CN1246208A - Switching device including spark gap for switching electrical power - Google Patents

Abstract

A device for switching electric power comprises at least one electric switching arrangement (5). This switching arrangement comprises at least one switching element (10a) comprising an electrode gap (24). This gap is convertible between an electrically substantially insulating state and an electrically conducting state. Furthermore, the switching element comprises means (25) for causing or at least initiating the electrode gap or at least a part thereof to assume electrical conductivity. The means (25) for causing or at least initiating the electrode gap to assume conductivity are adapted to supply energy to the electrode gap in the form of radiation energy to bring the gap or at least a part thereof to the form of a plasma by means of this radiation energy.

Description

Switchgear including spark gaps for switching power supplies

The invention relates to a device according to the preamble of claim 1 . The device according to the invention may be used in any connection made for switching purposes. The present invention is preferably applied in places where large power needs to be converted. Actually involves high voltage connections and power delivery applications. The best application of the device according to the invention is protection of electrical objects in power plants against faults, mainly current but also voltage, although this application is preferred, the device according to the invention does not limited to this application. In addition, the present invention also includes a method of securing an object.

The electrical object in question may have arbitrary characteristics as long as the object is included in the power grid and requires protection against faults related to overcurrents, ie in fact short-circuit currents. As an example, it may be pointed out that an object may consist of an electrical device with a magnetic circuit, such as a generator, transformer or electric motor. Other objects may also be in discussion, such as power lines and cables, power distribution devices, and the like. The application of the present invention will combine medium and high pressure. According to the IEC standard, medium voltage refers to 1-72.5kv, while high voltage refers to >72.5kv. This way, transmission, medium voltage transmission and distribution levels are all included.

In existing power plants of this nature, in order to protect the object in question, one has resorted to traditional circuit breakers (switchgears) of this design by providing galvanic separation for breaking. Since the circuit breaker must be able to break very high currents and voltages, this results in a larger capacity design with a high inertia, which is reflected in a longer opening time. It can be pointed out that the expected overcurrents are mainly short-circuit currents occurring in the connection to the protected object, eg in the electrical insulation system of the protected object due to a fault. This fault means that the fault current (short circuit current) of the external grid/equipment will flow through the arc. The result is a very severe breakdown. It may be noted that for the Swedish power grid the measure of the short-circuit current/fault current is 63 kA. In practice, the short circuit current can be equal to 40-50kA.

The problem with the circuit breaker is that it has a long opening time. The break time metric (IEC standard) to achieve full break is 150 milliseconds (ms). It is very difficult to reduce this off time to less than 50-130ms (depending on the actual situation). The consequence of this is that when there is a fault in the protected object, a large current will flow through the same object for the entire time required to initiate opening of the circuit breaker. During this time, the total fault current of the external power network draws a considerable load on the protected object. In order to avoid damage and complete breakdown of the protected object, according to the prior art, the object has been constructed such that it can withstand the short-circuit current/fault current during the opening time of the circuit breaker without significant damage. It can be pointed out that the short-circuit current (fault current) in the protected object consists of the influence of the object itself on the fault current and the additional current sent by the grid/equipment. The influence of the object itself on the fault current is not affected by the function of the circuit breaker, but the influence of the grid/equipment on the fault current depends on the operation of the circuit breaker. The need to construct the protected object so that it can withstand large short-circuit currents for a considerable time interval implies substantial drawbacks, namely higher equipment cost and reduced performance.

As indicated herein above, the present invention is not limited to protective uses. In other switching applications, when high powers are involved, it is disadvantageous to have to resort to relatively expensive high-capacity switching devices, such as semiconductor component assemblies, in order to realize the intended switching function. Current semiconductor components (preferably silicon semiconductor components, although semiconductor components of other materials are also contemplated) limit for practical reasons the maximum electric field strength that the component can withstand before electrical breakdown of the semiconductor material occurs. This immediately implies a corresponding limit on the maximum voltage the component can withstand. Especially in high-voltage connections, one is compelled to couple a large number of semiconductor components in series (semiconductor component groups) in such a way that none of the components contained in the semiconductor component group withstand voltages above the component safety level.

Furthermore, the design of the semiconductor components is complex because, for example, the semiconductor material itself is guaranteed to withstand very high electric field strengths compared to the atmosphere. But this design is ineffective for the insulating material that must exist between those electrodes outside the semiconducting material between which the high voltage is placed. This also involves a limitation: In the design of semiconductor components using high voltages, care must be taken to achieve a balance between the electric field strength in the semiconductor and the resistance in the surrounding insulating medium.

In several applications used in power plants, the components included therein have to withstand not only high voltages but also high currents. When an electric current flows through an element having a certain resistance, a considerable amount of heat (so-called Joule heating energy) is proportional to said resistance and proportional to the square of the current. Since the resistance of each semiconductor element is small and almost negligible, the maximum current that the element group can withstand is limited. If a large current is to be conveyed through the semiconductor element, one has to convey the current through several identical parallel current paths. Therefore, the number of semiconductor elements is multiplied.

Where there is high voltage and high current, a large number of semiconductor components must be used. Reliability is low since all elements have to work to put the power plant into operation (eg HVDC valves).

The fact that semiconductor components are piled up in large numbers means that they must be controlled with great precision in timing. Incorrect "timing" could, for example, result in too high a voltage being applied to a single component, causing some sort of failure or disabling the entire power plant. Of course, this "timing" problem increases if multiple parallel current paths have to be set up and run synchronously.

The main object of the present invention is to provide a switchgear which is more suitable for switching large electric powers quickly and at a lower cost than the switchgears currently used.

A second object of the present invention is to provide a design approach and method of equipment in order to achieve better protection for any object and thus reduce the load on the object, which means that the object itself does not have to be designed so that it will withstand the Maximum short circuit current/fault current.

According to the invention, the switching device is designed according to the characterizing parts of claim 1 . Since the electrode gap of the switching device is made conductive by supplying radiant energy directly to the electrode gap in order to create ionization/plasma in the electrode gap, conditions are established according to the invention for a fast operation of the switching device. The ionization/plasma in the electrode gap creates/starts an electrically conductive plasma channel with a very high conductivity, allowing the transfer of very high currents, more specifically over relatively extended time intervals without negative impact, which is in stark contrast to conventional semiconductor technology.

According to the invention, the above-mentioned second object is achieved by a switching device in the form of an overcurrent reducing device, adapted to reduce the overcurrent by means of an overcurrent state detection device, connected to a power plant to protect the object. According to a preferred embodiment, the switching means may constitute an overcurrent diverter for diverting the overcurrent to ground or another element with a relatively low potential.

Therefore, in terms of protection, the present invention is based on the principle of using a fast operating switching device, the switching device described herein, which does not actually break the overcurrent, but reduces the current to the point where the object is protected. To this extent, this protection substantially reduces the subject's overexertion, thereby allowing the subject to suffer less damage. Therefore, the reduction of overcurrent/fault current means that the total energy injected into the protected object will be substantially less than if the switching device according to the invention were not present.

The switchgear-based solution according to the invention implies that the need can be advantageously met in order to achieve a satisfactory protective function. A very fast triggering can thus be achieved via the switching device, so that an occurring overcurrent-related fault is diverted via the switching device in good time with very little delay as soon as the electrode gap is already in the conducting state. It may be noted that the term "triggering" in this connection means bringing the switching device into a conducting state. By means of the arrangement of the switching means, said switching means are easily dimensioned to conduct very high currents. In order to obtain a satisfactory protection function, it is desirable that the current conduction path established by the switching device has a very low impedance. This means that the undue fatigue of the object, which is protected from fault currents, is relieved to the greatest possible extent. Furthermore, the switching device according to claim 1 can be provided with a high trigger safety function with very little effort. The triggering must not lead to failure in critical situations in order to divert the occurring fault current as quickly as possible. On the other hand, the switching device according to the invention offers the possibility of dimensioning in order to achieve a very high dielectric strength in the non-triggered state. This way, the chances of natural breakdown are minimized. Thus, preferably at least one laser is used for triggering.

According to the preferred refinements of a.o., the means for supplying radiant energy to the electrode gap are defined in the appended claims. According to one embodiment, in order to achieve the greatest possible certainty that the electrode gap assumes a conductive state, the electrode gap is supplied with radiant energy at two or more points or areas. According to an alternative design, the energy supply device can provide radiant energy along the elongated area on the conducting path between the electrodes. According to a preferred embodiment, the elongated region completely or substantially completely bridges the gap between the electrodes. While this is possible, where there are two or more points or areas providing radiation, the successive application to these points or areas amounts to propagation with respect to the conductive path between the electrodes, in this way, to A time delay is applied to these points and areas in succession, and generally preferably substantially simultaneously in accordance with the present invention, in order to momentarily conduct the electrode gap.

Furthermore, according to the present invention, the means for providing trigger energy may apply radiant energy in a cylindrical volume. This is especially effective when one of the electrodes includes an opening for providing radiant energy and the radiant energy is provided in a cylindrical volume relatively close to the electrode provided with the opening.

According to another alternative embodiment, the energy providing means may be designed to provide radiant energy in a plurality of substantially parallel elongated electrode regions extending between the electrodes.

Radiant energy may also be provided to the electrode gap perpendicular to the electrode axis in one or more points located between the electrodes.

