E Source researches power quality benchmarking
Table of contents
What Is PQ Benchmarking?
Why is PQ Benchmarking Needed?
Establishing PQ Benchmarking
Benchmarking Objectives
Establishing Benchmarking Standards
Recent media reports of power outages, supply shortages, and difficulties encountered by deregulating markets have increased end users' awareness of power quality issues. Electric providers know that they need to refocus their efforts to maintain system reliability and enhance the quality of power delivered to their customers.
A July 2000 E Source report highlights this need. "Power Quality Benchmarking: Developing an Acceptable Baseline of Service" outlines how energy providers can ensure that they are meeting quality standards.
What Is PQ Benchmarking? (Back to top)
Power quality benchmarking is a process of measuring, analyzing and comparing power quality to ensure that an energy provider's objectives are being realized. The electric provider must clearly understand the various metrics that can be measured and how they are used to create benchmarks for sags, surges, transients, harmonics, flicker, and other transitory and long-term power quality issues.
As the study states, the most important factor when establishing power quality benchmarking is an understanding of the benchmarking program's objectives. These objectives can range from documenting current system performance to providing comparisons of multiple systems, helping troubleshoot customer problems, or providing for-fee customer information services.
Why is PQ Benchmarking Needed? (Back to top)
Improving the quality of power delivered to end users and controlling the costs of the services is an important way for energy providers to maintain competitiveness. Many energy providers previously found benchmarking a costly undertaking. But in today's competitive environment, they are focusing on quick and cost-effective power performance data to measure their quality levels.
As utility deregulation and restructuring continues to grow internationally, power providers and consumers are modifying their definition of acceptable electrical system performance. According to the report, the definition of acceptable level of service is complicated by many issues, such as the costs of providing service where climate, geography, system design, and load density varies. These variations can exist within a single energy company's service area, leading to varying costs to provide a particular level of service to different customers. Because of these issues, many energy companies believe that establishing minimum performance levels is unreasonable.
However, many energy providers see the need to establish minimum service requirements for customers such as hospitals, military bases, and schools. As industry restructuring continues, many energy companies are likely to discover that they have no choice but to establish minimum service standards due to public utility commission requirements. By implementing PQ benchmarking standards now, these energy companies are better positioned to respond to new regulations governing PQ service levels.
Establishing PQ Benchmarking (Back to top)
According to the report, in order to implement PQ benchmarking, the following four basic steps are needed:
- Selecting benchmarking metrics. To begin the benchmarking process, metrics must be defined for benchmarking and evaluating service quality. To select the metrics, the energy provider determines which PQ variations to consider in the quality assessment, as well as the quantification methods for determining "performance." The metrics may be estimated quantities that are calculated based on historical data, such as faults per mile of line. However, many providers have become more interested in metrics that focus on actual performance for a given time period.
- Collecting power quality data. After determining the metrics, the next step in benchmarking involves collecting the data needed to calculate the chosen metrics. The data collection process can be very costly and cumbersome, involving significant capital investment for equipment and labor investment for maintenance of the collected data.
- Selecting the benchmark. The benchmark may be based on the provider's own past performance, a standard adopted by a comparable provider, or a standard that a professional entity, such as IEEE, establishes.
- Determining target performance levels. After the data have been collected for the selected quality metrics and a benchmark has been selected, the service provider must determine what levels of quality are appropriate and cost-effective for each metric. More often, energy companies make the decision based on input from their specific customer, public utility commissions, or regulatory bodies.
According to the E Source report, utilities undertake benchmarking for several reasons. The primary reasons are to understand their distribution system's performance, support customer information and services, or develop systems that anticipate and prevent unwanted levels of PQ variations in the future.
In order to understand system performance, energy companies use benchmarking to complete the following tasks:
- Compare performance at various intra-company sites. Providers may undertake PQ benchmarking to understand how their distribution systems are performing in terms of numbers of sags, outages, and challenges their systems experience each year. They also seek to identify feeders that need to be upgraded.
- Compare performance among various providers. The EPRI Distribution Power Quality project monitors PQ levels at 300 locations on 24 different distribution systems in the United States. The results allow energy companies to compare their levels of sag and outage with national baseline levels.
- Support standards efforts. A few energy companies have measured PQ variations to develop their own internal PQ standards; in some cases, other energy companies ultimately adopt these benchmarks.
- Provide economic evaluation of PQ solutions. Energy companies need to justify the cost of PQ solutions to end users. Even though many customers have experienced equipment problems due to power quality variations, they are often unwilling to pay for solutions. Benchmarking allows energy providers to educate end users on the effect of PQ variations.
- Troubleshoot customer equipment problems. Benchmarking data provides solutions to PQ problems, either by allowing troubleshooters to link events on the grid with abnormal equipment behavior, or by eliminating the provider as the cause of the problem. Both the customer and end user benefit from an enhanced relationship, reduced labor costs, and more efficient problem solving.
- Support performance-based contracts. PQ benchmarking provides data that can ensure that performance standards issued in contracts are reasonable and achievable. Additionally, benchmarking data helps verify compliance, calculate penalties or bonuses, and settle disputes between parties.
- Provide premium power services. Premium power services include installation of technology or other system improvements to bolster reliability. Many energy companies have installed monitoring systems to benchmark performance so that the information provided to customers as part of PQ contracts can help them understand the power quality variations that affect their equipment. Monitoring and benchmarking are important to justify premium power services to end users and to document the benefits of the services.
Establishing Benchmarking Standards (Back to top)
Many providers are implementing PQ measurement and benchmarking standards to establish overall system performance. The information collected establishes baseline levels of power quality that can be used to assess the performance of individual substations and to offer enhanced services when baseline performance levels are unacceptable for customers.
According to the E Source report, South African energy company ESKOM, which was interested in understanding the quantity and length of voltage sags, began an in-depth benchmarking project to characterize system performance. The company used benchmarking results to define limits for acceptable numbers of voltage dips per year, depending on the end user's network voltage range. ESKOM's results were adopted as the standards for power system voltage sag performance nationwide—making South Africa the only country in the world with actual sag performance standards.
As energy deregulation continues to spread throughout the world, PQ benchmarking will become increasingly critical for those energy providers that seek to lead the competition. Customers' needs demand that energy providers initiate standards that minimize power problems. To entice these customers, energy providers must develop cost-effective methods to ensure the quality of their services.
This article is based on research findings published in the E Source report "Power Quality Benchmarking: Developing an Acceptable Baseline of Service," by Daniel L. Brooks and Bill Howe, PE. The report is available exclusively to subscribers of E Source's Power Quality Series and the PQ Group (an E Source and Electrotek alliance). For more information, please contact E Source (www.esource.com). In June 1999, the Financial Times Group (www.ft.com) a division of Pearson plc, acquired E Source.
Steve Hoffman is President of Hoffman Publications, Inc. (www.hoffmanpubs.com), a California-based firm that specializes in writing for the energy industry. His column appears every Monday on ElectricNet. (Back to top)