Ecosync
Outage Statistics As a Basis for Determining Line Clearance Program
Status. Guggenmoos, Siegfried
Abstract:
Outage statistics are the most meaningful measure of the success or failure of
a line clearance program. Using vegetation inventories as a basis for modelling
budget impacts on future outages and budget requirements represents a powerful
tool for securing adequate funding. The combination of outage history and
predictions can be used to demonstrate due diligence, thereby managing the risk
associated with tree-conductor contacts.
Outage statistics are the
most meaningful measure of the success or failure of a line clearance program.
They are a powerful tool for assessing current program status and can provide
an indication of future trends. Outage statistics provide information about how
the tree inventory changes and this, in turn, can be used to make economic
forecasts.
Why do we clear trees from
around energized lines? The standard answer is to increase reliability and
safety. Reliability is a quality of service issue. Quality of service is
measured by the customer, not by company programs and initiatives. Will
reliability be more or less important in a deregulated electric industry, where
the customer has a choice in suppliers? In a 1993 survey, TransAlta Utilities
(TAU) customers were asked to rate twenty service factors in terms of
importance and how they perceived TAU's performance on each of these.
Reliability topped the list in importance at 98.8%. Cost was sixth.
Providing safe service in
this litigious age, is managing a liability. Each tree-conductor contact holds
the potential for human exposure. I believe the associated risk is greatly
underestimated by utilities. If CEO's and directors were cognizant of the
unavoidable personal liability they assume for tree-conductor conflicts,
utility foresters would be struggling to exceed industry standards rather than
arguing for a budget based on a tree inventory.
The personal liability of
directors is illustrated by the fact a judge in London, Ontario imposed not
only heavy personal fines but also jail terms against directors and a senior
executive of Bata Industries Ltd. for the release of an environmental
contaminant. There was no associated death or injury reported. The judge
reasoned that it is the responsibility of directors to ensure the legal and
safe operation of the company. In this case, the two who had direct knowledge
of the pollution activity were given jail terms. And while it seems outlandish
that a jury would have McDonalds restaurants transfer millions of dollars to a
woman seemingly surprised to learn that coffee is sold hot, the implications of
a suit for damages against a utility whose product is admittedly potentially
lethal are frighteningly severe.
My thoughts on the
potential utility of outage statistics first coalesced in a struggle to salvage
TransAlta Utilities' Forestry or Line Clearance program as funding was cut.
What might studying outages yield? Using data from TAU we can explore if there
is a pattern to outages. Figure 1, which shows TAU's outage history in customer
hours lost for the years 1978 through 1984, suggests it may be exponential.
Figure 2 shows the budget through this same period. It too appears to be
increasing exponentially. In Figure 3, budget and outage statistics are
overlaid to determine if there is any apparent relationship between the two.
This chart showing both expenditures and outages expanding exponentially has
the potential to alarm management to the point of undertaking a whole new
course of action as was the case at TAU. It does appear that outages respond to
sharp budget increases though it may take more than a year for the result to
manifest.
Speculating about outages
we would anticipate if the right amount of money was spent, that is the budget
were linked to a tree inventory, we could expect outages to drop and
equilibrate at a new, lower level. This new level would reflect operational and
environmental factors such as: tree inventory; the clear distance; tree species
characteristics; environmental factors such as weather events; insect and
disease damage. The outage history at TAU confirms this speculation (Figure 4).
From 1992 on budgets have been increasingly divorced from the inventory and
outages are increasing.
In categorizing the factors
affecting the number of tree related outages, we find clear distance is the
most important since it is the only factor we control (Figure 5). While nature has
provided a certain tree density, clear distance dramatically impacts the
inventory capable of striking the line and hence outage probability.
We used outages for making
program choices at TAU. Faced with budget reductions in 1992, prior to the
completion of the first cycle, we wondered if we should simply hotspot the
untouched areas until such time as the budget shortfall was rectified. We
concluded the hotspotting would increasingly draw resources away from the
maintenance grid eventually sinking the whole program (Figure 6).
Outages and budget are
linked through inventory. The potential impact of underfunding the program has
also been assessed (Figure 7). While the impact of underfunding a program is
not very perceptible for a few years, the budget required to return outages to
the low equilibrium level is quite significant and begins to show after five
years.
Creating hypothetical
situations for TAU permit a revealing economic comparison. In the first case
(Figure 8) we assume the utility links the budget to the tree inventory. This
requires a temporary but substantial increase in budget. Outages drop and level
off at about 20,000 customer hours. In the second scenario (Figure 9), we
assume TAU's budget was frozen at the 1985 level. Outages increase and will of
course eventually level off. At the end of 12 years, outages are in excess of
300,000 customer hours.
Comparing the dollars
invested in line clearance and placing a value on the residual inventory after
the 12 years we find in present value terms, the program with the budget linked
to inventory cost 18.5% less. We could also say the program based on the
inventory has an internal rate of return12.5%.
With returns like that,
perhaps there is a ray of hope for line clearance programs. Use of outage
statistics may get you the attention you need and deserve for your program.
Figure 1 Figure 2
Figure 3 Figure 4
Figure 5 Figure 6
© ECOSYNC 1995
Figure 7
© ECOSYNC 1996
Figure 8
© ECOSYNC 1995
Figure 9
© ECOSYNC 1995
______________________________________________
About the author:
Siegfried Guggenmoos, B.Sc.(Agr.),
P.Ag. holds a degree in agriculture with a horticulture major from the University
of Guelph, Ontario. He has been involved in research on growth regulators and
herbicides; was the general manager of one of Canada's major vegetation
management contractors; Supervising Forester at TransAlta Utilities, 1985-1995,
designing, implementing and assessing vegetation management programs and
contracting methods; currently president of Ecological Solutions Inc.
(Ecosync), Sherwood Park, Alberta.