GB1573713A

GB1573713A - High-voltage electrical switchgear

Info

Publication number: GB1573713A
Application number: GB5147976A
Authority: GB
Original assignee: Northern Engineering Industries PLC
Current assignee: Rolls Royce Power Engineering PLC
Priority date: 1977-12-09
Filing date: 1977-12-09
Publication date: 1980-08-28

Description

(54) HIGH-VOLTAGE ELECTRICAL SWITCHGEAR (71) We, NORTHERN ENGINEER ING INDUSTRIES LIMITED, a British Company of NEI House, Regent Centre, Newcastle-upon-Tyne NE3 3SB, Tyne and Wear, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a high-voltage circuit-breaker of the type comprising one or more interrupter units for operation within an insulating fluid medium. The fluid medium may for example, be compressed air or SF6 gas, or a liquid medium such as oil. Circuit-breakers of this type will hereinafter be referred to as circuit breakers of the type specified". The invention is particularly, although not exclusively, concerned with means for supporting the interrupter assembly within the pressure vessel and forming electrical connections to associated line terminals for connection to a high-voltage circuit.

The invention is particularly although not exclusively applicable to circuit-breakers wherein the mechanical drive is axially in-line with the interrupter assembly and operates in a plane transverse to the terminal bushing insulators. In the design of such circuit-breakers the following primary objectives are to be aimed at: (a) minimising transverse loads on the terminal bushing insulators. which loads produce complex stress conditions in the insulating material from which the bushing insulators are manufctured; (b) ensuring substantially equal loading of each of the supporting insulator bushings, (c) accommodating dimensional changes resulting from differential thermal suspension between the outer containinghousing or pressure vessel and the inner interrupter assembly; (d) providing an arrangement which is simple and allows ready access to the internal assembly for constructional and maintenance purposes.

According to the present invention a high-voltage circuit-breaker of the type specified includes an interrupter assembly having one or more interrupter units actuated by an operating drive, the interrupter assembly being suspended at opposite ends of its length from the ends of associated line terminal conductors of the circuit-breaker by means of a pair of releasable sliding connections each comprising a fixed connector member secured to the end of the associated line terminal conductor, and a co-operating withdrawable connector member slidably supported by the fixed connector member and secured to the associated end of the interrupter assembly, the axes of sliding of the releasable connections being parallel to one another and transverse to the lengths of the line terminal conductors so that each of the supported ends of the interrupter assembly can be displaced, relative to the associated terminal conductor, in a direction transverse to the length of the associated line terminal conductor.

The axes of sliding of the releasable connection may conveniently be parallel to a line joining the ends of the line terminal conductors.

For example, the releasable connections may be of the sliding plug-and-socket type arranged with their sockets facing in the same direction, so that the complete interrupter assembly can be withdrawn from the line terminals by appropriate linear movement. The releasable connections preferably provide electrical interconnection between the line terminal conductors and the ends of the interrupter assembly, as well as supporting them mechanically.

The invention is especially beneficial in cases where the line of action of the operating drive for the interrupter units of the assembly is parallel to, e.g. aligned with, the longitudinal axis of the interrupter assembly, which axis may also be at right angles to the longitudinal axes of the line terminal conductors adjacent the releasable connections.

The circuit-breaker may be provided with terminal bushings of the ceramic type having a central conductor, which conductors constitute the line terminal conductors from which the interupter assembly is supported by the releasable connections referred to.

The invention may be carried into practice in various ways, but one specific embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing in which: Figure 1 is a diagrammatic partial crosssectional elevation through a single phase of a gas-filled circuit-breaker comprising two series-connected interrupters, and Figure 2 is a detail of the plug-and-socket arrangement employed in the circuitbreaker shown in Figure 1.