The advantages of the switching device according to the invention can be used to implement different switching functions which are conventionally achievable by semiconductor technology. In other words, the switching device according to the invention can be constructed with a suitable number of electrical components whose properties are similar to those known, for example, in the field of semiconductor technology.

Further advantages and characteristics of the invention, in particular the method according to the invention, emerge from the following description and claims.

Embodiments of the present invention are described with reference to the drawings.

Figure 1 diagrammatically shows the basic scheme of the solution of the present invention,

Figures 2a-2d show in a block diagram and comparative manner fault current generation and energy generation with and without the device according to the invention;

Figure 3 shows a possible design of the device according to the invention in a block diagram;

Figure 4 shows in detail a possible design of the overcurrent reducing means in a block diagram;

Figures 5-7 are several different deformation figures similar to Figure 4;

Figure 8 shows an optical system for supplying energy to the electrode gap;

Figure 9 shows an alternative optical system placed on the side of one of the electrodes;

Figure 10 is another alternative optical system for providing energy around one of the electrodes and relatively coaxially without openings in one of the electrodes;

Fig. 11 is an optical system diagram based on the use of optical fibers;

Fig. 12 shows a schematic diagram of the refraction of light emitted from a point light source by refracting axonite;

Figure 13 is similar to Figure 16, but showing the effect of axonite on a collimated laser beam;

Figure 14 shows the function of refractive axonite to create an elongated focal zone between electrodes;

Figure 15 shows a graph of the power density along the focal zone in Figure 18;

Figure 16 is similar to Figure 18, but showing the use of diffractive optical elements;

Figure 17 shows focusing in an elongated region by reflection axonite;

Figure 18 shows a diffractive axonite (Kino hologram) capable of producing focal regions with different geometries;

Fig. 19 schematically shows the apparatus of the present invention applied in a power plant comprising a generator, a transformer and a power grid connected to the power plant;

Figure 20 shows how energy can be supplied to the electrode gap relatively perpendicular to the common axis of the electrodes, Figure 20a shows the delivery of radiant energy in a single point or area, while Figure 20b shows the delivery of radiant energy in three such points or areas energy;

Figures 21a and b illustrate how radiant energy is provided to form several substantially parallel conductive pathways between the electrodes;

Fig. 22 shows a side view of an embodiment somewhat similar to Fig. 10, it is evident from

Figure 23 is seen in a plurality of individual kino holograms (diffractive optical elements) disposed around one of the electrodes;

Fig. 24 shows a schematic form in which the switching device according to the present invention completes the function of a bidirectional triac switching element,

Figure 25 shows a functional diagram of a unidirectional triac switching element,

Figures 26-28 are three different examples of how the function of a bidirectional triac switching element can be realized by a switching device according to the invention, each switching device comprising two switching devices,

Figures 29a-d show that a switching device according to the invention can provide a thyristor-like function by coupling in series with one or more diode-functional elements,

Figures 30 and 31 are examples of how to use a switching device according to the invention in a triac function or in a thyristor function, and

Fig. 32 is a schematic diagram of the series switching function of the switchgear according to the present invention.

FIG. 1 shows a power plant including a protected object 1 . This object can be formed, for example, by a generator. The object is connected to the external distribution network 3 via line 2 . The unit indicated by 3 can also be replaced by other equipment included in the power plant for the grid. Assume that the power plant involved has the property that when a fault occurs in Object 1 causing a fault current to flow from Grid/Equipment 3 to Object 1 such that the fault current will flow through the Object, the primary protection of Object 1 itself is the influence of the fault current. The fault may lie in a short circuit formed in the object 1 . A short circuit is a conductive path between two or more points, which is an undesirable condition. The short circuit can be formed, for example, by an electric arc. Said short circuit and the resulting high currents can cause considerable damage and even complete breakdown of the object 1 .

It has been pointed out that, at least for some types of protected electrical objects 1 , short-circuit currents/fault currents which are harmful to said objects can flow from the protected object to the grid/installation 3 . Within the scope of the invention, it is used for protection purposes, not only to protect an object from externally originating fault currents from flowing through the object, but also to protect internal fault currents in the object from flowing in the opposite direction. This is discussed in more detail below.

In the following, for the sake of simplicity of description, the mark 3 is always constituted by the external power network. However, it should be kept in mind that other equipment may be involved than this grid, as long as said equipment enables a high current to flow through the object 1 in the event of a fault.

A conventional circuit breaker 4 is arranged between the object 1 and the grid 3 on the line 2 . This circuit breaker comprises at least one inherent detector for detecting the environment to indicate the fact that an overcurrent flows in the outgoing line 2 . This circumstance, which can be current/voltage or otherwise, indicates that a fault is imminent. For example, the detector may be an arc detector or a detector that records a short circuit sound or the like. When the detector indicates that the overcurrent exceeds a certain level, the circuit breaker 4 is activated to disconnect the connection between the object 1 and the grid 3 . But the circuit breaker 4 must break the total short-circuit current/fault current. Thus, circuit breakers must be designed to fulfill high placement requirements, which in practice means that operation will be relatively slow. The current/time characteristic curve in FIG. 2 a shows that _{the fault} current in the line indicated by 2 in FIG. 1 rapidly assumes magnitude i ₁ when a fault, such as a short circuit, occurs in fault object 1 at instant t fault . The fault current i ₁ is broken by the circuit breaker 4 at t ₁ within at least 150 ms after t _fault . FIG. 2d shows the diagram i ² ·t and the energy formed therein in the protected object 1 due to the short circuit. Therefore, the energy injected into the object as a result of the short-circuit current is represented by the total area of the outer rectangle in Fig. 2d.

It is in this connection indicated that the fault currents in Figures 2a-c and the currents in Figure 2d represent the envelopes of extreme values. For simplicity, only one polarity is drawn in the diagram.

The design of the circuit breaker 4 is such that galvanic separation is established by separating metal contacts. Therefore, the circuit breaker 4 usually includes auxiliary equipment required for arc suppression.

According to the invention, the line 2 between the object 1 and the switchgear 4 is connected to a device generally indicated by 5 . This device is usually designated as a switching device. In the application shown, the switching device has the function of means for reducing the flow of excess current to the equipment. During a period substantially shorter than the opening time of the circuit breaker 4, the device reduces the overcurrent by the overcurrent state detection means. Therefore, the device 5 is designed such that it is not necessary to create any galvanic separation. Thus, conditions are established to rapidly reduce the current without completely eliminating the current flow from the grid 3 to the protected object 1 . Compared with the situation in Fig. 2a, Fig. 2b shows an overcurrent reducing device 5 according to the present invention, once a short-circuit current occurs at time t _fault , the device is activated to reduce the over current to a level at time t2 i ₂ . The time interval t _fault −t ₂ thus represents the reaction time of the overcurrent reduction device 5 . Since the task of the device 5 is only to reduce the fault current and not to break it, it is possible to make the device react very quickly, as will be described in more detail below. As an example, it may be noted that the current reduction from level _i1 to level _i2 will be done within lms or a few ms after detection of an unacceptable overcurrent condition. The next objective is to achieve a current reduction in less than 1 ms, and preferably less than 1 microsecond.

As can be seen from FIG. 1 , the device also includes a further circuit breaker 6 which is arranged on the line 2 between the circuit breaker 4 and the object 1 . The switch is designed to break lower voltages and currents than the circuit breaker 4 and as a result it can be operated with a shorter opening time than the circuit breaker. The further circuit breaker 6 is set open until after but substantially before the circuit breaker 4 the overcurrent flowing from the grid 3 to the object 1 has been reduced by the overcurrent reducing device 5 . From what is said, another circuit breaker 6 should be connected to the line 2 in such a way that the current reduced by the overcurrent reducing device 5 flows through said switch and is thus opened by it.

Figure 2b shows another circuit breaker 6 in action. More precisely, the switch is designed to open at instant _t3 , which means that the duration of the current _i2 reduced by the overcurrent reducing device 5 is substantially limited, namely to the time period _{t2- t3} . The result is the injection of energy into the protected object 1 caused by the fault current from the grid 3, represented by the hatched surface in Fig. 2d. It appears that a substantial reduction in energy injection is achieved. In this connection it can be noted that, according to the particular model, since the energy increases with the square of the current, a reduction of the current by a factor of two reduces the energy injection by a factor of four. FIG. 2c shows how the fault current will flow through the device 5 .

Considering the size of the device 5 and the further circuit breaker 6 is such that the device 5 reduces the fault current and voltage to be broken through the further circuit breaker 6 to a substantially lower level. The actual opening time of the other circuit breaker 6 is 1 ms. But the dimensions should be such that the other circuit breaker 6 is not opened until the device 5 has reduced the current through the other circuit breaker 6 to at least a substantial degree.

Figure 3 shows in more detail how the device is realized. It is then pointed out that the invention can be used for both DC (also HVDC = High Voltage Direct Current) and AC connections. In the following example, it can be considered that line 2 forms one of the phases of a polyphase AC system. It should be remembered, however, that the purpose of implementing the inventive device is that either all phases are protected in the event of a detected fault according to the invention, or that the phase or phases in which the fault current occurs are reduced in current.

