JP7152960B2 - Oil-immersed transformer and moisture removal device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oil-immersed transformer in which a core and windings are immersed in insulating oil, and a water removing device for removing water from the insulating oil.

Generally, in an oil-immersed transformer, an iron core and a winding composed of an electric wire wound around the iron core are immersed in an insulating cooling medium in a tank. The electric wire that constitutes the winding is covered with an insulator. Mineral oil, which has excellent insulating properties, is widely used as the insulating cooling medium. In recent years, biodegradable ester oil has been used as an insulating cooling medium instead of mineral oil.

A large amount of good quality wood pulp paper is used as an insulator for the windings. For example, kraft paper and crepe paper are used as insulating coatings for winding lead wires. In addition, various spacers to secure the flow path of the insulating cooling medium in the winding, insulators that make up the main insulation, support insulators placed above and below the winding to support the winding, and leads A press board made by strongly compressing paper is used as a material for an insulating cylinder constituting a wire barrier and a bracket for supporting spacers and lead wires. The insulation of the windings is a composite insulation of these insulating papers and mineral oil used as an insulating cooling medium.

Among the materials used for such oil-filled transformers, it is known that the characteristics of insulating cooling media such as mineral oil and insulators such as insulating paper deteriorate with age. It is believed that deterioration in characteristics due to aging deterioration is a factor in the aging deterioration of the transformer and affects the life of the transformer.

High reliability is required for oil-immersed transformers, which are important components for power distribution. Mineral oil, which is an insulating cooling medium, is known to deteriorate with age due to the involvement of oxygen and water, but it is known that the decrease in dielectric breakdown voltage is small. Mineral oil can usually be used for a long time if it is properly dehydrated during transformer manufacturing and there is no ingress of air and moisture from outside the tank. In addition, even if the characteristics deteriorate due to deterioration over time, it is possible to maintain the characteristics that do not hinder the operation of the transformer by replacing with new oil or performing a degassing filtration process.

On the other hand, the insulating paper provided on the windings has a reduced tensile strength due to deterioration over time, although the dielectric breakdown voltage hardly decreases. A decrease in the tensile strength of the insulating paper may adversely affect continued operation of the transformer. For example, when a surge current flows through a winding due to a lightning strike or an external short circuit, the electromagnetic mechanical force generated at this time exerts a tensile force on the coating of the winding. If the tensile strength of the insulating paper is lower than the tensile force generated in the covering of the winding, the insulating paper will be destroyed and its life will be shortened. Since it is generally impossible to rewind the insulating paper or replace the windings, it is believed that the life of the insulating paper determines the life of the transformer.

The insulating paper contains cellulose as a main component. Cellulose undergoes a decomposition reaction as it deteriorates over time. This decomposition reaction is roughly classified into three types: (1) oxidation reaction, (2) hydrolysis reaction, and (3) thermal decomposition reaction. It is thought that the presence of oxygen oxidizes hydroxyl groups in cellulose to produce carbonyl groups and carboxyl groups. On the other hand, it is believed that the presence of water hydrolyzes the ether bonds in the cellulose. When the main chain of cellulose is cut by the hydrolysis reaction, the degree of polymerization of the cellulose molecules is lowered, which is considered to lower the tensile strength of the insulating paper. Moreover, it is considered that the carboxyl group generated by the oxidation reaction of (1) or the like exhibits a catalytic action for this oxidation reaction. The thermal decomposition reaction (3) is a reaction in which chemical bonds are broken by heat, and is considered to occur at a higher temperature than the oxidation reaction (1) and the hydrolysis reaction (2). From the above, it is considered that the hydrolysis reaction of cellulose has a large effect on the decrease in tensile strength due to aged deterioration of the insulating paper.

Cellulose, which is the main component of insulating paper, is known to produce CO, CO ₂ , water (H ₂ O), and low-molecular-weight compounds such as furan compounds as it decomposes over time. By evaluating the amount of these compounds produced, the state of deterioration of insulating paper in transformers is estimated, and preventive maintenance of equipment is performed. Since it is difficult to estimate the deterioration state of insulating paper by analyzing the amount of water in the tank of a transformer, conventionally, CO, CO ₂ , furan compounds, etc. are mainly used as the main deterioration indicators of cellulose. .

