Benefits of Automated CVR
By
Tom Wilson, Chairman
PCS UtiliData

Conventional Conservation Voltage Reduction/Regulation (CVR) based on Voltage Spread Reduction and Line Drop Compensation settings in regulator and LTC controls is not used for Peak Shaving, or as a Load or Demand Control mechanism. In fact, conventional CVR often maintains the bus voltage at higher levels during peak loads than it would be if CVR were not implemented.

Automated CVR is implemented by using a micro-processor based controller in the substation and allowing it either to directly control or to change the voltage set points of the regulators or LTCs. Automated CVR can be either open loop or closed loop with the end of line voltages being monitored in "real time." Closed loop systems use end-of-line voltage as the process variable. Set points for the end-of-line voltages are entered locally at the substation or can be downloaded from a master station. Open loop systems receive distribution system model data from a master. Using this data, set points are computed and downloaded to the regulator or LTC controls.

A key advantage of using an automated system to implement CVR allows is that a utility can also implement Peak Shaving, Load and Demand Control, Peak Load Reduction and Emergency Demand/Load reduction.

Peak Shaving algorithms in an automated system attempt to prevent demand during a metering interval from going higher than a previous high demand during a billing cycle. At the beginning of a billing cycle, the peak demand is reset to some value that the customer or utility sets. This is the first peak demand value that the algorithms will try to stay below. Minimum allowable end-of-line and critical point voltages are determined by the customer or utility. These are the settings that the algorithms will not allow the system to go below when attempting to shave a peak. Peak Shaving can be used by utilities who purchase power from other utilities and have demand ratchets or by customers with large facilities that can take advantage of automated CVR as an energy conservation measure.

Peak Load Reduction is very similar to Peak Shaving in concept. Peak Load Reduction is primarily used by utilities to avoid peak loads during high demand periods. Peak Load Reduction can be automated at local substations by entering the time periods during which high peaks may occur or during which system peaks are expected. The automated system will then lower the end-of-line voltage set points to lower values that have been determined by the utility. Peak Load Reduction can also be dispatched from a control center to avoid peaks or rate manipulation by energy suppliers. Because Peak Load Reduction is primarily a short term measure, ANSI B level voltages may be used as the lower set points. Peak Load Reduction can be used as a "non-wires" transmission resource.

Emergency Load Reduction allows the dispatchers or system control centers to reduce the distribution voltage levels to lower ranges during system emergencies. Depending upon the utility’s communications infrastructure distribution voltage reduction can attained within 4 to 10 seconds. Emergency Load Reduction using automated CVR systems has two major advantages: By reducing distribution voltages levels, reactive power requirements of the loads are reduced, tests show as much as a 30% reduction in reactive power requirements from normal operating conditions with only an average 2 to 3 volt reduction from 120 volts on distribution feeders; and, the system also prevents the regulators or LTCs from raising taps to maintain distribution voltage levels and exacerbating the system emergency.