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Weir J.A.,Technical Services and Research
EIC 2014 - Proceedings of the 32nd Electrical Insulation Conference

Road salt spread on highways during the winter months can be a major source of contamination for insulators. Once the salt is spread on the highway, it becomes airborne through vehicle traffic and wind. The wind may then deposit the salt onto nearby electrical apparatus increasing the risk of flashover. The standard method of assessing contamination on insulators is the equivalent salt deposit density (ESDD) measurement. To determine ESDD and its relation to distance from the highway, strings of suspension insulators were hung from power poles along a distribution line perpendicular to the road before the first snowfall and retrieved before the first rain in the spring; the retrieved insulators were then washed and the ESDD determined. According to an empirical formula, ESDD is a function of wind speed and direction, the amount of road salt spread on the highway and, as confirmed by the present experiment, the inverse distance from the highway. The data from the experiment were used to estimate the minimum distance between a proposed highway and a switching station to prevent excessive flashovers. © 2014 IEEE. Source

Sanders J.R.,Technical Services and Research | Grabosky J.C.,Rutgers University
Urban Forestry and Urban Greening

Urban conditions have been thought to affect tree growth, but there is little conclusive evidence as to the severity of those influences or how various species respond differentially to urban stress. Reduced growth expectations are important to understand, because they affect design choices for the urban tree canopy, particularly as required by legislative mandate. Five tree species (Acer rubrum, Prunus serrulata, Pyrus calleryana, Quercus pallustris and Zelkova serrata) grown in parking lots ranging from 18 to 23 years old in central and northern New Jersey, USA were studied. Tree height, diameter at breast height (DBH), and canopy radius were measured, as was apparent plant available soil (nonpaved planting zone area). Tree DBH, commonly recorded for many municipal inventories, was found to be a useful predictor of canopy area. Data were normalized within site, to facilitate multiple site analysis. Across different parking lots, reductions in tree size were consistently associated with reduced apparent soil access. A previous study from Florida, USA was used for comparison of regional data, permitting conclusions on canopy reductions, relative to specification of design space for tree establishment. © 2013 Elsevier GmbH. Source

Ghassemi M.,University of Quebec at Chicoutimi | Farzaneh M.,University of Quebec at Chicoutimi | Chisholm W.A.,University of Quebec at Chicoutimi | Beattie J.,Technical Services and Research
EIC 2014 - Proceedings of the 32nd Electrical Insulation Conference

Two clean live-line tool flashovers in Manitoba at 500-kV line voltage and two recent ones in Saskatchewan at 230 kV during freezing conditions led to extensive laboratory tests to reproduce some of these flashover conditions in a controlled laboratory environment to understand the underlying mechanisms and to assess mitigation measures. This paper improves on the three-dimensional finite element method model developed in our previous study to compute the potential and electric field along and around a fiberglass-reinforced plastic hot-stick in a series of 'true' cold fog tests at the UQAC. In the previous study, the simulations were carried out with a dry surface and non-uniform wetting. In simulating the non-uniform wetting conditions, since a non-continuous water film was considered to be on the hot-stick surface, there was no leakage current. However, in the flashover and cold fog tests at the UQAC, leakage current activities were observed between the HV and ground electrodes on the surface of the hot-stick. In the present study, the mathematical equations of the model were modified to allow for the presence of leakage current flowing through a continuous thin layer of ice on the surface of the hot-stick in freezing and cold conditions, as was the case for the flashover incidents experienced in Saskatchewan. The potential and electric field distribution along and around the hot-stick were calculated and compared with those in dry surface conditions. © 2014 IEEE. Source

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