Determination of the preventive heating current of a lightning protection cable with a built-in optical cable on a 110-220 kV overhead line to prevent the formation of ice-frost deposits

Abstract

Last climate changes in the world are expanding the list of region of the Russian Federation. For this region the need to prevent icy-frost deposits on wires and ground wires of 110-220 kV is becoming the main problem for grid companies in the autumn-winter period. Most of 110-220 kV overhead lines are equipped with an overhead ground-wire cable with incorporated optical cable designed to protect overhead lines from direct lightning strikes. Also this incorporated optical cable serves a function of an optical fiber link. In the autumn-winter period on the 110-220 kV overhead lines may the following accidental situations may occur: mechanical breakage of the overhead ground-wire cable which arise due to the weight of icy-frost deposits and the action of wind; overheating of the overhead ground-wire cable with incorporated optical cable during melting of icy-frost deposits above the permissible temperature of +80°C...+85°C resulting in damage to the optical cable. Preventive heating of part the overhead to the positive temperature by induction method from electromagnetic fields of a double-chain 110-220 kV overhead lines is the alternative of ice melting. The use of preventive heating of a part of overhead ground-wire cable 110-220 kV on the job requires the refinement of a mathematical model to estimate the required current value. A mathematical model is considered to determine the required current value to create a ground-wire cable with incorporated optical cable at a temperature of +(1-2)°C, at which ice-frost deposits are not formed. The mathematical model is based on the equation of the thermal balance of the overhead line conductor in steady state, adopted in the IEC 61597 standard. In the calculated example the ranges of permissible values of air temperature and wind speed are constructed for the use of an induction method for heating a part of a ground-wire cable with incorporated optical cable on a 220 kV double-chain overhead line. The use of an induction method for preventive heating of a part of a ground wires of the OKGT brand on a 220 kV double-chain overhead line having a cross section of an aluminum part of at least 70 mm2 is effective at a value of induced current of at least 150A for meteorological conditions of ice and sleet formation.

Keywords

• overhead power line
• lightning protection wire with built-in optical cable
• ice-frost deposits
• preventive heating