U.S. patent application number 09/732737 was filed with the patent office on 2001-06-21 for vacuum switch including vacuum-measurement devices, switchgear using the vacuum switch, and operation method thereof.
Invention is credited to Kikukawa, Shuuichi, Kojima, Katsunori, Morita, Ayumu, Tanimizu, Tooru, Tsuji, Masashige.
Application Number | 20010004067 09/732737 |
Document ID | / |
Family ID | 18451722 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010004067 |
Kind Code |
A1 |
Kikukawa, Shuuichi ; et
al. |
June 21, 2001 |
Vacuum switch including vacuum-measurement devices, switchgear
using the vacuum switch, and operation method thereof
Abstract
A vacuum switch is composed by installing a vacuum
circuit-breaker and a disconnector in different grounded vacuum
vessels, respectively, and a vacuum-measurement device is attached
to each grounded vacuum vessel. The above vacuum vessel
communicates with one of the grounded vacuum vessels, and the
degree of vacuum in the vacuum vessel can be directly measured and
monitored.
Inventors: |
Kikukawa, Shuuichi;
(Hitachi-shi, JP) ; Kojima, Katsunori;
(Hitachi-shi, JP) ; Tanimizu, Tooru; (Hitachi-shi,
JP) ; Morita, Ayumu; (Hitachi-shi, JP) ;
Tsuji, Masashige; (Narashino-shi, JP) |
Correspondence
Address: |
MATTINGLY, STANGER & MALUR, P.C.
104 East Hume Avenue
Alexandria
VA
22301
US
|
Family ID: |
18451722 |
Appl. No.: |
09/732737 |
Filed: |
December 11, 2000 |
Current U.S.
Class: |
218/122 |
Current CPC
Class: |
H01H 33/6661 20130101;
H01H 33/666 20130101; H01H 31/003 20130101; H01H 33/6647 20130101;
H01H 33/668 20130101 |
Class at
Publication: |
218/122 |
International
Class: |
H01H 033/66 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 1999 |
JP |
11-356974 |
Claims
What is claimed is:
1. A vacuum switch comprising: grounded vacuum vessels in which a
circuit-breaker portion and a disconnector portion are contained
respectively; and vacuum-measurement devices which are attached to
said grounded vacuum vessels, respectively.
2. A vacuum switch comprising: grounded vacuum vessels in which a
vacuum circuit-breaker portion and a disconnector portion are
contained respectively; vacuum-measurement devices which are
attached to said grounded vacuum vessels, respectively; and vacuum
pumps which are attached to said grounded vacuum vessels,
respectively.
3. A vacuum switch according to one of claims 1 and 2, wherein the
space in a vacuum vessel containing said vacuum circuit-breaker
portion communicates with the space in said grounded vacuum vessel
containing said former vacuum vessel; and the space in said
grounded vacuum vessel containing said disconnector portion is
separated from the space in said grounded vacuum vessel containing
said vacuum circuit-breaker portion.
4. A vacuum switch comprising: a vacuum vessel containing a fixed
electrode, and a movable electrode which is connected to or
disconnected from said fixed electrode, of a circuit-breaker; a
first grounded vacuum vessel, electrically insulated from said
vacuum vessel, which contains said vacuum vessel; a second grounded
vacuum vessel, electrically insulated from said first grounded
vacuum vessel, which contains a disconnector and a grounding
switch; an insulation bushing which is projected from said first
grounded vacuum vessel; a load conductor which is led out of a
bushing of said second grounded vacuum vessel; a grounding
conductor which is led out a bushing of said second grounded vacuum
vessel; first and second vacuum-measurement devices which are
attached to said first and second grounded vacuum vessels,
respectively; a first operating rod for driving a movable blade of
said movable electrode of said circuit-breaker; and a second
operating rod, located substantially in the coaxial direction with
said first operating rod, for driving a movable blade for said
movable electrode of said disconnector.
5. A vacuum switch comprising: a vacuum vessel containing a fixed
electrode, and a movable electrode which is connected to or
disconnected from said fixed electrode, of a circuit-breaker; a
first grounded vacuum vessel, electrically insulated from said
vacuum vessel, which contains and communicates with said vacuum
vessel; a second grounded vacuum vessel, electrically insulated
from said first grounded vacuum vessel, which contains a
disconnector and a grounding switch; an insulation bushing which is
projected from said first grounded vacuum vessel; a load conductor
which is led out of a bushing of said second grounded vacuum
vessel; a grounding conductor which is led out of a bushing of said
second grounded vacuum vessel; first and second vacuum-measurement
devices which are attached to said first and second grounded vacuum
vessels, respectively; a first operating rod for driving a movable
blade of said movable electrode of said circuit-breaker; and a
second operating rod, located substantially in the coaxial
direction with said first operating rod, for driving a movable
blade for said movable electrode of said disconnector.
