NO844963L - LAST SWITCH - Google Patents

Description

The invention relates to an in-ground, closed load switch especially designed for use in electricity distribution systems with medium voltage in the range from 1 to 36 kV to interrupt currents up to approximately 1 kA.

Load switches used in distribution circuits with medium voltage generally comprise a pair of electrodes, one of which is stationary and the other can be moved to open and close the circuit. As is usually used in three-phase systems, three or multiples of three switches are mounted in a common earthed metal container. The switches are generally available in four types. Air breakers were first developed. Such switches are based on

air for insulation. As air is a relatively poor insulator, relatively large clearances must be maintained around each switch to isolate it from ground potential. Furthermore, the switch's contacts must be able to be separated with a relatively large clearance to break and isolate the circuit when the switch is open. These switches are consequently very large and must be equipped with very large containers. Therefore, air circuit breakers are often impractical in medium voltage distribution systems due to the high manufacturing costs, the large space they require and the unattractive appearance due to their large moving mass.

Oil-insulated circuit breakers represent a significant improvement in size over air circuit breakers. Oil is both a more effective insulating and spark suppressing medium. This makes it possible for an oil-insulated switch to be enclosed

in a relatively compact grounded house. Thus, oil-insulated circuit breakers take up significantly less space than equivalent air circuit breakers for use in the same voltage and amperage range. However, oil is flammable and thus poses a fire hazard. Another disadvantage of an oil-insulated switch is that the gases developed by the spark that occurs in the oil produce high pressures, which pose a risk of explosion and the accumulation of gases requires special measures, for example venting. A further disadvantage is the risk of water contamination of the oil, which can drastically reduce the dielectric value of the oil.

An oil circuit breaker for use in a medium voltage distribution system typically consists of a metal housing that is grounded and filled with oil. In the typical structure for three phases, a single metal housing comprises at least three switches, one for each phase, or multiples of three such switches, immersed in the oil.

Another type of load switch uses vacuum switches. With these switches, the contacts are enclosed in an evacuated chamber. The vacuum itself quickly absorbs the gas products from the spark that is drawn between the switch's contacts to interrupt the current when the switch is opened. Usually three or more such vacuum switches are mounted in a grounded metal container. The container contains an insulating medium that surrounds each vacuum switch. The insulating medium can be air, oil or sulfur hexafluoride.

The disadvantages and limitations of vacuum switches include the following: 1. Accidental breaks in the open position due to irregularities in the surfaces of the contacts require an additional disconnection device which is activated after the current has been interrupted.

2. It is very difficult to monitor correct vacuum conditions

_3

with 1.3 x 10 Pa.

3. A floating ring with contact potentials in the switch excludes practical activation of the vacuum container at ground potential. 4. High frequency characteristics of the vacuum switch can cause overvoltages. 5. The vacuum switch presents special problems when capacitive or inductive loads are involved. 6. There are large statistical variations for the electrical and insulating characteristics in vacuum.

Another type of load switches for distribution systems are gas-insulated switches that use a gas for both insulation and interruption. Sulfur hexafluoride (SF^), is used either alone or mixed with other gases, for example nitrogen. Such switches can be of the type with gas blowing or gas puffs where the spark suppressing gas is caused to flow over the contacts when the spark is formed. The relatively large flow rate of compressed gas over the spark will quickly extinguish the spark at one of the alternating current's natural current zero points. In a typical three-phase construction, a grounded metal receptacle surrounds three, or multiples of three, switches. Each individual switch typically comprises an unsealed cylindrical housing made of plastic, for example a reinforced epoxy resin. A grounded metal housing filled with sulfur hexafluoride surrounds the switches with significant clearance to prevent spark transfer. The sulfur hexafluoride in the common container and in the individual breakers is generally maintained at approximately atmospheric pressure with multiple breaker distribution breakers. A higher pressure in the housing is not practical because the usual gaskets and movable seals are exposed to leakage and because the large mechanical loads that occur in the relatively large common housing require a massive protective container. Consequently, only a pressure is used that is large enough to prevent a vacuum condition at low temperatures, i.e. 1.2 - 1.4 atm at 15.6°C which is sufficient to achieve positive pressure at a minimum temperature of r 40°C.

The disadvantage of each of the switches described above is that they are very heavy and bulky. Thus, they require special foundations and large rooms and containers in which they are mounted, resulting in high installation costs, unattractive appearance and requiring large critical space. The size of these switches is particularly undesirable in cities and built-up areas.

Another problem with these types of switches is abrasion and mechanical wear of the contact. Movable and stationary contacts can be compact conductors that abut each other to close the electrical circuit. This contact design ■ has the disadvantage that the contacts spring and a large impact load when the switch is closed, as well as a large contact resistance when by-products from sparking or corroded material are clamped together between the contacts. To prevent these problems, a wiping contact design can be used. In some constructions, one of the contacts has a hollow cylindrical design while the other is a compact cylinder that fits into the interior of the other contact's hollow cylindrical portion. The hollow cylindrical part can have a compact wall design or can consist of several fingers, as described for example in US 3970811. The activation of circuit breakers results in the surface of the contacts sliding in relation to each other. This can result in a reduction of the electrician due to the particles that wear off from the contacts. This further reduces the effective life of the contacts and requires expensive maintenance for repair.

Another problem with cylindrical finger contacts is the difficulty in maintaining correct axial runout for the contact engagement when the switch is closed.

A further problem with gas-filled switches is that the pressure in the container can drop to an unsafe level where the spark that occurs when the switch is opened is not extinguished, resulting in rapid heating and vaporization of the contact and, in some cases, an explosion.

A pressure gauge can be fitted, but this does not prevent opening of the switch and it constitutes a further source of leakage.

A further problem with sealed switches is that malfunctioning of the switch can cause uncontrolled sparking, heating and consequently vaporization of the metallic contacts. This increases the internal pressure in the switch and creates a safety risk for a possible explosion of the switch.

A further problem with distribution switches is the need for an appropriate device to determine each conductor's line voltage and the position of the switch contacts. Direct measurement of the high voltage levels that occur is cumbersome and fraught with risk and the positions of closed contacts are not secure when the contacts are either both energized or not energized. For practical reasons, this monitoring should be possible in places at a distance from the switch.

A further problem with distribution switches is the need for remote control of the contacts. This need is described, for example, in US 4187437. The costs for remote control of known switches are high due to the large amount of energy required to activate conventional switches.

In the distribution system for medium voltages

is another device that can be used to interrupt the current, the so-called "load breaker" elbow connection. Such on-load switch elbows have advantages, among other things, in their small size, their ability to be directly connected to a sleeve and/or cable and their submergibility, which makes it suitable for use both in places above ground and in underground spaces. However, it has significant limitations and accompanying

difficulties:

1. Load interruption is limited to 200 A and less.

2. With the load-breaking elbow, there is a significant danger for the staff as the disconnection takes place directly in the atmosphere and there is no shielding or protection for the operator who must stand in front of the device. A spark can occur in open air, so there is a danger that the spark can jump to earth and thereby develop a significant false spark with extremely high voltage, which can be dangerous for anyone nearby and damage the equipment. 3. Correct disengagement depends on the operator's experience and strength when using an energized arm to dislodge the elbow from its connection. 4. The service life of an elbow coupling is limited to relatively few activations as erosion of the intervening parts, due to the generation of sparks, greatly reduces the device's effectiveness in interrupting the current". There are certain dangers associated with such deterioration. 5. Load breaking elbows are limited to single-phase operations and where they are used in a three-phase system there will necessarily be a relatively large time interval between the opening or closing of the individual phases. This can in some cases cause the phenomenon of ferroresonance with serious overvoltage consequences. In many places of earth only three-phase switches are accepted 6. The right-angle bend in the shape of the elbow eliminates a requirement for a full cable loop in the receptacle.

These cable loops in the distribution lines are very large and dominate the space in the container. 7. After a longer connection, an elbow coupling may adhere to an associated connection, which will require an unusually large force to disengage.

Consequently, the use of load-break elbows for load interruption or load transfer is often limited. These elbow connections are generally limited for activation on non-energized circuits and conventional switch devices, as described above, must first be activated to disconnect the voltage on the line before the elbow connection can be activated.

Since these conventional switches may be located at locations remote from the particular elbow joint, a time-consuming and cumbersome procedure must be followed before an elbow joint is allowed to be tripped. These procedures involve significant travel between locations that are far apart. The time and distances of perhaps several miles entail a risk of accidental errors or incorrect operations. Consequently, all these difficulties will greatly extend the time that a circuit must be disconnected before a safe connection can be made.

On the basis of these problems, there is a need for a load switch for medium voltage which is small and has little weight so that it can be used without special foundations and rooms, which also does not require cable loops, which uses an insulating medium without the risk of fire, has a long lifetime, is essentially maintenance-free, can easily be covered and can be easily disconnected.

The present invention relates to a switch which satisfies these requirements. The switch comprises a housing, first and second opposing conductors in the housing, where the conductors are preferably stationary, and a contact device between the conductors. The contact device can be moved between a first closed position with electrical contact to both conductors and a second open position with contact only with the other conductor. The term "closed" here describes a position where the switch closes the electrical circuit in which the switch is arranged, so that the circuit is able to conduct an electric current, while the expression "open" refers to a position where the switch opens the circuit in which it is arranged so that the circuit cannot transmit an electric current.

