Forensic analyses of conductor spans through mountainous terrain

Following a re-conductoring project of a 230kV line through mountainous terrain in central Arizona, a quality control inspection revealed a series of significantly out-of-plumb suspension insulators. A forensic investigation of the line segment was conducted to evaluate the operational and code compliance implications of the problematic insulators and associated spans. The difficult terrain provides challenges for collection of timely survey data, resulting in highly variable conductor temperature observations from span to span. In light of the variable survey conditions, adjunct mathematical routines are presented that generate accurate line models calibrated to either conductor sag or insulator swing. Results of the forensic evaluation provide insight toward engineering, construction and maintenance practices that can influence the quality and serviceability of lines built over rugged terrain. Results of the enhanced analyses indicate the subject line meets all code and operational requirements where less rigorous techniques could not. However, maintenance limitations in rugged terrain introduce further restrictions requiring adjustments to typical maintenance protocol to ensure the continued serviceability of the subject line. The lessons learned from the forensic investigation help develop recommended quality control procedures that may be used to ensure problematic spans are identified early without serious interruption to construction.