6. A vacuum switch according to one of claims 4 and 5, wherein a
vacuum pump is connected to each grounded vacuum vessel.
7. A vacuum switchgear comprising: a vacuum switch, in which a
vacuum circuit-breaker and a disconnector are contained in
different grounded vacuum vessels, respectively, including a
vacuum-measurement device attached to each grounded vacuum vessel;
and operation units for driving respective movable electrodes
situated in said vacuum switch.
8. A vacuum switchgear comprising: a vacuum switch, in which a
vacuum circuit-breaker and a disconnector are contained in
different grounded vacuum vessels, respectively, including a
vacuum-measurement device and a vacuum pump attached to each
grounded vacuum vessel; and operation units for driving respective
movable electrodes situated in said vacuum switch.
9. A vacuum switchgear according to one of claims 7 and 8, wherein
the space in a vacuum vessel containing said vacuum circuit-breaker
portion communicates with the space in said grounded vacuum vessel
containing said former vacuum vessel; and the space in said
grounded vacuum vessel containing said disconnector portion is
separated from the space in said grounded vacuum vessel containing
said vacuum circuit-breaker portion.
10. A vacuum switchgear comprising: a vacuum vessel containing a
fixed electrode, and a movable electrode which is connected to or
disconnected from said fixed electrode, of a circuit-breaker; a
first grounded vacuum vessel, electrically insulated from said
vacuum vessel, which contains said vacuum vessel; a second grounded
vacuum vessel, electrically insulated from said first grounded
vacuum vessel, which contains a disconnector and a grounding
switch; an insulation bushing which is projected from said first
grounded vacuum vessel; a load conductor which is led out of a
bushing of said second grounded vacuum vessel; a grounding
conductor which is led out of a bushing of said second grounded
vacuum vessel; first and second vacuum-measurement devices which
are attached to said first and second grounded vacuum vessels,
respectively; a first operating rod for driving a movable blade of
said movable electrode of said circuit-breaker; a second operating
rod, located substantially in the coaxial direction with said first
operating rod, for driving a movable blade for said movable
electrode of said disconnector; operation units, which are
connected to said movable blade connected to said first operating
rod, and said second operating rod, respectively; and a control
unit for controlling said operation units.
11. A vacuum switch comprising: a vacuum vessel containing a fixed
electrode, and a movable electrode which is connected to or
disconnected from said fixed electrode, of a circuit-breaker; a
first grounded vacuum vessel, electrically insulated from said
vacuum vessel, which contains and communicates with said vacuum
vessel; a second grounded vacuum vessel, electrically insulated
from said first grounded vacuum vessel, which contains a
disconnector and a grounding switch; an insulation bushing which is
projected from said first grounded vacuum vessel; a load conductor
which is led out of a bushing of said second grounded vacuum
vessel; a grounding conductor which is led out of a bushing of said
second grounded vacuum vessel; first and second vacuum-measurement
devices which are attached to said first and second grounded vacuum
vessels,respectively; a first operating rod for driving a movable
blade of said movable electrode of said circuit-breaker; a second
operating rod, located substantially in the coaxial direction with
said first operating rod, for driving a movable blade for said
movable electrode of said disconnector; operation units, which
connect to said movable blade connected to said first operating
rod, and said second operating rod, respectively; and a control
unit for controlling said operation units.
12. A vacuum switch according to one of claims 10 and 11, wherein a
vacuum pump is connected to each grounded vacuum vessel.
13. A method of operating a vacuum switch, which includes a vacuum
circuit-breaker and a disconnector, contained in different grounded
vacuum vessels, respectively, including a vacuum-measurement device
and a vacuum pump attached to each grounded vacuum vessel; wherein,
when the degree of vacuum in at least one of said grounded vacuum
vessels deteriorates to less than a predetermined degree, the
degree of vacuum in a corresponding one of, said vacuum vessel
containing said vacuum circuit-breaker and said grounded vacuum
vessels, is increased by operating said vacuum pump of said
corresponding vessel.
14. A method of operating a vacuum switch, which includes a vacuum
circuit-breaker and a disconnector, contained in different grounded
vacuum vessels, respectively, including a vacuum-measurement device
and a vacuum pump attached to each grounded vacuum vessel; wherein
the degree of vacuum in said vacuum switch is continuously
monitored, and when it is necessary that the degree of vacuum in at
least one of said grounded vacuum vessels is increased, the degree
of vacuum in a corresponding one of, said vacuum vessel containing
said vacuum circuit-breaker and said grounded vacuum vessels, is
increased by operating said vacuum pump of said corresponding
vessel.
