Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
  • H01H33/60—Switches wherein the means for extinguishing or preventing the arc do not include separate means for obtaining or increasing flow of arc-extinguishing fluid
  • H01H33/66—Vacuum switches
  • H01H33/666—Operating arrangements
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
  • H01H33/02—Details
  • H01H33/28—Power arrangements internal to the switch for operating the driving mechanism
  • H01H33/30—Power arrangements internal to the switch for operating the driving mechanism using fluid actuator
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
  • H01R13/00—Details of coupling devices of the kinds covered by groups H01R12/70 or H01R24/00 - H01R33/00
  • H01R13/46—Bases; Cases
  • H01R13/53—Bases or cases for heavy duty; Bases or cases for high voltage with means for preventing corona or arcing
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02B—BOARDS, SUBSTATIONS OR SWITCHING ARRANGEMENTS FOR THE SUPPLY OR DISTRIBUTION OF ELECTRIC POWER
  • H02B13/00—Arrangement of switchgear in which switches are enclosed in, or structurally associated with, a casing, e.g. cubicle
  • H02B13/02—Arrangement of switchgear in which switches are enclosed in, or structurally associated with, a casing, e.g. cubicle with metal casing
  • H02B13/035—Gas-insulated switchgear
  • H02B13/0354—Gas-insulated switchgear comprising a vacuum switch
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
  • H01H33/60—Switches wherein the means for extinguishing or preventing the arc do not include separate means for obtaining or increasing flow of arc-extinguishing fluid
  • H01H33/66—Vacuum switches
  • H01H33/662—Housings or protective screens
  • H01H33/66207—Specific housing details, e.g. sealing, soldering or brazing
  • H01H2033/6623—Details relating to the encasing or the outside layers of the vacuum switch housings
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
  • H01H33/02—Details
  • H01H33/24—Means for preventing discharge to non-current-carrying parts, e.g. using corona ring

Definitions

• the present invention is concerned with high voltage switching devices , particularly as might be used in electric power distribution systems, eg for the control of cable circuits and the protecti on of transformers provided at local sub-stations .
• each sub-station distribution transformer is spurred off the ring via an HBC fuse and switch arrangement.
• a fault in the transformer resulting in fault current being drawn through the fuse operates the fuse .
• the connection to- the distribution transformer is made at a point on the ring main between two series connected oil immersed switches.
• the switch associated with the fuses is arranged to open auto ⁇ matically in response to the operation of the HBC fuse . Thus the transformer is isolated.
• connection is made between a first male portion, which is formed with a frustoconical insulating bushing, and a second female receptacle portion, which has an internally frustoconical aperture into which the male portion fits.
• a central connecting element typically a screw threaded plug at the tip* of the male portion makes electrical connection with a connecting element, typically a screw threaded hole, set at the base of the female portion.
• the frustoconical surfaces mate together to form a tight seal.
• a connection of this kind will be referred to hereinafter as a high voltage connection as hereinbefore defined.
• terminal bushings on electrical equipment, such as distribution transformers, which form the male portions of high voltage connections as hereinbefore defined.
• a high voltage switching device comprises an outer covering of an electrically conductive material, a vacuum switch and a switch operating mechanism mounted within the covering.
• solid electrical insulation material encapsulating the switch and operating mechanism and insulating them from the covering, an aperture in the covering, said solid insulation material being shaped in association with said aperture to form a female receptacle portion for receiving through said aperture the insulated bushing of the male portion of a high voltage connection as hereinbefore defined, and a conductive connecting element for the female receptacle portion, encapsulated in the insulation material and connecting to one terminal of the vacuum switch.
• a vacuum switch encapsulated by solid insulation material provides a compact, relatively cheap, but nevertheless highly serviceable device readily meeting the required standards for such devices.
• a female receptacle portion of a high voltage connection as hereinbefore defined, great advantage can be made of the compactness and attendent lightness of the switching device.
• the female receptacle portion can be connected directly on to the terminal bushing of a distribution transformer or other item of electrical equipment.
• the mounting is effected by connecting the female receptacle portion of the device on to an existing, bushing of the electrical equipment.
• the switching device need not be in fact connected directly to the terminal bushing of the electrical equipment. It is a known practice for several connections to be made to a bushing using successive high voltage connections as hereinbefore defined in line. T connectors are known for this purpose whereby a first T connector, eg carrying one cable end of a ring- main, can be connected directly to the transformer bushing, and then the switching device can be connected by means of an intermediate bushing to the other connection port of the T member..
