JPH04250606A - Potential transformer - Google Patents

Abstract

PURPOSE:To improve error characteristics and residual voltage characteristics of a sub-secondary winding at the time of a secondary short-circuit by reducing the leakage reactance of a potential transformer. CONSTITUTION:A primary winding is divided into a first part 2A and second part 2B and a secondary winding 3 is arranged between these first and second parts to improve the combination of the primary and secondary windings. Thus, a primary leakage reactance is reduced so that not only error characteristics but also residual voltage characteristics of a sub-secondary winding at the time of a secondary short-circuit are made satisfactory. An electrode 11 is arranged at least on one side out of the inside and outside of the second part of the primary winding via dielectric 10 so that a capacitor is formed between the electrode 11 and the second part 2B. In this manner, the induced voltage of the second part of the primary winding is prevented from rising at the time of applying a surge voltage.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to potential transformers.

0002

2. Description of the Related Art The structure of a conventional potential transformer is shown in FIG. 4, and its wiring diagram is shown in FIG. In these figures, 1 is a rectangular closed magnetic circuit iron core, 2 is a primary winding, and 3 is a secondary winding arranged concentrically inside the primary winding 2. The winding 3 is wound around one leg of the iron core 1. U and V are primary terminals, and Um and Vm are secondary terminals.

0003

The equivalent circuit of the above-mentioned potential transformer is shown in FIG. Here, 5 is the secondary burden of impedance Zbm, and R1' and X1' are the resistance and leakage reactance of the primary winding, respectively. Furthermore, Rm and Xm are the resistance and leakage reactance of the secondary winding, respectively, and V2 is the secondary induced voltage, V2
' is the secondary terminal voltage (secondary induced voltage minus secondary voltage drop).

The error δ of a potential transformer when a secondary load of impedance Zbm is connected is given by the following equation.

δ=V2−V2′={(R1′+Rm)+j(X1′+Xm
)}/Zbm...(1) Also, when adding an auxiliary secondary winding to the secondary side to prevent malfunction of the relay, the secondary winding is connected to the main secondary winding and the main secondary winding. The equivalent circuit in this case is as shown in FIG. 7. In the figure, Rm and Xm are the resistance and leakage reactance of the main secondary winding, Ra and Xa are the resistance and leakage reactance of the sub-secondary winding 4, respectively, and Ua is the terminal of the sub-secondary winding. When the sub-secondary winding is added, the residual voltage Va in the sub-secondary winding occurs when the secondary is shorted (V2'=0).
This residual voltage is given by the following equation.

Va = {(Rm +jXm)V2}/{(R1'+
Rm)+j(X1'+Xm)}...(2) Here, δ
, V2, V2', Va and Zbm are vector quantities.

As is clear from the above equation (1), if the leakage reactances X1' and Xm can be made small, the error can be reduced. Furthermore, as can be seen from equation (2) above, when a sub-secondary winding is provided, the residual voltage of the sub-secondary winding in the event of a secondary short circuit can be increased by reducing the leakage reactances X1' and Xm. Can be done.

However, in conventional voltage transformers, 1
Because the coupling between the primary and secondary windings was poor and the leakage reactance between the primary and secondary windings was large, the leakage reactance accounted for more than half of the total impedance, and in extreme cases, the leakage reactance It could reach up to 70-80%. Note that approximately 90% of the leakage reactance is the leakage reactance X1' of the primary winding.

[0009] As described above, the leakage reactance of conventional voltage transformers was large, making it difficult to obtain good error characteristics.

Furthermore, in conventional instrument transformers, leakage reactance was large, so when a sub-secondary winding was provided, it was difficult to improve the residual voltage characteristics of the sub-secondary winding in the event of a secondary short circuit. Ta.

One object of the present invention is to improve the error characteristics of a potential transformer.

Another object of the present invention is to improve the residual voltage characteristics of the auxiliary secondary winding in the event of a secondary short circuit when the auxiliary secondary winding is provided on the secondary side of a potential transformer. be.

[0013]

[Means for Solving the Problems] The present invention provides a primary winding and a secondary winding.
This relates to an instrument transformer in which a secondary winding is arranged concentrically and wound around an iron core.

