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UBC Theses and Dissertations

Mapping and modelling the probability of tree-related power outages using topographic, climate, and stand data Hirata, Felipe Gunji


Trees routinely fall across electrical power lines during severe weather events interrupting the power distribution to residential and business customers. Electricity utilities are responsible for generating and distributing power to customers, and managing tree-related hazards adjacent to transmission and distribution lines. To clarify the circumstances under which tree-related outages occur, the relationship between outage frequency and various climate, topographic and stand attributes were investigated. These variables were then used to fit outage probability models using logistic regression. The first study modeled the probability of tree-related outages in the transmission grid across the province of British Columbia (BC) using climate and topographic data. The second study modeled the probability of tree-related outages in the distribution grid for the North Shore region of the BC Lower Mainland using climate, topographic, and stand data. Models for the province fitted the data quite well (c-values ranging from 0.74 to 0.77). The North Shore had the highest density of outages per length of circuit within the province. These local models fit the data less well than in the provincial study (c-values ranging from 0.62 to 0.63). Key variables selected by the models were MC2 average hourly precipitation, MC2 average hourly wind speed, MC2 top 5 events wind speed, BC Hydro annual average wind speed, elevation, ground slope, topographic exposure, crown closure, stand height, and stand age. Vegetation management plans should continue to reduce the risk of outages by eliminating hazard and danger trees from stands adjacent to power lines. The outage density and probability maps could be useful tools for locating circuits that are more susceptible to outages and in customizing local management and ROW design regimes.

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