JPH0354846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a separate type evaporative cooling induction electric appliance in which a non-condensable insulating gas and a condensable cooling medium are separated by a closed insulating container.

[Prior art and its problems]

In recent years, there has been an increasing demand for high-voltage, large-capacity transformers, reactors, and other induction electrical appliances to be non-combustible and flame-retardant, mainly from the standpoint of disaster prevention. fluorocarbon, having
Evaporative cooling induction electric appliances that use condensate such as Freon as a cooling medium and insulating gas such as SF ₆ gas as an insulating medium are attracting attention, and compared to insulating oil, they use much less expensive cooling medium and have better cooling performance. In addition to being excellent,
There is a need for induction electric appliances that can handle high voltage.

FIG. 5 is a schematic side sectional view showing an example of an evaporative cooling induction electric appliance, and FIG. 6 is a schematic side sectional view showing an example of an evaporative cooling induction electric appliance of a dispersion type and FIG. 6 of a separate type. In the case of the condensate dispersion type, the disk winding 3 is housed in a tank 1 containing a cooling medium 10 and an insulating gas 9, and is made up of a plurality of section coils 4 and an inter-section duct 7 wound around an iron core 2. The condensate is stored in an insulating container 5 formed to surround it, and is transferred via condensate transfer means 11 to 13 to a dispersion device 14 disposed above the iron core 2, where it is dispersed through small holes 15. The iron core 2 is evaporatively cooled by receiving the liquid flow 10A of the condensate 10, and the disc winding immersed in the condensate 10 stored in the insulating container 5 is cooled by the latent heat of evaporation of the condensate and vaporized. The condensed liquid vapor 10B is condensed again in the condenser 6 and returned to the bottom of the tank 1.

In the scatter type evaporative cooling induction electric appliance constructed as described above, the iron core and the winding can be simultaneously and efficiently evaporatively cooled without causing liquid drying up. The large amount of condensate used creates an economic disadvantage, and since winding cooling relies solely on the latent heat of vaporization of the condensate, the winding temperature is significantly dependent on the boiling point temperature of the cooling medium. There is a problem in that as the electrical load of the induction appliance increases, a large amount of bubbles are generated in the insulation tank 5, and the withstand voltage performance of the winding 3 is reduced.

On the other hand, in the separate type shown in FIG.
and a heat exchanger 26, the sealed insulating container 2
5. A condensate 10 and a tank 1 contained in a closed circulation system such as a heat exchanger 26 so that the winding 3 is immersed therein.
A condensate 10 is formed to separate the insulating gas 9 contained therein, and is circulated between the closed insulating container 25 and the heat exchanger 26 by the pump 21.
The winding 3 is configured to be cooled using both sensible heat and latent heat. Therefore, the amount of condensate used can be reduced, and the sensible heat and latent heat of the condensate can be used to cool the windings, so there are fewer restrictions on the boiling point temperature of the cooling medium, and it is possible to achieve a comprehensive combination of cooling performance and price. It has the advantage of being able to evaluate and select an advantageous cooling medium.

By the way, in general, the withstand voltage performance of condensable cooling media is high in the liquid phase and low in the gas phase, so whether the windings have many localized electric field concentration parts in either the dispersed type or the separate type, By immersing it in liquid phase insulation and insulating the space away from the winding where there is little local electric field concentration,
It has the advantage of providing an induction electric appliance with excellent withstand voltage performance, in other words, an induction electric appliance that can be used at high voltages. However, as the condensate in which the windings are immersed is boiled, the area around the windings becomes a mixed gas-liquid insulation, which goes against the improvement of cooling performance and reduces withstand voltage performance. There is a drawback that voltage conversion is inhibited.

FIG. 7 is a side sectional view of the main part showing the above-mentioned state, and the outer circumferential side of the disc winding consisting of a plurality of section coils 4 and the inter-section duct 7 is insulated to hold the axial duct 8. Container 5 or 15
It is assumed that the container is filled with condensate 10 and the space outside the container is filled with insulating gas 9. If a voltage is easily applied to the winding in such a state, the electric field will be locally concentrated at the corner of the section coil 4 due to the potential difference between the section coils and the ground potential of the section coil, causing condensation near the corner. A high electric field portion is generated in the liquid 10C portion. Now, when the temperature of the section coil rises due to the current flowing through the winding and exceeds the boiling point temperature of the condensate 10, the condensate in contact with the surface of the section coil 4 begins to boil, and the vaporized vapor becomes bubbles. The air bubbles gather in the axial duct 8 as the air bubbles float along the lower and side surfaces of the section coil, and during the process of floating through the axial duct, air bubbles 10D grow, causing the air bubbles 10D to float along the axially upper side of the section coil. A state as shown in the figure appears, where the bubble density is higher at the corners.
In such a state, the bubble 10D is not only exposed to a high electric field, but also has a smaller dielectric constant than the condensed liquid, so the electric field concentrates on the bubble based on the principle of capacitance partial pressure, and the liquid There is a risk that spark discharge will occur in the bubbles, which have a lower withstand voltage strength than the phase, and this will trigger an insulation accident such as dielectric breakdown between the section coils. This has become a serious weakness that hinders the development of society.

