U.S. patent application number 11/410141 was filed with the patent office on 2006-08-24 for gas-insulated switchgear tank.
This patent application is currently assigned to Hitachi Ltd.. Invention is credited to Fumihiro Endo, Shunji Ito, Takashi Omori, Toshiaki Rokunohe, Tomoaki Utsumi, Yoshitaka Yagihashi.
Application Number | 20060186091 11/410141 |
Document ID | / |
Family ID | 34270049 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060186091 |
Kind Code |
A1 |
Rokunohe; Toshiaki ; et
al. |
August 24, 2006 |
Gas-insulated switchgear tank
Abstract
In a gas-insulated switchgear tank in which an electric
insulating characteristic is improved by a gas, and which has a
vacuum circuit-breaker, a disconnecting switch, and a container in
which container the vacuum circuit-breaker and the disconnecting
switch are arranged and an inside of which container is adapted to
be hermetically sealed and filled with the gas in such a manner
that the vacuum circuit-breaker and the disconnecting switch are at
least partially surrounded by the gas, the gas includes N.sub.2 and
O.sub.2.
Inventors: |
Rokunohe; Toshiaki;
(Hitachinaka, JP) ; Yagihashi; Yoshitaka;
(Hitachi, JP) ; Endo; Fumihiro; (Hitachi, JP)
; Utsumi; Tomoaki; (Hitachi, JP) ; Ito;
Shunji; (Hitachi, JP) ; Omori; Takashi;
(Hitachi, JP) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Hitachi Ltd.
Tokyo
JP
Japan AE Power Systems Corporation
Tokyo
JP
|
Family ID: |
34270049 |
Appl. No.: |
11/410141 |
Filed: |
April 25, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10921861 |
Aug 20, 2004 |
|
|
|
11410141 |
Apr 25, 2006 |
|
|
|
Current U.S.
Class: |
218/43 |
Current CPC
Class: |
H01H 33/22 20130101;
H01H 33/6661 20130101; H02B 13/0354 20130101; H01H 2033/566
20130101; H02B 13/055 20130101 |
Class at
Publication: |
218/043 |
International
Class: |
H01H 33/82 20060101
H01H033/82 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2003 |
JP |
2003-324047 |
Claims
1. A gas-insulated switchgear tank to be electrically connected to
at least one of a number of bus bars, comprising: a vacuum
circuit-breaker including a movable contact, a plurality of
disconnecting switches each of which includes a movable contact,
and a container in which the vacuum circuit-breaker and the
disconnecting switch are arranged and a mixture of nitrogen and a
gas of earth-warming coefficient not more than 1 is contained, and
a gaseous pressure of the mixture is kept at 0.2-0.8 MPa.cndot.abs,
wherein the movable contact of the vacuum circuit-breaker is
movable along a linear axis, and the disconnecting switches are
juxtaposed with each other in a direction parallel to the linear
axis.
2. A gas-insulated switchgear tank to be electrically connected to
at least one of a number of bus bars, comprising: a vacuum
circuit-breaker including a movable contact, at least one
disconnecting switch including a movable contact, and a container
in which the vacuum circuit-breaker and the disconnecting switch
are arranged and a mixture of nitrogen and a gas of earth warming
coefficient not more than 1 is contained, and a gaseous pressure of
the mixture is kept at 0.2-0.8 MPa.cndot.abs, wherein the movable
contact of the vacuum circuit-breaker and the movable contact of
the disconnecting switch are movable along respective linear
axes.
3. A gas-insulated switchgear tank according to claim 1, wherein
the movable contact of the vacuum circuit-breaker and the movable
contacts of the disconnecting switches are movable along respective
linear axes, and the linear axes are vertical.
4. A gas-insulated switchgear tank according to claim 2, wherein
the linear axes are vertical.
5. A gas-insulated switchgear tank according to claim 2, wherein
the linear axes are distant from each other in a horizontal
direction.
6. A gas-insulated switchgear tank according to claim 5, wherein
the linear axis along which the movable contact of the
disconnecting switch is movable is arranged in the horizontal
direction between the at least one of the bus bars and the linear
axis along which the movable contact of the vacuum circuit-breaker
is movable.
7. A gas-insulated switchgear tank according to claim 3, wherein
the linear axis of at least one of the disconnecting switches and
the linear axis of the vacuum circuit-breaker are spaced from each
other in a horizontal direction.
