High-end polyphase electronic meters are a very versatile addition to a SCADA system. Next generation meters can communicate directly with a SCADA master station through communications processors, or they can poll existing remote terminal units (RTUs) in the substation, providing real time current, voltage, watt, and var data, and more.
Historically electrical substations have been a combination of dissimilar, independent islands of automation. Over time utilities have added devices to accommodate individual requirements in response to specific needs. These devices include panel meters; voltage, current, watt, and var transducers; capacitor controls; event loggers; digital fault recorders; and power quality data collectors.
Programmable operator displays
High-end polyphase electronic meters have the flexibility to measure demand using block, rolling, or thermal demand methodologies. These meters can be programmed to integrate the energy readings over intervals ranging from 5 to 60 minutes and show both individual and three-phase values on their liquid crystal displays (LCDs).
The displays can be programmed to rotate readings at a selectable rate, from 1 to 60 seconds per value. Newer devices also allow the user to customise the labels displayed with each data value, reducing the confusion created by unfamiliar abbreviations. High-end meters permit a wide variety of operating parameters (watts, vars, volts, amps, or power factor) to be displayed on easy-toread, high contrast LCDs.
A high-end polyphase meter may be used to replace the traditional transducers, eliminating annual maintenance and calibration, increasing accuracy, and improving reliability of the installation. The voltage and current values are displayed locally, and polled directly by the SCADA master station, or through the local RTU using DNP3 protocol.
Substation capacitor control
Utilities usually locate switched capacitor banks in distribution substations. Some of the most flexible high-end meters offer programmable logic that can provide direct capacitor bank control. To make the installation more cost effective, the meters are located near the current transfomer and voltage transformer connections, and the control outputs and status inputs are installed remotely near the bank switches, connected via low cost, fibre optic cable. This installation reduces control complexity, improves accuracy and flexibility, and permits remote override bank control by the SCADA system during emergencies.
High accuracy, time -tagged event capture
Next generation high-end electronic meters provide an excellent way to accurately log system events. Low cost, high accuracy, GPS-synchronised clocks now provide microsecond accuracy time that is used to log a wide variety of events, including faults, outages, voltage variations, harmonic alarms, control actions, and many others. GPS-synchronised timetagged event logs allow engineers to compare information collected at multiple locations and determine the exact sequence of events.
This information is often critical to understanding event causes and effects, and implementing system improvements. Synchronous phasor measurements are another important use of accurate time; for example, the SEL-734 high-end meter can measure and report real time system voltage angle measurements to advanced synchrophasor visualisation systems.
Feeder power quality monitor
Many utilities want to continually monitor power quality on their distribution feeders to log voltage sags/swells/outages, to capture oscillographic voltage and current measurements during power quality events. Installing a high-end electronic meter on each feeder increases the amount of quality information available to diagnose operational problems. Waveform event capture allows quick, accurate analysis of feeder events, giving the system engineer a great tool to ‘see’ what happened.
The time has come to eliminate islands of automation and to use quality information sources to improve system operation. High-end electronic meters like the SEL-734 revenue metering system offer utilities a very flexible, cost effective way to improve operations. The SEL-734:
- Communicates with the SCADA system using DNP3 protocol
- Provides a panel LCD
- Replaces high maintenance transducers
- Controls substation capacitor banks more accurately
- Logs time-tagged events
- Collects valuable power quality information at feeder level.
Cost effective highly accurate, easy-to-install, lowmaintenance and flexible implementation makes the SEL-734 a great investment for utilities of all sizes.