MXPA99005699A - 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

SWITCHING DEVICE THAT INCLUDES DOWNLOADER TO SWITCH ELECTRICAL ENERGY FIELD OF THE INVENTION AND PREVIOUS TECHNIQUE This invention relates to a device according to the character part i-z of the appended claim 1. The device according to the invention can be used in any connection for switching purposes. Particularly preferred are the applications where it is to be switched. Actually, high voltage connections and electrical power transmission applications are involved. A preferred, though not restrictive, application of the device according to the invention is to protect, in a power plant, an electrical object from the consequences of the faults, mainly insofar as the current is involved but also the voltage. In addition, the invention comprises a method for the protection of the object. The electrical object in question may be of an arbitrary nature insofar as it is contained in a network of electrical energy and requires protection against overcurrents in connection with failures, that is, short-circuit currents in practice. As an example, it can be mentioned that the object can be formed by an electrical device having a magnetic circuit, for example a generator, transformer or motor. Other objects may also be in question, for example, energy lines and cables, switching equipment, e t c. The present invention is intended to be applied in relation to medium and high voltages. According to the IEC standard, the mean voltage refers to 1-72.5 kV considering that the high voltage is > 72.5 kV. Therefore, transmission and distribution levels are included. In prior art power plants of this nature, one has been required, for the protection of the object in question, to a conventional circuit breaker (switching device) of such design as to provide galvanic separation in the interruption. Since this circuit breaker can be designed to be able to separate very high currents and voltages, it would obtain a comparative volume design with large inertia, which is reflected in a comparatively long interruption time. It is pointed out that the predominant overcurrent is the short circuit current that occurs in relation to the protected object, for example as a consequence of faults in the electrical insulation systems of the protected object. Such failure means indicate that the fault current (short circuit current) of the external equipment / network will tend to flow through the arc. The result can be a very large interruption. It can be mentioned that for the Swedish energy network, the dimensioning of the short circuit current / fault current is 63 kA. Actually, the short circuit current can accumulate up to 40-50 k. A problem with such circuit interruption is the long interruption time thereof. The dimensioning interruption time (IEC standard) to completely achieve the interruption is 150 milliseconds (ms). It is associated with difficulties to reduce this interruption time to less than 50-130 ms depending on the real case. The consequence of this is that when there is a fault in the protected object, very high current will flow through it during all the time required to operate the interrupt switch. During this time, the entire fault current of the external power network, involves a considerable load on the protected object. In order to avoid damage and complete interruption with respect to the protected object, according to the prior art, the object has to be constructed in such a way that it manages, without appreciable damage, when subjected to the short circuit current / fault current. during the interruption time of the circuit breaker. At this point outside the short circuit current (fault current) in the protected object may be composed of the object's own contribution to the fault current and the addition of current emanating from the network / equipment. The own contribution of the object to the fault current is not influenced by the operation of the switch, although the contribution to the fault current from the network / equipment depends on the operation of the switch. The requirement to construct the protected object in a manner that resists a short-circuit current at the failure rate for a considerable period represents substantial disadvantages in the form of the most expensive design and reduced efficiency.

As noted above, the invention is not restricted only to protection applications. In other switching situations, it is a disadvantage to have to resort to rather expensive and bulky switching devices when high power is involved, for example, banks of semiconductor components, in order to handle the proposed switching function. The current semiconductor component, which preferably occurs in silicon although other materials may be involved, has for practical reasons a restriction for the maximum electrical field strength that the component can withstand before an electrical break in the semiconductor material occurs. This implies immediately corresponding restrictions of the maximum electrical voltage that the component can withstand. In particular, in high-voltage connections, it is forced to couple in series (stacking) a large number of semiconductor components in such a way that none of the components contained in the battery is subjected to a voltage that is above a safe level for the component. In addition, complications can occur in the design of the semiconductor component since the semiconductor material itself resists without being subjected to, for example compared to atmospheric air, a very high electric field resistance. However, the same would not be valid for the insulating material that must necessarily be present between those electrodes externally of the semiconductor material between which the high voltage is placed. This also involves a restriction: In the design of a semiconductor component for high voltage use a careful balance must be made between the resistance of the electric field between the semiconductor material and the electrical resistance in the circulating insulating medium. In various applications in electric power plants, the components included in them are subject not only to high electrical voltages, but also to large electric currents. When a current passes through a component that has a certain resistance, considerable amounts of thermal energy (the so-called Joule thermal energy) is proportional to the resistance in question and to the square of the current. Since each semiconductor component has a small but negligible resistance, the maximum current that the component battery can withstand is restricted. If very large currents are to be carried by the semiconductor components, one must force to transport the current through several identical parallel current paths. The number of semiconductor components increases, consequently, multiplied. At high voltages and large currents, a large number of semiconductor components must be used. This results immediately in lower reliability, since all the components must work in order to form the power plant, such as for example an HVDC valve to be in operation. The fact that a large number of semiconductor components are - stacked, means that they must be controlled by very high precision in time. The erroneous "synchronization" could for example result in too high a voltage applied to an individual component causing a certain failure and the accessory removal of the entire plant operation. The problem of "synchronization" is increased, of course, if a plurality of--, parallel current paths must be provided and synchronized.