8. A gas-insulated switchgear tank according to claim 7, wherein
the linear axis along which the movable contact of the at least one
of the disconnecting switches is movable is arranged in the
horizontal direction between the at least one of the bus bars and
the linear axis along which the movable contact of the vacuum
circuit-breaker is movable.
9. A gas-insulated switchgear tank according to claim 1, wherein
the container includes a first compartment in which at least a part
of the vacuum circuit-breaker is contained and second compartments
in each of which at least a part of corresponding one of the
disconnecting switches is contained, a gaseous pressure in the
first compartment is lower than a gaseous pressure in the second
compartments, and the first compartment and at least one of the
second compartments are juxtaposed with each other in a horizontal
direction.
10. A gas-insulated switchgear tank according to claim 2, wherein
the container includes a first compartment in which at least a part
of the vacuum circuit-breaker is contained and at least one second
compartment in which at least a part of the disconnecting switch is
contained, a gaseous pressure in the first compartment is lower
than a gaseous pressure in the at least one second compartment, and
the first and the at least one second compartment are juxtaposed
with each other in a horizontal direction.
11. A gas-insulated switchgear tank according to claim 9, wherein
the horizontal direction is perpendicular to a longitudinal
direction of the at least one of the bus bars.
12. A gas-insulated switchgear tank according to claim 9, wherein
as viewed in a direction parallel to a longitudinal direction of
the at least one of the bus bars, the horizontal direction
traverses a direction along which longitudinal axes of the bus bars
are arranged.
13. A gas-insulated switchgear tank according to claim 9, wherein
the at least one second compartment is arranged in the horizontal
direction between the at least one of the bus bars and the first
compartment.
14. A gas-insulated switchgear tank according to claim 12, wherein
the direction along which longitudinal axes of the bus bars are
arranged is vertical.
15. A gas-insulated switchgear tank according to claim 9, wherein
the movable contact of the vacuum circuit-breaker is movable along
a linear axis, and the second compartments are juxtaposed with each
other in a direction parallel to the linear axis.
16. A gas-insulated switchgear tank according to claim 10, wherein
the horizontal direction is perpendicular to a longitudinal
direction of the at least one of the bus bars.
17. A gas-insulated switchgear tank according to claim 10, wherein
as viewed in a direction parallel to a longitudinal direction of
the at least one of the bus bars, the horizontal direction
traverses a direction along which longitudinal axes of the bus bar
are arranged.
18. A gas-insulated switchgear tank according to claim 10, wherein
the second compartment is arranged in the horizontal direction
between the at least one of the bus bars and the first
compartment.
19. A gas-insulated switchgear tank according to claim 16, wherein
the direction along which longitudinal axes of the bus bars are
arranged is vertical.
20. A gas-insulated switchgear tank according to claim 10, wherein
the gas-insulated switchgear tank comprises a plurality of the
disconnecting switches and a plurality of the second compartments
for containing at least the parts of the disconnecting switches
respectively, the movable contact of the vacuum circuit-breaker is
movable along a linear axis, and the second compartments are
juxtaposed with each other in a direction parallel to the linear
axis.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claim is a continuation application of U.S.
patent application Ser. No. 10/921,861 filed Aug. 20, 2004, which
claims priority to Japanese Patent Application No. 2003-324047,
filed Sep. 17, 2003, the entire disclosure of these documents is
herein expressly incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a gas-insulated switchgear
tank.
[0003] JP-A-2002-199522 discloses a switchgear in which a vacuum
circuit-breaker and silicone oil are used. Fujijihou Vol. 75 No. 11
2002 discloses a switchgear product in which a vacuum
circuit-breaker and dry-air are used.
BRIEF SUMMARY OF THE INVENTION
[0004] An object of the present invention is to provide a
gas-insulated switchgear tank suitable for
environment-consciousness while maintaining an electrical
insulating characteristic.
[0005] According to the invention, in a gas-insulated switchgear
tank in which an electric insulating characteristic is improved by
a gas, and which has a vacuum circuit-breaker, a disconnecting
switch, and a container in which container the vacuum
circuit-breaker and the disconnecting switch are arranged and an
inside of which container is adapted to be hermetically sealed and
filled with the gas in such a manner that the vacuum
circuit-breaker and the disconnecting switch are at least partially
surrounded by the gas, since the gas includes N.sub.2 and O.sub.2,
the electric insulating characteristic by the N.sub.2 is further
improved by O.sub.2.
