Title of the invention
Vacuum insulated switching apparatus
Background of the invention
The present invention relates to a vacuum insulated switching
apparatus provided with a vacuum pressure measuring device.
Switching performance and dielectric strength of a vacuum
bulb is decreased rapidly when vacuum pressure is increased higher
than 104 Torr. Reasons of varying the vacuum pressure are such as
vacuum leakage by generating cracks, release of gaseous molecules
adsorbed onto metals and insulating materials, penetration of
atmospheric gases, and others. In accordance with increasing size of
the vacuum vessel accompanied with increasing the voltage of the
vacuum bulb, the release of the adsorbed gas, and the penetration of
atmospheric gas become not negligible. In accordance with a
structure of the insulated switching apparatus as disclosed in JP-A-9-
249076 (1997), wherein a breaker, a disconnector, and a ground switch
are integrated in a single bulb, an addition of vacuum pressure
checking function during operation, or of continuous pressure
monitoring function is desirable, in order to ensure safety of operators
for maintenance and inspection of load, or switching apparatus itself.
Conventionally, vacuum bulbs provided with vacuum pressure
measuring apparatus such as the one provided with an ionization
vacuum gauge, the one of which vacuum pressure is determined by
applying a voltage to a small gap provided in the vacuum vessel to
cause discharge, the one provided with a magnetron terminal, and
others are known.
Summary of the invention
When considering insulation between a main circuit and a
measuring terminal in the prior art, some problems occur as described
below. If the measuring terminal is composed with an insulating
cylinder separately from the main circuit, the size of the measuring
terminal including the insulating cylinder becomes as large as equal to
the size of the vacuum bulb. Furthermore, electrons e generated at
the measuring terminal entered into inside the vacuum bulb with
colliding with the insulating cylinder, that is, in an electron multiplied
state by generating secondary electrons. Therefore, deterioration of
the insulating performance of the vacuum bulb was a problem.
In accordance with one of the prior art, the size of the
measuring terminal could be small by making the insulating cylinder
unnecessary with a method, wherein a line at power source side and
an outer cylindrical electrode of the vacuum pressure measuring
element were maintained at an equal potential and a voltage divided
with a condenser was applied to an interior electrode. However,
problems were caused such as increasing size of the apparatus large
eventually if insulation of the condenser with ground was considered,
and further, receiving an influence of variation in voltage of the main
circuit (for instance, a surge voltage and the like). Because the
potential of the measuring element was equal to that of the line at
power source side, insulating transformers and optical transmission
were necessary for transmitting signals to relay circuits of the
measuring apparatus, warning lamp 42, and warning buzzer.
Therefore, a problem that the whole system became complex was
existed.
The present invention is aimed at solving the above problems,
and the object of the present invention is to provide a vacuum
insulated switching apparatus provided with a reliable vacuum
pressure monitoring and measuring function by composing the
vacuum bulb with a grounded vacuum vessel and providing a vacuum
pressure measuring apparatus around the vacuum bulb.
The present invention is aimed at achieving the desired object
by providing a grounded vacuum vessel, a switch; which comprises a
fixed electrode attached to the vacuum vessel via an insulator, and a
movable electrode attached to the vacuum vessel via an insulator
facing to the fixed electrode; and a vacuum pressure measuring
apparatus attached to the vacuum vessel.
The present invention is aimed at achieving the desired object
by providing a grounded vacuum vessel,
a switch; which comprises a fixed electrode attached to the vacuum
vessel via an insulator, and a movable electrode attached to the
vacuum vessel via an insulator facing to the fixed electrode; a coaxial
electrode at a side plane of the vacuum vessel, and a magnetic field
generating apparatus arranged around the coaxial electrode.
The present invention is aimed at achieving the desired object
by providing a grounded vacuum vessel,
a switch; which comprises a fixed electrode attached to the vacuum
vessel via an insulator, and a movable electrode attached to the
vacuum vessel via an insulator facing to the fixed electrode; and a
coaxial electrode at a side plane of the vacuum vessel, and a magnetic
field generating apparatus is arranged around the coaxial electrode a:
a time to measure the vacuum pressure.
In accordance with the switching apparatus composed of as
above, the main circuit and the measuring element can be separated
electrically, and safety of the switching apparatus can be ensured by
increasing the reliability of the vacuum monitoring and measuring
function.
