Distribution Automation: Reducing Energy Losses and Improving Reliability

Distribution Automation: Reducing Energy Losses and Improving Reliability

This piece was originally published in the April 2017 issue of electroindustry.

Bill Flerchinger, Technical Marketing Manager, Schweitzer Engineering Laboratories, Inc.

More and more utilities want to take advantage of technology such as microprocessor-based controls and computing platforms, revolutionary communication technologies, sensor technologies, advanced algorithms, and advanced coordination of devices for holistic system optimization. To do this, the name of the game is automation.

Several challenges, however, continue to slow the attainment of this distribution automation (DA) nirvana, namely financial obstacles in the form of capital costs pertaining to implementation; integration challenges associated with communications and combining new and legacy systems; and fundamental operational design that changes the way we’ve always done it. Making sense of the costs and benefits often requires the help of professionals experienced in examining and explaining the complete picture of potential advantages and drawbacks.

What if we could just focus on a dream system? What does a modern, optimized, state-of-the-art DA system look like?

That’s what one utility set out to discover in 2010 when it agreed to participate in a Department of Energy (DOE) smart grid project. Just how beneficial would automating their distribution system be? The answer: very.

The three-year SmartStar Lawrence project installed advanced metering infrastructure, a meter data management system, and DA. Investor-owned electric utility Westar Energy, based out of Topeka, Kansas, began with a wish list for its DA system. At the end of the DOE pilot project, they wanted their DA system to

  • increase system reliability;
  • reduce outage restoration times;
  • minimize distribution system losses;
  • reduce system loadings during peak conditions;
  • improve system operation and understanding;
  • improve service to customers; and
  • have the ability to pass information from DA system to their existing energy management system (EMS)/SCADA, i.e., with no new interface.

The idea behind the project was that economically adding automated fault location, isolation, and service restoration (FLISR), as well as voltage and reactive power (volt/VAR) control, would improve reliability and reduce system losses, delivering a highly beneficial project to Westar and its customers.

Operational Design

Westar’s new DA system was implemented on 20 of the 1,338 circuits across its distribution network. The feeder circuits used reclosers at normally open tie points to interconnect two or more power sources. Additional reclosers were installed throughout the feeder circuits to allow sectionalizing capabilities in the event that permanent faults occurred on a line section.

The new system included the following equipment:

  • Advanced recloser controls (33 units) and satellite-synchronized clocks (33 units) paired with reclosers
  • Legacy recloser (1 unit) with form 6 controls
  • Capacitor bank controls (53 units) retrofitted to existing capacitor banks
  • Existing non-telemetered switches (39 units)
  • Wireless 3G and 4G cellular modems (87 units) for feeder intelligent electronic device (IED) communications and control
  • Real-time automation controller (1 unit) as a distribution automation controller (DAC), providing centralized system intelligence
  • Ethernet security gateway (1 unit), providing comprehensive security measures and automated event collection capabilities from IEDs

The SEL DAC communicates with the substation breakers and protective relays through messages relayed by the EMS/SCADA system to the substation remote terminal units. In order to maintain an awareness of system configuration, a server-based software solution was developed that monitors the company’s outage management system and provides the status of the non-telemetered switches in the system back to the DAC, thus maintaining awareness of abnormal operating system conditions.

System components include advanced recloser control, satellite-synchronized clock, and wireless 3G cellular modem. Photo courtesy of SEL

The modernized design allowed for the implementation of several communication protocols across the system. The protocols were selected either to provide desired IED functionality or to accommodate legacy equipment limitations.

In turn, the DAC acts as a protocol converter, allowing the various IEDs in the DA scheme to communicate and operate as a holistic system. The DAC provides port-routing functionality for remote-access capabilities using various proprietary vendor software interfaces. This allows for the use of a mix of new and legacy IEDs, as well as controllers from different equipment manufacturers, thus minimizing the installation time and cost of implementing the system.

Leveraging Existing Technology

Since the automation system was deployed primarily for system restoration and VAR control, high-speed communications were not required. The design, deployment, and maintainability of a company-owned communications system would require a significant capital investment and result in long-term operation and maintenance expenses, although there would be no recurring carrier charges.

This type of deployment would have stressed the existing and future technical workforce at Westar. Planned obsolescence also needed to be factored into the system, which would have required another future capital-intense system upgrade of the communications network. It was for these reasons that Westar chose to leverage cellular technology.

Cellular communications allowed Westar to minimize deployment times since there was no backend infrastructure to build and maintain. Although there are ongoing data charges, rate plans were negotiated with the cellular providers, which offset the costs that would have been associated with a company-owned system. The cellular network is continually being built to incorporate new technologies with increasing data throughput rates and decreasing costs of data plans.

System Implementation

Westar Energy and SEL Engineering Services implemented the DNA system in two phases, starting with the fault location, isolation, and service restoration (FLISR) capability (phase one) and then adding volt/VAR control capability (phase two). This allowed the reclosers to be installed initially, followed by the replacement capacitor bank controls and LTC integration at a later time. SEL provided the initial FLISR and volt/VAR programming by creating a system model and configuring standard DNA libraries for the Westar Energy distribution system. Human-machine interface (HMI) displays were also developed for use during commissioning and testing.