15. A method of operating a vacuum switch, which includes a vacuum
circuit-breaker and a disconnector, contained in different grounded
vacuum vessels, respectively, including a vacuum-measurement device
and a vacuum pump being attached to each grounded vacuum vessel;
wherein the degree of vacuum in a vacuum switchgear including said
vacuum switch and operation units for driving respective movable
electrodes of said vacuum switch, is continuously monitored, and
when the degree of vacuum in at least one of said grounded vacuum
vessels deteriorates to less than a predetermined degree, the
degree of vacuum in a corresponding one of, said vacuum vessel
containing said vacuum circuit-breaker and said grounded vacuum
vessels, is increased by operating said vacuum pump of said
corresponding vessel.
16. A method of operating a vacuum switch, which includes a vacuum
circuit-breaker and a disconnector, contained in different grounded
vacuum vessels, respectively, including a vacuum-measurement device
and a vacuum pump attached to each grounded vacuum vessel; wherein
the degree of vacuum in a vacuum switchgear including said vacuum
switch and operation units for driving respective movable
electrodes of said vacuum switch, is continuously monitored, and
when it is necessary that the degree of vacuum in at least one of
said grounded vacuum vessels is increased, the degree of vacuum in
a corresponding one of, said vacuum vessel containing said vacuum
circuit-breaker and said grounded vacuum vessels, is increased by
operating said vacuum pump of said corresponding vessel.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a vacuum switch including
vacuum-measurement devices, switchgear using the vacuum switch, and
an operation method thereof.
[0002] The break performance and the withstand-voltage performance
of a vacuum switchgear rapidly deteriorate when the degree of
vacuum decreases to below 10.sup.-4 Torr. Changes in the degree of
vacuum are caused by leakage-in of gas from cracks which have
chapped, discharge of gas molecules which have been absorbed in
metal and insulation members composing a vacuum vessel, penetration
of ambient gas, etc. As the size of a vacuum vessel is increased in
accordance with an increase of the applied voltage, it becomes
unable to disregard the penetration of ambient gas into the vacuum
vessel. It is well known that the degree of vacuum in a vacuum
circuit-breaker is monitored by various means. For example, such
monitoring methods or apparatuses are disclosed in U.S. Pat. No.
5,537,858, U.S. Pat. No. 5,739,419, U.S. Pat. No. 4,163,130,
Japanese Utility Model Application Laid-Open Sho. 55-45160,
Japanese Patent Application Laid-Open Sho. 56-36818, Japanese
Patent Application Laid-Open Hei. 8-306279, etc. In the
contact-type measurement method such as that disclosed in U.S. Pat.
No. 4,163,130, of measuring the degree of vacuum in a vacuum vessel
which is not grounded, in order to elevate the voltage of a
vacuum-measurement device, which is equal to the voltage of a main
circuit, from the ground voltage, a transformer is necessary, and
has not come into practical use yet.
[0003] Further, although the non-contact-type vacuum-measurement
methods for a vacuum vessel are devised in U.S. Pat. No. 5,537,858,
Hei. 8-306279, etc., a method of measuring changes in the degree of
vacuum in a vacuum vessel with the required accuracy has not become
known yet. In Japanese Utility Model Application Laid-Open Sho.
55-45160, although it is not described that the vacuum vessel is
grounded, the system in which a vacuum-measurement device attached
to a second vacuum vessel containing a first vacuum vessel is
disclosed. Further, it is described in this Japanese Utility Model
Application Laid-Open, that a vacuum pump beside a
vacuum-measurement device is connected to the second vacuum vessel.
However, since the first vacuum vessel does not communicate with
the second vacuum vessel, the degree of vacuum in the first vacuum
vessel cannot be directly measured.
[0004] If a vacuum sensor is separated from a main circuit by using
an insulation member, the size of the vacuum sensor, including the
insulation member, is mostly as large as a vacuum valve. Further,
there is a problem in that since electrons generated in the sensor,
then generate secondary electrons while colliding with the
insulation member, that is, they cause electron multiplication, and
these electrons further enter the vacuum valve, the insulation
characteristics of the vacuum valve deteriorates. By setting the
potential of a line connected to a power source equal to that of an
outer cylindrical electrode of the vacuum sensor element, and
applying the voltage, divided by a capacitor, to an inner
cylindrical electrode, it is possible to remove the insulation
member, which in turn downsizes the vacuum sensor. However, the
size of a vacuum measurement device becomes large in the last
results because insulation of the capacitor from the earth is
necessary, and the vacuum measurement device is apt to receive
influences of changes in the voltage of the main circuit (for
example, surge voltage). Further, since the potential of the vacuum
sensor element is equal to that of the line connected to the power
source, an insulation transformer or a light transmission line is
necessary to transmit a signal to a measurement unit, an alarm
lamp, a relay for generating an alarm, etc., and this makes the
measurement system complicated.
