For More than Five Years, the City of Westerville, Ohio, has maintained a system average interruption frequency index (SAIFI) below 1.75. A four-year recipient of the American Public Power Association's (APPA) RP₃ — reliable public power provider — quality designation, the Westerville Electric Division as been identified by APPA as one of the top 84 (out of 2000) municipal power utilities in the U.S. Maintaining the RP₃ designation and working to continually improve reliability are Westerville's top priorities.

There is nothing radically innovative in Westerville's maintenance strategy. The public power utility does annual rebuilds of both overhead and underground segments. It performs annual substation maintenance and year-round vegetation management. And it prioritizes the replacement of defective equipment such as 69-kV insulators, polymer arrestors and deadend insulators on overhead facilities. However, if there is one thing that distinguishes Westerville's approach to reliability, it is the utility's willingness to explore new methods and technologies.

A NEW TOOL HITS THE STREETS

In early 2007, Exacter Inc. (Columbus, Ohio) approached Westerville with a new technology that could help the utility preempt and prevent power outages by identifying distribution line equipment that was about to fail. Westerville agreed to let Exacter survey its grid and report on the findings.

The EXACTER Outage-Avoidance System was mounted in Westerville's vehicles. As the utility staff drove along the various circuit routes, the system identified failure signatures (arc and partial-arc sources) that were coming from the overhead lines. The system would lock in on the signature of particular overhead line emissions and filter out unrelated noise from other sources. The failure signatures were captured along with GPS coordinates and relayed to a server for analysis. Potential problems were prioritized and locations were identified and mapped.

THE TOOL IN ACTION

As Exacter's first customer in 2007, Westerville became a voice that helped to shape their outage-avoidance system's product development. The public power utility's first report revealed an excess of 1100 emissions locations on its 135 miles (217 km) of overhead distribution. This was clearly overwhelming, not to mention unmanageable for a small utility.

Exacter personnel understood Westerville's concern and continued to survey and analyze the data. After three months in the field, Exacter was able to pare down the original 1100 emissions locations to 45 significant problems, a manageable number. Westerville sent its line crews out with Exacter and some common radio frequency interference (RFI) locating equipment to find out if the 45 locations were really problems.

The Westerville field team was naturally skeptical about the new technology. However, as the team began to go from point to point, confirming the interference at each location, they began to notice something was being identified. They would change out the indicated equipment and retest with the RFI equipment and the previous emissions would be gone. Of the 45 locations identified by the system, 43 turned out to be equipment that was indeed failing or required maintenance.

A VALUABLE FIND

Knowing the location of every failing pin insulator or tie-down on a small residential circuit is fine, but the real value comes when more-significant problems are uncovered. One of the locations identified early on was a vital interconnection: a 69-kV transition from overhead to underground that serves five of Westerville's six substations. Some minor arcing was identified at the interconnection.

Upon investigation, Westerville discovered one of the arrestor leads was completely burned and the other two were in the process of burning. The source was a cable shield strap that attached just below the termination. It had broken loose, probably due to wind. After the termination ground broke loose, it blew around in the wind, and when it contacted the arrestor lead, it formed a circuit, which caused the burning. There were also burned cables going underground. This was an imminent failure that would have taken out 80% of the city's system and would have resulted in a significant rebuild. Because this particular problem was located not on a street but on a remote bike path, it was relatively hidden from normal driving patterns.

A SMOKING CROSSARM

One uncertainty with Exacter data exists: When will the item actually fail? Will it be in two weeks or two months? Westerville's line crew was investigating a flagged location. Upon arrival, the crew noticed smoke coming from where the crossarm brace attached to the crossarm. It became obvious to the crew that one of the aluminum cap deadend insulator bells had failed. After workers isolated the deadend, the smoking stopped. Had they not been alerted to the problem, the crossarm would have burned in two, taking out power to 551 customers.

Worse would have been the possibility of a significant calamity caused by the line falling as part of the ensuing failure. While switching and isolating minimized downtime to about two hours, had the problem not been avoided, it would have resulted in the need for a substantial rebuild.

HARDENING FOR THE SMART GRID

Westerville's experience with the EXACTER Outage-Avoidance System also uncovered another potential benefit. The utility is hardening its distribution system in preparation for implementation of Smart Grid features, including advanced metering infrastructure (AMI). It only takes one loose pin insulator or component creating interference to stop the transfer of billing information from the AMI system. Some of the line interference locations may not be critical for overall distribution reliability, but eliminating this interference is critical for reliable communications. By hardening the distribution system in advance of AMI deployment, the utility is not only troubleshooting problems, but also improving the overall environment of its system.

