Effects of agricultural fires on the performance of overhead transmission lines

It is noted that the occurrence of fires under transmission lines is responsible for a great number of line outages in many countries. The insulation requirements for lines of several voltage levels were established on the basis of field investigations and laboratory tests under fire conditions. The results obtained and the statistics presented indicate that for actual AC transmission lines with rated voltage up to 500 kV, faults are mainly due to conductor-to-ground short circuit at midspan or phase-to-phase short circuit, depending on line configuration. Another problem arising from the burning is the contamination of the insulators due to the accumulation of particles (soot, dust) on their surface. Pollution severity in terms of ESDD (equivalent salt deposit density) measured on insulators coming from regions of sugar cane fields in Brazil has shown values of up to 0.1 mg/cm²