Schweitzer Engineering Laboratories, Inc. (SEL) is a 20-year-old company 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. Our customers have asked us to make a high-end revenue meter because they want 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 ‘blue boxes’, as the digital protective relaying equipment from Schweitzer Engineering Laboratories, Inc. (SEL) are informally known, must respond within milliseconds to protect transmission, distribution and generation equipment from electric system fault conditions. Our customers have asked us to make a high-end revenue meter because they want 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, 4-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
Many substations and generation plants have revenue meters that are co-located with the protective relaying equipment. This makes sense, as these facilities are often where the hand-off of power occurs from generation to transmission, from transmission to distribution, and finally from distribution to an industrial load. In many of these installations, however, 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 analogue 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 and amperes.
With the SEL-734 the meter can share any measured, calculated or recorded quantity with the other systems in the substation or industrial facility, using industry standard protocols and data communication interfaces such as DNP, Modbus, Ethernet and EIA serial ports. The data communications capability of high-end meters is of increasing importance as high-end metering evolves from being a monthly read to being a daily or hourly activity supporting requirements such as power scheduling reconciliation and real-time pricing.
It is impossible for us 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 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.
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 synchronised phasor measurements. These measurements can be used in programmable calculations and triggers within the meter.
WHAT THE SEL OFFERS THE METERING INDUSTRY
The SEL-734 Revenue Metering System brings our focus on quality, reliability, innovation and service to the metering industry. Protective relays are mission-critical equipment for electricity utilities, and SEL takes its commitment to quality very seriously. Our industry-leading ten-year warranty reflects our commitment and demonstrates the quality and value we deliver.
Support to our customers is provided through our Washington, U.S.A. headquarters, 24 USA offices, and 15 international locations in the UK, China, Australia, New Zealand, South Africa, Brazil, Bolivia, Canada and Mexico.