Transformers are manufactured by drying the insulating paper and dehydrating the insulating oil, and by sealing the tank to prevent moisture from entering from the outside. However, as the operation time of the transformer increases, the aging deterioration of the insulating paper progresses and the generation of water is thought to increase the total amount of water in the sealed tank.

In transformer tanks, water is typically adsorbed on insulating papers with high affinity (eg, kraft paper) and slightly dissolved in mineral oil with low affinity. For this reason, the generation of water due to aged deterioration of insulating paper is considered to have a small effect on the insulating properties of mineral oil, but it is considered to have a large effect on the hydrolysis of cellulose. In addition, ester oil, which has been increasingly applied to transformers in recent years, has a very high affinity for water, and when the ester bond in ester oil is broken by hydrolysis reaction, acid and alcohol are generated. It has been known.

In Patent Document 1, an adsorbent case is detachably attached to a piping system that circulates insulating oil via a polymer film material, and an adsorbent for absorbing moisture is provided in the adsorbent case. A transformer is described that removes moisture from insulating oil.

JP 2007-221047 A

It is possible to remove the water in the insulating oil by disposing an adsorbent such as zeolite or silica that adsorbs water well in the insulating oil. Since these adsorbents also adsorb compounds other than water, there is a problem that if the adsorbent is directly placed in the insulating oil, it is difficult to sufficiently adsorb water.

Also, these adsorbents can only adsorb a certain amount of water per unit weight. Therefore, when the transformer is operated for a long period of time, there is a problem that the adsorption performance is lost after a certain period determined by the type and amount of the adsorbent. In order to solve this problem, the transformer described in Patent Document 1 has a detachable adsorbent so that the adsorbent can be replaced periodically. However, it is usually difficult to replace the adsorbent while the transformer is in operation, and it is desirable to stop the operation of the transformer in order to safely replace the adsorbent.

As a method for recovering the adsorption performance of the adsorbent, a method of heating the adsorbent to release water from the adsorbent is conceivable. However, when the adsorbent is zeolite or silica, it is necessary to heat it at a high temperature in order to release water, and when the adsorbent is placed in the insulating oil, the insulating oil is thermally deteriorated. There is

SUMMARY OF THE INVENTION An object of the present invention is to provide an oil-filled transformer capable of efficiently removing moisture from insulating oil over a long period of time without stopping operation, and a moisture removal device that can be installed in the oil-filled transformer. .

An oil-filled transformer according to the present invention includes a tank containing an iron core and windings, insulating oil contained in the tank, and connected to the tank, the insulating oil flows from the tank, and the insulating oil flows into the tank. A cooler that cools, a first adsorbent that adsorbs water contained in the insulating oil, and a heating device that heats the first adsorbent, are connected to the cooler and the tank, and the a water adsorption unit into which the insulating oil flows from the cooler and the insulating oil flows out to the tank; and a second adsorbent that adsorbs water contained in the insulating oil, and is connected to the water adsorption unit, and an adsorbent regeneration device for removing water contained in the insulating oil that has flowed from the water adsorption unit.

According to the present invention, it is possible to provide an oil-filled transformer capable of removing moisture in insulating oil efficiently for a long period of time without stopping operation, and a water removal device that can be installed in the oil-filled transformer.

1 is a schematic diagram showing the configuration of an oil-filled transformer according to an embodiment of the present invention; FIG.

In a conventional oil-immersed transformer, if moisture is present in the insulating oil, the insulating paper in the tank will hydrolyze the cellulose, which is the main component, and will deteriorate over time. Cellulose produces water through decomposition due to aging. Therefore, it is desired to remove the moisture in the tank.

The oil-filled transformer and water removal device according to the present invention can reduce the total amount of water in the tank of the oil-filled transformer by removing the water in the insulating oil of the oil-filled transformer. It is possible to suppress aging deterioration of the insulator (especially insulating paper) and insulating oil (especially ester oil) used as the insulating material.

Furthermore, with the oil-filled transformer and the water removal device according to the present invention, the deterioration state of the oil-filled transformer can be diagnosed from the amount of water removed from the insulating oil.

The oil-filled transformer and water removing device according to the present invention can regenerate the adsorbent for removing water during operation of the oil-filled transformer, and the adsorbent does not need to be replaced. Moisture in insulating oil can be efficiently removed without stopping the operation of the transformer over a long period of time when the oil-filled transformer is operated.

