A brief summary of voltage conservation: How can it improve energy savings?
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Uses and Benefits
Voltage conservation (VC) offers the potential to reduce power system losses, save energy, and lower demand on the distribution system. The passive approach to savings that VC offers is particularly attractive where energy or demand reduction targets exist; VC is being used by some utilities as an approach to energy savings or peak reductions in tandem with programs requiring active customer engagement.
Various studies, including those by DNV GL, have assessed the energy savings potential or historical savings of VC programs. Savings are often cited in the range of less than 1 to 4% of energy consumption and of peak demand. Ultimately, savings depend on (1) reaction of a circuit to voltage reduction and (2) the extent to which voltage is reduced. Load composition, for example, is a factor that affects response to voltage changes. Typically, the reduction in kW in response to a reduction in voltage is described as CVR Factor. Formally, CVR Factor is the ratio between the percentage change in energy and the associated percentage change in voltage. Circuit average CVR Factors for implemented programs have ranged from just over zero to above one.
With regard to voltage reduction amounts, the circuit characteristics—such as equipment age and circuit design—can affect the extent to which voltage can be reduced on a system. In particular, the goal of VC is lower voltage on the system while maintaining customer voltage levels within required standards. The extent to which a system would want to reduce voltage depends on the voltage profile on a circuit and the voltage levels at which customers are currently being served. Some programs have implemented upgrades to their circuits to flatten the voltage profile prior to implementing VC-driven voltage reductions. Overall, even for circuits with similar CVR factors, savings can differ due to differences in circuit voltage profiles.
Costs & Considerations
A number of approaches have been taken to implementing VC. These approaches range from ones that manage voltage via equipment at the substation to those that manage voltage along the feeder, and ones that rely on pre-planned voltage reductions to one that determines voltage reduction based on feedback from the system. For the latter, feedback can be based on measurements where the controls are, or based on measurements across the full system.
Ultimately the approach to VC will affect the cost of implementation. Measurement that allows for feedback to control CVR in “real-time” can require communications and infrastructure upgrades while those with no infrastructure outlays or communication investments can require modeling and maintenance.
Regardless, of approach, many systems would require some sort of investment to ensure that customer voltages across the system are maintained when voltage is lowered upstream. Because VC may not be appropriate for all circuits or all customers on a circuit, cost-benefit analyses should account for less than full deployment across the system.
If you’re interested in seeing more detail on voltage conservation, or would like to share practical insights or field experience with us, please contact Jessica Harrison.
Jessica Harrison is a principal consultant with DNV GL. She has an interdisciplinary background in the electric power industry, including work in engineering analysis, market assessments and public policy. She has focused on the integration of novel technologies with electricity markets and power systems. She leads the Energy Storage and Electric Vehicles Practice Area in the Americas region of DNV GL. Read her full bio on our contributors page.