JPS5917842B2 - Cooling method for oil-immersed transformer - Google Patents

Description

Detailed Description of the Invention 5 The present invention relates to a method for cooling an oil-immersed transformer, and in particular to an oil-immersed transformer cooling method that uses both forced circulation cooling to operate an oil feed pump and natural circulation cooling to stop the oil feed pump depending on the usage rating. The present invention relates to a method for cooling an input transformer.

In general, an oil-filled transformer that uses both forced and natural circulation cooling is installed concentrically with the core 2 and other windings (not shown) in an oil tank 1, as shown in Figure 1. Therefore, between the inner insulating cylinder 5 and the outer insulating cylinder 6, a plurality of coils 3A formed by winding a conductor in a disk shape or a spiral shape are stacked in the axial direction, and a winding 3 is arranged. ,
Insulating oil 10 is sealed. This oil tank 1 has a cooler 9.
are connected by an upper pipe 8 and a lower pipe 7, and the insulating oil 10, which has undergone heat exchange with a cooler 9, is sent to a common oil pipe 4 provided in the oil tank 1. The lower pipe 7 (or the upper pipe 8) is provided with an oil pump P, and a side pipe 11 is provided in parallel with the oil pump P. Side passage piping 3
are connected via, for example, a check valve (not shown) that is closed to prevent the insulating oil 10 from flowing when the oil pump P is in operation. With this purchase, forced circulation cooling is performed by operating the oil feed pump P when the oil-immersed transformer is at full load, and natural circulation cooling is performed by stopping the oil feed pump when it is half loaded. That is,
Insulating oil 10 cooled by cooler 9 during forced circulation cooling
is sent from the lower pipe 7 into the common oil pipe 4 by the oil pump P as shown by the solid line arrow, and circulates from below the winding 3 to above and then back to the above pipe from the upper part of the oil tank 1, Further, during natural circulation cooling when the oil feed pump P is stopped, the insulating oil 10 enters the common oil feed 4 via the side pipe 11 as shown by the broken line arrow, and thereafter circulates in the same manner as the former.
On the other hand, the winding 3 consisting of a plurality of coils 3A is formed with a horizontal oil pipe 14 interposed between each coil 3A, as shown in FIG. Instead of forming inner and outer vertical oil passages 12 and 15 of predetermined dimensions, which are the passages for the insulating oil 10, by placing the inner and outer vertical oil passages 12 and 15 between each of the plurality of coils 3A for good cooling of the winding 3. Flow plates 13 are arranged to alternately close the oil passages 12 and 15, thereby preventing the insulating oil rising up the vertical oil passage 12 or 15 as shown by the solid and broken line arrows during both forced and natural circulation cooling. Each horizontal oilway 14 is made to flow to the opposite vertical oilway, and the inner and outer vertical oilways 12
.
This is the opposite of that between six adjacent folding plates, and this is configured to be repeated alternately in sequence.

Each horizontal oilway 14 between the plurality of coils 3A in each flow section
The flow velocity distribution of the insulating oil 10 in is as shown in FIG.

That is, when forced circulation cooling is used to operate the oil pump P, as shown by the solid line, the flow velocity in the horizontal axis 14 located near the bottom of the folding plate 13 that closes the vertical oil passage 12 or 15 is the highest. The further away from this point, the slower the flow rate becomes, and in the horizontal oil channel near the inlet of the insulating oil, the flow rate becomes extremely slow. On the other hand, in the case of natural circulation cooling in which the oil feed pump P is stopped, as shown by the broken line, a horizontal The flow velocity in the oil pipe 14 is the slowest, becomes faster as you move further away from this, and reaches the maximum flow velocity on the insulating oil inlet side. Therefore, during forced circulation cooling, the coils located above each folded flow section are cooled better than those located below, and conversely, during natural circulation cooling, the coils located above each folded flow section are cooled better than those located below. Since the lower coils in the section are cooled better than the upper ones, in either case there is a problem in that the cooling becomes uneven and the cooling efficiency of the windings decreases. For this reason, attempts have been made to uniformly cool each coil and improve cooling efficiency by both forced and natural circulation cooling by improving the structure of the windings, but they have not been able to achieve sufficient effects. . For example, in order to improve the flow velocity distribution of forced circulation cooling, the dimensions of the horizontal oil passage between each coil 3A in each folded flow section are narrowed from below the winding 3 to above to reduce the pipe resistance. When configured to adjust, as shown by the solid line in FIG. 4, the flow velocity distribution in forced circulation cooling is improved and almost uniform cooling can be achieved, but in natural circulation cooling, the unevenness of the flow velocity distribution is further exacerbated. On the other hand, if we mainly improve the flow velocity distribution of natural circulation cooling,
Forced circulation cooling results in a more non-uniform flow velocity distribution. That is, it has been extremely difficult to purchase windings that are sufficiently satisfactory for both forced and natural circulation cooling methods. The purpose of the oil-immersed transformer cooling method of the present invention is to effectively cool a winding made up of a plurality of disc-shaped or spiral-shaped coils in both forced and natural circulation cooling cases. The purpose is to improve cooling efficiency.