An oil-filled transformer and a water removal device according to embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of an oil-filled transformer according to an embodiment of the present invention. The oil-filled transformer according to this embodiment includes a tank 1, an iron core 2, an inner winding 3 and an outer winding 4 which are windings wound around the iron core 2, an insulating cylinder 5, insulating oil 6, nitrogen It comprises a gas 7, a cooler 8 and a moisture removal device according to an embodiment of the invention. The moisture removal device according to this embodiment will be described later.

A tank 1 contains an iron core 2 , an inner winding 3 , an outer winding 4 , an insulating cylinder 5 , insulating oil 6 and nitrogen gas 7 .

The iron core 2 is fastened and held by fasteners 10a and 10b attached to its upper and lower parts, respectively. The iron core 2 has, at its center, an oil introducing portion 15 which is a cavity into which the insulating oil 6 flows to cool the iron core 2 .

The inner winding 3 and the outer winding 4 are composed of wires coated with an insulator. An insulating cylinder 5 made of an insulator is provided between the core 2 and the inner winding 3, between the inner winding 3 and the outer winding 4, and between the outer winding 4 and the tank 1. ing. An insulator is provided between the wires forming the windings 3 and 4 in the inner winding 3 and the outer winding 4 . These insulators provided in the inner winding 3 and the outer winding 4 and the insulators constituting the insulating tube 5 are made of insulating paper (for example, kraft paper, crepe paper, and pressboard), insulating wood, and plastic. Any one or more can be used. In the following description, it is assumed that the insulators provided in the inner winding 3 and the outer winding 4 and the insulators forming the insulating tube 5 are made of insulating paper.

The insulating oil 6 insulates and cools the core 2, the inner winding 3 and the outer winding 4. FIG. Insulating oil 6 may be mineral oil, which is widely used in oil-filled transformers, silicone fluid, ester oil, or the like.

Nitrogen gas 7 exists above the insulating oil 6 inside the tank 1 .

The cooler 8 is installed outside the tank 1 and connected to the tank 1 by pipes 9a and 9b installed in the upper and lower parts of the tank 1, respectively. The cooler 8 cools the insulating oil 6 accommodated inside the tank 1 by an air-cooling system using fins or fans or a water-cooling system. A pipe 9 a allows the insulating oil 6 in the tank 1 to flow to the cooler 8 . The pipe 9 b allows the insulating oil 6 cooled by the cooler 8 to flow to the tank 1 .

The insulating oil 6 absorbs Joule heat generated from the iron core 2, the inner winding 3 and the outer winding 4 provided inside the tank 1, and cools the iron core 2, the inner winding 3 and the outer winding 4. As shown by the arrow 1, it flows from the inside of the tank 1 to the inside of the cooler 8 through the upper pipe 9a. The insulating oil 6 that has flowed into the cooler 8 flows from the cooler 8 into the tank 1 after being cooled by the cooler 8 . Insulating oil 6 circulates between tank 1 and cooler 8 by convection or driven by a pump.

Insulators 11 and 12 are installed above the inner winding 3 and the outer winding 4 , and insulators 13 and 14 are installed below the inner winding 3 and the outer winding 4 . Insulators 11, 12, 13, 14 can be composed of insulating paper (eg, kraft paper, crepe paper, and pressboard), insulating wood, and plastic. In the following, the insulators 11, 12, 13, 14 are assumed to be made of insulating paper.

The oil-filled transformer according to this embodiment includes a water adsorption section 19 and an adsorbent regeneration device 21 . The water adsorption part 19 and the adsorbent regeneration device 21 constitute the water removal device according to this embodiment.

The water adsorption unit 19 includes a water adsorbent 17 , a heating device 18 , and a container for accommodating them, and removes water contained in the insulating oil 6 cooled by the cooler 8 .

The water adsorbent 17 adsorbs and removes water contained in the insulating oil 6 . As the water adsorbent 17, insulating paper having a high affinity for water (for example, kraft paper and aramid paper) can be used.

