ELECTRICITY METERING AND MONITORING

Points to Consider When Choosing Billing Meters for Utility, Industrial or Commercial Applications

Energy suppliers and consumers use enterprise energy management (EEM) systems and equipment to provide billing support, control energy costs, decrease downtime, reduce maintenance, accelerate problem response, and improve electrical infrastructure planning. Although a typical EEM system consists of three main components: meters, communications, and energy management software, a key element shared by both the utility and the customer is the billing meter installed at the customer's main service entrance.

Traditionally used by the utility to bill for basic consumption, the role of the billing meter has expanded to offer additional services to both the power provider and the consumer. Aside from simple billing, intelligent metering and control devices now play a key role in power quality analysis, operations management, control and monitoring, and value-added services offered by the utility to the customer. Many of these applications require specific, advanced capabilities from the billing meter.

Billing support
In any billing application, accuracy is an essential requirement (conforming with ANSI C12.2-2001 or IEC 60687 0.2S standards). For accurate billing, the meter may be required to aggregate loads, calculate wheeling losses, and share the information with billing collection systems like MV-90. Meters are often now required at more points across the grid, including generation, key transmission interchanges, and large commercial and industrial facilities; for these high-profile high-revenue locations, Class 0.2 accuracy is essential.

And because a billing meter is essentially the cash register for these important locations, this data may also be used by co-generators, ISOs, distribution companies, transmission companies, generating companies, power brokers, power providers, power schedulers or producers like IPPs, merchant plants and power marketers. All stakeholders can benefit from fast, simultaneous access to power information, and with multi-protocol, multi-port communications, the meter can provide this information through a variety of mediums, including telephone (POTS), Ethernet (LAN/WAN), and wireless networks (cellular, CDPD, RF, etc.). Should communications fail, the meter retains billing information in load profile memory while also providing an audit trail of important meter events with time-stamped records.

For independent power producers, peaking plants, and generators with widely varying load curves, a wide dynamic range is beneficial. For locations that may implement distributed generation, cogeneration, or more progressive billing structures, four-quadrant bi-directional meters that measure energy flow both in and out of the metering location are becoming the standard.

Power quality analysis
Power quality management typically involves the deployment of strategies to prevent disruptions related to system outages, transients, sags/swells, and/or harmonics. Besides tripping breakers, excessive amounts of harmonics can overheat, damage, and reduce the life of equipment such as transformers and motors. Voltage sags can cause similar problems, as well as causing computer control and communication equipment to trip offline, which in turn can result in manufacturing production problems. By isolating the source of these problems through power quality analysis, power utilities and their customers can find long-term fixes to avoid repeat occurrences. In the event of a disturbance, a billing meter can also help to determine whether a disturbance originated on the supply side or the demand side of the main service entrance, and retain proof of the event's origin.

A good power quality meter can also help to determine accurate equipment tolerances, so that protective devices can be adjusted for Ôride-through' to avoid unnecessary breaker tripping or equipment damage. By tracking the number of breaker operations or the time of equipment use, one can easily identify equipment that has exceeded safe operating limits.

The fundamental features of a good power quality meter include waveform recording, harmonics analysis, transient detection, sag/swell measurements, symmetrical components, and automated alarming and control features to ensure a fast response to power quality events.

Operations management and control
Operations management and control can improve the efficiency and reliability of electrical distribution systems by focusing on the management of current conditions throughout the grid, or within a customer facility. Power meters take action by providing real-time supervision and reducing costs. Meters can monitor the real-time status of a facility's electrical system, take action, or issue alarms in response to conditions such as voltage sags, excessive transformer temperatures, or demand overloads. This can greatly reduce response time and help to avert potentially expensive or damaging results. During times of peak demand, the meter can automatically shed loads or initiate standby generation to help customers avoid demand penalties.

These days, one meter can often do the job of several pieces of older equipment, and when combined with enterprise energy management software, a network of meters can be used to create an overall load profile to provide a clear picture of energy, demand and/or aggregated/totalized energy usage.

When planning for expansion, load trending information can also help to predict future energy needs by identifying the available capacity of existing equipment. Depending on the device, equipment status reports or high priority alarms can be sent directly to key individuals through a variety of mediums including e-mail, pager, telephone, cell phone, cellular digital packet data (CDPD), and radio frequency. This information can also be communicated directly to SCADA, building automation, or other systems via DNP or MODBUS protocols, or via KYZ pulses and/or analog outputs.

To help manage long-term energy costs, energy consumers can also use advanced metering to support cost-control applications. For example, with a revenue-accurate billing meter, a facility can monitor its main feed to verify consumption and ensure efficient energy usage. With additional metering installed within the consumer's premises, the energy consumer can track and allocate energy-related costs by department, tenant, process, or output. Additionally, the consumer can perform sub-metering of tenants, departments or processes.

For billing purposes, a meter must be revenue-accurate and (for submetering applications) capable of energy cost analysis functions such as cost allocation and process accounting. For operations management and control, a power meter typically requires real-time information, in addition to load profile recording, and may also require analog and/or digital input/output, and (if desired) automated alarming and control. Again, multi-protocol, multi-port communications is particularly important to enable the meter to interface with existing systems such as SCADA, EMS, and MV-90, and communicate with individuals over a variety of mediums.

Web-enabled value-added services
The introduction of web-enabled energy and power quality meters has added a new dimension to revenue metering services. New web-ready metering features such as e-mail messaging and meter-based web-browser support can now enhance the many benefits of real-time monitoring for both the power provider and consumer. A web-enabled billing meter installed at a customer's service entrance can share information with the utility, ISO, and customer simultaneously. This arrangement enables the utility to offer real-time metering to its customers as a unique and cost-effective value-added service.

Using meter-based e-mail messaging, a web-enabled meter can send energy readings, load profile data, priority alarm notifications or scheduled system-status updates by e-mail to anyone within the facility, or if connected to a gateway, around the world. Metering data can be transmitted via e-mail message over the Internet, LAN/WAN, wireless or CDPD modem to a workstation, cell phone, pager or PDA.

Meter-based web browser support adds an on-board web server to the device, making the meter's real-time operational, billing and power quality information accessible through a local or remote LAN. With this feature, a customer can use a standard browser to directly and securely view power system information from its own billing meter through a security portal or extranet. The customer can then use this information to help analyze energy usage, diagnose operational problems, and verify power quality at or throughout the facility. Because this information comes directly from the meter, the customer can get the latest information in real-time, and respond immediately to changing conditions.

To provide this type of value-added service, a meter must offer Internet connectivity, and be capable of sending e-mail messages or communicating directly with a host web site. Other requirements include real-time metering, historical data recording, and automated information reporting.

Conclusion
New intelligent metering technologies are providing new ways for power suppliers and consumers to satisfy billing requirements, while also minimizing hardware investments, reducing operating costs, and extending the life of their existing equipment.

When comparing the metering products available today, it is important to satisfy the basic requirements for the individual application, but also to look beyond the meter itself to consider additional opportunities such as value-added services, increased communications, and improved accuracy that can greatly enhance an enterprise energy management system.

Jason Sheppard is with Power Measurement Ltd., Saanichton, BC, 1-877-638-3748, www.pml.com.
Al G. Weber is with ABB Inc., Raliegh, NC, 1-800-338-5251, or from Canada 1-800-263-9110, www.abb.com/metering. ET