The answer to this question is very simple—our customers asked us to. Schweitzer Engineering Laboratories, Inc. (SEL) is a 20-year-old company that is best known for making digital protective relaying equipment used by electric utilities worldwide. These "blue boxes," as our products are informally known, must respond within milliseconds to protect transmission, distribution, and generation equipment from electric system fault conditions. The reason our customers have asked us to make a high-end revenue meter is that they want to get in a meter what they've learned to expect from us in a protective relay—a reliable product with industry-leading features at a competitive price.

Our first revenue metering product is the SEL-734 Revenue Metering System. The SEL-734 is a transformer-rated, four-quadrant, 0.2 Accuracy Class meter targeted at substation, generation, and industrial metering. The metering features of the SEL-734 are summarized below.

• ANSI C12.20 0.2 Accuracy Class
• Four-quadrant: ±kWh, ±kVARh leading, ±kVARh lagging
• Demand: block, rolling, thermal
• Line and transformer loss compensation
• 35 days of 12-channel data at 5-minute intervals; longer records at up to 60-minute intervals
• Time-of-day synchronized
• Nonvolatile memory

Communications

Many substations and generation plants have revenue meters that are colocated with the protective relaying equipment. This makes perfect sense in that these facilities are often where the handoff of power occurs from generation to transmission, from transmission to distribution, and finally from distribution to an industrial load. In many of these installations, the information in the meter is isolated from the other systems in the facility. Traditionally, the only connection between the meter and these other systems has been KYZ pulses (contact outputs) or analog current outputs that are fed to pulse recorders and SCADA remote terminal units (RTUs). This approach requires a hard-wired interface for each metered quantity such as watts, VARs, amperes, etc.

With the SEL-734, the meter can share any measured, calculated, or recorded quantity with the other systems in the substation, plant, or industrial facility. This is accomplished using industry standard protocols and data communications interfaces such as DNP, Modbus®, Ethernet, and EIA serial ports. The data communications capability of high-end meters is becoming increasingly important as high-end metering evolves from being a monthly read to being a daily or hourly activity to support such requirements as power scheduling reconciliation and real-time pricing.

Automation

It is impossible for us as an equipment manufacturer to anticipate everything that a customer might want to do, and then build in a specific function to do it. Instead, we have found it to be much better to provide a programmable logic mechanism, called SELOGIC® control equations, that allows our customers to implement their own features. With SELOGIC math functions, customers are able to customize controls based on combinations of power system quantities. For example, a multiple of harmonic power can be added to fundamental power to predict transformer heating and alarm on overloads. Voltage excursions can be totalized to indicate service quality. An alarm can be generated if the power in one phase drops to zero.

As another example, the SEL-734 can be used to reduce power costs. A distribution utility or industrial customer can reduce peak demand charges by programming the SEL-734 to start a diesel generator if the load information indicates that a new peak demand will be set. Similarly, SELOGIC control equations can be used to send load control signals to high-demand equipment such as chillers or pumps.

Power Quality

Power quality metering is gaining in importance as industrial manufacturing processes become increasingly sensitive to power quality. Many utilities have performance-based rates that incorporate financial penalties if the power quality does not meet a minimum standard. In effect, power quality is becoming yet another metered quantity. Because of this, we provided the SEL-734 with a suite of power quality measurement features, such as voltage sag/swell recording, harmonics, instantaneous values, and synchronized phasor measurements. These power quality measurements can be used in programmable calculations and triggers within the meter.

What Does SEL Have to Offer to the Metering Industry?

The SEL-734 brings our focus on quality, reliability, innovation, and service to the metering industry. Protective relays are mission-critical equipment for electric utilities. As such, SEL takes its commitment to quality very seriously. Our industry-leading, ten-year warranty not only reflects our commitment but also demonstrates the quality and value we deliver. SEL continuously invests in our manufacturing processes and people, and we benchmark ourselves to learn, improve, and lead in production efficiency and quality. 

Support to our customers is provided through our Pullman, Washington, headquarters, 24 U.S. offices, and 15 international locations in the United Kingdom, China, Australia, New Zealand, South Africa, Brazil, Bolivia, Canada, and Mexico. As a result, SEL offers unparalleled local application assistance and technical support.

About the Author

Bob Hughes has more than 18 years of experience in electric power system automation, including SCADA/EMS, distribution automation, power plant controls, and automated meter reading. He has worked on projects in the United States, Canada, China, and Australia. He has a degree in electrical engineering. He joined SEL in 2002 as product engineer. Contact Hughes at Bob_Hughes@selinc.com.

About the Company

Schweitzer Engineering Laboratories, Inc. serves electric power utilities and industrial companies worldwide through the design, manufacture, supply, and support of products, systems, and services for power system protection, control, and monitoring. SEL was the first company to exclusively manufacture digital protective relays and to provide highly accurate fault location and event reporting as an integral part of power system protection solutions. SEL exists to make electric power safer, more reliable, and more economical. For more information, contact SEL by phone (509) 332-1890; fax (509) 332-7990; or mail to 2350 NE Hopkins Court, Pullman, WA 99163-5603. SEL is online at www.selinc.com.