Furthermore, by applying the pressure of the insulating gas 9 to the liquid level of the condensate 10 in the insulating layer 5 as shown in the scattering type shown in FIG. 5, the steam bubbles 10 can be crushed and the withstand voltage strength can be increased. Expected, but gauge pressure
The withstand voltage strength of the gas phase that can be achieved by applying a gas pressure of about 0.5 to 1 atm is only about half that of the liquid phase, and there is a problem that the influence of vapor bubbles cannot be eliminated, so further improvement is required. is required.

[Purpose of the invention]

The present invention was made in view of the above-mentioned situation, and
It is an object of the present invention to provide a separate type evaporative cooling induction electric appliance which eliminates the influence of vapor bubbles generated as a result of boiling of condensate on the withstand voltage performance of the windings, and has excellent withstand voltage performance.

[Key points of the invention]

The present invention is configured to surround and house the windings and communicate with a heat exchanger externally installed in a tank through a pair of upper and lower circulation passages, and store enough condensed liquid of a cooling medium to immerse the windings. A hermetically insulated container, and a communication pipe arranged substantially coaxially between the container and the winding to maintain a separation distance between the container and the winding, respectively, to form an axial passage for the condensate. a double insulating container formed of an inner insulating container formed to communicate with the heat exchanger; and a distribution hole for the condensate formed in a side plate of the inner insulating container so as to communicate with both axial passages; ,
It is equipped with a circulation passage and a flow rate regulating valve disposed at least on the outlet side of the communication pipe, and when the induction electric device is under a light load, condensed liquid is circulated within the winding in the inner insulating container to perform sensible heat cooling. During heavy loads, by adjusting the flow rate adjustment valve, the condensate that has flowed into the inner insulated container is guided into the axial passage of the outer sealed insulated container through the communication hole and circulated to the heat exchanger side via the communication pipe. With this structure, steam bubbles generated when the condensate near the windings boils when the induction electric appliance is under heavy load are immediately transferred to the outer airtight insulating container together with the condensate through the flow holes in the vicinity of the bubble generating section. Since the vapor bubbles are guided through the axial passage and away from the vicinity of the winding, it is possible to eliminate the vapor bubbles present in the high electric field area at the corner of the section coil, and also prevent the accumulation of bubbles near the section coil located at the upper position in the axial direction. Therefore, it is possible to prevent deterioration in voltage resistance performance due to vapor bubbles.

[Embodiments of the invention]

The present invention will be explained below based on examples.

FIG. 1 is a schematic side sectional view showing an embodiment of the present invention. In the figure, a winding 3 wound around an iron core 2 housed in a tank 1 containing an insulating gas 9 such as SF ₆ gas contains a condensate 10 of a condensable cooling medium such as fluorocarbon or fluorocarbon. An axial passage 3 for the condensate 10 is provided between a hermetically sealed insulating container 35 that is formed to be airtight, and the hermetically insulating container 35 and the winding 3 disposed inside the hermetically sealed insulating container 35.
It is housed in a double insulating container consisting of an inner insulating container 36 formed to maintain a separation distance of 8 and 39. In addition, airtight insulating container 3
5 is connected to a heat exchanger 26 externally installed in the tank 1 via a pair of upper and lower circulation passages 32A, 32B, and a flow rate adjustment valve 31 is connected to the upper circulation passage 32A.
A is provided, and the inner insulating container 36 communicates with the axial passage 39 on the anti-winding side through a plurality of communication holes 37 distributed and formed in the side plate, and the upper end thereof is connected to the communication pipe 33 and It communicates with the heat exchanger 26 via the flow rate adjustment valve 31B, and a liquid supply/drainage valve 4 is provided at the lower end.
3 is provided. Therefore, the condensate 10 is transferred to the closed insulating container 36, the heat exchanger 26, and the circulation pump 21.
The winding 3 is electrically insulated by a double insulating container near the winding. Condensate 1 stored inside it
0 and the part remote from the winding 3 by an insulating gas 9.