[0006] It is preferable for maintaining a hermetic sealing of the
vacuum circuit-breaker securely, particularly, improving an
operable life time of a bellows of the vacuum circuit-breaker
against a fatigue caused by repeated expansion and contraction of
the bellows that the container includes a first compartment in
which at least a part of the vacuum circuit-breaker is exposed to
the gas, and a second compartment in which at least a part of the
disconnecting switch is exposed to the gas, and a gaseous pressure
in the first compartment is lower than a gaseous pressure in the
second compartment.
[0007] It is preferable for keeping the electric insulating
characteristic of the gas that the gas and include a vapor whose
dew point is not less than a minimum value of an environment
temperature in which environment temperature the gas-insulated
switchgear tank is permitted to be used, and/or that the gas does
not include a vapor whose dew point is not less than a minimum
value of a temperature in the container in which temperature at
least one (or both) of the vacuum circuit-breaker and the
disconnecting switch is permitted to be operated.
[0008] It is preferable for easily or securely finding a leakage of
the gas that the gas further includes a smelly gas component.
[0009] It is preferable for effectively improving the electric
insulating characteristic of the N.sub.2 by O.sub.2 that a partial
pressure of O.sub.2 is 5-60% of a total pressure of the gas.
[0010] It is preferable for maintaining the hermetic sealing of the
vacuum circuit-breaker securely, particularly, improving the
operable life time of the bellows of the vacuum circuit-breaker
against the fatigue caused by repeated expansion and contraction of
the bellows that a direction in which a movable contact of at least
one of the vacuum circuit-breaker and the disconnecting switch is
movable is vertical.
[0011] It is preferable for effectively improving the electric
insulating characteristic of the gas that a pressure of the gas in
the container is 0.2-0.8 MPa.cndot.abs. It is preferable for
effectively utilizing the electric insulating characteristic of
N.sub.2 that the gas includes N.sub.2 and O.sub.2 as main
components thereof. It is preferable for miniaturization of the
gas-insulated switchgear tank that a maximum length of (the longest
length measurable in) a part of the gas-insulated switchgear tank,
which part does not include a driving mechanical force generator
for generating a driving mechanical force absorbed in the
gas-insulated switchgear tank, extends in a direction along which a
maximum length of (the longest length measurable in) the vacuum
circuit-breaker extends, and/or that the maximum length of the part
of the gas-insulated switchgear tank, which part is prevented from
including the driving mechanical force generator for generating the
driving mechanical force absorbed in the gas-insulated switchgear
tank, extends along a direction in which a movable contact of at
least one (or both) of the vacuum circuit-breaker and the
disconnecting switch is movable. It is preferable for maintaining
the hermetic sealing of the vacuum circuit-breaker securely,
particularly, improving the operable life time of the bellows of
the vacuum circuit-breaker against the fatigue caused by repeated
expansion and contraction of the bellows that the direction is
vertical. It is preferable that the container has one of
cylindrical shape and box shape.
[0012] When the vacuum circuit-breaker has a bellows shape
deformable to expand and contract so that a vacuumed chamber is
formed in the bellows shape and a movable contact movable in the
vacuumed chamber, it is preferable for improving the operable life
time of the bellows against the fatigue caused by repeated
expansion and contraction of the bellows that an outer periphery of
the bellows shape is exposed to the gas in the first compartment,
and/or that both ends of the bellows shape terminating respectively
in an expansion and contraction direction of the bellows shape
overlap each other at least partially as seen vertically. It is
preferable for effectively improving the electric insulating
characteristic of the N.sub.2 by O.sub.2 while keeping the operable
life time of the bellows against the fatigue caused by repeated
expansion and contraction of the bellows that a ratio of a partial
pressure of O.sub.2 in the gas to a total pressure of the gas is
greater than a ratio of a partial pressure of O.sub.2 in the
atmosphere to a total pressure of the atmosphere.
[0013] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0014] FIG. 1 is a diagram showing a relationship between a gas
pressure and a break down voltage in each of an adaequalis electric
field in dry air, a concentrated electric field in dry air and an
adaequalis electric field in N.sub.2 gas.
[0015] FIG. 2 is a diagram showing a relationship between a break
down voltage and a mixing (content) ratio of O.sub.2.
[0016] FIG. 3 is a diagram showing a relationship between a gas
pressure and a break down voltage in each of mixing ratios between
N.sub.2 and O.sub.2.
[0017] FIG. 4 is a diagram showing a relationship between a dry air
gaseous pressure and an apparatus weight.
[0018] FIG. 5 is a diagram showing a relationship between a break
down voltage and an electrode condition.