• the switching device or devices will normally be connected first to the transformer bushing.
• electrically conductive elements are provided within said covering moulded in contact with high voltage carrying metallic components to reduce electric field concentrations resulting from angularity of the metallic components, said elements being themselves insulated from the covering by the solid insulation material.
• said operating mechanism is wholly encapsulated within said covering and non mechanical actuating means are provided to initiate operation of the mechanism from outside the covering.
• This arrangement has no mechanical operating lever extending from the covering with its attendant insulation breakdown problems. All mechanical elements are entirely housed within the covering and actuation is provided by non mechanical means which may be solidly sealed to prevent ingress of moisture.
• a high voltage switching device comprises an outer covering of an electrically conductive material, a vacuum switch and a switch operating mechanism mounted within the covering, solid electrical insulation material encapsu ⁇ lating the switch and operating mechanism and insulating them from the covering, and at least one conductive connecting element encapsulated in the insulation material and connected to one terminal of the vacuumm switch to enable an external high voltage connection to be made to said one terminal, wherein said operating mechanism is wholly encapsulated within said covering and non mechanical actuating means are provided to initiate operation of the mechanism from outside the covering.
• hydraulic means within said covering are provided and are conveniently employed with a hydraulic-pneumatic interface mounted -exterior to said covering. This permits the hydraulic means to be completely sealed and the hydraulic pressure to be produced from a source of pneumatic pressure.
• the pneumatic pressure may be derived from an chemical charge detonated when operation of the switch is required.
• the switch may be independently operable to open and to close or may be normally in one state and irreversibly operable to change to the other state.
• the switching device may be configured as an in line switch between high voltage cables connected by means of two said female receptacl'e portions, eg a circuit breaker or isolating switch, or a sectionalising switch. Instead the switching device may be formed with a protruding bushing forming a male portion, for the connection thereto of one of the cables.
• the switching device may be configured as a fault throwing switch with the second contact of the vacuum switch being connected to an earth conductor.
• the switching device may then have two said female receptacle portions with said connecting means providing through connection means enabling respective high voltage connections ' to be made in series by means of- the two female portions and connecting the first contact of the vacuum- switch to the through connection means.
• the covering is T-shaped ' having said female receptacle portions in opposite ends of the cross arm of the T and the vacuum switch and the operating mechanism housed in the upright of the T with the earth conductor extending from the bottom end of said upright.
• T-shaped and elbow shaped connectors are becoming established as a convenient way of connecting cable tails to transformers and a fault throwing switch provided in a T-shaped covering similar to a T-shaped connector housing can most conveniently be mounted directly to the transformer so that the high voltage supply to the transformer passes through the cross arm of the T via the through connection means.
• the earth conductor emerging from the upright of the T is solidly connected to earth to provide for the earth fault current on closing of the fault throwing switch.
• An elbow shaped covering may be used for a fault throwing switch where through connection of the high voltage line is not required.
• a vacuum switch has ideal characteristics for use as a fault throwing switch in that when held open it has an adequate breakdown voltage and can be operated with high reliability. Furthermore the vacuum switch is extremely compact for its purpose.
• apparatus for protecting a ground mounted electrical power distribution transformer in a distri ⁇ bution system comprises, at the transformer installation, a fault throwing switch, which is normally open circuit, connected between one phase of the high voltage. supply, to the transformer and earth and arranged to close in response to a control signal to make a closed circuit resulting in earth fault current and fault detection means to generate said Control signal on detecting a fault current in any phase of the high voltage supply to the transformer, and, at a remote source installation supplying a plurality of said transformers on a common high voltage supply line, a circuit breaker responsive to an earth fault current in any phase of the line to .isolate the line.
• the above arrangements can provide secure protection for distribution transformers by detecting fault currents locally at the transformer and in response thereto initiating an earth fault current which can be detected remotely at a source installation, typically the primary sub-station.
• the installation at each of the distribution transformers of the necessary fault throwing switch and fault detection means can be very much cheaper than the existing practice of installing HBC fuse and switch combinations. It is recognised that the arrangement proposed in the present invention has the effect of temporarily isolating an entire high voltage supply line, including several distribution transformers (local sub-stations), but this is considered an entirely acceptable penalty in view of the low number of transformer faults expected.
