Vacuum switch and vacuum switchgear using the same

BACKGROUND OF THE INVENTION

The present invention relates to a vacuum switch and a vacuum switchgear using the vacuum switch and, more particularly to a vacuum switch most suitable to be made small in size and a vacuum switchgear using the same.

As incoming transformer apparatuses to be made compact, a SF

6

gas-insulated switchgear is disclosed in JP A 3-273804, for example. In the switchgear, a circuit breaker, two disconnecting switches, and an earth device are individually manufactured and contained in a unit chamber filled with an insulating gas and a bus chamber arranged in a switch box. In the case where a vacuum circuit breaker is used as this circuit breaker, a movable electrode is moved up and down to a fixed electrode to close and open by an operation device of the circuit breaker. There is also a vacuum circuit breaker, as disclosed in JP A 55-143727. In the vacuum circuit breaker a movable electrode is rotated left and right about a main axis as a supporting point to contact with or separate from a fixed electrode, that is, to close or open. Further, there is a switchgear as disclosed in JP A 9-153320, which is constructed so that while a movable conductor arranged in one vacuum container is roundly moving between a fixed conductor and an earth conductor, the movable conductor moves to a close position, an open position, a disconnecting position and an earth position.

Further, JP A 5-166440 and JP A 3-225718 each disclose a vacuum switch constructed so that a vacuum bulb, an operation mechanism for operating the vacuum bulb and a disconnecting device are contained in a hermetically closed metal box or a switch case.

The SF

6

gas insulated-switchgear disclosed in JP A 3-273804 uses a SF

6

gas, so that it is required to reduce the SF

6

gas in view of a greenhouse effect. Therefore, a switchgear in which the SF

6

gas is not used is desired. In the vacuum circuit breaker disclosed in JP A 55-143727, since the container is not grounded, in order to perform maintenance inspection of the incoming transformer apparatuses, it is necessary to take sufficient safety measures such as prevention of re-application of current or voltage from a power source by causing remaining electric charges and induction current to flow into an earth by opening the disconnecting switch provided other than the circuit breaker and grounding the earth switch after opening the circuit breaker. In the circuit breaker, the apparatuses are individually provided, so that it is difficult to make the size of the circuit breaker small. Further, the switchgear disclosed in JP A 9-153320 is excellent in making the size small, however, since the close position, open position, disconnecting position and grounding position are provided in one vacuum container, it has such a disadvantage that all the functions are lost when an accident occurred by any chance. JP A 5-166440 and JP A3-225718 each disclose that the vacuum bulb is contained in the hermetically closed metal box or switch case, however, they do not disclose that the hermetically closed metal box or switch case is made vacuum, and that the hermetically closed metal box or switch case is grounded.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide a vacuum switch which is made small in size and a switchgear using the vacuum switch.

Another object of the present invention is to provide a vacuum switch which can be suited for diversification of apparatuses and a switchgear using the vacuum switch.

Still another object of the present invention is to provide a vacuum switch which is improved in assemblage and a switchgear using the vacuum switch.

Further still another object of the present invention is to provide a vacuum switch which is improved in insulation and a switchgear using the vacuum switch.

In order to attain the above objects, a vacuum switch of the present invention comprises a first vacuum container containing therein a fixed electrode and a movable electrode of a circuit breaker, and a second vacuum container which is electrically insulated from the first vacuum container and grounded and contains therein the first vacuum container. The first vacuum container is communicable in vacuum with the second vacuum container, for example, through a small gap between an insulator forming a part of the first vacuum container and a conductor connected to a fixed or movable conductor and passing through the insulator. Thereby, the vacuum of the two vacuum containers reaches an equilibrium state under normal condition and is stable.

A wall of the first vacuum container containing therein the fixed electrode and the movable electrode of the circuit breaker and a wall of the second vacuum container are arranged at such a distance that the both walls are lower in potential than the potential of a bus, or at a relatively small distance. Particularly, they are arranged to keep such a distance that the potential of the wall of the first vacuum container becomes intermediate potential between the potential of the bus and the earth potential.

The second vacuum container also contains therein an insulator fixed both to the conductor electrically connected to the circuit breaker and to a movable rod for operating the circuit breaker to open and close.

A vacuum switch of the present invention comprises a first vacuum container containing therein a circuit breaker, a second vacuum container containing therein the first vacuum container and grounded, and a third vacuum container connected to the second vacuum container, containing therein a disconnecting switch and grounded. The first vacuum container is communicable in vacuum with the second vacuum container through a gap, however, the vacuum of the third vacuum container is isolated from the vacuum of the first and second vacuum containers.

The second vacuum container also contains therein an insulator fixed both to the conductor electrically connected to the circuit breaker and to a movable rod for operating the circuit breaker to open and close. Further, the disconnecting switch and the circuit breaker, preferably, the insulator fixed to the conductor and the movable rod also are arranged in a substantially straight line.

The vacuum switch is constructed so that a disconnecting switch and an earth device are contained in the third vacuum container. Further, at least one vacuum container containing the first vacuum container is provided between the first and second vacuum containers.

Further, a vacuum switchgear according to the present invention has switches as mentioned above of the number corresponding to three phases or more, and necessary elements such as a protective relay device and an operation box arranged in a metal box.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a sectional side view of a vacuum switchgear of a first embodiment of the present invention;

FIG. 2

is a sectional side view of a mounting construction of a vacuum measurement apparatus used in the vacuum switchgear of the first embodiment of the present invention;

FIG. 3

is a vertical sectional view of a construction of modified vacuum containers used for the vacuum switchgear of

FIG. 1

;

FIG. 4

is a sectional side view of a vacuum switchgear of a second embodiment of the present invention;

FIG. 5

is a sectional side view of a vacuum switchgear of a third embodiment of the present invention; and

FIG. 6

is a lateral sectional view of a construction of an earth device in the third embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

An embodiment of the present invention will be described hereunder, referring to

FIGS. 1

to

3

.

FIG. 1

is a sectional side view of a vacuum switchgear of the present embodiment,

FIG. 2

is a sectional side view of a vacuum measurement apparatus used in the present embodiment, and

FIG. 3

is an enlarged view of a modification of a part of a vacuum switch shown in FIG.

1

.

