JPH0531283B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to an on-load tap changeover, and more particularly to an improvement in an oil purifying pipe that prevents a drop in the oil level in the changeover switch oil tank. [Technical background of the invention and its problems] An on-load tap changer is a device that switches taps without interrupting the energization of a transformer. It consists of a switching switch that bridges between the taps to be selected via a current limiting resistor and then switches to the desired tap, and a drive device that drives this.In the case of a type with a built-in transformer, the tap selector and switching switch are connected to a transformer. built into the tank. Since the insulating oil of the on-load tap changer is contaminated by carbon generated by arcing when current is switched on and off, a device is provided to purify the contaminated oil. Moreover, this oil purification is performed while the transformer is energized. As shown in FIG. 6, such a conventional on-load tap changer has a purifying oil pipe 4 made of an insulating material upright from the bottom of the changeover switch oil tank 1 that houses the changeover switch 2 to its head. to the outside,
It is connected to an oil purifier 2 via a pipe 8 to purify the carbon-contaminated oil that accumulates at the bottom of the switching switch oil tank 1. The insulating oil 1a that has passed through the oil purifier 9 and has been purified is again returned to the switching switch oil tank 1 via a pipe 10 for circulation and purification. Note that a tap selector 3 is provided below the switching switch oil tank 1, and a conservator (not shown) is provided above the switching switch oil tank 1. And switching switch oil tank 1
The tap selector 3 is housed in a transformer tank 5, and the transformer tank 5 is filled with insulating oil 5a. As shown in such a circulation pipe, the insulating oil 1a in the switching switch oil tank 1 is completely separated from the insulating oil 5a in the transformer tank 5. In addition, if an oil leakage accident occurs in this external piping system or oil purifier, if the oil leakage location is lower than the switching switch oil tank 1, the insulation inside the switching switch oil tank 1 will be damaged due to the siphon phenomenon. Oil will be sucked out. Furthermore, if the oil purifier 9 is operated, oil will rapidly flow out due to the suction force of the oil feed pump of the oil purifier 9, regardless of the head difference between the oil leak location and the switching switch oil tank 1. become. Furthermore, if the tap changer continues to be energized during load without insulating oil in the changeover switch oil tank 1, dielectric breakdown will occur in the changeover switch oil tank 1, and it will be impossible to switch the taps. be. For this reason, in the event of the above-mentioned accident, an oil level gauge (not shown) provided in the conservator usually issues an alarm and the operation of the transformer is stopped. However, there is a problem described below.
In other words, even if an accident like the one described above occurs at a transformer in an unmanned substation located in a remote location, it is difficult to quickly respond to the accident. Furthermore, some of the transformers that supply power to hospitals and the like may cause a great deal of trouble to the power demand side if the transformer stops operating. Therefore, even if oil leaks from the oil piping system or the oil purifier 9, the insulating oil in the switching switch oil tank 1 will not be sucked out to the outside, allowing energization and tap switching to continue. It is necessary to prevent the oil level in the switching switch oil tank 1 from dropping so that the operation does not stop. [Object of the invention] The present invention has been made in consideration of the above points, and
The purpose of this is to prevent the oil level in the switching switch oil tank from dropping even if oil leaks from the external oil piping system or oil purifier, and to enable normal energization and tap switching. An object of the present invention is to provide an on-load tap changer. [Summary of the Invention] According to the present invention, in order to achieve the above object,
A small hole is drilled near the upper bend of the clean oil pipe installed in the oil tank of the switching switch, and the small hole is positioned so that the parts of the switching switch that are insulated in oil are not exposed. This feature prevents a drop in the oil level and enables normal energization and tap switching. Further, it is preferable that the area of the small hole is approximately 8% to 20% of the area of the oil suction port of the oil purifying pipe. [Embodiment of the Invention] An embodiment of the on-load tap changer of the present invention will be described below with reference to FIGS. 1 to 5 and Tables 1 and 2. The same parts as in FIG. 6 are given the same reference numerals. A switching switch 2 is housed in a switching switch oil tank (hereinafter abbreviated as oil tank) 1 and a tap selector 3 connected thereto is shown in a two-dot chain line, and is housed in a transformer tank 5. An oil purification pipe 6 made of an insulating member that opens at the bottom and has a curved portion at the top thereof is provided in the oil tank 1, and a small hole 7 is bored in the oil purification pipe 6 near the bent portion as will be described later. This oil purification pipe 6 is connected to piping 8, and this piping 8
A valve 8a is attached to an oil purifier 9 that penetrates the wall of the transformer tank 5 in an oil-tight manner and is installed outside the transformer tank 5.
