High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Air-current blowout
Reexamination Certificate
2003-03-14
2004-09-07
Donovan, Lincoln (Department: 2832)
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Air-current blowout
C218S059000, C218S043000
Reexamination Certificate
active
06787725
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas insulated switchgear, and particularly, to a switching mechanism of a circuit breaker for a gas insulated switchgear.
2. Description of the Background Art
A high voltage gas insulated switchgear having tens of kV or hundreds of kV rate voltage related to the present invention generally includes a circuit breaker, a current transformer, a disconnecting switch for load line, a disconnecting switch for power source line and a bushing for electrical insulation. The gas insulated switchgear is installed on an electrical power supplying line and is used when a circuit is opened/closed for testing electrical equipment or the electrical power supplying line in a normal usage status. Also, the gas insulated switchgear breaks the circuit between electric source and load when abnormal current due to ground faults or short circuit, etc., is generated in order to protect electrical power supplying system and electrical load apparatuses safely.
Presently, in most countries, in order to operate the electric power supplying system, a six Fluoric Sulfur (abbreviated as SF
6
) gas insulated switchgear or a switchgear called as an SF
6
gas ring main unit is installed on the ground or underground as a branching apparatus and a dividing apparatus of the lines.
One of the principal functions of the high voltage switchgear using the SF
6
gas as the insulating material is a function of extinguishing rapidly an arc generated when the circuit is opened or closed.
There are arc extinguishing methods used recently such as an electromagnetic arc rotating type, a thermal expansion type, an arc dividing grid type and a puffer type, etc.
The puffer type can be divided into a straight moving type and a rotating type, and the present invention relates to the straight moving type arc extinguishing method.
As a reference, arc discharging means a status that some of electrode material is evaporated to become gas, and can be referred as gas discharging. In addition, since the electricity is somewhat remained on the end of a moving arc contactor and a fixed arc contactor right after the flowing of electricity is blocked and generates arc discharging to interrupt the electric current blocking, the arc generated when the circuit is closed, that is, tripped in the gas insulated switchgear should be extinguished effectively and rapidly to protect the lines and the load apparatuses safely.
FIG. 1
is a brief view showing an outer appearance of a conventional gas insulated switchgear,
FIG. 2
is a cross-sectional view showing inside of a circuit breaker in the conventional gas insulated switchgear,
FIG. 3
is a cross-sectional view showing a switching mechanism which is a principal part of the breaker in the conventional gas insulated switchgear, showing the closed circuit, that is, the status of circuit connection, and
FIG. 4
is a cross-sectional view showing the switching mechanism which is a principal part of the breaker in the conventional gas insulated switchgear, showing opened circuit, that is, the status of circuit breaking.
As shown in
FIG. 1
, the gas insulated switchgear
1
comprises: a breaker
10
for breaking a circuit; a current transformer
20
for detecting amount of current flowing on the circuit; a disconnecting switch
30
for load line for breaking connection to load side; a disconnecting switch
40
for power source line for breaking connection to power source side; and a bushing
50
for insulating an electric terminal.
As shown in
FIG. 2
, the breaker
10
of the gas insulated switchgear
1
comprises: conductors C
1
and C
2
connected to power source side or to the load side; and a switching mechanism connected to the conductors C
1
and C
2
to connect or break the circuit, and the switching mechanism can be divided into a fixed portion
10
A and a movable portion
10
B.
As shown in
FIGS. 3 and 4
, the switching mechanism which is a principal part of the circuit breaker
10
for the gas insulated switchgear
1
is divided into the fixed portion
10
A and the movable portion
10
B, and the fixed portion
10
A comprises a fixed contactor
11
and a fixed arc contactor
12
located in the fixed contactor
11
.
In addition, the movable portion
10
B comprises: a main cylinder
13
; a movable cylinder
14
movably installed on an inner upper part of the main cylinder
13
, the movable cylinder
14
including SF
6
gas therein; a cylinder rod
15
located in a compressing chamber
14
a
of the movable cylinder
14
and movable with the movable cylinder
14
; a sealing member
16
fixedly installed in the movable cylinder
14
so that an outer circumferential surface of the cylinder rod
15
is abutted thereon for sealing the compressing chamber
14
a
; a connecting rod
17
installed to be connected to a lower part of the cylinder rod
15
, and connected to an actuator device (not shown) such as a hydraulic system in order to supply power to the switching mechanism according to a command signal of circuit breaking; a movable arc contactor
18
installed on the upper part of the cylinder rod
15
and selectively connected/separated to/from the fixed arc contactor
11
; and a nozzle
19
installed on an upper part of the movable cylinder
14
. The movable cylinder
14
and the cylinder rod
15
are connected to each other by a connecting member such as a ring member for connecting (not shown), and therefore, these can move together.
In addition, the conductors C
1
and C
2
for connecting circuit with the power source or with the load are connected to the fixed contactor
11
of the fixed portion
10
A and to the main cylinder
13
of the movable portion
10
B respectively, as shown in FIG.
2
.
In a normal status that the normal current flows in the circuit between the power source and the load, the movable arc contactor
18
is contacted to the fixed arc contactor
12
to maintain the closed circuit status as shown in
FIG. 3
, and the conductors C
1
and C
2
are connected electrically.
On the other hand, when abnormal large current flows due to ground fault or short circuit generated in the circuit between the power source line and the load line, a controller (not shown) recognizes it and outputs a command signal of circuit breaking, and accordingly, the actuator device (not shown) pulls the connecting rod
17
in the arrow direction and the cylinder rod
15
connected to the connecting rod
17
is also moved in the arrow direction. At that time, the movable arc contactor
18
located on the upper part of the cylinder rod
15
and the movable cylinder
14
connected to the cylinder rod
15
are also moved in the arrow direction.
The compressing chamber
14
a
is moved downward together with the cylinder rod
15
, and at that time, since the sealing member
16
is fixed, volume of the compressing chamber
14
a
is reduced rapidly and the movable arc contactor
18
is separated from the fixed arc contactor
12
simultaneously.
As described above, at the moment that the movable arc contactor
18
is separated from the fixed arc contactor
12
, the SF
6
gas in the compressing chamber
14
a
is injected through the nozzle
19
by the pressure to extinguish the arc. However, since the arc generated at the moment that the movable arc contactor
18
is separated from the fixed arc contactor
19
, is the gas of high temperature and high pressure, the pressure of the arc is higher than that of the SF
6
gas injected through the nozzle
19
, and therefore, the injection of SF
6
gas is not made effectively. In addition, when the arc gas is expanded, there is a limit of space to accept the gas, and therefore it is difficult to extinguish the arc rapidly.
Therefore, the function of extinguishing the arc by injecting a large amount of the SF
6
gas in the compressing chamber
14
a
rapidly, that is, the arc extinguishing speed is an important function of the gas insulated switchgear, and a lot of researches are being proceeded.
A method for increasing SF
6
gas injecting pressure by increasing the gas pressur
Kang Sung-Mo
Kim Duk-Rae
Donovan Lincoln
Fishman M.
Greenblum & Bernstein P.L.C.
LG Industrial Systems Co. Ltd.
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