Preferably, the opposing conductors are mounted coaxially in a cylindrical housing.

The contact device comprises several electrically conductive rods arranged essentially at equal distances in a cylindrical shape around the conductors. The rods are always in sliding contact with the second conductor and in sliding contact with the first conductor only in the fully closed position. Resilient devices are available to apply an inwardly directed contact force on the bars against both conductors. This contact force has a first level when the contact device is in the closed position and a second level when the contact device is not in contact with the first conductor. The first level is larger than the second level. In this way, the switch is kept securely closed with good electrical contact between the bars and conductors in the switch's closed position. This ensures little heating in the closed position at the selected current strength ranges. In the event of a short-circuit current, the contact device produces significant magnetic forces against the contacts which cause them to "pop out", by the contacts being pushed apart by the magnetic pulsating forces which occur at extremely high current levels. However, when the switch is opened, the contact force is significantly reduced so that mechanical abrasion in the contact device and conductors is minimized. The greatly reduced contact force results in a corresponding reduction in the energy and mechanical forces required to move the contacts.

The suspension device can be leaf springs with opposite first and second ends, where the first ends press the rods against the first conductor and the other ends press the rods against the second conductor when the contact device is in the closed position. When the contact device is moved away from the first conductor so that the rods are no longer in contact with the first conductor, there will no longer be any force exerted against the first conductor and the force against the second conductor is greatly reduced.

Preferably, the switch has an earthed cylindrical housing and contains a pressurized insulating gas as well as hermetic devices for permanently sealing the housing. Preferably, the housing has a cylindrical side wall with a small diameter where the conductors are arranged coaxially at opposite ends. Such a switch, which has a diameter of less than 150 mm, can be used in a circuit from 1 to 36 kV for continuous transmission or breaking of currents up to 1 kA.

In order to achieve a hermetically sealed switch, an activation arm preferably extends through the side of the housing and has a bellows which is hermetically sealed to the arm and the housing, the arm being able to be moved between first and second positions as the bellows is bent by this rocking movement. The arm can be rotatably supported on an axis which is passed through the bellows to produce the bellows' tilting deflection. Articulating devices connect the arm to the contact device so that when the arm is moved between first and second positions, the contact device will be moved in a corresponding manner between closed and open positions. The tilting bellows practically produces a hermetically sealed, pressurized switch that requires no additional work to be done to pressurize the insulating gas when the actuating arm is actuated. Mounting the tilting bellows and actuation arm on the side of the housing allows the conductors to flow axially in a compact switch that can be plugged into a wire in an electrical circuit without requiring cable loops.

The energy required to activate the switch is greatly reduced by the combination of the short contact stroke and low contact forces which are sufficient due to the high pressure of the insulating gas which can be used in the small hermetically sealed housing and the bellows which does not compress the gas, as well as the cylindrical arrangement of contact bars that will not snap at moderate contact forces and the reduction of the contact force when the bars are in sliding contact only with the second conductor.

The switch may have an insulating liner that acts as a cylinder for a buffer piston for the contact device. The insulating lining can be arranged separately from the housing so that an annular space is formed between the lining and the housing. Preferably, sealing devices are arranged in this annulus to separate the cavity from the part of the housing containing the second conductor. Preferably, the volume of the part of the housing containing the first conductor, together with the volume of the annulus, is greater than the volume containing the second conductor arranged opposite the contact device. This reduces the return pressure at the buffer nozzle due to heating of the insulating gas by a spark. Preferably, this larger volume is achieved by the insulating sleeve arranged close to the housing in an area with a relatively weak electric field. There is thus no need to arrange a conventional partition in the cylinder to limit the volume of the insulating gas which is compressed by the piston.

The insulating lining can be equipped with insulating bands at each end to act as capacitive electrodes for monitoring the position of the contacts and the voltage present at the first and second conductors. Each conductive band acts as a capacitive voltage divider to allow local or remote low voltage measurements proportional to the voltages at the first and second conductors. When only one conductor has voltage, a further indication is given that the contacts are in the open position. When both conductors carry current or both do not carry current, the position of the switch contacts can be measured by connecting a high-frequency voltage source to one of the conductive bands and carrying out a frequency-separating voltage measurement of the other conductive band. The open position of the contacts is indicated by a reduced measured voltage at the other conductive band, caused by the small capacities formed by the open switch's contacts, whether the conductors carry current or not.

It has been demonstrated in this way that a single-phase load switch which is suitable for use at voltages up to 36 kV and currents up to 1 kA can be enclosed in an earthed container with a diameter of from 50 to 150 mm and which contains an insulating gas under a pressure of at least 147.1 kPa. This is in contrast to known technology where single-phase distribution switches are not closed individually in earthed containers, but several switches are closed in a common earthed container. It has also been unexpectedly found that this new closed single-phase switch has greatly simplified the operation compared to known switches of this type. In addition, the individually closed switch can be easily inserted into distribution systems as it can, for example, be attached to a transformer sleeve using an elbow coupling or it can be spliced directly into a cable in the system without having to create special rooms or separate containers to accommodate these switches.

It has also been unexpectedly found that, despite the switch's very small volume, no significant pressure rise (either temporary or permanent) occurs when the load currents are switched off.

In one aspect of this invention, a closed single-phase load switch for use in electrical circuits within the voltage range from 1 to 36 kV comprises: a. a tight cylindrical metal housing with a diameter in the range from 50 to 150 mm,

b. first and second sleeve devices that coaxially need

through the cylindrical metal housing, one of the sleeves being mounted at one outer end of the housing and the other being mounted at the other outer end of the housing and with an electrical conductor passed through both sleeves, c. a contact device that can take a first position where it has physical and electrical contact with each sleeve's electrical conductor and a second position where it is physically and electrically separated from at least one of the conductors, d. devices for causing the contact device to move from the first position to the second position and thereby separate the contact device from at least one of the conductors so as to interrupt the current through the switch, and from the second position to a first position to thereby bring the contact device into contact with each conductor so as to form a path for the current through the switch, and

e. an insulating gas in the housing which is maintained at a pressure of approximately 490 kPa, the switch being arranged to form an electrical connection between a load and a power source with a voltage in the range of 1 to 36 kV.

In another aspect of this invention, a device comprises: A. a single-phase, grounded and closed load switch for use in electrical circuits in the voltage range 1 to 36 kV, comprising: a. a tight cylindrical metal housing with a diameter in the range 50 to 150 mm,

b. first and second sleeves that coaxially penetrate the cylindrical metal housing, one of the sleeves being mounted at

the outer one end of the housing and the other is mounted at the outer other end of the housing, an electrical conductor being passed through each sleeve, c. a contact device arranged to occupy a first position where it is in physical and electrical contact with the electrical conductor of each sleeve, and a second position where it is physically and electrically separated from at least one of the conductors,

d. the device for bringing the contact device to move from the first position to the second position to thereby separate the contact device from at least one of the conductors and thus interrupt the current through the switch, and from the second position to the first position to thereby bring the contact device in contact with both leaders to thus form one

current path through the switch,

e. an insulating gas in the housing which is maintained at a pressure of between 98 and 490 kPa,

B. a transformer with a voltage tap in the range 1 to 36 kV, the transformer having a tap sleeve, and C. a separable elbow coupling comprising a molded elastic body with first and second sleeve spaces adapted to receive and electrically connect the sleeves in the electrical equipment, the first sleeve opening is connected to a sleeve in the switch and the second sleeve opening is connected to an outlet sleeve on the transformer.

These and other features and advantages of the present invention will become better apparent from the following description in connection with the drawings, where Figure 1 shows a side view of a switch according to the invention, with a contact device and an actuator, Figure 2 shows a detailed longitudinal section of the contact device in the switch in Figure 1, Figure 3 shows a cross-section of the switch in Figure 1 along 3-3 in Figure 2, Figure 4 shows a cross-section of the switch in Figure 1 along 4-4 in Figure 2, Figure 5 shows a longitudinal section of the switch's actuator on figure 1, the actuator comprising a waterproof cover, figure 6 shows a cross-section of the switch in figure 1, along 6-6 in figure 5, figure 7 shows a longitudinal section of another embodiment of the switch according to the present invention, figure 8 shows the connection at a three-phase system with three single-phase switches corresponding to Figure 7, connected to the sleeves of a transformer with elbow connections, and Figure 9 shows an arrangement of three switches according to Figure 7 in a single-phase loop design which r each switch is activated independently of the others.

The switch according to the invention is arranged in an earthed container consisting of a metal housing with an essentially cylindrical shape. The term "essentially cylindrical" is used here in the sense that the housing has an essentially cylindrical, but not necessarily circular, cross-section.

Although this is not preferred, oval and similar cross-sections can be used if desired. The house can be earthed by connecting to earth via a suitable conductor. The housing is hermetically sealed and thus gas-tight and can thus be safely immersed in water. This makes the switch suitable for use underground where a flood is possible, or in environments that cannot be combined with air insulation. In this description, a hermetic seal denotes a gas-tight seal that can limit the total leakage from a pressurized container to the atmosphere to less than 10 - 6 cm 3 /s measured at atmospheric pressure.