• the circuit breaker at the source installation is an auto-reclosing type arranged to reclose after a predetermined time delay and there is provided at the transformer installation for each ' phase of the high voltage supply, a respective sectiona ⁇ lising switch which is normally closed to connect the respective phase of the high voltage supply line to the transformer, said sectionalising switch for said one phase being located to carry said earth fault current through the fault throwing switch, and control means responsive to said fault signal and subsequent cessation of the earth fault current on isolation of the line by the circuit breaker to open the sectionalising switches, to isolate the transformer from the line before reclosing of the circuit breaker.
• This arrangement provides automatic isolation of the faulted distribution transformer.
• fault detection means has been described as arranged to detect fault currents in any phase of the high voltage supply to the transformer.
• the fault detection means may additionally be arranged to generate said control signal on detecting faults in the low voltage connections to the transformer and the low voltage winding of the transformer. Ideally, any imbalance of energy entering or leaving the transformer is detected. In this way .full protection of the transformer can be provided.
• Figure 1 is a schematic diagram of an electrical power distribution system incorporating distribution transformer detection apparatus embodying the present invention
• Figure 2 is a schematic diagram illustrating the installation of a fault throwing switch at a distribution transformer installation
• Figure 3 is a schematic diagram illustrating additionally the provision of a sectionalising switch at the transformer installation
• Figure 4 is a more detailed cross-sectional view in elevation of a fault throwing switch provided in a T-shaped covering
• Figure 5 is a cross-sectional view of part of the switch of Figure 4 showing the actuating mechanism 'of the switch;
• Figure 6, 7 and 8 are plan views of parts of the mechanism shown in Figure 5 and
• Figure 9 is a cross sectional view of a circuit breaker provided in an "in-line" covering shape together with a block schematic diagram of control circuitry.
• an 11 kV ring main 10 is shown looping from a primary sub-station 11.
• a number of local sub-stations 12, 13, 14, 15 etc, are shown connected into the ring main 10.
• the main is normally held open at one point 25.
• the ring main is connected to a distribution transformer 16 to step the voltage down to the local mains voltage.
• a fault throwing switch 17 is provided ( rmecting to earth at least ene phase of the high voltage input lines to the transformer 16.
• the fault throwing switch is normally open as shewn in the drawing and is designed to withstand the line voltage, particularly 11 kV, of the ring main 10.
• a fault detector 18 is provided associated with each transformer 16 to detect fault currents arising at least in the high voltage feeds to the transformer. Such fault currents may arise for example fr ⁇ n a breakdown in the high voltage windings of the transformer.
• Additicrtally severe faults in the low voltage winding of the transformer and the low voltage cables may also produce sufficient fault current in the high voltage side to be detected by the unit 18.
• the unit 18 triggers the fault thrcwing switch 17 to close thereby ccnnecting the respec ⁇ tive -phase of the supply line to earth and enabling an earth fault current to flow.
• the ring main 10 is protected at the primary sub-station 11 by circuit breakers 19 provided in both arms of the main.
• the circuit breakers are capable when actuated of interrupting a fault current in the main and thereby isolate the main fr ⁇ n the electrical supply .
• the circuit breakers 19 are actuated in response to the detection of a ' fault current in the main by means of detectors 20.
• the equipment constituted by circuit breakers 19 and detectors 20 may comprise existing kinds of source circuit breaker arranged to trip disconnecting the mains in response to. fault currents.
• the detector 18 comprises simply current transformers provided on each of the high voltage input phases to the transformer 16. Time Limit Fuses provided in the detector 18operate in" response to currents flowing in the current transformers above a predetermined maximum for more than a predet- termined length of time. On operation of the fuses, a control signal is generated to operate the fault throwing switch 17.
• the protection afforded the transformers 16 by the above described arrangement has the effect of isolating the entire ring main 10 in response to a fault at any one of the transformers connected to the ring main.
• normally, manually operable isolation switches are provided at each-of the " sub-stations to enable the faulty euipment to be taken off line so that the ring main can then be re-energised to provide power to the other sub-stations.
• the circuit breaker provided at the area sub-station 11 is made to be of the auto-reclosing type, ie automatically re-closing to re-energise the.supply after a predetermined delay.
• the sub-station illustrated generally at 15 is ' an example of a modified form which automatically isolates a faulty transformer from the line.
