Circuit breaker of porcelain insulator type

Abstract

 Disclosed is a circuit breaker of the porcelain insulator type provided with a main breaking section having a plurality of series connected breaking contacts (1;1a), and a resistor contact device including a series connection of a resistor (3;3a) and a resistor contact (4;4a) and a capacitor device (6;6a) which are connected in parallel with each of the breaking contacts, in which each breaking contact (1) is mounted in a porcelain insulator (2) and the resistor contact device (3,4) and the capacitor device (6) associated with the breaking contact (1) are mounted in another porcelain insulator (5) disposed in parallel with the first-mentioned porcelain insulator (2).

Description

[0001] The present invention relates to a circuit breaker of the porcelain insulator type, and more particularly to a circuit breaker of the porcelain insulator type having a capacitor means and a resistance contact means which are electrically connected in parallel with a breaking section.

[0002] A high-voltage gas-filled circuit breaker of the porcelain insulator type has a main breaking section having a plurality of series-connected breaking contacts; a resistance contact means including a series connection of a resistor and a resistor contact and connected in parallel with each of the breaking contacts in order to insert the resistor prior to closing of the main breaking section ; for preventing a switching overvoltage in closing of the main breaking section (pre-insertion resistor), or prior to opening of the main breaking section for moderating the recovery voltage condition in opening of the breaking section (opening resistor); and a capacitor means connected in parallel with each of the breaking contacts in order to make the voltage distribution uniform among the breaking contacts when the main breaking section is opened. In the conventional circuit breaker of this type, as disclosed .for example in U.S. Patent No. 4,365,126 issued to Oshima et al. and entitled "GAS CIRCUIT BREAKER", the main breaking section, the resistor contact means and the capacitor means are mounted in three separate porcelain bushings, respectively, which are disposed in parallel to each other so as to constitute one breker unit. A circuit breaker is arranged by a suitable number of such breaker units corresponding to the number of desired breaking contacts, for example, two breaker units, which are mounted to a bracket supported by an upright porcelain bushing.

[0003] Thus, the conventional circuit breaker of the porcelain insulator type employs three porcelain insulators for every unit. Each of the porcelain insulators for a circuit breaker of 500 kv class, for example, has a diameter of-about 30 cm, a length of about 200 cm and a large weight and therefore there arises a problem such that the supporting porcelain insulator and the bracket are required to be sufficiently'large and strong for supporting the breaker units of the breaker, resulting in higher producing cost and large mounting space.

[0004] An object of the present invention is to provide a more economical circuit breaker of the porcelain insulator type.

[0005] According to the present invention, in a circuit breaker of the porcelain insulator type provided with a main breaking section.having a plurality of breaking contacts, and a resistor contact means and a capacitor means which are connected in parallel with each of the breaking contacts, each of the breaking contacts is mounted in a porcelain insulator, and both of the resistor contact means and the capacitor means, which are connected in parallel with the breaking contact, are mounted in another porcelain insulator, so that a circuit breaker unit composed of each of the breaking contacts and the associated resistor contact means and capacitor means is mounted in two porcelain insulators.

[0006] The features and advantages of the present invention will be fully understood from the following description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a schematic diagram illustrating the basic arrangement according to the present invention;

Fig. 2 is a cross-section of a porcelain insulator in which a resistor contact means and a voltage dividing means are mounted;

Figs. 3 and 4 are cross-sections illustrating various arrangements of capacitors of the voltage dividing means; and

Fig. 5 is a cross-section along the V - V line of Fig. 4.

[0007] Referring to Fig. 1, the basic arrangement of the present invention will be described. Fig. 1 shows an example in which a main breaking section of a breaker is constituted by two series-connected breaking contacts 1 and la. A resistor contact means including a resistor 3 and a resistor contact 4 connected in series with each other and a capacitor means including a capacitor 6 are connected in parallel with the breaking contact 1 so as to constitute one breaker unit 10. Similarly, another resistor contact means and a capacitor means are connected in parallel with the other breaking contact la so as to constitute another breaker unit 10a. The electrical connection between each breaking contact and the associated resistor contact means and capacitor means are performed basically in the same manner as that in the conventional one.

