Transmission Line Asset Management

Although many of the world’s major transmission systems were built in the 1960s and 70s during periods of high load growth, transmission lines built in the early years of the last century are still in service.

The industry continued to experience relatively high growth rates during the 1980s and expanded transmission facilities year after year. It was often more economical to replace a deteriorated plant by adding capacity to the new, higher-voltage, more efficient systems being built (taking advantage of economies of scale), than it was to refurbish the deteriorated plant.

The objective of the Transmission Line Asset Management Interest Group (TLAM) is to bring together interested parties to exchange information on asset management methods and techniques and to facilitate research that will optimize the management of transmission line system assets (overhead). A key thrust will be to extend the life of existing assets or to implement sufficient upgrades to them, and thus defer or eliminate the need for major capital expenditures for new transmission systems.

Topics and Issues:

• Implementation of an Asset Management Guide
• Assessment of the current condition and reliability of lines and prediction of the remaining life of components
• Assessment of available technologies and practices
• Methodology for risk assessment and decision analysis to undertake a reinforcement or a refurbishment and life-extension program
• Methodology and products to develop optimum use of existing lines
• Methodology and products for the optimization of line maintenance
• Means of controlling or mitigating environmental constraints and disasters

Current Projects

• State of the Art Study on Unmanned Aerial Vehicles (UAVs) for Transmission Line Asset ManagementThe objective of this project is to complete a state of the art study on the potential use of UAVs for transmission line asset management, i.e., inspection, data acquisition, maintenance and operations, as well as identifying added risks and benefits associated with UAVs as compared to manned aerial devices. The study will also identify government regulations, e.g., Federal Aviation Administration (FAA), that may impede or present complications in using UAVs for the purpose of transmission line asset management.
• Data Acquisition and Monitoring of Transmission Lines with High Resolution Satellite ImagesThe objective is to determine specific applications for high-resolution satellite imagery for the purpose of managing transmission line assets and data acquisition. This will be a pilot project focusing on one line section with a length of about 30 km. Based on the satellite information of the right of way and line details, an assessment will be made on the suitability of using the high-resolution data to manage transmission line assets. The assessment will include, but not be limited to the following asset management aspects: 1. Determination of vegetation type, health and risk to the system and whether the information can be used to support a NERC compliance audit; 2. Location and condition of right of way features, e.g., culverts, streams, bridges, access routes, trails, parks, water crossings, etc.; 3. Identification and inspection of line details, e.g., structure type, structure elevations, conductor elevations, aerial markers, leaning structures, switch location and type, etc.; 4. Capture of GIS data and suitability of using satellite imagery data versus field survey information.
• Composite Poles in Transmission & Distribution – Experience and IssuesThe objective of the project is to capture and document operational experiences and issues associated with the use of composite poles, cross arms and braces to provide utilities with a comprehensive reference as to the operational performance of these materials in the industry. Specifically the goals and objectives of the project are to identify and document construction, operational, and maintenance experiences associated with composite poles, cross arms, and braces used in low and high voltage facilities; to solicit and document feedback from manufacturers and vendors of composite poles, cross arms, and braces as to maintenance and operational and performance issues raised by utilities as well as how these issues were addressed; and to investigate and document financial and operational benefits that have been realized by utilities that implemented the use of composite poles, cross arms, and braces.
• Best Practices for Transmission Line Insulator Condition AssessmentThe objective of this project is to produce a best practices guide for transmission line insulator assessment that includes the various inspection techniques available in the electrical utility industry, with supporting documentation and rationale. The study will identify the pros and cons of each inspection method for the various types of insulators in use on transmission lines with further consideration given to the local environment where installed and climatic conditions that may exist at the time of testing. As well, the project will be structured in a way so as to allow transmission utilities to select the best method of insulator inspection/assessment for any particular insulator type and situation.
• Methodology for Ranking Transmission LinesThe objective of this project is to develop a methodology for ranking transmission lines in a network with due consideration to the parameters and criteria used by various departments in an asset management organization. Here the ranking of the transmission lines is defined as a score assigned to each circuit of the network based on the criteria defined by the various departments (system operator, system planner, asset manager responsible for maintenance/construction, customer relations, etc.) and which is aligned with the corporate risk tolerance and Key Performance Indicators (KPIs). The ranking should be usable for planning, prioritization and execution of maintenance activities, such as inspections and repairs, and capital work, such as refurbishment and life extension.
• Spare Part Strategies for Transmission Line AssetsThe objective of this project is to conduct a review of the spare part strategies used in various asset management organizations to develop a framework strategy based on industry intelligence. As a result of this investigation, a methodology shall be recommended for utilities to use for determining the optimum number of spares to stock, including items which are required in small numbers and which have long lead times for ordering.
