JPH08306253A - Bushing - Google Patents

Abstract

PURPOSE: To provide an inexpensive and simple bushing which has reliable voltage dividing function without using a capacitor element. CONSTITUTION: A main circuit conductor of a high voltage charging part is made to be a penetrating conductor 2A in an insulator part 3, an outer output terminal 5 capacity-coupled to the penetrating conductor is installed in an outer surface part of the insulator part, and the voltage divided by an outer impedance Zo connected to the outer output terminal 5 and the capacitive coupling part is sent out through the outer output terminal 5. The penetrating conductor is made to have a circular cross-section shape and a cylindrical electrode 6 having the penetrating conductor as a coaxial core is installed in the insulator part. Consequently, a capacitor is formed between the penetrating conductor and the cylindrical electrode and at the same time the outer output terminal is connected to the cylindrical electrode and a core with 8a of a shielded electric wire 8 in a prescribed length is inserted between the outer output terminal and the outer impedance and the shield 8b of the shielded electric wire 8 is earthed, so that a capacitor is formed between the core wire and the shield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bushing used for drawing out a voltage of an electric device such as a gas-insulated device corresponding to a high voltage, and in particular, it secures a shield function for a high voltage charging part (penetrating conductor) and divides the voltage. The present invention relates to a bushing that realizes cost reduction of a circuit.

[0002]

2. Description of the Related Art Generally, in an electric device having a voltage conductor such as a gas-insulated device, a voltage detecting device is housed as an individual component together with a bushing for pulling out a cable. FIG. 8 is a side view showing the structure of a conventional bushing described in, for example, Japanese Unexamined Patent Publication No. 4-47613. In the figure, 1 is provided in an electric device (a gas insulation device or the like not shown) for mounting the bushing. It is a frame.

Reference numeral 2 is a main circuit conductor which serves as a main body of a bushing which is charged with a high voltage, and constitutes a through conductor of an insulator portion (described later). Reference numeral 3 denotes an insulator portion of a bushing formed so as to cover the through conductor 2, 3a denotes a frame portion of the insulator portion 3 attached to the frame 1 of the electric device, and 4 denotes a periphery of the through conductor 2 in the insulator portion 3. , S is the interface between the insulator part 3 and the capacitor 4.

Reference numeral 5 is a low voltage lead terminal of the capacitor 4, which constitutes an external output terminal of the bushing. Zo is an external impedance connected between the external output terminal 5 and the ground, and includes a capacitor and the like.

The conventional bushing is constructed as shown in FIG. 8, and when the through conductor 2 is charged with a high voltage, the insulator part 3 is formed.
By the capacitor 4 provided inside and the external impedance Zo (for example, a capacitor) provided outside,
The divided voltage thus divided is output from the external output terminal 5.

As a result, a low-voltage divided voltage can be drawn to the external impedance Zo. Instead of the capacitor 4, a current transformer or the like (not shown) is provided in the insulator portion 3.
There is also a case where a bushing having a current detection function is provided.

[0007]

As described above, in the conventional bushing, the circuit element (capacitor 4) having a shorter life than the insulator portion 3 is provided in the insulator portion 3 of the bushing. However, there is a problem in that it is not possible to realize cost reduction when the bushing goes down and it is necessary to replace the entire bushing.

Further, since the circuit element called the capacitor 4 is provided in the insulator portion 3, in order to improve the adhesion of the interface S between the insulator portion 3 and the capacitor 4, the outer corner portion of the capacitor 4 is formed. Since it is necessary to form a curved surface or to perform a coating process for relaxing the thermal stress at the interface S, there is a problem that the cost is increased and the bushing as a whole becomes expensive.

Further, when the external impedance Zo connected to the external output terminal 5 fails, the output voltage of the external output terminal 5 is not divided, and an excessive voltage is output.

Further, when a current transformer in the insulator portion 3 is provided in place of the capacitor 4, if a surge transient voltage is generated in the through conductor 2 penetrating the insulator portion 3, the insulator portion 3 There is a problem in that a surge transient voltage may be transferred to the secondary circuit of the current transformer due to an electrostatic action through the current transformer, causing a failure in the secondary circuit in the current transformer.

