Intelligent system for diagnostics of power transformer equipment

Introduction

Moisture management today is one of the most important problems in the maintenance of high-voltage oil-insulated power transformers [4-6]. Let's take a look at moisture management for transformers with oil tanks using the example of a high-end equipment line with humidity and temperature monitors. Power transformers are one of the most important objects for transmission and distribution of energy, and the most expensive equipment of the entire electrical system. As a rule, they are very reliable and rather undemanding to maintain, because they do not contain parts that are in continuous motion. However, insulating materials degrade over time and it is ultimately difficult to determine the remaining life of a transformer. Figure 1 shows an analysis of the location of the failure for transformer substations with voltages of 100 kV and above, respectively [1-3]. Excess moisture builds up in the transformer insulation, which is capable of holding more than 95% water, resulting in increased conductivity and accelerated aging. When high levels of humidity are reached, a sharp drop in temperature is possible, hence there is a large loss of free water and the risk of an internal short circuit increases.

Preliminaries

Molecular sieve in line for drying transformers. The unit is a molecular sieve made of zeolite in line, which provides continuous removal of water from the oil, and also makes it possible to extract water from the paper insulation of the transformer. This method not only reduces the aging rate of the equipment, but also increases the dielectric strength of the insulation and increases reliability, especially by neutralizing external influences and possible defects, while maintaining the insulation power.

Fig. 1 Locations of failures of substation transformers

The use of zeolite as a "drier" in the molecular sieve concept has been well known since the 1960s. However, more recently, with the advent of synthetic elements, it has become possible to sufficiently accurately control the pore size during the manufacturing process to improve the absorption process. Modem molecular sieves do not provide prematurely outdated dissolved gas analyzes.

The devices also accept sampling points that allow the operator to extract an oil sample for further analysis in the laboratory.

Statement of the problem

When the inlet and outlet concentration levels approach one, the system or electrical plant operator knows that the molecular sieve material is saturated and needs to be replaced. TRANSEC units can be used to monitor the humidity and temperature of inlet and outlet oil pipes. The reliability and stability of the measurements made by the MMT162 is not only applied to monitoring the moisture in oil, but also to measuring the operating parameters of the moisture management system. Moisture monitoring. When the inlet and outlet concentration levels approach one, the system or electrical plant operator knows that the molecular sieve material is saturated and needs to be replaced. TRANSEC units can be used to monitor the humidity and temperature of inlet and outlet oil pipes. The reliability and stability of the measurements made by the MMT162 is not only applied to monitoring the moisture in oil, but also to measuring the operating parameters of the moisture management system.

Solution method

power transformer equipment insulation

System for continuous monitoring and dehumidification of the insulation of oil-filled transformers. Continuous draining of the insulation of an oil-filled transformer during operation: does not require disconnecting the transformer during installation and operation; for transformers with a capacity of 1 MVA and above; reduces the risk of accidents and extends the life of transformers; humidity level control; independent installation, only need power supply.

Exposure to moisture and oxygen causes degradation of the insulating paper. One of the products of such a chemical reaction is H₂O. Transformer oil picks up only a small amount of moisture, while more than 95% remains in the solid insulation. An increase in the percentage of moisture accelerates the aging of the transformer and can cause an interturn circuit, partial and creeping discharges, and a change in the temperature of the transformer oil increases the risk of transformer failure [7]. After the transformer oil is dried by the TRANSEC system, the oil absorbs the moisture from the insulating paper and re-enters the dryer system. Thanks to this cyclical effect, the TRANSEC system keeps the solid insulation permanently dry, which ensures reliable and safe operation and significantly extends the life of the transformer. In comparison with other methods, this method allows drying not only oil, but also paper insulation, while the transformer is running, without resorting to transporting or shutting it down. TRANSEC's operating principles make it the most cost-effective solution for dehumidifying oil-filled transformer insulation among alternative methods. In addition, unlike other methods, TRANSEC allows you to constantly (rather than from time to time) keep the solid insulation in a dry state, which significantly reduces the rate of degradation of the insulating paper and the risks associated with it. TRANSEC modules are a reliable and safe way to dry the solid insulation of live oil-filled power transformers. Power transformers and autotransformers are important elements of electrical networks and power systems, ensuring the reliability and efficiency of their operation. Most power transformers are used with a longer service life than specified in GOST 11677-85. Often they are forced to work 1.5-2 times more.

The service life of transformers directly depends on their maintenance, which should be aimed at restoring the operational properties of units and elements. The weakest link in a transformer is the cellulose insulation of the windings. Moisture greatly accelerates the thermal aging of cellulose, the consequences have a bad effect on the dielectric characteristics, chemical resistance to decomposition and mechanical strength of solid insulation. Cellulose also suffers from oxygen, oil oxidation products, and temperature. By protecting the transformer from these factors, it is possible to greatly increase the life of the solid insulation and extend the life of the device itself. Maintaining transformers: 2 ways. Maintaining the operational characteristics of the insulation and monitoring its moisture content during operation is possible in two ways. The first is the direct drying of the cellulose insulation of the windings on a disconnected transformer, which, in fact, is a major overhaul. And also potentially dangerous, as it can lead to a decrease in reliability, resource and even failures, and as a result - to significant material losses. The second way is to dry the transformer insulation without disconnecting from the network. JSC NPO Streamer offers a technologically advanced and efficient method for drying the solid insulation of operating transformers by continuously drying oil in TRANSEC modules.

Use is carried out without the participation of service personnel. A circulation pump is built into the transformer circuit, pumping oil at a rate of 60 l / h through 1 or 3 filters filled with zeolite. The suction line is connected to the bottom filling valve of the transformer, the oil is returned from the unit to the transformer through a valve at the top of the tank. Up to 11 liters of water can be removed with one set of cylinders.

Conclusion

1. Intelligent diagnostic system for power transformer equipment. After analyzing the known power transformer monitoring systems that meet all modern requirements, but at the same time there is no excessive overload with information flows.

2. The proposed diagnostic system can operate both autonomously, installed on a single transformer or electrical substation, and as part of a network monitoring system covering a certain area of electrical networks.

References

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2. Bubenchikov A.A., Nuraxmet E.E. Naibolee xarakternye neispravnosti v silovom oborudovanii. Mezhdunarodnyj nauchno-issledovatelskij zhurnal. Vypusk №5. Chast 3. 2016 g. S. 56-58.

3. Kostinskij S.S. Obzor sostoyaniya otrasli transformatornogo proizvodstva i tendencij razvitiya konstrukcii silovyx transformatorov. Zhurnal Izvestiya vysshix uchebnyx zavedenij. Energetika, №1, 2018

4. Bakar, N.A.; Abu-Siada, A.; Islam, S. A review of dissolved gas analysis measurement and interpretation techniques. IEEE Electr. Insul. Mag. 2014, 30, 39-49.

5. Coenen, S.; Siegel, M.; Luna, G.; Tenbohlen, S. Parameters influencing Partial Discharge Measurements and their Impact on Diagnosis. In Proceedings of the Monitoring and Acceptance Tests of Power Transformers CIGRE Session, Paris, France, 22-26 August 2016..

6. Coenen,S. Tenbohlen,S.Locationof P. D. sources in power transformers by UHF and acoustic measurements. IEEE Trans. Dielectr. Electr. Insul. 2015, 19, 1934-1940.

7. Repair of electrical equipment and machinery [electronic resource] / informational portal. URL: http://www.laborelec.be/ENG/services/electrical-equipment.

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