JPH0212005B2 - - 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 greater, and the loss is also 1.6 times greater. In addition, in power plant transformers, the high voltage secondary side is directly connected to a cable or GIS (gas insulated switchgear), so modification when boosting the voltage involves modifying the cable or GIS, which can be extremely costly.

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 550kV, but because it uses two transformers, it is more expensive and the loss is more than 1.3 times higher. 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. .

The purpose of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a transformer that has two rated voltages in one unit, has a small increase in equivalent capacity and loss, and can switch voltages without draining the oil in the tank. It is to provide the equipment.

To achieve this objective, the present invention provides: on the primary side,
In a transformer in which one of the secondary sides has two rated voltages, the side having the two rated voltages is connected to a first winding to which the lower rated voltage is applied, and this first winding. When connected in series, a higher rated voltage is applied to the winding, and a second winding is arranged concentrically and separated from the first winding. When a terminal is provided to draw out each winding end of the second winding independently to the outside of the tank, and when used at the lower rated voltage of the two rated voltages, at least one of the terminals to draw out the second winding end is provided. It is characterized by being configured so that one side is grounded.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 shows an embodiment of the invention.

In the transformer of this embodiment, the low voltage side is composed of one low voltage winding 9 like a normal transformer, whereas the high voltage side is composed of two windings, a medium voltage winding 10 and a high voltage winding 11. ing. Note that 12 is an iron core. These windings 9, 10, 11 and iron core 12
is stored in the oil tank 13.

Both terminals 9A and 9B of the low voltage winding 9 are led out of the tank 13 through an air bushing. One terminal of the medium voltage winding 10 serves as a neutral point terminal 10N, and the other terminal serves as a medium voltage terminal 10A, each of which is drawn out of the tank 13 through an air bushing. Both ends of the high-voltage winding 11 are short-circuited, and a medium-voltage terminal 11A is drawn out from there, and a high-voltage terminal 11B is drawn out from the center of the high-voltage winding through an air bushing, respectively, to the outside of the tank 13.

When this transformer is initially operated at medium voltage (lower rated voltage, e.g. 275kV), it should be used as shown in Figure 2a.
Connect the medium voltage terminal 10A of the medium voltage winding 10 and the overhead wire 14, and connect the high voltage winding 11 to which no current flows.
Use by grounding the medium voltage terminal 11A. after that,
When switching to a high voltage (higher rated voltage, e.g. 550kV), as shown in Figure 2b, the high voltage winding 11
While connecting the high voltage terminal 11B and the overhead line 14,
The medium voltage terminal 10A of the medium voltage winding 10 and the medium voltage terminal 11A of the high voltage winding 11 may be connected to each other.

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. In addition, the equivalent capacity is also
Compared to a 550kV transformer, the increase can be kept to only 25%, and the loss can also be kept to within 10%. Also, when using medium voltage voltage, medium voltage terminal 1
The high voltage winding 11 also responds to the transition voltage to the high voltage terminal 11B when an impulse enters 0A.
Since the medium voltage terminal 11A is grounded, the transition voltage to the high voltage terminal 11B can be suppressed to about 1.5 times the voltage applied to the medium voltage terminal 10A. value) and does not require any special measures.

If the space is narrow, install an oil-filled junction box outside the tank and erect the intermediate voltage terminal's air bushing there, and place the medium voltage terminal of the medium voltage winding and the medium voltage terminal of the high voltage winding in the oil. It may be drawn out into the oil-filled junction box using wall bushings or the like, and the medium voltage terminals may be switched and connected within the junction box.

FIG. 3 shows another embodiment of the invention.

This embodiment differs from the embodiment shown in FIG. 2 in that an oil-filled junction box 15 is provided outside the tank 13, and inside this oil-filled junction box 15, the medium voltage terminal 10A of the medium voltage winding 10 and the high voltage winding 11 medium voltage terminal 11A
The high voltage terminal 11B is drawn out using an oil-immersed wall bushing or an oil-immersed terminal board, and the cable head 16 is installed in the oil-immersed junction box 15.
is installed. Similar to Figure 2, a
b is when medium voltage is used, and b is when high voltage is used.
When switching from a medium voltage to a high voltage, the oil in the oil-filled junction box 15 is drained, the connections are switched from a to b, and then the junction box 15 is filled with oil again.
The rest of the structure is the same as the embodiment shown in FIG. 2, so the same parts are given the same reference numerals and detailed explanations will be omitted.

FIG. 4 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 17 like a normal transformer, whereas the low voltage side consists of two medium voltage windings 18 and low voltage windings 19.
It consists of two windings. Note that 20 is a stable winding, and 21 is an iron core. These windings 17,1
8, 19, 20 and the iron core 21 are housed in an oil tank 22. A high-pressure oil-filled connection box 23 and a low-pressure oil-filled connection box 24 are provided on the outside of the oil-filled tank 22.

