Gontar Y. Method of controlling the current overloads of medium voltage power cables

A model is proposed that allows to determine the parameters of long-term current load of a medium-voltage cable with cross-linked polyethylene insulation. The mathematical model for determining the parameters by introducing an analytical expression into the system of equations to determine the heat dissipation coefficient was improved, which allowed to take into account the design features of a particular cable. The range of operating modes in which it is necessary to estimate the overload capacity of medium voltage power cables with cross-linked polyethylene insulation is analyzed. Theoretical and experimental researches of definition of dynamics of heating of a cable АПвЕгаПу - 1 × 70 - 35 kV in the conditions of real production are carried out. The influence of technological features of production of medium voltage cables with cross-linked polyethylene insulation is analyzed. It is established that under conditions of application in semiconductor screens of furnace soot instead of acetylene at the screen-insulation boundary there may be places of local amplification of the electric field. The process of degassing of medium voltage cables with cross-linked polyethylene insulation is analyzed, on the basis of thermogravimetric analysis protocols practical recommendations on degassing terms are given. Provided that the load mode is permissible, ie the current overheating does not exceed the maximum permissible, the current and time of permissible overload are determined. The range of possible modes of long current loading for a concrete design of a cable is established, time and temperature limits at the set overload factor are defined. Practical recommendations for the integration of the proposed method of control in the system of control tests at cable companies are given. It is noted that the proposed method can be used for non-destructive testing of power cables.