OBJECT OF THE INVENTION The main object of the present invention is to provide a switching device more suitable for the switching of high electrical energy in a fast way and at a comparatively lower cost than the switching devices used today. A secondary object of the present invention is to design ways to design the device and the method so as to achieve the best protection for arbitrary objects and, consequently, a reduced load on them, a fact that means that the objects themselves should not have been designed to withstand a maximum of short-circuit currents for short periods of time.

BRIEF DESCRIPTION OF THE INVENTION According to the invention, the arrangement of the invention is designed according to the characterization part of claim 1. Since the discharger of the switching means is brought into an electrically conductive state by supplying power directly to the suitable arrester in the form of radiation in order to establish the ionization / plasma in the arrester, conditions that are created during a very fast operation of the switching arrangement according to the invention. The ionization / plasma in the pro duce / initiation discharger to an electrically conductive plasma conduction channel that has a very high conductivity so that very high currents can be transported and more specifically to last relatively long periods of time without negative effects, which it is in direct contrast to the conventional semiconductor technique. According to the invention, the aforementioned secondary object is achieved in that the switching arrangement in the form of an overcurrent reducing arrangement, which is operable for overcurrent reduction with the assistance of an overcurrent condition detecting arrangement, which is connected to the electric power plant to protect the object. The switching arrangement may, in accordance with a preferred embodiment, form an overcurrent shunt to derive the structors to ground or otherwise, another unit having a relatively low potential. Therefore, the invention is based on the principle, while the protection aspect is involved, in using a fast-acting switching arrangement, hereinafter referred to as switching means, which without affecting the -interruption of the overcooking, reduces the same to a degree such that the object under protection will be subjected to substantially reduced stresses and consequently to a lesser amount of damage. The reduction of the reduced fault means, therefore, that the total energy injection within the protected object will be substantially less than in the absence of the switching means according to the invention. The solution according to the invention is based on switching means which involve a particularly advantageous satisfaction of the demands that can be established in order to achieve a satisfactory protection function. Therefore, a very fast actuation can be achieved by means of the switching means so that the occurrence of overcurrent related to the faults with a very small delay of time that will be derived by means of the switching means as soon as the arrester has been adopted. an electrically conductive condition. It is pointed out that the term "actuation" in this aspect means bringing the switching means into an electrically conductive state. By means of the arrangement of the switching means, the switching means can be easily sized to be able to conduct very large amounts. In order to obtain a satisfactory, namely desirable, protection function, the current conducting channel, which is established through the switching means, has a very low resistance. This means that the enormously possible voltage release of the object, which is protected from the fault currents. Furthermore, the switching means according to claim 1 can, with less effort, be forced to operate with a particular high drive safety. The actuation therefore in order to derive the occurrence of fault currents as soon as possible, must not fail in a critical situation. The switching means according to the invention also give rise to the possibility of sizing in order to achieve a very high electrical resistance in a non-activated line. The probability of a spontaneous interruption is therefore minimal. It is especially preferred to use therefore, at least one laser beam for actuation. Preferred developments with respect to the means for supplying radiant energy to the unloader are defined in the appended claims. According to the modality, the radiant energy supplied to the discharger in two or more points or areas for the purpose of achieving the greatest possible certainty with respect to bringing the discharger to assume an electrically conductive state. According to an alternative, the power supply means may be designed to supply radiant energy along an elongated area, a conduction path that is intended between the electrodes. According to an optimum embodiment, this elongated area can, completely or substantially completely, connect the space between the electrodes. Although it is possible, in a case with two or more areas or points for radiation supply, those areas or points are applied successively corresponding to the propagation with respect to the electric conduction path between the electrodes in such a way that the points or areas are applied successively with a time delay, that is, according to the invention, normally preferred to apply those points or areas substantially simultaneously to make the conductive discharger momentarily. In addition, the means for supplying drive power can, according to the invention, be adapted to apply radiant energy in a volume having a tubular shape. This is particularly preferable when the electrodes comprise an opening, through which radiant energy is supplied, and when the radiant energy supplied in a tubular volume is applied relatively close to the electrode provided with an aperture.According to an alternative embodiment, the power supply means may be designed to supply the radiant energy in a plurality of substantially parallel elongated areas extending between the electrodes.