A high-voltage terminal 17A is drawn out from the center of the high-voltage winding 17 through an oil-immersed wall bushing or an oil-immersed terminal plate into a high-voltage oil-filled junction box 23, and this high-voltage terminal 17A is connected to a cable head on the high-voltage side within the junction box 23. 25. Also, both ends of the high voltage winding 17 are short-circuited, and from there, the neutral point terminal 17
N is drawn out of the tank 22 through the air bushing. One terminal of the medium voltage winding 18 serves as a medium voltage terminal 18A, and the other terminal serves as a low voltage terminal 18B, each of which is drawn out into the low voltage side oil-filled connection box 24 through a wall bushing or the like submerged in oil.
One terminal of the low-voltage winding 19 is led out as a low-voltage terminal 19A into the low-voltage side oil-filled junction box 24 through an oil-immersed wall bushing, etc., and the other terminal is led out of the tank 22 as a neutral point terminal 19N through an air bushing, etc. It is being pulled out to. Low pressure oil-filled connection box 24
A cable head 26 on the low voltage side is installed inside.

When this transformer is initially operated at a low voltage (lower rated voltage), the low voltage terminal 18B of the medium voltage winding 18 is grounded, and the low voltage terminal 19A of the low voltage winding 19 is grounded, as shown in Figure 4a. is used by connecting it to the cable head 26. 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 24 and connect the medium voltage terminal 18A of the medium voltage winding 18 as shown in Figure b. cable head 26
and the low voltage terminal 18 of the medium voltage winding 18
After connecting B and the low voltage terminal 19A of the low voltage winding 19, the connection box 24 is filled with oil.

In this embodiment, the high voltage terminal 17A 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 19 may be placed outside the medium voltage winding 18 in consideration of loss.

In each of the above embodiments, the high-voltage windings are arranged in parallel above and below, but the present invention is also applicable to the case where they are wound through.
Furthermore, a tertiary winding used for power supply within the substation can also be provided inside the low voltage winding.

As explained above, according to the present invention, one transformer can be used to switch between two rated voltages, so installation space can be reduced, and losses and equivalent capacity can be reduced, as well as voltage switching. It is possible to shorten downtime and improve reliability.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional means corresponding to two rated voltages, where a is when the lower rated voltage is used;
b is when using the higher rated voltage, Figures 2 to 4
The figures are block diagrams showing embodiments of the present invention, and a
b is when the lower rated voltage is used, and b is when the higher rated voltage is used. 9...Low voltage winding, 9A, 9B...Low voltage terminal, 1
0...Medium voltage winding, 10A...Medium voltage terminal, 10N...
...neutral point terminal, 11...high voltage winding, 11A...medium voltage terminal, 11B...high voltage terminal, 13...tank,
15...Oil filled connection box, 17...High voltage winding, 17A
...High voltage terminal, 17N...Neutral point terminal, 18...
Medium voltage winding, 18A... medium voltage terminal, 18B... low voltage terminal, 19... low voltage winding, 19A... low voltage terminal,
19N...neutral point terminal, 22...tank, 23...
...High pressure side oil-filled connection box, 24...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, the side having the two rated voltages is connected to the first side to which the lower voltage is applied.
and a second winding to which a higher rated voltage is applied when connected in series to the first winding, and which is arranged concentrically and separated from the first winding. In addition, terminals are provided to draw out each winding end of the first and second windings to the outside of the tank independently, and when used at the lower of the two rated voltages, the above-mentioned A transformer characterized in that at least one of the terminals from which the second winding end is drawn out is grounded. 2. In claim 1, the side having the two rated voltages is a high voltage side, the first winding is a medium voltage winding having a neutral point terminal and a medium voltage terminal, and the second winding is a medium voltage winding having a neutral point terminal and a medium voltage terminal. A transformer characterized in that the winding is a high voltage winding having a medium voltage terminal and a high voltage terminal. 3. In claim 2, the medium voltage terminal of the medium voltage winding and the medium voltage terminal and high voltage terminal of the high voltage winding are drawn out into an oil-filled junction box provided outside the tank. A transformer characterized by: 4. In claim 1, the side having the two rated voltages is a low voltage side, the first winding is a low voltage winding having a neutral point terminal and a low voltage terminal, and the second winding is a low voltage winding having a neutral point terminal and a low voltage terminal. A transformer characterized in that the winding is a medium voltage winding having a low voltage terminal and a medium voltage terminal. 5. In claim 2, the low voltage terminal of the low voltage winding and the low voltage terminal and medium voltage terminal of the medium voltage winding are drawn out into an oil-filled junction box provided outside the tank. A transformer featuring: