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The Danger Tree Locator (DTL) feature in PLS-CADD was originally developed in 2002 in cooperation with British Columbia Hydro (BCH). British Columbia Transmission Corporation (BCTC) took over responsibility for management of the BC transmission system after this project was started and many of the people involved are now at BCTC. BCH was looking for a safer, more reliable and less costly alternative to existing vegetation management procedures. They were interested in identifying danger trees that were too close to their wires and trees that could contact the wires if they were to fall. Existing procedures relied on field personnel “guesswork” predictions for wire positions under maximum operating temperature and high wind. Inaccuracies in these guesstimates result in failure to cut danger trees and or excessive cutting of non danger trees. Their goal was to perform a LiDAR survey to collect points along wires and trees and then feed this into PLS-CADD for accurate danger tree classification. PLS-CADD would be responsible for predicting wire positions under different combinations of wind, ice and operating temperature. PLS-CADD would then compare these wire positions against the surveyed tree points and identify those that were too close to the wires. The project was a success with BCH personnel declaring "the LiDAR/PLS-CADD system is the best thing to hit transmission vegetation management since the chain saw". For more background on BCH's experiences please see the related articles published in Transmission & Distribution World listed at the top of this page.
Sample PLS-CADD plan & profile sheets with danger tree graphics (courtesy of BC Hydro)
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![]() Grow-in and falling tree violations in 3D view
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![]() Grow-in and falling tree violations in plan & profile sheet view with optional plan grid to make measuring violation offset from centerline easier
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![]() Grow-in and falling tree violations in plan view with wire displayed in hot position
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![]() Falling tree violations displayed in cross section view with wire in hot position
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Isolines are polylines that connect points of equal value. Ground elevation contours are isolines where the points along the lines have the same ground elevation. Isoclearance lines are similar but the points all have the same distance to the closest wire rather than the same elevation.
Wire position varies with wind, ice and temperature. PLS-CADD can generate isoclearance lines for any given combination of wind, ice and temperature and can also generate a composite isoclearance line representing the worst case clearance to a range of up to 100 different wind, ice and temperature combinations (same assumptions as in Danger Tree Locator shown above).
We developed the isoclearance line feature in 2004 after discussions with Bryan Hooper of British Columbia Transmission Corporation. Bryan introduced us to the concept of the isoclearance line and explained how to use them to identify different areas of interest. The areas include:
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