QUANTIFYING TREE RISK TO IMPROVE RELIABILITY

What would it be worth to you to reduce tree-related outages by 50%... in avoided storm damage repair costs, in avoided regulatory proceedings, in avoided revenue losses, in customer relations and
retention?

Do you currently know the level of risk your electric lines face due to trees? If you could quantitatively assess the tree risk for each line you would have:

• a means for progressive reliability improvements
  
• a means of setting specific, acceptable, residual tree risk levels
  
• a basis for prioritizing investment to maximize reliability gains and minimize losses
  
• a means of illustrating to regulators the need for and prudence of line clearance maintenance decisions and funding
  

Increasingly regulators are setting minimum reliability standards. They are also questioning the influence of past maintenance practices when major storm-related outages occur. Many jurisdictions are moving to or considering performance-based rate making.

As long as there is an overhead system the risk of major weather-caused service disruptions exists. Frequently most of the weather related outages are actually caused by trees and branches falling onto lines. I'd like to introduce you to a new approach that can effectively manage this risk.

What percentage of unplanned outages are due to trees? Frequently it's 20% to 50% and that excludes the outages caused by major storms. While trimming trees is important for public safety it really has little impact on reliability. Tree-related outages arise from trees and branches falling on the line. The majority of these tree-related outages stem from trees located beyond the right of way and are generally categorized as non-preventable. If it's important to you to improve reliability, you need to address these "non-preventable" outages. Outages arising from tree and branch failure are preventable. Most utilities have a hazard tree removal program but have no means of forecasting the return in improved line security. And in fact, in most cases there is very little return. I'd like to introduce you to a new approach to managing tree-related outages that creates a quantitative basis for progressive reliability improvements and explains where and why hazard tree programs fail to significantly improve reliability.

If you are interested in substantially reducing tree-related outages, including those arising during major storm events, you need this new quantitative approach. You can capture the

benefits through purchase of an Optimal Clear Width Calculator subscription. Because this new approach provides a location specific quantitative measure of the risk of tree-conductor contacts, it allows for progressive, sustainable improvements in reliability. It provides a concrete means of reducing tree-related outages, educating stakeholders, demonstrating why you need a specific clearance, and protecting your company. If you are working to storm proof the system, the Optimal Clear Width Calculator will allow you to determine where your buck can get the biggest bang in increased line security.

Need more information on the Optimal Clear Width Calculator and the Line Strike Probability Charts? Get the technical paper now... it's titled Managing Tree-Conductor Conflicts by Risk Assessment … and it's free. For other papers on the applications of the Optimal Clear Width Calculator go to the Utility Arborist Association web site or use the following shortcuts--here and here. Be forewarned, the latter two are very technical articles but if you are trying to get a handle on tree-related outages or how to avoid extensive tree-caused outages during major storms these articles represent the current state of knowledge from the vegetation management side. The paper on the National Grid Transmission project establishes that tree exposure risk explains over 99% of the tree-related outage frequency. This has major implications for distribution systems and the extent of reliability improvements available through engineering options such as sectionalizing.

You can get pricing and ordering information for the Optimal Clear Width Calculator here.