Dead tank drawout breakers

Details Dead tank drawout breakers Dead tank drawout breakers

2000-05-26

2003-10-07

Friedhofer, Michael (Department: 2832)

Electricity: circuit makers and breakers

Interlocking

Drawout-type switchgear

C361S605000

Reexamination Certificate

active

06630638

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to electrical switching devices. More particularly, the present invention relates to electrical switching devices that have an architecture that facilitates access, maintenance, and repair to the device and reduces substation equipment and real estate.
BACKGROUND OF THE INVENTION
A high voltage circuit breaker is a device used in the transmission and distribution of three phase electrical energy. When a sensor or protective relay detects a fault or other system disturbance on the protected circuit, the circuit breaker operates to physically separate current-carrying contacts in each of the three phases by opening the circuit to prevent the continued flow of current. In addition to its primary function of fault current interruption, a circuit breaker is capable of load current switching. A circuit switcher and load break switch are other types of switching device. As used herein, the expression “switching device” encompasses circuit breakers, circuit switches, dead tank breakers, live tank breakers, load break switches, reclosers, and any other type of electrical switch.
The major components of a circuit breaker or recloser include the interrupters, which function to open and close one or more sets of current carrying contacts housed therein; the operating mechanism, which provides the energy necessary to open or close the contacts; the arcing control mechanism and interrupting media, which interrupt current and create an open condition in the protected circuit; one or more tanks for housing the interrupters; and the bushings, which carry the high voltage electrical energy from the protected circuit into and out of the tank(s) (in a dead tank breaker). In addition, a mechanical linkage connects the interrupters and the operating mechanism.
Circuit breakers can differ in the overall configuration of these components. However, the operation of most circuit breakers is substantially the same. For example, a circuit breaker may include a single tank assembly which houses all of the interrupters. U.S. Pat. No. 4,442,329, Apr. 10, 1984, “Dead Tank Housing for High Voltage Circuit Breaker Employing Puffer Interrupters,” discloses an example of the single tank configuration and is incorporated herein in its entirety by reference. Alternatively, a separate tank for each interrupter may be provided in a multiple tank configuration. An example of a prior art, multiple tank circuit breaker is depicted in
FIGS. 1
,
2
,
3
, and
4
. Circuit breakers of this type can accommodate 72 kV, 145 kV, 242 kV, and 362 kV power sources.
The circuit breaker shown in
FIG. 1
is commonly referred to as a “dead tank” because it is at ground potential.
FIG. 1
provides a front view of a three phase or three-pole circuit breaker having three entrance bushing insulators,
10
,
11
, and
12
, that correspond to each respective phase. The bushing insulators may be comprised of porcelain, composite, or a hardened synthetic rubber sufficient to withstand seismic stresses as well as stresses due to the opening and closing of the interrupter contacts within the device. In high voltage circuit breakers, the bushings for each phase are often mounted so that their ends have a greater spacing than their bases to avoid breakdown between the exposed conductive ends of the bushings.
The circuit breaker is comprised of three horizontal puffer interrupter assemblies enclosed in cylindrical tanks
15
,
16
, and
17
. Current transformer assemblies
20
and
21
(referring to FIG.
2
), which comprise one or more current transformers and their exterior housings, are located underneath the bushing insulators on the exterior of the breaker to facilitate their replacement in the field. Current transformers
20
and
21
measure the outgoing current.
FIG. 2
provides a side view of the three-pole circuit breaker of
FIG. 1
that shows the corresponding exit bushing insulator,
13
, of the interrupter assembly housed in tank
15
.
FIG. 2
illustrates how entrance bushing insulator
10
and exit bushing insulator
13
is associated with tank
15
. The entrance and exit bushing insulators for the interrupters in tanks
16
and
17
(not shown in
FIG. 2
) are arranged in a similar fashion.
Referring to FIG.
1
and
FIG. 2
, the three interrupter tank assemblies are mounted on a common support frame
19
. The operating mechanism that provides the necessary operating forces for opening and closing the interrupter contacts is contained within an operating mechanism housing or cabinet
18
. The operating mechanism is typically mechanically coupled to each of the interrupter assemblies through a common linkage such as a drive cam. The operating mechanisms can be, but are not limited to, compressible springs, solenoids, hydraulic, or pneumatic-based mechanisms.
FIG. 3
is a partial, cross-sectional view of the interrupter assembly housed within cylindrical tank
15
and shown in FIG.
1
and
FIG. 2. A
typical circuit interrupter is comprised of stationary and movable contact assemblies
31
and
23
, respectively. Entrance insulator bushing
10
houses a central conductor
22
which supports movable contact assembly
23
within conductive tank
24
. Movable contact assembly
23
is affixed to an insulator tube
25
through which a linearly operating rod
26
extends. Rod
26
operates movable contact
27
between its open and closed position in a well-known fashion.
Exit insulator bushing
13
houses a central conductor
30
which is connected to the stationary contact assembly
31
and is also supported within conductive tank
24
. An insulator tube
32
extends between the stationary contact assembly
31
and the movable contact assembly
23
.
The interior volume of tank
24
, as well as the entrance and exit insulating bushings
10
and
13
, are preferably filled with an inert, electrically insulating gas such as SF
6
. The electrically insulating gas fulfills many purposes. The arcing contacts within both the stationary and movable contact assemblies are subject to arcing or corona discharge when they are opened or closed. Such arcing can cause the contacts to erode and disintegrate over time. Current interruption must occur at a zero current point of the current waveshape. This requires the interrupter medium to change from a good conducting medium to a good insulator or non-conducting medium to prevent current flow from continuing. Therefore, a known practice (used in a “puffer” interrupter) is to fill a cavity of the interrupter with an inert, electrically insulating gas that quenches the arc formed. During operation of the contacts in assemblies
23
and
31
, a piston, which moves with the movable contact in assembly
23
, compresses the gas and forces it the compressed gas between the separating contacts and toward the arc, thereby cooling and extinguishing it. The gas also acts as an insulator between conductive parts within housing
15
and the wall of tank
24
.
Circuit breakers can switch various devices in an electric utility system. Primarily, these devices include transmission lines, transformers, shunt capacitor banks, and shunt reactors within an electrical substation, power distribution substation, or power transformer and distribution substation. The electrical substation converts the high voltage power carried by long-distance transmission lines into lower distribution voltage that services homes and businesses.
FIG. 4
provides a top view of the circuit breaker of
FIG. 1
as it is commonly installed within an exterior electrical substation. These substations generally cover a large surface area and are not aesthetically pleasing. Given their design, these substations require a great deal of maintenance due to their continuous exposure to climatic and seismic events.
As
FIG. 4
shows, the conductive ends of the bushings are connected to a series of individual air disconnect switches or blades
40
that relate and connect each phase of the circuit breaker to the overhead, electrical substation bus (not shown in FIG.
4
). Air disconnect swi

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