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How can Smart Grid equipment help to improve the overall efficiency of the distribution system?

DennisFlinn-smallMost electric power utilities have a relatively limited budget for infrastructure investments such as installing or replacing equipment. A strong business case is necessary to justify such capital expense and obtain financing from government entities or private investors. The number of rate cases in 2013 reported by EEI was the lowest since 2009. Therefore, optimal allocation of limited investment is required by identifying key investment areas.

There is a variety of smart grid equipment available that helps utilities achieve their goals of generating, transmitting, and distributing electric power to the end-user. It can be difficult to determine the best projects, where they should be applied, and to what scale. Financial and engineering studies are carried out to provide answers to important questions such as:

  1. What equipment should be considered?
  2. What locations will show the highest benefit?
  3. How will this equipment be installed and operated?
  4. What benefits will be achieved by implementing this equipment?

If used properly, the addition of Smart Grid equipment will improve the overall efficiency of the distribution system. Key benefits from Smart Grid equipment is the improved O&M and investment savings on distribution equipment like transformers as an outcome of matching rated capacity to consumer’s behavior. Benefits of a few types of Smart Grid equipment are discussed below.

Volt-VAR Control Equipment
The primary purpose of voltage control is to maintain acceptable voltage at the service entrance of all customers served by the feeder under all possible operating conditions. There are many factors that influence the voltage at each customer service entrance, including:

  • Under any condition, the supply line voltage fluctuates by a small amount. Voltage regulating devices must adjust the voltage so that the fluctuations do not cause it to drift out of the acceptable range.
  • During peak load conditions, the current (ampere) flowing on the feeder increases, and the voltage drop along the feeder due to the current flow increases. This results in decreased voltage for customers that are further from the substation end of the feeder. The voltage regulating devices must automatically raise the line voltage under peak load conditions to account for increased voltage drop. Conversely, when the feeder is lightly loaded, the voltage drop is lower, so the voltage regulating devices must lower the voltage to avoid possible high voltage conditions

Advanced voltage control capability of the Smart Grid equipment has significantly increased operating flexibility over conventional voltage control. While conventional voltage control is primarily intended to maintain acceptable voltage along the feeder, Smart Grid voltage control enables the user to achieve other operating objectives in addition to the primary function of maintaining acceptable voltage. The most common smart grid voltage control function is Conservation Voltage Reduction (CVR). With CVR, the system intentionally lowers the voltage on the distribution feeder to the lowest acceptable voltage value to achieve valuable benefits to the utility and consumers, such as reduced demand and energy consumption. As long as the feeder voltage remains above the minimum acceptable value, there is no adverse impact on the customer.

Fault Location, Isolation &Service Restoration (FLISR) Equipment
The purpose of FLISR is to improve distribution system reliability by identifying faults quickly, responding by isolating faults, and selecting the best method of restoring service to the un-faulted sections. There are many devices associated with FLISR equipment. A list of some of these devices is presented here:

  • Reclosers
  • Fault Current Indicators (FCI)
  • Automated Switches with data collection functionality
  • Outage Management System (OMS)
  • AMI Meters
  • SCADA

The main benefits of FLISR are shorter investigation times and shorter outage times. Smart relays and fault analysis applications provide greater accuracy in locating and identifying faults and their causes. Remote fault indicators notify grid operators and field crews when faults occur and when voltage and current levels are outside normal operating boundaries. Smart relays collect information about faults to help grid operators to location and determine the causes of faults.

Distribution Automation
Distribution Automation (DA) enables real-time monitoring and automation of the entire distribution system. Sensors and controllers are connected to distribution equipment and managed by computer algorithms. DA has the potential of reducing spare distribution capacity, locating, and reconfiguring networks to isolate faults and improve efficiency.

DA can also be used to monitor distribution assets and estimate equipment conditions. These functions can be useful in predicting equipment failure by developing preventive asset management plans.

Conclusion
DNV GL has developed a benefit-cost analysis that assesses grid conditions and optimizes spending by applying Smart Grid equipment to meet performance objectives. This analytical process is customized for each utility to get the most out of their technology investments. This customization evaluates different technologies, where they should be employed, and to what level of deployment. This Technology Investment Plan illustrates the tradeoffs between technology, associated benefits, and optimized ROI. This plan can be used to relate information to stakeholders and regulators in order to support pilot projects and investment approval. If you’d like to know more, please feel free to contact me at Dennis.Flinn@dnvgl.com.

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