JPS6161690B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transformer having two rated voltages on the primary side or the secondary side, and particularly to a transformer in which the rated voltages can be switched when stepping up or stepping down the voltage of the system.

Due to the operation of the power transmission system, for example, the initial voltage was 275kV.
Operation starts at the transmission voltage (hereinafter referred to as operation start),
There are plans to boost the voltage to 550kV in a few years.
In this case, if a 275kV transformer is installed initially, a 550/275kV autotransformer will be required to step up the voltage to 550kV.

Therefore, with this method, it is necessary to secure the installation space for the autotransformer in advance, and by adding the autotransformer, compared to a normal 550kV transformer consisting of a low-voltage winding and a high-voltage winding, To secure a voltage of 550kV, the equivalent capacity is more than 1.5 times larger, the loss is 1.6 times larger, and the impedance is also 1.8 times larger.
In addition, in power plant transformers, the high voltage secondary side is directly connected to a cable or GIS (gas insulated switchgear), so when boosting the voltage, the cable or GIS
The costs involved will be enormous.

An improvement plan for this is to install two transformers with a capacity of 1/2, and at 275kV, connect the low voltage windings 3 and 4 of the two transformers 1 and 2 in parallel, as shown in Figure 1a. In addition, there is a method in which the high voltage windings 5 and 6 are connected in parallel, and when the voltage is 550 kV, the high voltage windings 5 and 6 are connected in series as shown in FIG. In addition, in Fig. 1, 7 and 8 are iron cores,
N is a neutral point terminal.

However, with this method, in terms of equivalent capacity,
It is the same as a 550kV transformer, but because it uses two transformers, it is more expensive and the loss is 1.3 times more. Moreover, it is difficult to change connections and requires a large amount of installation space.

There is also a plan to store the contents of these two transformers in the same tank, but with this plan, it is necessary to drain the oil and change the internal connections on-site when boosting the voltage, which poses reliability problems. .

Furthermore, as an improvement to these, the present inventor has recently proposed a transformer as shown in FIG. 2 (Japanese Patent Application No. 116375/1982).

This transformer has a low voltage side of 1 like a normal transformer.
In contrast, the high-voltage side is configured with two windings, an intermediate-voltage winding 10 and a high-voltage winding 11, into a single-turn winding. Note that 12 is an iron core. These windings 9, 10, 11 and iron core 12 are housed in an oil tank 13.

Both terminals 9A and 9B of the low voltage winding 9 are drawn out of the tank 13 through air pushing. A neutral point terminal 10N is connected from one end of the medium voltage winding 10, a common medium voltage terminal 14 is connected from the connection between the other end and the shorted ends of the high voltage winding 11, and a common medium voltage terminal 14 is connected to the high voltage winding 10. High voltage terminals 11A are drawn out of the tank 13 from the center of the tank 11 through air bushings.

Initially, medium voltage (lower rated voltage e.g.
275kV), as shown in Figure 2 a.
The medium voltage terminal 14 and the overhead wire 15 are connected, and the high voltage terminal 11A of the high voltage winding 11 through which current is not flowing is connected to the lightning arrester 1.
Used by grounding via 6. After that, when switching to a high voltage (higher rated voltage, e.g. 550 kV), remove the lightning arrester 16 and connect the overhead line 15 from the medium voltage terminal 14 to the high voltage terminal 11A, as shown in Figure 2b.
All you have to do is change the connection.

In this way, one transformer can handle two rated voltages, so it requires less installation space and can easily switch voltages. Especially when changing the voltage, there is no need to make any changes to the inside of the tank, so there is no reduction in reliability. Further, the increase in equivalent capacity and loss is also relatively small. However, even though the increase in equivalent capacity and loss is small, compared to a normal 550kV transformer, the equivalent capacity increases by 25% and the loss increases by 10%. A lightning arrester is required to suppress the voltage transfer to the high voltage terminal in the event of a lightning impulse entering the terminal.
In addition, the leakage magnetic flux density is determined by the solid line MV and the chain line HV in Figure 3 when using medium voltage and high voltage.
As a result, the impedance when using high voltage is 1.5 times that when using medium voltage, resulting in a problem of lowering the stability of the system.

The purpose of the present invention is to solve the above-mentioned problems and to
The unit has two rated voltages, and the equivalent capacity does not change.
To provide a transformer in which the increase in loss is further reduced, impedance does not change when both rated voltages are used, and the voltage can be switched without draining the oil in the tank of the transformer main body.