In the evaporative cooling induction electric appliance configured as described above, when the electrical load is light and the winding temperature is lower than the boiling point of the condensate, the flow adjustment valve 31B is closed and the circulation passage side valve 31A is opened. ,
The condensate 10 is circulated through an axial passage 38 adjacent to the windings in an inner insulating vessel 36 to provide sensible cooling of the windings, while the insulation near the windings has a voltage withstand voltage free from vapor bubbles. It is retained by the highly strong condensate 10, and high withstand voltage performance can be obtained.

Next, when the electrical load on the induction device increases and the winding temperature exceeds the boiling point temperature of the condensate, the flow rate adjustment valve 31A on the circulation passage 32A side is almost closed, and the flow rate adjustment valve 31B on the communication pipe 33 side is closed. By almost fully opening the lower circulation passage 32B
The condensate 10 flowing into the axial passage 38 of the inner insulating container 36 from the axial passage 3 through the communication hole 37
Since it is possible to apply a radial component force that leads to the winding 3 side, the steam bubbles generated in each section coil of the winding 3 can be pushed along with the condensate in the axial direction on the opposite winding side. It can be discharged to the passage 39 side. Therefore, by forming distribution holes 37 in the side plate of the inner insulating container 36 in a size that allows steam bubbles to pass through, distributed in the axial and radial directions, the winding side in contact with the corner of the section coil is formed. Since the steam bubbles in the axial passage 38 can be quickly removed, it is possible to prevent the voltage withstanding performance from deteriorating due to the steam bubbles.

FIG. 2 is an explanatory diagram showing the state of steam bubbles in the above-described embodiment. Since the steam bubbles 10D flow into the directional passage 39, the component force of the radial flow generated by these many branched flows causes the steam bubbles 10D to flow out from the communication hole toward the axial passage 39, resulting in a liquid flow of condensate containing steam bubbles. 20 is led through an axial passage 39 to a heat exchanger. The axial passage 39 is the high electric field section 1
Since it is far from 0C, there is no risk of spark discharge occurring in the air, and the amount and size of bubbles in the high electric field section 10C is significantly reduced, greatly improving the withstand voltage performance of the winding. can be improved.
In addition, the air bubbles generated in each section coil can be discharged from the distribution holes formed laterally and can be prevented from accumulating and staying at the corner of the axially upper section coil of the axial passage 38. , the flow rate of the condensate in the axial passage 38 is slow on the downstream side, but on the contrary, it becomes faster on the axial passage 39 side. Therefore, on the downstream side, the suction action to draw out the steam bubbles to the axial passage 39 side is automatically performed. steam bubbles can be more effectively eliminated.

In addition, if a variable volume part such as a bellows protruding toward the insulating gas space is provided in the circulation passage or the communication pipe in FIG. 1, and the pressure of the insulating gas 9 is applied to the condensate 10, the internal pressure of the steam bubbles can be increased. This makes it possible to further improve withstand voltage performance. In addition, by configuring the flow rate adjustment valves 31A and 31B to be controlled based on an output signal from a detector, such as a current transformer, that detects the load state of the induction electric device, it is possible to save labor in switching work, and also to realize sensible heat cooling and Boiling cooling can be performed efficiently.

FIG. 3 is a side sectional view of a main part showing a different embodiment of the present invention. 49 are provided alternately on the inner diameter side and the outer diameter side in the axial direction of the winding 3 to cause the condensate 10 to flow in a zig-zag pattern in the inter-section duct 7 of the winding 3, and downstream of the flow in the inter-section duct 7. This embodiment differs from the previous embodiment in that the communication holes 47 are formed in a distributed manner in the side plate portion of the inner insulating container 36 on the opposite side.

FIG. 4 is an explanatory diagram showing the state of steam bubbles in the above-mentioned embodiment. By flowing the condensate in a zig-zag pattern through the inter-section duct 7, a radial component force is forced on the flow of the condensate. The steam bubbles 10D can be quickly discharged to the axial passage 39 side through the distribution holes 47 formed in the downstream side plate that directly receives the component force of this flow. Not only the steam bubbles attached to the lower surface of the coil 4 but also the steam bubbles near the high electric field section 10C are eliminated before they grow or gather.
Deterioration in voltage resistance performance due to vapor bubbles can be more effectively prevented.