It can be seen from FIG. 3 that the overcurrent reducing device 5 includes an overcurrent diverter 7 for diverting the overcurrent to the ground 8 or another element whose potential is lower than the power grid 3 . In this way, the overcurrent diverter can be considered to constitute a current distributor that quickly establishes a short circuit to ground or low potential 8 in order to divert at least a substantial part of the current flowing in line 2 so that said current cannot reach the protected object 1 . If a serious fault such as a short circuit occurs in the object 1, it is the same size as the short circuit that can be established by the overcurrent diverter 7, it can be said that when the fault is close to the overcurrent diverter, the usual Said reduces the current flowing from grid 3 to object 1 by a factor of two. Thus seen in comparison with Fig. 2b, it can be said that the current level _i2 shown therein which is approximately equal to half of _i1 represents the worst existing situation. Under normal conditions, the aim is that the overcurrent diverter 7 should be able to establish a short circuit with better conductivity than the conductivity of the short-circuit fault in the corresponding protected object 1, so as to thus divert the main part of the fault current through the flow diverter 7 to ground or a lower potential . It can thus be seen that in the case of a common fault the energy injected into the object 1 at the time of the fault is substantially less than that represented in Figure 2d if as a result of the lower current level _i2 and the shorter time span _t2 - _t3 . Apparently, reliable protection is also obtained when the established short circuit has a conductivity slightly lower than that corresponding to a short circuit fault in the protected object 1 .

It has already been pointed out that the symbol 8 includes not only ground but also another element at a lower potential than the grid/plant 3 . It should therefore be noted that the element 8 may be constituted by another power network or another device included in the power plant, said device having a voltage level lower than that valid for the network/equipment 3 connected to the protected object 1 .

The overcurrent diverter 7 comprises switching means connected between the ground 8 or said lower potential and the line 2 between the object 1 and the grid 3 . The switching device comprises a control member 9 and a switch member 10 . The switch member is set open in the normal state, ie insulated from ground. However, the switching element 10 can be brought into the conducting state via the control element 9 within a very short time in order to establish a current reduction by conducting the current to ground.

The overcurrent state detection device shown in Fig. 3 comprises at least one and preferably several sensors 11-13 adapted to detect these overcurrent states requiring activation of the protection function. As can also be seen from FIG. 3 , these sensors may include a sensor 13 located in or near the object 1 . Furthermore, the detector means comprise a sensor 11 adapted to detect an overcurrent condition in the line 2 upstream of the connection of the overcurrent reducing means 5 and the line 2 . As explained below, it is expedient to provide a further sensor 12 to detect the current flowing in the line 2 to the protected object 1 , ie the current which has been reduced by the overcurrent reducing device 5 . Furthermore, it may be pointed out that the sensor 12, and possibly also the sensor 13, is able to detect a current flowing in the line 2 in a direction away from the object 1, for example in some cases energy magnetically stored in the object 1 produces a direction away from the object 1 current.

It can be pointed out that the sensors 11-13 do not have to be constituted by separate current and/or voltage detection sensors. Within the scope of the invention, the sensors can be of such a nature that they can generally detect any condition which indicates a characteristic failure requiring activation of a protective function.

In some cases, such a fault occurs so that the current will flow in a direction away from the object 1, the device is designed so that its control element 14 controls the closing of the other circuit breaker 6, and in addition activates the overcurrent reducing means once it has opened 5 so that the short-circuit current is diverted in the same way. For example, if it is assumed that the object 1 consists of a transformer, the effect of which is the occurrence of a short-circuit current such that the short-circuit current initially causes a high current to flow through the transformer, which is detected and the device 5 is activated for the purpose of current conduction. When the current to the transformer 1 has been reduced to the extent required, the other circuit breaker 6 is opened, but controlled by the switching element 14, not earlier than the departure time of the energy, when this happens , the energy magnetically stored in the transformer 1 flows out of the transformer 1 and is diverted via the device 5 .

Furthermore, the device comprises a control element 14 . This element is connected to sensors 11 - 13 , an overcurrent reducing device 5 and a further circuit breaker 6 . The operation of the device is such that when the control element 14 receives a signal indicating the occurrence of an unacceptable fault current flow to the object 1 via one or more of the sensors 11-13, the overcurrent reducing device 5 is immediately controlled so as to quickly provide the required current decreases. The control element 14 may be arranged to control the other circuit breaker 6 to switch off its operation when the sensor 12 has detected that the current or voltage has decreased sufficiently, and when the overcurrent is lower than a predetermined level. This design guarantees that the other circuit breaker 6 does not open until the current has indeed decreased to a certain level, which means that the other circuit breaker 6 has no task to open. It is not designed to open. current. However, it is also possible to replace the embodiment so that the other circuit breaker 6 is controlled to open at a certain predetermined moment after the overcurrent reducing device has been controlled to complete the current reduction.

The circuit breaker 4 may comprise its own detector means for detecting an overcurrent condition or instead the circuit breaker may be controlled via a control element 14 which also controls the overcurrent reducing means based on information from the same sensors 11-13 operation.

As shown in Figure 3, another circuit breaker 6 comprises a switch 15 with metal contacts. The switch 15 is operable between an open and a closed position by means of an operating member 16 , which in turn is controlled by a control element 14 . A parallel line 17 is connected in parallel across the switch 15, said parallel line comprising one or more elements 18, which avoids contact separation arcing of the switch 15 by conducting the parallel line 17 from the contacts displacing current. The design of these components is such that they can break or limit the current. Thus, the purpose is that the element 18 should normally keep the conduction path in the parallel line 17 open, but close the parallel line when the switch 15 is about to be opened, so that the current bypasses the switch 15 and the arc does not occur in that way. Arcs that would or could be present are effectively extinguished. Element 18 comprises one or more associated control members 19 connected to control element 14 for control purposes. According to one embodiment of the invention, said element 18 is a controllable semiconductor element, such as a GTO thyristor, with the necessary overvoltage braking means 30 .

An isolating switch 20 for galvanic separation is arranged in series with the one or more elements 18 in the circuit path established by the parallel line 17 . The isolating switch 20 is controlled by the control element 14 via the operating member 21 . The isolating switch 20 shown in FIG. 3 is itself placed in the parallel line 17 . This is of course unnecessary. As long as the galvanic separation can be ensured, the isolating switch 20 can also be coupled in series with the one or more elements 18 and placed in the line 2, so that the current has no possibility of flowing through the elements 18 in the conduction path established by the series coupling. sex.

Up to this point, the installation has been operated in the following way: when there is no fault, the circuit breaker 4 is closed like the switch 15 of the other circuit breaker 6 . Element 18 in parallel line 17 is non-conductive. The isolating switch 20 is closed. Finally, the switching device 10 of the overcurrent reducing device 5 is open, ie it is in a non-conductive state. In this case, the switching device 10 must of course have sufficient electrical insulation strength so that it cannot cause a conducting state. Thus, an overvoltage state or coupling method occurring in the line 2 as a result of the atmospheric environment (lightning strike) makes it possible for the voltage strength of the switching device 10 not to be exceeded in its non-conducting state. For this purpose, it is expedient to connect at least one overvoltage brake 22 in parallel with the switching device 10 . In this example, such overvoltage brakes are shown on both sides of the switching device 10 . The purpose of the overvoltage brake is therefore to divert the voltage, which would otherwise pose the risk of inadvertent breakdown of the switching device 10 .

The overvoltage diverter 22 shown in FIG. 3 is itself connected to the line 2 on either side of the switchgear 10 connected to the line. In principle, it is desirable that at least one overvoltage diverter be connected as closely as possible upstream relative to the switching device 10 . The overvoltage diverter 22 can also be connected to a branch line forming an electrical connection between the switching device 10 and the line 2 , which can also be indicated by a dashed line 26 in FIG. 3 . This configuration enables the integration of the switching device 10 and the at least one surge diverter 22 into a single electrical device which can be brought into conductive connection with the line 2 via a single connection.

When an overcurrent condition has been registered by some of the sensors 11-13 or by the sensor of the circuit breaker 4 itself (of course enabling the use of information from the sensor of the circuit breaker 4 itself as the basis for the control of the overcurrent reducing device 5 according to the invention) , the magnitude of this overcurrent state is that a serious failure of the object 1 is expected to occur soon, and the opening operation is initiated as far as the circuit breaker 4 is concerned. Furthermore, the control element 14 controls the overcurrent reduction device 5 to influence this reduction, more precisely, to bring the switching device 10 into electrical conduction via the control member 9 . As mentioned earlier, this can happen very quickly, i.e. in a fraction of the time required to open the circuit breaker 4, the reason why the object 1 is immediately protected is because the switching device 10 makes at least a substantial part, in fact the main part, of the current flow. The full short-circuit current of the grid 3 is partially diverted to ground or a lower potential. Once the current flowing to the object 1 via the other circuit breaker 6 has been reduced to the required level, the level can be determined by the time difference between the switching device 10 actuation and the circuit breaker 6 operating or by detecting the current in the line 2, for example by the sensor 12 On a purely time basis, the operating member 16 of the switch 15 is controlled via the control element 14 to open the contacts of the switch 15 . In order to eliminate or avoid the arc, the element 18 is controlled by the control member 19 to establish the conductivity of the parallel line 17, and the element 18 may be, for example, a GTO thyristor or a gas switch. When the switch 15 has been opened and thus provides galvanic separation, the control element 18 again brings the parallel line 17 into a non-conductive state. In that way, the current flow from the grid 3 to the object 1 is substantially cut off. After bringing the parallel line 17 into a non-conducting state, the galvanic separation can additionally be influenced by controlling its actuating member 21 from the control element 14 to disconnect the switch 20 . When all these events occur, opening is done by circuit breaker 4 at the occurrence of the last event. According to the first embodiment, it is important to be able to repeatedly operate the overcurrent reducing device 5 and the further circuit breaker 6 . In this way, when the circuit breaker 4 has been forced to open by the sensors 11-13, the switching device 10 is reset to the non-conducting state and the switch 15 and the disconnector 20 are closed again, so that when the circuit breaker 4 is next closed, the protection device is fully operational. According to another embodiment, it is contemplated that the overcurrent reducing device 5 needs to exchange one or more paths in order to operate again.

