Summary of research and developments
Introduction
The widespread use of ac system became possible only after the transformer invention. Thanks to its presence an opportunity to produce electricity at a voltage that is convenient for its generation, transfer it to the voltage corresponding to the minimum losses, and to consume at a voltage, calculated on the parameters of electro. Transformer not only changes the voltage to levels suitable for all levels of the circuit, but also connects them into a unified energy system. Therefore no exaggeration to say that the power transformers are very important and integral part of any power system and their importance is difficult to overestimate.
Topicality
Proper maintenance and timely repairs can significantly extend the service time of industrial equipment. As well as reducing the costs of its keep (for example, by reducing the cost of consequence the effects of unplanned stopping), raise the general reliability of the company work, etc.
For large enterprises, especially using complex and expensive equipment, questions of maintenance service and repairs play a crucial role. The costs of such companies on maintenance service and repairs can be more than half the total cost of production.
Therefore, all the more pressing becomes the problem of improving maintenance service and repairs system. And so the problem of introduction the new systems for the effective maintenance of in-service equipment, which includes a complex of works aimed at the rapid evaluation of the technical condition and maintain it in good condition with the use of modern diagnostic means.
Work aim
Work aim is the research and analysis of modern technical diagnostic methods for power transformers of electric networks and estimation of their using possibility during the transition to service system «on a condition».
Scientific novelty and practical value
Using of complex diagnostic test of power transformers allows objectively evaluate the current technical condition all transformer systems, to minimize the costs linked with a transformer fault, due to timely defect detection arising during operation. It also allows carry out transition from system of scheduled preventive maintenance to service system «on a condition».
Researches results
• Analysis of power transformers damage.
• Analysis of existing technical diagnostics methods of power transformers in electrical networks.
• Mathematical modeling of power transformers planning repairs in electrical networks and revelation possible ways to increase maintenance intervals.
• Development of transition algorithm from scheduled preventive maintenance system to service system «on a condition» for power transformers of electric networks.
Work approbation
• Ukrainian scientific-technical conference "Electromechanical systems, modeling and optimization.
• Ukrainian scientific-technical conference of students "Electrical, electronics and microprocessor technology.
Review of existing methods and working
At present there is a set of various methods of diagnosing and the control of a technical condition of transformers. All measurements and analyses may be divided into 5 groups.
The first group includes traditional measurements on the switched off transformer: measurements of tgφ and R winding insulation and lead-ins, winding dc resistance, no0load losses and resistance to short-circuit to control the mechanical condition of the windings after the occurrence of loop short-circuit currents.
The second group of measurements carried out on transformers with an operating voltage in the biggest loads mode and (or) in no-load condition. Here it can be to highlight the following work:
1. Partial and other electrical discharge measurements.
2. Acoustic survey of the transformer tank.
3. Vibration transformer survey.
4. Determination of oil pumps the cooling system condition.
5. Thermographic survey of the transformer tank, lead-ins of expander heat exchangers (radiators), thermosiphon filters, electric motors and oil pumps of the cooling system, contact connections.
The principle of heat visor test of power transformers is the projection on thermal defect in the active part on the tank surface which is not closed by an equipment on hinges, and identify this site in the analysis of thermograms (Figure. 1).
Figure 1 – Heat projection of the defect in the active part of the transformer on the tank surface:
1 – tank, 2 – winding, 3 – core, 4 – defect, 5 – heating projection on the tank surface
The third group is a physical-chemical analysis of oil from the tank, oil-filled lead-ins, contactor of on-load tap changing device. There is a large group of traditional measurements among them, widely used in the operation (measurement of breakdown voltage, acid number, etc.).
The fourth group is a measurement system for continuous monitoring (monitoring) of lead-in insulation and daily measurements of main indices of the transformer working.
The fifth group of tests carried out for transformers, which at result of the first four groups of measurements are planned overhaul. This group includes the definition of the degree of paper insulation polymerization, direct measurement of its moisture content and strength.
Conclusion
Executed analysis showed that the modern development of technical diagnostics methods of power transformers in electrical networks allows reliably detect the defects in equipment components at an early stage of their development. This in one’s turn allows to refuse from system of scheduled preventive maintenance and to pass to service system of power transformers «on a condition».
References
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http://transform.ru/articles/html/07repair/rep00018.article
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Note
When writing this abstract the master’s work was not completed. Final completion: December 2010. Complete text of the work and material on the topic may be obtained from the author or his manager after that date.