• Failure Assessment of Power Connections under Elevated Electrical Load ConditionsThis project will address the mechanical, metallurgical and electrical properties of power connections and their stability under different operating and environmental conditions. This project will include identification and quantification of the major parameters determining the quality and life of power connectors in terms of their mechanical and metallurgical characteristics such as degree of deformation, stress relaxation, creep, fretting wear and corrosion; determination of the main causes of failure of power connections and establishment of the relationships between these degradation mechanisms and the measurable properties of materials involved; description of practical mitigating measures for slowing down connector degradation and restoring connectors’ original capabilities; development of a chart quantifying variations of the connector properties with its consumed life for each degradation mechanism; development of methods for the in-field sampling procedure and assessment of the actual condition of power connections; development of life estimation models for predicting the remaining life of power connections, their applicability and limitations under particular service conditions; and a detailed review of existing diagnostic and monitoring techniques of the power connection condition and assessment of their feasibility, accuracy, performance and simplicity for the in-field use.
• Conductor Vibration and Galloping in Transmission LinesThe objective of this project is to prepare a user friendly guide on the above conductor vibration modes to assist transmission utilities’ asset managers and maintenance personnel in planning the inspections of lines. This guide will describe how to detect early signs of damage, and how to control and minimize the wind-induced vibration and galloping-related damages and outages on their transmission lines. It will include a review of the work done to guide transmission line design, as well as pointers for inspection to reduce the impact of these vibration modes, and summarizing the available instrumentation and a realistic interpretation of its accuracy and limitations. The guide will identify those commonly used conductor types for which there is an absence of reference safe values, thereby indicating desirable direction for future research.
• Technology Review of Wood Pole TreatmentsThe project scope will include research into and a detailed assessment of available wood pole treatment methods, their applicability to various species of poles and their cost effectiveness in safeguarding against above ground and below ground pole deterioration due to infestations by decay fungi, insects, woodpeckers, etc., as mentioned above. The research will include a survey of utilities and industry service providers to gather information on the wood pole treatment services (test and treat) being used and to highlight the most commonly used treatments. The evaluation/assessment would be based mainly on the cost effectiveness of the treatment (i.e. identifying the treatment which provides longer periods between reapplication and the longest functional life for the utility wood poles at the best cost). However, the evaluation will give due consideration to and comment on products’ environmental impact, safety for the public and wildlife and regulatory compliance within various jurisdictions (products approved in one jurisdiction may not be approved in others).
• Technology Review on Best Practices for a Risk Based Approach to Vegetation ManagementThe objective of this project is to conduct a technology review to identify best practices on strategic vegetation management planning of transmission ROWs. The study would review how utilities survey/audit, plan (growth estimates, brushing cycles, budgets, etc.) and justify ROW brushing and other vegetation control methods from a strategic perspective to manage risk and cost.
• Guidelines for Specifying Polymer Insulators for Applications in Harsh Service EnvironmentsPolymer insulator specifications are minimal specifications, and insulators meeting these requirements have generally performed well in pristine service environments. However, insulators meeting these specifications have often failed to perform in harsh service environments. The objective of this project is to clarify and document the reasons for both the good and poor performance that has been experienced, and then utilize this information, coupled with a good understanding of polymer insulator ageing mechanisms under various harsh operating conditions, to develop a specification for the application of polymer insulators in various harsh environments, where insulators are installed in areas subject to contamination from sources such as such as seacoast, mining, salted expressways, petrochemical or heavy industries, etc.
• ACSR Conductor Splice Inspection MethodologiesThis Technology Review examines in detail, existing conductor splice inspection methodologies. A comprehensive literature review, interviews with manufacturers of the diagnostic tools, and a survey of utility maintenance managers will be used to gain a more thorough understanding of these inspection technologies and the importance of the required parameters. The advantages and disadvantages of each technology will be documented, and their relative cost effectiveness will be identified. The primary objective of this Technology Review is to provide utilities with a clearer understanding of the cost effectiveness of these inspection technologies. The literature review, diagnostic tool manufacturer interviews, and utility user survey are expected to reveal the effectiveness, relative costs, the requirements for use and the relative advantages or disadvantages of each methodology.
• Technology Review on the Condition Assessment of Below Grade Steel Structures and Life Extension MethodologiesThis technology review will investigate the various methods for assessing the condition of below grade steel structures used for transmission lines, primarily the galvanized grillage type but galvanized members of lattice towers or pole type structures that are encased in concrete as well. The project is primarily intended to address how to assess the condition of the coatings (galvanizing, paint, etc.), layer and parent steel, and how to extend the life by the application of barrier coatings, or installation of sacrificial anodes, member reinforcement or encasement in concrete.
• Proximity of Pipelines to Transmission Structures and Grounding: An Overview of Problems, Analysis Tools and Mitigation MeasuresPipeline installation (natural gas, petroleum, water, sewage, etc.) on transmission line Right-of-Ways (ROWs), although commonly accepted, is of concern to both pipeline and utility owners. Steel structures are placed within close proximities to pipelines and this causes utilities to be concerned about the potential corrosion of transmission tower footings and grounding conductors due to stray earth currents from the pipelines cathodic protection schemes. Pipeline owners are concerned about the earth’s component of fault currents and voltage induction damaging the cathodic protection supplies and punctures to pipeline coatings, flashover damage to isolation flanges and possible hazardous step and touch potentials to workers on pipelines.
  