〔Effect of the invention〕

As described above, the present invention includes a closed insulating container formed to store windings and condensate separately from an insulating gas space and communicate with a heat exchanger via a pair of upper and lower circulation passages and a flow rate regulating valve; Inside the container, the container and each of the windings are arranged to maintain a distance that should form an axial passage for the condensate, and distribution holes communicating with both axial passages are formed in the side plate. In addition, a double insulating container is provided with an inner insulating container whose upper end is formed to communicate with the heat exchanger via a communication pipe and a flow rate adjustment valve, and when the induction device is under light load, the flow rate on the circulation passage side is adjusted. When the valve is mainly opened, the condensate circulates in the axial direction inside the inner insulated container to perform sensible heat cooling.When the load is heavy, the flow rate adjustment valve on the communication pipe side is mainly opened and the condensate flows through the circulation hole. It was configured so that the flow was distributed from the inner insulating container side to the outer insulating container side. As a result, during sensible heat cooling, the high electric field area near the windings is insulated by the condensate with high withstand voltage strength, and when the load is heavy, the condensate moves radially through the flow holes, causing the condensate to cool. A radial component force is generated in the flow of the winding, and the steam bubbles generated by the boiling of the condensate on the surface of each section of the winding are passed through the flow holes into a closed insulating container with little local electric field concentration. Since it can be discharged to the axial passage side of the side, it is possible to prevent the deterioration of the withstand voltage performance of the winding caused by the presence of many steam bubbles in the high electric field area near the corner of the section coil, improving insulation reliability. Therefore, it is possible to provide an evaporative cooling induction electric appliance with high performance and high voltage.

In addition, the flow velocity of the condensate in the axial passages on the winding side and the anti-winding side, which are communicated with each other through the flow holes, decreases on the winding side and increases on the anti-winding side as it goes downstream. It is possible to naturally generate the effect of sucking out steam bubbles to the axial passage side on the side opposite to the winding through the flow holes. Therefore, the closer the section coil is located in the upper position in the axial direction, the more easily the steam bubbles accumulate, and the more easily the steam bubbles accumulate. This provides the advantage of eliminating the conventional problem of large voltage performance drop. Furthermore, if the condensate is made to flow in a zig-zag pattern in the duct between sections of the winding, and a flow hole is provided on the downstream side of the duct, the radial component force of the flow of the condensate can be reduced. Therefore, it is possible to more actively discharge steam bubbles, and there is an advantage that deterioration of withstand voltage performance due to steam bubbles can be more effectively prevented.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention, and FIG.
The figure is an explanatory diagram showing the state of steam bubbles, Figure 3 is a side sectional view of the main part showing a different embodiment, Figure 4 is an explanatory diagram showing the state of steam bubbles, and Figure 5 is conventional scattering type evaporative cooling. FIG. 6 is a side sectional view showing an example of an induction electric appliance, FIG. 6 is a side sectional view showing an example of a separate type, and FIG. 7 is an explanatory diagram showing the state of steam bubbles in the prior art. DESCRIPTION OF SYMBOLS 1... Tank, 2... Iron core, 3... Winding wire, 4... Section coil, 5... Insulating container, 7... Duct between sections, 9... Insulating gas, 10... Condensate, 10C... High electric field part, 10D... Steam bubble , 20... Condensate containing bubbles, 21... Circulation pump, 25, 35... Sealed insulating container, 26... Heat exchanger, 36, 46... Inner insulating container, 37, 47... Distribution hole, 38... Axial passage ( winding side), 39...Axial passage (counter-winding side), 31
A, 31B...Flow rate adjustment valve, 22, 23, 32A,
32B...Circulation passage, 33...Communication pipe, 49...Liquid stopper.

Claims (1)

[Claims] 1. A winding wire wound around an iron core and housed in a tank having an external heat exchanger and containing insulating gas;
and a hermetically sealed insulating container that surrounds and accommodates this winding and communicates with the heat exchanger via a circulation passage, and the winding is cooled by a condensed liquid of an insulating medium that circulates through the hermetically insulated container and the heat exchanger. An inner insulator disposed inside the hermetically insulating container so as to maintain an axial passage between the hermetically insulating container and the winding, respectively, and communicating with the heat exchanger via a communication pipe. container,
The inner insulating container also includes a plurality of distributed liquid guide holes formed in the side plate thereof so as to communicate with the sealed insulating container, and a flow rate regulating valve provided in the circulation passage and the communication pipe. Evaporative cooling induction appliances. 2. In what is stated in claim 1,
The winding consists of a layered assembly of a flat ring-shaped section coil and an inter-section duct, and each of the plurality of section coils is provided with liquid stoppers alternately on the inner and outer diameter sides of the section coil. An evaporative cooling induction electric appliance characterized in that communication holes are provided distributed in a side plate of an inner sealed container in a portion facing the downstream side of a condensate flowing in a zigzag shape. 3 In what is stated in claim 1,
1. An evaporative cooling induction electric appliance, characterized in that a flow rate regulating valve provided in each of the circulation passage and the communication pipe is controlled by an output signal of a load information detection means of the induction electric appliance.