[0008] The breaking contact 1 is mounted in a porcelain insulator 2, and the associated resistor contact means and capacitor means are mounted in another porcelain insulator 5 disposed in parallel with the porcelain insulator 2. Similarly, the other breaking contact la and the associated resistor contact means and capacitor means are respectively mounted in porcelain insulators 2a and 5a disposed in parallel with each other. The breaker unit 10 including the porcelain insulators 1 and 5 and the breaker unit 10a including the porcelain insulators la and 5a are symmetrically supported by an upright supporting porcelain insulator 9 through a bracket 8. The supporting porcelain insulator 9 is fixed on a base structure including a supporting base 30 and a housing 20 containing therein an actuator device of the breaker. The actuator device in the housing 20 serves to actuate the main contacts 1 and la and the resistor contacts 4 and 4a through a connecting mechanism mounted in the porcelain insulator 9 and a link mechanism mounted in the bracket 8. In the arrangement as described above, the detailed description with respect to the construction other than the porcelain insulators 5 and 5a in which the resistor contact means and the capacitor means are mounted is omitted here because it is the same as that in the conventional apparatus disclosed, for example, in the above-mentioned U.S. Patent No. 4,365,126.

[0009] According to the present invention, the resistor contact means and the capacitor means are mounted in one porcelain insulator. An embodiment of such an arrangement will be described by referring to Fig. 2. The opposite ends of the porcelain insulator 5 are hermetically sealed by end plates 15 and 16, respectively and an insulating gas such as SF6 is filled in the porcelain insulator 5. An end of the resistor 3 is fixed to the end plate 15. A terminal plate 13 and a fixed contact 11 are attached on the other end of the resistor 3. An electrically conductive guide cylinder 17 is fixed on the end plate 16. A movable contact 12 is slidably supported in the guide cylinder 17 so as to perform closing and opening operation with respect to the fixed contact 11. The guide cylinder 17 is electrically connected to the movable contact 12 and a terminal plate 14 is fitted or fixed on the-outer periphery of the guide cylinder 17. A capacitor 6 having a predetermined capacitance is provided between the terminal plates 13 and 14. The arrangement excepting the terminal plates 13 and 14 and the capacitor 6 is the same as the conventional resistor contact means. According to the present invention, in order to mount the capacitor 6 in the porcelain insulator 5 together with the resistor contact means, the capacitor 6 is supported between the electrically conductive terminal plate 13 mechanically fixed on and electrically connected to the other end of the resistor 3 or the neighborhood thereof and the electrically conductive terminal plate 14 mechanically fixed to and electrically connected to the guide cylinder 17.

[0010] In the embodiment of Fig. 2, the capacitor 6 is constituted by a plurality of annular capacitor elements 6-1 stacked in a generally cylindrical form to provide a space for containing the resistor contact mechanism 4 inside the capacitor 6. The capacitor elements 6-1, each provided at opposite end surfaces with metal layers, are electrically connected in series to each other. The junction portion between the capacitor 6 and-the terminal plate 13 is shown in Fig. 3. The terminal plate 13 is formed in its inner side with an annular groove 21 and the end annular capacitor element 6-1 is loosely fitted into the groove 21. A spring 23 and a metallic annular plate 29 are disposed between the end annular capacitor element 6-1 and the bottom surface of the groove 21 so as to urge the capacitor 6 against the terminal plate 14 on the opposite side thereby to ensure the electrical connection between the capacitor 6 and each of the terminal plates 13 and 14. The junction portion between the capacitor 6 and the terminal plate 14 is arranged similarly to that between the capacitor 6 and the terminal plate 13 except that the end of the capacitor 6 is directly inserted into the annular groove formed in the terminal plate 14 with no metallic plate and no spring. Further, three or more insulated rods, of which only two rods 28a and 28b are shown in Fig. 3, are provided for assuring alignment of the capacitor elements. Each of the rods has a threaded end which is fixedly screwed into a threaded hole of the terminal plate 13, as shown in Fig. 3, and another threaded end which is inserted into a through-hole of the terminal plate 14 and fixed by a nut (not shown). The rods are" circumferentially disposed so as to be tightly in contact with the inner surfaces of the capacitor elements thereby assuring alignment of the capacitor elements. It will be understood, however, that any other suitable method may be used for holding the capacitor elements between the terminal plates 13 and 14.

[0011] A modification of the capacitor 6 is shown in Figs. 4 and 5. In this embodiment, the capacitor 6 is constituted by four stacks of capacitor elements 6a, 6b, 6c and 6d circumferentially disposed around the resistor contact 4. Any number of the stacks, however, may be used, as a matter of design choice and may be disposed in any positional relationship so long as they do not adversely affect the resistor contact 4. Fig. 4 shows the junction portion between the terminal plate 13 and each stack. Each of the capacitor element stacks 6a, 6b, 6c and 6d is contained in an insulator tube 24. Four annular grooves 26 are formed in the inner surface of the terminal plate 13 at its circumferential periphery. Each annular groove 26 is formed to have a dimension such that the end portion of the insulator tube 24 can be loosely fitted therein and an island portion 27 encircled by the annular groove 26 facilitates the electrical contact with the capacitor stack 6a-6d. Similarly, annular grooves for receiving the respective capacitor stacks are formed in the terminal plate 14. A spring 25 and a metallic-plate 30 are provided between the island portion 27 and the stack 6a-6d for urging the stack against the terminal plate 14, while no spring and no metallic plate are required at the terminal 14 side.