SUMMARY OF THE INVENTION
[0005] An objective of the present invention is to provide a vacuum
switch and a vacuum switchgear using the vacuum switch, in which
the vacuum switch is downsized, and its degree of vacuum can be
measured and monitored reliably, by putting a vacuum
circuit-breaker and a disconnector into different grounded vacuum
vessels, respectively, by providing a vacuum measurement device at
each grounded vessel; and its reliability is improved by composing
the vacuum switchgear so that, even if a defect or a malfunction
occurs in the vacuum circuit-breaker and the disconnector, its
effects do not propagate in the whole of the vacuum switch.
[0006] To achieve the above objective, the present invention
provides a vacuum switch comprising: grounded vacuum vessels in
which a vacuum circuit-breaker portion and a disconnector portion
are contained respectively; and vacuum-measurement devices which
are attached to the grounded vacuum vessels, respectively.
[0007] In the present invention, the vacuum circuit-breaker portion
includes indispensable components composing this circuit breaker,
that is: movable and fixed electrodes, conductors supporting these
electrodes, and a vessel containing these components. Further, the
disconnector portion is an apparatus, connected to the
circuit-breaker, for maintaining the circuit-breaker in a
disconnection state when it is required, and it sometimes includes
a grounding switch. Furthermore, it includes a vessel containing
these components.
[0008] Further, it is desirable in order to assure the safety of
workers who inspect and maintain loads or a switchgear, to provide
a function for checking or continuously monitoring the degree of
vacuum in an operation unit, at a structure of a switchgear
according to the present invention, in which a circuit-breaker, a
disconnector, and a grounding switch are integrated in a vacuum
vessel. As a vacuum valve including a vacuum-measurement device, a
vacuum valve using an ionization vacuum gauge, a detector to detect
the degree of vacuum by applying voltage to a small gap provided in
a vacuum vessel to cause discharge in the gap, or a magnetron-type
vacuum-sensing element, are well known. Although all the above
well-known detectors can be used in the present invention, it is
favorable to use an ionization vacuum gauge or a magnetron-type
vacuum-sensing element from the view point of reliability and
accuracy. Also, it is possible to adopt the composition in which a
megger is connected to a measurement element, although this
composition is not suitable for continuous monitoring of the degree
of vacuum. By using this composition, the degree of vacuum can be
measured without a specific power source.
[0009] In the vacuum switch of the present invention, a fixed
electrode and a movable electrode are arranged opposite to each
other in the vacuum vessel from which these electrodes are
insulated with insulation members, and a first vacuum vessel
surrounding this vacuum vessel is provided. Further, a
vacuum-measurement device is attached to the first vacuum vessel.
Further, it is possible that when the degree of vacuum is measured,
a set of coaxial electrodes and a magnetic field-generation unit
surrounding the coaxial electrodes is attached to the first vacuum
vessel which is grounded and in which the fixed electrode and the
movable electrode are arranged opposite to each other; and when the
degree of vacuum is not measured, the set is detached from the
first vacuum vessel. Furthermore, it is desirable to provide a
vacuum pump at the grounded vacuum vessel in order to recover the
degree of vacuum in this vacuum vessel when the vacuum
deteriorates.
[0010] In accordance with the vacuum switchgear of the present
invention, since the vacuum-sensing element can be electrically
separated from the main circuit, the reliability of the function
for measuring or monitoring the degree of vacuum can be improved,
and if the degree of vacuum deteriorates, the vacuum can be
recovered by the vacuum pump, which in turn ensures the safety of
the switchgear. Also, by separating the circuit-breaker portion
from the disconnector portion, it is possible to prevent a
malfunction which has occurred in either the circuit-breaker
portion or the disconnector portion, from propagating in the whole
of the switchgear. Moreover, since the degree of vacuum in the
vacuum vessel containing the circuit-breaker portion can be
directly monitored, the reliability of the circuit-breaker portion
is improved.
[0011] Since the pair of the movable and the fixed electrodes in
the circuit-breaker portion is coaxially arranged with the pair of
the movable and the fixed electrodes in the disconnector portion,
even if a large driving force is applied to these pairs of
electrodes in a disconnecting operation, this driving force can be
absorbed or alleviated by those coaxially arranged components,
which in turn can improve the reliability of the vacuum switch.