It can be pointed out that according to another alternative embodiment of the invention, the element or group of elements 18 is brought into the conducting state once the overcurrent reducing device 5 has been brought into the closed state, independent of whether the switch 15 may not be activated thereafter. disconnect. Then, element 18 may appear via control element 14 or via a control function involving blind follower device 5 closure, as previously described.

FIG. 4 shows a first embodiment of an overcurrent reducing device 5 with a switching device 10a. The switching device 10a has electrodes 23 and a gap 24 between these electrodes. As already described, the switching device has means 25a for triggering the electrode gap 24 to form a conductive path between the electrodes. The control member 9a is arranged to control the operation of the member 25a via the control element 14a. In this example, the means 25a are arranged to cause, or at least initiate, the electrode gap to become conductive by forming the gap or parts thereof into a plasma. Thus, it is important that the device 25a is able to quickly provide trigger energy to the electrode gap. Preferably, the triggering energy is provided in the form of radiant energy, which in turn affects the ionization/startup of the plasma in the electrode gap.

According to a preferred embodiment of the present invention, means 25a comprises at least one laser which, by supplying energy to the electrode gap, causes ionization/formation of plasma in at least part of the electrode gap.

According to the invention, the electrode gap 24 is preferably energized by means of one or several lasers or other means 25a, in this way the entire electrode gap is ionized and respectively forms a plasma and instantly renders the entire gap electrically conductive. sex. In order to conserve or make optimal use of the (generally) limited use of laser energy/effect, in the application of the present invention, the devices 25a are arranged such that they can only provide ionization/plasma in one or more parts of the gap 24. In the embodiment shown in accordance with FIG. 4 , FIG. 25 a provides radiant energy at a single point or area 28 . As described below, the invention also includes the application of radiant energy at multiple points or areas in the electrode gap, and also includes the application of radiant energy at one or both electrodes, or one or more electrodes extending continuously or substantially continuously between the electrodes. Radiant energy is applied in a rod-shaped area.

As shown in FIG. 4, by connecting the switching device 10a between the line 2 and the ground 8 (or another element with a lower potential), i.e. one electrode of the electrode 23 is connected to the line 2 and the other electrode is connected to the ground 8, A voltage difference occurs between the electrodes forming an electric field. The electric field in the gap 24 will be exploited in order to transfer or cause an electrical breakdown between the electrodes once the device 25a has been controlled triggered, ie has produced ionization/formation of plasma in one or more parts of the electrode gap. The electric field drives the ionization/formation of the established plasma to bypass the gap between the electrodes so as to create in this way a low resistance conductive path, ie an arc between the electrodes 23 . It may be noted that the invention is not limited to use in conjunction with the presence of such electric fields. Thus, the invention is that the means 25a should be able to establish conductivity between the electrodes also in the absence of such an electric field.

Since switching device 10a needs to be closed very quickly for current diversion, it is desirable to size the switching device in such a way that the electric field strength in gap 24 is sufficiently high to close safely when only a restricted portion, such as a point-like portion of the gap, is ionized. But on the other hand, it is required that the switching device 10a has a high electric strength to prevent breakdown between electrodes at its isolated location. The electric field strength in the gap 24 should therefore be correspondingly low. On the other hand this will reduce the speed by which the switching device establishes a current diversion arc between the electrodes. In order to achieve an advantageous relationship between the need for a safe triggering of the switching device on the one hand and the need for a high dielectric strength against undesired triggering on the other hand, it is preferred according to the invention to form the switching device in such a way: When the gap forms electrical isolation, the electric field strength in the gap 24 with respect to its entire operating environment does not exceed 30% of the field strength at which natural breakdown normally occurs. This relatively reduces the possibility of natural breakdown.

It is appropriate that the electric field strength in the electrode gap 24 in its isolated state does not exceed 20%, preferably not more than 10%, of the field strength at which natural breakdown usually occurs. On the other hand, in order to obtain an electric field in the electrode gap 24, which facilitates the formation of the arc at the ionization/formation of the initiated plasma in a part of the electrode gap in a faster manner, it is preferable that the electric field strength is less than the field strength at which natural breakdown normally occurs Suitably at least 0.1% and at least 1% (E ₄ ), preferably at least 5%.

It can be seen from FIG. 4 that the electrode gap 24 is enclosed in a suitable housing 32 . A vacuum or a suitable medium in the form of a gas or a liquid can be present in the gap 24 for this purpose. The case where the medium is a gas/liquid in the gap is formed in such a way that it can be ionized by triggering and form a plasma. In this case it is appropriate to initiate the ionization/formation of the plasma in the gap 24 at some point between the electrodes 23 . However, FIG. 4 shows the assumption that a vacuum or a suitable medium is present in the gap 24 . Closing activation is then effected by focusing the emitted radiant energy of the laser 25a via a suitable optical system 27 in at least one area 28 or in the vicinity of one of the electrodes, preferably as shown in FIG. 4 . This implies that the electrodes will operate as electron and ion emitters creating an ionized environment/plasma in the electrode gap 24, in this way an arc is formed between the electrodes. According to FIG. 4 , one of the electrodes 23 has an opening 29 through which the laser 25 a emits radiant energy to the region 28 by means of the optical system 27 .

Fig. 5 shows a variant 10b of the switching device in which instead the system laser 25b/optical system 27b focuses the radiant energy on the trigger area 28b, which is located between the electrodes and in the medium between these electrodes. Therefore, once triggered, a plasma will be formed bridging from this region to the electrode.

The variant 10c of the switching device in FIG. 6 differs from that in FIG. 4. In FIG. 6, an auxiliary electrode 31 has been placed between the electrodes 23c, said auxiliary electrode being adapted to be ring-shaped, so that the beam emitted by the laser 25c can pass through the auxiliary electrode 23c. electrode 31. These electrodes will work to smooth the electric field between the electrodes 23c, and these electrodes are isolated from each other, ie they can be on a floating potential. The auxiliary electrodes provide improved safety against natural breakdown, reduced size of the switching device and reduced sensitivity to external electric field influences. The auxiliary electrode is also susceptible to the laser beam/pulses causing it to emit free charges, which further improves the triggering capability.

FIG. 7 shows a modification 10d of the switching device, in which an electrode 31d is added, similar to that described with reference to FIG. 6 .

In order to obtain the relationship discussed above with respect to the state of the electric field strength between the electrodes 23 in the isolated state of the switching device, the characteristics of the switching device must of course be adequate for the intended use, ie the voltage state present on the electrodes 23. Useful constructive steps are of course related to the formation of the electrodes, the distance between the electrodes, the inter-electrode medium and the presence of another possible electric field affecting the inter-electrode elements.

The present invention may use diffractive optical elements. In diffractive optical elements, the wavefront of light determines the propagation of light, which is formed by diffraction rather than refraction. A special type of diffractive optics modulates only the phase, not the amplitude, of light due to the high transmittance of this type of element. Pure phase modulation can be achieved by providing a relief structure to the surface of the optical element, where the height of the relief should be of the same order as the wavelength for optimal functioning of the element. Another way to achieve phase modulation is to modulate the refractive index of an optical element, but this modulation is quite difficult. Diffractive optical elements can be fabricated by holographic processes, but cannot fulfill arbitrary functions. A more flexible mode of fabrication is computer generation, in which optical functions are calculated in a computer. In principle, completely arbitrary optical functions can then be realized, which are generally not possible with conventional refractive or reflective optics. The resulting working surface is thereafter converted into reliefs, for example by electron beam lithography or photolithography, both of which are well known in the semiconductor field. The resulting dator, phase-controlled surface relief elements are commonly known as kino holograms. A well-known example is the Fresnell lens. Like all diffractive optical elements, this lens can be designed as a binary structure consisting of only two relief layers, or as a multilayer relief, providing a substantial improvement in diffractive efficiency (the functional efficiency of the optical element).

Fig. 8 shows an embodiment based on an optical system 27e comprising a lens system 35 through which arriving laser pulses are transmitted to a diffractive optical phase element 36, ie a kino hologram. The element is designed to produce multiple focal points or focal spots 28e from a single incident laser pulse. These focal points 28e are distributed along the axis of symmetry between the electrodes 23e. Since the focal point 28e is distributed along the line between the electrodes 23e, a conductive path can be established between the electrodes more safely, which means that the highest possible trigger possibility.