[0019] FIG. 6 is a schematic view showing a tank type gas insulated
switchgear as an embodiment of the invention.
[0020] FIG. 7 is a schematic view showing another tank type gas
insulated switchgear as another embodiment of the invention.
[0021] FIG. 8 is a schematic view showing a box type C gas
insulated switchgear as another embodiment of the invention.
[0022] FIG. 9 is a schematic view showing a three-phase gas
insulated switchgear as another embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] At first, a principle as a basis of the invention is
explained. N.sub.2 is known as a gas of extremely low influence on
environment load. Further, N.sub.2 is not electrically negative gas
and is known as a good insulating gas of typical electron retarding
gas. The electron retarding gas decelerates high-speed electrons to
decrease electron energy. But, dielectric strength of N.sub.2 is
about one third in comparison with SF.sub.6 as a generally used
electrically negative gas, and thereby an improvement of dielectric
strength thereof is necessary.
[0024] Further, when the dielectric strength of N.sub.2 is 1, it is
generally known that of N.sub.2O is 1.1, that of CH.sub.4 is 1.0,
that of CO.sub.2 is 0.9, and that of O.sub.2 is 1.0, irrespective
of change thereof in accordance with various conditions. Among
these, N.sub.2 satisfies all of less influence on environment load,
high dielectric strength, and easiness on handling.
[0025] A mechanism on destroying the insulation of N.sub.2 is as
follows. When an acceleration more than electron retarding effect
is applied to the electrons by an electric field, electron
avalanche occurs to increase a number of the electrons so that the
insulation is destroyed. Generally, it is known that the dielectric
strength is improved to increase a break down voltage by mixing the
negative gas with the electron retarding gas, but the negative gas
increasing significantly the dielectric strength is designated as a
global warming gas, or GWP thereof is more than 1, so that the
influence on the global environment is concerned.
[0026] On the other hand, as the negative gas whose global warming
coefficient is not more than 1 and which does not include atom of
Chlorine, Fluorine, Sulfur or the like, CO.sub.2 and O.sub.2 exist.
Particularly, O.sub.2 is not the global warming gas, and can
improve the dielectric strength when being mixed with N.sub.2.
[0027] In FIG. 1, a gaseous pressure characteristic of break down
voltage of each of pure N.sub.2 and N.sub.2/O.sub.2 mixture gas
(dry air) is shown. As described in "SF.sub.6 no
chikyuh-kankyou-huka to SF.sub.6 kongou.cndot.daitai-gas zetuenn"
of no. 841 Denki-gakkai-gijutsu-houkoku, a gaseous pressure
characteristic of break down voltage in dry gas under adaequalis
electric field is indicated by a dot line, and a gaseous pressure
characteristic of break down voltage in N.sub.2 under adaequalis
electric field is indicated by a dashed line. The dielectric
strength of N.sub.2 saturates in a high gaseous pressure region not
less than 0.8-1 Mpa.cndot.abs. A reason of this is that since
N.sub.2 has a gradual ionization characteristic change in the
vicinity of critical electric field under the gaseous pressure less
than about 0.5 Mpa.cndot.abs, a local electric field dependence is
small so that the gaseous pressure effect determines the dielectric
strength. On the contrary, since the electron avalanche is
magnified by ionization in short length and the electric field
destroying the insulation is high, the dielectric strength is
strongly affected by weak point breakdown.
[0028] On the other hand, the gaseous pressure at which the
dielectric strength of the air saturates is higher than the gaseous
pressure at which the dielectric strength of N.sub.2 saturates, and
about 3 Mpa.cndot.abs. A reason of this is that by mixing with
O.sub.2, the local electric field dependence is lowered. But, the
gaseous pressure characteristic of break down voltage in the air
obtainable when the electric field is not constant or a high
voltage electrode on which the electric field is concentrated
locally is used, is not known.
[0029] The solid line in the drawing shows the gaseous pressure
characteristic of break down voltage obtainable when the electric
field is concentrated. When the electric field is concentrated,
since the electric field locally becomes significantly high under
the gaseous pressure of about 0.5 Mpa.cndot.abs, the dielectric
field is strongly affected by the weak point breakdown and a
dielectric strength saturation tendency is found from about 0.5
MPa.cndot.abs. In the switchgear, it is difficult that the whole of
high-voltage regions is designed as the adaequalis electric field,
and is should be designed to have the gaseous pressure
characteristic on which the electric field concentration is taken
into consideration.