Further, since the vacuum vessel is surrounded by the first or
second grounded vacuum vessel, even if a malfunction occurs in the
vacuum vessel, the vacuum vessel can be protected from the
malfunction by the first or second grounded vacuum vessel.
[0012] In accordance with the vacuum switch and the operation
method of the switchgear according to the present invention, by
operating the vacuum pump as the occasion arises, or at will, the
degree of vacuum in not only the grounded vacuum vessels, but also
the vacuum vessel containing the vacuum circuit-breaker, is
improved or maintained at a necessary level, and this can
remarkably improve the performances of the vacuum switch and the
vacuum switchgear. switch and vacuum switchgear using the vacuum
switch.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a vertical cross section of the composition of a
vacuum switch of an embodiment according to the present
invention.
[0014] FIG. 2 is a vertical cross section of the structure of a
vacuum-measurement device used for embodiments according to the
present invention.
[0015] FIG. 3 is a graph indicating the relationship between the
degree of vacuum and the vacuum insulation characteristics.
[0016] FIG. 4 is a schematic diagram of the composition of a
vacuum-measurement device of another embodiment according to the
present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0017] In embodiments of the present invention, a vacuum switch
basically includes a vacuum vessel which contains a fixed electrode
and a movable electrode being connected to, and disconnected from
the fixed electrode, of a circuit-breaker; a first grounded vacuum
vessel which contains the vacuum vessel, being electrically
insulated and communicating with the vacuum vessel; a second
grounded vacuum vessel which contains a disconnector and a
grounding switch, being electrically insulated from the vacuum
vessel and the first grounded vacuum vessel; an insulation bushing
which is projected from the first grounded vacuum vessel; a load
conductor led out of a bushing projected from the second grounded
vacuum vessel; a grounding conductor led out of another bushing
projected from the second grounded vacuum vessel; first and second
vacuum-measurement devices; a first operation rod for driving a
movable blade for the movable electrode of the circuit-breaker; and
a second operation rod, which is situated substantially in the
direction of the axis of the first operation rod, for driving a
movable blade for the movable electrode of the disconnector.
[0018] In the following, embodiment 1 of the present invention will
be explained with reference to FIG. 1. In this figure, the vacuum
switch includes the vacuum vessel 1 containing the movable
electrode 11 and the fixed electrode 10 of the circuit-breaker 9;
the first grounded vacuum vessel 2 containing the vacuum vessel 1;
a vacuum-sensing element 110 attached to the first grounded vacuum
vessel 2; a vacuum pump 91 attached to the first grounded vacuum
vessel 2; and the second grounded vacuum vessel containing the
disconnector 40 and the grounding switch. Most portions of the
vacuum vessel 1 and the first grounded vacuum vessel 2 are made of
conductive material such as a metal with high strength, for
example, stainless steel. Further, the first grounded vacuum vessel
2 is grounded. The portions such as member 7 and 8, other than the
conductive portions, are fabricated with insulation material such
as alumina.
[0019] The vacuum vessel 1 is composed by locating the insulation
member 7 and 8 on and under the side wall of the vacuum vessel 1,
respectively. The fixed electrode 10 and the movable electrode 11
which is disconnectable from the fixed electrode 10, are arranged
in the vacuum vessel 1, and circuit-disconnection or connection is
performed by disconnecting the movable electrode 11 from the fixed
electrode 10, or connecting the movable electrode 11 to the fixed
electrode 10. A movable conductor 15 penetrates the insulation
member 7 connected to the movable electrode 11. Since there is a
narrow gap between the insulation member 7 and the movable
conductor 15, which permits the movement of the movable electrode
11, the vacuum space of the vacuum vessel 1 communicates with that
of the first grounded vacuum vessel 2. Therefore, the
vacuum-sensing element 110 can directly measure or monitor the
degree of vacuum in the vacuum vessel 1 and the first grounded
vacuum vessel 2.
[0020] Another terminal of the movable conductor 15 is connected to
a power source conductor 61 via a flexible conductor 60. This
terminal of the movable conductor 15 is also connected to a link
mechanism of an operation unit via a movable blade 13. The movable
blade 13 is hermetically sealed by a bellows 17.
[0021] The first grounded vacuum vessel 2 is composed of an end
plate 20 and a side wall 29, and the vacuum vessel 1 is surrounded
by a vacuum space 2a. A connection part 81 is connected to a bus
bar (not shown in FIG. 1).
