared thermal imaging temperature measurement cannot directly contact the surface of the measured cable, and there is a certain distance between the cable and the infrared thermal imaging temperature measurement, resulting in a slightly lower measurement temperature than the direct contact fiber optic grating temperature measurement.