WO1995027298A1

WO1995027298A1 - Interrupter assembly

Info

Publication number: WO1995027298A1
Application number: PCT/US1995/003870
Authority: WO
Inventors: Ian J. Harvey; Lexie W. Crowe
Original assignee: ABB Power T&D Co Inc
Current assignee: ABB Inc USA
Priority date: 1994-03-31
Filing date: 1995-03-29
Publication date: 1995-10-12
Anticipated expiration: 1996-09-30
Also published as: AU2200095A

Abstract

An interrupter assembly (10) comprises an interrupter switch (12) and a condition sensing device (32) operatively coupled to the interrupter switch (12) for sensing a condition of a circuit to which the interrupter assembly (10) is connected, wherein the interrupter switch (12) and the condition sensing device (32) are each embedded within a solid dielectric material. Preferably, the solid dielectric material is a polymer concrete, an epoxy-concrete or an epoxy resin. The condition sensing device (32) may comprise a current sensor (32).

Description

INTERRUPTER ASSEMBLY
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to interrupter devices for high voltage AC distribution systems, and more particularly, to an interrupter assembly comprising an interrupter switch and a condition sensing device, each of which is embedded within a solid dielectric material.

Description of the Prior Art
Vacuum interrupters or switches are employed in many high voltage applications to perform various interrupting and switching functions. For example, vacuum interrupters are used in reclosers, circuit breakers, intelligent switches for automated power distribution, and indoor switchgear. A typical vacuum interrupter comprises a pair of large-surface electrical contacts arranged in an axial configuration and enclosed within an evacuated metalceramic housing. One of the contacts is stationary, while the other moves in an axial direction to open and close the contacts.

In many applications, a number of vacuum interrupters are housed in a single enclosure along with related circuit components. For example, current and/or voltage sensors may b included to provide input to overcurrent protection devices, measuring devices and monitoring relay schemes in the control function of the equipment. Typically, the enclosures are filled with an insulating oil or gas (e. g. SF6) having a high dielectric strength to provide electrical insulation between the vacuum interrupters and other components. Immersing the interrupters and associated sensing devices in an insulating oil or gas allows the individual assemblies to be mounted in closer proximity, thus reducing the overall size and cost of' the equipment.

In some cases, however, the current and voltage sensing devices are mounted separately from the vacuum interrupters to further isolate these components.

Unfortunately, use of insulating oils or gases makes maintenance of the equipment more difficult and often requires special handling equipment. Additionally, there is a growing environmental concern with respect to a number of oil and gas compositions currently employed in the high voltage equipment industry.

Recently, the electrical utility industry has been exploring the use of polymer concrete and similar dielectric materials as a replacement for porcelain in a wide variety of insulating applications. Polymer concretes are composite materials consisting of inorganic aggregates, such as silica, bonded together with a low viscosity organic resin.

The most widely known polymer concrete formulations have been trademarked by the Electric Power Research Institute under the trade name Polysil. Polymer concretes are mechanically strong and have excellent electrical properties, including a Dielectric Strength in the range of 400 V/mil. Additionally, polymer concretes can be easily molded or cast into complex shapes. Epoxy-concrete is a similar solid dielectric material wherein epoxy is used to bond the silica aggregates. Various epoxy resins which do not contain silica aggregates, such as cycloaliphatic epoxy resin, also provide similar properties.

Nonken, U. S. Patent No. 3,812,314, discloses an interrupter assembly for use in underground electric power
distribution systems that comprises a vacuum interrupter switch embedded in a bushing formed of electrically r insulated epoxy resin. However, Nonken does not teach or suggest encapsulating other devices, such as a current sensor, within the bushing to create a single multi-function assembly. I
Reighter, U. S. Patent No. 4,267,402, discloses an insulator formed of polymer concrete that has mounting threads molded directly into the polymer concrete. St-Jean et al., U. S. Patent No. 4,827,370 discloses a cylindrical enclosure formed of epoxy-concrete or polymeric concrete for housing a surge arrester. Lindsey, U. S. Patent No.

4,823,022, discloses a power line insulator formed of
Polysil. A voltage sensor, current sensor and terminal box are embedded in the Polysil during the molding process for the insulator.

Although Nonken teaches embedding a vacuum interrupter in an epoxy resin and Lindsey teaches embedding voltage and current sensing devices in a power line insulator formed of Polysil, the prior art has not recognized the reduced size, ease of maintenance and environmental advantages of combining a vacuum interrupter and a condition sensing device in a single assembly wherein the interrupter and the condition sensing device are each embedded within polymer concrete or a similar solid dielectric material. Such assemblies would eliminate the need for an insulating oil or gas and would allow reduced spacing between adjacent interrupter assemblies in a wide variety of high voltage equipment.