The present invention has been made in order to solve the above problems, in which the insulating portion itself which acts as a dielectric and the external wiring itself connected to the external output terminal are respectively provided with electrostatic capacitance. It is possible to reduce the cost by constructing a voltage divider consisting of the following, and by interposing a voltage divider around the through conductor, it is possible to prevent current transformers, etc. located at the outer peripheral part of the capacitive coupling part of the through conductor. The purpose is to obtain a bushing that can be electrically shielded.

[0012]

According to a first aspect of the present invention, there is provided a bushing in which a part of a main circuit conductor, which is a high voltage charging section, in the longitudinal direction is covered with an insulator, and the main circuit conductor is insulated. An external output terminal that is capacitively coupled to the through conductor is provided on the outer surface of the insulator portion as well as the through conductor in the portion,
In a bushing in which a divided voltage divided by an external impedance connected to an external output terminal and a capacitive coupling portion is output from the external output terminal, the through conductor is formed in a circular cross-sectional shape, and the through conductor is coaxially centered. By providing the cylindrical electrode in the insulator part, a capacitor is formed between the through conductor and the cylindrical electrode, and the external output terminal is connected to the cylindrical electrode, and the specified length is provided between the external output terminal and the external impedance. By inserting the core wire of the shielded electric wire and grounding the shield of the shielded electric wire, a capacitor is formed between the core wire and the shield.

A bushing according to a second aspect of the present invention is the bushing according to the first aspect, in which a cylindrical current transformer is attached to an external position of the cylindrical electrode.

A bushing according to a third aspect of the present invention is the bushing according to the first or second aspect, in which the intermediate portion in the longitudinal direction outside the cylindrical electrode is narrowed into a curved surface.

A bushing according to a fourth aspect of the present invention is the bushing according to the first or second aspect, in which the intermediate portion in the longitudinal direction of the through conductor is enlarged in a curved shape.

A bushing according to a fifth aspect of the present invention is the bushing according to any one of the first to fourth aspects.
A ring portion is formed at both ends of a cylindrical electrode.

[0017]

In the first aspect of the present invention, the electrostatic capacitance (capacitor) is formed by the insulator portion interposed between the through conductor and the cylindrical electrode surrounding the outer periphery thereof. In addition, the external wiring connected to the external output terminal is used as a shielded wire,
Capacitance is also formed between the core of the shielded wire and the shield. By forming a voltage dividing circuit by the electrostatic capacitance formed around each of these penetrating conductors and external wiring and connecting the core wire of the shield wire to the cylindrical electrode, the potentials of the cylindrical electrode and the external output terminal are two static. It becomes the divided potential of the capacitance ratio. Therefore, the voltage dividing function capable of measuring the voltage of the through conductor can be inexpensively and easily and surely configured without providing a capacitor element in the insulator portion and the external impedance. In addition, by appropriately setting the length of the shielded wire connected to the external output terminal, the electrostatic capacity can be made much larger than the electrostatic capacity formed on the side of the through conductor, and the cylindrical electrode and the external output terminal can be made. The divided voltage at can be set to a very low voltage.
Furthermore, as a function of the cylindrical electrode, a shield effect for the through conductor (high-voltage charging part) is provided, and since the cylindrical electrode has a low voltage partial potential, a very low electric field is generated outside the cylindrical electrode. The high voltage charging section is practically shielded from the ground.

According to the second aspect of the present invention, since the cylindrical electrode has an electrostatic shield effect on the through conductor (high voltage charging section), the current transformer is attached to the external position of the cylindrical electrode. It is possible to suppress the transfer of the surge transient voltage and prevent damage to the secondary circuit in the current transformer.

Further, according to a third aspect of the present invention, the intermediate portion in the longitudinal direction on the outside of the cylindrical electrode is narrowed into a curved surface, and the isolation distance between the through conductor and the cylindrical electrode is reduced to increase the electrostatic capacitance. By setting, the influence of stray impedance is suppressed.

Further, according to a fourth aspect of the present invention, the intermediate portion in the longitudinal direction of the through conductor is enlarged into a curved surface, and the isolation distance between the through conductor and the cylindrical electrode is reduced to set a large capacitance. By doing so, the effect of stray impedance is suppressed.

Further, according to a fifth aspect of the present invention, a ring portion is formed at the end of the cylindrical electrode to suppress electric field concentration at the interface with the insulator portion.