To achieve this objective, the present invention provides a winding having two rated voltages, at least one of which is higher than or equal to ultra-high voltage, a first winding to which a lower voltage is applied and a second winding to which a higher voltage is applied. and the first and second windings are arranged on both sides of the winding having one rated voltage, sandwiching the winding on the side having one rated voltage,
and the winding start and winding end terminals of the first and second windings are respectively drawn out of the transformer main body tank, and when the lower rated voltage is applied, the first and second windings are connected in parallel, It is characterized in that the first and second windings are connected in series when a higher rated voltage is applied.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 4 shows an embodiment of the present invention.

In the transformer of this embodiment, a medium voltage winding 10 and a high voltage winding 11 constituting the high voltage side are arranged on the inside and outside of the low voltage winding 9, respectively, with the medium voltage winding 10 sandwiching the low voltage winding 9.
Each of these windings 9 to 11 and the iron core 12 are housed in an oil tank 13.

Both terminals 9A and 9B of the low voltage winding 9 are drawn out of the tank 13 through an air bushing, and both terminals 10A and 10N of the medium voltage winding 10 and the high voltage winding 11
Both terminals 11A and 11B are also drawn out of the tank 13 through air bushings.

When this transformer is initially operated at a medium voltage (lower rated voltage, e.g. 275kV), one terminal 10A of the medium voltage winding 10 and one terminal of the high voltage winding 11 are connected as shown in FIG. 4a. 11A, connect these to the overhead wire 15, and also connect the medium voltage winding 1
0, that is, the neutral point terminal 10N, and the other terminal 11B of the high voltage winding 11 are connected. In other words, the medium voltage winding 1 on the high voltage side has two rated voltages.
0 and high voltage winding 11 are connected in parallel. Then the high voltage (higher rated voltage e.g.
550kV), as shown in Figure 4b,
One terminal 10A of the medium voltage winding 10 and the high voltage winding 11
connection with one terminal 11A of , and medium voltage winding 1
0 neutral point terminal 10N and the other terminal 11B of the high voltage winding 11 are disconnected, and one terminal 10A of the medium voltage winding 10 and the other terminal 11B of the high voltage winding 11 are connected. 10 and the high voltage winding 11 may be connected in series.

In this way, one transformer of this embodiment has two
Since it can accommodate two rated voltages, it requires less installation space and can be easily switched between voltages. Especially when changing the voltage, there is no need to make any changes to the inside of the tank, so there is no reduction in reliability. Furthermore, the equivalent capacity is the same as that of a normal 550kV transformer, and there is no transition voltage to the high-voltage terminal mentioned above, so there is no need for a lightning arrester. Furthermore, as shown in Figure 5, the leakage magnetic flux density is half of that shown in Figure 3, and there is no difference between using medium voltage and high voltage, so there is no change in impedance. In addition to maintaining good system stability, stray loss is reduced by halving leakage magnetic flux density, and loss can be reduced by that amount.

FIG. 6 shows another embodiment of the invention.

This embodiment differs from the embodiment shown in FIG. Both terminals 1 of wire 11
1A and 11B are drawn out using an oil-immersed wall bushing or an oil-immersed terminal board, and one terminal 1 of the high-voltage winding 11 is installed in this oil-immersed junction box 17.
Cable head 19 for connecting cable 18 connected to 1A and neutral point terminal 10N of medium voltage winding 10
A neutral point bushing 20 connected to the neutral point bushing 20 is installed.

As in FIG. 4, a indicates when medium voltage is used, and b indicates when high voltage is used. When switching from medium voltage to high voltage, drain the oil in the oil-filled junction box 17, switch the connections from a to b, and then switch the junction box 17 again.
Fill the inside with oil. The rest of the structure is the same as the embodiment shown in FIG. 4, so the same parts are given the same reference numerals and detailed explanations will be omitted.

FIG. 7 shows yet another embodiment of the invention. This embodiment is an example in which the low voltage side has two rated voltages.

In the transformer of this embodiment, the high voltage side consists of one high voltage winding 21 like a normal transformer, while the low voltage side consists of two medium voltage windings 22 and a low voltage winding 23.
The medium-voltage winding 22 and the low-voltage winding 23 are arranged on the outside and inside of the high-voltage winding 21, sandwiching the high-voltage winding 21, respectively. In addition, 24 is a stable winding, and 25 is an iron core. Each of these windings 21
24 and the iron core 25 are housed in an oil tank 26. A high-pressure oil-filled connection box 27 and a low-pressure oil-filled connection box 28 are provided on the outside of the oil-filled tank 26.