PRIORITIZING KNOWN PROBLEMS

Over the last couple of years, Westerville has been replacing its 20-year-old aluminum cap deadend bells with increasing frequency. Knowing this problem would be escalating over the coming months and years, the utility asked if Exacter could provide a report to help identify the most-significant deadend bell problems.

The Exacter report the utility received not only broke out all the deadend bells, but also provided a Group Maintenance Merit measurement that identified the units exhibiting the worst signs of failure. This helped the utility to prioritize its change-outs and set up a maintenance schedule that would preempt the most-likely outage sources.

A MYSTERIOUS LINE INTERFERENCE

Several months after one of the surveys, Westerville started receiving a significant amount of customer complaints about a recurring flicker problem. The utility sent technicians out several times over a two-week period, but the cause could not be located.

The electric field superintendent suggested checking the old survey data. Sure enough, there was a problem location on that circuit. When the utility went to the specific location, it identified that the stinger (a conductor or wire that attaches equipment to the distribution feeder) had a hard-to-find intermittent connection that was causing the problem. The repair was made, and the customer problems disappeared. Having the survey data directed the utility to the problem.

A STRATEGIC TOOL

Westerville has been fortunate to have budgets for regular line rebuilds, but as the utility has used EXACTER to make predictive repairs, this process of preempting problems opens up some interesting possibilities. What if instead of investing in a complete line rebuild of a problem circuit, the utility reallocated the dollars — taking a fraction of the budget to simply harden the hot-spot area with targeted repairs, and using the bulk of the money for other system priorities? Presently, this is a hypothetical scenario, but the system intelligence data the surveys provide certainly could be a vital solution component for utilities struggling with ever-tight budgets and increasing workload.

Westerville has used the EXACTER system for more than two years. The utility is currently surveying its grid twice a year, receiving information it cannot get anywhere else. If the utility can stop a pole fire or avoid a significant section of the grid from going down, the outage-avoidance system pays for itself many times over.

While preventing outages is a tangible benefit, the EXACTER system is more of a strategic information tool. When the utility receives the survey data and sees which particular areas in the system have a greater concentration of problems, it helps Westerville to make more-informed decisions about where to spend line-rebuild resources. Or, if Westerville managers can identify some hot spots in specific areas where work is being done, without much extra effort, quick change-outs can be made that are truly proactive, predictive maintenance. The Exacter tool can help the utility to work smarter and make better decisions.

Achieving reliability is still an inexact science, but with tools like this, utilities can get a much-clearer picture of what is happening on their systems. Using this tool is being proactive about reliability. For Westerville, it's the most-affordable outage-mitigation tool — one that should become part and parcel to the maintenance budget of every utility.

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Andrew M. Boatright (Andrew.Boatright@westerville.org) has served as the electric utility manager for the City of Westerville Electric Division since 1996. With more than 27 years of experience in the electric utility industry, Boatright began his career as a distribution engineer with Public Service Indiana after receiving his BSEE degree from Purdue University; he then worked as a city engineer with the City of Rensselaer, Indiana; he followed that as chief electrical engineer for Richmond Power and Light in Richmond, Indiana. Boatright also holds an MBA degree from Otterbein College and is a licensed professional engineer in Ohio.

Problem found	Number
Pin insulators	18
Deadend bell insulators	8
Wires and grounding	7
Tie wires	2
Lightning arrestors	2
Jumpers at arm pins	1
Loose hardware	1
Stinger	1
Loose wires	1
Cable box	1
Loose hardware	1
Nothing found	2
Total	45

As a result of the City of Westerville Electric Division's experience with Exacter, the American Public Power Association issued a Demonstration of Energy-Efficient Development (DEED) grant for $58,000 for the utility to share its preventive-maintenance program, specifically featuring the use of new technologies to locate failing electrical equipment and improve overall distribution reliability. This report and associated video footage are now made available to APPA members under the Research & Development link on the APPA home page (www.appanet.org).

DEMONSTRATION OF ENERGY-EFFICIENT DEVELOPMENTS

City of Westerville Reliability Statistics

Index	2008	2007	2006	2005	2004
SAIDI (minutes)	63.92	61.33	71.18	37.35	88.62
SAIFI (outages)	1.53	1.48	1.52	1.35	1.72
CAIDI (minutes)	41.90	41.32	46.73	27.59	51.52
MAIFI (interruptions)	5.83	6.13	5.48	6.23	8.04
ASAI (%)	99.9878	99.9883	99.9865	99.9930	99.9831