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Meeting the Challenges of Managing Substation Equipment Assets

by By Mr. Jack Shaver, P. Eng. CEA Technologies Inc.

As regulated monopolies evolve into competitive industries, utilities have had to change the way they conduct business. A central component of the marketplace is the need to provide the consumer with an available and reliable product at the lowest cost, placing great pressure on utilities to reduce variable expenses. The burden is thus to reduce the capital cost of equipment and its associated operating and maintenance costs.

Problematic is the fact that much of the equipment (breakers, transformers, switches) owned by utilities was installed a great number of years ago and may be reaching the end of its service life.Because of the risk of failures, this older equipment requires higher frequency maintenance and scheduled outages, which reduce system availability and reliability, decreasing the value of the delivered product.Although simply replacing the equipment may solve these problems, the carrying costs associated with such actions would, in turn, increase the cost to the consumer.

Asset management is without a doubt one of the most difficult occupations in the utility industry.In order to remain competitive, work must be performed at minimum cost and with little interruption to service, all without neglecting safety and environmental concerns.

This dilemma creates serious problems for those charged with the responsibility of maintaining utility assets especially as the list of factors they must consider grows longer.The focus is thus one of determining the best practices for the monitoring and assessment of station equipment.

The current state of the industry has challenged the time-honoured system of scheduled, or time-based, maintenance.This is the most expensive form of maintenance and it may not identify potential failures.Scheduled maintenance may identify the condition of the equipment at the time of assessment, but the estimation of remaining life is not necessarily addressed by current tests or practices.It is clear that the maintenance process must evolve with the industry.

MAINTENANCE INTERVALS

In the past, utilities generally followed the maintenance recommendations of manufacturers. These recommendations were justifiably conservative as, without detailed knowledge of the operating conditions, manufacturers must base their maintain/repair/replace guidelines on the most severe operating conditions and duty cycles.Transformers, for example, are typically expected to last well in excess of 20 years, with testing or maintenance planned at regular (annual or otherwise) intervals.Research, however, indicates that maintenance intervals can be extended beyond manufacturer guidelines based on the operating conditions of the equipment – many transformers currently in service are approaching 30 – 40 years of age.While improvements have been made in determining optimum maintenance intervals, further research will be needed to produce ideal timelines for varying conditions, minimizing both costs and associated outage requirements.

FAILURES

Maintenance tasks must identify two central factors: the condition of the existing equipment and potential equipment failures.Any abnormal conditions should be addressed before any equipment is returned to service as on-line failures constitute the most expensive maintenance task.These events also increase the risk to other equipment in the system and must be prevented.In the event that equipment is to be placed into service without corrective action, it must be done with full knowledge of when a failure may be expected, with remedial action scheduled before that time.

ASSESSMENT

An important factor to be addressed is how the condition of the equipment can be assessed without removing it from service.Oil/gas sampling has been the accepted on-line method to date, but other technologies are quickly emerging and/or being applied in non-traditional manners.New techniques, including the monitoring of parameters such as vibration and acoustics, temperature, discharge, and motion, offer utilities alternatives to the status quo.It is hoped that additional research in the development of new technologies may help to establish safe operating limits for the parameters being monitored and improve on utilities’ capabilities to interpret and analyze the data in real-time.

TOOLS

It is essential that utilities know when equipment should be replaced or repaired.As many factors influence this decision, it is useful that the asset manager have access to both qualitative and quantitative tools.Developing decision-making tools that take into account obsolescence, reliability, safety and environmental issues, in addition to operating, repair and carrying costs, is necessary for consistent and intelligent decision-making.

REMAINING LIFE

One of the most pertinent topics in asset management is the estimation of remaining life.Based on a piece of equipment’s at-present operating conditions, asset managers are tasked with determining how much of its expected life has expired and, considering future operating conditions, how much life is left.In order to do so, new technologies and methodologies for analysis and forecasting must be developed.Through forecasting and budgeting for replacement, surprises in capital cost expenditures can be avoided.While the hope is that maintenance planners will be able to schedule maintenance, repair, or replacement to coincide with the increased probability of failure based on the remaining life, more research and data collection will be needed before this can be considered an effortless assignment.

EXTENDING THE USEFUL LIFE

While the estimation of remaining life helps to predict failures, it can also be useful in helping to extend the life cycle of equipment.New developments in the use of inhibitors and in the maintenance of the original quality of the insulating medium will extend the life expectancy of both new and used equipment.Under older methods, these were allowed to deteriorate to a certain point before remedial action was to be taken.Keeping these mediums at peak operating condition will extend the equipment’s life and reduce costs, especially if the process can be done while the equipment is on-line.Real-time detection and analysis of decomposition by-products will provide clues in the assessment of the current condition and the remaining life.The development of more real-time on-line analysis and diagnostic techniques will lead to courses of remedial action that will be of great benefit to the industry.

BEST PRACTICES

It is often quite difficult to determine the best operation and maintenance practices and methods.The management of assets can vary greatly between utilities, often under similar operating conditions.Opportunities do exist, however, to research, develop and document these "best practices."Such research will assist utilities in the development of their individual processes and methods.By identifying areas of risk (too little maintenance) and areas of overindulgence (too much maintenance), utilities can optimize their operations.

