RU203274U1 - COMPRESSED AIR FILLED TRANSFORMER - Google Patents

Abstract

The utility model relates to electrical engineering, namely to power transformers. The technical result of the invention is to achieve absolute environmental friendliness of the transformer by replacing the SF6 gas with compressed air while maintaining fire and explosion safety. The technical result is achieved due to the fact that air as an insulating and cooling medium is pumped from the environment into the transformer tank to the required pressure. The air pressure is chosen such that the basic technical characteristics of the transformer are equivalent to those of oil filled or SF6 transformers. 3 ill.

Description

The utility model relates to electrical engineering, to power transformers and can be used in the main electrical equipment of power plants, substations, and power transmission lines.

Known transformers / 1 / - electromagnetic static converters of electrical energy, having two or more inductively coupled primary and secondary windings. They serve to create a magnetic field through which electrical energy is transferred from the primary to the secondary. The magnetic circuit serves to strengthen the magnetic coupling between the windings. The transformers are filled with oil, which is an insulating and cooling medium.

However, such transformers are fire and explosive equipment, and also pose a certain environmental problem associated with the disposal of oil.

Transformers with synthetic fluid filling 121 are known which have a higher flash point. However, this does not completely remove the problem of fire and explosion safety, and the problem of ecology remains.

Known transformers with gas insulation / 3 /, enclosed in a metal tank, inside which there are a magnetic circuit and windings. The transformer is cooled by forced gas circulation. Gas is injected into the transformer tank by a supercharger and it, flowing through the channels of the magnetic circuit and windings, cools them. Heat transfer to the environment is carried out by a cooler. SF6 gas is used as a cooling and insulating gas.

The prototype of the proposed transformer is a gas-insulated transformer / 4 /. The transformer contains a magnetic circuit placed in a sealed metal case, two or more inductively coupled secondary windings. Cooling of windings and magnetic core is carried out by forced gas circulation. The external SF6 gas circuit consists of a gas blower and a cooler that removes heat to the environment. Such a transformer is fire and explosion proof, however, a significant amount of SF6 gas in the transformer creates a certain environmental problem. SF6 gas is an inert gas, however, if it leaks due to depressurization of the transformer tank, it creates a problem for the substation personnel, since such a transformer, as a rule, is located in closed rooms due to its fire and explosion safety. In addition, SF6 is a greenhouse gas that negatively affects the earth's atmosphere (Kyoto Protocol, Paris Agreement).

The technical result of the invention is to achieve absolute environmental friendliness of the transformer by replacing the SF6 gas with compressed air while maintaining fire and explosion safety.

The technical result is achieved due to the fact that air from the environment is injected by the compressor into the transformer tank to the required pressure. The air pressure is chosen such that the basic technical characteristics of the transformer are equivalent to those of oil filled or SF6 transformers.

The main technical tasks when creating a transformer are:

ensuring insulation requirements for a given voltage class;

ensuring the rated power of the transformer.

In order to satisfy the dielectric strength of the transformer insulation with the normalized test voltages, the choice of air pressure is based on the calculation of the initial voltages of partial discharges, as well as on the calculation of the development of an electric discharge in the insulating gaps of the transformer based on the available experimental data and data on the mechanism of the discharge development in compressed air. Since the dielectric strength of compressed air depends on the purity and humidity of the air, it is necessary to take measures to clean the air from contamination and to dry the air.

To ensure the required power, it is necessary to consider the processes of heat transfer in the transformer windings and cooler. The heat transfer coefficient is a function of gas pressure and gas velocity. Gas-dynamic and thermal calculations of the transformer and cooler windings make it possible to determine the air pressure that will provide the required power of the transformer.

According to the results of calculations for PP. 1 and 2 the air pressure (highest) is selected.

The specific version of the transformer is illustrated in the figures.

FIG. 1 shows a general view of the transformer. The transformer tank 1 contains a magnetic circuit and windings (primary and secondary). In the external circuit there are blowers 2, coolers 3, as well as gas valves 4. In addition, a filter drier can be provided in the external circuit to clean the air. There is also an on-load voltage regulator 5.

FIG. 2 shows a cross-section of the transformer tank. The tank space is divided by a screen 6, windings and a magnetic circuit 7 are placed in the tank.

In the operating mode, compressed air from the blower is supplied to the space under the screen 6, which rises up through the channels in the magnetic circuit and the high voltage and low voltage windings 7. Then, through the outlet, the air enters the external circuit 8 through the gas pipeline to the cooler, in which it gives off the accumulated heat into the external environment, and then the blower is directed again into the space under the screen 6.

The air velocity is determined by the characteristics of the blower and the gas-dynamic resistance of the transformer and cooler. FIG. 3 shows the dependences of gas-dynamic resistances on the gas flow rate of the transformer, cooler and blower. At the point of intersection of the characteristics of the blower and the total gas-dynamic resistance of the transformer and the cooler, the gas flow rate is determined in m ³ / s. Further, depending on the cross-sections of the channels of the magnetic circuit and windings, the speeds in these channels and in the cooler are determined. The temperature of the gas at the inlet and outlet of the cooler is determined from the thermal characteristic of the cooler for a known gas velocity and power loss of the transformer. The thermal calculation of the transformer for known gas flow rates in the channels and its temperature at the transformer inlet determines the maximum temperatures of the coil conductors and the temperature of the magnetic circuit.

The insulation characteristics of various transformer units are determined by calculation based on the experimentally determined and known dependence of the air ionization coefficient on the gas pressure, as well as the experimentally determined characteristics of the main insulation gaps of the transformer.

List of used sources of information:

1. A.V. Sapozhnikov, Design of transformers, 1959, Gosenergoizdat.

2. Z.D. Wang, Q. Liu, X. Wang and others. Ester insulating liquids for power transformers, OGRE 2012, A2-209.

3. Patent JP 2011077385 2011.04.14

4. Gura Yu.L. "Gas-filled power transformer", Electric, No. 1-2, 2009.

Claims (2)

1. A transformer containing a magnetic circuit placed in a sealed metal case, two or more inductively coupled primary and secondary windings, an external forced gas circulation circuit, consisting of a gas blower and a cooler, characterized in that air under excess pressure is used as an insulating and cooling medium ... 2. The transformer according to claim 1, characterized in that the external contour of the forced gas circulation is equipped with a filter-dryer of air.

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