The switch according to the present invention contains in the housing an insulating gas which is kept under positive pressure, i.e. greater than 98 kPa. The gas is preferably sulfur hexafluoride (hereinafter referred to as SFg). The gas pressure used in a specific switch depends on the voltage and amperage range of the switch, its size and whether there is a buffer mechanism or whether another locking device is used for the gas. The gas pressure is in range 98 to 490 kPa and preferably between 147 and 490 kPa for circuit breakers in the range 15 - 36 kV which are insulated with SFg. The hermetically sealed housing allowed pressure in this range to be maintained for periods exceeding 20 years.

A pair of sleeves are fitted in the housing. Each sleeve comprises a metal conductor arranged in and which extends through an insulator, for example made of epoxy plastic, or a ceramic material. A metal mounting flange is molded into the plastic and welded to the wall of the switch's grounded receptacle. The metal conductor in the sleeve extends through the sleeve to conduct current to the switch. The conductor can be a rod of suitable metal, generally copper or aluminium. If aluminum is used, the aluminum extension is preferably enclosed where the contacts come into contact, in a metal that is better suited for sparks or sliding contacts.

Preferably, sleeves are arranged coaxially at the ends of the essentially cylindrical housing, the conductors of the sleeves extending axially through the ends of the housing. This allows a design in the wiring of the circuit that does not require loops of the cables and allows a housing with a small diameter suitable for high pressures to be used.

The interruption of high-voltage circuits requires the removal of significant amounts of heat from the switch. Heat is primarily conducted away by heat conduction from the switch's contacts through the conductors of the external power cable. Secondarily, heat is conducted from the conductors through the sleeves to the housing. That is why

it is important that the leaders are short. The inner length of the conductor, i.e.

the part of the conductor that extends into the body of the switch depends primarily on the type used for contact. The conductors must be sufficiently long to make physical and electrical contact with the contact device when it is in its first, or closed, position and must accommodate the movement of the contact device in its second, or fully open, position. The additional length of the conductor in the parts of the sleeves in the interior of the housing depends on the distance to the surface that is required along the sleeve's insulating material to prevent sparking to the housing.

Because the insulating gas in the housing can be kept under high pressure, both a short contact stroke and a short inner sleeve can be used.

The contact device can assume a first position where it has Russian and electrical contact with each sleeve's conductor. In this first closed position, the contacts in the device must be able to carry continuous current. At the starting point, the switch is capable of conducting continuous current up to at least 200 A in the lowest range and at least 1000 A (or 1 kA) and possibly higher. The contact device can also take a second position where it is separated from a first conductor in one of the sleeves to form a gas-insulated clearance in the path of the circuit and thereby interrupt the current through the switch. The switch can open at normal current load and close at large fault currents of, for example, 12,000 A, 25,000 A or even higher according to standard short-circuit values.

The contact device is generally moved in an axial direction. When it is moved into or out of contact with the first conductor, a spark is formed between the contact device and the conductor. As described in more detail below, the spark is smothered by the pressurized insulating gas.

Preferably, the contact device comprises several elongated, electrically conductive contact rods arranged as a hollow cylinder. The contact bars are preferably made of a highly conductive material, for example copper. The contact rods are held in a cylindrical shape by being mounted in a holding device with a radial groove for each rod. The holding device can be an axially sliding piston which is used to pump the insulating gas as described below, where the piston is made of an insulating material, for example molded plastic. The radial grooves hold the contact rods in a cylindrical shape, separated from each other and notches in the contact rods engage with the grooves for axial positioning of the contact rods by the piston. The grooves in the holding device can be achieved by appropriately designed discs, as shown in figures 2, 3 and 4 and described in more detail in the following.

The contact device preferably has a guide to keep the contact device in correct axial alignment with the other components. This guide can be a cylinder for the piston.

The piston preferably has a relatively open star shape to allow the insulating medium to circulate in the housing. The housing may contain a pressure device, for example in a gas-insulated switch device, to push a stream of spark-suppressing gas across the clearance formed between the first conductor and the contact device when the circuit is opened or closed. A pressure device can suitably be built into the construction of the piston, if this is desired. The piston comprises a relatively compact cylindrical block with several holes or passages carried through. When the contact device is moved from its first to its second position, the insulating gas is forced through the holes and directed towards the clearance formed between the first electrode and the contact device. In such embodiments of the invention, the conductive rods in the contact device can be guided on the flush devices in such a way that the surfaces of the rods which are in contact with the first electrode are placed relatively close to the holes through the flush device.

The contact device comprises a spring which is connected to the contact bars in such a way that when the device is in its first position, i.e. in contact with both conductors, the contact rods exert a maximum inwardly directed contact force against the conductors. This ensures low contact resistance and high heat transfer across the closed contacts. The springs can, for example, be leaf springs mounted on each conducting rod. Other springs, for example spiral springs or band springs around the conducting rods, single radial springs mounted on each rod, or other devices that provide an inwardly directed force against the rods, can be used.

To open the switch, the contact device is moved from the first to the second position, i.e. that the piston is moved so that the contact rods no longer have contact with both conductors. The device can be moved by means of a joint arrangement connected to the piston, which is activated by a handle or an actuator arranged outside the housing. As described in more detail below in connection with the drawings, opening the switch, i.e. moving the switch to its second position causes the contact bars to move away from the first electrode. A spark between the front ends of the contact rods is extinguished by the insulating gas.

The inwardly directed force acting against the contact rods causes the rods to be pressed inwards against a spacer as soon as the contact rods are no longer in contact with the first conductor. The spring is connected to the contact rods in such a way that when the contact rods are pressed inward against the spacer after they are released from the first conductor, the force acting on the opposite ends of the contact rods against the second conductor is significantly reduced. A contact force of approximately 1 to 2 kg when the cylindrically arranged contact rods make contact with both conductors. When the contact rods are disconnected from the first conductor, the contact force against the second conductor is reduced to approximately 0.5 kg. The contact bars remain in contact with the second conductor so that the current arising due to the spark between the front ends of the bars and the first conductor is transferred to the second conductor. The contact device is pulled away from the first conductor a sufficiently large distance so that a clearance is formed so that the spark between the first conductor and the contact bars does not re-emerge after it has been suffocated. There is a reduced force against the rods and the second conductor.

It has generally been found that when the contact device is used in a load switch in a circuit with 200 A and 15 kV, the piston can have a relatively open "star" shape. When used in a circuit with 600 A and 15 kV, a pressure mechanism is preferred.

In order for the pressure mechanism to be effective, the flow of insulating gas must continue after the contacts are separated by a distance sufficient to prevent the re-emergence of the spark, until a subsequent oppositely directed flow occurs. Since synchronizing the contact opening with the frequency of the wire is not practical, the choke gas flow must continue for at least half a cycle to ensure that the choke current continues after the contacts are separated beyond the respark distance. Because it is also desired to minimize the heat generated by the spark, the suffocation should be completed within a short time interval. The switch according to the present invention can be activated with a short contact stroke with a correspondingly small contact speed within a time frame determined by the considerations above. As the low contact speed greatly reduces the kinetic energy required to activate the switch, a build-up of the moving parts with little weight is possible, so that an actuator with very little power can be used.

By making all components apart from the contact device of a suitable insulating material, it is possible to produce a closed compact switch that is grounded where the grounded container has a diameter of less than 150 mm.

A piston in a cylinder can drive the contact device according to the invention, in which a pressure or gas blowing mechanism is arranged. A pressure mechanism delivers a stream of insulating gas to the area where the arm is formed "to blow out" the spark. In such designs, the body of the piston is relatively compact and has suitably placed holes which extend through the piston to direct a stream of insulating gas to the clearance between the contacts so as to suffocate the spark produced when the contact device is moved.

A pressure mechanism used in an embodiment according to the invention is shown in Figure 7 and described in detail in the following.

It is preferred that a compact tube-shaped body or lining of a suitable insulating material or medium is inserted between the contact device and the housing near the sparking zone. The tubular body is preferably placed close to the wall of the house and can be attached to this if desired. If the tubular body is attached to the metal wall, there should be no air space between the two components. It is preferred to place the tubular body so that there is an annular clearance between the body and the wall. If desired, the tubular body can extend over the entire length of the house. The thickness of the insulating material depends to a certain extent on the voltage that will be across the switch. In general, the tubular body should have a thickness between 2.5 and 13 mm. The tubular body is preferably an alkyl, epoxy or equivalent plastic. The tubular body may serve as a cylinder to guide the piston of the contact device.

The switch can be equipped with electrodes for capacitive determination at a relatively low voltage, at high voltage, at connected switch conductors and the open and closed positions of the contacts. This is possible with the tubular insulating lining which is arranged coaxially in the housing and separated from it by a smaller clearance or ring-shaped space for capacitive separation of the voltages of the conductors during alternating current. The insulating liner may have conductive strips arranged in contact with the annular space, axially arranged near each coaxial contact. The conductive bands can be connected with hermetically sealed connections on the housing. Voltage measurements of the connections can be carried out locally or by remote reading, as the measurements correspond to the contact voltages when the switch is connected to a distribution system.