[0022] At the side of the fixed electrode 10, there is the second
grounded vacuum vessel 3 which contains a movable electrode 49 and
a fixed electrode 50 of the disconnector 40, a flexible conductor
74, and movable and fixed electrodes 31 and 32 of a grounding
switch. The first grounded vacuum vessel 2 is hermetically
separated from an insulation member 8. Accordingly, a
vacuum-sensing element 120 and a vacuum pump 90 are attached to the
second grounded vacuum vessel 3, independent of the vacuum-sensing
element 110 and the vacuum pump 91. A movable conductor 45
connected to the movable electrode 49 of the disconnector 40 is
connected to a link mechanism of an operation unit via an
insulation member 43 and a connection member 44.
[0023] The flexible conductor 74 is electrically connected to the
connection part 82 via the load conductor 70.
[0024] FIG. 2 shows a vertical cross section of a magnetron-type
vacuum-measurement device, which is an example of a
vacuum-measurement device used for the embodiments of the present
invention, and a vacuum-sensing element 150 of this measurement
device is attached to the side wall of the first grounded vacuum
vessel 2. The vacuum-sensing element 150 is composed of a pair of
coaxial electrodes 152 and a coil 156, located surrounding the
coaxial electrodes 152, for generating a magnetic flux. The coaxial
electrodes 152 consist of an outer cylindrical electrode 153 and an
inner electrode 153 which is led inside the outer cylindrical
electrode 153, and these electrodes are electrically insulated from
each other. Meanwhile, it is possible to use a ring permanent
magnet in place of the coil 156. Further, even if the direction of
N and S polarities is reversed, the same performance of the
vacuum-sensing element can be obtained.
[0025] Next, the operation of the vacuum-sensing element 150 is
explained below. The negative DC voltage is applied to the inner
electrode 154 by a power source circuit 130. The AC voltage or the
pulse voltage can also be used. Electrons emitted from the inner
electrode 154 receive Lorentz force caused by the electric field E
and the magnetic field B generated by the coil 156, and slew around
the inner electrode 154. The slewing electrons collide with gas
remaining in the vacuum vessel at which the element 150 is
installed, and ionize this gas. Further, the generated positive
ions I move to the inner electrode 154. Since this ion current j
depends on the quantity of the remaining gas, that is, the pressure
of this gas, this gas pressure can be measured by measuring the
voltage between both terminals of a resistor R. Continuous
monitoring of this gas pressure can be implemented by lighting an
alarm lamp or generating an alarm, which are performed with a relay
operated by the voltage V generated between both terminals of the
resistor R. Here, as shown in FIG. 3, the disconnection and
insulation characteristics of the circuit-breaker 9 in the vacuum
vessel 1 rapidly deteriorate if the gas pressure P is more than
10.sup.-4 Torr, it is necessary to monitor the degree of vacuum in
the vacuum vessel so as to prevent the degree of vacuum from
decreasing to below that value (the gas pressure from increasing to
over that value.) Since the above-described magnetron-type
vacuum-sensing element 150 can detect about the pressure of
10.sup.-6 Torr, it is effective enough to monitor the degree of
vacuum in the vacuum vessel.
[0026] Further, since the vacuum-sensing element 150 is attached to
the grounded vacuum vessel 2, a power source circuit 140 of the
vacuum-sensing element 150 can be separated from the main circuit
of the vacuum switchgear. Accordingly, a device for isolating the
vacuum-sensing element 150, for example, a transformer, is not
necessary, and this makes it possible to directly connect the
resistor R to a measurement circuit or a relay circuit. Thus, it
has become possible to downsize and simplify the measurement
system, which in turn can reduce the size of the vacuum switch.
Furthermore, since an erroneous operation of the vacuum-sensing
element 150 due to a surge voltage signal from the main circuit 130
does not occur, the reliability of the sensing element 150 can be
improved. Moreover, since the vacuum-sensing element 150 is
directly attached to the grounded metal vacuum vessel 2, the number
of electrons which enter the vacuum vessel 1 is less than that in
the case where the sensing element 150 is attached to the vessel 2
via an insulation cylinder, and this can prevent the insulation and
shielding characteristics of the vacuum vessel 1 from
deteriorating.
[0027] In addition, since the vacuum pumps 91 and 90 are attached
to the grounded vacuum vessels 2 and 3, respectively, even in the
unlikely event that the degree of vacuum in the vacuum vessel 1,
and the first and second grounded vacuum vessels 2 or 3
deteriorates due to gas discharge from the components in these
vacuum vessels, it can be detected by the vacuum-sensing element
110 or 120, for which the above vacuum-sensing element 150 is
adopted, and the degree of vacuum can be recovered by operating the
vacuum pump 91 or 90.
[0028] The cylindrical side wall la of the vacuum vessel 1 is made
of conductive material such as stainless steel, and is fixed on the
insulation member 8 made of insulation material such as ceramics.
Further, the side wall 1a is supported by the insulation member 7.