In the embodiment illustrated diagrammatically in Figure 1, a high-voltage circuit breaker comprises two puffer-type interrupters 10A and 10B each of the type described in our British Patent Application No. 44231/ 74 (Serial No. 1525460) the two interrupters being mounted within an earthed-metal pressure vessel 11 which is of a generally cylindrical form and has two insulating lead-in bushings 14 mounted on flanges 13 on circular chambers 12 at the top of the pressure vessel 11. One end of vessel 11 has a flanged access cover-plate 11a which is bolted to a flange on the vessel 11 in a pressure tight manner. The other end of pressure vessel 11 has fixed to it a cylindrical chamber 11B which contains the interrupter operating linkage referred to below. This chamber 11B is also fixed in a pressure-tight manner to the vessel 11.

The tank 11 contains a pressurised insulating gaseous medium, for example, SF6 at a pressure of 70 to 85 p.s.i. gauge. The two interrupters 10 are connected electrically in series with one another and are supported in electrical connection with the lower ends of copper conductors 15 of the lead-in bushings 14 by means of fixed plug and relatively-withdrawable socket assemblies which will be described below with reference to Figure 2. The upper ends of the conductors 15 constitute the phase terminals of that phase of the circuit-breaker. Referring to Figure 1, the fixed plug which is permanently electrically connected to each conductor 15 is contained with an electrostatic stress-shield 16, and the withdrawable socket which is electrically connected to the interrupter assembly is contained within an electrostatic stress-shield 17.

The lower end of each bushing conductor 15 is supported within a conical insulating barrier shroud 18 which also has the function of separating the gas within bushing 14 from the gas within the main enclosure 11 since the latter may be contaminated by arcing by-products.

In order to simplify the drawing, full-line details of only one interrupter, namely 10B, are shown in Figure 1. Each interrupter 10A and 10B is generally as described in our pending British Patent Application No.

44231/74 (Serial No. 1525460-) and generally comprises a fixed contact 19 and a moving contact assembly 20; each complete interrupter 10A and 10B is contained within an insulating support chamber 21 and fixed between cylindrical conducting supporting chambers 22. A dished baffle 23 is formed in at least one end wall of each chamber 22, the baffle being provided with a fixed surface facing inwardly towards the fixed and moving contacts. Thus, the extreme lefthand chamber 22 as seen in Figure 1 has one baffle 23, the centre chamber 22 has two baffles 23, and the extreme righthand chamber has one baffle 23, the latter baffle only being shown. The function of the fins on baffles 23 is to separate and trap particles of solid arcing products produced by the circuit-interrupting co-action of the fixed and moving contacts 19, 20, as described below.

A primary drive for the moving contact assemblies 20 is provided by an insulated drive shaft 24 which is connected to one of two insulated cross-arms 25, and the two cross-arms 25 are connected together by insulated drive tubes 26 which are pinjointed at their ends to the cross-arms. Each moving contact assembly 20 is connected to a respective one of the cross-arms 25 by means of a shaft 24a. The extreme right hand end of the drive shaft 24 in Figure 1 is connected to an operating drive crank 29 which is driven by an external operating mechanism, not shown. The connection to the external mechanism is made through pressure-tight seals in the pressure vessel 11.

The extreme right-hand support cylinder 22 is connected rigidly to the end of the pressure vessel 11 by means of an insulating cylinder 27, and a pair of wheel supports 28 are provided to facilitate insertion and withdrawal of the complete assembly of interrupters 10A and 10B for constructional and maintenance purposes. This would be done by withdrawing the complete assembly towards the left in Figure 1 after the end cover 11a has been removed, the plug-andsocket connections in the stress shields 16, 17 separating to permit this withdrawal. The electrical and mechanical support and connection of the interrupter assembly to the lead-in bushings is provided by means of the arrangement shown in greater detail in Figure 2. The electrostatic stress-shields 16 and 17, Figure 1, respectively contain the fixed plugs 30 and withdrawable sockets 31, one pair of which is shown in Figure 2. The fixed plug assembly 30 comprises an electrically-conducting guide pin 32 whose head is fixed to the end of the bushing conductor 15 by a nut 33. A plurality of spring-loaded contact fingers 34 are provided for electrical connection with the relatively-withdrawable socket 31 which comprises a cylindrical conducting body 35 having an axial bore 36 which accommodates the guide pin 32. An insulating bush 37 is contained within bore 36 and insulates the socket 35 from the guide pin 32, and this ensures that the current flow is only through the contact fingers 34 to the outside surface of the socket body 35. The socket body 35 is connected to the support cylinder 22 by end flange 38.