connected via. The oil purifier 9 is also oil-tightly connected to the upper part of the transformer tank 5 via a valve 10a and piping 10. A conservator 13 is provided on the upper side surface of the oil tank 1 by a pipe 12 via a protection device 11 such as an oil flow relay. A valve 14a and a breather 14b are connected to this conservator 13 via piping 14. In addition, the inside of the transformer tank 5 is filled with insulating oil 5a, the inside of the oil tank 1 and the conservator 13 are filled with insulating oil 1a, and the oil tank The insulating oil 1a inside is circulated and purified. This insulating oil 1a is separate from the insulating oil 5a inside the transformer tank 5, and is used in the oil purifier 9.
An internal oil pump (not shown) circulates and purifies the insulating oil 1a as shown by the arrow. The oil purifying pipe 6 provided in the oil tank 1 will be explained with reference to FIG. 2. The oil purifying pipe 6 is made of an insulating material,
A small hole 7 is formed near the upper curved portion. At the lower end of the oil purifying pipe 6 is a suction port 15 that opens at the bottom of the oil tank 1.
It is connected to an external pipe 8 (see FIG. 1) by a bent pipe 16 having a flange 16a at its upper end. The lid part 17 is formed to be detachable from the oil tank 1, and the gear mechanism part 18 is attached to this lid plate 17.
will be provided. This gear mechanism section 18 consists of a bevel gear section 18a containing a built-in bevel gear (not shown) and a spur gear section 18b connected thereto.
8a is connected to a drive section (not shown). Further, the gear mechanism section 18 is connected to the switching switch 2 via a drive shaft 19 in the oil tank 1, and further
A tap selector 3 shown by a two-dot chain line is connected to the outside of the bottom plate 1b of the oil tank 1 by a mounting plate 20 and a coupling portion 21. Further, the switching switch 2 is fixed to the inner surface of the oil tank 1 via an insulating support member 22. Note that this oil tank 1 is filled with insulating oil 1a. FIG. 3 shows a small hole 7 in the oil purifying pipe 6 for draining oil from the oil tank 1 when the cover 17 is removed during inspection of the oil tank 1.
It shows a state in which a blind stopper 23 for sealing and a chain 23a connecting this are provided. The positions of the oil purifying pipe 6 and the small hole 7 are as shown in FIG.
In other words, it is provided within the range of dimension A between the top of the insulating support member 22 and the top of the insulating support member 22. Further, the hole area of the small hole 7 is selected to be approximately 8% to 20% of the opening area of the suction port 15 of the oil purifying pipe 6. The effects of the present invention configured as described above will be explained. If there is an oil leak in the external piping or oil purifier 9, the oil level from the conservator 13 will begin to drop, and when the oil in the conservator 13 runs out, the oil level in the oil tank 1 will then drop. . If the oil purifier 9 is being operated at this time, the oil level will drop even more rapidly. However, when the oil level drops to the height of the small hole 7, air from this small hole 7 passes through the upper part of the oil purification pipe 6 and enters the external piping, so the oil level no longer drops below the height of this small hole 7. do not have. Furthermore, the position or height of the small hole 7 is set at a height that prevents the oil level from dropping and does not expose the parts insulated in the oil above the oil level, so the insulation inside the oil tank 1 is maintained and the tap Switching and energization are possible. Therefore, there is no need to immediately stop the operation of the transformer. Next, when it is necessary to drain the oil in the oil tank 1 during inspection, prepare the blind plug 23 as an inspection tool as shown in FIG.
You can remove the oil inside. Also, attach the blind stopper 23 to the chain 2.
3a to the outside of the oil tank, the blind plug 23 is prevented from falling and the blind plug 23 is prevented from being forgotten to be removed. Furthermore, the area of the small hole 7 that prevents the oil level from dropping must be such that it can reliably prevent the oil level from dropping regardless of whether the oil purifier 9 is stopped or in operation. In this way, in order to determine the area of the small hole 7, the fourth
Using the experimental apparatus shown in the figure, the area of the small hole 7 that can prevent a drop in the oil level was investigated by changing the ratio of the area of the small hole 7 to the area of the oil suction port. The oil purifier 9 houses a filter 25 and an oil pump 26 inside,
One side of the filter 25 is connected to the upper side of the oil tank 28 by a pipe 27 having a valve 27a, and a pipe 29 having a valve 29a and a flow meter 29b is connected to one side of the oil pump 26 near the bottom of the oil tank 28. The vertical part of the pipe 29 in the oil tank 28, that is, the oil purifying pipe 6
A small hole 7 is formed near the upper curved part of the oil tank 28.
is filled with insulating oil 28a. Further, valves 30a and 30b are provided at a bend in the middle of the pipe 29, and connected to an oil sump 32 by a bypass pipe 31. The arrows in the figure indicate the direction of flow of the insulating oil. Table 1 shows the test results when oil was circulated as shown by the arrows using this test device, with the ratio of the area of the small hole 7 to the area of the suction port 15 being varied from 0.5% to 33%.