• a sectionalising switch 21 is additionally provided in series between the connection to the ring main 10 and the point 22 to which the fault throwing switch 17 is connected.
• the sectionalising switch 21 is operated by a control unit 23 -arranged to open the sectionalising switch 21 only after the cessation of the earth fault current caused by the fault throwing switch 17.
• the control unit 23 is arranged then to open the sectional ⁇ ising switch 21 during the dead time when the ring main 10 is isolated by the circuit breaker at the primary sub-station and before the circuit breaker recloses automatically. In this way on re-closing, the faulted equipment has been isolated from the line so that the remaining sub-stations can be re-energised.
• the above described fault detectors 18 at each sub-station sense only fault currents in the high voltage lines to the transformer. Some faults in the low voltage side of the transformer may not produce sufficient fault current on the high voltage side to actuate the fault throwing switch. Accordingly, in an alternative arrangement, the detector 18 is arranged also to monitor the low voltage side of the transformer directly, eg by further current transformers sensing currents on the low voltage lines to the transformer, including the low voltage neutral line. In this way protection can be provided to the transformer ensuring detection of transformer faults and thereby actuating the fault throwing switch to signal the fault to the primary sub-station.
• the fault throwing switch takes the form of a vacuum switch 30 which is held open and provided in the housing of a T shaped connector 31.
• T connectors are known and useful for making multiple spur connections to a line and for connecting the line to plant bushings such as the. bushing 32 of " a transformer.
• the housing 31 can be provided with a through connection between the ports 33 and 34 of the connector so that the connector can be interposed between the transformer bushing 32 f ⁇ nd two further ordinary T connectors 35 and 36 by which the high voltage line cables are directly connected to the transformer.
• the vacuum switch 30 has one contact solidly connected to the through connection line between ports ' 33 and 34. The other contact of the switch is solidly connected via the third port of the housing to earth as at 37.
• FIG. 3 An additional element 40 is illustrated interposed between the housing 31 containing the fault throwing switch 30 and the first of the T connectors 35 connecting the supply line cable to the transformer.
• the element 40 incorporates a further vacuum switch 41 to operate as the sectional ⁇ ising switch 21 of Figure 1.
• T connectors 35 and 36 together with the housing 31 are shown separated for convenience only. Furthermore, it will be appreciated that the two high voltage cables connected to* the single bushing 32 of the transformer by means of T connectors 35 and 36 constitute the incoming and outgoing elements of one phase of the ring main 10.
• FIG. 4 to 8 illustrate the T-shaped connector housing 31 with the vacuum contactor 30 providing the fault throwing switch in greater detail.
• the T connector has an outer covering 50 typically formed of an electrically semi-ccnducting rubber or plastics material. All current transmitting elements within the connector are insulated from the housing 50.
• Opposed ports 51 and 52 of the T connector enable through connection to be made eg between the connecting bushing 32 ofthe transformer connected in port 51 and an interconnecting bushing connected in port 52 to connect the T to an adjacent T connector 35.
• the through connection is provided via a through connecting element 53 centrally located between the ports 51 and 52.
• Each of the ports 51 and ' 52 is formed as a female receptacle shaped to receive the frusto-conical bushing of the male portion of a standard high voltage interconnection.
• the vacuum switch 54 is mounted within the upright ' of the T.
• the switch 54 has a fixed contact 55 at one end and a moving contact 56 at the other end 26.
• the fixed contact 55 is connected by means of a metal component 57 to the through connecting element 53.
• the moving contact 56 takes the form of a plunger extending through a gas seal in the body of the switch 54.
• the plunger 56 is held pulled out of the body in the position shown in Figure 5.
• Atmospheric pressure urges the plunger 56 into the body towards the closing position of the switch and further a compression spring 58 is compressed between a thrust washer 59 forming part of the plunger and a seat 60 to enhance the closing force applied to the plunger.
• ⁇ e plunger 56 with an extension shaft 27 and compression spring 58 extends through a metal tubular element 61 which is firmly attached to the lower end 26 of the switch body by fixing screws 28.
• the shaft 27 is a sliding fit in a bore 62 through a disc element 29 which is secured in the tube 61.
• the disc element 29, best seen in Figure 7, has radial bores containing compression springs 80 urging restraining balls 63 radially inwards to seat in a circumferential groove 81 around the shaft 27.
• Adjustment screws 82 are provided in the radial bores permitting adjustment of the force with which the balls 63 are urged into the groove 81.