A conductor 14 penetrates the central region of the insulation
member 8, and the fixed electrode 10 is connected to the end of the
conductor 14 in the vacuum vessel 1. The movable electrode 11 is
situated opposite to the fixed electrode 10, and these electrodes
compose the circuit-breaker 9. The movable conductor 15 for driving
the movable electrode 11 of the circuit-breaker 9 in the vacuum
vessel 1, is connected to the flexible conductor 60, and to the
movable blade 13 via the insulation member 12. The movable blade 13
is connected to an operation mechanism in an operation unit, and it
drives the movable conductor 15 to reciprocate in accordance with
the operation of the operation mechanism. A control device (not
shown in the figures) is situated in the operation mechanism, and
it generates a signal to operate the circuit-breaker 9. The
connection or disconnection between the movable electrode 11 and
the fixed electrode 10 is implemented by the reciprocation of the
movable conductor 15, which is started by this signal.
[0029] In this way, since the vacuum vessel 1 is contained in the
first grounded vacuum vessel 2, the potential of the vacuum vessel
1 is at an intermediate level between the ground level and the
voltage of the main circuit, and this can prevent the insulation
breakdown which may occur between the vacuum vessel 1 and the first
grounded vacuum vessel 2. Further, since the insulation between the
vacuum vessel 1 and the first grounded vacuum vessel 2 is
maintained, even in the unlikely event that leakage occurs in the
vacuum vessel 1, insulation can sill be maintained.
[0030] The first grounded vacuum vessel 2 containing the vacuum
vessel 1 is arranged coaxial with the vacuum vessel 1. An end plate
20 of a convex shape in the inside and down direction of the vacuum
vessel 2, is welded to the end portion of the vacuum vessel 2.
Also, the vacuum-sensing element 120 for sensing the degree of
vacuum in the second grounded vacuum vessel 3 is attached to the
second grounded vacuum vessel. Further, the vacuum pump 90 is
attached to the side wall of this vacuum vessel 3, and it is
possible to recover the vacuum state by using the vacuum pump
90.
[0031] Both end sides of the bellows 17 are connected to the end
plate 20 and to an end side of the insulation member 12,
respectively, by which the airtight seal of the first grounded
vacuum vessel 2 is maintained. Further, an end side of the flexible
conductor 60 is fixed to a conductor 61. The side wall 39 of the
second grounded vacuum vessel 3 is made of conductive material with
high strength, for example, stainless steel. The second grounded
vacuum vessel 3 is arranged coaxial with the first grounded vacuum
vessel 2. The conductor 14 penetrates the insulation member 8, and
is connected to the side wall 39 via the insulation member 8.
Further, the fixed electrode 50 of the disconnector 40 is situated
on the end side of the conductor 14 in the second grounded vacuum
vessel 3. The movable electrode 49 is arranged opposite to the
fixed electrode 50. The movable blade or conductor 44 is connected
to the movable electrode 49 via the movable conductor 45, the
attachment part of the flexible conductor 74, and the insulation
member 43. Both end sides of a bellows 46 are connected to an end
plate 20 and to an end side of the insulation member 43,
respectively, by which the airtight seal of the second grounded
vacuum vessel 3 is maintained.
[0032] The movable blade 44 is connected to an operation case
containing an operation unit, via a link mechanism, and the
operation unit drives the movable blade 44 to reciprocate. The
connection or disconnection between the movable electrode 49 and
the fixed electrode 50 is implemented by the reciprocation of the
movable blade 44. By closing the circuit-breaker 9 after the
disconnector 40 is closed by slowly applying force to the
disconnector 40, it is possible to approximately balance the force
applied to the movable electrode 11 of the circuit-breaker 9 and
the force applied to the movable electrode 49 of the disconnector
40. Accordingly, the thickness of the insulation member 8 can be
reduced, and its size can also be decreased.
[0033] Moreover, in the grounding switch, the movable electrode 32
is arranged opposite to the fixed electrode 31. The movable
electrode 32 is connected to the movable blade or conductor 33. A
bellows 34 is provided in the cylinder formed by the side wall 39.
One end side of this bellows 34 is connected to the cylinder, and
the other end side of the bellows 34 is connected to the movable
electrode 32 via an insulation member, by which the airtight seal
of the vessel 3 can be maintained. A grounding conductor (not shown
in the figures) is connected to the movable blade 33, and this
conductor is grounded. Also, the movable blade 33 is connected to a
link (not shown in the figures), and the link is further connected
to an operation unit (not shown in the Figures). The fixed
electrode 31 is connected to end sides of a conductor 70 and the
flexible conductor 74. The insulation member 43 is connected to the
movable conductor 45 via another end side of the flexible conductor
74. Further, the end side of the flexible conductor 74 is connected
to the conductor 70. The bushing 71 is provided surrounding the
conductor 70. Furthermore, a load conductor is connected to the
main circuit of the switchgear through an insulation part 82
situated outside the bushing 71.
