INMR: January/February 2001 : Utility Develops Insulator Washing Program Based on Contamination Monitoring

Utility Develops Insulator Washing Program
Based on Contamination Monitoring

Washing insulators, whether on overhead lines or at substations, is almost always an expensive undertaking. Therefore, washing conducted solely on the basis of some regular time schedule and without regard to the actual contamination levels on the insulators opens up the possibility of two types of risk. The first is the risk that washing is done too late to prevent flashovers due to unusually severe contamination build-up since the last washing. The second type of risk, less serious, is that washing is undertaken when not strictly needed, meaning unnecessary maintenance expenses.

In the following article, based on the Presentation given at the 9th ESMO Conference, Dr. William Chisholm of Kinetrics and Tom Kydd of Hydro One explain how Hydro One (formerly Ontario Hydro) has developed criteria which guide the timing and methodology for insulator washing at its substations, especially during the problematic winter months.


William Chisholm looks over post insulators being tested at Kinetrics to compare different insulation enhancement treatments under icing conditions, especially when stations are located near to expressways.

Experience at some important substations in the Hydro One (formerly Ontario Hydro) network has demonstrated that contamination-related flashovers of both station and line insulators can be particularly severe during the winter months. In many instances, road salt deposited on highways passing close to stations has been a major contributor in this regard. Several 115 kV and 230 kV stations have been especially susceptible to this problem over the past ten years. Therefore, a variety of remedial actions have been taken as part of a multi-million dollar program to improve winter flashover performance at these stations (see INMR Vol. 8 No. 6 page 22).


	Hydro One substation lies adjacent to major expressway. Fence has only limited effect in preventing highly conductive particles from winter salting being thrown into the switchyard by motion of passing vehicles.

At the same time, Hydro One has discovered that the 1550 kV BIL insulators selected during the 1970s for its 500 kV stations have been unexpectedly sensitive to flashovers due to winter icing. Conditions found to be most serious in this respect are two or more weeks of freezing weather followed by a thaw with either light freezing rain or cold winter fog.

The development of condition-based ‘Smart Washing’ in a co-operation between the utility’s Research Division (now a separate organization operating under the name Kinetrics) and Hydro One’s Operations and Maintenance Department has proven to be extremely valuable in dealing with this winter icing problem. At the same time, it has allowed the utility to postpone (in some cases indefinitely) further costly insulation upgrades at its more problematic stations.