The heating device 18 is installed at a position where the water adsorbent 17 can be heated, heats the water adsorbent 17, and dissolves the water adsorbed by the water adsorbent 17 into the insulating oil in the water adsorption part 19. . Any device can be used as the heating device 18 as long as it can heat the water adsorbent 17 .

The water adsorption part 19 is connected to the cooler 8 by the pipe 16 a , and the insulating oil 6 cooled by the cooler 8 flows from the cooler 8 . The water adsorption unit 19 is connected to the tank 1 by a pipe 16b, and the insulating oil 6 from which water has been removed by the water adsorbent 17 flows out to the tank 1 as indicated by the arrow. The pipe 16 a flows the insulating oil 6 cooled by the cooler 8 to the water adsorption portion 19 . The pipe 16 b is connected to the lower part of the tank 1 and flows the insulating oil 6 from which water has been removed by the water adsorbent 17 into the tank 1 . The insulating oil 6 circulates through the cooler 8 , the water adsorption section 19 and the tank 1 by convection or driven by a pump.

The adsorbent regeneration device 21 includes a water adsorbent 22 and a container that stores the water adsorbent 22 , and removes water contained in the insulating oil 6 flowing from the water adsorption section 19 .

The water adsorbent 22 adsorbs and removes water contained in the insulating oil 6 . For example, zeolite or silica can be used as the water adsorbent 22 .

The adsorbent regeneration device 21 is connected to the water adsorption section 19 via pipes 20a and 20b. The insulating oil 6 in which the water adsorbent 17 is heated by the heating device 18 and the water is eluted flows into the adsorbent regeneration device 21 from the water adsorption section 19 through the pipe 20a. In the adsorbent regeneration device 21, the insulating oil 6 from which water has been removed by the water adsorbent 22 flows out to the water adsorption section 19 through the pipe 20b. The pipe 20 a flows the insulating oil 6 eluted with water in the water adsorption part 19 to the adsorbent regeneration device 21 . The pipe 20 b flows the insulating oil 6 from which water has been removed by the adsorbent regeneration device 21 back to the water adsorption section 19 . The insulating oil 6 is driven by a pump to circulate through the water adsorption section 19 and the adsorbent regeneration device 21 .

A procedure for controlling the flow of the insulating oil 6 and removing moisture contained in the insulating oil 6 in the oil-filled transformer according to the present embodiment will be described below. Valves provided in the pipes 9a, 9b, 16a, 16b, 20a, and 20b are opened and closed by an operator or a control device.

During normal operation, in the oil-filled transformer, the valves provided on the pipes 9a and 9b are open, and the valves provided on the pipes 16a and 16b and the pipes 20a and 20b are closed. As a result, the insulating oil 6 flows from the tank 1 through the pipe 9a to the cooler 8, is cooled by the cooler 8, and then flows from the cooler 8 to the tank 1 through the pipe 9b.

When removing the moisture contained in the insulating oil 6, in the oil-filled transformer, the valve provided on the pipe 9b is closed and the valves provided on the pipes 16a and 16b are opened. The valve provided in line 9a remains open and the valves provided in lines 20a, 20b remain closed. As a result, the insulating oil 6 flows from the tank 1 through the pipe 9 a to the cooler 8 , is cooled by the cooler 8 , and then flows from the cooler 8 through the pipe 16 a to the water adsorption section 19 .

The water adsorbent 17 provided in the water adsorption portion 19 adsorbs and removes water contained in the insulating oil 6 that has flowed into the water adsorption portion 19 . The insulating oil 6 cooled by the cooler 8 and water removed by the water adsorbent 17 flows from the water adsorbing portion 19 to the tank 1 through the pipe 16b and cools the inner winding 3 and the outer winding 4 .

In this way, the insulating oil 6 whose temperature has risen by cooling the inner winding 3 and the outer winding 4 flows from the tank 1 through the pipe 9a to the cooler 8, is cooled by the cooler 8, and is cooled by the cooler 8. 8 flows to the water adsorption section 19 through the pipe 16a, and the water adsorption section 19 removes water. The removal of water from the insulating oil 6 by the water adsorption unit 19 is performed for a certain period of time determined by the type and amount of the water adsorbent 17 .

