14-11-2012, 01:11 PM
CONDITION MONITORING OF TRANSFORMERS
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ABSTRACT
Transformers are a large part of the component structure of the electricity system. Knowing the condition is essential to meeting the goals of maximizing return on investment and lowering total cost associated with transformer operation. In order to reconcile both decreasing maintenance spending and reliable service, condition based maintenance (CBM) is often proposed. The successful application of CBM lies in obtaining information transformers, so that, on the one hand, a critical condition will be noted early enough to take measures and on the other hand, so that only minimal maintenance is being applied to transformers still in good condition. The paper covers the following areas.
General aspects of aging in transformers.
An overview of condition monitoring methodology with partial discharge patterns in focus.
Partial discharge measurement and diagnostics on power transformer using a multi channel digital PD detector.
INTRODUCTION
The need for improved performance from expensive industrial plant has in recent years necessitated the application of condition-Monitoring methodologies. These can provide early warning of potential failure with the opportunity of organizing avoidance strategies to minimize lost time and unexpected costs, thus greatly improving manufacturing efficiency. The same is the case with power industry. Here maintenance expense as well as increased liability for non-delivered energy increases the costs of sudden failure of a component. E.g. Transformers. The continuing drive for improved efficiency demands that a more educated analysis of monitored signals provides an indication of or even diagnoses the cause of a fault. The level of urgency of a condition can then be determined, thus enabling the necessary action to be taken over an appropriate fine scale. Maintenance can be scheduled based in plant condition rather than on a time based regime. This need for condition based maintenance has encouraged the development of adaptable and cost effective diagnostics for HV transformers in addition to regular measurements like gas in oil analysis, several measuring tools have been introduced. To simplify the task of PD testing, the digital PD detector LDS-6 was adopted to automate there measurements and perform sensitive measurements under electrically noisy conditions.
Condition Monitoring of Transformer Condition based maintenance (CBM) for
Cost reduction
Life time extension
Increased reliability
GENERAL ASPECTS OF AGING
The insulation system of a transformer consists mostly of oil and paper which are subject to aging. Aging is defined as the irreversible changes of the properties of electrical insulation systems (EIS) due to action of one or more factors of influence. The aging factors produce electrical, thermal mechanical or environmental aging mechanism that eventually leads to failure. When aging is dominated by one aging factor this is referred to as single factor aging. In multifactor aging more than one factor substantially affects the performance of the EIS. Aging factor may act synergistically, that is, there may be direct interactions between the stresses. Interactions may be positive or negative. The aging of a practical EIS can be complex and failure is usually caused by a combination of aging mechanisms, even though there may be only one dominant aging factor. The following aging factors are important
1. Thermal Aging: Thermal Aging involves the process of chemical and physical changes as a consequence of chemical degradation reactions, polymerization depolymerisation diffusions etc. It also involves the thermo mechanical effects caused by the forces due to thermal expansion or contraction. The rate of thermal aging is very much influenced by the operating temperature.
2. Electrical Aging: Electrical Aging either AC, DC or impulse involve the following.
The effects of partial discharges
The effects of tracking
The effects of treeing
The effects of electrolysis
The effects of increased temperature produced by high dielectric losses.
Electrical Aging is influenced by field strength.
[attachment=39370]
ABSTRACT
Transformers are a large part of the component structure of the electricity system. Knowing the condition is essential to meeting the goals of maximizing return on investment and lowering total cost associated with transformer operation. In order to reconcile both decreasing maintenance spending and reliable service, condition based maintenance (CBM) is often proposed. The successful application of CBM lies in obtaining information transformers, so that, on the one hand, a critical condition will be noted early enough to take measures and on the other hand, so that only minimal maintenance is being applied to transformers still in good condition. The paper covers the following areas.
General aspects of aging in transformers.
An overview of condition monitoring methodology with partial discharge patterns in focus.
Partial discharge measurement and diagnostics on power transformer using a multi channel digital PD detector.
INTRODUCTION
The need for improved performance from expensive industrial plant has in recent years necessitated the application of condition-Monitoring methodologies. These can provide early warning of potential failure with the opportunity of organizing avoidance strategies to minimize lost time and unexpected costs, thus greatly improving manufacturing efficiency. The same is the case with power industry. Here maintenance expense as well as increased liability for non-delivered energy increases the costs of sudden failure of a component. E.g. Transformers. The continuing drive for improved efficiency demands that a more educated analysis of monitored signals provides an indication of or even diagnoses the cause of a fault. The level of urgency of a condition can then be determined, thus enabling the necessary action to be taken over an appropriate fine scale. Maintenance can be scheduled based in plant condition rather than on a time based regime. This need for condition based maintenance has encouraged the development of adaptable and cost effective diagnostics for HV transformers in addition to regular measurements like gas in oil analysis, several measuring tools have been introduced. To simplify the task of PD testing, the digital PD detector LDS-6 was adopted to automate there measurements and perform sensitive measurements under electrically noisy conditions.
Condition Monitoring of Transformer Condition based maintenance (CBM) for
Cost reduction
Life time extension
Increased reliability
GENERAL ASPECTS OF AGING
The insulation system of a transformer consists mostly of oil and paper which are subject to aging. Aging is defined as the irreversible changes of the properties of electrical insulation systems (EIS) due to action of one or more factors of influence. The aging factors produce electrical, thermal mechanical or environmental aging mechanism that eventually leads to failure. When aging is dominated by one aging factor this is referred to as single factor aging. In multifactor aging more than one factor substantially affects the performance of the EIS. Aging factor may act synergistically, that is, there may be direct interactions between the stresses. Interactions may be positive or negative. The aging of a practical EIS can be complex and failure is usually caused by a combination of aging mechanisms, even though there may be only one dominant aging factor. The following aging factors are important
1. Thermal Aging: Thermal Aging involves the process of chemical and physical changes as a consequence of chemical degradation reactions, polymerization depolymerisation diffusions etc. It also involves the thermo mechanical effects caused by the forces due to thermal expansion or contraction. The rate of thermal aging is very much influenced by the operating temperature.
2. Electrical Aging: Electrical Aging either AC, DC or impulse involve the following.
The effects of partial discharges
The effects of tracking
The effects of treeing
The effects of electrolysis
The effects of increased temperature produced by high dielectric losses.
Electrical Aging is influenced by field strength.