Performance metering addresses increasing data needs

Patrick Corrigan

ABB Electricity Metering

Rick Stetler

Power Measurement Ltd.

Simple energy metering at the point of consumption is no longer adequate in today`s electric utility industry. Every company that expects to survive in the deregulated energy market is developing plans for a performance metering system to address the unprecedented need to measure contractual performance (or compliance) at each interface point.

One driving factor is the realization that large consumers of electricity are beginning to understand that they will benefit from the ability to verify the performance of their power provider against their energy supply contracts.

In the energy market, the exchange of goods and services for money is becoming increasingly difficult to define, measure and manage. We now deal with cogeneration, wheeling, interruptible rates, time of use rates, and real-time pricing. In response to consumer demand, progressive utilities are implementing contractual commitments to measure reliability, quality, and even “green” power.

Unlike conventional EMS and SCADA metering systems that serve as engineering and operations tools, a performance meter is a business tool-and sometimes a legal tool-needed to verify delivery at every point where energy goods and services are exchanged. These systems measure and analyze delivery to provide data used to control the flow of large sums of money, and they`re indispensable in a deregulated energy environment.

Exchange points exist between the generating company (genco), the transmission company (transco), the distribution company (disco), and the end user. In some places, an independent system operator (ISO), energy services company (ESCO) or a power pool council (PPC) may provide a direct link between the genco and the end user. In this case there may be fewer exchange points, but performance meters are nonetheless required. At each exchange point, the performance meter must satisfy suppliers and consumers that contracted goods are being delivered, and provide proof if a dispute arises over the performance of the supplier.

Performance metering

In a deregulated market, a key distributor responsibility includes optimizing customer satisfaction-which now means more than traditional energy and demand metering. As a transco customer, the disco requires access to the kind of information that the end user wants, including billing, cost and financial data; historic demand information; and real-time pricing. In addition, the disco`s perfor- mance meter must be able to:

– determine the source, cause, magnitude and ripple effect of power quality disturbances to ensure no other customers are affected. Not only is it essential to know whether or not disturbances are within contractual limits, it can be useful to have this information available before customers phone to report problems;

– determine the compliance of major customers to demand limits and interruptible rate requests; and

– compute network energy and power demand losses, including losses caused by wheeling.

Going further up the supply chain, the exchange points between the disco and the transco are a direct result of deregulation. A transmission service provider must keep all customers (discos) satisfied, which means providing access to all the information they have, and then some. For transcos, the performance meter must be able to:

– analyze capacity utilization in real time. This is an essential part of the requirement to provide open access to transmission line capacity. The transco must always know how much excess capacity is available on its transmission lines;

– analyze power quality data, energy flow and efficiency. This is the only way to ensure optimal network operation. Poor power quality will adversely affect customers, while poor efficiency will waste money;

– provide data to monitor phase voltages, currents, and imbalances; and

– broker supply/delivery contracts from gencos to discos in real time.

Electricity generators will also need access to the same information available to their customers. They will further need up-to-date information to determine the prices posted in real-time pricing schemes. They also must be able to:

– determine capacity based on anticipated and contracted loads and compliance with existing supply contracts;

– determine cost to produce; and

– determine power quality to establish the source, cause, and magnitude of disturbances that affected their ability to deliver power as contracted.

Versatile meters

Obviously, the various companies in the deregulated electricity supply environment have many common goals, several distinct metering requirements and an increasing need to share the same information among different entities. The difficulty is finding a performance meter that can measure the delivery of goods and services at the exchange points, and satisfy the whole spectrum of needs of each entity in the system.

Electric metering is rapidly evolving and improving access to real-time performance data. Yet conventional meters typically have restricted configurability, making it difficult to extract performance metering information beyond standard energy and demand readings. If the meter cannot be adapted to filter the data for new kinds of information, it usually means “out with the old and in with the new” when metering needs change. Obviously, this is an expensive approach to implementing a maintainable performance metering system.

The only intelligent electronic devices (IEDs) that begin to address this problem have the ability to be reconfigured for specific applications. For example, they feature some level of programmable logic for waveform recording and signaling based on set-point conditions. The most advanced performance meters offer object modularity within the device, allowing the user to select operating modules needed for specific applications.

This approach takes advantage of the most powerful aspect of object technology-a network of objects that can be easily linked to create exactly the system a user needs. An intelligent performance meter with object technology can be configured to monitor exactly the conditions that are most critical in a given power system, interpret the data in the field, and send very carefully focused information to the host computer system.

Networked information management

Performance meters in the field are only a part of a complete performance metering system. A total system also requires an information management infrastructure that makes all information available to the right people, in the right format, and at the right time.

The physical information network that meets this challenge can be simple or sophisticated, but it requires that every meter be connected over a communication backbone to a network that can be used for information management, as well as analysis and control. Software transforms performance data into information that can be used by the supplier to verify fulfillment of contractual commitments, and by the consumer to do exactly the same thing.

Information must be in a format that is useful to each user. The user interface, for example, should support system diagrams with easy access to fine details as well as general overviews of the system operation. Tools to analyze trend logs and disturbance information are essential. Networked object technology is also becoming the norm for advanced software, and vendors are starting to offer power monitoring systems based on such object models.

Information management systems based on low-cost desktop workstations, using the ubiquitous Windows NT operating system and conventional networking, are rapidly becoming commonplace. Using non-proprietary components allows users to take advantage of best-in-class technologies as the system grows, and to connect to wide area information sharing systems that are required by real-time pricing and independent system operators.

In a deregulated energy market, the ability to monitor and verify consumption patterns and power quality levels by both the provider and the consumer is very important. Without a clear understanding of this kind of information, it is far too easy to waste time and money negotiating penalties or assigning blame when a problem occurs. With this information, providers and consumers can cooperate to maximize power reliability and value. This need for information by two or more parties (who might be geographically distant from each other and the metering location) demands a means of accessing the meters or their information. This can be accomplished at:

– the device level through multi-port communications;

– the host software level through real-time access to the communicating software;

– the database level through shared access to the database tables; or

– via alternative methods such as publishing data on the Internet.

In any of these scenarios, traditional data retrieval schemes are not effective. Scheduled polling for raw information does not address real-time information requirements. Uploading large amounts of unfiltered data wastes communications bandwidth, and is impractical over large distances. Access to metering and billing information must be affordable on a large scale.

Metering devices must intelligently evaluate power measurements and initiate communications at specific intervals or when conditions are out of the ordinary. The Internet will prove to be a superior method of transferring such information.

With appropriate monitoring equipment installed to measure consumption and demand levels with revenue accuracy, concurrent with power quality information, an energy service provider can readily have nationwide access to all the metering data that is required to manage power supply contracts. Easy scalability ensures additional customers and value-added services may be provided to existing customers with little or no extra expenditure for the communication infrastructure.

Patrick Corrigan is marketing manager with ABB Electricity Metering in Raleigh, N.C., and Rick Stetler is vice president of utility systems with Power Measurement Ltd. in Victoria, Canada.

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