For the past five years, the Independent Electricity System Operator (IESO) in Ontario has expressed concerns about limitations in the ability to transfer power from the Niagara Falls stations to the west, towards Hamiltion, Ontario. Capacity of this interface falls when the wind speed across the conductor drops below 2 m/s. Plans are underway to supplement five existing parallel 230-kV transmission lines with two more circuits. However, in the meantime, Hydro One also initiated some of the most advanced studies of overhead line clearance ever reported. This work used helicopters to perform laser surveys of the conductor position, sonar to measure the conductor height and new algorithms to turn the traditional rating calculation inside out - by reading out the average wind speed along the entire line, rather than relying on the average of a few data points measured far away at airports.

William A. (Bill) Chisholm managed the research and development aspects of this project, that started in 2001 and ended in 2005 with commissioning of permanent clearance observation sites. He is a Principal Engineer at Kinectrics, the former Ontario Hydro Research Division and now a subsidiary of AEA Technologies PLC. He graduated in Engineering Science from the University of Toronto in 1977, received an M.Eng in 1979 and completed a Ph.D. in Electrical Engineering at the University of Waterloo in 1983. He has twenty-nine years of research background in lightning protection, icing and thermal rating of transmission systems. He is a Senior Member of IEEE, member of Conductors panel sessions at the previous two IEEE-PES meetings and a member of the joint IEEE/CIGRE Task Force B2.12, "Weather Parameters for Bare Overhead Conductor Ratings".