COLLABORATIVE EFFORTS

It is important to recognize that research related to asset management cannot be undertaken by one single utility; the cost of individual efforts is simply prohibitive.Through collaboration and by bringing together their resources (ideas, funding, personnel, skills, etc.) utilities can meet their objectives.

The Life Cycle Management of Substation Equipment and Apparatus (LCMSEA) Interest Group of CEA Technologies Inc. (CEATI) helps utilities facilitate their research and technology development endeavours.This group of 24 utilities provides a forum for the sharing of information and the development of new projects.

The group is currently focused on the development of equipment diagnostics (on- and off-line) and life optimization through the development of validation tools for predicting the remaining life and/or extending life.Safety and environmental concerns are a consideration in all endeavors of the group.

Many projects have been completed through the collaborative efforts of the Interest Group.Recently completed projects include:

Prediction of the Remaining Life (Life Left) as a First Indicator of Transformer Problems

The current trend in the utility industry is to utilize power transformers beyond their operating limit and/or normal operating life.The objective of this project was to find a simple test (through the monitoring of properties of oil) that might indicate the extent of deterioration and the remaining life of the transformer oil. Two methods were tested - Free Radical Scavenging Activity (FRSA) and the Rotary Bomb Oxidation Test (RBOT; ASTM D2112).A combination of the two tests was applied to estimate the remaining life of transformer oils.Further tests with field samples established a correlation between oil stability as measured by combining RBOT and the Free Radical Scavenging Activity.

Safety Protocol for Restoration of Substations Involved with Fires/Explosions

A natural consequence of maximizing the life of existing electrical utility substation assets is the further aging of electrical equipment.As equipment (and more specifically a transformer) ages, it is more prone to failure, which can occasionally result in fires and/or explosions.As materials typically found in electrical substations may form toxic by-products due to combustion, this report investigates the potential impact of their hazardous by-products.Included case studies illustrate the impact that these incidents have had on workers providing secondary response and cleanup, providing valuable lessons for future response.A safety protocol is presented for the sampling and clean-up of the atmosphere, equipment and debris following a fire or explosion in a substation. This safety protocol may be used by utilities to develop their own response plans and procedures.

Prediction of the Remaining Life (Life Left) of Power Connectors and Disconnect Switches

The primary aim of this work is to conduct a thorough engineering and failure mode analysis of power connectors and disconnect switches to identify maintenance issues and high frequency/high cost faults and failures.The work identifies sensors required to diagnose or predict the faults, including cost-benefit analysis.An essential part of the project involves the development of a prognostic algorithm for predicting the remaining life of a power connection.Included in the work is a survey of utilities which aims to collect field data on the failure sites, modes and mechanisms of power connectors and disconnect switches.

Instrument Transformer Condition Assessment and Diagnostics

Failures or faults on instrument transformers (ITs) may lead to the malfunction of system protection, controls or metering devices, and thereby jeopardize reliability and safety.There are many techniques for the condition assessment of oil-paper insulated equipment in general, and ITs in particular.However, no single technique seems to work all the time.In response, the LCMSEA Interest Group has sponsored a report which consists of a literature review and a worldwide survey of utilities to identify "best practices."Commercially available diagnostic instruments from different manufacturers were assessed based on their technology and operating experience. From this study, guidelines were developed for the implementation of the most appropriate and cost-effective condition monitoring methodologies.

JOINING TOGETHER TO FUND SUBSTATION RESEARCH

The Life Cycle Management of Substation Equipment and Apparatus (LCMSEA) Interest Group is one of the many "interest groups" of CEA Technologies Inc. (CEATI).LCMSEA participants jointly sponsor studies and research projects in the area of substation equipment that will benefit them, the electrical utility industry and customers at large. Participation is open to all electrical utilities that have an interest in substation-related issues. The group identifies areas of common concern and defines research objectives to solve those concerns.Individual group participants can then select to co-fund projects of interest that will be of benefit to their organizations.This flexible and collaborative approach provides substantial cost-benefit advantages to the participants.

About the Author
Mr. Jack Shaver, P. Eng. leads the Life Cycle Management of Substation Equipment and Apparatus (LCMSEA) Interest Group. Mr. Shaver has over 30 years of engineering experience with Manitoba Hydro in positions ranging from distribution design to apparatus maintenance.In his latest position as Senior Apparatus Maintenance Engineer, he was responsible for developing maintenance standards for substation equipment based on Reliability Centered Maintenance (RCM) in Transmission and Distribution Substations.A graduate of University of Manitoba, Mr. Shaver has also taken advanced courses in Project Management, Business Planning, Progress Improvement and the Fundamentals of Thermography. Over the years he has focused on many areas, including the planning of diesel generation facilities to meet load requirements in remote communities in Manitoba and the design of distribution substations, subtransmission and distribution lines and their protection systems.Jack served as a member and Chair of the Manitoba Hydro Professional Engineers Association Safety Committee and was also Manitoba Hydro’s representative in LCMSEA from 1996 until his retirement in 2003.



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