After the moisture is removed from the insulating oil 6 by the water adsorption part 19 during this certain period of time, the valve provided on the pipe 9b is opened and the valves provided on the pipes 16a and 16b are closed. The valve provided in line 9a remains open and the valves provided in lines 20a, 20b remain closed. Since the valve provided in the pipe 9b is opened, the insulating oil 6 flows from the tank 1 through the pipe 9a to the cooler 8, is cooled by the cooler 8, and then flows from the cooler 8 through the pipe 9b to the tank. flow to 1. The insulating oil 6 does not flow into the water adsorption portion 19 from the cooler 8 and does not flow out from the water adsorption portion 19 to the tank 1 . The insulating oil 6 that has not flowed into the tank 1 exists inside the water adsorption portion 19 .

In this state (that is, when the insulating oil 6 does not flow from the cooler 8 to the water adsorption portion 19 and does not flow out from the water adsorption portion 19 to the tank 1), the heating device 18 heats the water adsorbent 17. do. The water adsorbent 17 releases adsorbed water to the insulating oil 6 in the water adsorbing portion 19 when heated. The water released from the water adsorbent 17 elutes into the insulating oil 6 . The heating device 18 heats the water adsorbent 17 at a temperature and time such that the water adsorbent 17 and the insulating oil 6 do not deteriorate.

When the heating device 18 heats the water adsorbent 17, the valves provided in the pipes 20a and 20b are opened. The insulating oil 6 eluted with water released from the water adsorbent 17 by heating flows from the water adsorption part 19 into the adsorbent regeneration device 21 through the pipe 20a. The insulating oil 6 that has flowed into the adsorbent regeneration device 21 is freed of the water it contains, and flows back to the water adsorption section 19 through the pipe 20b.

The adsorbent regeneration device 21 removes water contained in the insulating oil 6 flowing from the water adsorption part 19 with the water adsorbent 22 . As the insulating oil 6 circulates through the water adsorption unit 19 and the adsorbent regeneration device 21 , the water released from the water adsorbent 17 is adsorbed by the water adsorbent 22 and removed.

In this way, the water adsorbent 17 of the water adsorption part 19 can release the adsorbed water to recover the water adsorption performance and regenerate. The regeneration of the water adsorbent 17 is determined according to the type and amount of the water adsorbent 17, the type and amount of the water adsorbent 22 in the adsorbent regeneration device 21, and the heating time of the water adsorbent 17. over a period of time.

When the regeneration of the water adsorbent 17 is completed, the heating of the water adsorbent 17 by the heating device 18 is stopped, and the valves provided in the pipes 20a and 20b are closed. Thereafter, the oil-filled transformer may be operated normally with the valve provided in the pipe 9b opened and the valves provided in the pipes 16a and 16b closed, or Water contained in the insulating oil 6 may be removed by the water adsorption section 19 by closing the valves and opening the valves provided in the pipes 16a and 16b.

The removal of the moisture contained in the insulating oil 6 by the water adsorption part 19 can be performed at any time, for example, it can be performed periodically at each lapse of a predetermined period of time.

The water adsorbent 22 can be replaced as necessary when the valves provided in the pipes 20a and 20b are closed and the water adsorbent 17 is not being regenerated.

In this way, the oil-filled transformer according to the present embodiment removes water from the insulating oil 6 with the water adsorbent 17 provided in the water adsorption part 19 during operation of the oil-filled transformer, and the adsorbent regeneration device At 21 the water sorbent 17 can be regenerated. Since the water adsorbent 17 is reproducible and does not need to be replaced, the oil-filled transformer according to the present embodiment can be efficiently used without stopping operation, and can be used in the insulating oil 6 for a long period of time when the oil-filled transformer is operated. of moisture can be removed.

Since the insulating paper forming the water adsorbent 17 is heated by the heating device 18, it is preferably made of heat-resistant paper. If heat-resistant paper is used for the water adsorbent 17, deterioration due to repeated heating by the heating device 18 can be suppressed. Any heat-resistant paper can be used, such as amine-added paper or aramid paper.

When the oil-filled transformer according to this embodiment is used, the amount of water removed from the insulating oil 6, that is, the amount of water adsorbed by the water adsorbent 17 is used to decompose the insulating paper in the tank 1 due to deterioration over time. can estimate the amount of water The amount of water generated due to aged deterioration of the insulating paper in the tank 1 can be obtained, for example, by the following method. A standard amount of water generated by insulating paper due to deterioration over time is obtained by experiments or by using past data. Next, the amount of water adsorbed by the water adsorbent 22 is determined using an existing method, and the amount of water adsorbed by the water adsorbent 17 is estimated from the determined amount of water. From this estimated amount of water and the standard amount of water described above, the amount of water generated due to aging deterioration of the insulating paper in the tank 1 can be estimated.

