Conservation Voltage Reduction Helps Utilities Survive Peaks
By Greg Myers, Sensus
All electric utilities have a need to better gauge demand during peak load times. Too high and everybody pays more. Too low and you risk brownouts and blackouts.
Conservation voltage reduction (CVR) has emerged as an attractive solution for utilities seeking to gauge peak demand and optimize their power grid to help control their energy costs while still delivering optimal power to customers.
Following is an overview of how CVR can help utilities optimize delivery and make better use of their energy resources, including a case study featuring a utility that leveraged available infrastructure to implement a CVR program and reaped significant benefits as a result.
Voltage Levels Refresher
Nominal voltage for a residential home in the U.S. is 120 volts (V) with an acceptable variation of +/- 5 percent (+/- 6 V). A range between 114-126 V, therefore is generally considered “good” power supply, though many utilities regularly operate around 120 V to stay on the safe side of good supply.
Distribution feeders are supplied from electric substations. Voltage regulation is managed through regulators located in the substations or on the feeders. Impedance settings in the regulator controllers help correct the adjusted voltage on the feeder. This approach typically results in higher voltages at the beginning of the feeder and lower ones along the feeder as voltage drop occurs along the distribution lines.
Long feeders can be challenging because voltage can drop below 114 V at some point. When this condition occurs, utilities use field equipment (capacitor banks, line regulator banks) to adjust the voltage back to “good” levels. From this adjusted point, the voltage will again drop along the feeder’s lines.
How CVR Can Help
CVR gives electric utilities the ability to view voltage data and make adjustments in real time for more accuracy and control. By leveraging CVR, therefore, electric utilities can reduce their system demand during peak events.
With the right CVR solution in place, utilities can:
“- Monitor and manage real-time voltage data using metrology, communications and analytics
“- Measure and optimize voltage across the entire distribution network, from substations to homes and businesses
“- Ensure the proper level of service voltage is delivered to customers
“- Reduce overall energy usage for the utility system through right-size voltage
“- Save money with less need for in-house generation (larger utilities) or for purchased power (smaller utilities)
Beginning the CVR Journey: Where to Start
The keys to getting the most value from CVR are gathering the right data to make informed decisions on how to best manage and deliver power during peak events, and having the right network to transmit this data for effective, real-time analysis. In many cases, this infrastructure might already be in place, especially for utilities that have deployed an advanced metering infrastructure (AMI) solution for consumption data transmission and analysis.
With the right AMI technology, utilities can use meters to collect and transmit usage data at regular intervals, then analyze this data to understand demand in real time and make the proper adjustments. For data transmission, many utilities and municipalities have implemented private networks that offer two-way communication over a licensed spectrum that uses a star network design. This type of network can offer point-to-multipoint connectivity for faster data transmission without the bandwidth issues that often plague public mesh networks.
AMI can be instrumental in enabling CVR, creating a system that uses voltage data from electricity meters working together as a feedback loop of actual values. The voltage information is measured in two ways:
1. The meters on the feeder can be programmed to send voltage data into head end software as part of their normal billing read.
2. Some meters have the added capability of calculating a one-minute average of voltage, and frequently reporting those detailed values. These act as bellwether meters, which are typically 1 to 2 percent of the electricity meters spread out over the distribution system.
The combined approach provides additional voltage resolution for improved accuracy. Utilities use the voltage data to identify which feeders are running with lower or higher voltage and can then adjust them as needed. The data may also indicate which feeders are the best candidates for further CVR load reduction.
Finally, utilities can use advanced analytics software applications to receive CVR information from meters installed on the network, which they can then use to determine where voltage is too high or too low. These applications can also help indicate where to use a SCADA system to adjust levels by raising or lowering voltage to get it back to “good” levels.
Wake EMC: Using CVR to
Achieve Bottom-line Impact
When Don Bowman, Wake EMC’s manager of engineering, and his team deployed an AMI solution–comprised of more than 43,000 meters and an advanced two-way communication network–in 2012, CVR wasn’t one of the driving factors. They soon discovered, however, that it offered some of AMI’s greatest benefits.
“We started to see a change in energy rates, which caused us to look at ways to reduce peak loads,” said Bowman. “Rather than asking our customers to make changes, we decided to look internally at ways we could clean up our side of the system, and CVR was one of the solutions we identified.”
With a system for reading and transmitting voltage data in real time already in place, Wake EMC quickly jumped on opportunities to reduce peak loads without impacting customers’ power supply.
“We had this massive amount of data coming into our system, and what we learned is that there were enough inefficiencies that we could correct to make a substantial impact on our costs,” said Bowman.
Though they typically run loads between 120 V and 125 V, Bowman and his team learned they could reduce loads to 114 V during peak events while still supplying adequate power to customers. By using built-in alarms in their AMI solution, the system could alert them to when voltage was in danger of running below safe levels.
“Having real-time voltage alarms in your meters is key for CVR to make sure you’re not bringing it down too low,” reiterated Bowman. “In the time we’ve been doing CVR with our AMI solution, I haven’t had one residential customer call me to complain about low voltage.”
In more than three years since beginning their journey with CVR, Wake EMC has seen costs savings that have stretched beyond what Bowman initially thought possible.
“For every half of a percent of load we reduce we’re saving up to $100,000 per year, and we’ve managed to reduce it by up to 4 percent in some cases,” said Bowman. “On average, we save somewhere between 2 and 3 percent, up to $600,000 annually. We’re incredibly proud of the system we’ve implemented.”
CVR is an effective solution that provides strong economic benefits while meeting critical utility and customer needs.
With CVR, many utilities, like Wake Electric, have experienced significant voltage reduction as well as a drop in energy consumption. Specific amounts depend on the load types on a particular feeder, but it is common to see corresponding energy savings of 1 to 2.5 percent on feeders running CVR.
To recap, utilities that use CVR can:
“-Reduce system peak demand consumption
“-Improve service quality
“-Extend the life of equipment
“-Lower operating costs
“-Enable preventive maintenance
“-Offer voltage visibility and insights across the network
“-Provide information to ensure adequate power generation
“-Balance energy supply and demand
Taken together, the energy saved during peak events across the system can add up to significant cost savings for the utility that can be reinvested in further improvements or passed on to the customer. | PGI
Greg Myers is vice president of global electric marketing at Sensus. Greg has 25 years’ experience in the electric industry, including eight years of service at Sensus. He received a bachelor’s of science degree in electrical engineering from West Virginia University of Technology and earned a Master of Business Administration from John Hopkins University.