The Kino Hologram 36 is low-absorbing and can therefore withstand extremely high optical fluences. The Kino hologram is therefore formed of an insulating material so that it does not severely disrupt the electric field between the electrodes.

According to the embodiment shown in Figure 8, radiant energy is provided through an opening 29e in one of the electrodes as previously described. FIG. 9 shows a variant in which, in general, the only difference compared to the embodiment of FIG. 8 is the radial placement of a diffractive optical element (Kino hologram 36f ) outside one of the electrodes 23f. As previously mentioned, the optical element 36f is designed to deflect the laser light rays and focus them on a plurality of spots or points distributed along the intended conductive path between the electrodes. The beamforms forming the beam at point 28f each have their own deflection angle. Thus, the beamformers must travel different distances to reach the respective points 28f. The advantage of the kino hologram 36f being located on the side of one of the electrodes according to FIG. 9 is that the kino hologram will be located on the side with the strongest electric field, so that the electric field interference is minimized. The design of the electrode is also simplified since no opening is required for the laser beam.

Figure 10 shows an embodiment in which a laser 25g symmetrically supplies laser radiation via an optical system 27g to a plurality of spots or points 28g distributed along the length of the electrode gap without requiring any openings in the electrode 23g. Optical system 27g includes a prism or beam splitter 37 for deflecting the laser beam around adjacent electrodes 23g. One or preferably more kino holograms 36g (diffractive optical elements) are placed around this electrode 23g to focus the laser beam at desired focal points 28g (possibly through additional lenses (lenses)) so that plasmas are generated at these points form.

Figure 11 shows a variation in which the laser beam is delivered through an optical system 27h comprising optical fibers 38 for forming focal points 28h at different positions between electrodes 23h. Optical fiber 38 is arranged to emit light through lens 39 .

Figure 12 shows the basic principle of conical lenses, so-called axons. The definition of this axonite can be said to be that each optical element is symmetric about rotation and is capable of deflecting light from a point source on the element's axis of symmetry by refraction, reflection, diffraction, or a combination of these, in such a way that the light is not as The axis of symmetry is intersected at only a single point as in conventional spherical lenses, but along a continuous line of points or speckles extending substantially along the axis.

As shown in Figure 13, the collimated (non-diverging) beam is deflected by the same angle by the axonite. In terms of rotational symmetry, each beam will intersect the axis of symmetry at some point.

It can be seen from Fig. 14 that the light rays can be converged by the axon 36i in the elongated focal region 28i located between the electrodes 23i. According to an embodiment of the present invention, the focal region may extend continuously across the entire gap between the electrodes, but may also extend along a part of the gap between the electrodes. Figure 15 shows the relationship between the light intensity and the distance between the electrodes. The solid line represents the intensity distribution over the beam brightness initially having a Gaussian intensity distribution, and the dashed line represents the intensity distribution over the beam brightness having a constant intensity distribution. Furthermore, it can be pointed out that the invention is not limited only to such purely linear conical axonites. Thus, axonites whose outer surface differs from a linear cone having a direct effect on the focal intensity distribution are included within the scope of the present invention.

As far as the focal region 28k is concerned, FIG. 16 shows that the same result as in FIG. 14 can be obtained by means of a diffractive optical element 36k, ie, a keno hologram.

Figure 17 shows that an elongated focal zone 28m can be obtained in the gap between the electrodes 23m by axonite, more precisely by reflecting axonite.

Figure 18 shows an embodiment in which specially designed diffractive axonite 36n kino holograms provide focal regions 28n and 28n' respectively having different shapes. In this example, the focal region 28n is elongated, disposed on the axis of symmetry of the axonite 36n and the electrode. In contrast, as indicated on the left side of FIG. 18, the cross-section of the focal region 28n' is cylindrical. Since the circumferential position of the cylindrical focusing region 28n' is relatively close to the electrode 29n provided with the opening, the advantage of the cylindrical shape is that it is closest to the electrode 23n provided with the opening 29n. Focal regions 28n and 28n' in FIG. 18 have substantially constant light intensity along the axis of symmetry, but in the case of focal region 28n, the light intensity distribution perpendicular to this axis is substantially Gaussian or formed according to a Bessel function.

The advantage of using fully or substantially conical or diffractive coaxial focusing elements such as those shown in Figs. The first formed plasmoids close to the radiating energy supplying electrode do not shield, reflect or so severely affect the radiant energy converging in points/areas located further away from the energizing electrode. Otherwise this "shadowing effect" by the initially formed plasmoid would prevent the radiant energy from effectively reaching the later focal point. This is a consequence of plasma's ability to reflect or absorb radiant energy.

Figure 19 shows an embodiment where the generator 1b is connected to the grid 3a via a transformer 1a. The protected objects are thus represented by transformer 1a and generator 1b. The overcurrent reducing device 5a and the further circuit breaker 6a and the normal circuit breaker 4a are obviously arranged in the combination shown in FIG. 1 , in this case it is imagined that the object 1 in FIG. 1 constitutes the object 1a in FIG. 19 . Therefore, it will be described here in conjunction with FIG. 1 . The protective operation of the overcurrent reducing device 5c and the further circuit breaker 6c is also valid for the generator 1b. Therefore, the generator 1 b in this example should be equivalent to the object 1 in FIG. 1 , and the transformer 1 a should be equivalent to the device 3 in FIG. 1 . Thus, the overcurrent reducing device 5c and the further circuit breaker 6c in combination with the conventional circuit breaker 4b are able to protect the generator 1b from the flow of high currents from the direction of the transformer 1a.

Figure 19 also shows another overcurrent reducing device 5b and another circuit breaker 6b. Apparently, the overcurrent reducing devices 5a and 5b are respectively arranged on both sides of the transformer 1a. It is to be noted that further circuit breakers 6a and 6b are respectively positioned in the connection between the overcurrent reducing devices 5a and 5b and the transformer 1a. Another overcurrent reducing device 5b will protect the transformer 1a and prevent high current from flowing from the transformer to the generator 1b. Obviously, the circuit breaker 4b can be opened in any direction between the objects 1a and 1b to achieve the required safety function.

Figure 20 shows diagrammatically how the gap between electrodes 23o is energized by one or more lasers 25o in one or more points or regions 28o perpendicular to the axis of symmetry X between electrodes 23o. By using a number of different lasers 25o, high power can be supplied to the gap between the electrodes for plasma formation.

Figure 21b shows that a plurality of substantially parallel conductive pathways can be formed between electrodes 23p. The diagram of Fig. 21a is a top view of Fig. 21b, wherein, viewed from the side, the conductive channels are in a row. However, a plurality of conductive plasma channels can be arranged not only in rows but also in columns between the electrodes. The simultaneous presence of multiple conductive channels increases the conduction capacity of the switching device.

Figure 22 shows a variation in which the optical system 27q includes an axonite (refractive or diffractive) that divides radiation from a laser or the like into fractions and directs these different fractions of radiation to different Diffraction element (Kano hologram 36q). These kino holograms are distributed around one of the electrodes, that is, the electrode indicated by 23q in FIG. 22 . FIG. 23 shows a perspective view of the structure shown in FIG. 22 . As can be seen from Figure 23, the exemplary four kino holograms 36q are arranged around the electrode 23q, causing the radiant energy to converge by diffraction at a plurality of points or regions 28q present along the axis of symmetry of the electrode. Although it is also possible to use a continuous ring-shaped kino hologram, it is comparatively simpler and less expensive to implement using several discrete kino holograms 36q.

Semiconductor components such as thyristors, triacs, GTOs, IGBTs and other types of semiconductor components are very common in today's power systems and they are mainly used as electronic valves for controlling, i.e. delivering or blocking, the flow of current.

Although semiconductor components are highly efficient, exhibit good performance and are relatively cheap with the development of modern manufacturing methods, there are problems, mainly at very high voltage levels, and they require complex, bulky and costly processes method.

Through the process embodiments/methods presented in this specification, alternatives to semiconductor components are presented/explained, which provide a variety of simple designs using relatively few components, resulting in reduced costs. Furthermore, the process describes the design of electronic valve components, which ensure higher voltages than corresponding semiconductor components. Furthermore, devices based on the proposed process can be guaranteed to be almost independent of current and current density.

In the field of electric power, semiconductor elements have been widely used. This part of the power field is often referred to as power electronics. These applications are commonly referred to as converters. A converter is an operating unit that includes a semiconductor unit (electronic valve) and the necessary peripherals for changing one or more characteristic variables and parameters of the power system. In this way, the converter can vary voltage and current levels, frequency and number of phases. Electronic switches can also be considered converters.

Devices that interconnect DC and AC systems can also be considered converters (current diverters). When the current changes from AC to DC, the converter operates as a rectifier. Instead, the converter operates as an inverter when the current changes from DC to AC. An AC-AC converter is called a frequency converter, which converts one AC signal into another with any relationship between frequency, amplitude, phase and phase, and number of phases of voltage. A DC-DC converter converts one DC voltage into another DC voltage.

Electronic switches can be designed for DC or AC. It can be used to connect or disconnect equipment, or to control or check active or reactive power.

An electronic valve is controllable if it can switch/change from a cutoff state (off state) of high voltage and low current to a conduction state (on state) of low voltage and large current. The high efficiency of the electronic converter depends on this bistable function of the electronic valve. Electronic valves can be inherently stable, such as thyristors, or controllable for bistable operation, such as transistors.