Moreover, when the oil-filled transformer according to this embodiment is used, the deterioration state of the insulating paper in the tank 1 can be accurately determined by estimating the amount of water generated by the decomposition of the insulating paper in the tank 1 due to deterioration over time. Diagnosis can be performed, and the accuracy of diagnosing the deterioration state of the oil-filled transformer can be improved.

The estimation of the amount of water generated due to aging deterioration of the insulating paper in the tank 1 and the diagnosis of the deterioration state of the oil-filled transformer may be performed by a computer or by an operator.

The water removal device provided in the oil-filled transformer according to the present embodiment, that is, the water adsorption unit 19 and the adsorbent regeneration device 21, are based on the existing oil-filled transformer (a tank containing an iron core, windings, and insulating oil, and a tank containing insulating oil). can be installed in an oil-filled transformer with a cooling cooler). By using the water removing apparatus according to the present embodiment, even in an existing oil-filled transformer, the water adsorbent 17 removes water from the insulating oil 6 while the oil-filled transformer is in operation, and the water adsorbent 17 is removed. It can be recycled, the amount of water generated by the decomposition of the insulating paper due to aged deterioration can be estimated, and the deterioration state of the oil-filled transformer can be diagnosed with higher accuracy.

It should be noted that the present invention is not limited to the above embodiments, and various modifications are possible. For example, the above embodiments have been described in detail in order to facilitate understanding of the present invention, and the present invention is not necessarily limited to aspects having all the described configurations. Also, part of the configuration of one embodiment can be replaced with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. Moreover, it is possible to delete a part of the configuration of each embodiment, or to add or replace another configuration.

DESCRIPTION OF SYMBOLS 1... Tank, 2... Iron core, 3... Inner coil, 4... Outer coil, 5... Insulating tube, 6... Insulating oil, 7... Nitrogen gas, 8... Cooler, 9a, 9b... Piping, 10a, 10b... Fasteners 11, 12, 13, 14 Insulator 15 Oil introducing portion 16a, 16b Piping 17 Water adsorbent 18 Heating device 19 Water adsorbing portion 20a, 20b Piping , 21... adsorbent regeneration device, 22... water adsorbent.

Claims (6)

a tank containing the iron core and the winding;
insulating oil contained in the tank;
a cooler connected to the tank, into which the insulating oil flows from the tank and cools the insulating oil;
a first adsorbent that adsorbs water contained in the insulating oil; and a heating device that heats the first adsorbent. a water adsorption portion into which the insulating oil flows and the insulating oil flows out into the tank;
an adsorbent regeneration device that includes a second adsorbent that adsorbs water contained in the insulating oil, is connected to the water adsorption unit, and removes water contained in the insulating oil that has flowed in from the water adsorption unit;
An oil-immersed transformer comprising: The heating device heats the first adsorbent when the insulating oil does not flow from the cooler into the water adsorption unit and does not flow out from the water adsorption unit into the tank.
The oil-filled transformer according to claim 1. When the heating device heats the first adsorbent, the adsorbent regeneration device uses the second adsorbent to remove water contained in the insulating oil that has flowed in from the water adsorption unit.
The oil-filled transformer according to claim 2. The first adsorbent is insulating paper,
The oil-filled transformer according to claim 1. The insulating paper is made of heat-resistant paper,
The oil-filled transformer according to claim 4. It can be installed in an oil-immersed transformer comprising a tank containing an iron core, windings and insulating oil, and a cooler for cooling the insulating oil,
a first adsorbent that adsorbs water contained in the insulating oil; and a heating device that heats the first adsorbent. a water adsorption portion into which the insulating oil flows and the insulating oil flows out into the tank;
an adsorbent regeneration device that includes a second adsorbent that adsorbs water contained in the insulating oil, is connected to the water adsorption unit, and removes water contained in the insulating oil that has flowed in from the water adsorption unit;
A moisture removing device comprising:

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