Overheating of Grounding Wire Clamps of Transmission Lines - Diagnostics, EMTP Investigation and Solution Suggestion

摘要

Overheating of ground wires clamps was revealed during a helicopter thermovision inspection carried out in the years of 2014 and 2015. This problem appeared on three lines owned by the Czech Transmission System Operator. Measured temperature of some of the overheated ground wire clamps reached relatively high values (up to 400°C). Based on this finding, several affected clamps on the 400 kV line were dismounted and examined. Footprints of heat stress was found on it. Even partial melting and welding of cast-iron and steel parts occurred in several cases. This paper deals with possible root cause analysis of the overheating phenomena. Mathematical model of affected lines was created and induced currents were examined for various grounding wires connection schemes and clamps contact resistances. A solution of the problem is suggested.