As shown in

FIG. 1

, a switchgear of the present embodiment has a first vacuum container

1

containing therein a circuit breaker

200

, a second vacuum container

2

containing therein the first vacuum container

1

, and a third vacuum container

3

connected to the second vacuum container

2

through an insulator

8

and a conductive member or ring

9

(which may be made of insulating material) and containing therein an earth device

30

and a disconnecting switch

40

, and each vacuum container is contained in a metal outer casing or box

100

partially shown. The second vacuum container is arranged so as to cover the outer peripheral side of the first vacuum container

1

, keeping a distance which is from the outer peripheral side and set so that a side wall

1

a

of the first vacuum container

1

is intermediate potential lower than the potential of a bus which will be described later. The first vacuum container

1

also can be constructed so as to have a role as an arc shield which will be described later. A conductor

60

inside the second vacuum container

2

is made of a flexible conductor. The flexible conductor

60

is connected to a bushing

63

through a connecting conductor

62

and a fixed conductor

61

, and the fixed conductor is connected to a bus not shown, using a connection portion not shown. The second and third vacuum containers of the number corresponding to three phases are arranged in the metal box

100

. The buses of the number corresponding to three phases are taken out of the vacuum containers. A conductor

70

inside the third vacuum container

3

is connected to a cable

77

through a bushing

71

and a connection portion

72

.

The second and third vacuum containers

2

and

3

each are grounded as mentioned later and the side walls

2

a

3

a

of them are earth potential, so that it is possible to arrange the vacuum containers of three phases in contact with or in an adjacent relation to each other. A box

104

containing therein a protective relay is contained in the metal box

100

partially shown. When the protective relay detects occurrence of an accident or the like, an operation mechanism in an operation box

102

is controlled to control opening and closing of the circuit breaker

200

, earth devices

30

,

50

and disconnecting switch

40

. An operation compartment is constructed by a box accommodating the operation box

102

and the box

104

containing therein the protective relay. Each apparatus of the operation compartment can be arranged adjacent to the vacuum containers because the second vacuum container

2

and the third vacuum container

3

each are earth potential, so that the whole switchgear can be made compact.

The cylindrical side wall

1

a

of the first vacuum container

1

is made of conductive material such as stainless steel. The first vacuum container

1

is composed of the side wall

1

a

and insulators

7

,

8

each made of material such as ceramic and fixed to an end portion of the side wall

1

a,

and it contains therein a movable electrode

11

, a part of a movable conductor

15

, a fixed electrode

10

and a part of a fixed conductor

14

. The movable conductor

15

and the fixed conductor

14

pass through the insulators

7

and

8

, respectively. A small gap necessary for the movable conductor

15

to reciprocate is formed between the movable conductor

15

and the insulator

7

, for example, the small gap is about 2 mm in difference between a hole of the insulator

7

and the diameter of the movable conductor

15

. The first vacuum container

1

and the second vacuum container

2

are communicated with each other through the gap. Such a gap can be provided also between the fixed conductor

14

and the insulator

8

when required. The insulator

8

is fixed to and supported on the second vacuum container

2

by the conductive ring

9

. Further, since the first vacuum chamber

1

is constructed by using the insulators

7

and

8

, the first vacuum container

1

can be fixed to the second vacuum chamber

2

by fixing each of the insulators

7

and

8

to the second vacuum chamber

2

, whereby the strength of support of the first vacuum chamber

1

is improved and the resistance to impact caused by operation of the movable electrode

11

is good. The insulator

8

has the conductor

14

passing through at a central portion thereof, and the conductor

14

has the fixed electrode

10

fixed to an end thereof. The movable electrode

11

is arranged to face the fixed electrode

10

thereby to form a circuit breaker

200

. An end of the movable conductor

15

passing through the insulator

7

is connected to a movable rod

13

for operating the movable electrode

11

inside the first vacuum container

1

, and the movable rod

13

is connected to an operation rod not shown through a link

21

. The operation rod is connected to an operation box

102

containing therein the operation mechanism, and the movable electrode

11

and fixed electrode

10

are contacted or separated by operation of the operation mechanism.

Arc shields

16

a,

16

b

are provided which are connected to the side wall

1

a

between the fixed electrode

10

and the insulator

8

and between the movable electrode

11

and the insulator

7

and on which an insulating material such as ceramic, for example, alumina (Al

2

O

3

), oxide zinc (ZrO

2

) is coated by flame spray coating. An arc shield

16

c

is provided inside the insulator

8

and an arc shield

16

d

is provided inside the insulator

7

. Outer peripheral portions of the arc shields

16

c,

16

d

are positioned a little more outer than the inner peripheral portions of the arc shields

16

a,

16

b

as if arc shields radially extended from inner peripheral portions of the arc shields

16

c,

16

d

to the outer peripheral portions of the arc shields

16

a,

16

b.

The inner surface of the side wall

1

a

is coated with an insulating material such as ceramic, for example, alumina (Al

2

O

3

), oxide zinc (ZrO

2

) by flame spray coating, thereby to be protected from arcs leaked within the arc shields

16

a,

16

b.

Therefore, the first vacuum container

1

can be used as an arc shield. Further, on the outer side of each of the insulators

7

and

8

forming a part of the first vacuum container

1

, a shield

130

,

131

for relaxing electric field is provided to relax the concentration of the electric field.

Since the first vacuum container

1

is contained in the second vacuum container

2

electrically insulated from the first vacuum container

1

and grounded in this manner, the first vacuum container

1

reaches to intermediate potential which is lower than the potential of the bus and higher than the earth potential, whereby it is possible to prevent dielectric breakdown from occurring between the first and second vacuum chambers

1

,

2

. Further, since the vacuum is kept by the first and second vacuum chambers, even if the vacuum of the first vacuum chamber

1

lowers, the insulation can be kept. Further, since the first vacuum chamber

1

and the second vacuum chamber

2

are communicated each other through the gap, it is possible to detect the vacuum of the first vacuum chamber

1

by measuring the vacuum of the second vacuum chamber

2

.

In the above explanation, an example that the second vacuum chamber

2

is arranged outside the first vacuum chamber

1

is described, however, it is possible to provide a fourth vacuum chamber

140

or plural vacuum chambers outside the first vacuum chamber

1

and between the first vacuum chamber

1

and the second vacuum chamber

2

, as shown in FIG.

3

. In this example, the fourth vacuum chamber

140

is connected and fixed to the insulators

7

and

8

. By constructing in this manner, the potential of each vacuum chamber becomes stepped potential at each wall of the first, fourth and second vacuum chambers, and it is possible to make it more uneasy to cause dielectric breakdown. As a result, even if the vacuum switchgear is made high in voltage, the outer diameter of the second vacuum container can be equal to or less than that of a vacuum chamber in the case where a single vacuum chamber is provided, whereby the switchgear can be made compact. Further, even if the degree of vacuum of the vacuum chamber decreases, the vacuum can be kept by a plurality of vacuum chambers, so that the insulation can be maintained.

