Proactive Prevention to Enable Cost-effective Maintenance

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As an increasing portion of the transmission network in North America approaches the end of its anticipated useful life, asset owners are taking more proactive steps to better understand the health and condition of their transmission line assets.

Since aging conductors frequently drive the replacement and rehabilitation of transmission lines, specific interest in the condition assessment of conductors and shield wires has grown significantly in recent years.

The client

Great Lakes Power (GLP)

Objective:

Background:

Two main mechanisms cause conductors and groundwires to deteriorate due to natural aging processes: loss of fatigue strength due to wind-induced vibrations; and loss of tensile strength due to corrosion.

A number of transmission line circuits on GLP’s transmission network exceeded an in-service age of 40 years. Although the performance of the lines had not suffered so far, due to the advanced age of the lines, GLP management took a proactive approach to establish the health of conductors and shield wires, by assessing the degree of corrosion through laboratory testing.

During the recently completed phase of the project,12 samples, obtained from strategic locations on five transmission line circuits, were thoroughly tested. Results were analyzed and the physical condition of transmission line circuits was quantitatively ranked through the following tests:

• Close-up visual examination in lab
• Tensile strength measurement through lab testing
• Torsion ductility measurement through lab testing
• Remaining thickness of zinc layer measurements through lab testing

Criteria for ranking of the overall condition of the transmission line conductors were developed by the appropriate weighting of results from different lab tests. The condition of each transmission line was ranked based on the established criteria.

Results:

The tests provided an extremely valuable snapshot of the present condition of the client’s transmission line conductors.

In spite of the advanced in-service age of the transmission lines, a majority of the circuits were found to be in either very good, good or fair condition. A few specific line sections in "marginal" condition were also identified.

Client benefits:

Great Lakes Power concluded that the project had been a very cost-effective exercise in establishing the health and condition of selected aging transmission lines on the network.

Based on the test data, it became possible for the client to accurately prioritize and in some cases, defer a number of planned capital investments.

The project results also enabled effective prioritization of the client’s monitoring and preventative maintenance efforts to areas where it was needed most.

Comprehensive Testing Services

For over 15 years, Kinectrics has been developing, improving and perfecting the techniques for reliably and objectively assessing the condition of aged conductors and shield wires, in partnership with our major transmission clients.

Typically in-situ conductor assessments may include foot patrols, aerial inspections, close-up visual examinations from bucket trucks, infra-red scanning and dimensional measurements of steel wire cross-section and the zinc layer carried out by joint teams of Kinectrics and client staff.

In addition, Kinectrics has developed criteria for ranking the present condition and estimating the remaining useful life of conductors. Major lab tests performed by Kinectrics in assessing the health and remaining useful life of conductors include:

• Aeolian Vibration Endurance Test
• Galloping Endurance Test
• Sheave Passing Test
• Torsion Ductility/Tensile & Elongation Failure Tests
• Creep Test
• Remaining Zinc Test
• Wrap Test
• Electrical Resistance Test
• Metallurgical Examination
• Chemical Analysis & Accelerated Corrosion Test

For more information, contact

Craig Pon, 416.207.6000 x6741, craig.pon@kinectrics.com