CVR? VVO? VVC? What do these letters stand for and what is all the hype and fanfare about?
Conservation Voltage Reduction (CVR) has been around for decades and known by many different terms. It is the activity of slightly reducing the end-use/service voltage to customers in order to save energy without affecting equipment performance. The down side is that, if you lower the voltage too much, or inversely raise it too high, the efficiency is reduced in some types of loads, and you can actually use more energy. In the past, it has been difficult to monitor and control attempts at CVR to a degree that could be proven beneficial.
The advent of the “Smart-Grid,” along with its newly found friends such as AMI, DA, etc., has provided a means to make better use of CVR; by increasing the possible benefits and reducing the past inherent downsides, positive net results are achievable.
In the past, controlling end-user voltage levels as normally attempted via the substation LTC or bus regulators, and possibly down-line regulators. The voltage would be set at the regulating equipment and would decline along the distribution line until the feeder ended. The use of fixed and/or switched capacitor banks along the feeder was an attempt to “flatten” the voltage profile. Such attempts were often foiled by lack of monitoring, control and communication; without these capabilities, schemes like this could easily raise the voltage at other points on the feeder too high.
Entering the arena now is one of the newer players in the Smart Grid’s arsenal – VVO/VVC. Voltage and VAR Optimization (VVO) or Voltage and VAR Control (VVC) are variations of using switched capacitor banks to level and maintain the voltage profile to achieve the desired results. The major difference between VVO and the prior attempts at “voltage reduction” is the use of newly obtainable and integrated monitoring and communication systems.
On these prior attempts on feeders with multiple voltage regulation and VAR compensation devices, each device was controlled independently, without much regard for the resulting consequences of the local control devices. This often led to less than desired effects on the feeder, the substation, and the distribution system. What was needed was a means to obtain, from monitoring, the necessary real-time end-use voltages, and information on the status and effects of each switchable VAR compensation device.
To this end, the Advanced Metering Infrastructure (AMI) is a big player. This infrastructure, or similarly designed and developed facilities, can monitor and communicate the needed information in near real-time to a central point, allowing the appropriate decisions to be made and communicated back to the VAR compensating devices along each feeder. By using such tools, VVO can minimize power loss or demand without causing undesirable voltage violations. Case studies have shown achievable savings up to 3% of system distribution losses, and comparable reductions in system peak demand.
A recent publication by the Department of Energy (DOE) entitled “Evaluation of Conservation Voltage Reduction (CVR) on a National Level” has useful information and insight into this area:
http://www.pnl.gov/main/publications/external/technical_reports/PNNL-19596.pdf
Contact us for more information.