In the present embodiment, the second vacuum chamber

2

containing therein the first vacuum container

1

is formed in a L-shape, that is, the second vacuum container

2

is composed of a part thereof in which the axis is in the same direction as the axis of the first vacuum container

1

and another part in which the axis is perpendicular to the axis of the first vacuum chamber

1

. The side wall

2

a

of the second vacuum container

2

is made of conductive material such as stainless steel. On the side wall

2

a,

a cylindrical portion

18

is provided, and the cylindrical portion

18

and the movable rod

13

are connected by a bellows

17

to secure airtightness of the second vacuum container

2

. An insulator

12

is provided between the movable conductor

15

passing through the insulator

7

and the movable rod

13

, and a flexible conductor

60

is mounted on the insulator

12

on the side of the first vacuum container

1

. In this manner, since the insulator

12

is provided in the second vacuum container

2

, irrespective of the movable rod

13

being made of metal, it is possible to arrange the movable rod

13

at a position of a small distance from the side wall

2

a

or the bellows

17

, whereby the vacuum switch can be made compact.

To the side wall

2

a,

an end of the flexible conductor

60

is fixed through an insulator

19

. The insulator

19

is arranged on the reverse side to a third vacuum container

3

which will be described later, and in such arrangement, force in the reverse direction to the third vacuum

3

is applied on the conductor by electromagnetic force generated by current flowing in the conductor, however, the force can be supported in the compression direction of the insulator

19

, whereby the durability is improved. The connecting conductor

62

also is mounted on a portion to which the flexible conductor

60

is fixed, and the connecting conductor

62

is connected to the fixed conductor

61

. Both end portions of the flexible conductor

60

are provided with stoppers

132

,

133

, respectively, whereby the flexible conductor

60

is prevented from being bent excessively and the durability thereof is improved.

In the present embodiment, the fixed conductors

61

of the number corresponding to three phases are arranged at different positions in the direction of long axis of the second vacuum container

2

as shown by dotted line illustration, so that in the case where vacuum switches of the number corresponding to three phases are necessary to be arranged in row, each fixed conductor

61

can be wired with straight connecting conductor, and can be connected by simple wiring.

A bushing

63

is mounted on the side wall

2

a

at one end thereof to surround the outer periphery of the fixed conductor

61

and the fixed conductor

61

is connected to the other end of the bushing

63

. The earth device

50

is mounted on one end of the flexible conductor

60

. A fixed electrode

52

of the earth device

50

is mounted, on the side to opposite to the insulator

19

, on the portion fixing the end of the flexible conductor

60

. A movable electrode

51

is arranged to face the fixed electrode

52

, and fixed to a movable rod

53

. A bellows

54

is provided inside a cylindrical portion

55

of the side wall

2

a,

one end of the bellows

54

is connected to the cylindrical portion

55

and the other end is connected to the movable rod

53

through an insulator

59

, whereby the airtightness of the second vacuum container

2

is kept. An earth conductor

58

is mounted on the movable rod

53

, whereby the movable rod

53

is grounded. The movable rod

53

is connected to a link

56

, and the link

56

is connected to an operation mechanism not shown. Operation rods are connected to the links

56

of the number corresponding to three phases, the three phase movable rods

53

are operated in a lump by an operation device not shown. In this manner, the movable rods

53

of the earth device

50

are constructed to reciprocate, so that it is possible to make contacts of the fixed and movable electrodes simple in construction.

To the both ends of the second vacuum container

2

, end plates

20

a,

20

b

each of which is convex inward are fixed by welding. By making the end plate convex, the end plate

20

a,

20

b

can be made thin in thickness and light in weight. On any one of the end plates

20

a,

20

b

grounded, a vacuum measurement apparatus

80

for measuring the degree of vacuum in the second vacuum container

2

is mounted. The vacuum measurement apparatus

80

employs a magnetron type measurement apparatus. As shown in

FIG. 2

, a magnetic member

81

extending near to coaxial electrodes

82

a

is fixed to the end plate

20

a,

and the vacuum measurement apparatus

80

is composed of the coaxial electrodes

82

a

and a coil or ring-shaped permanent magnet

82

b

arranged in a circumference of the coaxial electrodes for generating magnetic field. An inner electrode

82

c

of the coaxial electrodes

82

a

is connected to a power circuit

83

, and a negative direct current is applied on the inner electrode

82

c

by the power circuit

83

. By measuring ion current of anion ions generated by impact ionization with remaining gas by rotating movement of electrons e discharged from the inner electrode

82

c,

the degree of vacuum is measured.

Since the magnetic member

81

extending near to the coaxial electrodes

82

a

is provided as a member other than the end plate

20

a

in this manner, it is possible to prevent magnetic field of the permanent magnet

82

b

from permeating inside the end plate

20

a

and to improve the insulation between the conductor and the grounded container.

The third vacuum container

3

is mounted on the side of the fixed electrode

10

of the circuit breaker. By arranging it in this manner, the operation mechanism for operating the circuit breaker

200

and disconnecting switch

40

is easy to be installed, and the whole switchgear can be made compact. A cylindrical side wall

3

a

of the third vacuum container

3

is made of conductive material such as stainless steel, and the third vacuum container

3

is arranged in the direction that the axis of the third vacuum container

3

crosses the axis of the first vacuum container

1

at right angle and along the axis of the second vacuum container

2

. A fixed electrode

41

of the disconnecting switch

40

is fixed to the conductor

14

on the opposite side to the fixed electrode

10

. A movable electrode

42

is arranged so as to face the fixed electrode

41

. To the movable electrode

42

, a movable rod

44

is connected through a mounting portion of a flexible conductor

74

and an insulator

43

. On the both end portions of the flexible conductor

74

, stoppers

134

,

135

are provided, respectively, whereby the flexible conductor

74

is prevented from being bent excessively and the durability thereof is improved. On the side wall

3

a,

a cylindrical portion

47

is provided, and a bellows

46

is provided inside the cylindrical portion

47

. One end of the bellows

46

is connected to the cylindrical portion

47

and the other end is connected to the movable rod

44

. Since the insulator

43

is provided inside the vacuum container in this manner, irrespective of the moving rod

44

being made of metal, it can be arranged at a small distance from the side wall

3

a

or the bellows

44

and it is possible to make t he size small.