If, for example, the housing has a diameter of approximately 76 mm, the conductive bands are approximately 74 mm and the contacts approximately 13 mm in diameter and a voltage of approximately 225 V is connected to the corresponding conductive band. If there is a large voltage at one of the contacts, this can be determined by conventional equipment connected with associated connections. If the voltage measured at the connections indicates that one contact is connected while the other is not, there is a further indication that the contact device is in the open position.

If the contact of these measurements turns out to be in the same position (both under voltage or both without voltage) a power source with a high frequency current can be connected to one of the connections to determine the position of the contact device. The high-frequency magnetization of a conductive band is connected to an associated conductor, via the contact device of the other conductor, then to the other conductive band where it can be measured with a conventional frequency-selecting voltmeter. When the contacts are in the closed position, the transfer of magnetism from one conductor to the other is direct.

However, when the contacts are in the open position, the resulting very low series capacitance between the conductors will prevent a significant high-frequency magnetization from being transferred to the other conductor and thus to the other conductive strip. The degree of high-frequency coupling can be measured under controlled operating conditions to calibrate the measurements. These measurements are appropriate for the switch according to the present invention as the capacity between the contacts is relatively small in relation to the capacity between the conductive bands and the relevant contacts.

The switch has means for moving the contact device from the first position to the second position. A preferred arrangement comprises a tiltable bellows or a diaphragm mechanism arranged on the side wall towards one end of the housing. Actuation of a rocker arm or an arm extending through the bellows results in movement of the contact device from its first to its second position and back, as desired. Activation of the arm deflects the bellows by lateral and/or rotary movement in a direction substantially normal to the expansion axis of the bellows. This type of bending of the bellows is referred to here as "tilting".

The use of the bellows with tilting bend in the high-voltage switch according to the invention provides several advantages. The tilting bellows can be activated without significantly changing the closed volume of the bellows when the contact device is moved from its first position to its second position. This eliminates the work that would otherwise have been done by compressing the insulating gas by conventional axial movement of the bellows. The bellows makes it possible for it to be placed outside the central axis of the wire and thus allows an unaffected linear orientation of the conductors. Such a linear orientation of the conductors, which is made possible by the use of the tiltable bellows in the manner described above, allows the switch to be easily installed, as described below. Furthermore, the linear orientation of the current path in the switch device advantageously affects the magnitude and direction of magnetic forces that occur in the event of a short circuit. The metal cover produces favorable shielding which seeks to reduce the magnetic forces due to external current loops in short-circuit conditions.

The use of a tilting bellows extends the life of the switch as there are no paths for a gas leak as would have been the case if sliding seals or O-rings had been used.

The use of the tilting bellows reduced the size and cost of the bellows, i.e. the number of pleats required in the bellows and also the lifetime of the bellows is extended due to the fact that its speed of movement is reduced, as only the relatively small speeds near the pivot point are applied to the bellows and not the high contact speed. Since the loads in the bellows are directly dependent on the rate at which it is activated at high speeds, this invention reduces the stresses and increases the life and reliability of the device.

The compact size and light weight of the switch according to the invention enables easy insertion into a distribution network. The switch can be connected directly in a power cable, for example with a conventional joint or with conventional separable connections or couplings. Such separable connections and couplings are typically molded elastic materials arranged to receive, for example, a power cable and sleeve to form an electrical connection between them. How relatively easily the switch can be inserted into the distribution network is shown by the fact that the switch can be attached directly to a transformer by means of an elbow connection. Elbow couplings are a common commodity and an example of such an elbow coupling is described in U.S. Pat. 3559141.

Figures 1-5 show a preferred embodiment of a switch (205) according to the present invention. The switch

(205) comprises a cylindrical metal housing (210) which is grounded. A supply sleeve (212) and a load sleeve (214) are fitted to opposite ends of the housing. The sleeves (212) and (214) both have a ring

(215) which is cast in place. The rings (215) are welded to the housing

(210) to form a hermetic seal between the supply sleeve

(212),, the load sleeve (214 ) and the housing (210). A rod (216) for the supply of current extends through the supply sleeve (212)' and a rod (218) for the load current extends through the load sleeve (214).. The current rods (216) and (218) each have a threaded hole (211) for receiving a connector (not shown) or for use as a soldering cup for connection with a power cable

(217)belonging to an external distribution network.

Figures 2, 3 and 4 show a contact device (219) which is axially slidably mounted in the housing (210). The contact device (219) comprises several cylindrically arranged contact rods

(220) which is mounted concentrically in a piston (222) '. When the piston (222) is in a closed position (a), a first end (221) of the contact rods (220) will rest against a spark contact

(226) which is attached to the bar (218) for load current. The contact rods (220) are disconnected from the spark contact (226) when the piston is in an open position (b). In the drawing, the parts are shown in the closed position with solid lines, while the open position is shown dotted. A second end (227) of the contact rods (220) is constantly sliding against a transfer contact (224)' which is attached to the rod (216) for supply current in a bore (228) in the transfer sleeve (212). The bore (228) allows the combination of the connector (224) and the supply sleeve (212) in the housing (210) to be shortened to achieve improved heat conduction while maintaining a sufficiently large surface distance above the supply sleeve (212) to prevent sparking from transfer contact (224) to ground. The piston (222) has several through-going axial holes (230) to accommodate the flow of insulating gas that occurs due to the displacement of the gas when the piston (222) is moved between first and second positions. A piston cup (231) is attached to the outside of the piston (222) and holds a nozzle (232) which surrounds the spark contact (226) when the piston is in the first position. The piston cup (231) has several axial holes (231) which are all closed with a non-return valve (234) to control the gas flow as described below. The check valve

(234) is held by a valve stand 235).

A shield (238) is provided on the rod (218) for the load current and is held in place by a retaining ring (240). The shield (238) is concave towards the spark contact (226) to protect the load sleeve (214) from sparking.

An insulated liner (242) surrounding the contact device (219) is radially centered in the housing (210) with an 0-ring (244) at the supply sleeve (212) end to create an annulus (245) between the housing (210) and the insulating lining

(242). The piston cup (231) with the piston (222) is guided on the inside of the insulating liner (242).

The contact rods (220) align with the piston (222) by means of a pair of finger washers (246) which are centered in bores (247) on opposite sides of the piston. Each contact rod (220) is spring biased inwards by a leaf spring (248). Each contact rod (220) and leaf spring (248) has a notch (249) for engagement in a groove (250) in the finger washers (246). A spacer sleeve (252) is clamped to a threaded spacer (254) by a screw (256). The spacers (252) and (254) are arranged axially against the finger discs (246) with the spacers (252) and (254) in a cylinder (251) which is formed by the contact rods (220).

The main purpose of the spacer sleeve (252) is to control the contact force between the contact rods (220) and the transfer contact (224) when the contact rods (220) are disconnected from the spark contact (226). When the contact rods are disconnected from the spark plug, the contact rods are pressed against the spacer sleeve (252)

of the leaf springs (248) . A shift in the axial position of the reaction force against the contact rods from the spark contact (226) to the spacer sleeve (252) results in a reduction of the contact rods' force against the transfer contact (224) so that the magnitude of the contact force at the transfer contact is reduced when the contact rods (220) are disconnected from the spark contact ( 226). The size of this outwardly directed spring influence depends on the length of the spacer sleeve (252). A recess (257) is arranged on each contact rod (220) so that the pressure against the transfer contact (224) is located at the end (227) of the contact rod (220). A much lower contact force against the transfer contact (224) is tolerated because heating is not a problem in the very short time interval required to move the contacts from their open to their closed positions, i.e. on the order of 10 to 20 milliseconds.

Another purpose of the spacers (252) and (254) is to hold the contact rods (220) and leaf springs (248) in their slots

(250) to simplify the handling of cont.akt-annrrlnina<p>n m Ql

Preferably, a clearance is used between the spacer sleeve (252) and the contact rods (220) which is sufficient to allow some tolerance in the flight of the spark contact (226) in the contact device (219) and to allow normal erosion of the contacts.

The piston (222) is moved from the open position (a) to the closed position (b) by a pair of links (258) which are rotatably connected to the piston by means of a pair of piston pins (259). The piston pins (259) can also serve to attach the piston cup (2 31) to the piston (222).

Preferably, the piston (222), the cup (231), the joints (258) and the piston pins (259) are made of an insulating material. By avoiding the use of unnecessary conductive material near the contact device (219), the grounded housing (210) can be manufactured with a smaller diameter without the risk of spark formation. Conductive material in the contact device (219) is arranged within a diameter approximately equal to the diameter of the supply sleeve (212) and load sleeve (214) so that an approximately optimal ratio is achieved between energized parts and grounded coaxial parts to reduce the maximum electrical grease strength in the housing (210) . In addition, the use of only insulating materials where there is sliding contact, especially between the piston cup (231) and the insulating liner (242), prevents contamination of the insulating gas in the switch (205) due to conductive particles from wearing parts.