By embedding both the interrupter switch and the condition sensing device in a solid dielectric material, the need to mount these devices separately or provide additional insulation would be eliminated.

SUMMARY OF THE INVENTION
The present invention is directed to an interrupter assembly comprising an interrupter switch and a condition sensing device operatively coupled to the interrupter switch for sensing a condition of a circuit to which the interrupter assembly is connected, wherein the interrupter switch and the condition sensing device are each embedded within a solid dielectric material. Preferably, the solid dielectric material is one of epoxy-concrete and polymer concrete. The condition sensing device may comprise a current sensor, and the interrupter switch may comprise a vacuum interrupter switch.

According to a preferred embodiment of the present invention, the interrupter switch is embedded within a first ; body of solid dielectric material, and the condition sensing device is embedded within a second body of solid dielectric material. The first and second bodies of solid dielectric material are then joined together. Preferably, the movable terminal rod of the interrupter assembly extends at least partially through a substantially cylindrical opening in the second body of solid dielectric material. The interrupter assembly may further comprise a contact terminal disposed at least partially within the second body of solid dielectric material, and a current transfer assembly electrically coupled to the movable terminal rod and to the contact terminal to provide a transfer of current from the movable terminal rod to the contact terminal.

Preferably, the condition sensing device is operatively coupled to the contact terminal within the second body of solid dielectric material in order to sense a condition of a circuit to which the interrupter assembly is connected.

Other features and advantages of the present invention will become evident hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing summary, as well as the following detailed description of the preferred embodiment, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, an embodiment that is preferred, it being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed. In the drawings:
Figure 1 is a sectional view of an interrupter assembly in accordance with a preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings wherein like numerals indicate like elements throughout, there is shown in Figure 1 an interrupter assembly 10 in accordance with a preferred embodiment of the present invention. As shown, in the present embodiment, the interrupter assembly 10 comprises an interrupter switch 12 and a condition sensing device 32, each of which is embedded within a solid dielectric material. The condition sensing device 32 is operatively coupled to the interrupter switch 12 for sensing a condition of a circuit (not shown) to which the interrupter assembly may be connected. According to the present embodiment, the interrupter switch 12 is substantially embedded within a first body 14a of solid dielectric material, and the condition sensing device is embedded within a second body 14b of solid dielectric material.

The first and second bodies 14a, 14b are joined together to form a single assembly. Any suitable means may be employed to join the first and second bodies 14a, 14b. For example, the first and second bodies 14a, 14b may be joined together with an adhesive or glue. Alternatively, the first and second bodies 14a, 14b may be bolted together. Preferably, a sealing compound or gasket material 19 is provided between the first and second bodies 14a, 14b to prevent moisture and other impurities from leaking through the joint.

Preferably, the first and second bodies of solid dielectric material 14a, 14b are each formed of a polymer concrete. As explained above, polymer concretes are composite materials consisting of inorganic aggregates, such as silica, bonded together with a low viscosity organic resin. The most widely known polymer concrete formulations have been trademarked by the Electric Power Research
Institute under the trade name Polysil. Polymer concretes are mechanically strong and have excellent electrical properties, including a Dielectric Strength in the range of 400 V/mil. While polymer concrete is the preferred material, any other solid dielectric material having similar properties may be employed without deviating from the spirit and scope of the present invention. For example, an epoxy concrete could be used.

Alternatively, an epoxy resin without silica aggregates, such as cycloaliphatic epoxy resin, could be used. Cycloaliphatic epoxy resin has a
Dielectric Strength of about 350 V/mil.

The interrupter switch 12 and condition sensing device 32 are embedded within the respective solid dielectric bodies 14a, 14b during suitable molding operations. The overall size and shape of each solid dielectric body 14a, 14b is not limited to that illustrated in Figure 1. Rather, the solid dielectric bodies 14a, 14b may be molded to any desired shape, thereby providing great flexibility in the design of electrical equipment incorporating such assemblies. Projections 28 may be formed on the second body 14b to facilitate clamping of the assembly to electrical equipment (not shown). Additionally, mounting threads (not shown) may be formed in the solid dielectric body 14b for securing the assembly with suitable hardware.