Further, since e the fixed electrode

10

of the circuit breaker

200

and the fixed electrode

41

of the disconnecting switch

40

are provided on the both end portions of the conductor

14

, respectively, by closing the circuit breaker after applying force on the electrode by slowly closing the disconnecting switch

40

, it is possible to balance the force applied on the movable electrode

11

of the circuit breaker and the movable electrode

42

of the disconnecting switch

40

. As a result, impact at time of closing the circuit breaker

200

can be received by the disconnecting switch side. Further, the insulator

8

can be made thin thereby an d the vacuum switch can be made small in size.

A conductor

70

is fixed to the side wall

3

a

through an insulator

75

. The earth device

30

is provided on the conductor

70

, wherein a fixed electrode

31

of the earth device

30

is fixed to the conductor

70

on a reverse side of the conductor

70

to the insulator

75

. The earth device

30

can be omitted. The insulator

75

is provided at a position reverse to the second vacuum container

2

. By arranging in this manner, force is applied on the conductor in a reverse direction to the second vacuum container

2

by electromagnetic force generated by current flowing in the conductor, however, the force can be supported in a compression direction of the insulator

75

, whereby the durability is improved. A movable electrode

32

is arranged so as to face the fixed electrode

31

. The movable electrode

32

is connected to a movable rod

33

. A bellows

34

is provided inside a cylindrical portion

35

of the side wall

3

a.

An end of the bellows

34

is connected to the cylindrical portion

35

and the other end is connected to the moving rod

33

through an insulator

39

, whereby airtightness of the third vacuum container

3

is kept. An earth conductor

36

is connected to the movable rod

33

, and the movable rod

33

is grounded. The movable rod

33

is connected to a link

37

, and the link

37

is connected to an operation mechanism not shown. The links

37

of the number corresponding to three phases are connected by a rod, and operated in a lump by the operation mechanism.

The conductor

70

and flexible conductor

74

are connected to each other at a connecting portion

76

, and a switch

90

is provided between the connecting portion

76

and the earth device

30

. The switch

90

has a fixed electrode

91

and a movable electrode

92

arranged so as to face the fixed electrode

91

. The movable electrode

92

is connected to the movable rod

94

through an insulator

93

. A bellows

96

is provided inside a cylindrical portion

97

of the side wall

3

a,

an end of the bellows

96

is connected to the cylindrical portion

97

and the other end is connected to the movable rod

94

, whereby the airtightness of the third vacuum container

3

is kept. The movable rod

94

is connected to a link

101

, and the link

101

is connected to an operation mechanism not shown. The links

101

of the number corresponding to three phases are connected by an operation rod and operated in a lump. An end of a flexible conductor

95

is connected to the movable electrode

92

and the other end to a fixed conductor

98

. The fixed conductor

98

is connected to, for example, a potential transformer as a potential detector and an arrester. Since the conductor is connected to the potential transformer and arrester through the switch

90

in this manner, it is possible to measure potential in a proper time and improve the resistance to thunder by the arrester.

The conductor

70

is fixed and supported by a bushing

71

made of ceramic and fixed to the side wall

3

a.

The conductor

70

is connected to a cable

77

through the bushing

71

and a connection portion

72

. A current transformer not shown is provided in an outer peripheral side of the cable

77

. The end plate

20

b

of the second vacuum container

2

is arranged so as to have a gap between the cable

77

and the end plate

20

b,

and the cable

77

and the conductor

61

are led out in the same direction. The cable

77

, however, can be led out in the reverse direction to the conductor

61

, whereby freedom of wiring can be increased.

An end plate

78

which is convex toward the inside of the vacuum container is welded and fixed to an end of the third vacuum container

3

on the opposite side to the end portion at which the bushing

71

is provided. On the end plate

78

which is grounded, a vacuum measurement apparatus not shown for measuring the degree of vacuum of the third vacuum container

3

is mounted. The vacuum measurement apparatus, which is similar to the vacuum measurement apparatus

80

, is composed of coaxial electrodes and a coil or ring-shaped permanent magnet arranged in its circumference for generating magnetic field. An inner electrode of the coaxial electrodes is connected to a power circuit. The power circuit applies negative direct current on the inner electrode. In the present embodiment, since the vacuum measurement apparatuses are provided for the second and third vacuum containers

2

,

3

, respectively, the degree of vacuum at time of power supply can be monitored. When the vacuum lowers less than 10

−4

torr, the insulating ability lowers, so that a signal is sent to an alarm device or monitoring device. Here, that the vacuum lowers less than 10

−4

torr means that it becomes 10

−3

torr, for example.

Further, vacuum pump connecting portions can be provided for the second and third vacuum chambers

2

,

3

, whereby when the degree of vacuum lowers, the vacuum can be kept high by operating the vacuum pump or pumps.

An operation of the switchgear constructed in this manner will be described. When power is supplied, the earth devices

30

,

50

are opened and the disconnecting switch

40

, switch

90

and circuit breaker

200

are closed. The power to be supplied from t he b us is supplied to a load side through the bushing

63

, fixed conductor

61

, flexible conductor

60

, movable conductor

15

, movable electrode

11

, fixed electrode

10

, fixed conductor

14

, flexible conductor

74

, conductor

70

and bushing

71

.

In the case where an accident occurs on the bus or load side, a sign al for opening the circuit breaker

200

puts out from a controller by a signal from a detector not shown, and a linear motion of the movable conductor

15

is effected by the operating mechanism. The linear motion of the movable conductor

15

shifts the movable electrode

11

from a closing state to an open state, thereby to break the circuit. At this time, arcs occur between the fixed electrode

10

and the movable electrode

11

, however, most of the arcs are shielded by the arc shields

16

a

to

16

d

provided inside the first vacuum container

1

, and the side wall

1

a

is protected from arcs. The side wall portion subjected to arcs leaked inside the arc shields

16

a,

16

b

of a linearly moving portion of the movable electrode

15

is protected from the arcs by the coating of insulating material formed by flame spray coating. when the circuit breaker

200

is opened, the movable rod

44

of the disconnecting switch

40

is shifted by the operation mechanism according to a control signal from the controller so that the movable electrode

42

is separated from the fixed electrode

41

and the disconnecting switch

40

becomes a disconnected state. Then, the movable rod

33

of the earth device

30

is shifted so that the movable electrode

32

contacts with the fixed electrode

31

, whereby the conductor is grounded. Further, the movable rod

53

of the earth device

50

is shifted so that the movable electrode

51

is contacted with the fixed electrode

52

to effect grounding.