In order to achieve the above object, in the cooling method of the present invention, a plurality of coils are stacked via horizontal oil passages, and inner and outer vertical oil passages are provided between the inner and outer insulating cylinders. The inner and outer vertical oil passages of each coil are alternately closed with folding members to form multiple folded sections. When cooling the winding by forced or natural circulation cooling, the inner and outer vertical oil passages in the folded sections are The resistance of each conduit, including the oil pipe, is formed so that it decreases from the bottom of the winding to the top, and during forced circulation cooling using an oil pump, the insulating oil is routed from the cooler to the top of the oil tank, inside the winding, and into the winding. In addition to circulating insulating oil from the cooler to the lower part of the oil tank, inside the windings, and then to the upper part of the oil tank using the parallel side piping when cooling by natural circulation without using an oil pump, it is recommended to This is a characteristic feature.

Embodiments of the present invention will be sequentially described below with reference to FIGS. 5 to 10, in which portions that are the same as those of the prior art are denoted by the same reference numerals.

In the cooling method of the present invention, as shown in FIG. 5, the contents of a transformer consisting of an iron core and windings are housed in an oil tank 1 and insulating oil is sealed in the oil tank 1 as in the conventional case. For example, a cooler 9 is connected to the lower pipe 7, and an oil feed pump P is interposed in the lower pipe 7, and a side pipe 11 is provided in parallel thereto.

At this time, in the present invention, the winding 3 is purchased as described later, and at the same time, when the oil pump P is operated for forced circulation cooling, the insulating oil is transferred from the cooler 9 to the upper part of the oil tank 1, inside the winding 3, as shown by the solid line arrow.
In the case of natural circulation cooling in which the oil is circulated in the order of the common oil pipe 4 at the bottom of the oil tank 1 and the oil feed pump P is stopped, the side pipe 11 is used.
The insulating oil is circulated from the cooler 9 to the lower part of the oil tank 1, inside the winding 3, and to the upper part of the oil tank 1 in this order as indicated by the broken line arrow. The winding 3 used in the cooling method of the present invention is, for example, as shown in FIG. The cylinders are stacked in the axial direction through the cylinders 5 and 6, and are arranged so as to form internal and external vertical oil passages 12 and 15 between the internal and external insulating cylinders 5 and 6.

This winding 3 is constructed by providing folding members 13 made of an insulator or the like for alternately closing the inner and outer vertical oil passages 12, 14 for each of the plurality of coils 3A to create a plurality of folding sections. For example, the height dimension t of each horizontal oilway in each turning section is made larger from the lower part of the winding to the upper part, so that each horizontal oilway including the inner and outer vertical oilways 12 and 15 14 conduit resistance, that is, the conduit resistance from one vertical oil pipe on the insulating oil inlet side of the flow section to the horizontal oil pipe to the outgoing mark of the other vertical oil pipe is configured to decrease in order. . As a result, the oil pump can be operated to forcefully circulate the insulating oil from the upper part of the winding to the lower part as shown by the solid arrow, or the oil pump can be stopped and the oil can be circulated from the lower part of the winding to the upper part as shown by the dashed arrow. When natural circulation is carried out toward the diversion section, the resistance of the pipes including the horizontal oil pipe located at the lower part of the diversion section is greater than that of the upper part, so the insulating oil passing through this part is restricted. As shown by the solid line and the broken line in , the flow velocity of the insulating oil in each horizontal oilway can be adjusted to be approximately the same in both cases of forced and natural circulation cooling, respectively.

