Electricity: circuit makers and breakers – Pole switch
Reexamination Certificate
2000-07-11
2002-06-25
Luebke, Renee (Department: 2832)
Electricity: circuit makers and breakers
Pole switch
C218S120000
Reexamination Certificate
active
06410867
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to electrical switching devices. More particularly, the present invention relates to electrical switching devices with an improved joint system joining an insulating bushing to a circuit interrupter tank.
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 insulating bushings,
10
,
11
, and
12
, that correspond to each respective phase. The insulating bushings 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 transformers assemblies and
21
(referring to FIG.
2
), which comprise one of more current transformers and their exterior housing, are located underneath the insulating bushings on the exterior of the breaker to facilitate their replacement in field. Current transformers
20
and
21
measure outgoing current.
FIG. 2
provides a side view of the three-pole circuit breaker of
FIG. 1
that shows the corresponding exit insulating bushing,
13
, of the interrupter assembly housed in tank
15
.
FIG. 2
illustrates how entrance insulating bushing
10
and exit insulating bushing
13
is associated with tank
15
. The entrance and exit insulating bushings for the interrupters in tanks
16
and
17
(not shown in
FIG. 2
) are arranged in a similar fashion. The devices, illustrated in
FIGS. 1 through 3
, have
3
pairs of entrance and exit bushing insulators, or a total of
6
bushing insulators.
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, 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 insulating 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 insulating 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 insulating 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 insulating 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 insulating 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 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
.
FIG. 4
provides a detailed, cross sectional view of how an insulating bushing
33
, similar to entrance insulating bushing
10
and exit insulating bushing
13
in FIG.
1
through
FIG. 3
, is associated with tank
34
in the prior art. Insulating bushing
33
is joined to tank
34
through the use of a mounting flange,
35
, and a plurality of fasteners
36
. Fasteners
36
are inserted parallel to the axis of mounting flange
35
(and the axis of insulating bushing
33
) and spaced equidistantly around the periphery of flange
35
. The diameter of mounting flange
35
must be sufficient to allow adequate space for fasteners
36
. Moreover, the material selected for flange
36
must be suitable to withstand continuous exposure to the weather.
In addition for the joint being strong, it is also important that the joint between the insulating bushing
33
and tank
34
be gas tight and moisture tight. Both insulating bushing
33
and tank
34
have hollow interiors that are preferably filled with an inert, electrically insulating
ABB Inc.
Luebke Renee
Nguyen Nhung
Woodcock & Washburn LLP
LandOfFree
Bolted conical loading joint system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bolted conical loading joint system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bolted conical loading joint system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2912281