Posted by: nialljmcshane | August 8, 2010

The Naperville Smart Grid Investment Project: Technology Overview

In last week’s blog entry I discussed the steps that were being taken by the public utility in Naperville IL to secure consumer buy-in for the investments in technology that this utility has been making for many years and are now accelerating with the help of a grant under the Smart Grid Investment Project provisions of the ARRA stimulus funding.

Naperville is a city of 145,000 citizens, located in DuPage and Will Counties, 30 miles SW of Chicago IL.  Electricity in the city is supplied by the public utility which is owned and operated by the city.  The utility has over 57,000 meters (approximately 50,000 residential and 7,000 commercial & industrial customers) and experiences peak demand of 388 MW and annual energy usage of 1,550,000 MWh.  The 46 sq mile service area has 19 miles of 138 KV and 33 miles of 34.5 KV transmission lines, 72 miles of 12.47 KV overhead and 800 miles of 12.47 KV underground distribution lines.  Connection to Commonwealth Edison transmission lines is made at 7 locations around the city.

Over the past 18 years, Naperville’s public utility has strategically invested in technology to dramatically improve reliability, reducing average outage time per customer from 120 minutes in 1992 to less than 18 minutes today.  These investments have included implementing SCADA for real time monitoring and control as well as distribution automation, substation automation and an enhanced, secure fiber optic communications network.  Of these projects, the SCADA implementation is complete and the others are 70-80% complete.  Two AMI pilots have also been completed in preparation for a full AMI implementation.

The existing grid in Naperville consists of relatively new assets as a result of the significant growth that the city saw in the 80’s and 90’s.  Distribution Automation is already 80% complete using switches from S&C Electric in Chicago.  Distribution automation switches come in pole mounted formats for overhead distribution and in pad mounted formats for underground distribution.  Since over 90% of Naperville’s distribution network is underground, the majority of existing switches are of the pad mounted variety.  These switches allow the grid to reconfigure itself automatically when a fault occurs in the network.  All sections of the grid are connected to multiple substations, providing multiple paths for power to flow to that section of the grid.  Under normal operations, the switches are configured in such a way that the load is balanced among the various substations in an optimal manner.  However, in the event of a fault which causes loss of power to some sections of the grid, these switches automatically open or close to reconfigure the network, restoring power to the impacted customers and isolating the faulted section of the grid.  By completing the distribution automation implementation, the city expects to achieve significant additional reductions in the outage time experienced by its residents.

Another major objective of Naperville’s project is to implement VOLT/VAR optimization to increase power quality and minimize losses due to distribution inefficiency.  Energy losses in a distribution network are proportional to the product of the resistance and the square of the current magnitude.  The resistance of a conductor cannot easily be changed but the current flow can be managed.  Current flows can be defined as active and reactive.  Active current flows occur when the waveforms of the voltage and current are synchronized producing net energy flow towards the load devices.  Pure reactive flows occur when the voltage and current are 90 degrees out of phase resulting in energy ebbing and flowing during each half of the waveform producing zero net energy flow.  In a real world electrical circuit, inductance, which reduces reactive power, and capacitance which increases reactive power also play a role so there is a combination of active and reactive power flows.  Reactive power (VAR) can be regulated in the grid by means of compensation devices such as switched capacitor banks.  Voltage can also be regulated to follow demand more closely using special voltage regulating transformers at the substations and at key points along the feeder lines.  The net result is lower demand requirements due to reduced reactive power flows and being able to operate the feeder lines at lower voltages.  A Smart Grid implementation of VOLT/VAR optimization, such as that which Naperville is implementing, leverages sensing technology from substation and distribution automation along with advanced modeling techniques to create a more integrated grid level response as opposed to the more localized responses that were previously available.

Other portions of the Naperville Smart Grid Investment Project include:

  • Implementing customer portals to allow customers to monitor their own consumption and provide access to service information.
  • Provision of in-home real time energy consumption meters on a voluntary basis.
  • Implementing Automated Metering Infrastructure using smart meters to provide two way communications between the utility and the consumer.
  • Implementing a load control program to analyze the effectiveness of this approach for achieving demand curtailment during peak demand periods.
  • Preparing the grid to be ready for the anticipated adoption of electric vehicles which have the potential to put significant additional stress on the distribution network especially the local transformers.

On the day that Mark Curran and Allan Poole came to talk to the Green Technology Organization of Greater Chicago, the city had held a mandatory pre-proposal meeting for vendors interested in bidding on the AMI, Load Control and HAN portions of the project.  The utility plans to install over 57,000 smart meters (~50,000 residential and 7,000 commercial/industrial customers).  They are technology agnostic and will select a solution that best meets the needs of the community based on the proposals received.  The meeting was attended by 55 people.  On the same day, the RFP for the MDMS and e-Portal portions of the project were released for bid and a pre-proposal meeting for these sections is scheduled for August 10.  Proposals are currently under evaluation for the distribution automation portion of the project.

At a total cost of $22 million, half of which is being provided by a matching grant from the stimulus program, the estimated net present value of the Naperville Smart Grid Investment Project is $34 million.  If carbon were to be priced at $20 per ton, this would increase the NPV of the project to $52 million due to the carbon reductions that are projected to occur as a result of the program.  The project is expected to take around 3 years to complete with ~90% of the funds projected to be spent by mid-2012.  Analysis done by West Monroe Partners indicates that the adoption of electric vehicles could double the cost savings from this project.

In summary, Naperville expects this project to help it and its customers to:

  • reduce meter data acquisition costs,
  • maintain and further improve the reliability of its electrical service,
  • control operational costs and optimize the use of human resources by enabling self-healing within the grid,
  • improve operational efficiency and infrastructure security through real time access to substation and distribution network status,
  • enable remote disconnect and reconnect operations to streamline the process of handling customer move-in/move-out events,
  • improve outage detection and reporting of outage occurrences and expected restoration to consumers
  • support variable rate plans, energy conservation and enabling of smart home controls via the AMI network,
  • provide access to improved data for engineering studies and projects to further optimize and/or upgrade the grid.

Coming next:  The Illinois Statewide Smart Grid Collaborative is meeting on August 19 to finalize their report to the State of Illinois on Smart Grid strategies.  A draft document by the collaborative provides a wonderful summary of various smart grid applications and their benefits to various stakeholders.  I have been studying this report and plan to summarize sections of it in the blog over the coming weeks.

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Responses

  1. Great synopsis of the ongoing Naperville Smart Grid project!


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