Brief description of the drawings
FIG. 1 is a schematic illustration of the vacuum bulb and the
vacuum pressure measuring terminal of an embodiment of the
present invention;
FIG.2 is a schematic illustration of the vacuum bulb and the
vacuum pressure measuring terminal of an embodiment of the
present invention;
FIG. 3 is a vertical cross section of the vacuum pressure
measuring terminal attached to the vacuum bulb of an embodiment of
the present invention;
FIG. 4 is a vertical cross section of another vacuum pressure
measuring terminal attached to the vacuum bulb of an embodiment of
the present invention;
FIG. 5 is a vertical cross section of the vacuum bulb of an
embodiment of the present invention;
FIG. 6 is a vertical cross section of the vacuum bulb of an
embodiment of the present invention;
FIG. 7 is a vertical cross section of the vacuum bulb of an
embodiment of the present invention;
FIG. 8 is a vertical cross section of another vacuum pressure
measuring terminal attached to the vacuum bulb of an embodiment of
the present invention;
FIG. 9 is a vertical cross section of another vacuum pressure
measuring terminal attached to the vacuum bulb of an embodiment of
the present invention;
FIG. 10 is a vertical cross section of another vacuum pressure
measuring terminal attached to the vacuum bulb of an embodiment of
the present invention;
FIG. 11 is a vertical cross section indicating another
embodiment of the present invention;
FIG. 12 is a vertical cross section indicating another
embodiment of the present invention;
FIG. 13 is a illustration of insulated switching apparatus of
an embodiment of the present invention;
FIG. 14 is a characteristic graph indicating a relationship
between the pressure P and breaking performance/dielectric strength
performance;
FIG. 15 is a schematic illustration indicating a method for
measuring the vacuum pressure of another embodiment of the
present invention;
Detailed explanation of the preferred embodiments of the invention
Embodiments of the present invention are explained in detail
referring to FIG. 1 to FIG. 15.
(Embodiment 1)
The first embodiment of the present invention is explained
hereinafter. A cross sectional view of a vacuum bulb 1 and a vacuum
pressure measuring terminal 30 is indicated in FIG. 1, and an
insulated switching apparatus composed by mounting rotatably the
movable conductor 21 to a main axis 20 is indicated in FIG. 12.
The vacuum bulb is composed by attaching two bushings 3, 4
to periphery of a grounded metallic vessel 2. A fixed electrode 5 and a
movable electrode 6 are arranged so as to be touchable/separable at
inside the vacuum bulb 1 to switch on or off by making the electrodes
touch or separate. The fixed electrode is fixed to the bushing 3, and a
flexible conductor 8 extended from the movable electrode 6 is
connected to the bushing 4. In accordance with the vacuum bulb 1 of
the present embodiment, an electric current flows through a path in
the order of bushing 3 - fixed electrode 5 - movable electrode 6 - flexible
conductor 8 - bushing 4. The movable electrode 6 is connected with
an insulating rod 9, and the insulating rod 9 is fixed to the metallic
vessel 2 via a bellow 10. The mark 11 indicates an arc shield for
preventing an earth fault generated by touching an arc A to the
metallic vessel 2.
An operation of the vacuum bulb 1 is explained hereinafter
referring to FIG. 13. FIG. 11 indicates a switching apparatus,
wherein the vacuum bulb 1 is operated by an operating mechanism 25.
The mark 30 indicates a disconnecting spring, which generates a
driving force by releasing a pressed insulating portion 31 by a trip
mechanism provided separately, and the driving force is transmitted
to the insulating rod 9 via a shaft 22. As the result, the insulating
rod is moved upwards or downwards, and the fixed electrode 5 and the
movable electrode 6 are touched or separated.
The mark 30 indicates a magnetron type measuring terminal,
which is attached at a side plane of the metallic vessel 2. The structure
of the measuring terminal 30 is indicated in FIG. 3. The measuring
terminal 30 is composed of a coaxial electrode 32 and a coil 36 for
generating a magnetic field arranged around periphery of the coaxial
electrode 32. The coaxial electrode 32 is composed of a cylindrical
outer electrode 33 and an inner electrode 34 penetrating the outer
electrode. The outer electrode 33 and the inner electrode 34 are
insulated each other by the insulating portion 31. A ring shaped
permanent magnet 37 can be used instead of the coil 36 as indicated in
FIG. 4. Additionally, the magnetic polarity of the permanent magnet
N pole and S pole are reversible.
