JPH0244508Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a three-winding transformer that has a tertiary winding in which a current limiting reactor is connected in series, and that takes protection measures against transition voltage.

[Technical background of the invention and its problems]

In recent years, transformers used in power transmission systems have become increasingly high-voltage and large-capacity due to the increase in power demand, system operation, and economic efficiency. In response to these demands, three-winding transformers having three different independent windings for one phase: a high-voltage winding, a low-voltage winding, and a tertiary winding have been widely adopted.

This three-winding transformer is useful for grid connection, power factor adjustment,
Because it has good characteristics in suppressing high-frequency waves, it is excellent as a large-capacity transformer for power transmission systems, but the overall size of the device tends to increase. Therefore, this type of transformer is generally manufactured by dividing it into multiple unit transformers, transporting each unit transformer separately, and connecting each unit transformer to each other at the site, which is widely adopted. .

Therefore, in the transformer, in order to protect the system equipment, it is necessary to suppress the short-circuit current between the winding terminals to below the breaking capacity of the system. In the case of a three-winding transformer, the terminal voltage of the tertiary winding is 10 to 70KV, but the capacity of the circuit breaker applied to this is limited to 50KA at most, so the voltage between the tertiary winding terminals is It is necessary to suppress the short circuit current below the breaking capacity.
The value of this short-circuit current is determined by the impedance between the windings, especially the impedance between the low-voltage winding and the tertiary winding, but in order to suppress the short-circuit current, it is possible to further connect a current limiting reactor in series with the tertiary winding. It is being done.

FIG. 2 shows a schematic configuration of one phase of a conventional three-winding transformer. That is, there is a unit transformer 61 in which a tertiary winding 31, a low voltage winding 21, and a high voltage winding 11 are wound around an iron core 41 from the inside and housed in a tank 51, and a tertiary winding 32 and a low voltage winding are wound around an iron core 42 from the inside. It has a unit transformer 62 in which the line 22 and the high voltage winding 12 are wound and housed in the tank 52, and the high voltage windings 11 and 12 are connected in series to form a high voltage line side terminal U and a neutral point side terminal. O, low voltage winding 21,
22 are connected in parallel to form the low voltage line side terminal u and the neutral point side terminal θ, and the tertiary windings 31 and 32 are connected in series and one terminal A ₁ and the other are passed through the current limiting reactor 7 to form the terminal A ₂ . There is.

In order to configure a three-phase bank with three of these single-phase devices, the high voltage side can be connected in a Y-type connection, the low-voltage side can be connected in a Y-type connection, and the tertiary side can be connected in a Δ connection. By configuring each unit transformer 61, 62 by dividing and housing each winding in each unit transformer tank 51, 52 in this way, it is possible to transport each unit transformer 61, 62 separately. Transport size and weight can be reduced.

Therefore, a second winding having a rational winding arrangement structure
In the three-winding transformer shown in the figure, when a lightning impulse voltage is applied to one winding of the transformer, protective measures must be taken against the transition voltage induced in the other winding by electrostatic induction and electromagnetic induction. must be taught. In other words, in FIG. 2, when the voltage at the line terminal u of the low-voltage winding 21 is high, the tertiary windings 31 and 32 have a voltage that is determined by the inductance and capacitance between the windings in response to lightning impulses entering from the low-voltage line terminal u. A transition voltage occurs, which often exceeds the insulation level of the tertiary winding itself.

At this time, in the unit transformer 61, the end of the tertiary winding 31 facing the line terminal u of the low voltage winding 21 is the tertiary line terminal _a1 , which is a normal line terminal.
Since a ₁ and a ₂ are protected by surge absorbers z ₁ and z ₂ , their transition voltage can be suppressed to a low level. However, in the unit transformer 62, the low voltage winding 22
The end 32 of the tertiary winding 32 facing the line terminal u of
A has no device connected to the current limiting reactor 7 to limit the voltage, so a large transition voltage will occur. Therefore, the insulation dimension between the iron core 42 and the tertiary winding 32 needs to be greater than or equal to the insulation dimension determined from the insulation level of the terminal _a2 of the tertiary winding. If the insulation dimensions are increased in this manner, the diameter of the windings disposed on the outside increases accordingly, which increases the weight of the transformer and increases the loss generated, resulting in an uneconomical transformer.