Since the vacuum switch is constructed in a laterally-laid-U shape by the L-shaped second vacuum container and the third vacuum container, a bus side unit and a transformer side unit can be made common. Further, the vacuum switches can be arranged parallel, whereby a compact switchgear can be provided.

Since the movable rod

13

for the circuit breaker

200

is constructed of a driving system reciprocating the movable rod

13

and the fixed electrode

10

of the circuit breaker and the fixed electrode

41

of the disconnecting switch are arranged at both ends of the fixed conductor

14

, the force applied on the movable electrode

11

of the circuit breaker and the force applied on the movable electrode

42

of the disconnecting switch can be balanced, so that the thickness of the insulator

8

can be formed thin and made small in size. Further, the first vacuum container

1

containing therein the circuit breaker

200

and the third vacuum container

3

containing therein the disconnecting switch

40

and earth device

30

are constructed so that they are connected each other, the insulation reliability is improved. Further, the disconnecting switch and the earth device can be assembled individually from the circuit breaker, so that the freedom of constructing the switchgear increases.

The space in the vacuum measurement apparatus communicates with the vacuum container and the vacuum of the vacuum container is measured or always monitored by the vacuum measurement apparatus, whereby the safety and reliability of the vacuum switch can be improved.

Since the first vacuum container

1

containing the circuit breaker

200

and the second vacuum container

2

are communicated with each other and the second vacuum container

2

and the third vacuum container

3

are interrupted in vacuum, in the case where any disadvantage occurs in the first and second vacuum containers the circuit breaker can be opened, and in the case where any disadvantage occurs in the third vacuum container the circuit breaker can be opened, so that the safety is improved.

A second embodiment of the present invention will be described hereunder, referring to FIG.

4

.

FIG. 4

is a sectional side view of a vacuum switch of the second embodiment.

The vacuum switch of the present embodiment is constructed as follows. Here, parts or components having a function the same as or similar to those of the first embodiment are given the same reference numbers.

A first vacuum container

1

comprises a cylindrical side wall

1

a

and insulators

7

,

8

fixed to end portions of the cylindrical side wall

1

a

which is made of conductive material such as stainless steel or the like. The insulators

7

,

8

each are made of, for example, ceramic. The insulator

8

is fixed and supported to a second vacuum container

2

through a conductive or insulating ring

9

, whereby the first vacuum container

1

is supported by the second vacuum container

2

. The first vacuum container

1

also can be fixed to the second vacuum container

2

by both the insulators

7

and

8

as described in the first embodiment. A fixed conductor

14

is provided at a central portion of the insulator

8

, and a fixed electrode

10

is fixed to an end of the conductor

14

inside the first vacuum container

1

. A movable electrode

11

is provided so as to face the fixed electrode

10

to construct a circuit breaker

200

. A movable conductor

15

has the movable electrode

11

fixed thereto at one end and operates the movable electrode

11

of the circuit breaker in the first vacuum container

1

. The movable conductor

15

passes through the insulator

7

and is connected to a flexible conductor

60

and to a movable rod

13

through an insulator

12

. The movable rod

13

is connected to an operation box

102

containing therein an operation mechanism and causes the movable conductor

15

to reciprocate by an operation of the operation mechanism. Reciprocation of the movable conductor

15

causes the movable electrode

11

to contact with or separate from the fixed electrode

10

.

Arc shields

16

a,

16

b

each coated with ceramic by flame spray coating are provided between the fixed electrode

10

and the insulator

8

and between the movable electrode

11

and the insulator

7

. An arc shield

16

c

is provided inside the first container

1

on the inner side of the insulator

8

, and an arc shield

16

d

also is provided inside the first vacuum container

1

on the inner side of the insulator

7

. Outer peripheral portions of the arc shields

16

c,

16

d

are positioned radially at positions a little more outer than the inner peripheral portions of the arc shields

16

a,

16

b

as if arc shield extended from the electrodes to the side wall

1

a.

An inner surface of the side wall

1

a

is coated with ceramic by flame spray coating and protected from arcs leaking inside the arc shields

16

a,

16

b.

The second vacuum container

2

containing the first vacuum container

1

is arranged so that the axis of the second vacuum container

2

is in the same direction as the axis of the first vacuum container

1

. When the first vacuum container

1

communicates with the second vacuum container

2

and the second vacuum container

2

and a third vacuum container

3

are isolated from each other with respect to vacuum, it is possible to contain the first vacuum container

1

inside the third vacuum container

3

or to contain a part of the first vacuum container

1

in one of the second and third vacuum containers

1

,

2

and the other part in the other of the vacuum containers

1

,

2

. The second vacuum container

2

is arranged so as to surround the outer periphery of the first vacuum container

1

at the distance set so that the side wall

1

a

of the first vacuum container

1

becomes intermediate potential. An end plate

20

which is convex toward the outside of the vacuum container is welded and fixed to one end of the second vacuum container

2

. A vacuum measurement apparatus not shown for measuring the degree of vacuum of the second vacuum container

2

is mounted on the end plate

20

. The vacuum measurement apparatus is constructed as shown in FIG.

2

. The insulator

12

is provided between the movable conductor

15

passing through the insulator

7

and a bellows

17

, and a flexible conductor

60

is provided on the insulator

12

on the side of the first vacuum container

1

. Further, the insulator

12

is connected to an end of a movable rod

13

the other end of which passes through the end plate

20

to be out of the vacuum container. The end plate

20

and an end of the insulator

12

are connected by the bellows

17

surrounding the movable rod

13

to maintain the airtightness of the second vacuum container

2

. Since the insulator

12

is provided inside the vacuum container in this manner, the movable rod

13

can be arranged at a small distance from the side wall

2

a

or the bellows

17

irrespective of the movable rod

13

being made of metal, whereby the size can be made small. An insulator

66

is provided on the side wall

2

a,

and an end of the flexible conductor

60

is fixed to a conductor

61

passing through the insulator

66

and fixed thereto. A shield

67

for relaxing electric field is provided on the insulator

66

on the side of the first vacuum container

1

to relax the concentration of electric field. A bushing

63

is provided on th e side wall

2

a

in the circumference of the conductor

61

and the conductor

61

is connected to a conductor on the side of a bus.

Since the first vacuum container

1

is contained in the second vacuum container

2

which is electrically insulated from the first vacuum container

1

and grounded in this manner, the first vacuum container

1

is intermediate potential lower than the potential of the bus and higher than the earth potential, whereby it is possible to prevent dielectric breakdown from occurring between the first and second vacuum containers

1

and

2

. Further, since the vacuum is maintained by the first and second vacuum containers

1

and

2

, the insulation can be maintained even if the degree of vacuum of the first vacuum container

1

decreases.

In the above explanation, an example that the second vacuum container

2

is provided outside the first vacuum container

1

is described, however, as shown in

FIG. 3

, a fourth vacuum container

140

or containers can be provided outside the first vacuum container

1

and between the first and second vacuum containers

1

and

2

.

The third vacuum container

3

is mounted on the circuit breaker on the side of the fixed electrode

10

. The cylindrical side wall

3

a

of the third grounded vacuum container

3

is made of conductive material such as stainless steel, and the third vacuum container

3

is arranged so that the axis of the third vacuum container

3

is in the same direction as the axis of the second vacuum container

2

. The conductor

14

passed through the insulator

8

is connected to the side wall

3

a

through an insulator

75

, and a fixed electrode

31

of an earth device

30

is provided on the opposite side to the insulator

75

. A movable electrode

32

is provided so as to face the fixed electrode

31

. The movable electrode

32

is connected to an movable rod

33

. A bellows

34

is provided inside a cylindrical portion

35

of the side wall

3

a,

an end of the bellows

34

is connected to the cylindrical portion

35

and the other end to the movable rod

33

through an insulator

39

, whereby the airtightness of the third vacuum container

3

is kept. An earth conductor not shown is mounted on the movable rod

33

, whereby the movable rod

33

is grounded. The movable rod

33

is connected to a link not shown, the link is connected to an operation mechanism contained in an operation box

102

. The arrangement can be reverse. Since the insulator

39

is provided within the vacuum container, it is possible to arrange the movable rod

33

at a small distance from the side wall

3

a

or bellows

34

irrespective of the movable rod

33

made of metal and the size can be made small.

A flexible conductor

74

is connected to the conductor

14

, and a disconnecting switch

40

is provided on an end of the flexible conductor

74

. The flexible conductor

74

is connected to the movable electrode

42

and the movable electrode

42

is connected to a movable rod

44

through an insulator

43

. The side wall

3

a

is provided with a cylindrical portion

47

, and a bellows

46

is connected to the cylindrical portion

47

and an end of the insulator

43

to maintain the airtightness of the third vacuum container

3

. The movable rod

44

is connected to an operation mechanism not shown through a link not shown. Since the insulator

43

is provided inside the vacuum container in this manner, it is possible to arrange the movable rod

44

at a small distance from the side wall

2

a

or bellows

46

irrespective of the movable rod

44

made of metal, and the size cam be made small. The fixed electrode

41

is arranged so as to face the movable electrode

42

. A conductor

70

connected to the fixed electrode

41

is provided passing through an insulator

106

fixed to the side wall

3

a,

and fixed and supported by the insulator

106

. A bushing

71

is provided in the outer periphery side of the conductor

70

. The bushing

71

is arranged in the same direction as a bushing

63

and the conductor is connected to the negative side.

Since the insulators

66

,

106

are provided in this manner, although such force as to expand between the conductor

70

and conductor

61

is applied on the conductors

70

and

61

by electromagnetic force generated by current flowing the conductors, the insulators

66

and

106

can receive the force.

A fixed electrode

91

of a switch

90

is connected to the fixed electrode

41

of the disconnecting switch

40

, and a movable electrode

92

is provided so as to face the fixed electrode

91

. A movable rod

94

is connected to the movable electrode

92

through a mounting portion of a flexible conductor

95

and an insulator

93

. The side wall

3

a

is provided with a cylindrical portion

97

, and a bellows

96

is provided inside the cylindrical portion

97

. An end of the bellows

96

is connected to the cylindrical portion

97

and the other end to the movable rod

94

to maintain the airtightness of the third vacuum container

3

. Since the insulator

93

is provided inside the vacuum container in this manner, the movable rod

94

can be arranged in a small distance from the side wall

3

a

or bellows

96

irrespective of the movable rod

94

made of metal, and the size can be made small.

A conductor

98

connected to the flexible conductor

95

is fixed and supported by a bushing

99

made of ceramic and fixed to the side wall

3

a.

A connection portion not shown is provided outside the bushing

99

, the conductor is connected to a potential transformer and an arrester by the connection portion.

A vacuum measurement apparatus

80

for measuring the degree of vacuum of the third vacuum container

3

is mounted on a lateral side of the side wall

3

a

that the bushing

99

of the third vacuum container

3

is provided. The vacuum measurement apparatus

80

is composed of coaxial electrodes and a coil or ring-shaped permanent magnet arranged in the peripheral portion for generating magnetic field, as shown in FIG.

2

. An inner electrode of the coaxial electrodes is connected to a power circuit and applied with negative current voltage by the power circuit. Further, it is possible to provide a connection portion or portions of a vacuum pump or pumps on the second and third vacuum containers

2

,

3

, whereby when the vacuum decreases, the vacuum can be kept high by operation of the vacuum pumps.

Since the second vacuum container

2

and the third vacuum container

3

are linearly arranged to construct vacuum switch in this manner, a switchgear the depth (the size in a direction perpendicular to a long axis of the vacuum switch) of which is small can be provided. Further, since the second and third containers

2

,

3

are grounded and the side walls

2

a,

3

a

become earth potential, it is possible to arrange the switches of three phases at a contacting or adjacent relation to each other, whereby a compact switchgear can be provided. Further, by arranging the operation mechanism for operating the switches of three phases in a lump within the width of the vacuum switches of the number corresponding to three phases, arranged in an adjacent relation with each other, it is possible to arrange plural sets of the vacuum switches of three phases thereby to arrange switches of the number corresponding to 6 phases or more.

Further, the first vacuum container containing therein the circuit breaker and the third vacuum container containing therein the disconnecting switch and earth device are constructed so that they are connected to each other, the insulation reliability is improved. Further, the circuit breaker, the disconnecting switch and the earth device can be assembled individually, so that the freedom of constructing the switchgear increases.

The space in the vacuum measurement apparatus communicates with the vacuum container and the vacuum of the vacuum container is measured or always monitored by the vacuum measurement apparatus, whereby the safety and reliability of the vacuum switch can be improved.

The above-mentioned vacuum switches of the number corresponding to three phases or more and the operation box

102

, a protective relay box, etc. are contained in a metal box

100

, thereby to from a switchgear.

A third embodiment of the present invention will be described hereunder, referring to

FIGS. 5 and 6

.