Unfortunately the terminology is not completely uniform. IEC-compilations can be found in the "International ElectrotechnicalDictionary" and in Publ. 60050-551 IEV "Power Electronics". A large number of different semiconductor components can be completely or partially replaced by technology, which is the subject of this patent application. Two examples of the state of the art are: "Modern Power Electronics", Bose et al, IEEE Industrial Electronics Society, ISBN: 0-87942-282-3, and "Power Electronics-in Theory and Practice" by K. Thorborg, Chartwell-Bratt ”, ISBN: 0-86238-341-2. Mentioned below are the available semiconductor components referred to in these references:

- Thyristors, Diodes, Triacs, GTOs (Gate Off Thyristors), Bipolar Transistors (BJTs), PWM-Transistors, MOSFETs, IGBTs (Insulated Gate Bipolar Transistors), SITs (Static Induction Transistors), SITH (Static Induction Thyristor), MCT (MOS Controlled Transistor), etc.

I. When the current is made zero by an external device, the thyristor is turned off (transferred to cut-off state). In a self-rectifying alternator, the electronic valve is turned off by a shutdown circuit consisting of a capacitor, inductor and resistor. Thyristors are known as high voltage and power semiconductor components.

A thyristor as a semiconductor element has a bistable function. It consists of three pn transistors. It can be switched from off to on and vice versa in one or both directions. The most commonly used type of thyristor is the so-called "reverse blocking triode thyristor". A thyristor has three connections: anode, cathode and gate. In the absence of control pulses at the gate, the thyristor blocks current flow in both directions. When a positive voltage is applied on the anode and a negative voltage is applied on the cathode, the thyristor is in the off state and cuts off the voltage. If the applied voltage is of opposite polarity, the thyristor is in the off state in its opposite direction and reverses the cut-off voltage.

The leakage current in the reverse blocking and off states increases with thyristor size and temperature and can rise to several hundred mA for very large thyristors.

If the thyristor is triggered by applying a current or voltage pulse across the gate, of sufficient magnitude and duration, the thyristor switches from the off state to the on state, with current flowing in the forward direction from the anode to the cathode.

For normal values of on-state current, the voltage drop (voltage across the thyristor), the so-called on-state voltage, is typically 1-2 volts.

If the cut-off (forward) voltage exceeds the thyristor's specified breakdown voltage, it naturally changes from the off state to the on state. This self-triggering voltage can severely damage the thyristor, so such overshooting should be avoided.

In high voltage applications, where the system voltage substantially exceeds the maximum voltage a single thyristor element can withstand, several thyristors must be coupled in series or cascaded. In order to achieve adequate voltage distribution between the series-coupled thyristors, each thyristor must be equipped with its own RC circuit and resistor divider: the RC circuit acts as a transient voltage divider, and the resistors divide the cut-off voltage and the backward cut-off voltage respectively into Roughly the same voltage differential is given to each thyristor so that different thyristors do not have different leakage currents. Also, the resistor equalizes the voltage across the capacitor in the RC circuit. For thyristors in series, it is very important that the firing pulses of all thyristors occur simultaneously and have the same amplitude. Failure to fire simultaneously results in an overvoltage on the thyristor that was fired last and as a result current will flow through its RC circuit as well as the other thyristors. Often it is not only necessary to use thyristors that are already matched to each other, ie the selected thyristor exhibits properties compatible with other thyristors, especially in high frequency applications, a fact that complicates the structure and increases the cost.

The triac switching element is a triac, which means it has two cut-off directions, or forward. A triac is equivalent to two thyristors connected in antiparallel with a common gate. The triac switching element is initially in an off state. But it can be controlled to turn on by a negative pulse or a positive pulse on the control pole, which also enables bipolarity on the triac switching element. In most cases, the technological performance of a triac corresponds to that of a thyristor having the same dimensions and performance. The restrictive exception is caused by the fact that the triac switching element does not have the same short rise and fall times as a thyristor, nor does it have the same resistance to voltage transients (dU/dT). So, they are mostly used in voltage regulators with resistive loads and for grid frequencies where there are no rapid fluctuations in current and voltage. The fact that the triac switching element is two-state and requires only one cooling element and one firing pulse unit makes the structural design simple and relatively cheap, especially for low electrical power levels. For inherent reasons, light-triggered thyristors are good for high voltages, such as in HVDC systems and thyristor switching phase compensation systems. The main reason is the stringent requirements for electrical insulation. Furthermore, the risk of simultaneous start/conduction of the thyristors caused by noise coupling into their gates is reduced. The light pulses entering the thyristor are sent from the control unit at ground potential to the thyristor via the photoconductor. Since the photoconductor is formed of an insulating material, high voltage insulation can be achieved.

However, the light energy sent through the photoconductor is limited and dangerous, which is manifested in the fact that the thyristor system needs a long delay time to obtain the control signal, so the growth rate of the thyristor on-state current is relatively low, unless the thyristor is equipped with more A complex control structure that includes an amplification function for the signal that is ultimately applied to the gate of the thyristor. However, this construction means that the thyristors again become more sensitive to noise that may be coupled in via the gate and lead to inadvertent switching. Laser-triggered plasma switches can perform the same functions as multiple power semiconductors, and in some cases lead to greater process and economic advantages. In this patent application, it is specifically concerned with the function of a laser-triggered plasma switch as a triac switching element. Laser-triggered plasma switch, which is based on the instantaneous short-circuit current of the gas-filled electrode gap through the slender ionized conductive channel generated by the laser light, this switch mainly has the following benefits:

The distance between the electrodes included in the electrode system can be made large so that no greater problems arise with regard to the design and dimensioning of the external electrical insulation system. In this way, the structure can be simplified and the manufacturing cost can be reduced.

Another even greater benefit: There is in principle no limit to the maximum current that can be conducted by the plasma switch when it has been triggered into its conducting state by the laser. The conduction current is generated by the ionization channel created by the rapidly arcing laser light. The arc is not subject to any fundamental limitation in terms of the same maximum current flow, so the current density is not limited to the maximum value encountered by any semiconductor component. As the current rises, the arc maintains a favorable current density by expanding rapidly in terms of energy. This self-adjustment function is not available in semiconductor components.

A third fundamental benefit is that plasma switches can be designed for very high voltage levels and can be constructed from only a single component. Compared with a stacked semiconductor structure with the same function and for the same high voltage level, this switch not only greatly reduces the complexity of the structure itself, it does not have to include a large number of precisely connected semiconductor components, but also greatly reduces the need for these components. Timing needs between each other.

The substantial reduction in the number of active components increases reliability compared to what would be achieved using semiconductor components. In addition, the electrical loss is reduced, the equipment cost is reduced, and the complexity of the control system is reduced.

Another great benefit is that fast triggering can be achieved on the order of hundreds of microseconds, which increases the reliability of precise modulation.

Triac switching element function

Laser triggering in the elongated focal region provides for switching from the off state to the on state at any point in time. By virtue of its construction, the plasma switch according to the invention exhibits the same properties as a triac switching element, fully in combination with the electrode distance, the gas pressure, the gas composition and the partial pressure of the partial gas, and the overall geometry of the encapsulation vessel. When not triggered, the plasma switch is in an off non-conductive state. This cut-off characteristic is bi-directional, ie the element is electrically isolated from both polarities of voltage across the plasma switch. Once triggered, the plasma switch switches to the conduction state almost instantaneously, wherein as long as the current in the arc remains above a certain designed value and the electrode voltage of the plasma switch remains above a certain designed value, The plasma switch remains on. This conduction state is bidirectional: the plasma switching element can be triggered by a laser to make bipolar conduction. Figure 24 shows a switchgear with triggering by radiant energy. For example, a laser can be used for triggering. The switching device 5 is bipolar-triggerable, which gives a bidirectional function.

Triac function with open circuit

In the application, the function of the switchgear must have the possibility to open the switch, i.e. turn it into the open state. This is achieved by one of the following functions of the switch: (1) automatically self-extinguishing through its structure which fully combines electrode distance, air pressure, gas composition and partial pressure of the gas, or (2) giving the switch an external shutdown. open feature. In case (1), self-disconnection occurring after a time interval can be checked and determined by the structural design. Both DC and AC systems can implement this self-disconnecting function. In the case of AC it is simpler because the automatic self-disconnection is assisted by the current flowing through the conducting arc to change polarity and thus the current crosses zero. From the above, the conditions for effectively opening the plasma switch are established in a manner exactly equivalent to that used for opening a thyristor. Therefore, the stringent requirements on the structure of the plasma switch are reduced in the AC case. In case (2) the plasma switch can be provided with an external impedance element which ensures that the on-state current is reduced to zero so that the plasma switch is turned on and considered to be in the off-state. The same effect can be achieved with the operating environment in an AC system: just before the current zero-crossing changes polarity, the plasma switch self-opens due to insufficient ionization of the gas along the discharge channel. During this time, the current changes polarity and the new polarity reaches a voltage at which a fully ionized plasma channel conducts, enough of the plasma components to have time to recombine that the channel conductance is too low to support repeated conduction of the arc. level of communication. Therefore, re-emission is prevented and the plasma switch is turned off.

