T&D World Magazine
Burns  McDonnell Arizona Public Service flexible grid

APS crew prepping the new recloser before it is installed.  View full T&D HOW video: How to Change Out a Recloser.

Evolution to a Flexible Grid

Arizona Public Service implements tools and infrastructure vital to improving the customer experience and future utility success.  

Over the years, industries have evolved to meet the growing needs of their customers and communities by embracing new technologies. Computers have become smaller and more mobile. Cellular phones have become smarter and more functional. Automobiles have become safer and more dependable. Electric utilities are no exception. Arizona Public Service (APS) is one such utility using new technologies to optimize reliability and performance, empower customers, extract business intelligence from data and enable alternative energy delivered over the flexible grid of the future.

Founded five years after the legendary gunfight at the O.K. Corral in Tombstone, Arizona, U.S., APS is Arizona’s largest and oldest electrical utility, serving more than 1.2 million retail and residential customers in 11 of Arizona’s 15 counties. The utility’s corporate vision is to create a sustainable energy future for Arizona by using innovative technologies, renewable energy sources and energy efficiency. APS has held true to its vision by deploying more than 1,223 MW of solar generation, placing it among the top five in the industry. APS also has strategically embarked on comprehensive advanced grid initiatives throughout its system, ranking it as a top 10 utility in this space.

To continually generate and distribute reliable, sustainable energy for the businesses and residents of Arizona, APS has long known the current state of the electrical grid would be inadequate. Advanced technologies would be required to transition toward an electrical grid flexible enough to handle the energy demands of the 21st century.

Why a Flexible Grid?

APS foresaw the grid of the future would need to have dynamic capabilities the original grid was never designed to have. In 2013, the utility developed its Grid Modernization Ops Vision 2025 strategic plan, which set the direction for deployment of advanced grid technologies to increase the visibility and automation capabilities of its distribution grid. One of the challenges being solved by the flexible grid is the ability to handle two-way power flow due to the increased penetration of distributed energy resources (DERs), such as rooftop solar and energy storage.

The ability to redirect power flow in the event of an outage gives APS a way to bring critical loads or customers on-line faster. Unfortunately, traditional relay coordination proves to be a major hurdle when redirecting power flow through the distribution network. Protection and automation devices are needed beyond the substation. They must be located throughout the grid to allow for dynamic changes to individual distribution systems.

It is important not only to manage and correct power flow, but also to monitor and adjust voltage on demand. Having dynamic voltage variability enables APS to correct for load variances immediately instead of seasonally. Using two-way communications (between the equipment and control center) and integrated volt/volt-ampere-reactive controller (IVVC) technology on regulators, capacitor banks and reactors, the utility can respond instantaneously to power-quality concerns. A robust communications network is needed to enable these devices to react appropriately. This is why it is critical for the IT communications infrastructure plan to be in sync with the advanced grid technology deployment plan.

Just as loads can vary across APS’s system, intermittent energy sources vary, as well. By definition, intermittency of an energy source means the power output of a DER cannot be directly controlled. Wind and solar generation are perfect examples of an intermittent energy source because the main variables are mostly unpredictable. The strength and direction of the wind, intensity of the sun or amount of cloud cover are all uncontrollable variables.

Burns & McDonnell, Arizona Public Service, flexible grid
APS manages the grid from its distribution operation center.

This is why, nationally, most DERs currently are used merely to displace traditional fuel consumption in nonrenewable power plants or in conjunction with energy storage devices. As the demand for residential and commercial energy storage grows, and the advancement and reliability of battery technology increases, the capital investment cost of this technology will be accepted more widely.

Operationally, planning generation production has become increasingly difficult with the proliferation of rooftop solar and other DERs on the system. Fast-response energy storage, coupled with solar production metering, will enable APS to respond to DER intermittency. To get ahead of the ever-growing rooftop solar industry in Arizona, APS has developed the nation’s first solar partner program. The program enables APS to use residential rooftop infrastructure to study the real-time capabilities of advanced inverters within an actual utility system.

Along with the solar partner program, APS has been experimenting with various technologies for years in small areas to verify feasibility. APS also has developed a series of data analytics applications to get a better understanding of its data. One such application is solar forecasting and visualization. This is a geospatial application that is taking solar production advanced metering infrastructure (AMI) data from 40,000-plus rooftop solar systems. The data provides situational awareness and also day-ahead forecasting for distributed solar generation. This improves marketing and trading as well as operational planning.

APS crew installing a nova recloser. View full T

Launching Technology

APS’s big push for a flexible grid began in 2007 with the deployment of its AMI, which enabled two-way communication with meters, a major change from the traditional meter reader. This technology’s advanced capabilities such as remote connects and disconnects of services and enhanced data collections allow for improved corporate efficiencies by drastically reducing drive time for service personnel (less maintenance, lower fuel costs, reduced risk of motor vehicle accidents and less pollution), providing improved response time for customers and developing a better use of human resources.