[0034] The vacuum-sensing element 120 is attached to the side wall
39 of the second grounded vacuum vessel 3.
[0035] Since the vacuum switch is composed so that the first and
second grounded vacuum vessels 2 and 3 are serially arranged in a
line, it has become possible to provide a compact switchgear of
small width. Moreover, since the respective first and second
grounded vacuum vessels 2 and 3 are grounded, and the potential of
their side walls is equal to the ground potential, the respective
switches for three phases can contact each other, or they can be
laid near each other, which in turn makes it possible to provide a
compact switchgear.
[0036] The movable blade 13 is connected to the drive mechanism for
driving this blade to reciprocate, and the fixed electrodes 10 and
50 of the circuit-breaker 9 and the disconnector 40 are connected
to both end sides of the fixed conductor 14, respectively.
Therefore, it is possible to balance the force applied to the
movable electrode 11 of the circuit-breaker 9 and that of the
disconnector 40, and this can reduce the thickness of the
insulation member 8, and the size of the vacuum switch. Also, since
the vacuum switch is composed so that the first grounded vacuum
vessel 2 containing the circuit-breaker 9 is connected to the
second grounded vacuum vessel 3 containing the disconnector 40 and
the grounding switch, the reliability in the insulation
characteristics of the vacuum switch can be improved. Moreover,
since the circuit-breaker 9, the disconnector 40, and the grounding
switch can be separately fabricated, the freedom in composing the
switchgear is increased.
[0037] The spaces inside the respective vacuum-sensing elements 110
and 120 communicate with the spaces inside the respective first and
second grounded vacuum vessels 2 and 3, and the degree of vacuum in
these spaces is continuously measured or monitored. Since the
vacuum pumps 90 and 91 are attached to the respective first and
second grounded vacuum vessels 2 and 3, even in the unlikely event
that the degree of vacuum deteriorates due to discharge of gas from
parts composing the vacuum switch, it is possible to recover the
degree of vacuum in these vessels by detecting the deterioration of
the degree of vacuum with the vacuum-sensing elements 110 and 120,
and operating the pumps 90 and 91. In this way, the safety and
reliability of the vacuum switch can be improved. Thus, the present
invention has remarkable advantages of monitoring the degree of
vacuum in the vacuum switch and improving the performance of the
vacuum switch.
[0038] In a vacuum switch, it is favorable to install a
vacuum-measurement device outside a vacuum vessel containing a
fixed electrode and a movable electrode of a circuit-breaker in
order to prevent metal particles which are emitted from the
electrodes when the electrodes are disconnected, from entering the
vacuum-measurement device. Further, by using magnetic material for
the attachment member of the vacuum-measurement device, the
magnetic reluctance of the vacuum-measurement device can be
decreased.
[0039] As an example of a vacuum-sensing element for the
vacuum-measurement device, a vacuum-sensing element which includes
coaxial electrodes and a magnetic field-generating element, for
sensing the degree of vacuum, can be used.
[0040] Further, it is possible to provide an electrode whose
potential is set equal to an external electrode, which is located
opposite to the inner central electrode of the above vacuum-sensing
element. In the concept of the present invention, there can be
various modifications or improvements such as that indicated by the
above coaxial electrode composed of a cup-type ceramic cylinder
whose inside surface is plated with metal, and the inner central
electrode penetrating the base of the ceramic cylinder.
[0041] Furthermore, a megger can be used as the power source of the
vacuum-sensing element. FIG. 4 shows a schematic diagram of the
composition of the vacuum-measurement device to which a megger is
used for a power source. The vacuum-sensing element of the
vacuum-measurement device 230 is attached to the grounded vacuum
vessel 2. The vacuum-sensing element includes the inner electrode
233 and the outer electrode 234 located surrounding the electrode
233, and both electrodes are insulated from each other by the
insulation member 231. A pair of permanent magnets 237 are arranged
outside the outer electrodes 233. When measuring the degree of
vacuum, the measurement is carried out by connecting the terminal
of the megger 243 to the inner electrode 234 and the vacuum vessel
2, wherein the megger is used as the power source. In this
embodiment, since an independent power source is not necessary, the
measurement device can be simplified, and is safe.
[0042] As described above, in accordance with the present
invention, it has become possible to improve the reliability of
measuring and monitoring the degree of vacuum in a vacuum switch,
and consequently to provide a highly safe vacuum switch and
switchgear.
* * * * *