In the present invention, the primary winding is divided into a first part and a second part, the first part is placed outside the secondary winding, and the second part is placed outside the secondary winding. Place each inside the . Then, an electrode is arranged inside the second part of the primary winding via a dielectric, and the electrode is connected to a ground potential part, and the electrode and the
A capacitor is formed between the second part of the next winding and the second part of the winding. In the above configuration, the electrode is placed inside the second part of the primary winding via a dielectric, but the electrode is placed outside the second part of the primary winding (between the second part and the secondary winding). An electrode may be placed between the two electrodes via a dielectric material, and the electrode may be connected to a ground potential section.

Further, electrodes may be disposed on the inside and outside of the second portion of the primary winding via a dielectric material, and both electrodes may be connected to a ground potential portion.

In the present invention, an auxiliary secondary winding may be provided on the secondary side, and in this case, the secondary winding is wound concentrically with the main secondary winding. and a sub-secondary winding that is rotated.

[0017]

[Operation] As described above, the primary winding is divided into a first part and a second part, and the secondary winding is arranged between the first part and the second part. In this case, since the secondary winding is sandwiched between the primary windings, the coupling between the primary winding and the secondary winding can be improved. Therefore, the primary leakage reactance can be reduced, and the internal impedance can be reduced, so that the error characteristics can be improved. Also, if the error characteristics are the same,
Since the diameter of the winding conductor can be made thinner and the cross-sectional area of the iron core can be reduced, it is possible to downsize the instrument transformer and reduce its cost.

Furthermore, since the leakage reactance can be reduced, when a sub-secondary winding is provided, the residual voltage characteristics of the sub-secondary winding at the time of a secondary short-circuit can be improved.

[0019] When a high frequency voltage such as a surge voltage is applied to the above-mentioned instrument transformer, the voltage induced in the second part of the primary winding located inside the secondary winding rises due to its inductance. In extreme cases, dielectric breakdown may occur between the second part of the primary winding and the secondary winding, but as in the present invention, the inside or outside of the primary winding, or Electrodes are placed on both the inside and outside through dielectrics,
When the electrode is connected to the ground potential part and a capacitor is formed between the second part of the primary winding and the electrode, the capacitor exhibits a low impedance against surges, so when a surge voltage is applied, It is possible to prevent the induced voltage in the second portion of the next winding from rising.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows the structure of a voltage transformer according to the present invention, and the winding connections thereof are as shown in FIG.

In these figures, 1 is a rectangular closed magnetic circuit core, 2 is a primary winding, and 3 is a secondary winding. It is divided into two parts, including a second part 2B having a smaller number of turns. These windings are arranged such that the first part 2A of the primary winding is concentrically arranged outside the secondary winding 3, and the second part 2B of the primary winding is arranged inside the secondary winding 3. It is wound around one leg of the iron core 1 while being concentrically arranged. In this example, the second part 2B of the primary winding
An electrode 11 is arranged inside (between the second portion 2B and the iron core 1) with a dielectric (insulator) 10 interposed therebetween, and the electrode 11 is connected to the ground potential part of the iron core 1 and the like. FIG. 3 shows the positional relationship between the second portion 2B of the primary winding, the dielectric 10, and the electrode 11. In this example, the electrode 11 is connected to the iron core 1 through a grounding wire 12.

The dielectric 10 is formed into a cylindrical shape along the circumferential direction of the winding. The electrode 11 can be composed of a substantially cylindrical conductor attached to the outer periphery of the dielectric 10;
In this case, it is necessary to separate a part of the conductor constituting the electrode so that the electrode 11 does not form one turn.

[0023] Note that U and V are primary terminals, and Um and Vm are 2
This is the next terminal.

[0024] With the above configuration, the secondary winding 3
Since the structure is sandwiched between the next windings 2A and 2B, 1
Next, the primary leakage reactance can be reduced by improving the coupling between the secondary and the internal impedance of the potential transformer.

Furthermore, with the above structure, the electrode 11 and the second portion 2B of the primary winding form a capacitor C (FIG.
) can be formed. Since this capacitor C exhibits a low impedance to high frequency voltages such as surge voltages, the induced voltage in the second portion 2B of the primary winding when high frequency voltages such as surge voltages are applied to the potential transformer. can be prevented from lifting.

In the above embodiment, the electrode 11 was placed inside the second portion 2B of the primary winding with the dielectric 10 interposed therebetween, but the electrode 11 was placed outside the second portion 2B of the primary winding (second between the part 2B and the secondary winding 3) via a dielectric,
The electrode may be connected to a ground potential section.