Operation of the measuring terminal 30 is explained
hereinafter referring to FIG. 3. A negative direct current is applied
to the inner electrode 34 by an electric power source circuit 40. An
alternating current, or voltage pulses also can be used. The electrons
e released from the inner electrode 34 receive Lorentz force by a
magnetic field B applied by an electric field E and the coil 36, and
move rotatively around the periphery of the inner electrode 34. The
rotating electrons e collide with residual gases to ionize them, and
generated anions I flow into the inner electrode 34. The ionized
current j varies depending on the amount of the residual gases, that is
a pressure. Therefore, the pressure can be measured by determining
the voltage V generated between the both ends of the resistance R.
When the pressure must be monitored continuously, a relay may be
operated to turn on a warning lamp, or to generate a warning sound
based on the voltage at the both ends of the resistance R. As the
graph shown in FIG. 14 indicates, the disconnecting performance and
the insulating performance of the vacuum bulb 1 is rapidly
deteriorated when the pressure is increased equal to or more than 10-5
Torr. The vacuum pressure measuring terminal 30 indicated in the
present embodiment is detectable till approximately 10-6 Torr, and
sufficiently effective for monitoring the vacuum pressure.
Advantages of the present embodiment are explained
hereinafter. Because the measuring terminal 30 is provided to the
grounded metallic vessel 2, the power source circuit for the measuring
terminal 30 can be separated from the main circuit 13. Therefore,
malfunction caused by a surge from the main circuit 13 can be avoided,
and reliability of the switching apparatus is improved. Because
signals are transmitted directly from the resistance R to measuring
instruments or relay circuits, the measuring system can be small in
size and simplified. In accordance with the present invention, the
measuring terminal 30 is fixed directly to the metallic vessel 2.
Therefore, in comparison with the prior art, wherein the measuring
terminal was fixed via an insulating cylinder, the number of electrons
entering into the vacuum bulb 1 is small, and an advantage to avoid
deterioration of the disconnecting performance and the insulating
performance of the vacuum bulb 1 can be realized.
FIG.5 shows an example of a magnetron using metallized part of the
ceramics to radiate electrons. The coaxial electrode 32 and outer electrode
33 are connected to negative polarity and the inner electrode 34 is
connected to positive polarity. Therefore, the polarity is reverse to FIG.4.
The electric field becomes high near the thin metallized part 43 of the
ceramics 31 for connecting the outer electrode 33 with ceramics 31 is high,
and, therefore, the electron emission coefficient becomes high. As a result,
the sensitivity of the magnetron is improved.
The position for fixing the measuring terminal 30 is preferably
at an outside of the arc shield 11 as indicated in FIG. 6. Because
metallic particles, electrons, and ions released from the electrode at a
disconnecting time do not enter into the measuring terminal 30, and
the reliability can be maintained. The shield 12 can be provided
separately in the vacuum bulb 1 as indicated in FIG. 7. In this case,
the coil 36 can be arranged far from the electrode, and decrease of the
disconnecting performance by the magnetic field can be avoided. The
coil 36 is not necessarily provided at all times, but it may be provided
at only pressure measuring time, in order to avoid the influence of the
magnetic field to the disconnecting performance.
It is natural that the present invention is applicable not only to
the magnetron terminal, but also to measuring terminals such as
ionization vacuum gauge terminal, discharging gap measuring
terminal, and the like. The reliability of all the measuring terminal
can be improved by attaching to the grounded metallic vessel 2,
because the measuring system and the main circuit can be separated.
(Embodiment 2)
The second embodiment of the present invention is explained referring to
FIG.2. In accordance with the present embodiment, the measuring
terminal 30 indicated in FIG. 1, is attached to the metallic vessel 2 of the
vacuum bulb 1 through an insulating member 50. In case the thickness of
the insulating member 50, electrons from the sensor repeat to collide with
the insulating member 50 and multiplied electrons by secondary
electron multiplication enter into the vacuum vessel 1. As a result, the
insulation performance reduces. Therefore, the appropriate thickness of
the insulating member 50 is 2 to 3mm.
According to j the present embodiment, the main circuit and
measuring system are separated, and therefore, it is capable of avoiding
the failure of measuring system caused by the surge current from the main
body. The vacuum measuring apparatus is able to be installed at the wall of
the grounded vacuum vessel (metallic vessel) 2 as well as any place distant.
from the vacuum vessel 2 as shown in FIG. 15. That is, it is possible to
install the vacuum measuring apparatusat anywhere in the vucuum vessel
if the pressure is able; to be measured.