[Purpose of invention]

The purpose of this invention is to sufficiently suppress the transition voltage at the end of the tertiary winding that occurs when lightning impulses enter the low-voltage winding, and to determine the dimensions between the iron core and the tertiary winding from the insulation level of the winding terminals. To provide a miniaturized three-winding transformer that can be manufactured without expanding beyond insulation dimensions.

[Summary of the idea]

The three-winding transformer according to the present invention connects two divided tertiary winding units in series via a current limiting reactor, so that the ends of the two tertiary winding units opposite to the line end of the low voltage winding The line terminal is protected by a surge absorber.

[Example of idea]

The present invention will be described below with reference to the embodiment shown in FIG. 1. In this figure, the same reference numerals as in FIG. 2 indicate the same parts, so the explanation thereof will be omitted.
That is, the three-winding transformer according to the present invention has two unit transformers 61 and 62, and the arrangement and connection of the high voltage windings 11 and 12 and the low voltage windings 21 and 22 of each transformer 61 and 62. The configuration is the same as the conventional one shown in FIG.

The present invention is characterized in that the tertiary windings 31 and 32 are connected in series via a current limiting reactor 7, as shown in FIG. With this connection configuration, the end of the tertiary winding 31 facing the line terminal u of the low voltage winding 21 of the unit transformer 61 becomes the line terminal a ₁ , and the low voltage winding 2 of the unit transformer 62
The end of the tertiary winding 32 facing the line terminal u of No. _{2 becomes the line terminal a2} .

Since the line terminals a ₁ and a ₂ are connected to surge diazosorbers z ₁ and z ₂ to protect the terminal voltages from being below the insulation level of the terminals, the low voltage windings 21 and 22 Even at the opposing portion of the line terminal u where the transfer voltage from the tertiary windings 31 and 32 to the tertiary windings 31 and 32 is maximum, it can be suppressed to the insulation level of the tertiary windings 31 and 32 themselves, that is, the insulation level of the line terminals a ₁ and a ₂ or less. .

Therefore, the voltage generated between the iron core 42 and the tertiary winding 32, that is, the voltage generated between the low voltage winding 22 and the tertiary winding 32
In conventional wiring, the transition voltage to the tertiary line terminal
Although the insulation level was higher than that of a ₁ and a ₂ , the wiring connection of the present invention is lower than this level, so that the insulation dimension between the iron core 42 and the tertiary winding 32 can be reduced.

In the embodiment of the present invention shown in Fig. 1, a case has been explained in which the low-voltage winding and high-voltage winding are arranged outside the tertiary winding, but in the case of an auto-transformer, they are arranged outside the tertiary winding. A similar effect can be obtained by arranging a path winding and a series winding. Furthermore, in the case of Fig. 1, the tertiary windings 31 and 32 divided into two parts are stored in separate tanks, but the tertiary windings 31 and 32 divided into two parts are wound on different core legs on the same core. Even when the current limiting reactor 7 is installed and housed in the same tank, the same effect can be obtained by connecting the current limiting reactor 7 at the same position.

[Effect of idea]

As described above, according to the present invention, by connecting two divided tertiary winding units in series with a current limiting reactor placed between them, a transition is made from a low voltage winding to a divided tertiary winding unit. Since the voltage is suppressed to below the insulation level of the tertiary winding itself by the surge absorber at each terminal, the insulation dimension between the winding and the iron core can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a winding layout diagram showing an embodiment of the three-winding transformer of the present invention, and FIG. 2 is a winding layout diagram showing a conventional three-winding transformer. 61, 62... Unit transformer, 51, 52... Tank, 11, 12... High voltage winding unit, 21, 22
...Low voltage winding unit, 31, 32... Tertiary winding unit, 41, 42... Iron core, U... Line side high voltage terminal, O... Neutral point side high voltage terminal, u... Line side low voltage terminal, θ...neutral side low voltage terminal, _a1 , _a2 ...tertiary winding terminal.

Claims (1)

[Scope of utility model registration request] In a three-winding transformer in which the three windings of a high-voltage winding, a low-voltage winding, and a tertiary winding are divided into two winding units per unit and wound on different iron core legs, the tertiary winding is divided into two. Wire units are connected in series via a current limiting reactor, and the line terminal sides of both tertiary winding units and the line terminal sides of the windings wound outside each tertiary winding unit are arranged to face each other. A three-winding transformer featuring: