Conservation Voltage Regulation: A Strategy in Search of a Technology

What Is CVR?
Conservation Voltage Regulation (CVR) is a technique for reducing voltage along the feeder lines. Utilities have been using, experimenting with or researching CVR for over 20 years. It was first introduced on a large scale in California in 1977, with good results.

But until now, widespread CVR has been a strategy in search of a technology that would allow it to reach its full potential.

CVR decreases the voltage at which electrical power is consumed and yields on average, nationwide, a 1% energy savings for each 1% in voltage reduction. And it is far less expensive to save that 1% for later use than to pay to create a 1% increase in capacity from generation to distribution.

Thus, CVR has since the late 1970s been an attractive, compelling concept.

Why CVR Is Necessary
The American National Standards Institute (ANSI) requires that voltage be made available to residential customers at 120V +/- 5% — which yields a range of 126V to 114V. On any feeder line, especially those over three miles long, voltage on the feeder line gradually decreases as the cumulative load on the feeder line increases. This is called “line drop.” Because of line drop, power must be transmitted at a high enough voltage that the last house on the line gets at least 114V. Consequently, power is often transmitted at an initial value of 126V. US homes receive an average of 122.5V. Approximately 99% receive more voltage than they need.

Line Drop Compensation
Since appliances, light bulbs and other electrical devices operate efficiently at reduced voltages, utilities can provide service at the lower end of the acceptable range with no detriment to their customers. On lines operating with CVR, voltage is regulated with a technique called Line Drop Compensation (LDC) to provide voltages within the reduced range of 120V to 114V. LDC is a form of CVR that reduces the average voltage to 117.5V, and ensures that the home at the end of the line gets the minimum 114V.

The Benefits of CVR
Customers save money on electricity with service at a lower voltage, and the life of appliances, light bulbs and other electrical devices is extended. Utilities save energy and capacity, yielding lower fixed costs. And the environment benefits as well: the by-products of the most widely used kinds of power generation are greenhouse gases.

Testing of CVR
Between 20 and 25% of US utilities have tested some form of a CVR program on parts of their systems and for widely varying lengths of time. In general they have successfully reduced the average voltage supplied to residential and some commercial customers about 4%, to about 117.5V from the average 122.5V. Yet CVR is currently applied nationwide to less than 2% of all feeders, and most of these are in California, where CVR is mandated.

Current Limitations of CVR
This appears to be the limit to which CVR can be applied by the utilities at present. Fluctuating electrical loads limit the lowest voltage setting. On any electrical distribution system, as the electrical load increases the voltage decreases. Since the load fluctuates dynamically, the utilities must keep the voltage high enough so that no customer’s voltage dips below 114V before the system-level voltage regulation reacts to the fluctuating load. Furthermore, customers with different requirements from those of residential customers are usually mixed on the same distribution feeders, interfering with implementation of CVR on those lines. The presence of particularly sensitive customers, such as hospitals and manufacturers, on a feeder line can preclude the entire feeder line from using CVR. Until now, CVR has been a thoughtful and ambitious notion that could be implemented only on short feeder lines with expensive and labor-intensive equipment upgrades. To implement CVR on the US electrical grid — even with its highly developed infrastructure — extensive modifications of utility equipment would be necessary. Here is just a partial list:

– modifying tap-changing settings and voltage regulators
– adding more LTC voltage regulators
– adding more capacitors
– reconfiguring the utility’s central control and communication systems
– constructing more substations
– shortening feeder lines and configuring them with larger conductors
– reconductoring present feeders
– converting to higher primary voltages

The greatest limitation to CVR as it is currently practiced, is what we call the gray zone. The gray zone is the voltage drop that occurs between the distribution transformer and your service entrance. Most utilities assume the average drop across the gray zone is 3 volts. In fact for the utility it is an uncontrollable variable that can be as high as 5 volts and as low as 1. This is the reason why feeder line voltage is rarely set lower than 117 volts at the distribution transformer, even using LDC techniques. A voltage drop of more than 3 volts across the gray zone would cause your voltage at the service entrance to be too low. It was impossible for the utility to set the voltage at everyone’s service entrance to 114 volts, until the HVR and EVR products became available. Our products regulate voltage beyond the point in the system where all the variables that complicate the traditional implementation of CVR occur.

The MicroPlanet Solution
Until MicroPlanet introduced its HVR™ and EVR™, there had been no way to make CVR simple enough that it could be implemented widely and intelligently, no way that it could be implemented at the micro level — that is, the service entrance to the home or office — rather than at the feeder-line level. The HVR and EVR allow Conservation Voltage Regulation to be practiced on a micro level, home by home, business by business — easily, reliably and inexpensively. It is CVR for the new millennium.

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