[0030] In a case of the dry air, while the break down voltage is
increased by the effect of O.sub.2 as the negative gas in
comparison with N.sub.2, the gaseous pressure characteristic
depends on the characteristic of N.sub.2 included by the whole gas
by 80%, and has a tendency of saturating at 0.8-1 Mpa.cndot.abs.
Therefore, when miniaturizing with increasing the gaseous pressure,
the maximum gaseous pressure becomes about 1 Mpa.cndot.abs.
[0031] In FIG. 2, a relationship between a mixing rate and the
break down voltage is shown. An ordinate corresponds to a relative
ratio with respect to the break down voltage of N.sub.2 gas. The
mixing rate is an average of the break down voltage under a
constant gaseous pressure. Generally speaking, an increase of the
break down voltage caused by mixing O.sub.2 with N.sub.2 occurs
within a range of the partial pressure 5-60% corresponding to the
mixing rate of O.sub.2. An optimum mixing rate of O.sub.2 depends
on the gaseous pressure. As shown in FIG. 3, the optimum mixing
rate is the partial pressure rate of O.sub.2 of 5-60% when the
gaseous pressure is 0.2-0.4 Mpa.cndot.abs, and the optimum mixing
rate is the partial pressure rate of O.sub.2 of about 20% when the
gaseous pressure is not less than 0.4 Mpa.cndot.abs. Therefore, the
dry air can be deemed to be the mixture gas of N.sub.2 and O.sub.2
as the electron retarding gas, and the optimum gaseous pressure is
not less than 0.4 Mpa.cndot.abs when the dry air is used.
[0032] On the other hand, a length of a bellows becomes great to
deteriorate the miniaturization and weight saving when the gaseous
pressure in a container receiving therein a vacuum switchgear
becomes high. An operating life against repeated opening and
closing operations of the bellows is evaluated from a stress
applied to each of corners of the bellows, and the stress is
calculated as a total amount of a stress caused by the pressure and
a stress caused by a displacement. That is, the stress caused by
the pressure increases in accordance with an increase of the
gaseous pressure, but the stress applied to each of the corners can
be decreased to not more than an acceptable level by increasing a
number of the corners of the bellows.
[0033] Therefore, the length of the bellows is mainly determined on
the basis of the stress caused by the displacement when the gaseous
pressure is low, so that an increasing rate of the length of the
bellows with respect to an increase of the gaseous pressure is
small, and the length of the bellows is mainly determined on the
basis of the stress caused by the pressure when the gaseous
pressure is high, so that the length increases substantially in
proportion to the gaseous pressure. Generally, when the gaseous
pressure is not more than 0.2 Mpa.cndot.abs, the stress caused by
the displacement is dominant, and when the gaseous pressure is not
less than 0.5 Mpa.cndot.abs, the stress caused by the pressure is
dominant.
[0034] Therefore, for miniaturization of the apparatus, a design
flexibility needs to be maintained in a longitudinal direction of
the bellows of the vacuum switch gear and so forth, and the
miniaturization is obtainable by making a longitudinal direction of
a container containing therein the vacuum switch gear and a
longitudinal direction of the vacuum switchgear parallel to each
other. Incidentally, since it is effective for minimizing an
increase in volume of the switchgear that the length is increased
in the longitudinal direction rather than a short length direction,
it is effective for the miniaturization that the increase in length
of the bellows in accordance with the increase of the gaseous
pressure is absorbed in the longitudinal direction of the
switchgear by making the longitudinal directions of the vacuum
switchgear and the container parallel to each other.
[0035] Further, in the disconnecting switch, a small current
interrupting performance is needed. Since the interrupting
performance of the N.sub.2/O.sub.2 mixture gas includes problems of
thermal destruction as well as continued current, a distance
between poles cannot be necessarily decreased in accordance with
the increase of the gaseous pressure. Therefore, the length in a
direction between the poles increases in accordance with the
increase of the gaseous pressure, so that a movable contact moving
direction and a longitudinal direction of the container as well as
the vacuum switchgear needs to be made parallel to each other to
decrease the size and weight of the apparatus.
