JPS6110968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a three-phase transformer device that is used, for example, in a power system and has a function of suppressing overcurrent in the event of a short circuit or ground fault.

BACKGROUND ART Conventionally, as shown in FIG. 1, there is a grid interconnection device 1 inserted between power systems A and B as a device having a function of suppressing overcurrent in the event of a ground fault or short circuit accident in a power system. As shown in FIG. 2, the conventional grid interconnection device 1 has a primary winding 3 of a series transformer 2 connected in series to power systems A and B, and a secondary winding 4 connected to a compensation power source 5. A compensation voltage Vc having a component orthogonal to the phase voltage of the power system is energized. This compensates for the steady voltage drop due to the impedance of the series transformer 2.

The overcurrent suppression function of this grid interconnection device is
This will be explained using the vector diagrams in Figures a and b. Compensation voltage Vc of series transformer 2, which is a grid interconnection device, = 0
In this case, when the bus current I flows, a voltage drop IX occurs due to the leakage impedance X of the series transformer 2. Therefore, as shown in FIG. 3b, a phase difference occurs between the phase voltages V _A and V _B of the power system interconnected by the series transformer 2. Leakage impedance X of the series transformer 2 is necessary to suppress overcurrent in the event of an accident, but it is desirable that this impedance X be as small as possible during steady state. Therefore, as shown in Fig. 2, by constantly applying a compensation voltage Vc, which has a phase difference almost at right angles to the phase voltage of the power system, to the secondary side of the series transformer 2, as shown in Fig. 3b, voltage drop to
IX can be compensated with compensation voltage Vc. That is, the phase difference angle between the phase voltages V _A and V _B of both power systems connected to the series transformer 2 can be made small, and the impedance of the device in an apparently steady state can be made small. The compensation voltage Vc, which has a quadrature phase with the phase voltage of the power system, is generally determined by the phase voltage by a regulating transformer (not shown) connected between the primary midpoint of the series transformer 2 of each phase and the ground. can get.

On the other hand, in the event of an accident such as a short circuit or ground fault, the fault current is automatically suppressed by the leakage impedance X of the series transformer 2, but the influence of the compensation voltage Vc is Therefore, the fault current will not increase, and the compensation voltage will decrease due to the drop in grid voltage due to a grid fault.
It is well known that this has almost no adverse effect on the fault current suppression function because Vc itself becomes smaller.

In this way, conventional grid interconnection devices have excellent features such as low apparent impedance during steady state and the ability to automatically suppress overcurrent in the event of an accident. Since the system requires a regulator and a regulating transformer, it has the disadvantage of being large in size, requiring a large installation area, and being expensive.

By the way, as a device that adjusts the phase of the system voltage during steady state, there is a load voltage phase adjustment transformer. This requires two windings for each of the three phases of the transformer.
An auxiliary winding for each phase is provided, and one auxiliary winding for another phase and one auxiliary winding for the remaining one phase are connected in series to the main winding for each phase. according to this,
The two auxiliary windings can generate a voltage in phase quadrature with the main winding voltage, and the phase of the system voltage in normal operation can be adjusted by adjusting the taps of each auxiliary winding. (Refer to Japanese Patent Publication No. 33-3972.) However, in order to perform effective phase adjustment in such a load voltage phase adjustment transformer, its own impedance is kept as low as possible. Therefore,
A drawback is that another impedance device must be added to suppress overcurrent in the event of an accident. Also, of the two auxiliary windings connected in series,
There is a drawback that one of the auxiliary windings always has a voltage higher than the neutral point by the voltage of the other auxiliary winding, so the insulation must be strengthened.

The purpose of the three-phase transformer device with overcurrent suppression function of the present invention is to prevent the potential of each auxiliary winding from increasing, thereby reducing the burden of insulation on these windings, tap changers, etc. The purpose is to improve insulation reliability.

In order to achieve the above object, in the present invention, the core leg of each phase is provided with at least a primary and secondary main winding and a plurality of taps and one primary and secondary auxiliary winding that is wound with tap adjustment. The primary winding of each phase is connected in series with the primary auxiliary winding of the adjacent phase, and the secondary winding of each phase and the secondary auxiliary winding of the adjacent phase are By connecting different phases in series in reverse phase order and making a three-phase connection, the potentials of the two auxiliary windings of each phase can be selected separately, and phase adjustment can be performed without any problems.

Hereinafter, an example of the three-phase transformer device of the present invention will be explained using FIGS. 4 and 5.

In this device, the iron core legs 11, 12, 13 of each phase are
respectively, primary main windings U ₁ , V ₁ , W ₁ , primary auxiliary windings U ₂ , V ₂ , W ₂ , and secondary main windings U ₁ , V ₁ , W ₁ ,
Secondary auxiliary windings u ₂ , v ₂ , and w ₂ are wound, and these windings are connected as described below to form a three-phase connection. In addition, among each winding, the primary main winding U ₁ , V ₁ ,
All except W ₁ have multiple taps. U, V, W are the primary terminals of each phase, u,
v and w are secondary terminals of each phase, and O and o are primary and secondary neutral points.

Primary main winding U ₁ , V ₁ , W ₁ and primary auxiliary winding of each phase
Between U ₂ , V ₂ , W ₂ and between the secondary main windings u ₁ , v ₁ , w ₁ and the secondary auxiliary windings u ₂ , v ₂ , w ₂ of each phase are those of the adjacent other phases. They are connected in series with different phases to form a predetermined three-phase connection.

