Optimized line design in a deregulated world
Fred A. Brown, PE President & Chief Executive Officer LineSoft Corporation 12310 East Mirabeau Parkway Spokane, WA 99216 Telephone: (509) 928-1707 Fax: (509) 928-2581 E-mail: fbrown@linesoft.com Introduction Deregulation has presented utilities with new challenges, and to win, these service providers must focus on reducing the total cost of power line design, construction, and maintenance without sacrificing performance, reliability, or standards. The way to reliability, best cost, and compliance in line design is down the path of optimization. Optimization first requires an evaluation of practices throughout the business, particularly by those in the engineering environment, where the job of the line designer demands advanced tools, technical expertise, and creative energy. Although design optimization involves improved tools, it is above all a process change. This new approach requires an objective comparison of traditional "rules of thumb" with new engineering procedures in light of company objectives. Energy delivery to customers is the top priority. Regulatory compliance and adherence to company standards are obligatory. The crucial new factor is the addition of best-cost procedures to the mix of delivery and compliance. With the aid of powerful and efficient design and spotting software, engineers can evaluate the impact of the hundreds of factors that affect the cost and performance of electric lines. Software technology now provides designers the tools to quickly and precisely investigate a variety of options and identify the combination best suited to a given situation. In short, the automation solution becomes a natural extension of the engineer's design process, stimulating new ideas and enhancing creativity. Changing the established system within a utility or any other business is a challenge. At the utility, success requires that Management, Engineering, Standards, Information Services, and Construction departments work together toward clear and common goals. The incentive is real and attainable; millions of dollars can be saved each year using optimized design practices. Success requires new tools, solid design skills, and a shift in focus from today's practices to a new engineering approach to power line design. The optimization process The basic optimization process is simple. A designer wants to get power from point A to point B at the best cost and within the bounds of safety and performance criteria. Many factors affect the cost, safety, and performance of a power line. Some factors are within the designer's control and some are not. The designer must recognize which factors can be manipulated to his or her advantage. It is then a matter of identifying the optimal combination of variables that take the fullest advantage of the terrain and other constraints. Line design and structure spotting are historically laborious, complicated tasks. Designers have not had time to thoroughly consider what-if scenarios. With the advent of optimization software and the analysis it affords, a designer can now identify and track the cost of each design decision. After each optimization effort, the designer can determine which factors are limiting the design. The designer can then manipulate the variables over which he or she has control and re-spot the line. No one can foresee how the complicated interrelationship of variables and terrain will come together and affect the spot. Intuition and experience can help, but it is still a trial and error process. Historically, utilities have limited the variables available to the designer and applied a series of "rules of thumb" to the process. Sometimes these standardized rules are based on sound engineering judgement. Sometimes they are not. There are valid reasons for standardized materials and practices, but in today's competitive environment, there are vital business reasons to rethink established practices and consider creative solutions. Optimization process factors No two power line installations are the same. Differences in terrain, wire size, environmental loading, routing constraints, and other factors require that the designer consider each line as a new challenge. Cost and reliability of any line are affected by basic factors that can be evaluated and modified. Some concepts that should be considered during every overhead line design include:
Viewing the line as a system increases the potential for the greatest cost savings. All variables within the designer's control (from construction materials to conductor tension to allowable span lengths) should be synchronized with the terrain and constraints outside the designer's control. This is often overlooked in day-to-day line design. If span lengths are limited to 200 feet for other reasons, ten-foot crossarms that allow 400-foot spans under galloping conditions are unnecessary, costly, and of no benefit to the system. Common reasons for not optimizing distribution lines Distribution lines are notorious for exhibiting constraints not seen in transmission line design. Some feel these constraints are so great no benefit can be gained by optimizing. This is not the case. There is always something the designer can do to reduce the cost below standard "rule-ofthumb" designs. The standard objections to the value of optimization and our response to these objections follow:
Optimization results This paper focuses on the big picture of optimization. The discussion targets the mental attitude and iterative design process needed for optimal designs. This is because the utility can gain limited improvement without rethinking the design process. It is important to understand the magnitude of potential cost savings. This section demonstrates real-world results of the optimization process. LineSoft has conducted several pilot projects at different utilities to demonstrate optimization results. This section summarizes typical results of distribution and transmission pilot projects conducted at 2 large U.S. utilities. Similar results were achieved at the other utilities evaluated. The goal of these studies was to demonstrate hard-dollar savings in construction, labor, and material. Additional benefits of the optimization process, such as savings in design time, design consistency, code compliance, and process improvement, occurred as well. Distribution pilot study process The pilot study randomly selected large distribution work orders constructed during the previous year. The projects ranged from 12.47kV to 24.9kV, and each consisted of 15 to 39 poles. LineSoft personnel worked alongside the original utility designers to redesign and optimize each work order. All constraints faced by the original designers were discussed and included in the optimized design. Such constraints included fixed pole locations (for taps, customer agreements, access, etc.), prohibitive zones where structures could not be placed (roadways, driveways, railroads, etc.), transmission crossings, and joint use considerations. The random jobs selected represent a cross section of work orders of this size common throughout the utility's service territory. The projects considered in the study are:
Additional jobs were evaluated with similar results. Because of space limitations, we have included only these three projects. Distribution Pilot Study Results The table below summarizes the labor and material cost savings demonstrated for the example work orders and the methodology used to obtain the savings. All costs are based on the utility's standard labor and material costs. Costs shown include all material and labor costs associated with the work order. Transfer and removal of existing poles, conductor, and equipment is included as well as installation of new structures and conductors.
The average savings was 15.9 percent. This was accomplished with more than 40 percent of the total number of structure locations fixed for various reasons. Transmission pilot study process The summary is based on various studies at utilities across the United States where projects were redesigned using LineSoft's LD-Pro for transmission line design. All projects were subject to the same design constraints as the original project. These spotting constraints include items such as road and railroad crossings, span limits due to right-of-way limitations (blow out), wetlands, customer agreements, guying limitations (self-supporting structures), etc. In some studies, several designs were considered by manipulating conductor tensions, pole types, insulator types, and framing configurations. Each work order was entered into LD-Pro as designed and analyzed for standards compliance. To ensure accuracy, LD-Pro's total cost output was compared with the original work order design and cost. As with the distribution examples, we have included a representative sample of transmission jobs.
Savings on transmission line design jobs ranged from 13 percent to 20.4 percent. Conclusion The winning utility will successfully optimize line design. It is possible to reduce the total installed cost of transmission and distribution lines while maintaining or even increasing the performance and reliability of the line. This requires a rethinking of the entire design and construction process. However, with millions of dollars at stake every year, the benefit is evident. It's time to bring the old "rules of thumb" under close scrutiny and start embracing new engineering practices. The technology is available and the payoff enormous. The return in the first year alone can easily make the cost of implementing the technology insignificant. All it takes are the tools, the skills, and a focus on optimized, sound engineering approaches to power line design. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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