Figures 5 and 6 show that the joints (258) are connected to a fork (260) with a pair of pins (262). A crank or actuating arm (264) is welded to the fork (260) and extends through a tiltable bellows (266) which is soldered to the arm (264) to form a hermetic seal. The bellows (266) is soldered to a bellows holder (268) which is welded to the housing

(210). The arm (264) rests slidingly against a rocker arm (270) which is rotatably mounted to a rocker holder (272) which is in turn welded to the housing (210). The rotatable mounting of the rocker arm (270) to the holder (272) forms a pivot (273) for the arm (264). The pivot pin (273) passes through the tilting bellows (266) to provide sufficient freedom for the arm (264) with only a small load on the bellows (256). Movement of the crankshaft over an angle of approximately 32 degrees results in movement of the piston (222) via the links (258) between the closed position (a) and the open position (b).

An over-centered mechanism (274) is used to turn the rocker arm (270) so that the arm (264) is actuated. The mechanism (274) can be enclosed in a waterproof cover (276) which is attached to the housing (210) by means of a pair of conventional clamps (278) with a gasket (279) between the cover (276) and the housing (210). A conventional handle (280) is located outside the cover (276) and is connected to the over-centered mechanism

(274) through the cover (276) using a pair of coupling shafts (282) with O-rings (284). The gasket (279) and the O-rings

(284) keeps water and other extraneous objects out of the interior of the cover (276) which is kept under atmospheric pressure.

The coupling axes (282) are both fixed to a slot

(883) into the handle (280) with a scourer (285) and a washer (287). Each coupling shaft (282) is kept axially flush by a coupling holder (289) which is attached to the cover (276) with a screw (291).

The over-centered mechanism (274) comprises a U-shaped holding arm (286) which is rotatably mounted to the rocker holder (274) in line with and driven in a slot (293)

in each coupling shaft (282) . A stop (288) is rotatably mounted to the rocker holder (272), and engages in the grooves

(290) in the rocker arm (270) and is under pressure from an over-centered spring (292) at a distance from a holding shaft (294) which is attached to the holding arm (286). The movement of the holding arm (286) and the tilting arm (270) is limited by a device (295) which is attached to the holder (272).

In some applications for the switch (205), there will be no need for the waterproof cover (276) that encloses the over-centered mechanism (274). In this case, the handle (280) can be arranged to be directly attached to the holding arm (286), as shown in figure 1.

Sulfur hexafluoride, or another insulating gas, is introduced into the switch (205) while the cover (276) is removed, through an extension (296) and intake passage (298).

in the crank heat (264) . After introducing the desired amount of gas to the switch (205), a hermetic seal is formed by

to bend the extension (296) so that a fold (300) is formed.

The arm (264) is pressed against the inside of the housing (210).

a spring (302) with weak pressure acting through a spring washer (304). The increased pressure in the switch pushes the bellows (266) away from the housing (210) and compresses the spring (302) until the arm (264) rests against a stop washer (306) which is pressed against the rocker arm (270) by a strong spring (308) ). If a leak occurs in the switch, the weaker spring (302) will overcome the reduced pressure in the bellows (266) to displace the arm (264) towards the supply sleeve (212). In this case, the arm (264) is in a locked, non-operating position and the piston

(222) is locked either in the first or the second position by a device (310) which rests against the fork (260). The facility

(310) is attached to a collar (312) which is welded to the housing

(210), the collar (312) surrounding the supply sleeve (212). Normal pressure in the housing (210) will bring the fork: (260) to position away from the plant (310) so that the piston (222) can be actuated between the first and second positions.

If an abnormally high pressure develops in the housing (210), the outwardly directed pressure from the bellows (266) will be greater than the pressure from the strong spring (308) and the stop disc

(306) will be pushed away from rocker arm (270). This will cause a blade (314) and/or a point (316) attached to the rocker arm (270) to puncture the bellows (266). This safety measure prevents an explosion of the switch should an abnormal amount of gas develop in the switch. If the bellows (266) is punctured by the blade (314) and/or the point (316), the resulting low pressure will lock the piston (222) and the arm

(264) as described above.

A side window (318) is arranged in the cover (276) for visual indication of the pressure in the housing (210). A Cape

(320) which is mounted on the arm (264) has colored low and normal indications which can be seen one at a time through the side window (318). When there is a correct pressure level in the housing

(210), the indication "normal" will be visible through the side window. When a low pressure allows the arm to be pushed so that the fork is locked by the device (310), the indication "low" will be visible through the side window. If the bellows (266) is punctured by the blade (314) or the point (316) as a result of abnormally high pressure in the switch, the fork (360) will rest against the device (310) as a result of the low pressure that occurs and the indication "low" will be visible through the side window.

A visual indication of the contact device's

(219) position is achieved through an upper window (322) in the cover

(276). A position indicator (324) with appropriate marks for "open" and "closed" is connected to the casing (320)

and is pressed against the upper window by a clamp (326).

A molecular sieve (328) is held in a holder (330)

of a screen (332). The insulating liner (242) holds the screen in place to hold the molecular sieve in the holder against the load sleeve (214). The small size of the switch (205) results in a large ratio between the surface area and the volume in the housing (210). Therefore, a significant concentration of unwanted moisture from the inner surfaces can be present after the switch (205) is closed. The molecular strainer (328) attracts moisture from the interior of the housing (210) and gas contaminants that occur due to wear and/or sparking in the switch.

The insulating lining (242) is held against the screen by a lining system (334) which is attached to the collar (312). A further molecular sieve (329) may be held under the collar (312) by a pair of tongues (335) on the liner assembly (334).

A bracket (334) is welded to the housing to allow the switch (205) to be positioned with a channel (336) attached to the bracket (334) by a pair of screws

(338). The channel (336) can be used to support the switch

(205) and/or place further switches according to the invention, (parallel to the switch (205), for example to form a collection of 3 single-phase switches. A rod (340) extends through the switch's (205) handle (280) and can activate each switch simultaneously to disconnect the phases in a 3-phase arrangement. The screws (338) can be used for grounding the housing (210). A shield wire (342) from each power cable (217) is clamped under a corresponding screw

(338). The switch (205) takes electrodes for capacitive determination at relatively low voltage both of the switch's conductors with high voltage and the open and closed position of the contacts. The insulating liner has a first conductive band (350) and a second conductive band (352) arranged in contact with the annulus

(342) which is located axially at a distance from the spark contact

(226), respectively the transfer contact (224). On the conductive bands (350) and (352) the solder belongs to the first and second resilient clamps (354) and (356) which abut against the first and second connections (358) and (360). The first and second connections (358) and (360) are insulated and hermetically sealed relative to the first and second nipples (362) and (364) with associated first and second plugs (360) and (368). First and second nipples (362) and (364) extend through the housing (310) and are hermetically attached to this by soldering. First and second threaded caps (370) and (372) rest against first and second nipples (360) and (368) respectively and can be used to protect the connections (358) and (360) when they are not in use.

Whether it is used individually or combined

with several, the switch (305) is sufficiently light and compact that it can be carried by the cables (217) which are connected to the rod (216) for power supply and the rod (218) for the load current, if this is desired.

During use, moving the handle (280) away from the housing (210) will cause the holding arm to rotate so that the over-centered spring (292) is compressed against the holding arm

(286) is in line with the estimate (288). Still moving

of the handle results in a rapid rotation of the rocker arm

(270) by means of the stop (288) so that there is a snap action of the piston (222) and the contact device (219) from (a) the closed position, to (b) the open position, regardless of the speed of the handle (280) moved with. Conversely, movement of the handle (280) towards the housing (210) will cause the piston (222) and contact device (219) to snap from (b), the open position to (a) the closed position regardless of the speed at which the handle (280) is moved with.

When the contact device (219) snaps from (a) the closed position (b) the open position, the ends (221) of the contact rods (220) are moved out of contact with the spark contact

(226). This results in a spark being drawn between the contact rods (220) and the spark contact (226) when there is a load current in the switch (205). The rapid movement of the piston (222) develops a flow of insulating gas through the holes (230) in the piston (222), the gas being directed around the first ends (221) of the contact rods (220) and through the nozzle (232) to smother the spark. The gas flow increases the pressure in the piston cup (231) which holds the check valve

(234) closed against the piston cup so that all gas flow is directed towards the nozzle (232).

The increased pressure in the piston cup (231) due to the flow of insulating gas through the nozzle (232) will stabilize the contact device (219) speed to ensure a continued flow of insulating gas through the nozzle (230) when the flow is reversed after the separation of the contact rods ( 220) from the spark contact (226) over a distance that is sufficiently large to exclude new spark development. The volume of the insulating gas downstream of the nozzle (232) in the housing (210) comprises the volume of the annulus

(245) volume and is greater than the remaining volume of the insulating gas in the housing (210) and enables the expansion of the insulating gas heated by the spark without significantly increasing the pressure on the back of the nozzle.

The equalization of the gas pressure in the housing (210) downstream of the nozzle (232) and in the annulus (245) causes some flow of insulating gas through the molecular sieve (328). Particles from wear and vaporized products that may be present in the insulating gas are directed towards the molecular sieve (328) where they are captured as a result of the gas flow through the sieve (328) and due to the sieve's (328) attracting properties. Additional wear and vapor products are attracted to the additional molecular sieve (329).