[0036] A wall thickness t1 of the container of cylindrical shape
containing the high pressure gas with hermetic sealing increases in
accordance with the gaseous pressure as shown in formula (1).
t1=P.times.D/(2.sigma.) (1)
[0037] In this case, .sigma.: allowable stress in circumferential
direction, P: gaseous pressure, D: inner diameter, t1: wall
thickness of cylinder. On the other hand, a plate thickness t2 of a
flange not cylindrical increases in proportion to a square root of
the gaseous pressure as shown in formula (2).
t2=2d.times.(Z.times.C.times.P/.sigma.).sup.0.5 (2)
[0038] In this case, d: fixing bolt pitch circle, Z: constant value
determined in accordance with a shape of plate, C: constant value
determined in accordance with mounting feature of a flat plate, P:
gaseous pressure, and a allowable stress. From the formulas (1) and
(2), it is apparent that the weight of the apparatus increases in
accordance with an increase of the plate thickness caused by the
increase of the gaseous pressure. That is, the weight of the
apparatus increases in accordance with the increase of the pressure
of the used gas when the inner diameter is kept constant. Further,
the miniaturization of the apparatus is restrained by an increase
of driving force of the actuator caused by the increase of the
gaseous pressure. On the other hand, from the relationship between
the gaseous pressure and the break down voltage shown in FIG. 1,
the increase of the gaseous pressure causes the increase of the
dielectric strength to enable the size of the apparatus to be
decreased, so that the size and weight of the apparatus is
decreased. Therefore, an optimum gaseous pressure for decreasing
both of the size and weight exists.
[0039] The optimum gaseous pressure changes in accordance with a
ratio in weight between the cylindrical portion and the flange,
but, it is generally used for the miniaturization and cost down
that a number of the flanges is made minimum, that is, a constant
value. Further, a length of the cylindrical portion can be
decreased by the increase of the dielectric strength with an affect
onto the mechanical portion or the like, so that its rate is small
and estimated at about one-third in comparison with the change of
the inner diameter.
[0040] FIG. 4 shows an example in which a ratio in weight between
the cylindrical portion and the flange is 4:1. The gaseous pressure
for minimizing the weight of the apparatus is about 0.4
MPa.cndot.abs, and a design should be done to satisfy the gaseous
pressure of 0.2-0.8 MPa.cndot.abs to obtain a design within a range
of 20% from the minimum value. Further, when the gaseous pressure
of the N.sub.2/O.sub.2 mixture gas is not more than 0.2
MPa.cndot.abs, the weight increases abruptly. An optimum range of
the gaseous pressure of the dry gas for decreasing the size and
weight of the switchgear is between 0.2-0.8 MPa.cndot.abs.
[0041] That is, in the gas-insulated switchgear tank including the
insulating gas of the mixture gas (a partial pressure ratio of
O.sub.2 is 5%-60%) or dry air with the main components of N.sub.2
and O.sub.2, it is necessary for decreasing the size and weight
that the minimum gaseous pressure or rated pressure is 0.2-0.8
MPa.cndot.abs.
[0042] FIG. 5 shows the break down voltage changing in accordance
with a treatment condition of the electrode in the N.sub.2/O.sub.2
mixture gas. Lowest and highest break down voltages of a bare
electrode are indicated by bars, and an average break down voltage
is indicated by .largecircle.. By coating the electrode, an initial
break down voltage is made not less than the average of the bare
condition. Further, the insulating matter is molded on the
electrode, the break down voltage is further increased, so that
under the constant gaseous pressure, the initial break down voltage
is made 1.5 times of the average of the bare condition, and the
significant miniaturization is obtainable if using the mixture gas.
Further, the gaseous pressure characteristic for the electrode with
the insulating coat is in proportion to the gaseous pressure
characteristic for the bare electrode, so that decreasing the
weight and size is obtainable by incorporating the insulating coat
or insulating molding under the constant optimum gaseous
pressure.
[0043] As the insulating coat, epoxy type resin, polyethylene resin
or the like is usable. Further, if the epoxy type insulating
material including alumina, silica, titanium oxide or the like is
used as the molding material, a specific inductive capacity can be
adjusted somewhat freely in combination with the molded thickness
to optimize the apparatus. Hereafter, a plurality of embodiments
will be described.
Embodiment 1
[0044] FIG. 6 shows an embodiment of a tank type gas insulated
switchgear of the invention. Cylindrical pressure vessels 2, 7a and
7b are filled with a N.sub.2/O.sub.2 mixture gas or dry air of
0.2-0.8 MPa.cndot.abs. A vacuum circuit breaker 1 is contained in
the cylindrical pressure vessel 2, a longitudinal direction of the
cylindrical pressure vessel 2 is arranged parallel to a vertical
direction, and a longitudinal direction of the vacuum circuit
breaker 1 is arranged parallel to the longitudinal direction of the
cylindrical pressure vessel 2. The vacuum circuit breaker 1 is
connected to an operator 3 through an opening and closing operation
rod below the vacuum circuit breaker 1. Further, an arrestor 4 is
arranged under the vacuum circuit breaker 1 to decrease a size of
the apparatus.