The arrangement of plug-and-socket connections 30. 31 described above ensures that the principal loads on the associated bushing insulators in service are simple loads of low order which act in-line with the axis of the insulator and. therefore. produce simple and predictable stress conditions. The sliding contact facility provided by the plugand-socket connections 30, 31 ensures good electrical connection when dimensional changes occur due to differential thermal expansion and contraction between the outer pressure vessel and the interrupter assembly. The arrangement also reduces the requirement for close tolerancing of assemblies during the manufacturing process.

The interrupter operating assembly ensures that the high dynamic mechanical loads are carried by the insulating elements 27. 21 mounted in-line with the primary drive rod '4. which also ensures simple and predictable stress conditions.

The circuit-breaker as shown in Figure 1 is in the open-circuit position: the circuitbreaker is closed by moving the primary drive-rod 24 to the left in Figure 1 by means of the crank 29, driving the moving contact assemblies 20 via the cross-arms 25 and drive tubes '6 and 24a until the fixed and moving contacts 19. 20 are in secure electrical connection. The electrical path through this particular phase is thus closed. The circuit-breaker is "tripped" to open the circuit by movement of the operating mechanism in the opposite direction. The operating mechanism. not described, may be of the mechanical charged spring type, hydraulic or pneumatic. and the operating crank 29 may be mounted on a transverse drive shaft which is common to a number of phases similar to that described with reference to Figure 1.

This invention is not limited to the specific form of interrupter described nor to the specific form of supporting assembly described by way of example only. The insulating medium may be some alternative fluid, for example, compressed air or oil. The invention may also be applied-to metal-clad switchgear arrangements where bushing insulators as described above are not applicable.

WHAT WE CLAIM IS 1. A high-voltage circuit-breaker of the type specified, which includes an interrupter assembly having one or more interrupter units actuated by an operating drive, the interrupter assembly being suspended at opposite ends of its length from the ends of associated line terminal conductors of the circuit-breaker by means of a pair of releasable sliding connections each comprising a fixed connector member secured to the end of the associated line terminal conductor, and a co-operating withdrawable connector member slidably supported by the fixed connector member and secured to the associated end of the interrupter assembly, the axes of sliding of the releasable connections being parallel to one another and transverse to the lengths of the line terminal conductors so that each of the supported ends of the interrupter assembly can be displaced, relative to the associated terminal conductor, in a direction transverse to the length of the associated line terminal conductor.

2. A circuit-breaker as claimed in Claim 1 in which the releasable connections provide electrical inter-connection between the line terminal conductors and the ends of the interrupter assembly which they support.

3. A circuit-breaker as claimed in Claim 1 or Claim 2, in which the axes of sliding of the releasable connections are parallel to a line joining the ends of the associated line terminal conductors.

4. A circuit-breaker as claimed in Claim 1 or Claim 2 or Claim 3, in which the releasable connections are of the plug-andsocket type arranged with their sockets facing in the same direction.

5. A circuit-breaker as claimed in Claim 2 and Claim 4 in which electrical insulation is provided between the plug and the socket of each releasable connection at their slidably-interengaged surfaces, and in which the electrical connection between conducting parts of the fixed and withdrawable connector members is afforded by slidable electrical contacts.

6. A circuit-breaker as claimed in any one of the preceding Claims, in which the line of action of the operating drive for the interrupter assembly is parallel to, for example aligned with, the longitudinal axis of the interrupter assembly.