• the plunger 56 is thereby restrained against the closing force provided by atmospheric pressure and the compression spring 58 to hold the switch open. However the screws 82 are set so that the retaining effect of the balls 63 can be defeated by applying excess closing -effort to the shaft over and above that exerted by atmospheric pressure and the compression spring 58.
• a chemical actuator 64 is mounted co-axially with the shaft 27 to be fired by a trigger signal supplied on lines 65 to apply the required excess force to the end of the shaft 27 to defeat the restraining balls 63 and thereby permit the shaft and plunger to move rapidly to the closed position, thereby closing the switch.
• Three metal wire braid connectors 83 are electrically connected by connecting screws 84 to the thrust washer 59 of the plunger, and are fed down through the tube 61 through holes 85 in the disc element 29, and out of the end cap 86 of the tube through holes 87.
• the braid connectors 83 are connected to earth outside the housing 50.
• the lines 65 to the chemical actuator extend out through the bottom end of the upright of the T housing along with the braid connectors 83.
• the lines 65 are connected to fault detection circuitry associated with the current transformers sensing the current in the high voltage supply to the transformer.
• annular layer 71 of insulation material insulating the current carrying elements within the housing from the outer semi-conducting wall of the housing.
• the cavities at the lower end of the upright of the housing from which extend the earthingconductor braids 83 and the lines 65 are also 5 completely filled with an insulating sealing compound.
• Screens 72 and 73 of semi-conducting material may be provided immediately adjacent the high voltage conducting elements of the unit to smooth out electric field concentrations which might otherwise impair the
• the screens 72 and 73 may be made from a conducting rubber material.
• the entire fault throwing switch unit illustrated, in Figures 4 to 8 is very c ⁇ ipact and can be made relatively cheaply. It provides a reliable open circuit via the
• circuit breaker may be made using an in-line two port housing shape with the ports in opposite ends of the housing enabling connections to be made to respective contacts of a vacuum switch.
• FIG. 9 illustrates an "in-line" form of
• a vacuum switch 90 is located axially inside a cylindrical covering 91.
• the covering 91 is formed of an electrically conducting plastics material providing an outer screen to the switch assembly.
• the vacuum switch 90 comprises* in - 20 the normal way a ceramic tubular body 92 with axially
• Contact 93 is mounted fixed relative to one end face of the vacuum switch 90 and is solidly connected, eg by welding, to a connecting member 95 in which there is an axial screw threaded bore 96.
• the vacuum switch 90 together with connecting member 95 are located within the covering 91 by means of solid encapsulation material 97.
• the encapsulation material 97 is electrically insulating and serves to insulate all the current carrying and conductive elements located within the covering 91 from the covering itself.
• the insulating material 97 is formed adjacent an open end 98 of the cylindrical cover 91 to form a frusto-conical inwardly tapered receptacle 99.
• the receptacle 99 is shaped to form the female receptacle portion of a high voltage connection of the type herein- before defined.
• the receptacle 99 is sized to receive the frusto-conically shaped bushing 100 of the male portion of such a connection.
• a screw threaded conducting stud 101 extending from the head of the bushing 100 locates and screws in to the bore 96 in the connecting member 95 at the base of the receptacle 99.
• the bushing 100 of the male portion is made of an insulating epoxy resin and is relatively hard, whereas the solid encapsulation material 97 comprises an insulating elastomeric material. Accordingly, the complementarily shaped frusto-conical surfaces of the bushing 100 -and the receptacle 99 make an interference fit w,ith each other when the stud 101 is received in the bore 96, to make a secure moisture seal.
• the second contact -94 of the vacuum switch 90 is formed as a plunger i ⁇ 2 extending from the other end of the .vacuum switch through a gas seal formed by a bellows 103.
• the plunger 102 extendsaxially along a cylindrical bore provided in a conducting rod member 104 extending coaxially from the end of the vacuum switch.
• the rod member 104 extends outwards through the opposite end opening of the cylindrical covering 91 and is terminated in a screw threaded connecting stud 105.
• the rod 104 has moulded around it a frusto-conical outwardly tapering bushing 106, so that the combination of the bushing 106 and connecting stud 105 themselves form the male portion of a high voltage connection of the kind hereinbefore defined.