The radiant energy can also be supplied to the electrode space transversely with respect to an axis of the electrode in one or more points located between the electrodes. The switching arrangement according to the invention can advantageously be used to realize various switching functionalities conventionally obtainable by means of the semiconductor technique. In other words, the electrical components can be constructed by means of the switching arrangement according to the invention in a suitable number, such as electrical components having properties similar to those known per se within the present semiconductor technique . The additional and characteristic advantages of the invention, particularly with respect to the method according to the invention, appear in the following description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the accompanying drawings, a more specific description of an example of embodiment of the invention follows below. In the drawings: Figure 1 is a purely diagrammatic view illustrating the basic aspect behind the solution according to the invention, Figures 2a-2d are diagrams illustrating in a diagrammatic manner and in a comparative manner the developments of fault current and the development of energy with and without the device according to the invention; Figure 3 is a diagrammatic view illustrating a conceivable design of a device according to the invention; Figure 4 is a diagrammatic detailed view illustrating a possible design of the overcurrent reduction arrangement, Figures 5-7 are views similar to the Figure 4 of different variants, Figure 8 is a diagrammatic view illustrating an optical system for power supply to the electrode space; Figure 9 is a view illustrating an alternative optical system positioned on the side of one of the electrodes; Figure 10 is a further alternative for an optical system positioned to supply the radiant energy around one of the electrodes and coaxial relative thereto without the need for an opening in one of the electrodes; Figure 11 is a view of an optical system based on the use of optical fibers; Figure 12 is a prinsipal view illustrating the refraction of light emanating from a point source by means of a refractive axicon; Figure 13 is a view similar to Figure 16 although it shows the action of the axicon on a collimated laser beam; Figure 14 is a view illustrating the function of a refractive axicon for generating an elongated focal area between the electrodes; Figure 15 is a diagram illustrating the energy density along the focal area in Figure 18; Figure 16 is a view similar to Figure 18, although it illustrates the use of an optical diffraction component; Figure 17 is a view illustrating the approach in an elongated area by means of a reflective axicon; Figure 18 is a view illustrating the use of a diffractive axicon (a cynoform) capable of generating focal areas having different geometric shapes; Figure 19 is a diagrammatic view illustrating the device according to the invention applied in an electric power plant comprising a generator, a transformer, and an electric power network coupled thereto; Figure 20 is a view illustrating how energy can be delivered to the electrode space transversely relative to a common axis of the electrodes, Figure 20a illustrating the radiant energy that is delivered at a single point or area considering that such points or areas are presented in Figure 20b; Figures 21a and b are views illustrating how the radiant energy can be delivered so that several substantially parallel and electrical conductive channels are formed between the electrodes; Figure 22 is a side view illustrating an embodiment similar to one in figure 10, which is evident from Figure 23 that a plurality of individual cords (diffractive optical elements) are placed around one of the ect ects, Figure 24 illustrates in diagrammatic form that the commutating arrangement according to the invention can satisfy an idimensional thyristor function, Fig. 25 is a view illustrating a unidirectional thyristor function, Figs. 26-28 are three different examples of how the bidi tional thyristor function can be achieved by means of switching arrangements in accordance With the invention, each comprising two switching means, Figures 29a-d are views illustrating that the switching arrangement according to the invention by series that are coupled with one or more diode functionalities may be provided to function as a thyristor, Figures 30 and 31 are examples of how the switching arrangements according to the invention n can be used with a triac function or a thyristor function, and Figure 32 is a diagrammatic view of the switching arrangement according to the invention in a series switching function.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES An electric power plant comprising a protected object 1, is shown in Figure 1. This object could for example consist of a generator. This object is connected, via a line 2, to an external distribution network 3. Instead of such a network, the annotated unit 3 could be formed by some other equipment contained in the electric power plant. The electrical power plant involved is conceived to be of such a nature that this is the same object 1 that is mainly intended to be protected against the fault currents of the network / equipment 3 when a fault occurs in the object 1 that gives rise to a fault current from the network / equipment 3 to object 1 so that the fault current will flow through the object. Such failure may consist of a short circuit that has been formed in object 1. A short circuit in a conduction path, which is not intended, between two or more points. The short circuit may, for example, consist of a bow. This short circuit and the resulting violent current flow can cause considerable damage and even a total breakdown of object 1.