(Embodiment 3)
The third embodiment of the present invention is explained
hereinafter referring to FIG. 8. In accordance with the present
embodiment, the measuring terminal 30 indicated in FIG. 7 is
attached to the metallic vessel 2 in the vacuum bulb 1 indicated in FIG.
1. The measuring terminal 30 is composed of an outer electrode 33,
an inner electrode 34, and a third electrode 39 having an equal
potential to the outer electrode 33 provided facing to the inner
electrode 34. Accordingly, the electrons e released from a top end of
the inner electrode 34 are captured by the electrode 39, entering the
electrons e into inside of the vacuum bulb can be decreased, and
decrease of the insulating performance of the vacuum bulb 1 can be
avoided. The same effect as above can be obtained by providing a
hole 15 to the metallic vessel 2, and attaching the coaxial electrode 32
thereon as indicated in FIG. 9.
As shown in FIG. 10, a hole 51 smaller than the inside of outer
electrode 33 is provided at the metallic vessel 2. The electrons e2 emitted
from the top end of the inner electrode 34 receive Lorentz force by the
electric field E and magnetic field B, and move along a spiral locus 44 and
reach to the metallic vessel 2. When the electron e2 repeat to collide with
residual gases, ion current j flows. In addition to the current by the electron
e1, the sensitivity is improved by the effect of electrons e2.
(Embodiment 4)
The fourth embodiment of the present invention is explained
hereinafter referring to FIG. 9. In accordance with the present
embodiment, the measuring terminal 30 indicated in FIG. 11 is
attached to the metallic vessel 2 in the vacuum bulb 1 indicated in FIG.
1. The measuring terminal 30 comprises an outer electrode composed
of a metallic plated film 52 on an inner side plane of a cup shaped
ceramic body 51. In accordance with the embodiments 1 and 2 as
shown in FIG.3, the insulating portion 31 and the outer electrode 33
were manufactured separately. However, in accordance with the
present embodiment, the insulating portion and the outer electrode
can be manufactured as an integrated member. Therefore, the
numbers of parts and brazing portions can be decreased.
(Embodiment 5)
The fifth embodiment of the present invention is explained
hereinafter. In accordance with the present embodiment indicated in
FIG. 11, the measuring terminal 30 indicated in FIG. 11 is attached
to the metallic vessel 2 in the vacuum bulb 1 indicated in FIG. 1.
The measuring terminal 30 comprises the inner electrode 34 having a
screw portion, which improves a sensitivity of the measurement by
enhancing a local electric field at surface of the inner electrode 34 to
increase the amount of electrons released from the inner electrode 34.
Naturally, the same effect as above can be obtained by providing any
protrusion at the inner electrode 34.
(Embodiment 6)
The sixth embodiment of the present invention is explained
hereinafter referring to FIG. 15. The measuring terminal 30 is
attached at the side plane of the metallic vessel 2 as same as the
embodiment 1 indicated in FIG. 1. In accordance with the present
embodiment, generation of a direct current voltage applied to the
measuring terminal 30 and measurement of the ionic current are
performed using a megohmmeter 41, i.e. an insulation resistance
tester. The megohmmeter 41 is a handy type tester for measuring M
O level resistance by applying a direct current voltage of several kV to
an insulator and measuring a leak current, and one of instruments,
which are generally owned by personal in charge of maintenance and
control of high voltage apparatus. Voltage terminals 42 of the
megohmmeter 41 are connected with the coaxial electrode 32 of the
measuring terminal 30, and a resistance R is measured by applying a
voltage V. The leaking current (I = V/R) determined by the voltage V
and the resistance R corresponds to the ionic current I depending on
the pressure P. Accordingly, if a relationship between the resistance
R and the pressure P is determined previously, the pressure can be
readily measured with the megohmmeter.
It is not necessary to prepare a special electric power source for
measuring pressure, and the pressure can be readily measured with a
low cost.
(Embodiment 7)
The seventh embodiment of the present invention is explained
hereinafter. The present embodiment is a countermeasure for
prevent the magnetic field B generated at the measuring terminal 30
from entering into the vacuum bulb 1. The composition is as same
as the embodiment 1 indicated in FIG. 1. In accordance with the
present embodiment, the metallic vessel 2 indicated in FIG. 1 is made
of a magnetic material such Monel (a Cu-Ni alloy) and the like, in
order to avoid decrease of disconnecting performance with entering a
magnetic field by shielding the magnetic field generated at the
measuring terminal with the metallic vessel 2.
