Mark McGranaghan and Sandy Smith
Deregulation has increased the need to understand the expected reliability and power quality characteristics of utility power systems. This information must be developed through monitoring programs that characterize system performance. The benchmarking results can then be used to establish minimum performance guidelines for the system. This is already being done in the reliability area and many utilities around the world are using the same approach to define minimum power quality requirements. Now, power quality monitoring systems are being expanded to provide increased value by helping to actually improve overall system performance. These monitoring systems are being integrated with system operations and reliability-centered maintenance programs to operate and maintain the system more efficiently and reliably.
For years, power system, or power quality, monitoring was a reactive measure implemented as needed to identify and characterize problems occurring on utility and customer power systems. Monitoring is still done for this purpose; however, the changing nature of the utility industry, coupled with advances in technology, has moved monitoring to the point where it is part of a utility’s standard operations. There are a number of factors behind this trend:
“-Benchmarking existing power quality levels. Benchmarking expected power quality levels has been a key focus for a while, starting with the EPRI Distribution Power Quality project benchmarking distribution power quality in the United States. Many utilities followed with their own benchmarking projects to measure localized power quality. Similar projects have also been conducted in other countries. These efforts resulted in an understanding of expected base power quality levels that can become the basis of reliability performance contracts and premium power services.
“-Standards. The concept of power quality performance standards is becoming more prevalent at the international level and there is a strong likelihood it will move in that direction in North America. Europe maintains standards for minimum power quality levels that utilities must provide (EN 50160), as does South Africa. Argentina has a standard defining utility power quality and many other countries in South America are working towards similar standards.
“-Power quality performance contracts. Utilities serving the “Big Three” U.S. automakers have implemented electricity supply contracts including power quality considerations — i.e., interruptions and voltage sags. These contracts involve benchmarking expected power quality and guaranteeing this level of performance. Other utilities are implementing contracts incorporating enhanced power quality offerings. Monitoring can not only establish the benchmark performance, but also aid in the administration of the contract.
“-Customer information service. Many customers with equipment sensitive to power quality variations are interested in their characteristics so that they can evaluate equipment performance and determine if ride through or protective devices are needed. Utilities offer monitoring of customer sites as a service for these critical facilities.
“-Prioritizing system improvements based on problem impacts. Utilities traditionally prioritize capital expenditures and system maintenance based on solving problems and handling system growth. These expenditures are also related to maintaining an acceptable level of reliability. Prioritizing expenditures based on customer costs focuses on the objective of achieving high customer satisfaction, critical in a competitive market. Understanding the impacts of power quality variations on customers requires monitoring with follow-ups with the customer to assess the impacts.
“-Implementation of preventive maintenance systems and programs. Monitoring can identify problem conditions throughout the utility power system before they cause widespread customer complaints and equipment malfunctions and failures. Examples include resonance conditions causing localized harmonic distortion problems, breaker problems causing restrikes during capacitor switching, arcing conditions due to bad connections and cable insulation problems, fault performance problems resulting in voltage sags and interruptions, and grounding problems resulting in stray voltages and neutral problems. Monitoring key points on the utility power system can aid in implementing a system for preventive maintenance.
Trends in power system monitoring
Utilities have been investing in portable power quality monitoring equipment for many years to investigate “spot” power quality concerns. As the need for continuous monitoring has increased, many manufacturers introduced permanent power quality monitors for application at substations, distribution feeders, and within customer systems.
The technology to implement power monitoring has radically changed with the rise of the Internet. Traditionally, data had to be downloaded for analysis, a painstaking process. Many manufacturers have now incorporated Ethernet capability into their products, enabling instruments to be downloaded using the Internet and the data viewed and analyzed using the Web. In addition to speeding the process, this is especially useful because multiple users can access the data with no software to use beyond an ordinary Web browser. (Electrotek pioneered the web-based monitoring through early cooperative research with DOE, and it is now becoming the industry standard.)
Because utilities frequently use instruments from different manufacturers, there is significant interest in open systems allowing different equipment to work side by side. Virtually all equipment manufacturers have proprietary software for downloading instruments and analyzing data. Many of these programs use file formats incompatible with one other, making integrated analysis of collected data problematic. This led a move towards a common data output format–the Power Quality Data Interchange Format (PQDIF) being finalized by IEEE (http://grouper.ieee.org/groups/1159/3/). Application of industry standards like PQDIF allows the implementation of advanced analysis systems and database management systems, increasing the value of the overall monitoring system.
Many utilities move beyond power quality measurements in their analysis of system performance. Some utilize details on the cause of a fault, or the circumstances behind an event. End user impacts in terms of the type of equipment dropping offline during an event, or cost due to the disturbance, can also be included to help determine where investments in the power system would provide the greatest benefit. Many utilities are integrating power quality monitoring information with operational data recorded by their SCADA systems.
Many instrument manufacturers offer software to acquire and analyze collected data. The latest generation of this software incorporates advanced technology to analyze the data and provide detailed answers ranging from diagnosis of power quality problems to recommendations on predictive maintenance. This trend holds the most potential in a deregulated market. Many equipment manufacturers have implemented notification and alarming capability enabling a page or e-mail to be sent when events occur.
The ultimate goal of power system monitoring is to help improve the performance of the power system by identifying problems more quickly; helping to prioritize maintenance expenditures, and helping customers deal with power quality issues more effectively. The monitoring system can help a utility realize substantial savings in operation and maintenance costs while also improving overall system reliability.
Power system monitoring has come a long way. The shift from troubleshooting to predictive analysis and performance assessment is helping ensure faster response to problems while realizing better use of resources and savings. The emergence of “smart monitoring” offers even more potential. This provides tremendous benefit in an industry where employees all too often have to do more with less.
McGranaghan is vice president of marketing and sales and Smith is marketing communications manager for Electrotek Concepts, Knoxville, TN. McGranaghan and Smith may be contacted at 865-470-9222 or e-mail firstname.lastname@example.org or email@example.com. For more information on this topic, visit www.powermonitoring.com.