7. A circuit-breaker as claimed in any one of the preceding Claims, in which the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Figure 2. The electrostatic stress-shields 16 and 17, Figure 1, respectively contain the fixed plugs 30 and withdrawable sockets 31, one pair of which is shown in Figure 2. The fixed plug assembly 30 comprises an electrically-conducting guide pin 32 whose head is fixed to the end of the bushing conductor 15 by a nut 33. A plurality of spring-loaded contact fingers 34 are provided for electrical connection with the relatively-withdrawable socket 31 which comprises a cylindrical conducting body 35 having an axial bore 36 which accommodates the guide pin 32. An insulating bush 37 is contained within bore 36 and insulates the socket 35 from the guide pin 32, and this ensures that the current flow is only through the contact fingers 34 to the outside surface of the socket body 35. The socket body 35 is connected to the support cylinder 22 by end flange 38. The arrangement of plug-and-socket connections 30. 31 described above ensures that the principal loads on the associated bushing insulators in service are simple loads of low order which act in-line with the axis of the insulator and. therefore. produce simple and predictable stress conditions. The sliding contact facility provided by the plugand-socket connections 30, 31 ensures good electrical connection when dimensional changes occur due to differential thermal expansion and contraction between the outer pressure vessel and the interrupter assembly. The arrangement also reduces the requirement for close tolerancing of assemblies during the manufacturing process. The interrupter operating assembly ensures that the high dynamic mechanical loads are carried by the insulating elements 27. 21 mounted in-line with the primary drive rod '4. which also ensures simple and predictable stress conditions. The circuit-breaker as shown in Figure 1 is in the open-circuit position: the circuitbreaker is closed by moving the primary drive-rod 24 to the left in Figure 1 by means of the crank 29, driving the moving contact assemblies 20 via the cross-arms 25 and drive tubes '6 and 24a until the fixed and moving contacts 19. 20 are in secure electrical connection. The electrical path through this particular phase is thus closed. The circuit-breaker is "tripped" to open the circuit by movement of the operating mechanism in the opposite direction. The operating mechanism. not described, may be of the mechanical charged spring type, hydraulic or pneumatic. and the operating crank 29 may be mounted on a transverse drive shaft which is common to a number of phases similar to that described with reference to Figure 1. This invention is not limited to the specific form of interrupter described nor to the specific form of supporting assembly described by way of example only. The insulating medium may be some alternative fluid, for example, compressed air or oil. The invention may also be applied-to metal-clad switchgear arrangements where bushing insulators as described above are not applicable. WHAT WE CLAIM IS

1. A high-voltage circuit-breaker of the type specified, which includes an interrupter assembly having one or more interrupter units actuated by an operating drive, the interrupter assembly being suspended at opposite ends of its length from the ends of associated line terminal conductors of the circuit-breaker by means of a pair of releasable sliding connections each comprising a fixed connector member secured to the end of the associated line terminal conductor, and a co-operating withdrawable connector member slidably supported by the fixed connector member and secured to the associated end of the interrupter assembly, the axes of sliding of the releasable connections being parallel to one another and transverse to the lengths of the line terminal conductors so that each of the supported ends of the interrupter assembly can be displaced, relative to the associated terminal conductor, in a direction transverse to the length of the associated line terminal conductor.

longitudinal axis of the interrupter assembly is at right angles to the longitudinal axes of the line terminal conductors at their end portions adjacent to the releasable connections.

8. A circuit-breaker as claimed in any one of the preceding Claims, which is provided with terminal bushings of the ceramic type each having a central conductor, which central conductors constitute the line terminal conductors.

9. A circuit-breaker as claimed in Claim 8 in which the interrupter assembly is suspended in a surrounding earthed vessel filled with insulating fluid, for example, SF6 gas, the line terminal conductors extending through the wall of the vessel and being insulated therefrom by their ceramic bushings.

10. A circuit-breaker as claimed in any one of the preceding Claims in which the interrupter assembly comprises a pair of interrrupter units axially aligned end-to-end and electrically and mechanically connected in series for joint operation by means of an operating drive member connected to one end of the pair, the line of action of the drive member being coaxial with the interrupter units.

11. A high-voltage circuit-breaker substantially as specifically described herein with reference to the accompanying drawings.