With nearly 1.3 million advanced meters installed, AMI also is providing operational and planning benefits to APS by enabling voltage, outage and transformer load management. Additionally, the variety of billing options supported by AMI has proven to be a big customer benefit, allowing them to control home energy usage and lower electricity bills.

APS understood giving the operations personnel the high-tech tools needed to manage the ever-changing flexible grid was critical. In doing so, the next phase of deployment was the implementation of the distribution outage management system, which enabled the operators to move from a paper mapping system to a more accurate digital system. This was a significant upgrade to how business was done, and the capabilities AMI provided could be better utilized. Now with digital visibility of the grid, APS has moved forward by experimenting with various technologies in small controllable areas.

APS linemen prepare to install a new line capacitor bank. Click on the image to see the full T

An Advanced Grid

Between 2009 and 2012, APS launched several advanced grid pilot projects to understand some of these technologies better. In Flagstaff, Arizona, APS experimented with an area-wide fault location, isolation and self-restoration (FLISR) network using communications-assisted switching cabinets among other equipment. This enabled APS to test various equipment and technologies while validating whether the application was feasible on a statewide scale. This pilot system laid the foundation for APS’s current advanced grid capabilities and is now being implemented in other areas across the state.

APS crew replacing a switching cabinet in downtown Phoenix. To view full T

Another APS project was the implementation of IVVC technology on the distribution network that enabled optimization of voltage and VARs on individual feeders. The increased deployment of this technology will enable APS to operate distribution capacitor banks and regulators remotely to adjust power-quality issues in real time. Along with monitoring power quality, APS has strategically placed communicating fault indicators throughout the distribution network to help pinpoint fault locations, giving operations and maintenance crews the ability to respond and reduce outage durations quickly for customers.

In 2013, more advancements to the APS grid came in the form of recloser technology, a protective device used mostly on overhead distribution lines. The deployments started with dozens of installations and are now projected to hit more than 100 in the next few years. APS is currently using three-phase reclosers with two-way communications to replace old motor-operated switches. These same reclosers also can be used as sectionalizers on a line and have built-in control systems that can detect high impedance faults, an issue APS has struggled with for decades.

Recently, there has been a push to replace fuses with small single-phase reclosers — also known as trip savers — that fit on traditional fuse cutouts. This device will only open on permanent fault conditions but reclose back to normal on a temporary fault (that is, a falling tree branch, lightning and wind slapping two phases together), thus reducing the instances linemen need to be dispatched simply to replace a fuse. This is especially important in rural, remote areas where hours of travel time are required.

These advanced grid programs and technological advancements are providing the public with a safer and more reliable grid. They also give operations the flexibility to operate the grid in a way that minimizes the number of customers lost during an outage, especially during storm-related outages. Restoration is greatly improved because the operations team has greater visibility and control with the various communicating devices deployed in the system.

APS linemen lift a new line regulator into position. To view full T

What's Next?

Future advancements to APS’s flexible grid will come with the implementation of the advanced distribution management system (ADMS), which includes outage management, distribution management, and distribution supervisory control and data acquisition (SCADA) system applications. ADMS will provide visibility and automation by integrating data provided by smart sensors (fault indicators, automated switches, reclosers and cap bank controllers) and advanced meters connected to the grid. For example, ADMS will provide several outage management tools to manage crews, trouble calls and notifications.

Operators also will gain situational awareness of the system and the ability to control breakers and other feeder devices remotely as needed. Additionally, APS will be able to run applications for load flows, fault locations, event playback, restoration switching analysis and even training simulators.

Having these tools and infrastructure in place are vital to APS’s success and the improvement of the customer experience, as APS foresees continual growth in distributed solar generation, residential energy storage, microgrids, home energy management systems and an infiltration of electric vehicles throughout the transportation market.

An APS lineman installs trip savers in fuse cutouts. To view full T

An APS lineman installs CFIs on the distribution line. To view full T


Jonathan Dusenberry is a senior electrical engineer at Burns & McDonnell. He has more than eight years of T&D-related experience and is currently serving as a T&D project manager for Arizona Public Service.

Adolfo Maldonado is a senior electrical engineer at APS in the T&D engineering and standards department. He has 15 years of experience in the utility industry, spanning both the generation and T&D sides of the business.

Jasdeep Singh is the manager of advanced grid technologies at Arizona Public Service, responsible for the strategic planning of advanced grid technologies and advanced data analytics.

Chad Lonski is the manager of distribution maintenance at Arizona Public Service, where he has been employed for the past 10 years. He has been in the utility industry for 17 years, spending time in the field as a lineman and in various management roles.

Editor’s note: Videos of the APS installations mentioned in this article can be found at tdworld.com/videos/td-how.

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