hihi ivmaa - march 2005 lessons from the ice storm of 1998 in québec (from bérubé roger and c....
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IVMAA - March 2005
Lessons from the ice storm of 1998 in Lessons from the ice storm of 1998 in QuébecQuébec(from Bérubé Roger and C. Houde
August 3, 2003)
François Gauthier, f. eng., M. Sc.
Environmental project leader
Hydro-Québec TransÉnergie
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A historic stormA historic storm
The climatic event of the century in Montreal area
Occurs once in 450 years
Duration of 80 hours vs an average of a few hours (12 – 17 times a year)
100 mm of ice vs 40 mm in 1961 25 mm in 1997
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A heavy impactA heavy impact
A major impact on our customers January 5, 1997 ice storm
180 000 customers January 5, 1998 ice storm
1 400 000 customers
Thousands of trees destroyed or damaged
1600 repair crews from a hundred companies (600 pruning) for over a month
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Ice storm impactIce storm impact
Especially a vegetation management Distribution problem
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Service Interruptions – Jan 97 vs Jan 98Service Interruptions – Jan 97 vs Jan 98
(number of customers)
-
500 000
1 000 000
1 500 000
5 6 7 8 9 10 11 12 13date
Jan 97 Jan 98
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DiagnosisDiagnosis
Causes of distribution network failure:
Design specifications exceeded (54 %) (zones of low density vegetation) Issue: More robust network
Falling trees and branches (46 %) (zones of medium and high density vegetation) Issue: Controlling vegetation
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Hydro-Québec orientationsHydro-Québec orientations
Restore service in less than a week for most customers
Be able to handle an ice storm that recurs once in 100 years
Make priority lines more robust
Optimize solutions between Transport and Distribution
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A robust networkA robust network
Reinforcement program
Zones > 45 mm of freezing rain (100 years prob.)
Raise design criteria on priority lines
Failure sequence: Wire detaches Cross arm detaches Pole breaks
Emergency plan
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Controlling vegetationControlling vegetation
Trees increase network vulnerability to climatic extremes
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Controlling vegetationControlling vegetation
Effects of climate
Wind: Wind strength increases by the cube of wind speed
An 80 km/h wind is 8X stronger than a 40 km/h wind
Ice: Weight of ice increases by roughly the square of its thickness
25 mm of ice is 25X heavier than 5 mm
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Controlling vegetationControlling vegetation
Key facts
Falling trees and branches largest cause of outages Average of 50 %
Similar impacts of freezing rain, strong wind and wet snow
Vulnerability to less severe freezing rain Damage to trees starts at 15 mm Systematic damages from 25 mm
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Controlling vegetationControlling vegetation
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Controlling vegetationControlling vegetation
Actions targeted Cut overhanging branches
Urban mostly Remove hazardous trees
Urban and forested Priority according to
Probable thickness of iceStrategic importance of lines
Better diagnostic of problem trees
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Controlling vegetation – Forested areasControlling vegetation – Forested areas
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Controlling vegetationControlling vegetation
Can tree-related outages be prevented ? Over 80 % caused by falling trees and
branches Species
Aspens, birchs, fir, silver and red maple 66 % of outages preventable 75 % acceptance by customers
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Controlling vegetationControlling vegetation
Budget increased fron 23 to $40 million/yr in distribution 100 000 tress cut or overhang removed per year
Planning improved Including vulnerability reduction objectives
Skills reinforced Team of internal specialists hired
Effects on contractors More stability ISO 9002 required
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Controlling vegetationControlling vegetation
Agreements made with municipalities Shared objectives
Management Information improved Cost control
ISO 14001 applied to operations Agreement of owners required
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Conclusions for vegetation managersConclusions for vegetation managers
Distribution network:
Plant the right tree at the right place
Do the required maintenance on trees
Plan for the improbable
Don't hesitate to call for help when needed