LTC Condition Assessment by Diagnostic Testing
Authors作者: Fredi Jakob, Karl Jakob, Simon Jones - May 29, 2003
During the past forty years, dissolved gas analysis DGA, has become universally accepted as the premier diagnostic tool for location of incipient faults in transformers. Extension of DGA to other oil filled equipment were proposed and debated during the past decade. The consensus opinion was that gases developed during the switching operation would “cover up” any gases due to equipment problems. Table 1 shows the gas producing processes that occur in oil filled electrical apparatus. The gases that are produced by these various processes are listed in Table II. Recognition of these differences between normal and abnormal gassing conditions paved the way to diagnostic evaluation of load tap changers LTC’s, and oil filled circuit breakers, OCB’s.
Use of Gas Concentrations Ratios to Interpret LTC Dissolved Gas Data
Authors: Fredi Jakob, Karl Jakob, Simon Jones Weidmann-ACTI Rick Youngblood Cinergy Corporation — May 29, 2003
Fifteen years ago a common belief was that dissolved gas analysis, DGA, was not applicable to oil circuit breakers, OCB’s or load tap changers, LTC’s. This assumption was based on the idea that the gases produced during normal operation of an OCB or LTC would be more significant than gases produced by a fault process such as contact overheating.
Dissolved Gas Analysis - Past, Present and Future
Authors: Fredi Jakob Weidmann-ACTI Inc. — Jan 21, 2003
It has been well over thirty years since dissolved gas analysis, DGA, was introduced as a diagnostic tool for monitoring mineral oil filled transformers. It is now universally accepted as the method of choice to locate incipient thermal and electrical faults. DGA methodology and applicability have evolved significantly since its inception. The evolutionary development includes new laboratory methods, on-line DGA, application to additional types of fluid filled equipment, application to dielectric fluids other than mineral oil and new diagnostic interpretation protocols.
Condition Appraisal of Power Transformers
Authors: David J. Woodcock Weidmann Systems International Inc — Jul 17, 2002
The new deregulated electric utility environment is driving Transmission and Distribution companies to find ways to improve their competitive position. Maximizing return on investment (ROI) is often a key financial driver when formulating a profitable T & D operation and maintenance strategy. Increased equipment utilization, deferred capital expenditure and reduced maintenance expense are all a part of the guidelines for today's T & D asset strategists and managers. Although tighter operating budgets and reduced spending are nothing new to utility engineers and planners, today's increased need to leverage more out of existing equipment must be achieved with the majority of T&D assets nearing the end of their life cycle.
The Key to Condition-Based Asset Strategies for Power Transformers
Authors: David J. Woodcock, Weidmann Systems International — Nov 1, 2004
Investment in the development of electric generation, transmission and distribution was booming throughout the mid-1960s to early 1980s. The installation of power transformers followed this trend. This peak development period was followed by a sharp decline in capital spending which, on average, has continued for the past 20 years. At the same time, demand for electrical energy, or load growth, has slowly but steadily increased. This has resulted in the typical power transformer on the U.S. domestic grid being highly loaded with an average age of 35 years. Electrical equipment of this age is generally considered to be approaching the end of its useful life. Electric utility companies, driven by their customers' needs, have a low tolerance for failures and hence risk-cost has become a very real cost of doing business.
Power Transformer Design Enhancements Made to Increase Operational Life
Authors: David J. Woodcock, Jeffrey C. Wright, P.E., Weidmann Technical Services Inc. — Sep 12, 2003
New rules in the deregulated electric utility business require Transmission and Distribution companies to find ways to improve their competitive position. Maximizing return on investment (ROI) is often a key financial driver when formulating a profitable operating T & D strategy.
Application of Dissolved Gas Analysis to Load Tap Changers
Authors: Rick Youngblood, Cinergy Corporation; Charles Baker, South Carolina Electric and Gas; Fredi Jakob and Nick Perjanik, Analytical ChemTech International, Inc. — Sep 23, 2002
Thermal and electrical faults dissipate energy. If dielectric fluid or solid insulation is in the vicinity of a fault, energy transfer will occur and this will result in non-reversible partial molecular degradation of insulating materials. The existence of irreversibly generated decomposition products is the basis for dissolved gas analysis (DGA). These processes are not limited to transformers and can occur in any oil filled electrical equipment. The application of DGA to transformers has been universally accepted as a valuable diagnostic tool. When consideration is taken of the operating parameters of Load Tap Changers and Oil Circuit Breakers, there is no reason why the DGA methodology cannot be applied in a cost-effective preventive maintenance program.
The Move Toward Dynamic Loading of Power Transformers
Authors: David J. Woodcock, Weidmann Systems International Inc. — Sep 12, 2003
The new deregulated electric utility environment is driving Transmission and Distribution companies to find ways to improve their competitive position. Maximizing return on investment (ROI) is often a key financial driver when formulating a profitable T & D operation and maintenance strategy. This strategy requires that utility operations and maintenance find ways to leverage the most out of existing transformers.