In the present embodiment, the interrupter switch 12 is a vacuum interrupter switch that comprises a pair of large-surface electrical contacts (not shown) disposed within an evacuated housing 15. A stationary terminal rod 16 extends from one end of the housing 15 and emerges from the solid dielectric body 14 to form an upper contact terminal 22. A movable terminal rod 18, sometimes also referred to herein as an"operating rod", extends from the other end of the housing 15 through a substantially cylindrical opening 26 formed in the second body 14b of solid dielectric material. The cylindrical opening 26 is formed in the second body 14b to allow axial movement of the operating rod 18. The distal end 30 of the operating rod 18 may be connected to a suitable operating mechanism (not shown) for opening and closing the contacts (not shown) of the interrupter switch 12.

A contact over-travel spring (not shown) may be provided in the top end 18a of the operating rod.

A current transfer assembly 20 is coupled about the proximal end of the operating rod 18. A lower contact terminal 24 is embedded in the second body 14b of dielectric material such that one end 24a is disposed in the cylindrical opening 26 while the other end 24b protrudes outward from the side of the solid dielectric body 14b. An electrical connection 25 is provided between the current transfer assembly 20 and the lower contact terminal 24. The current transfer assembly 20 operates to transfer current flow from the movable terminal rod 18 to the lower contact terminal 24 and may comprise a roller contact, sliding contact, flexible connector or other suitable device.

When the interrupter assembly 10 is connected to an electrical circuit (not shown), the condition sensing device 32 operates to sense a condition of that circuit. In the present embodiment, the condition sensing device comprises a current sensor 32 that is operatively coupled to the lower contact terminal 24 for measuring the magnitude of current flow in the circuit. Preferably, the current sensing device 32 comprises a ring-type current transformer having its secondary winding wrapped about an annular core.

As illustrated in Figure 1, the current transformer 32 is embedded within the second body 14b of solid dielectric material such that the contact terminal 24 extends axially through the center of the annular core. In this configuration, the contact terminal 24 serves as a singleturn primary of the transformer 32. A lead 34 of the secondary winding of the current transformer runs through the solid dielectric body-and emerges from the bottom end 35 of the assembly 10. The end 36 of the secondary lead 34 can be connected to an overcurrent protection device, a measuring device or a monitoring relay scheme in the control function of an electrical apparatus employing the interrupter assembly 10 of the present invention. Although a ring-type current transformer is preferred, any suitable current sensing device may be employed.

As the foregoing illustrates, the present invention is directed to an interrupter assembly comprising an interrupter switch and a condition sensing device, wherein the interrupter switch and condition sensing device are each embedded in a solid dielectric material. Use of solid dielectric materials allows the condition sensing device to be incorporated into the interrupter assembly without the need for additional insulation. Because solid dielectric materials can be molded or cast to any desired shape, the overall size of electrical equipment incorporating such assemblies can be reduced. Moreover, multiple interrupter assemblies can be spaced in close proximity without the need for an insulating oil or gas. It is understood that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof.

Accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

Claims

WHAT IS CLAIMED IS: 1. An interrupter assembly comprising an interrupter switch and a condition sensing device operatively coupled to the interrupter switch for sensing a condition of a circuit to which the interrupter assembly is connected, wherein the interrupter switch and the condition sensing device are each embedded within a solid dielectric material.

2. The interrupter assembly of claim 1 wherein the solid dielectric material is one of a polymer concrete, an epoxy-concrete and an epoxy resin.

3. The interrupter assembly of claim 1 wherein the condition sensing device comprises a current sensor.

4. The interrupter assembly of claim 1 wherein the interrupter switch comprises a vacuum interrupter switch.

5. The interrupter assembly of claim 1 wherein the interrupter switch is embedded within a first body of solid dielectric material, and the condition sensing device is embedded within a second body of solid dielectric material, the first body of solid dielectric material being joined to the second body of solid dielectric material.

6. The interrupter assembly of claim 5 wherein the interrupter switch has a movable terminal rod extending at least partially through a substantially cylindrical opening in the second body of solid dielectric material.

7. The interrupter assembly of claim 6 wherein the interrupter assembly further comprises a contact terminal disposed at least partially within the second body of solid dielectric material, and a current transfer assembly electrically coupled to the movable terminal rod and to the contact terminal to provide a transfer of current from the movable terminal rod to the contact terminal.

8. The interrupter assembly of claim 7 wherein the condition sensing device is operatively coupled to the contact terminal.

9. The interrupter assembly of claim 7 wherein the condition sensing device comprises a ring-type current transformer having a substantially annular core, and wherein the current transformer is disposed within the second body of solid dielectric material such that the contact terminal extends substantially axially through the center of the annular core.