Conductor Temperature Monitoring And Rating Estimation For 220kV Tunnel Cables

The XLPE cable has basically replaced the traditional oil-filled cable for its merits, such as light weight, easy installation, good electrical and thermal performance, large capacity, and convenient operation and maintenance, and is widely applied in urban power grid. To meet increasing demand of load and save investment, it becomes important to maximize utilization of cables without adding new lines. More and more attention has been paid to cable temperature monitoring and rating estimation. One of the reasons is that it can guarantee cables operate in the rated temperature range to prevent insulation degradation caused by overheating; the other is to increase power delivery and provide the basis to power dispatch.The paper presents a method of calculating conductor temperature basing on the thermal network when the cable is in the heat-stable stats, discusses the conductor temperature rise in a period of cable carrying transient load and develops a system of conductor temperature monitoring and rating estimation for 220kV tunnel cables. The system can calculate conductor temperature and rating by using the monitored cable surface temperature, real-time load and the structure parameters of tunnel cables. It is made up of three parts: the real-time acquisition device, the wireless transmission system and the monitoring software. The on-line acquisition device includes an 8051 microcontroller embedded RF transceiver nRF9E5 and some digital temperature sensors DS18B20s. The wireless transmission system contains two nRF9E5s and a GPRS module.It is certified that the system works well on monitoring ambient temperatures and cable surface temperatures, calculating conductor temperature and estimating ratings for 220kV tunnel cables...