[0045] Arranging the longitudinal direction of the vacuum circuit
breaker parallel to the vertical direction causes the following
effects. When a length of a bellows increases in accordance with an
increase of a gaseous pressure, the bellows is bent to a V shape in
response to the opening and closing operation occurs. Therefore,
when the length of the bellows increases, a ring for preventing the
bend needs to be arranged between protruding corners of the
bellows, so that the length of the bellows is further increased.
Maximizing this bend occurs when the bellows extends
perpendicularly to the vertical direction, but by arranging the
bellows parallel to the vertical direction, a number of the rings
for preventing the bellows bend can be decreased to decrease the
length of the bellows and the size of the apparatus.
[0046] A bus bar disconnecting switch 5a and a line disconnecting
switch 5b are connected to each other through a spacer 6 as a gas
partition. A gas compartment containing the disconnecting switches
5 is gaseously separated from a gas compartment containing the
vacuum circuit breaker 1, so that an influence to the other
electric lines can be minimized by opening the disconnecting
switches 5a and 5b when a trouble with the vacuum circuit breaker 1
occurs or an inspection is needed. Further, movable contacts of the
disconnecting switches 5 are formed monolithically respectively
with movable contacts 10a and 10b of a grounding disconnecting
switch to combine the disconnecting switches 5 and the grounding
disconnecting switch with each other, so that a size of the
disconnecting switches and grounding disconnecting switch is
decreased. Further, a longitudinal direction of cylindrical
pressure vessels 7a and 7b containing the disconnecting switches is
arranged parallel to a movable direction of the movable contacts of
the disconnecting switches 5. The longitudinal direction of the
cylindrical pressure vessels 7a and 7b containing the disconnecting
switches 5 is arranged parallel to the longitudinal direction of
the cylindrical pressure vessel 2 containing the vacuum circuit
breaker 1 to decrease the size and weight of the entire switchgear.
Further, a solid insulation such as cable head 9 is applied to the
bus bar 8 and lines to decrease the size of the apparatus and keep
layout flexibility.
[0047] Further, the gaseous pressure in the cylindrical pressure
vessel 2 containing the vacuum circuit breaker 1 is made lower than
the gaseous pressure in the cylindrical pressure vessels 7
containing the disconnecting switches 5 to satisfy both the optimum
miniaturization of the disconnecting switches 5 and the optimum
miniaturization of the vacuum circuit breaker 1 and decrease the
size of the whole apparatus. Additionally, since the electric field
is concentrated at a high voltage shield of the disconnecting
switches 5 and upper and lower electrodes and so forth of the
vacuum circuit breaker 1, these areas to be insulated are coated by
molding with the insulating coat of the epoxy type resin or the
polyethylene resin including filler so that the significant
miniaturization is obtainable without changing the gaseous
pressure.
[0048] Further, by adding a sulfur type smelling agent to the
mixture gas or dry air so that the mixture gas or dry air inserted
into the apparatus becomes smelly, a gas leakage can be detected
rapidly through the smell. The sulfur type smelling agent may be,
for example, diethyl-disulfide, tasha-leaf or dimethyl-sulfide.
Embodiment 2
[0049] FIG. 7 shows another embodiment of a tank type gas insulated
switchgear of the invention. The vacuum circuit breaker (VCB) is
vertically arranged, and is connected to the disconnecting switch
(DS) unit through the gas partition. The line side is connected to
a power cable through a cable head, and a current therethrough is
measured by a current transformer.
[0050] An operator of the VCB is arranged in a box at a right side
of the drawing, and operators of the disconnecting switch (DS) and
the earthed switch (ES) are arranged under the operator of the VCB.
Each of the metallic vessels containing respectively the VCB, DS,
ES and bus bar has a substantially cylindrical shape suitable for
inner pressure. The vessels contain, for example, the dry air with
the minimum pressure of 0.5 Mpa.cndot.abs to form a compact and
light-weight gas insulated switch (GIS) including no global warming
gas.
[0051] In this embodiment, the VCB and the line disconnecting
switch (DSL) are contained in a common gas compartment, and the
insulating compartment for the bus bar disconnecting switch (DSB)
is gaseously isolated from the common gas compartment. In such
structure, each line is great, and 2-4 gas compartments are
arranged. The disconnecting switch DS is of blade type, and a
fulcrum of the movable contact is arranged on the conductive member
at the disconnecting switch side, to include the earthed switch
ES.