It has already been pointed out that at least some types of protected electrical objects 1, the short circuit currents / currents of damaging faults for the object in question can flow from the protected object to the network / equipment 3. Within the The scope of the invention is intended to be used for protection purposes not only for protection of the object from the fault currents emanating from the exterior flowing to the object but also from the internal fault currents in the object flowing in. the opposite direction. This will be described in more detail below. In the following, the designation 3, to simplify the description, will always be mentioned as consisting of an external electric power network. However, it must be remembered that some other equipment may be involved in place of such a network, while the equipment causes violet currents to flow through object 1 when there is a fault. A conventional circuit breaker 4 is placed on line 2 between object 1 and network 3. This switch comprises at least one sensor of its own to detect circumstances indicative of the fact that there is an overcurrent flowing on line 2. Circumstances can be either 1 or 2, but also another indication that a fault is within reach. For example, the sensor may be an arc sensor or a sensor that records the sound of the short circuit, etc. When the sensor indicates that the overcurrent has reached a certain level, the switch 4 is operated to interrupt the connection between the object 1 and the network 3. The circuit breaker 4 must, however, separate the short circuit current / Corri ent of total failure. Therefore, the switch must be designed to meet the highest requirements, which in practice mean that it will operate relatively slowly. Figure 2a illustrates a current diagram that when a fault, for example, a short circuit in object 1 occurs in time tfau? T / the fault current in line number 2 in Figure 1 quickly assumes magnitude ii. This fault current ii is interrupted by means of the switch 4 in you, which is at least 150 ms after tfau - Figure 2d illustrates the diagram i2t, and consequently, the energy developed in the protected object 1 as a consequence of the short circuit in it. The energy injection into the object that occurs as a consequence of the short-circuit current is, consequently, represented by the total area of the outer rectangle in Figure 2d. It is in this connection that it is pointed out that the fault current in Figures 2a-c and currents 2d represent the envelope of the extreme value. Only one polarity has been plotted in the diagram for the purpose of simplicity. The switch 4 is such a design that establishes the galvanic separation by the separation of metallic contacts. In consecuense, the switch 4 comprises a rule, the auxiliary equipment required for the extinction of the arc. According to the invention, the line 2 between the object 1 and the switching device 4 is connected to an arrangement generally designated as 5. This arrangement can be generally designed as a switching arrangement. In the application shown, the switching arrangement has the function of arrangement that reduces the over-current to the apparatus. The arrangement is operable to reduce overcurrent with the help of the overcurrent condition detection arrangement within a period substantially less than the interruption time of the switch 4. This arrangement 5 is, consequently designed so that it does not have to establish any galvanic separation. Therefore, the conditions are created to very quickly establish a current reduction without having to achieve any total elimination of the current flowing from the network 3 to the protected object 1. Figure 2b illustrates in contrast to the case according to the Figure 2a that the overcurrent reduction arrangement 5 according to the invention is activated at the occurrence of a short-circuit current in the time tfau? T for the reduction of overcurrent up to the level i2 at time t2. The time interval t £ aiut-t2 thus represents the reaction time of the overcurrent reduction arrangement 5. Since the task of arrangement 5 is not to interrupt but only to reduce the fault current, the arrangement it can be forced to react extremely quickly, which will be described below. As an example, it may be mentioned "that the current reduction from level ii to level i2 is destined to be achieved one or a few more after the unacceptable overcurrent conditions have been detected, ie to meet the current reduction in a time less than 1 ms, and preferably more quickly than 1 micro second As shown in Figure 1, the device comprises an additional switch annotated generally as 6 and placed on line 2 between switch 4 and the object 1. This additional switch is designed to interrupt a low voltage and the current that the circuit 4 and can, as a consequence of the same, be designed to operate with interruption times less than those of the switch. interrupt not only after the overcurrent from the network 3 to the object 1 that has been reduced by means of the reductive arrangement of the overcurrent. 