[0022]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. 1 is a side sectional view showing Embodiment 1 of the present invention, and FIG.
1 is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 3 is a perspective view showing the structure of the cylindrical electrode in FIG. 1. In FIGS. 1 and 2, 1, 3, 3a, 5 and Zo are as described above. It is similar. 2A corresponds to the through conductor 2 described above,
In this case, the penetrating conductor 2A is formed of a cylinder and has a circular cross-sectional shape as shown in FIG.

In each figure, reference numeral 6 denotes a cylindrical electrode arranged so as to surround the penetrating conductor 2A in the insulator part 3, and has a hollow shape with the penetrating conductor 2A as the coaxial center. 6
Reference numeral a denotes a ring portion for relaxing an electric field formed at an end portion of the cylindrical electrode 6, and reference numeral 6b denotes a cylindrical portion which is a base body of the cylindrical electrode 6.

Reference numeral 3b is an insulator portion located between the through conductor 2A and the cylindrical electrode 6, and the through conductor 2A and the cylindrical electrode 6 are provided.
An electrostatic capacity, that is, a capacitor is formed between and.
3c is an insulator portion located on the outer peripheral portion of the cylindrical electrode 6, and 7 is a lead wire connecting the cylindrical electrode 6 and the external output terminal 5.

Reference numeral 8 denotes a shielded wire having a specified length inserted between the external output terminal 5 and the external impedance Zo. Both ends of the core wire 8a in the shielded wire 8 are respectively connected to the external output terminal 5 and the external impedance Zo. It is connected. The shield 8b of the shielded electric wire 8 is connected to the ground wire 9
An insulator (not shown) between the core wire 8a and the shield 8b is similarly grounded via a capacitor and forms a capacitor.

In the bushing constructed as described above, the capacitance value of the capacitor formed by the insulator portion 3b between the cylindrical through conductor 2A and the cylindrical electrode 6 is set to C1, and the core of the shielded wire 8 is set. Let C2 be the capacitance value of a capacitor formed by an insulator between the line 8a and the shield 8b.

As shown in FIGS. 1 to 3, the cylindrical electrode 6 is connected to the core wire 8a of the shield wire 8 via the lead wire 7 and the external output terminal 5, and the shield 8b of the shield wire 8 is connected to the ground wire 9. By connecting, the capacitance value between the through conductor 2A (high voltage charging part) and the ground is C1 and C.
A series circuit of two capacitors of 2 is formed. Therefore, the voltage of the cylindrical electrode 6 depends on the capacitance values C1 and C2.
The partial voltage potential corresponds to the ratio of.

With the above bushing, it is possible to form a voltage measuring circuit for dividing the high voltage applied to the penetrating conductor 2A into a low voltage and outputting it. That is, in order to significantly reduce the divided voltage, the condition of C1 << C2 may be satisfied by setting the length of the shielded wire 8 to be relatively large.

At this time, it is not necessary to provide a capacitor inside the external impedance Zo in the insulator portion 3, and the cost can be reduced. Further, since the ring portions 6a are formed at both ends of the cylindrical electrode 6, the electric field concentration at the interface between the cylindrical electrode 6 and the insulator portion 3 can be easily alleviated. The cylindrical electric field 6 also functions as a shield for the through conductor 2A.

Example 2. In the first embodiment, the cylindrical electrode 6 is arranged around the penetrating conductor 2A to form only the capacitor, but a current transformer may be further arranged around the cylindrical electrode 6. FIG. 4 shows the insulator portion 3 on the outer peripheral portion of the cylindrical electrode 6.
Example 2 of the present invention in which a current transformer is provided in c is a side sectional view, and FIG. 5 is a sectional view taken along line BB in FIG.

In each figure, 1, 2A, 3, 3a-3
c, 5 to 7, 8, 8a, 8b, 9 and Zo are the same as described above. Reference numeral 10 is a cylindrical current transformer attached to the outside of the cylindrical electrode 6, 11 is a secondary lead wire of the current transformer 10, and 12 is a terminal for drawing the secondary lead wire 11 to the outside.

As described above, since the potential of the cylindrical electrode 6 is used as a normal measuring voltage, the shield wire 8
By setting the length of, the condition of C1 << C2 can be satisfied and the voltage can be divided into a low voltage. In this way, when the potential of the cylindrical electrode 6 is lowered, the insulator portion 3c located outside the cylindrical electrode 6 has a low electric field.