In contrast, the DC case has stricter requirements on the structure of the plasma switch. Through an accurate balanced selection of design parameters such as electrode distance and mainly the total air pressure, including the gas element and its partial air pressure, these requirements can be met, enabling self-disconnection to be achieved. Inherently alternative to allowing the current to commutate to another wire or element, the current in the plasma switch will go to zero while the plasma switch is open. However, the simplest technical solution is to complete the DC element with an external current limiting circuit element. Rougher but adequately stated, the solution is to incorporate in a suitable manner a plasma switch mechanical circuit breaker by which the plasma switch can be fully isolated from the grid under voltage.

unidirectional triac switching element function

The triac can conduct in both directions in its conducting state. As already described, plasma switches are bi-directional in nature since they do not have any kind of diode function. However, if the laser trigger is only active during one of the two polarities of the AC system, this function becomes effectively unidirectional, assuming that the preceding trigger has sufficiently low conductivity to prevent non-laser triggers after recombination. Natural triggering at the polarity of the triggering (half cycle of the AC voltage), the rest of the plasma may survive.

Fig. 25 shows a plasma switch functioning as a bidirectional triac switching element according to the present invention.

Bidirectional triac switching element function with two plasma switching elements

An alternative to the above-described embodiment is formed by two plasma switch elements with a break function (self-break or external break function) connected in anti-parallel between the upper and lower between potentials. According to the above description in this paper, the currently constructed two plasma switches connected to the AC system to form two unidirectional units are connected to the grid and connected to each other in such a way that the two switches conduct current in opposite directions. Since the plasma switch is inherently bi-directional, this means that both elements are designed to be laser-triggered during their respective polarity, ie during a half cycle of their own AC voltage. The two plasma switches can be triggered by one or the same laser, which requires the optical system to be equipped with a luminous flux control shutter. The laser is fired at least twice per cycle, once every half cycle, and in one embodiment, the shutter is designed such that the entire emitted laser volume is alternately directed to one or the other of the two plasma switching elements. Such a luminous flux guiding shutter can be constituted by, for example, a rotating high-reflection mirror, which guides laser light to each of the two optical channels leading to the plasma switch through reflection from its two ends. Another embodiment is to split the laser light into two channels with an equal amount of laser effect in both channels. Each channel leads to one of two plasma switches. Luminous flux control shutters are installed in each channel, said shutters ensuring that only one of the two plasma switching elements is exposed to the triggering laser light by means of a controllable action during each triggering operation. Both plasma switching elements can also be triggered reliably by a laser for each plasma switching element, the operation of the lasers being checked, synchronized and controlled by an external electronics unit. Figures 26, 27 and 28 only show the possibility for forming the function of a bidirectional triac switching element.

Of course, the same bidirectionality can also be achieved with a coupling of two corresponding plasma switching elements, which does not exhibit a self-disconnecting function or is not provided with an external device for disconnecting.

Thyristor function

As described in the prior art, the thyristor has an off state, the so-called off state, for voltage and current in both directions. When a thyristor is fired at its gate, it assumes the so-called conducting state, in which current flows in the forward direction of the thyristor rather than in the reverse direction. The best way to achieve the same function by a laser-triggered plasma switch means that the laser-triggered plasma switch is coupled in series with one or more diode functions, which may be of semiconductor type. The number of diodes is determined entirely by the maximum voltage that must be put across them in the application. Two different possibilities for the positioning of the diode relative to the plasma switch are: forward towards the plasma switch and forward towards the plasma switch. Thus, two different thyristor functions can be realized, wherein a thyristor unit consisting of a plasma switch connected in series with a plurality of diodes results in different directivity and polarity. Preferably, the diodes contained in such a composite are provided with their respective RC networks or other more general impedance networks and resistor dividers in order to achieve equal voltage distribution. Thus, the diodes are not exposed to different voltage levels that may exceed their specified voltage tolerance. Figures 29a-d illustrate that different directivities or polarities can be achieved with one or more diodes in a plasma switch according to the present invention.

As an example, how the plasma switch described above can be used in the form of a triac function or a thyristor function is explained with reference to FIGS. 30 and 31 . The circuit shown in the figure acts as a transfer switch. The function of Fig. 30 is as follows: the upper conductor _L1 is connected to AC voltage, while the lower conductor _L2 is connected to ground or lower potential. In the event that neither of the plasma switches PS ₁ and PS ₂ is triggered, no current will flow through the circuit as long as the voltage in the upper conductor L ₁ is positive. But if plasma switch _PS2 is triggered to close, current will flow from upper conductor _L1 through diode D1 through _PS2 to ground. As long as the voltage has positive polarity, current flows. After the polarity on the upper conductor _L1 becomes negative, the current flows in the opposite direction. But this current only flows after PS ₁ has been triggered, from the upper conductor via diode D ₂ and PS ₁ to the lower conductor and then back to the upper conductor via diode D ₂ and PS ₁ . Since the voltage drop across diode _D2 may be lower than the voltage drop across _PS2 in the direction from _L2 to _L1 , the current preferably flows through _D2 rather than _PS2 after said polarity change. PS ₂ will not be restarted in the wrong direction, so it is at rest for the half cycle it is currently in negative polarity.

In the circuit just described, the plasma switch is used in the function of a unipolar triac switching element, ie in the function of a normal thyristor. The circuit in Fig. 31 is provided with two other diodes connected in series with the plasma switch respectively, which fully guarantees that the current does not mistakenly try to turn off the plasma switch after a polarity change. Thus, as an example of an external device, an additional diode prevents the switch from being activated again ("back firing").

From the description given above it is evident that in the case of laser triggering of the plasma switch as the starting point, more technical functions than those described herein can be realized.

Fig. 32 diagrammatically shows a switchgear 5r connected in series in line 2r between grid 3r and object 1r as previously discussed. The switching device 5r comprises a switching device 1Or having the aforementioned characteristics, ie the switching device 1Or is adapted to bring the electrode gap into conductive closure by means of radiant energy. But it is not shown in more detail in FIG. 32 . It can be seen from FIG. 32 that the switching device 5r has a purely switching function, ie, when in the conducting state, the feeding of the object 1r or possibly in the opposite direction occurs via the switching device 10r. When required, the switching device 1Or will inhibit the current flow relatively quickly, for example to protect the object 1r or possibly even the grid 3r from the current from the object 1d. In order to achieve disconnection in the AC connection by means of the switching device 10r, it is sufficient for the device supplying energy to the electrode gap to terminate this energy supply. When the following channel crosses zero, the arc in the switching device 10r is extinguished, so that the current supply is interrupted. In DC applications, it may be necessary to support the disconnect function by taking measures to reduce or eliminate the voltage difference across the switching device 1Or. This way consists in the switch 31 being coupled in parallel to the switching device 1Or. Closing of the switch 31 means that the current bypasses through the switching device 10r, a fact which causes the arc in the switching device 10r to be extinguished. If this measure is not sufficient, additional switches can be provided in the line 2r on both sides of the switching device 10d in order to completely disconnect the switching device 10r from the line 2r.

The purpose of Fig. 32 is to show that the switching device 5r according to the invention can have a general switching application, where it is only a matter of protecting different devices, and more generally of switching power supplies under different load conditions.

It should be pointed out that the description made herein is only illustrative of the idea underlying the invention. Therefore, those skilled in the art can make detailed modifications to the present invention without departing from the scope of the present invention. As an example, it may be provided according to the invention that it is not necessary to use a laser to provide ionization/plasma forming energy to the gap 24 . As long as the requirements of speed and reliability are met according to the invention, other radiation sources such as electron guns or other energy supply methods can also be used. It should be observed that, according to the invention, the switching device 10 can also protect electrical objects from faults related to overcurrents in other operating situations than those shown in FIGS. 1 , 3 and 19, wherein the device according to the invention The setting is to reduce the negative impact of the relatively low opening time of the circuit breaker 4 . In this way, the switching device according to the invention does not necessarily require operation in relation to such a circuit breaker 4 . The invention is applicable to both AC and DC.