Therefore, since each coil 3A within the folded flow section is cooled almost uniformly, it is possible to significantly improve the cooling efficiency of the winding 3. In the practical example of the present invention shown in FIG. 8, the oil pump P is interposed upwardly, contrary to the example shown in FIG.
The only difference is that the windings 1 and 3 are arranged in parallel, and the same effect can be achieved by forming the winding 3 as described above and circulating insulating oil as described above during forced and natural circulation cooling. It is. With this arrangement of the oil pump P, when applied to a transformer that uses a type that communicates with the atmosphere as a conservator that compensates for the expansion and contraction of the insulating oil 10, the condition that the suction side of the oil pump P becomes almost atmospheric pressure is created. is satisfied, the pressure inside the winding 3 becomes higher than the atmospheric pressure throughout the entire area during forced circulation cooling, so there is no risk of gas separating from the insulating oil 10 due to a decrease in static pressure and causing an insulation breakdown accident. There is. In each fold section of winding 3,
In order to adjust the pipe resistance of each horizontal oil pipe 14 including the inner and outer vertical oil pipes 12 and 15, as shown in FIG. An inner or outer vertical oil pipe 1 facing the outlet side of the insulating oil 10 during natural circulation cooling (inlet side during forced circulation cooling)
This can also be done by arranging the control member 16 made of an insulating material within the windings 2 and 15 such that the thickness decreases from below the windings 3 to the top, and the vertical oil passage gradually widens. . In this example, the control member 16 is divided into small pieces and arranged so as to face the coil 3A, but it is preferable to provide one in which the control member 16 is formed so as to be continuous from the bottom to the top of the vertical oil passage. Alternatively, the control member 16 can also be used as the folding member 13. Winding 3
Even when formed as shown in Fig. 9, the flow velocity in each horizontal oil pipe 14 within the flow pressure gap is distributed almost uniformly in both forced and natural circulation cooling as shown in Fig. 10. Therefore, each coil 3A (7) can be cooled well. By applying the method of cooling an oil-immersed transformer of the present invention, windings consisting of a plurality of disc-shaped or spiral-shaped coils can be cooled well whether by forced or natural circulation cooling. , can achieve the effect of significantly improving cooling efficiency.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a conventional oil-immersed transformer cooling method, Fig. 2 is a partial longitudinal sectional view showing the flow of insulating oil within the windings of a conventional oil-immersed transformer, and Fig. 3 is a schematic diagram showing a cooling method for a conventional oil-immersed transformer. Figure 4 is a diagram showing the relationship between each horizontal oil passage in the diversion section of the winding and the flow velocity of the oil. Figure 5 is a schematic diagram showing an example of the cooling method for an oil-immersed transformer according to the present invention, and Figure 6 is a diagram showing the relationship between the flow velocity of the insulating flow and the flow rate of the oil-immersed transformer according to the present invention. FIG. 7 is a diagram showing the relationship between the position of each horizontal oil pipe in the folded flow section of the winding shown in FIG. 6 and the flow velocity of insulating oil, and FIG. FIG. 9 is a schematic diagram showing another example of a method for cooling a transformer; FIG. 9 is a partial vertical sectional view showing the flow of insulating oil in the winding of another example of an oil-immersed transformer to which the present invention is applied; FIG. 10 9 is a diagram showing the relationship between the position of each horizontal oilway in the folded section of the winding shown in FIG. 9 and the flow velocity of insulating oil. 1...Oil tank, 2-...Iron core, 3-...
...Winding, 3A...Coil, 5,6...
・Inner and outer insulation tubes, 7, 8...Lower and upper piping, 9...Cooler, 10...-Insulating oil, 11...--Semi-1j path Piping, 12, 15...
...Inner and outer vertical oil pipes, 13...Folding member, 14...Horizontal oil pipe, 16...Control member, P...Oil sending pump.

Claims (1)

[Claims] 1. An iron core and a winding, which are the contents of a transformer, are housed in an oil tank, and insulating oil is sealed therein, and the winding is formed by stacking a plurality of coils through horizontal oil pipes. A plurality of folded flow sections are provided by providing folding members arranged to provide inner and outer vertical oil passages between inner and outer insulating cylinders and alternately closing the inner and outer vertical oil passages for each of the plurality of coils. A cooler is connected to the oil tank by upper and lower piping, and an oil feed pump is provided in either one of the upper and lower piping, and a side that is parallel to the feed pump and opens when the operation is stopped. In the case where the winding is cooled by forced or natural circulation cooling, the winding is configured to reduce the pipe resistance of each horizontal oil pipe including the inner and outer vertical oil pipes in each turning section below the winding. When the oil pump is operated for forced circulation cooling, the insulating oil is circulated from the cooler to the upper part of the oil tank, inside the winding, and to the lower part of the oil tank, and the oil pump is stopped. The above-mentioned side pipe is used for natural circulation cooling,
A method for cooling an oil-immersed transformer, characterized by circulating insulating oil from a cooler to the lower part of the oil tank, inside the windings, and then to the upper part of the oil tank. 2. The pipe resistance of each horizontal oilway including the inner and outer vertical oilways of the diversion section is adjusted by increasing the dimensions of each horizontal oilway from the bottom of the winding to the top. A method for cooling an oil-immersed transformer according to claim 1. 3 The pipe resistance of each horizontal oil pipe including the inner and outer vertical oil pipes in the folded flow section is such that the thickness of the control member decreases from the bottom of the winding to the top when it is cooled by natural circulation. 2. A method for cooling an oil-immersed transformer according to claim 1, wherein the cooling method is carried out by disposing it in an inner or outer vertical oil passage.