• the bushing 106 is formed of an epoxy resin insulating material similar to that normally used for connection bushings such as bushing 100. Electrical connection is made between the rod 104 and the plunger 102 of the movable contact 94 by means of a Multilam contact 107.
• the Multilam contact 107 is formed of a pack of washer like elements solidly located within the bore of the rod 104 and providing a sliding fit with the plunger 102. The multiplicity of contacts provided by this arrangement ensure low resistance contact at all times.
• the operating mechanism ' for the vacuum switch 90 is generally located within the bore in the rod 104.
• a compression spring 108 seated against a base recess of the bore in the rod 104 bears against an hydraulic piston 109 mounted on the plunger 102, tending to urge the plunger to close the contacts 93 and 94.
• the piston 109 can travel axially in a cylinder portion 110 of the bore in the rod 104 between a first position in which the contacts 93 and 94 are closed and a second position in which the contacts are open, as shown in the drawing.
• An hydraulic packing seal enables the plunger 102 to move relative to the end face of the cylinder 110 whilst preventing leakage of hydraulic fluid in the cylinder.
• Hydraulic fluid to actuate the piston 109 in the cylinder ' , to move the plunger and contact 94 from the closed to the open position as shown in the drawing, is supplied along a pipe 112 from a pneumatic/hydraulic interface unit 113 mounted on the outside of the covering 91.
• the plunger 102 is retained in the open position as shown, on actuation of the piston 109 by a pulse of hydraulic fluid along the pipe 112, by means of an hydraulically released latch 114.
• the latch 114 is urged by a compression spring 115 radially inwards relative to the plunger 102 so as to locate into a suitable gr.oove or recess provided in the plunger 102 when the contacts of the vacuum switch are opened as shown. - ⁇ he latch 114 then prevents the contacts from being closed again under the influence of the compression spring 108, even if the hydraulic , pressure applied to the piston 109 is no longer maintained.
• the latch 114 is itself-released by means of a hydraulic piston and cylinder arrangement illustrated at 115, whereby hydraulic fluid is delivered to the cylinder along a pipe 116 from another pneumatic/hydraulic interface unit 117 also mounted on the outside of the cover 91. Delivery of a charge of hydraulic fluid along the conduit 116, depresses the piston of the latch 114 against the compression spring, withdrawing the latch from the groove or recess in the plunger 102 so that the plunger 102 can then be moved under the influence of the compression spring 108 to close the contacts. Delivery of a charge of hydraulic pressure along the conduit 112 can reopen the switch, with the latch 114 again locating in the recess in the plunger under the influence of the compression spring in the arrangement 115.
• the chargesof the hydraulic"izid delivered to open or close the vacuum switch 90 come from the pneumatic /hydraulic interface units 113 and 117 as mentioned before. Each of these comprises a movable member able to communicate pneumatic pressure to the hydraulic fluid whilst sealing one from the other.
• the interface units are -shown in the drawing as pistons moving in cylinders, but may alternatively be formed by means of flexible diaphrams.
• a 'charge of pneumatic pressure can be delivered to each of the interface units from respective pressure boxes 118 and 119.
• the pressure boxes 118 and 119, the interface units 113 and 117, and the inter ⁇ connecting conduits are normally at substantially atmospheric pressure, with the vacuum switch remaining in its previous state.
• Pneumatic pressure to operate the switch to change its state is produced by detonating a small explosive charge in the respective one of the pressure boxes 118 and 119. Explosive charges are shown mounted in each of the pressure boxes at 120 and 121 respectively. These can be detonated electrically from respective selectors 122 and 123. Detonation of a charge in one of the pressure boxes 118 produces a pneumatic pressure pulse along the conduit to the respective pneumatic/hydraulic interface unit 113 and 117, which in turn produces the necessary hydraulic fluid charge to operate the respective opening or closing mechanism of the switch.
• the entire switching device may be mounted by means of the female receptacle 99 on the existing connecting bushing, eg of a distribution transformer. Additional connections to the transformer can then be made by means of the bushing 106 of the switching device.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Gas-Insulated Switchgears (AREA)

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• 1985
  • 1985-06-20 EP EP19850903030 patent/EP0186688A1/de not_active Withdrawn
  • 1985-06-20 WO PCT/GB1985/000274 patent/WO1986000464A1/en not_active Application Discontinuation
  • 1985-06-20 AU AU44400/85A patent/AU4440085A/en not_active Abandoned

Non-Patent Citations (1)

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