The present invention can be applied to a rotary operation type
vacuum bulb indicated in FIG. 12. The movable electrode 6 is
rotated with a main axis 20 as a supporting point to be contacted or
separated with the fixed electrode 5. The fixed electrode 5 is
insulated by an insulating cylinder 16A, and the movable electrode 6
is insulated by an insulating cylinder 16B, from the grounded
metallic vessel 2, respectively. In accordance with the present
embodiment, the hole 15 is added in order to compose a small size
switching apparatus comprising a breaker, a disconnector, and
ground switch, by making the movable electrode 6 stop at each of four
positions, i.e. a closing position Y1, an opening position Y2, a
disconnected position Y3, of which insulating is not broken with
thunder and the like, and grounding position Y4. In accordance with
adding the vacuum pressure measuring terminal 30 of the present
invention to the vacuum bulb 1 having a function as a disconnector,
safety of operators for maintenance and inspection can be ensured,
and the reliability of the switching apparatus can be improved.
As explained above, in accordance with the present invention,
reliability in monitoring and measuring the vacuum pressure is
improved by providing the vacuum pressure measuring terminal to
the grounded metallic vessel, and as the result, a vacuum insulated
switching apparatus having a high safety can be provided.
WE CLAIM

1. A vacuum insulated switching apparatus comprising:
a grounded vacuum vessel,
a switch, which comprises
a fixed electrode attached to said vacuum vessel via an
insulator, and
a movable electrode attached to said vacuum vessel via
an insulator facing to said fixed electrode, ana
a vacuum pressure measuring apparatus for measuring the
pressure in said vacuum vessel.
2. A vacuum insulated switching apparatus as claimed in
claim 1, wherein
said vacuum pressure measuring apparatus being capable of
detecting a pressure in the range of 10-4- 10-6 Torr.
3. A vacuum insulated switching apparatus comprising:
a grounded vacuum vessel,
a switch, which comprises
a fixed electrode attached to said vacuum vessel via an
insulator, and
a movable electrode attached to said vacuum vessel via
an insulator facing to said fixed electrode, and
a vacuum pressure measuring terminal, which comprises
a coaxial electrode and
a magnetic field generating apparatus arranged around
said coaxial electrode.
4. A vacuum insulated switching apparatus comprising:
a grounded vacuum vessel,
a switch, which comprises
a fixed electrode attached to said vacuum vessel via an
insulator, and
a movable electrode attached to said vacuum vessel via
an insulator facing to said fixed electrode, and
a vacuum pressure measuring terminal, which determines
vacuum by
a coaxial electrode attached to said vacuum vessel and
a magnetic field generating apparatus arranged around said
coaxial electrode.
5. A vacuum insulated switching apparatus as claimed in any
of claims 3 and 4, wherein
an arc shield is provided around the electrode arranged in said
vacuum vessel, and
said coaxial electrode is provided at outside of said arc shield
in the vacuum vessel.
6. A vacuum insulated switching apparatus as claimed in any
of claims 3 and 4, wherein
a shielding means for preventing metallic particles released
from a contact electrode at switching time entering into said coaxial
electrode is provided in said vacuum vessel.
7. A vacuum insulated switching apparatus as claimed in any
one of claims 3 to 6, wherein
an electrode having the same potential as an outer electrode of
said coaxial electrode is provided facing to a central electrode of said
coaxial electrode.
8. A vacuum insulated switching apparatus as claimed in any
one of claims 3 to 6, wherein
said coaxial electrode is composed of a cup shaped ceramic
cylinder, of which inside is plated with metal, and the central
electrode penetrating through the ceramic cylinder.
9. A vacuum insulated switching apparatus as claimed in any
one of claims 3 to 8, wherein
a protrusion for enhancing electric field is provided to the
central electrode of said coaxial electrode.
10. A vacuum insulated switching apparatus as claimed in any
one of claims 3 to 8, wherein
a megohmmeter is used as an electric power source of said
vacuum pressure measuring apparatus.
11. A vacuum insulated switching apparatus as claimed in any
one of claims 3 to 10, wherein
said vacuum vessel is composed of a magnetic material.

In accordance with a vacuum bulb 1 composed of a grounded
metallic vessel 2, the reliability in monitoring and measuring the
vacuum pressure can be improved by providing a vacuum pressure
measuring terminal 30 at a side plane of the metallic vessel 2 to
separate electrically the main circuit 13 and the measuring terminal
30 each other.