That is, the U-phase primary main winding U ₁ is connected to the W-phase primary auxiliary winding W ² , and the V-phase primary main winding V ₁ is connected to the U-phase primary auxiliary winding W 2.
The secondary auxiliary winding U ₂ and the W-phase primary main winding W ₁ are connected in out-of-phase series with the V-phase primary auxiliary winding V ₂ , respectively.
The other ends of these primary auxiliary windings U ₂ , V ₂ , and W ₂ are connected together to form a neutral point O of the star-shaped connection. In addition, the secondary main windings u ₁ , v ₁ , w ₁ and the secondary auxiliary windings of each phase
u ₂ , v ₂ , w ₂ are the above-mentioned 1 as shown in Figure 4.
Connected in series with different phases so that the next side is in reverse phase order,
The other ends of each of these secondary auxiliary windings u ₂ , v ₂ , w ₂ are connected together to form a neutral point o of the star-shaped connection. With this kind of connection, one end of the primary and secondary auxiliary windings U ₂ , V ₂ , W ₂ , u ₂ , v ₂ , w ₂ of each phase can all be maintained at the neutral point potential. .

In the embodiment of FIG. 4 of the present invention, the three-phase voltage vectors of each winding and terminal voltage during steady state are as shown in FIG. 5a. In other words, the primary each phase voltage V
_U , V _V , and V _W are primary main winding voltages V _{U1 and} V W, respectively.
V _V1 , V _W1 and primary auxiliary winding voltage V _U2 , V _V2 ,
The composite voltage of V _W2 and the secondary phase voltages V _U , V _V ,
V _W is the secondary main winding voltage V _U1 , V _V1 , respectively.
It becomes a composite voltage of V _W1 and secondary auxiliary winding voltages V _U2 , V _V2 , and V _W2 .

In this device, the voltage vector of each phase when the primary and secondary are converted into the same number of turns is shown in FIG. 5b for an example of the U phase. I is the load current, X is 1
Next is the leakage impedance between the two dimensions. The relationship between the primary and secondary voltages in FIG. 5b means the following. That is, when a load current I flows to the three-phase transformer device during steady state, a voltage drop IX occurs due to the leakage impedance X between the primary and secondary, and the primary and secondary main winding voltages V _U1 , V _u
1 , but by adjusting the primary and secondary auxiliary winding voltages V _v2 and V _w2 of the other phases,
The phase difference between the primary and secondary U-phase voltages V _U and V _u can be controlled. Furthermore, in the present invention, by selecting the number of turns and taps of each auxiliary winding, the impedance of the device when it is healthy can be made to appear to be approximately zero.

In the embodiment of the present invention shown in FIG. 4, the arrangement increases the leakage impedance between the primary and secondary windings, for example, the primary and secondary auxiliary windings of each phase are placed between the primary and secondary main windings. By arranging the auxiliary windings, overcurrents in the event of an accident are automatically suppressed, but as for the influence of the auxiliary winding voltage, since it is a component voltage at right angles to the phase voltage, it does not increase the accident current. Because the auxiliary winding voltage itself decreases due to a drop in system voltage due to a system fault, there is almost no negative effect on the fault current suppression function.

Moreover, in the example of Fig. 4, the secondary main windings u ₁ , v ₁ , w ₁
Although a plurality of taps are provided in the main windings, instead of this, taps can be provided in the primary main windings U ₁ , V ₁ , W ₁ , and instead of providing taps in the main windings, separate taps can be provided. Adjustment windings can be connected in series to adjust the voltage.

Further, in the above example, the case where both the primary side and the secondary side are star-shaped connections is shown, but the present invention can also be applied to, for example, a case where the secondary side is a triangular connection. Among the primary and secondary auxiliary windings U ₂ , V ₂ , W ₂ , u ₂ , v ₂ , w ₂ , one auxiliary winding for each phase is connected to the winding side that is star-connected, and the remaining phases are Since one auxiliary winding can be connected to the winding side of the triangular connection, at least one end of the auxiliary winding of each phase connected to the winding side of the star connection is kept at the neutral point potential. be able to.

If configured as in the present invention, one end of all the primary and secondary auxiliary windings or one end of the primary or secondary auxiliary winding in a three-phase transformer device having an overcurrent suppression function is set to the neutral point potential. Because it can be kept in
Since the insulation burden on these auxiliary windings is reduced, the insulation reliability of the transformer can be significantly improved.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams showing conventional grid interconnection equipment, Figure 3 is a vector diagram explaining the operation of Figure 2,
FIG. 4 is a wiring diagram of a three-phase transformer device according to an embodiment of the present invention, and FIGS. 5a and 5b are vector diagrams illustrating the operation of FIG. 4. 11, 12, 13... Iron core legs, U ₁ , V ₁ , W ₁ ...1
Secondary main winding, U ₂ , V ₂ , W ₂ ...Primary auxiliary winding, u ₁ ,
v ₁ , w ₁ ... secondary main winding, u ₂ , v ₂ , w ₂ ... secondary auxiliary winding.

Claims (1)

[Claims] 1. Each of the three-phase core legs is wound with at least a primary and secondary main winding, and one primary and secondary auxiliary winding that is provided with a plurality of taps and whose taps are adjusted. death,
The primary winding of each phase is connected in out-of-phase series with the primary auxiliary winding of the adjacent phase to form a three-phase connection, and the secondary main winding of each phase is connected to the secondary auxiliary winding of the adjacent phase. A three-phase transformer device characterized in that the three phases are connected in series with different phases so that the phase order is reversed from the primary side. 2 At least the primary or secondary main winding,
A three-phase transformer device according to claim 1, characterized in that a plurality of taps are provided.