FIG. 5

is a side-sectional view of a vacuum switch of the third embodiment and

FIG. 6

is a lateral sectional view of an earth device.

The vacuum switch of the present embodiment is constructed as follows. Here, parts or components having a function the same as or similar to those of the first embodiment are given the same reference numbers.

A cylindrical side wall

1

a

of a first vacuum container

1

is formed of conductive material such as stainless steel or the like, the side wall

1

a

is fixed and supported by a portion of an insulator

8

made of, for example, ceramic and supported by a portion of an insulator

7

. The insulator

8

is fixed and supported to a second vacuum container

2

. The first vacuum container

1

can be fixed to the second vacuum container

2

by both the insulator

7

and the insulator

8

as described in the first embodiment. A conductor

14

is provided at a central portion of the insulator

8

, and a fixed electrode

10

is provided on the conductor

14

inside the first vacuum container

1

. A movable electrode

11

is provided so as to face the fixed electrode

10

to construct a circuit breaker

200

. A movable conductor

15

operating the movable electrode

11

of the circuit breaker

200

in the first vacuum container

1

passes through the insulator

7

and is connected to a flexible rod

13

through an insulator

12

. The movable rod

13

is connected to an operation box

102

containing therein an operation mechanism and causes the movable conductor

15

to reciprocate by an operation of the operation mechanism. Reciprocation of the movable conductor

15

causes the movable electrode

11

to contact with or separate from the fixed electrode

10

.

An arc shield

16

c

coated with ceramic by flame spray coating is provided inside the first container

1

on the inner side of the insulator

8

, and an arc shield

16

d

also is provided inside the first vacuum container

1

on the inner side of the insulator

7

. An inner surface of the side wall

1

a

is coated with ceramic by flame spray coating and protected from arcs.

In the present embodiment, arc shields

16

a,

16

b

are omitted by making the diameter of the electrodes large thereby to make the arc sufficiently stable. Since the arc shields

16

a,

16

b

are not provided in this manner, the axial length of the first vacuum container

1

can be made short. As a result, the volume of the first vacuum container

1

can be made small, so that it is easy to maintain the vacuum.

The second vacuum container

2

containing the first vacuum container

1

is arranged so that the axis of the second vacuum container

2

is in the same direction as the axis of the first vacuum container

1

. The first vacuum container

1

is contained in a third vacuum container

3

as in the second embodiment, or it is possible to contain the first vacuum container

1

in both the second and third vacuum containers so that a part of the first vacuum container is in the second vacuum container and the other part in the third vacuum container. The second vacuum container

2

is arranged so as to surround the outer periphery of the first vacuum container

1

at the distance set so that the side wall

1

a

of the first vacuum container

1

reaches to intermediate potential. An end plate

20

which is convex toward the inside of the vacuum container is welded and fixed to one end of the second vacuum container

2

. A vacuum measurement apparatus

80

for measuring the degree of vacuum of the second vacuum container

2

is mounted on the second vacuum container

2

. The vacuum measurement apparatus is constructed as shown in FIG.

2

. Further, a connection portion

136

to a vacuum pump not shown is provided. An insulator

12

is provided between a movable conductor

15

passing through the insulator

7

and a bellows

17

, and a flexible conductor

60

is provided on an insulator

12

on the side of the first vacuum container

1

. The end plate

20

and an end of the insulator

12

are connected by the bellows

17

to maintain the airtightness of the second vacuum container

2

. Since the insulator

12

is provided inside the vacuum container in this manner, a movable conductor

15

can be arranged at a small distance from the side wall

2

a

or the bellows

17

irrespective of the movable rod

13

made of metal, whereby the size can be made small. An insulator

66

is provided on the side wall

2

a,

and an end of the flexible conductor

60

is fixed to a conductor

61

passing through the insulator

66

and fixed thereto. The flexible conductor

60

is bent at right angle and an axial direction of the conductor

61

is arranged in a direction perpendicular to the axial direction of the first vacuum container

1

. Therefore, the depth of the container can be made small. A shield

67

for relaxing the electric field is provided on the insulator

66

on the side of the first vacuum container

1

. A bushing

63

is provided on the side wall

2

a

in an outer peripheral side of the conductor

61

and the conductor

61

is connected to a bus arranged on the upper side.

Since the first vacuum container

1

is contained in the vacuum container

2

which is electrically separated from the first vacuum container

1

and grounded in this manner, the first vacuum container

1

becomes intermediate potential which is lower than the potential of the bus and higher than the earth potential, whereby it is possible to prevent dielectric breakdown from occurring between the first and second vacuum containers

1

and

2

. Further, since the vacuum is maintained by the first and second vacuum containers

1

and

2

, the insulation can be maintained even if the degree of vacuum of the first vacuum container

1

decreases. In the above explanation, the example that the second vacuum container

2

is provided outside the first vacuum container

1

is described, however, as shown in

FIG. 3

, a fourth vacuum container

140

or containers can be provided outside the first vacuum container

1

and between the first and second vacuum containers

1

and

2

.

The third vacuum container

3

is mounted on the circuit breaker on the side of the fixed electrode

10

. The cylindrical side wall

3

a

of the third grounded vacuum container

3

is made of conductive material such as stainless steel, and the third vacuum container

3

is arranged so that the axis of the third vacuum container

3

is in the same direction as the axis of the second vacuum container

2

. A conductor

14

passed through the insulator

8

is connected to the side wall

3

a,

and a fixed electrode

41

of a disconnecting switch

40

is provided on the conductor

14

on the side of the third vacuum container

3

. A movable electrode

42

is arranged to face the fixed electrode

41

. A movable rod

44

is connected to the movable electrode

42

through a movable conductor

45

, a connection portion of a flexible conductor

74

and an insulator

43

. An end plate

78

and an end of the insulator

43

are connected by a bellows

46

to maintain the air tightness of the third vacuum container

3

. The movable rod

44

is connected to an operation box

103

containing an operation mechanism, the rod

44

is driven to reciprocate by an operation of the operation mechanism. Reciprocation of the movable rod

44

causes the movable electrode

42

and the fixed electrode

41

to contact with and separate from each other. Since the fixed electrode

10

of the circuit breaker and the fixed electrode

41

of the disconnecting switch

40

are provided on the both ends of the conductor

14

in this manner, after the disconnecting switch

40

is slowly closed and force is applied, the circuit breaker is closed, whereby the force applied on the movable electrode

11

of the circuit breaker can be balanced with the movable electrode

42

of the disconnecting switch

40

, the insulator

8

can be made thin and the size can be made small.

An earth device

30

provided at the position of an connection portion of the insulator

43

and the movable conductor

45

is constructed as shown in

FIG. 6. A

fixed electrode

31

is provided on a conductor

38

arranged so as to surround the insulator

43

and connected to a conductor

70

described later at a position reverse to the conductor

70

. A movable electrode

32

is arranged so as to face the fixed electrode

31

. The movable electrode

32

is connected to a movable rod

33

through an insulator

39

. A bellows

34

is provided inside a cylindrical portion

35

of the side wall

3

a,

an end of the bellows

34

is connected to the cylindrical portion

35

and the other end to the movable rod

33

through an insulator

39

, whereby the airtightness of the third vacuum container

3

is kept. Since the insulator

39

is provided inside the vacuum container, it is possible to arrange it at a small distance from the side wall

3

a

or the bellows

34

irrespective of the movable rod being made of metal. An earth conductor not shown is mounted on the movable rod

33

, whereby the movable rod

33

is grounded. The movable rod

33

is connected to a link not shown, and the link is connected to an operation mechanism not shown. the insulator

43

and the movable conductor

45

are arranged so as to pass through the conductor

38

. An end of a flexible conductor

74

is connected to the movable conductor

45

and the other end to the conductor

70

. The flexible conductor

74

is formed bent at right angle, and the conductor

70

is arranged in the direction that the axial direction thereof crosses the axial direction of the first vacuum conductor

1

at right angle. Therefore, the depth size can be made small. The conductor

70

is provided passing through an insulator

106

fixed to the side wall

3

a,

and fixed and supported by the insulator

106

. A bushing

71

is provided in the outer periphery side of the conductor

70

. The bushing

71

is connected to a cable

77

through a connection portion

72

. Since the insulators

66

,

106

are provided in this manner, although force so as to expand between the conductor

70

and conductor

61

is applied on the conductors

70

and

61

by electromagnetic force generated by current flowing in the conductors, the insulators

66

and

106

can receive the force.

A vacuum measurement apparatus

80

for measuring the degree of vacuum of the third vacuum container

3

is mounted on a lateral side of the side wall

3

a.

The vacuum measurement apparatus

80

is composed of coaxial electrodes and a coil or a ring-shaped permanent magnet arranged in the peripheral portion for generating the magnetic field, like the vacuum measurement apparatus

80

shown in FIG.

2

. An inner electrode of the coaxial electrodes is connected to a power circuit and applied with negative current voltage by the power circuit. Further, a connection portion

137

to a vacuum pump is provided.

In this example, the example that the operation boxes

102

,

103

are arranged sidewards of the second and third vacuum containers

2

,

3

, respectively, however, the operation boxes

102

,

103

can be arranged under the second vacuum container

2

and over the third vacuum container

3

, and by such an arrangement, the vacuum measurement apparatus and the operation mechanism of the earth device

30

can be arranged sidewards of the second and third vacuum containers and the whole apparatus can be made compact. Further, the operation mechanism can be arranged within the width the vacuum switches of the number corresponding to three phases, whereby it is possible to arrange plural sets of the vacuum switches of six phases or more. Further, although not shown, a potential transformer, a conductor connected with an arrester, and an switch can be provided in the second vacuum container

2

.

The switchgear comprises the vacuum switches, the operation boxes

102

,

103

and protective relay box

104

, each contained in a metal box

100

.

Since the second and third vacuum containers are linearly arranged to construct the vacuum switchgear in this manner, the switchgear the depth of which is small can be provided. Further, the second and third vacuum containers

2

,

3

are grounded and the side wall is earth potential, so that switches of the number corresponding to three phases can be arranged closely to each other and a compact switchgear can be provided.

Further, since the fixed electrode of the circuit breaker and the fixed electrode of the disconnecting switch are arranged at the both ends of the fixed conductor in a driving system reciprocating the movable rod of the circuit breaker, the force applied on the movable electrode of the circuit breaker and the force applied on the movable electrode of the disconnecting switch can be balanced, so that the insulator

8

can be formed thin and the switchgear can be made small in size. Further, the first vacuum container containing therein the circuit breaker and the third vacuum container containing therein the disconnecting switch and earth device are constructed so that they are connected to each other, the insulation reliability is improved. Further, the circuit breaker, the disconnecting switch and the earth device can be assembled individually, so that the freedom of constructing the switchgear increases.

The space of the vacuum measurement apparatus communicates with the vacuum container and the vacuum of the vacuum container is measured or always monitored by the vacuum measurement apparatus, whereby the safety and reliability of the vacuum switch can be improved.

As mentioned above, the vacuum switches of each embodiment and the switchgear using the switches have the following effects.

Since the first vacuum container

1

is contained in the second vacuum container

2

which is electrically separated from the first vacuum container

1

and grounded, the first vacuum container

1

becomes intermediate potential between potential of the bus and the earth potential, whereby it is possible to prevent dielectric breakdown from occurring between the first and second vacuum containers. Further, the vacuum is maintained by the first and second vacuum containers, so that the insulation can be maintained even if the vacuum of the first vacuum container lowers.

The vacuum switches can be arranged in parallel, so that a compact switchgear can be provided. Further, since the fixed electrode of the circuit breaker and the fixed electrode of the disconnecting switch are arranged at the both ends of the fixed conductor in a driving system reciprocating the movable rod of the circuit breaker, the force applied on the movable electrode of the circuit breaker and the force applied on the movable electrode of the disconnecting switch can be balanced, so that the insulator

8

can be formed thin and the switchgear can be made small in size.

Further, the first vacuum container containing therein the circuit breaker and the third vacuum container containing therein the disconnecting switch and earth device are constructed so that they are connected each other, the insulation reliability is improved. Further, the circuit breaker, the disconnecting switch and the earth device can be assembled individually, so that the freedom of constructing the switchgear increases.

The space of the vacuum measurement apparatus communicates with the vacuum container and the vacuum of the vacuum container is measured or always monitored by the vacuum measurement apparatus, at the same time, the vacuum is maintained by the vacuum pump, so that the safety and reliability of the vacuum switch can be improved.

Number	Name	Date	Kind
4087644	Weston	May 1978	A
6335502	Kikukawa et al.	Jan 2002	B1

Vacuum switch and vacuum switchgear using the same

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Foreign Referenced Citations (5)

Number	Date	Country
55-143727	Nov 1980	JP
3-225718	Oct 1991	JP
3-273804	Dec 1991	JP
5-166440	Jul 1993	JP
9-153320	Jun 1997	JP