One terminal of the high voltage winding 21, that is, the high voltage terminal 2
1A is drawn out into the high-pressure oil-filled connection box 27 through an oil-immersed wall bushing or an oil-immersed terminal board,
It is also connected within the junction box 27 to a cable head 30 on the high voltage side which is connected to the cable 29. Further, the other terminal of the high-voltage winding 21, that is, the neutral point terminal 21N, is drawn out of the tank 26 through an air bushing. Both terminals 22A, 22B of the medium voltage winding 22 and both terminals 23 of the low voltage winding 23
A, 23N are connected to the low pressure oil-filled connection box 28 through the oil-immersed wall bushing or oil-immersed terminal board, respectively.
Among these, medium voltage winding 22
One terminal 22A of the cable 31 and the neutral point terminal 23N of the low voltage winding 23 are connected to the cable 31
The cable head 32 and the neutral bushing 33 on the low voltage side are respectively connected to the low voltage side cable head 32 and the neutral point bushing 33 connected to the low voltage side.

When this transformer is initially operated at a low voltage (lower rated voltage), one terminal 22A of the medium voltage winding 22 and one terminal 23A of the low voltage winding 23 are connected as shown in Figure 7a. At the same time, the other terminal 22B of the medium voltage winding 22 and the neutral point terminal 23N of the low voltage winding 23 are connected, and the medium voltage winding 22 and low voltage winding 23 on the low voltage side having two rated voltages are connected in parallel. and use it. After that, when switching the low voltage side to medium voltage (higher rated voltage), drain the oil from the low voltage side oil-filled junction box 28 and connect the terminal 22 as shown in Figure b.
After disconnecting A and the terminal 23A and disconnecting the terminal 22B and the terminal 23N, and connecting the terminal 22B and the terminal 23A, the connection box 28 is filled with oil again.

In this embodiment, the high voltage terminal 21A does not necessarily require a cable or GIS lead-out. Further, depending on the values of the low voltage and medium voltage, the low voltage winding 23 can be placed outside the high voltage winding 21 and the medium voltage winding 22 can be placed inside the high voltage winding 21 in consideration of losses.

In each of the above examples, the two rated constant pressures are
Although the explanation was given using 275KV and 550KV as examples, it is not necessarily limited to switching between ultra-high voltage and ultra-super high voltage, and when one of the two rated voltages is higher than ultra-high voltage, for example, 187KV / 274KV. In that case,
It is also applicable to Further, in each of the above embodiments, the high voltage winding is a cylindrical winding, but depending on the voltage, it may also be a disk winding arranged in parallel above and below.

As explained above, according to the present invention, one transformer can be used to switch between two rated voltages, thereby reducing installation space, reducing loss and equivalent capacity, and switching voltages. It is possible to shorten the outage period, improve transition voltage, and improve system stability and reliability.

[Brief explanation of the drawing]

Figures 1a and b are configuration diagrams of a conventional transformer device corresponding to two rated voltages when each rated voltage is used, and Figures 2a and b are configurations of the transformer according to the existing proposal when each rated voltage is used. 3 is an explanatory diagram showing the leakage magnetic flux density of the transformer shown in FIG. 2, FIGS. 4a and 4b are configuration diagrams of the transformer according to an embodiment of the present invention when each rated voltage is used, FIG. 5 is an explanatory diagram showing the leakage magnetic flux density of the transformer shown in FIG. 4, and FIGS. 6 a, b and 7 a, b are each rating of the transformer according to other embodiments of the present invention. FIG. 3 is a configuration diagram when voltage is used. 9,23...Low voltage winding, 10,22...Medium voltage winding, 11,21...High voltage winding, 13...Transformer main tank, 17...Oil-filled junction box, 27...High voltage side oil filler Connection box, 28...Low pressure side oil filled connection box.

Claims (1)

[Claims] 1. In a transformer in which either the primary side or the secondary side has two rated voltages, at least one of which is an ultra-high voltage or higher, the side with the two rated voltages is replaced with the lower one. It consists of a first winding to which a rated voltage is applied and a second winding to which a higher rated voltage is applied, and the first and second windings are connected to a side having one rated voltage. The first and second winding terminals are arranged on both sides of the winding, and the winding start and winding end terminals of the first and second windings are respectively drawn out of the main tank of the transformer. 1. A transformer characterized in that first and second windings are connected in parallel, and when a higher rated voltage is applied, the first and second windings are connected in series. 2. In claim 1, the side having the two rated voltages is a voltage side, and the side having the two rated voltages is a voltage side, and the side having the two rated voltages is a voltage side, and
A transformer characterized in that the winding is a medium voltage winding, and the second winding is a high voltage winding. 3 In claim 1, the side having the two rated voltages is a low voltage side, and the side having the two rated voltages is a low voltage side, and the side having the two rated voltages is a low voltage side,
A transformer characterized in that the winding is a low voltage winding, and the second winding is a medium voltage winding. 4. In claim 1, the winding start and winding end terminals of the first and second windings are drawn out into an oil-filled junction box provided outside the transformer main body tank. A transformer featuring: