Mark McGranaghan and Daniel Sabin
As it has with so many other aspects of the utility industry, deregulation has changed the fundamental premise of monitoring and managing power quality. Traditionally, power quality monitoring was conducted on a case-by-case basis at customer facilities to identify problems and determine their cause. With customers now able to select power providers (and with the evolution away from the vertically integrated utility), power quality has emerged as a criti-cal issue from the standpoint of customer retention as well as utility performance.
With customer equipment and processes becoming less tolerant to power system disturbances, resulting in downtime equaling losses of thousands and even millions in dollars, customers are weighing power quality and service reliability as high as they do price when choosing a power provider. In addition, the separation of utilities into different operating units and even competing companies has spurred a new level of interest in monitoring.
Sample utility power quality monitoring system
This situation has become even more visible with the emergence of the microprocessor-driven digital economy. The expansion of telecommunications facilities and computer-oriented customer loads such as data centers and server farms have compelled utilities to evaluate their ability to provide “high nines” power reliability as specified by these customers. Monitoring is now seen as a mission-critical activity for utilities to serve high-demand customers and improve operating efficiencies.
Why monitor power quality?
Monitoring provides a number of benefits to utilities as well as customers. Some of these benefits are exclusively found in that realm defined as the utility-side of the meter, some are found exclusively on the customer side. However, power provider and power user share similar benefits. These can include:
- Identification of problem conditions. Monitoring can identify problem conditions on utility and customer power systems before they cause equipment misoperation or failures and customer complaints. Examples can include resonance conditions that can cause localized harmonic distortion problems, breaker problems that cause restrikes during capacitor switching, and fault performance problems resulting in excessive voltage sags and momentary interruptions. In particular, there are customer operations-such as motor starting or the operation of arc furnaces in steel plants that can impact the customer, the utility and even other customers. Monitoring can help identify these conditions and direct utility and customer personnel to correct them.
- Prioritize system improvements. Utilities traditionally prioritize capital expenditures and system maintenance based on solving system problems and handling system growth. These expenditures are also related to maintaining an acceptable level of reliability. A more customer-driven approach to prioritizing system expenditures is based on customer costs of system disturbances. Prioritizing expenditures based on end-user costs has the objective of achieving the highest level of customer satisfaction. Such an objective is particularly important in a deregulated business environment. Understanding the impacts of power quality variations on customers requires monitoring along with follow up with the customer to assess the impacts. More and more utilities and customers are also using monitoring for predictive purposes to help determine when equipment needs maintenance or repair.
- Assess overall performance of utility and customer power systems. This becomes important as utilities and customers move towards power supply contracts that specify a certain level of service reliability. An ongoing monitoring regime can enable power providers and users to assess system reliability under a wide range of conditions, including market volatility, weather conditions, and utility and customer operations.
- Determine effectiveness of system maintenance activities and power conditioning technologies. For utilities, monitoring can help determine the effectiveness of measures such as tree trimming and expansion of the distribution system. Forcustomers, monitoring can verify the performance of ride through measures such as UPS systems and backup generation or power conditioning technologies such as harmonic filters. Many utilities, especially through their unregulated subsidiaries, are working with customers to implement mitigation measures to improve power quality. Monitoring is an essential component of the customer care process for this business.
While many of these benefits have long been recognized by utilities, the increasing attention by customers to power quality has leant them a greater prominence in both customer service and system operation activities.
The changing nature of monitoring
Over the past few years, a number of trends have emerged that impact not only how utilities conduct power quality monitoring, but also how they perceive the role of power quality monitoring. Chief among these are changes in the use of power quality monitoring data. Beginning with the EPRI Distribution Power Quality (DPQ) study managed by Electrotek Concepts (where locations at 24 utilities located throughout the United States were monitored to determine power quality performance), utilities have begun to adopt more of a systems approach to power quality monitoring. No longer content with placing monitors at certain locations at a customer facility, more utilities are placing monitoring equipment at key points on the distribution network and on both sides of the customer meter. This reorientation in conducting monitoring operations has coincided with more and more customers undertaking monitoring programs on their own and taking a greater interest in the data collected by utility monitoring. Besides these overall trends, specific ones include:
- Monitoring beyond troubleshooting. As mentioned previously, more utilities and customers are conducting monitoring for predictive purposes and to assess performance of the power system under a variety of conditions. Monitoring data is used to drive process improvements, correlate power and operational parameters, avert power quality problems, and control energy costs on a continuous basis.
- Trending. Many of the monitoring systems being deployed store large amounts of data and compile databases that can be analyzed to determine trends in system performance. Through this trending, utility and customer engineers can determine why problems are occurring and take steps to prevent them. In addition, maintenance and expansion priorities can be established from trend analysis.
- Establishment of power quality indices. As an outgrowth from the EPRI DPQ project, utilities have moved towards establishment of power reliability indices. These can include factors such as voltage sag performance (SARFI) and be used to prioritize maintenance activities and capital expenditures. These indices are not only based on number of events detected on the utility system, but also on sensitivity of customer equipment to disturbances. Many utilities are compiling their own indices and using them to benchmark system performance against the national average. Baltimore Gas & Electric determined that their system performance was favorable compared to national indices and ran an advertisement in the Wall Street Journal touting that fact. Accordingly, indices can be used for benchmarking and as a marketing tool for customer attraction and retention.
- Comparison of performance against standards and industry limits. Many monitoring systems are collecting data that can be used to compare power system performance to IEEE and other industry standards. In addition, many utilities and customers are comparing the performance of their power systems against tolerance limits established by industry organizations. Some systems are being configured to alert personnel when system performance exceeds guidelines established by these organizations.
- Multi-function monitoring. Several years ago, power quality monitoring instrumentation largely focused on recording voltage variations. Along the way, many instruments began to measure parameters such as demand, power factor, and harmonic content. In a deregulated industry, many meters are also incorporating revenue-metering functionality, a key consideration for monitoring power in customer facilities and at the utility-customer interface.
- Internet connectivity and Web interfaces. Many utility-scale and many customer facility-monitoring applications involve fixed instruments that must be downloaded for data analysis. Traditional approaches to do this included modems as well as direct download to computers. Many instrument manufacturers are incorporating Ethernet capability into their products, enabling instruments to be downloaded using the Internet and the data viewed and analyzed using the World Wide Web.
- Centralizing information. Many utilities are now storing more than just power quality measurements in databases. Georgia Power is currently conducting a monitoring research project that centralizes voltage sag recordings with breaker and recloser operations recorded by its transmission and distribution SCADA systems.
- Submetering. As utilities have moved towards deploying monitors at numerous points on their distribution systems, more and more customers are installing monitors at various points in the facilities. This enables determination as to whether a particular piece of equipment is impacting power system performance. Also, many customers are monitoring processes and individual pieces of equipment to determine demand, an activity that the New York State Energy Research and Development Authority estimates could result in a 20 percent reduction in energy cost.
- Monitoring to verify power delivery contract performance. To retain high-demand and high profile customers that are sensitive to power system disturbances, many utilities are signing special power supply contracts specifying standards for power service reliability. Detroit Edison Co. has signed special manufacturing contracts with General Motors, Ford Motor Co. and DaimlerChrysler that establish electric service quality guarantees that require payments when excessive numbers of interruptions and/or voltage sags are tallied during a calendar year. The contracts specify a “sag score” to track payments for interruptions. Both Detroit Edison and the carmakers monitor the service into the plants to determine contract compliance. Detroit Edison uses the collected performance data to determine vulnerabilities on its power system and to plan improvements to increase reliability.
The key trend that is likely to continue is the emergence of expert systems that will provide a wide range of reporting and problem solving functions for utility and customer personnel. These systems will help assure informed analysis and decision-making, improving utility operations and better relations between power provider and user. These trends, along with the benefits, are moving power quality monitoring into a strategic function to which every utility, regardless of its structure, should give serious attention. In a deregulated energy industry, increased efficiencies and attention to customer satisfaction will be the key to not just success, but survival as well.
McGranaghan is vice president of marketing and sales, and Sabin is manager of PQView and enterprise system applications for Electrotek Concepts, Knoxville, Tenn. McGranaghan and Sabin may be contacted at 865-470-9222 or e-mail firstname.lastname@example.org or email@example.com.