That is, since the cylindrical electrode 6 acts as a shield electrode, the current transformer 1 as shown in FIGS.
When 0 is arranged, even if a surge overvoltage is applied to the through conductor 2A, electrostatic transfer is limited, so that overvoltage should be applied to the secondary circuit of the current transformer 10. There is no. Therefore, damage to the current transformer 10 can be reliably prevented.

Example 3. Further, in the first embodiment, the cross-sectional shape of the cylindrical portion 6b (intermediate portion in the longitudinal direction), which is the generatrix of the cylindrical electrode 6, is formed in a straight line, but the inner diameter of the intermediate portion is increased in order to increase the capacitance value C1. You may squeeze it into a curved surface. Figure 6
FIG. 4 is a cross-sectional view showing a cylindrical electrode according to a third embodiment of the present invention in which an intermediate portion of the cylindrical portion (longitudinal direction of the cylindrical electrode) is narrowed down, and in the drawing, 2A, 3b, 6 and 6a are the same as those described above. .

The structure not shown in FIG. 6 is as shown in FIG. Further, 16b corresponds to the cylindrical portion (intermediate portion) 6b of the cylindrical electrode 6. In this case, the cylindrical portion 16b is
The diameter of the middle part is smaller than the diameter of both ends. d
Is the distance between the through conductor 2A and the cylindrical electrode 6, that is, the thickness of the insulator portion 3b.

In general, the distance d between the through conductor 2A and the cylindrical electrode 6 (the thickness of the insulator portion 3b) is determined by the cylindrical electrode 6
Determined by the electric field strength at the ring portions 6a at both ends of
Further, since the electric field strength is concentrated on both ends of the cylindrical electrode 6, the electric field strength in the middle portion in the longitudinal direction of the cylindrical electrode 6, that is, the cylindrical portion 6b becomes a low value when the narrowed portion is not provided.

However, since the capacitance value C1 is inversely proportional to the separation distance d, the capacitance value C1 is increased by adopting a structure in which the inner diameter of the cylindrical portion 16b is narrowed like the cylindrical portion 16b in FIG. be able to. Therefore, a reliable voltage dividing function can be achieved without being affected by various floating impedances around the bushing. Usually, in order to suppress the influence of the floating impedance, the capacitance value C1 of the insulator portion 3b may be set to about 100 pF or more. Further, in order to make the electrostatic capacitance value C2 connected to the external output terminal 5 extremely larger than the electrostatic capacitance value C1, the shielded electric wire 8 may be further lengthened.

Example 4. In the third embodiment, in order to increase the capacitance value C1, the inner diameter of the cylindrical portion 16b is narrowed to reduce the separation distance d between the penetrating conductor 2A and the cylindrical portion 6b of the cylindrical electrode 6. The outer diameter of the intermediate portion of 2A may be enlarged in a curved shape to reduce the separation distance d.

FIG. 7 shows the intermediate portion 2 of the through conductor 2A in the longitudinal direction.
FIG. 8B is a cross-sectional view showing a through conductor 2A according to a fourth embodiment of the present invention in which the outer diameter is set large in b. In the figure, 2
b is an intermediate portion of the through conductor 2A, and the outer diameter thereof is set to be larger than that of both end portions. In this case, the shape of the cylindrical electrode 6 is the same as that of the first embodiment.

In FIG. 7, the through conductor 2A and the cylindrical electrode 6
The separation distance d in the insulator portion 3b between and is narrowed down, so that the electrostatic capacitance value C1 can be increased for the same reason as described in the third embodiment, and the influence of stray impedance is similarly suppressed. Therefore, the reliability of the voltage dividing function can be improved.

Example 5. In the third and fourth embodiments, only the electrostatic coupling relationship between the penetrating conductor 2A and the cylindrical electrode 6 is shown, but like the second embodiment, the current transformer 10 (see FIG. 4) is provided around the cylindrical electrode 6. May be provided. Further, although the ring portions 6a are provided at both ends of the cylindrical electrode 6, the ring portions 6a can be omitted if the electric field concentration at both ends does not pose a particular problem.