Further, an electrode is disposed inside the second portion 2B of the primary winding via a dielectric material, and the second portion 2B
An electrode may also be placed on the outside of the electrode via a dielectric material, and both electrodes may be connected to a ground potential section.

In the above embodiment, the secondary winding consists of a single winding, but an auxiliary secondary winding is provided on the secondary side to prevent malfunction of the relay in the event of a secondary short circuit. When inducing a residual voltage in the sub-secondary winding, the secondary winding 3 is constituted by a main secondary winding and a sub-secondary winding wound concentrically with the main secondary winding. .

[0029]

As described above, according to the present invention, the primary winding is divided into the first part and the second part, and the Since the structure is such that the secondary winding is arranged, the secondary winding can be sandwiched between the primary windings and the coupling between the primary winding and the secondary winding can be improved. Therefore, the primary leakage reactance can be reduced,
This has the advantage of reducing internal impedance and improving error characteristics. Furthermore, according to the present invention, if the error characteristics remain the same, the diameter of the winding conductor can be made thinner or the cross-sectional area of the iron core can be reduced, thereby reducing the size and cost of the potential transformer. This has the advantage that it is possible to reduce the

Furthermore, according to the present invention, since the leakage reactance can be reduced, when a sub-secondary winding is provided, it is possible to improve the residual voltage characteristics of the sub-secondary winding in the event of a secondary short circuit. can.

[0031] Furthermore, in the present invention, a capacitor can be placed between the second portion of the primary winding and the electrode by arranging the electrode on the inside or outside of the primary winding, or on both the inside and outside of the primary winding with a dielectric interposed therebetween. Since the capacitor has a low impedance against surges, it is possible to prevent the induced voltage in the second portion of the primary winding from rising when a surge voltage is applied.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram schematically showing the configuration of an embodiment of the present invention.

FIG. 2 is a wiring diagram of a winding according to an embodiment of the present invention.

FIG. 3 is an enlarged cross-sectional view of a main part showing a state in which electrodes are disposed inside a second portion of a primary winding via a dielectric material in an embodiment of the present invention.

FIG. 4 is a configuration diagram schematically showing the configuration of a conventional potential transformer.

FIG. 5 is a wiring diagram of windings of a conventional potential transformer.

FIG. 6 is a circuit diagram showing an equivalent circuit of a voltage transformer when no sub-secondary winding is provided.

FIG. 7 is a circuit diagram showing an equivalent circuit of a potential transformer when a sub-secondary winding is provided.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...Iron core, 2...Primary winding, 2A...1st part of primary winding, 2B...2nd part of primary winding, 3...Secondary winding, 10...
Dielectric, 11...electrode.

Claims (4)

[Claims] 1. An instrument transformer comprising a primary winding and a secondary winding arranged concentrically and wound around an iron core, wherein the
The secondary winding is divided into a first part and a second part, the first part is arranged outside the secondary winding, and the second part is arranged inside the secondary winding, and the first part is arranged inside the secondary winding. An electrode is placed inside the second portion of the primary winding via a dielectric, and the electrode is connected to a ground potential part, forming a capacitor between the electrode and the second portion of the primary winding. An instrument transformer characterized by: 2. An instrument transformer comprising a primary winding and a secondary winding arranged concentrically and wound around an iron core, wherein the
The secondary winding is divided into a first part and a second part, the first part is arranged outside the secondary winding, and the second part is arranged inside the secondary winding, and the first part is arranged inside the secondary winding. An electrode is placed outside the second portion of the primary winding via a dielectric, and the electrode is connected to a ground potential, forming a capacitor between the electrode and the second portion of the primary winding. An instrument transformer characterized by: 3. An instrument transformer comprising a primary winding and a secondary winding arranged concentrically and wound around an iron core, wherein the
The secondary winding is divided into a first part and a second part, the first part is arranged outside the secondary winding, and the second part is arranged inside the secondary winding, and the first part is arranged inside the secondary winding. Electrodes are disposed on the inside and outside of the second part of the primary winding through a dielectric, and both electrodes are connected to a ground potential part, and between the two electrodes and the second part of the primary winding. An instrument transformer characterized by forming a capacitor. 4. The secondary winding includes a main secondary winding and a main secondary winding.
The potential transformer according to any one of claims 1 to 3, comprising an auxiliary secondary winding wound concentrically with the secondary winding.