  It is proposed to conduct a literature survey, review of experience with pipeline (including various pipeline types) and transmission companies for concerns and experiences of having pipelines on transmission line corridors. A utility and manufacturer survey will also be conducted as well to see which tools are presently used and which tools are available for utilities to study such a problem. The project will also examine bonding of steel structures and pipelines. The purpose of the proposed project is to examine the concerns of transmission line ROW users and to identify mitigation measures.
• Methods for Improving Ground Resistance of Transmission Structures, Phase IIThe first phase of this work was funded by the TLAM TR Program and those results are available to all TLAM group participants. It is recommended to continue this investigation with a thorough high-frequency analysis. The first objective of the second phase is to make a direct comparison of two different methods for modeling the response of ground electrodes -- CDEGS, an industry-standard analysis package, and NEC-4, modeling the high frequency response of antennas with elements buried in lossy soil. These software programs will be used to model typical transmission line towers such as: steel pole, four foot lattice tower, and H-Frame structure. The use of both the CDEGS and NEC-4 software will increase the confidence in the numerical results obtained, and will help evaluate the errors introduced by the low frequency approach used by CDEGS packages such as AutoGround and MultiGround. The numerical results will be also compared with measurement data available in the public domain. The second objective is to evaluate the performance of CDEGS MultiFields package, dedicated to transient grounding, electromagnetic interference and electromagnetic field computations. The cases described above will be modeled with this package and the results will be compared with NEC-4 solutions and the CDEGS low frequency approach.
• Above Ground Structure Corrosion On Transmission Lines - A Practical ApproachThis project is intended to review and describe the various methods of assessing the degree of corrosion on above ground steel structures used for transmission lines, such as lattice type galvanized steel, shaped steel poles either galvanized, self-protecting coating and paint coatings. The methods to be described and quantified should be simple yet reliable enough to describe when a structure should be recoated in order to avoid structural deficiencies.

Recently Completed Projects