[0042]

As described above, according to claim 1 of the present invention, a part of the main circuit conductor serving as the high voltage charging section in the longitudinal direction is covered with an insulator, and the main circuit conductor is insulated. The external output terminal capacitively coupled to the through conductor is provided on the outer surface of the insulator part, and the divided voltage is divided by the external impedance connected to the external output terminal and the capacitive coupling part. In a bushing that outputs a signal from an external output terminal, the through conductor is formed into a circular cross-sectional shape, and a cylindrical electrode having the through conductor as a coaxial center is provided in the insulator portion, thereby providing a capacitor between the through conductor and the cylindrical electrode. Connect the external output terminal to the cylindrical electrode, insert the core wire of the shielded wire of the specified length between the external output terminal and the external impedance, and ground the shield of the shielded wire. More, since the formation of the capacitor between the core wire and the shield, cheap and easy and reliable voltage dividing function without using an element such as a capacitor is achieved an effect of bushings that achieves cost reduction is obtained.

According to the second aspect of the present invention, in the first aspect, since the cylindrical current transformer is attached to the outside of the cylindrical electrode having the electrostatic shield effect, the surge voltage is prevented from shifting. As a result, there is an effect that a bushing that prevents damage to the secondary circuit in the current transformer is obtained.

According to a third aspect of the present invention, in the first or second aspect, the intermediate portion in the longitudinal direction outside the cylindrical electrode is narrowed into a curved surface so that the static electricity between the through conductor and the cylindrical electrode is reduced. Since the capacitance is set large, the effect of stray impedance can be suppressed, and the bushing having a highly reliable voltage dividing function can be obtained.

According to a fourth aspect of the present invention, in the first or second aspect, the intermediate portion in the longitudinal direction of the through conductor is enlarged into a curved surface so that the electrostatic capacitance between the through conductor and the cylindrical electrode is increased. Since the capacitance is set large, the effect of stray impedance can be suppressed, and a bushing having a highly reliable voltage dividing function can be obtained.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, ring portions are formed at both ends of the cylindrical electrode so that the interfacial electric field concentration with the insulator portion is concentrated. Since it is relaxed, there is an effect that a bushing that prevents damage to the electrostatic coupling portion including the cylindrical electrode can be obtained.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a structure of a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a perspective view showing a structure of a cylindrical electrode in FIG.

FIG. 4 is a side sectional view showing the structure of Embodiment 2 of the present invention.

5 is a cross-sectional view taken along the line BB in FIG.

FIG. 6 is a side sectional view showing a structure of a cylindrical electrode according to a third embodiment of the present invention.

FIG. 7 is a side sectional view showing the structure of a cylindrical electrode according to Example 4 of the present invention.

FIG. 8 is a side view showing a structure of a conventional bushing.

[Explanation of symbols]

2A through conductor, 2b middle part, 3, 3b, 3c insulator part, 5 external output terminal, 6 cylindrical electrode, 6a ring part, 6b, 16b cylindrical part, 7 lead wire, 8 shielded wire, 8a core wire, 8b shield , 9 ground wire, 10 current transformer, d isolation distance, Zo external impedance.

Claims (5)

[Claims] 1. A main circuit conductor serving as a high-voltage charging part is covered with an insulating material around a part in a longitudinal direction of the main circuit conductor, and the main circuit conductor is a through conductor in the insulating part. An external output terminal capacitively coupled is provided on the outer surface of the insulator portion, and a divided voltage divided by the external impedance connected to the external output terminal and the capacitive coupling portion is output from the external output terminal. In the bushing, a cross-sectional shape of the through conductor is formed in a circular shape, and a cylindrical electrode having the through conductor as a coaxial center is provided in the insulator portion, thereby forming a capacitor between the through conductor and the cylindrical electrode. In addition, the external output terminal is connected to the cylindrical electrode, a core wire of a shielded wire having a specified length is inserted between the external output terminal and the external impedance, and the seal is formed. Bushing by grounding the wire shield, characterized in that the formation of the capacitor between the shield and the conductor. 2. The bushing according to claim 1, wherein a cylindrical current transformer is attached to an external position of the cylindrical electrode. 3. The bushing according to claim 1, wherein the intermediate portion in the longitudinal direction outside the cylindrical electrode is squeezed into a curved shape. 4. The bushing according to claim 1, wherein an intermediate portion in the longitudinal direction of the through conductor is enlarged in a curved shape. 5. The bushing according to claim 1, wherein ring portions are formed at both ends of the cylindrical electrode.