[0052] Further, if dry air is used as the insulating gas, rarely
occurring leakage thereof from the apparatus will not affect the
environment, but it is difficult for a gas leaking position to be
found, so that in the worst case, all of the gas compartments need
to be replaced. Therefore, if helium or CF.sub.3CH.sub.2F of
partial pressure ratio of not more than 5% is mixed with the dry
air, the gas leaking position can be found easily by use of a gas
detector so that a recovery can be performed effectively.
Embodiment 3
[0053] FIG. 8 shows an embodiment of a box type C-gas insulated
switch (GIS) of the invention. When the box type vessel is used, a
weight increase in accordance with the increase of the gaseous
pressure is remarkable in comparison with the cylindrical vessel,
and the optimum gaseous pressure is relatively lower in comparison
with the cylindrical vessel, so that a range of the minimum or
rated gaseous pressure optimum for decreasing the size and weight
is between 0.2-0.7 Mpa.cndot.abs. When the vessel is of box shape,
an effect for decreasing an amount of the used gas is lower in
comparison with the cylindrical vessel, but an space efficiency for
mounting the switchgear can be improved.
[0054] In this embodiment, the VCB and the line disconnecting
switch (DSL) are contained in a common gas compartment, and the
insulating compartment for the bus bar disconnecting switch (DSB)
is gaseously isolated from the common gas compartment. In such
structure, each line is great, and 2-4 gas compartments are
arranged. A linear type is applied to the disconnecting switch DS,
and the disconnecting switch DSL on the circuit breaker side and
the earthed switch ES are arrange perpendicularly to the vertical
direction, so that a height of the switch gear is decreased.
Further, it is connected to an underearth power cable through a
cable head CH. Bus bars as gas-insulated bus bars are arranged
parallel to each other to form three phase combined type, and the
mixture gas (including the dry air) is applied to the circuit
breaker compartment and the bus bar disconnecting switch with the
minimum kept gaseous pressure not less than 0.2 Mpa.cndot.abs and
not more than 0.7 Mpa.cndot.abs, so that both the
environment-accordance and the dielectric strength are
obtainable.
[0055] In C-GIS, the box shape causes the increase of the vessel
size and cost in accordance with the increase of the rated gaseous
pressure, and thereby the gaseous pressure is preferably as low as
possible. Therefore, if the dry gas is used as the insulating gas
for example, the minimum kept gaseous pressure or rated gaseous
pressure is made 0.3-0.5 Mpa.cndot.abs, and the insulating coat or
molding is used. In this case, the apparatus can have the same or
less size in comparison with the apparatus with SF.sub.6 gas of the
minimum kept gaseous pressure (0.17 Mpa.cndot.abs).
Embodiment 4
Gas
[0056] FIG. 9 shows an embodiment of a GIS of three phase combined
of the invention. The vacuum circuit breaker 1 is arranged
vertically, and connected to the bus bar disconnecting switch 5a
and the line disconnecting switch 5b. It is connected through the
cable head 9 to the power cable, the breaker 1 is contained in the
metallic vessel 2, the disconnecting switch 5a and the bus bar are
contained in the metallic vessel 7a, and the disconnecting switch
5b is contained in the metallic vessel 7b, so that the size is
decreased. The mixture gas of N.sub.2 and O.sub.2 or the dry air is
used and the rated gaseous pressure is not less than 0.2
Mpa.cndot.abs and not more than 0.8 Mpa.cndot.abs, so that the
environment-accordance and the decrease of the weight and size are
achieved in the GIS. Incidentally, 19 denotes an absorbing agent
container, and 20 denotes a mounting table.
[0057] The vacuum circuit breakers 1 are arranged parallel to the
vertical direction and form a triangle shape, so that an inner
diameter of the cylindrical pressure vessel 2 containing the vacuum
circuit breakers 1 is decreased. The vacuum circuit breakers 1 are
connected to the operator 3 through the operating rods under the
vacuum circuit breakers 1, so that the vacuum circuit breakers 1
are operated to be opened and closed by converting horizontal
movement of the operator 3 to vertical movement. Further, the
arrestor 4 as well as an arrestor release device 18 are arranged
under the line disconnecting switch 5b connected to the cable head
9 so that the miniaturization is obtained and an efficiency of test
with electrically energizing on setting the apparatus is
significantly improved.
[0058] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
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