When the switch (205) is actuated to connect a load by moving the contact device (219) from (b), the second position to (a) to the first position, the check valve (234) is opened by displacing the valve pin (235) away from the holes (332) in the piston cup (331) so that the pressure is released in front of the moving piston cup (231) to allow a faster snapping movement of the contact device

(219) from (b) the second position to (a) the first position in order to prevent spark formation when the first end (221) of the contact fingers (220) comes into contact with the spark contact (226).

When the spark contact (226) or the transfer contact (224) is energized with alternating current, a corresponding voltage can be measured at the associated first and second connections

(358) or (360). A voltage of 15kV either at the spark contact (226) or the transfer contact (224), results in a voltage of 225 V being connected to the corresponding first or second • conductive bands (350) or (352) so that a high voltage on one of the contacts can be detected with conventional equipment connected to the associated connections (358) and (360). If the voltages measured at the first and second connections

(358) and (360) indicate that one contact is energized while the other is not energized, there is a further indication that the contact device (219) is in the open position.

If the spark contact (226) and the transfer contact (224) turn out to have the same condition during these measurements (both energized or both not energized), a high-frequency power source can be connected to the first or second connection (358) or (360) to determine contact devices

(219) position, as described above.

Figure 7 shows another embodiment of the switch

according to the invention. The switch (5) comprises an earthed receptacle (10) which is a cylindrical metal housing. The thickness of the housing in the version shown is 0.8 mm. Sleeves (12) and (14)

are mounted at opposite ends of the container. Conductive rods (16) and (18) extend through the housings (12) and (14). The part of each sleeve that extends from the outside of the sleeve

can be easily connected to components in a distribution network, for example a cable or transformer by connection or by a movable elbow connection, as described in more detail below. Parts of the sleeve's conductor extend into the interior of the switch and are arranged for contact with the device (19), the contact device comprising a cylindrical metal tube (20) with axial slots and a piston (22). In a first position, the contact device with each conductive rod (16)

and (18) make contact with the transfer contact (24) and the spark contact (26). The piston (22) has several holes, of which 2 holes (28) and (30) are shown, as these are continuous in order to

take a stream of insulating gas which is formed by the displacement of the gas by the downward movement of the piston in the container (10). A nozzle (32) is attached to the piston (22) on

same side of the disc as the spark plug (26). The mouthpiece

(32) contains non-return valves (34) and 36) to control the gas flow as described below. The switch (5) is also an intake valve (38) for the introduction of sulfur hexaflouride, or another insulating throttle, into the switch. Sulfur hexaflouride fills the body of the switch (5) as well as the clearance (40) between the earthing container (10) and an insulating liner (42). The insulating lining (42) can be made of a compact dielectric or other suitable insulating medium.

The earthing container (10) has a tiltable bellows (50) through which a heat exchanger (52) extends in it

substantially radially into the body of the switch. The bellows allows movement of the crankcase (52) while maintaining a hermetic seal of the container. The heat exchanger is designed as a fork to enclose the space for the sleeve which is grounded. A pair of diametrically opposed links (52) (partially shown) are connected to the piston (22). To activate the switch, an external actuator (not shown) is connected to the road heater (52) end. When the actuator is actuated, a downward movement of the crankshaft (52) will influence the joint (54) to move the piston (22) downwards. As the piston (22) is continuous with the rest of the contact device (20), the entire contact device (20) will be moved downwards. The transfer contact (24) slides down the conductor (16) and the spark contact (26) will move away from the conductor (18) so that a clearance is created over which it is pulled

a spark. This movement of the piston (22) causes a flow of insulating gas through the holes (28) and (30) while the check valves (34) close. The insulating gas is forced through the nozzles (32) which, due to their shape, cause the gas to flow essentially axially along the clearance to thus suffocate the spark that has occurred between the spark contact (26) and the conductor (18).

The outer ends of the conductors (16) and (18) can be electrically connected to the distribution network in an appropriate manner. When the switch (5) is inserted in an electrical circuit the container is

(10) grounded in a known manner. Figure 7 shows the grounding cable

(60) which is connected to the container (10) by means of a nut (62).

The switch according to the present invention can be connected to an electrical network between a load and a power source using known devices. For example, the conductors (16) and (18) can be spliced to power cables which are connected to electrical equipment, for example transformers or motors, interconnected with other electrical components, for example fuses or the like (especially shielded fuses for example as described in US application 400,509), for example with other switches of the same type, as described below and several other possibilities. It is a significant advantage of the switch according to the invention that it can be easily connected to other electrical components in a distribution system. An appropriate way to connect the switch to other electrical equipment is by means of an elbow connection. Molded elastic elbow-shaped connectors typically have a sleeve space for connection with a sleeve belonging to electrical equipment for interconnection by insertion and a second space arranged to receive a power cable or sleeve belonging to another electrical component.

Figure 8 shows three single-phase switches according to the invention which are electrically connected to a three-phase transformer bushing. The switches (70,72 and 74) on

figure 8 is connected to a transformer's (80) sleeves by means of elbow connectors (76,78 and 80). The switches are connected with a mechanism (82) so that the three switches are moved simultaneously when activated. The other ends of the switches (70, 72 and 74) are connected with cables (84, 86 and 88) in a known manner (not shown), for example insertable, separable connections, splicing or the like.

Figure 9 shows three single-phase switches for the same phase connected in a loop system. The switches (90, 92 and 94) are shown connected by elbow connectors (96, 98 and 100). As the switches are connected in a loop system, the switches will be activated individually using road heaters (102, 104 and 106). The switches are connected in a loop arrangement in a closure (108).

Although the present invention has been described in detail according to particular preferred embodiments, other modifications are also possible. For example, a single rocker arm can be connected to only one over-centered mechanism

so that this simultaneously affects the road heat in the switches in a 3-phase construction. Furthermore, another embodiment may include a stationary partition wall near the transfer contact which limits the flow of insulating gas in front of the piston which is moved to increase the flow through the nozzle without reducing the volume of insulating gas in the housing.

Claims (52)