【table】

〔Effect of the invention〕

As explained above, according to the present invention, a small hole is provided in the upper part of the oil purifying pipe installed in the switching switch oil tank of the on-load tap changer, and the area of the small hole is Approximately 8% of the area of the lower end suction port
20%, and the position of this small hole is such that the oil-immersed insulation member of the switching switch is not exposed, so even if there is an oil leakage accident in the external oil piping system or oil purifier, the inside of the oil tank will remain intact. The oil does not leak outside and the oil purification effect is not lost, allowing for tap switching and energization as usual, and even if such an oil leakage accident occurs, transformer operation is immediately stopped. Because there is no need to do so, it provides a stable power supply for transformers in unmanned substations installed in remote areas where prompt accident response is difficult, and for transformers that cannot be stopped immediately due to power demand. It is possible to provide an on-load tap changer that has the following advantages:

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the on-load tap changer of the present invention, Figure 2 is an enlarged detailed cross-sectional view of the main parts of the present invention, and Figure 3 is a view of the lid opened when inspecting the oil tank in Figure 2. An enlarged sectional view showing the state, FIG. 4 is a configuration diagram of an experimental device for verifying the effects of the present invention, FIG. 5 is a characteristic diagram obtained by the experimental device shown in FIG. 4,
FIG. 6 is a sectional view of a conventional load tap switch. 1...Switching switch oil tank (abbreviated as oil tank), 2
...Switching switch, 3...Tap selector, 5...Transformer tank, 1a, 5a...Insulating oil, 6...Oil purification pipe, 7...Small hole, 8, 10...Piping, 9... Oil purifier, 15... Suction port, 22... Insulating support member.

Claims (1)

[Claims] 1. Clean the insulating oil that maintains the insulation between the switching switch of the on-load tap changer that switches the taps when the transformer is loaded, the switching switch, the switching switch oil tank that stores the insulating oil, and the insulating oil. An oil purifier that supplies oil, an oil purifier pipe that is piped from the bottom of the switching switch oil tank to the top, an oil suction side pipe that is connected to this oil purifier pipe and is piped to the oil purifier, and from the oil purifier. In the on-load tap switch, which is composed of an oil outlet side pipe connected to the switching switch oil tank, a small hole is provided in the upper part of the oil purifying pipe to prevent a drop in the level of insulating oil in the switching switch oil tank. The area of this small hole is approximately 8% to 20% of the area of the suction port at the lower end of the oil purifying pipe, and the position of this small hole is such that the submerged insulation member of the switching switch is not exposed. On-load tap changer.