To quote Sherlock Holmes in The Adventure of the Beryl Coronet: “It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth.”

Conductor pulling had reached the last few spans when the breaks occurred. Based on the forensic test results, it was decided to leave in place the 14 miles (22 km) of ACCC/TW wire that had been installed, but not to install any ACCC/TW conductor from reels associated with the conductor breaks. This was done as a precautionary measure, not knowing the manufacturing history of this conductor. Standard ACSR Drake conductor was installed for the final mile, and the line was energized on schedule.

Based on all the evidence and experience to date, AEP plans to replace the final mile of Drake ACSR with ACCC/TW by the year's end.

ACCC/TW is a product with high-temperature sag advantages over existing ACSR technology. After one major project, AEP's knowledge of ACCC/TW has grown, as has its active interest. In fact, the new Leon Creek-Pleasanton line is another important step in the company's embrace, and management, of new technology.

James J. Berger began his career in 1984 with Central Power & Light Inc. in distribution planning, operations, design and construction. In 1992, Berger became director of Standards and Compatible Units with Central and South West Services Inc. Since joining American Electric Power in 2000 as director of Transmission Line Projects Engineering, Berger's responsibilities have included standardizing materials used in designing distribution electrical systems, developing corporatewide compatible units for use in the corporate work management system, developing an outage reporting system and implementing a mobile computer-based system for use by service personnel. Berger holds a BSEE degree from Texas A&M University and is a registered professional engineer in Texas. JJBerger@AEP.com

When CTC and General Cable heard about conductor breaks at the Leon Creek installation, the team immediately began investigating possible causes. A thorough examination of manufacturing and quality disciplines was undertaken and all records were assembled.

The first break was a result of the conductor jumping off the bull-wheel tensioner and wrapping around the axle; therefore, it was easy to resolve. The other two breaks were not so obvious and did not become apparent until after conductor tensioning.

Extensive forensic investigations confirmed that the core break was a result of being bent around too tight of a radius. However, questions still remained:

• What caused the core to bend to such a degree?

• Could some type of production anomaly have caused a weakening of the core's flexural strength, and if so, how could that have been prevented?

• What could have possibly caused damage to the core during the wrapping or shipping process to compromise its strength?

Improper installation methods seemed the obvious explanation, especially considering the bull-wheel incident and that more than a dozen other installation projects had been completed without similar incidents prior to the Leon Creek installation. However, definitive evidence was not available or apparent.

The General Cable/CTC team undertook an intensive review of all its manufacturing, quality-assurance and field-support procedures. The outcome of the review resulted in several proactive measures. Because field training is mission critical, a new installation manual was developed to help field supervisors avoid potential problems. Linemen training, preconstruction meetings and construction support measures were stepped up. Enhanced inspection devices were added throughout the manufacturing process.

Additionally, CTC instituted more stringent manufacturing controls including: laser sensors for filament in-feed tooling, redundant thermocouples to ensure proper die curing temperatures and a novel in-line continuous flex test to ensure that every millimeter of core produced meets all strength requirements.

As a result of these enhanced quality-control measures, CTC, General Cable and AEP are more confident than ever in the performance capabilities of ACCC.