1. Switch consisting of (a) a housing, (b) first and second opposite conductors in the housing, (c) a contact device between the conductors which can be moved between a first, closed position in electrical contact with both conductors and a second open position with contact only to the second conductor, CHARACTERIZED IN THAT it comprises (i) several electrically conductive rods arranged in a cylindrical shape around the conductors, the rods being in sliding contact with the second conductor and, when near the closed position, in sliding contact with the first conductor, and that (i) pressure devices are present to exert an inwardly directed force against the rods, directed at both conductors, the force having a first level when the contact device is in the first closed position and a second level when the contact device is not in contact with the first leader, as it the first level is larger than the second level. 2. A switch according to claim 1, wherein the housing is permanently hermetically sealed and contains an insulating gas at a pressure greater than 196 kPa CHARACTERIZED BY comprising (a) an actuation arm extending through the housing and movable between first and second positions, (b) a bellows that is hermetically closed to the arm and to the housing, the bellows being able to pivot when the arm is moved between the first and second positions, and (c) the device connecting the arm to the contact device so that the contact device upon movement of the arm between the first and other positions in a similar way are moved between the closed and the open position. 3. Switches according to claim 2, CHARACTERIZED IN THAT the housing has opposite ends and a cylindrical side and first and second conductors which are coaxially arranged at opposite ends of the housing, and that the arms and bellows are arranged on the cylindrical side of the housing. 4. Switches according to claim 3, CHARACTERIZED IN THAT the arm is mounted rotatable. 5. Switches according to claim 1, CHARACTERIZED IN THAT the housing has opposite ends and a side and that the conductors are arranged on opposite sides of the housing, and that the switch comprises (a) an activation arm which extends through the side of the housing and is rotatable in relation to to this between the first and second positions, and (b) devices which connect the arm to the contact device so that the contact device is moved between the closed position and the open position in a corresponding manner when the arm is moved between the first and second positions. 6. Switches according to claim 1, CHARACTERIZED IN THAT it comprises (a) filling devices for introducing insulating gas into the housing, and (b) closing devices for sealing the housing and the filling devices. 7. Switches according to claim 6, CHARACTERIZED IN THAT it comprises a molecular file to remove moisture in the housing. 8. Switches according to claim 1, mounted in a circuit with from 1-36 kV and designed for continuous transmission and interruption of at least 100 A, CHARACTERIZED BY THE fact that the housing is grounded and has a cylindrical shape with a diameter of less than 150 mm . 9. Switches according to claim 8, CHARACTERIZED BY the fact that it is connected in a circuit with at least 10 kV. 10. Switches according to claim 1, CHARACTERIZED IN THAT the housing is cylindrical, and that the contact device is arranged so that it can serve as an axially movable piston in the cylindrical housing. 11. Switches according to claim 10 with an insulating gas in the housing and a nozzle on the contact device to direct the insulating gas towards the conductive rods and the first conductor and where the contact device pumps insulating gas through the nozzle towards the first conductor when the contact device is moved from the closed position to the open position, CHARACTERIZED IN THAT it comprises (a) an insulating liner arranged in and spaced from the housing with an annular space between the liner and the housing, the insulating liner serving as a cylinder for the contact device, and (b) a sealing device in the annulus between the liner and the housing where the sealing device separates the housing into first and second sections near the first and second conductors, the first section comprising the annulus and the first section being larger than the second section so that the first section contains more insulating gas than the second section . 12. Switches according to claim 10, CHARACTERIZED IN THAT it comprises an insulating liner in the housing, the insulating liner serving as a cylinder for the contact device. 13. Switches according to claim 10, CHARACTERIZED IN that it is permanently hermetically sealed and contains an insulating gas at a pressure greater than 196 kPa. 14. Switches according to claim 1, mounted in a circuit with at least 1 kV, CHARACTERIZED IN THAT the housing is conductive, grounded, cylindrical and coaxially arranged in relation to the first and second conductors and placed between the first and second conductors and respectively the grounded housing for measuring voltages on first and second conductors by capacitive separation. 15. Switches according to claim 14, CHARACTERIZED IN THAT a cylindrical insulating liner is arranged in and separated from the housing, with an annular space between the liner and the housing, the contact device being designed to act as a in the cylindrical insulating liner axially movable piston and that conductive bands are arranged on the insulating liner. 16. Switches according to claim 1, CHARACTERIZED IN THAT the pressure device comprises leaf springs with opposite first and second ends, the first end pressing the rods against the first conductor and the other ends pressing the rods against the second conductor when the contact device is in the closed position, as the force against the first conductor at the second level is essentially equal to 0. 17. Switch mounted in a circuit of at least 1 kV, CHARACTERIZED IN THAT it comprises (a) a cylindrical, conductive, earthed housing, (b) first and second opposing conductors coaxially arranged in the housing (c) a contact device for opening and closing the circuit between the first and second opposing conductors, and (d) first and second conductive bands arranged coaxially between the first and second conductors and at grounded housings for measuring voltages on the first and second conductors by capacitive splitting. 18. Switch CHARACTERIZED BY comprising (a) a permanently hermetically sealed housing containing an insulating gas at a pressure greater than 196 kPa, (b) first and second opposed conductors in the housing (c) a contact device at a first conducting position and at a second non-conducting position, (d) an actuating arm extending through the housing and moving between first and second positions, (e) a bellows hermetically sealed to the arm and to the housing, the bellows being able to tilt when the arm is moved between first and second positions, and (f) devices that connect the arm to the contact device so that the contact device, when the arm is moved between first and second positions, is correspondingly moved between a closed position and an open position. 19. Switch according to requirement 18, CHARACTERIZED IN THAT the arm is rotatably mounted. 20. Breaker according to claim 18, CHARACTERIZED IN THAT it is mounted in a circuit with between 1 and 36 kV and can continuously transmit and interrupt at least 100 A, CHARACTERIZED IN THAT the housing is grounded and designed cylindrically with a diameter that is less than 150 mm . 21. Breaker according to claim 18, CHARACTERIZED IN THAT the housing has opposite ends and a cylindrical side and that the first and second conductors are arranged coaxially at opposite ends of the housing, and that the bellows and the arm are arranged on the cylindrical side of the housing. 22. Breaker according to claim 21, mounted in a circuit with 1-36 kV for continuous transmission and interruption of at least 100 A, CHARACTERIZED IN THAT the housing is grounded and has a cylindrical shape with a diameter less than 150 mm. 23. Switch CHARACTERIZED BY comprising (a) a permanently sealed housing which is conductive, earthed, cylindrical in shape and made of metal and having opposite ends and one side, (b) first and second opposite conductors at the ends of the housing, (c) a contact device between the conductors movable between a first closed position in electrical contact with both conductors and a second open position where it does not make contact with either conductor, (d) an actuation arm extending through the side of the housing and movable between first and second positions, (e) a bellows that is hermetically sealed to the arm and the housing, the bellows being able to deflect tilting when the arm is moved between the first and second positions (c) devices connecting the arm to the contact device so that the contact device, when the arm is moved between first and second positions, moved between the closed and open positions, and (g) an insulating gas in the housing at a pressure not greater than 196 kPa. 24. Switch mounted in a circuit with from 1 - 36 kV and capable of continuously transmitting at least 100 A, where the switch comprises (a) an earthed, conductive, cylindrical housing with opposite ends and one side and with a diameter of less than 150 mm, (b) first and second opposed conductors at opposite ends of the housing, (c) a contact device between the conductors which moves between a first closed position in electrical contact with both conductors and a second position in contact with only the second conductor, CHARACTERIZED BY that the contact device comprises (i) several electrically conductive rods arranged cylindrically around the conductors, the rods having sliding contact with the second conductor and, sliding contact with the first conductor when it is close to the closed position, (ii) pressure devices for exerting an inward directed force on the rods towards both conductors, the force having a first level when the contact device is in the first closed position and a second level when the contact device is not in contact with the first joint is, the first level being larger than the second level, (d) an actuation arm extending through the housing and movable through first and second positions, (e) a bellows hermetically sealed to the arm and to the housing, the bellows being able swing tilting when the arm is moved between the first and second positions, (f) devices which connect the arm to the contact device so that the contact device, when the arm is moved between the first and second positions, is moved correspondingly between the closed position and the open position, (g) an insulating gas in the housing, (h) an insulating liner in and at a distance from the housing, with an annulus between the liner and the housing, the insulating liner serving as a cylinder for carrying contact devices, (i) sealing devices in the annulus between the liner and the housing, the sealing device divides the housing into first and second sections close to the first and second conductors respectively, where the first section includes the annulus, the first section is larger than the second section so that the the first section contains more insulating gas than the second section, (j) a nozzle on the contact device for directing the insulating gas towards the conductive rods and the first conductor, the contact device being adapted to act as a piston in the insulating liner and pumping it insulating gas in through the nozzle toward the first conductor when the contact device is moved through the closed position to the open position and (k) first and second conductive bands on the insulating liner arranged coaxially between the first and second conductors and the grounded housing to measure voltages on the first and other managers at the capacitive department. 25. A circuit breaker mounted in a circuit rated from 1 to 36 kV and capable of continuously transferring and interrupting at least 100 A, CHARACTERIZED IN THAT it comprises (a) a grounded, conductive and cylindrical housing with opposite ends and a diameter of less than about 150 mm, (b) first and second opposed stationary conductors arranged coaxially at opposite ends of the housing, (c) a contact device between the conductors movable between a first closed position in electrical contact with both conductors, and a second open position in contact with the second manager. 26. Switch according to claim 25, CHARACTERIZED IN THAT the circuit has at least 10 kV and that the housing is hermetically sealed and contains an insulating gas with a pressure greater than 196 kPa. 27. Switches for continuous transmission and interruption of between 1 and 36 kV and at least 100 A, CHARACTERS-.. INCLUDING that it comprises (a) an earthed, conductive, cylindrical housing with opposite ends and a diameter less than 150 mm, ( b) first and second opposed stationary conductors arranged coaxially at opposite ends of the housing, and (c) a contact device between the conductors movable between a first closed position in electrical contact with both conductors and a second open position in contact only with the second conductor . 28. Switch which directly interconnects first and second suspended cable sections in an electric power system, with between 1 and 36 kV and which can continuously transmit and interrupt at least 100 A, CHARACTERIZED IN THAT it comprises (a) a housing with opposite ends, (b) first and second opposed conductors in the housing with external connections to the respective ends in the housing, under tension connected to the respective cable sections for carrying the switch by means of the cable sections, and (c) a contact device between the conductors which can be moved about a first closed position with electrical contact with both managers and a second open position with contact only with the other manager. 