SEL provided remote interactive training so that engineers at Westar would be proficient at maintaining and implementing changes to the system to accommodate additional IEDs or feeder circuits in the future. Westar engineers further developed and implemented features in the system, including the deployment of automated password management, remote IED management capabilities, automated text and email routines, and HMIs to aid with routine system operations.

Human-machine interface and distribution automation EMS screens aid with routine operations. Photo courtesy of SEL

Phase One: FLISR DNA System Capabilities

Centralized automated controls were added that perform autonomous fault location, isolation, and service restoration activities. The SEL solution included the following features as part of the FLISR functionality:

  • Loss-of-source detection
  • Open-phase detection
  • Discoordination detection and mitigation (provides operator notification and sectionalizes the correct portion of the system with the fault)
  • Overload mitigation and load shedding (smartly selects an alternate source with available capacity, shifts sources if loading increases beyond limits, or sheds load if no alternate sources with capacity are available)

Phase Two: Volt/VAR Control

The implementation of automation and control for voltage and reactive power will use the same centralized system DAC and feeder information but will add control of voltage regulators, capacitor banks, and substation transformer LTCs to the system model. This simplifies the effort to add volt/VAR control while allowing both systems to operate as an integrated system. A benefit of implementing the system in this manner is that, even after system reconfiguration, volt/VAR capabilities could still be performed on the reconfigured system.

Currently, the system is fully integrated with capacitor banks, but full LTC control is still being implemented. The system has been operating in a VAR optimization mode only, but benefits in efficiency have already been realized. Moving to a full voltage control mode will allow for even more operating benefits.

Volt/VAR may be optimized for specific feeders. Photo courtesy of SEL

Flexible operator control modes are used to optimize

  • voltage on the feeder;
  • power factor (PF) on the feeder;
  • PF on the station bus;
  • demand response for peak load reduction; and
  • VAR set point on the primary side of the transformer for transmission VAR support.

Additional System Benefits

Secure communication to substation and feeder devices enables remote engineering access. Westar engineers can retrieve and change IED settings, as well as pull event data (sequential event records and oscillography) from all devices on a feeder circuit, facilitating faster event analysis and helping to refine settings for improved system operation and protection. Westar also implemented automated password management and automated text and email messaging routines for configured alarms and events.

Example of oscillography centrally retrieved from remote IED speeds event analysis. Photo courtesy of SEL

The system has successfully handled many faults and correctly performed automated reconfiguration on four different permanent fault events. It is estimated that these restoration events resulted in a savings in customer minutes interrupted (CMI) of 211,382 minutes. The system identified sympathetic faults on feeders in the automation scheme. As a result of remote data collection capabilities provided by the system, engineers identified two separate incidents involving locations upstream of faulted line sections in which conductors were “slapping” together due to magnetic fields associated with high fault current levels.

Another benefit of adding reclosers and recloser controls to the system is the reduction in customer interruptions, even without FLISR system interaction. The reclosers alone eliminated approximately 587,000 CMIs.

There were valuable lessons learned during design and implementation:

  • Building relationships with IT groups and personnel involvement, including IT security, was instrumental to successfully designing and securing the system.
  • Early-stage and continuing cross-functional group communication was key.
  • New devices deployed en masse, in contrast to a small trial installation, resulted in some challenges with wildlife protection.
  • The use of cellular modems required some communications handshaking and latency issues to be overcome, some of which required vendor firmware modifications.
  • Autonomous (closed-loop) system acceptance by operating groups was aided by education and training.
  • “Fault bit” logic in recloser controls and an early warning system for problem areas was beneficial.

Decreased Losses, Increased Sustainability

Westar’s new economical and cost-effective DA system is providing a fully automated FLISR and VAR distribution solution, with voltage control soon to be implemented. The system can translate between various communications protocols and seamlessly interface with Westar’s existing EMS system, leveraging some of Westar’s existing legacy equipment and positioning the company for future enhancements.

Deployment of the SEL DAC and security gateway hardware at Westar has opened the door to a system-wide modernization of communication devices across their service territory. The systems have been designed to maximize system effectiveness, improve system awareness, and increase work efficiencies, thanks primarily to new remote access capabilities.

The Lawrence area is benefiting from improved system reliability and reduced system losses, resulting in a win-win for Westar Energy and its customers.

Joanna Hofer, SEL, and Mike Watson, Jeff Hauber, Clayton Stubbs, and Matt Bult, Westar Energy, contributed to this article.

One thought on “Distribution Automation: Reducing Energy Losses and Improving Reliability

  1. Under “Leveraging Existing Technology”, use of cellular technology is mentioned. What other existing technology was leveraged?

    Was a HAZOP or risk assessment done on using cellular technology versus other means?

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