MV cable temperature characteristics in dependence of load current, ambient environment and temperature. determination of the critical environment

The paper presents results of Latvian distribution system operator Sadales tikls AS (ST) and Riga Technical University (RTU) joint research on possibilities to increase the permissible loading level of the operating MV cables in order to improve the efficiency of the existing network assets usage and increase the supply reliability. Permissible loading level determination of the operating MV cables from the heating point of view is affected by many variable factors such as ambient environment, temperature, number and configuration of the cables etc. To estimate the temperature characteristics in dependence of load current of the operating MV cables in the real environment at different climatic and ambient environments (cable channels, ladders, soil and pipes) in the cities of Latvia a special MV cable sheath and ambient environment temperature monitoring device is designed. Sheath and ambi-ent environment temperature monitoring of nine 10 kV and 20 kV cables at four ST 110/10–20 kV substations is carried out for a period of one year. By analyzing the acquired temperature monitoring data, dynamics of the cable sheath temperature in dependence of load current, ambient environment and temperature is determined. A mathematical model for maximum achievable MV cable sheath temperature prediction is developed.