29. Device, CHARACTERIZED IN that it comprises (a) several switches each consisting of (a) a housing, (b) first and second opposite conductors in the housing, (c) a contact device between the conductors which can be moved between a first closed position with electrical contact to both conductors and a second open position with contact only to the second conductor, the device comprising (i) several electrically conductive rods arranged cylindrically around the conductors, the rods having sliding contact with a second conductor and when the device is located close to the closed position, has sliding contact with the first conductor, (ii) pressure devices for exerting an inwardly directed pressure on the rods against both conductors, the force having a first level when the contact device is in the first closed position and a second level when the contact device is not in contact with the first conductor, the first level being larger than the second level, (B) bracket means for mounting the switches arranged in parallel, and (C) actuation means is connected to each switch to move the individual contact devices simultaneously. 30. Device according to claim 29, wherein each housing has opposite ends and a cylindrical side and first and second conductors arranged coaxially at opposite ends of the housing, and wherein each housing is conductive, grounded, permanently hermetically sealed and contains an insulating gas at a pressure greater than 196 kPa, CHARACTERIZED IN that each switch comprises (a) an actuation arm extending through the side of the housing and movable between first and second positions, (b) a bellows hermetically sealed to the arm and to the side of the housing, the bellows can be tilted when the arm is moved between the first and second positions, and (c) devices which connect the arm to the contact device so that the contact device, when the arm is moved between the first and second positions, is similarly moved between the closed and the open position. 31. Device according to claim 30, CHARACTERIZED BY the fact that each switch further comprises (a) an insulating liner at a distance from the housing, with an annular space between the liner and the housing, the insulating liner serving as a cylinder for guiding the contact device, (b ) sealing devices in the annulus between the liner and the housing, which divides the housing into first and second sections near the first and second conductors, the first section comprising the annulus, the first section being larger than the second section so that the first section contains more insulating gas than the second section, and (c) a nozzle on the contact device for directing the insulating gas towards the conductive rods and the first conductor, the contact device being adapted to act as a piston in the insulating liner and pumping insulating gas through the nozzle towards the first conductor when the contact device is moved from the closed position to the open position. 32. Device according to claim 29 which connects several first and second hanging cable parts in an electric power system with from 1 to 36 kV and at least 100 A, CHARACTERIZED IN THAT the housing has opposite ends and first and second opposite conductors at each end, that the housing has external connections to the ends of the housing and are connected in tension with the cable sections to hold the device by means of the cable sections. 33. Single-phase, earthed, closed load switch for use in electric circuits within the voltage range 1 to 36 kV, CHARACTERIZED IN THAT it comprises (a) a tight cylindrical housing consisting essentially of metal with a diameter in the order of 50 to 150 mm, ( b) first and second sleeve means which coaxially penetrate the cylindrical metal housing, one of the sleeves being mounted near one end of the housing and the other being mounted near the other end of the housing, the sleeves having a through-conductor, (c) a contact means which can receive a first position where it is in physical and electrical contact with the electrical conductor for each sleeve and a second position where it is physically and electrically separated from at least one of the conductors, (d) means for causing the contact device to move from the first position to the second position in order to thereby cause the connection device to be separated from at least one of the conductors and thus interrupt the current through the switch and correspondingly from the second position to the first position thereby bringing the contact device into contact with both conductors and thus forming a current path through the switch, and (e) an insulating gas in the housing which is maintained at a pressure of up to 490 kPa, the switch being arranged to be electrically switched between a load and a power source with a voltage in the range 1 to 36 kV. 34. Switch according to claim 33, CHARACTERIZED BY the fact that it further comprises devices for keeping the contact device flush with the conductors of the sleeves. 35. Switch according to claim 34, CHARACTERIZED IN THAT the holding device is a piston which extends from the contact device to the cylindrical housing. 36. Switch according to claim 35, CHARACTERIZED IN THAT the piston is made of an insulating material. 37. Switch according to claim 35, CHARACTERIZED IN that the piston has a relatively open structure to allow the insulating gas to be displaced by the piston so that it flows towards the contact device. 38. Switch according to claim 33, CHARACTERIZED IN THAT it further comprises a tubular body of a compact dielectric, arranged between the contact device and the cylindrical housing. 39. Switch according to claim 38, CHARACTERIZED IN THAT the tubular body is located close to the housing. 40. Switch according to claim 38, CHARACTERIZED IN THAT the tubular body is attached to the housing. 41. Switch according to claim 38, CHARACTERIZED IN THAT the tubular body extends over the entire length of the housing. 42. Switch according to claim 33, CHARACTERIZED IN THAT the insulating gas is sulfur hexafluoride. 43. Switch according to claim 42, CHARACTERIZED IN THAT the gas has a pressure of at least 196 kPa. 44. Single-phase load switch for use in electrical circuits within the voltage range up to 36 kV, CHARACTERIZED IN THAT it comprises (a) a tight cylindrical housing with a diameter in the order of 50 to 150 mm, (b) first and second sleeve devices coaxially penetrating the cylindrical metal housing, one of the sleeves being mounted near one end of the housing and the other sleeve being mounted near the other end of the housing, both sleeves having a continuous electrical conductor, (c) contact device arranged to assume a first position where it is in physical and electrical contact with the electrical conductors of both sleeves and a second position where it is physically and electrically separated from at least one of the conductors, (d) means for causing the contact device to move from the first position to the second position and thereby cause the contact device to separate from at least one of the conductors and thus interrupting current-but through the switch and on the other hand from the second position to the first position and thus bringing the contact device in contact with both conductors and thus create a path for a through current, (e) an insulating gas in the housing which is maintained at a pressure of from 98 to 490 kPa, the switch being arranged to be electrically connected into an electrical distribution network with a voltage in the range from 1 to 36 kV. 45. Device, CHARACTERIZED IN THAT it comprises a three-phase distribution network where each phase has a single-phase switch according to claim 44. 46. Device according to claim 45, CHARACTERIZED IN THAT the insulating gas is sulfur hexafluoride at a pressure of at least 196 kPa. 47. Device according to claim 46, CHARACTERIZED IN THAT it comprises a piston of an insulating material which extends from each contact device to keep the contact device flush with the conductors of the sleeves, each switch further comprising a tubular body of a compact dielectric between the contact device and the cylindrical housing to carry the stamp. 48. Device according to claim 45, CHARACTERIZED IN THAT it further comprises a metal housing which surrounds the switches, the housing containing an insulating gas which is maintained at a pressure of approximately 98 kPa. 49. Single-phase, earthed and enclosed load switch for use in electrical circuits within the voltage range from 1 to 36 kV, CHARACTERIZED IN THAT it comprises (a), a tight cylindrical housing substantially of metal, having a diameter in the range of 50 to 150 mm, (b) first and second sleeve means coaxially penetrating the cylindrical metal housing, one of the sleeves being mounted near one end of the housing and the other sleeve is mounted near the other end of the housing, and both sleeves have a continuous electrical conductor, (c) a contact device which can occupy a first position where it is in physical and electrical contact with the electrical conductor in each sleeve, and a second position where it physically and is electrically separated from at least one of the conductors, (d) means for causing the contact device to move from the first position to the second position thereby bringing the contact device out of electrical contact with one of the conductors and vice versa from the second position to the first position to thereby bring the contact device into electrical contact with both conductors, (e) an insulating gas in the housing maintained at a pressure of from 98 to 490 kPa, and (f) anor connections for bringing current with insulating gas to the area between the contact device and the conductor when the contact device is moved into and out of contact with the conductor, the switch being adapted to be electrically connected into an electrical power distribution system with a voltage in the order of 1 to 36 kV. 50. A single-phase, earthed, closed load switch for use in electric circuits in the voltage range 1 to 36 kV, CHARACTERIZED IN THAT it comprises (a) a close cylindrical housing substantially of metal with a substantially cylindrical side wall and a pair of opposite end walls, the diameter of the housing being in the range of 50 to 150 mm, (b) first and second sleeve means coaxially penetrating the cylindrical metal housing, one sleeve being arranged near one end of the housing and the other sleeve being arranged near the other end of the housing, both sleeves has a continuous electrical conductor, (c) contact device which can occupy a first position where it is in physical and electrical contact with each sleeve's electrical conductor, and a second position where it is separated physically and electrically from at least one of the conductors, (d) a bellows mounted in the cylindrical side wall of the housing and with an arm extending through this, the bellows being arranged to tilt when the arm is moved relative to the cylindrical wall and the arm is connected by contact the contact device via a trip valve, (e) devices which act on the arm to move the contact device axially from the first position to the second position and thereby bring the contact device out of contact with at least one of the conductors and thus interrupt the flow of current through the switch, and from the second position to the first position so as to bring the contact device into contact with both conductors and thus provide a path for current to pass through the switch, and (f) an insulating gas in the housing maintained at a pressure between 98 and 490 kPa, the switch being arranged to be electrically connected between a load and a current source at a voltage in the range 1 to 36 kV. 51. Device consisting of a single-phase, earthed and closed load switch for use in electric circuits in the voltage range 1 to 36 kV, CHARACTERIZED IN THAT it comprises (a) a tight cylindrical housing essentially made of metal with a diameter in the order of 50 to 150 mm . which can assume a first position where it is in physical and electrical contact with each sleeve's electrical conductor, and a second position where it is physically and electrically separated from at least one of the conductors, (d) means for causing the contact device to move from the first position to the second position thereby causing the contact device to separate from at least one of the conductors and thus interrupting the flow of current through the switch, and on the other hand from the second position to the first position to thereby bring the contact device into contact with both conductors and thus create a current path through the switch, and (e) an insulating gas in the housing maintained at a pressure between 98 and 490 kPa, being an electrical power cable with a voltage in the range 1 to 36 kV is directly connected to the device. 52. Device, CHARACTERIZED IN THAT it comprises (A) a single-phase earthed, closed load switch for use in electric circuits in the voltage range 1 to 36 kV with (a) a tight cylindrical housing essentially made of metal and with a diameter between 50 and 150 mm . arranged to assume a first position where it is in physical and electrical contact with both sleeve electrical conductors, and a second position where it is physically and electrically separated from at least one of the conductors, (d) means for causing the contact device to move from the first position to the second position and thereby cause the contact device to separate from at least one of the conductors and thus interrupt the flow of current through the switch, and on the other hand from the second st illing to the first position where it contacts both conductors so as to produce a current path through the switch, (e) an insulating gas in the housing maintained at a pressure ■ > between 98 and 490 kPa, (B) a transformer with an output -voltage in the range of 1 to 36 kV, the transformer having an outlet sleeve, and (C) a disconnectable elbow connector with a molded resilient portion having first and second sleeve spaces adapted to receive and electrically interconnect the sleeves of electrical equipment/where the first sleeve space is connected to a sleeve on the switch and the other sleeve space is connected to an outlet on the transformer.