[0012] In the arrangement of the above-mentioned embodiment, as seen in Fig. 1, a series connection of the resistor 3 and the capacitor 6 is electrically connected in parallel with the breaking contact 1, while each of the capacitor and the resistor is connected in parallel with the main breaking contact in the prior art breaker.

[0013] Generally, the capacitance of the capacitor is selected to be several hundreds to several thousands pico farads (PF) which is sufficiently large relative to the stray capacitance between the main breaking section 1 and the resistor contact 4 and the stray capacitance between the bracket 8 and the earth, which are totally in an order of several tens PF. This capacitance of the capacitor provides an impedance value of about 106 ∿ 10⁷ n with respect to an A.C. high voltage of commercial frequency. The resistor 3 is generally several hundreds n for the pre-insertion purpose. Accordingly, even if the capacitor and the resistor are connected in series with each other, the impedance is not so different from the case where only the capacitor is connected and substantially the same effect can be obtained in voltage distribution.

[0014] As described above, according to the present invention, one porcelain insulator can be reduced for every breaker unit so that an economical circuit breaker of the porcelain insulator type can be produced. Further, it will be easily understood for a skilled person in the art that the present invention is not limited to the embodiments described above but various modifications can be made without deviating from the scope of the invention. For example, the capacitor 6 may be connected to an intermediate portion of the resistor 3, while it is connected between the resistor 3 and the resistor contact 4 in the embodiment described above.

Claims

1. A circuit breaker of the porcelain insulator type provided with a main breaking section having a plurality of series connected breaking contacts (l;la), resistor contact means connected in parallel with each of said breaking contacts and including a series connection of a resistor (3;3a) and a resistor contact (4;4a), and capacitor means (6;6a) connected in parallel with each of said breaking contacts, said circuit breaker comprising:

a first porcelain insulator (2;2a) mounting therein each of said breaking contacts; and

a second porcelain insulator (5;5a) mounting therein said resistor contact means (3,4;3a,4a) and said capacitor means (6;6a) and being disposed in parallel with said first porcelain insulator.

2. A circuit breaker of the porcelain insulator type according to claim 1, in which said main breaking section includes two series connected break ng contacts (l;la); and in which a first breaker unit including a first porcelain insulator (2) mounting therein one (1) of said two breaking contacts and a second porcelain insulator (5) mounting therein said resistor contact means (3,4) and said capacitor means (6) respectively associated with said one breaking contact (1) and a second breaker unit including another first porcelain insulator (2a) mounting therein the other (la) of said two breaking contacts and another second porcelain insulator (5a) mounting therein said resistor contact means (3a,4a) and said capacitor means (6a) respectively associated with said other breaking contact (la) are symmetrically supported by a single upright supporting porcelain insulator.

3. A circuit breaker of the porcelain insulator type according to claim 1, in which said capacitor means (6;6a) is constituted by a plurality of annular capacitor elements (6-1) piled up to form a stack having therein a cylindrical space, and in which said resistor contact (4) of said resistor contact means is disposed in said cylindrical space.

4. A circuit breaker of the porcelain insulator type according to claim 3, in which one end of said resistor (3) is fixed at one end portion of said second porcelain insulator (5) and said resistor contact (4) includes a fixed contact (11) connected to another end of said resistor (3) and a movable contact (12) slidably supported in and electrically connected to an electrically conductive guide tube (17) connected to another end portion of said second porcelain insulator (5), and in which said capacitor means (6) is supported between a first terminal plate (13) fixed and electrically connected to said resistor (3) and a second terminal plate (14) fixed and electrically connected to said guide tube (17).

5. A circuit breaker of the porcelain insulator type according to claim 1, in which said capacitor means (6) includes a plurality of capacitor units (6a,6b,6c,6d), each of said capacitor units being constituted by a plurality of capacitor elements piled up to form a stack, said plurality of capacitor units being disposed so as to form a space surrounded by them said resistor contact (4) of said resistor contact means being disposed in said space.

6. A circuit breaker of the porcelain insulator type according to claim 5, in which one end of said resistor (3) is fixed at one end portion of said second porcelain insulator (5) and said resistor contact (4) includes a fixed contact (11) connected to another end of said resistor (3) and a movable contact (12) slidably supported in and electrically connected to an electrically conductive guide tube (17) connected to another end portion of said second porcelain insulator (5), and in which said capacitor means (6) is supported between a first terminal plate (13) fixed and electrically connected to said resistor (3) and a second terminal plate (14) fixed and electrically connected to said guide tube (17).

Drawing