Life-Cycle Considerations of Loading Transformers Above Nameplate Rating
Authors: Michael A. Franchek and David J. Woodcock, Weidmann Technical Services Inc. — Sep 12, 2003
In today's world of deregulated electric utilities, the concepts of transformer life extension, increased loading, and reduced maintenance are often discussed. These ideas at first appear to be contradictory in nature, but all strive for the same results; reduced operating costs and improved reliability in the delivery of electricity. In fact, for substation transformers, all of these goals can be obtained with the implementation of a strategic "Life Cycle Management Program". This paper addresses the primary concepts of life extension and increased loading of transformers, and how these issues are interrelated.
A Solution for Maintenance of Power Transformer Operating Under Frequent Overloads
Authors: Jean-Claude Duart, DuPont de Nemours International, and David J. Woodcock, Weidmann Systems International Inc. — Sep 12, 2003
Changes in the way utilities manage their transmission and distribution assets, as well as increases in peak load demand, has led to the need to subject more and more substation transformers to overload conditions. This paper will present the concept of utilizing a high temperature insulation system, also called a hybrid insulation system, as a way for enhancing the performance and load capability during the transformer repair process.
Authors: Fredi Jakob, Karl Jakob & Simon Jones, Weidmann-ACTI; Rick Youngblood, Cinergy; Alex Salinas, Southern California Edison - Sep 23, 2002
During the B.D. era, before deregulation, run to failure, time based and operation count based maintenance methods were widely employed. These methods were effective in maintaining the power delivery system but were labor intensive and not cost effective. Time based and operation count based maintenance methods could not identify units that developed problems between scheduled inspections. Units were often inspected on a time basis and no problems were identified. After deregulation, A.D., fiscal requirements led to decreases in trained maintenance personnel, deferral of capital expenditures, equipment life extension programs, and efforts to maximize uptime and minimize maintenance costs. Reliability centered and condition based maintenance are key A.D. concepts that have been implemented in the power industry. The ultimate goal of condition based maintenance would be to perform maintenance “just in time”, before the equipment fails in service. Condition based maintenance requires periodic or continuous (on-line) equipment monitoring. Equipment is scheduled for inspection and/or maintenance only when diagnostic test results indicate a potential problem.
OIL: The Four Rs - Retain, Recondition, Reclaim, Replace
Authors: Fredi Jakob, Weidmann-ACTI — Sep 23, 2002
Fluids, liquids or gases, that are used in electrical equipment serve three essential purposes. These fluids must provide adequate insulation, efficiently transfer heat from the source to the atmosphere and quench arcs that may develop in the equipment. To meet these requirements the selected fluid must consist of non-polar molecules that are chemically stable.
Sulfur Hexafluoride: A Unique Dielectric
Authors: Fredi Jakob Ph.D. and Nicholas Perjanik M.B.A., Analytical ChemTech International, Inc. — Sep 23, 2002
Fluids, either gases or liquids, that are used as dielectrics in electrical equipment must possess certain basic properties. The selected fluid must provide thermal conductivity in order to dissipate heat generated within the equipment. It must have excellent insulating properties and must be able to quench arcs.
Silicone Dielectric Fluids
Authors: Fredi Jakob, Karl Jakob, Nicholas Perjanik, Analytical ChemTech International, Inc. — Sep 23, 2002
Mineral oil based dielectric fluids have been used more extensively than other dielectric fluids in electrical equipment because of their wide availability, low cost and excellent physical and electrical properties. Their only shortcoming is their relatively low flash and fire points.
The Effects on Winding Clamping Pressure Due to Changes in Moisture, Temperature and Insulation Age
Authors: Tom Prevost, EHV-Weidmann, USA; David J. Woodcock, Weidmann Technical Services Inc., USA; Christoph Krause, H. Weidmann Ltd., Switzerland — Mar 21, 2000
Power transformer windings are designed to withstand high axial forces which result from short circuit events. To withstand these forces, the winding assembly is clamped to a predetermined pre-load pressure during manufacture. This paper discusses the important relationship between changes in moisture level versus clamping pressure for new transformers. It further relates laboratory investigations of changes in clamping pre-load versus changes in operating temperature, moisture and the insulation aging effect.
A Nomograph for Interpretation of LTC-DGA Data LTC
Authors: Fredi Jakob, Karl Jakob, Simon Jones, Weidmann-ACTI; Rick Youngblood, Cinergy - Jan 27, 2004
Dissolved Gas Analysis, DGA, is based on the fact that the release of energy in oil filled electrical equipment results in a partial destruction of insulating fluids and/or solid insulation. The number of molecules destroyed is relatively small but detectable amounts of low molecular weight gases are produced. The quantification of the low molecular weight “fault gases” is the basis of all DGA.