Claims (51)

1. Equipment for switching power supplies, comprising at least one electrical switching device (5), characterized in that the switching device (5) comprises at least one switching device (10), which comprises an electrode gap (24), which is Switchable between an insulating state and a conductive state, the means (25) for causing or at least activating the electrode gap or at least part of the electrode gap to be conductive, and the means for causing or at least activating the electrode gap to be conductive (25 ) is adapted to energize the electrode gap in the form of radiant energy such that the gap or at least part of the gap forms a plasma. 2. Apparatus according to the preceding claim, characterized in that said means (25) for causing or at least initiating the electrical conductivity of the electrode gap or part of the electrode gap comprise at least one laser (25). 3. Apparatus according to any one of the preceding claims, characterized in that the switching means (10) is formed in such a way that between its electrodes (23) it exhibits an electric field in its insulated state which excites or generates between the electrodes Electrical arcing that causes or initiates electrical conductivity across the electrode gap. 4. Device according to claim 3, characterized in that the electric field strength of the electric field in the insulating state of the electrode gap (24) is substantially smaller than that at which natural breakdown occurs. 5. The device according to claim 3 or 4, characterized in that the electric field intensity of the electric field in the electrode gap (24) insulation state is not greater than 30% of the electric field intensity at which natural breakdown occurs, and is not more than 20% more appropriate, Preferably no more than 10%. 6. The device according to any one of claims 3-5, characterized in that the electric field strength of the electric field in the electrode gap (24) insulation state is at least 0.1% of the electric field strength at which natural breakdown occurs, at least 1 % is more appropriate, preferably at least 5%. 7. Apparatus according to any one of the preceding claims, characterized in that said means (25) which cause or at least initiate the conduction of the electrode gap (24) are arranged to provide The radiant energy, at this electric field strength, can trigger the electrode gap to become conductive. 8. Apparatus according to any one of the preceding claims, characterized in that said means (25) for causing or at least enabling the electrode gap (24) to become conductive are arranged to supply radiant energy to the electrode gap (24) in such a way : Minimize the time delay between the arrival of radiant energy and the ability to form an electrode gap to conduct electricity. 9. Apparatus according to any preceding claim, characterized in that the switching means (10) and means (25) which cause or at least initiate the conductivity of the electrode gap are arranged such that the establishment of conductivity in the electrode gap is substantially does not depend on the electric field strength occurring between the electrodes of the switching device in the insulated state. 10. Apparatus according to any preceding claim, characterized in that the switching means (25) for supplying trigger energy to the electrode gap are arranged to apply radiant energy to at least one of the electrodes (23) or at least Applied in the vicinity of at least one of the electrodes (23). 11. Apparatus according to any one of the preceding claims, characterized in that the switching means (25) for supplying trigger energy to the electrode gap are arranged in order to position the radiant energy in the gap (24) between the electrodes (23) A point or area. 12. Apparatus according to any preceding claim, characterized in that the means (25, 27) for supplying trigger energy to the electrode gap are arranged to apply radiant energy to two or more points or area (28). 13. Apparatus according to claim 12, wherein the means for providing trigger energy to the electrode gap is arranged to locate two or more points or areas of radiant energy along a line extending between the electrodes, The lines correspond to the extension of the desired conductive path between the electrodes. 14. Apparatus according to any preceding claim, characterized in that the means (25) for supplying trigger energy to the electrode gap are arranged to apply radiant energy to one or more elongate regions (28i, k, m , n), the longitudinal axis of which extends substantially in the direction of the desired conductive path between the electrodes. 15. Apparatus according to claim 14, characterized in that the means (27) for supplying trigger energy to the electrode gap are adapted to form the elongate focal zone in the shape of a cylinder. 16. Apparatus according to claim 14 or 15, characterized in that the means for providing trigger energy to the electrode gap is adapted to form the elongated region such that it bridges the entire or substantially the entire space between the electrodes. 17. The device according to claim 14 or 15, characterized in that the means (27) for supplying trigger energy to the electrode gap is adapted to form two or more elongated focal zones (28) within the electrode gap, said The focal regions are positioned longitudinally behind each other along the desired conductive path between the electrodes. 18. Apparatus according to any one of claims 1 and 10, characterized in that the means for providing trigger energy to the electrode gap is adapted to apply radiant energy to at least one of the electrodes or between the electrodes. 19. Apparatus according to any one of claims 10-18, characterized in that at least one of the electrodes in the electrode gap has an opening through which the means (25) for providing trigger energy guides the radiant energy . 20. Apparatus according to claims 15 and 19, characterized in that the means (27) for supplying trigger energy to the electrode gap is located in the cylindrical radiant energy area (28) near the electrode with the opening (29) so that the cylindrical The axis of the shaped radiant energy region is substantially concentric with the axis of the opening in the electrode. 21. Device according to any one of the preceding claims, characterized in that auxiliary electrodes (31, 31d) are arranged on the gap between the electrodes for balancing the electric field and/or actively participating in the triggering process, by means of which auxiliary electrodes Capable of emitting free charges when exposed to radiant energy. 22. Apparatus according to any one of claims 10-21, characterized in that the means for supplying trigger energy to the electrode gap comprises a system for controlling the energy of electromagnetic waves. 23. Device according to claim 22, characterized in that the control system comprises at least one refractive, reflective and/or diffractive element. 24. Apparatus according to claim 23, characterized in that the element is formed of axonite. 25. Device according to claim 24, characterized in that the element is formed by a kino hologram. 26. Device according to claim 23, characterized in that the element comprises an optical fiber (38). 27. Apparatus according to any one of claims 23-26, characterized in that the control system (27f, h) is located radially outside the electrodes, adapted to introduce the beam of radiation into the gap between the electrodes. 28. Apparatus according to any one of claims 23-27, characterized in that the control system (27g) divides the laser pulses into a ring structure around one of the electrodes. 29. Apparatus according to any preceding claim, characterized in that at least one overvoltage diverter (22) is connected in parallel to the switching device (10). 30. Apparatus according to any preceding claim, wherein the electrical object (1) is connected to a grid (3) or another device comprised in a power plant, said device comprising a line between the object and the grid/device Switchgear (4) on (2), characterized in that the switchgear (10) is connected to the line (2) between the object (1) and the switchgear (4), and that the switchgear (10) is actuatable , for diverting the overcurrent in a time interval substantially shorter than the opening time of the switching device (4). 31. Arrangement according to claim 30, characterized in that the switchgear (4) is constituted by a circuit breaker. 32. The device according to claim 21 or 31, characterized in that it comprises a further circuit breaker (6) arranged on the line between the switchgear (4) and the object, said further circuit breaker being arranged at the switchgear between the device (10) and the object (1), adapted to break voltages and currents lower than those of the switching device (4), and thus capable of being performed with a shorter breaking time than the switching device, when flowing to or from the object (1) The other circuit breaker is opened when an overcurrent has passed through the switchgear (10) but earlier than the switchgear has been reduced. 33. The device according to claim 32, characterized in that it comprises a control element (14) connected to the detection means (11-13) and to another circuit breaker (6), in order that when the flow direction is indicated by the detection means Or when the overcurrent leaving the object (1) is lower than a predetermined level, the actuation of another circuit breaker is completed for opening purpose. 34. Apparatus according to any one of claims 32-33, characterized in that the further circuit breaker (6) comprises a switch (15) on which a parallel line with one or more elements (18) is coupled (18) for avoiding arcing caused by separation of the contacts of the switch (15) by causing the parallel line (17) to receive conduction current from the contacts. 35. The device according to claim 34, characterized in that one or more elements (18) on the parallel line (17) can be controlled to be closed and conducted via the control element (14). 36. Apparatus according to claim 34 or 35, characterized in that said one or more elements (18) are constituted by controllable semiconductor elements. 37. Apparatus according to any one of claims 34-36, characterized in that said one or more elements (18) are equipped with at least one overpressure brake (30). 38. Apparatus according to any one of claims 34-37, characterized in that an isolating switch (20) for galvanic separation is arranged in series with said one or more elements (18). 39. Apparatus according to claim 38, characterized in that the isolating switch (20) is coupled to the control element (14) so that when the switch (15) has been closed in a controlled manner and the one or more elements (18) have After being in the state of disconnecting the parallel line (17), the isolating switch is thus controlled to be opened. 40. Device according to any one of the preceding claims, characterized in that the protected object (1) is constituted by an electric device with a magnetic circuit. 41. Apparatus according to claim 40, characterized in that said object is constituted by a generator, a transformer or an electric motor. 42. Apparatus according to any one of claims 1-41, characterized in that said object is constituted by a power line such as a cable. 43. Apparatus according to any preceding claim, characterized in that two switching means (10) are arranged on both sides of the object to protect the same object from both sides. 44. The device according to claim 1, characterized in that it comprises a control element (14) connected to the switching means (10) and the overcurrent state detection means (11-13), the control element (14) It is arranged to control the closing of the switching means based on the information from the overcurrent condition detection means when protection is required. 45. The device according to claim 44 and one or more of claims 34, 36 and 40, characterized in that, on the basis of information from the overcurrent state detection means (11-13), the same control element ( 14) Control switchgear (10) and another circuit breaker (6). 46. Use of an apparatus according to any preceding claim for protecting an object from the effects of an overcurrent related fault. 47. Apparatus according to any preceding claim, wherein the means for providing trigger energy to the electrode gap focuses radiant energy in a plurality of substantially parallel elongated focal regions, the longitudinal axes of which lie substantially along the gap between the electrodes. Orientation of the conductive path (Figure 21). 48. Apparatus according to any preceding claim, characterized in that, in addition to supplementary diodes or other elements, one or more switching means (10) are provided to form a switch or converter function. 49. The apparatus of claim 48, wherein the function is a triac and a thyristor function. 50. A method in a power plant for protecting an electrical object (1) from faults related to overcurrent, characterized in that, when an overcurrent state has been detected by means of detection means (11-13), by switching means ( 10) Complete the overcurrent diversion, in order to divert the overcurrent to the ground (8) or another element with a relatively low potential, the switch device (10) provided is closed by triggering the electrode gap (24) overcurrent diversion, by Radiant energy is supplied to the electrode gap by means of trigger means (25) to render conductivity in the switch. 51. The arrangement according to claim 50, characterized in that a further circuit breaker (6) is arranged between the switchgear (4) and the object (1) and between the switchgear (10) and the object (1) On the line (2), said further circuit breaker (6) is opened after the excess current flowing to or from the object (1) has been reduced by the switching device (10).

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