5, but substantially before the switch 4. From what has been established, it seems that the additional switch 6 must be coupled to the line 2 in such a way that it is the reduced current by means of the overcurrent reduction arrangement 5, which it will flow through the additional switch and that, consequently, it will be interrupted by means of it. Figure 2b illustrates the action of the additional switch 6. This switch is, more specifically, designed for interruption in time t3, which means that the duration of the current i2 reduced by means of the overcurrent reducing arrangement 5 is substantially delimited, namely until the time period t2-t3. The consequence is that the injection of energy into the protected object 1 caused by a fault current from the network 3 is represented by the surface marked with oblique lines in Figure 2d. It seems that a drastic reduction of the energy injection was achieved. In this regard, it is pointed out that according to a specific model, the energy increases with the square of the current, a reduction to a half of the current, the reduction of energy to a fourth. This is illustrated in Figure 2c of how the fault current will flow through the arrangement 5. The sizing and arrangement 5 and the additional switch 6 is designed to be carried out so that the arrangement 5 reduces the fault current and the voltage to be interrupted by means of the additional switch to substantially the lowest levels. A realistic interruption time for additional switch 6 is 1 ms. Nevertheless, the sizing should be done so that the switch 6 is forced to interrupt until after the arrangement 5 has reduced the current flowing through the switch 6 to at least a substantial degree. It is illustrated in more detail in Figure 3 how the device can be realized. It is noted that the invention is applicable in direct current connections (also HVDC = High Voltage Direct Current) and alternating current. In the latter case, the denoted line 2 can be considered to form one of the phases in a multiple phase alternating current system. However, it must be remembered that the device according to the invention can be realized in such a way that all the phases are subjected to the protection function according to the invention in case of a detected fault or that only that phase or phases where the current failure occurs if subjected to current reduction.

From Figure 3 it appears that the generally designated overcurrent reducing arrangement 5 comprises an overcurrent shunt 7 to derive the overcurrent to ground 8 or otherwise to another unit having a lower potential than the network 3. Therefore, the overcurrent diverter can be considered to form a current divider that rapidly establishes a short circuit to ground or otherwise a lower potential 8 for the purpose of deriving at least a substantial portion of the current flowing on line 2 of so that the current does not reach the object 1 to be protected. If there is a serious fault in the object 1, for example a short circuit, which is of the same magnitude as the short circuit that the overcurrent diverter 7 is capable of establishing, it can be said speaking in general terms that a reduction of a mean of the current flowing through the object 1 of the network 3 is achieved as a consequence of the overcurrent shunt 7 in case the fault is close to the latter. The comparison with Figure 2b, consequently, seems that the level i2 of current 2 is illustrated in it and that it is indicated until an amount of approximately half of ix can represent in the worst case that they occur. Under normal conditions, the purpose is that the overcurrent shunt 7 must be able to establish a short circuit that has a better conductivity than one corresponding to the short circuit fault in the object 1 to be protected so that consequently a major part of the fault current is derived to earth or otherwise a lower potential by means of the current diverter 7. From this, consequently in a case of normal failure, it appears that the energy injection into the object 1 in case a fault becomes substantially smaller than that which is indicated in Figure 2d as a consequence of the lower level of current? 2 as well as the smaller time interval t2-t3. It should be obvious that a protection is obtained as the short circuit, which has been established, has somehow lower conductivity than one corresponding to the short circuit fault in the object 1 to be protected. It has been noted that annotation 8 not only includes the earth but also another unit with a lower potential than the network / equipment 3. It is therefore noted that unit 8 could possibly be formed by another power grid or other equipment included in the electric power plant, equipment that has a lower voltage level than one that is effective for network / equipment 3, for which object 1, which is to be protected, is connected. The overcurrent shunt 7 comprises switching means coupled in the ground 8 or the smallest potential and line 2 between the object 1 and the network 3. These switching means comprise a control means 9 and a switching member 10. This member switch is set to open in a normal state, ie isolating in relation to ground. The switching member 10 may, however, be brought to a conductive state by means of the control member 9 in a very short time in order to establish the current reduction by deviation to ground. Figure 3 illustrates that the devices that detect the overcurrent conditions may comprise at least one and preferably several suitable detectors 11-13 for detecting overcurrent situations that require activation of the protection function. As also appears from Figure 3, these sensors may include the denoted sensor 13 located in object 1 or in its vicinity. In addition, the detector arrangement comprises a sensor 11 adapted to detect the overcurrent conditions in line 2 upstream of the connection of the overcurrent reduction arrangement 5 and line 2. As already explained below, it is appropriate that a sensor 12 is provided to detect the current flowing in line 2 towards the object 1 to be protected, that is, the current that has been reduced by means of the overcurrent reducing arrangement 5. Furthermore, it is signaled that the sensor 12 as well as possibly the sensor 13, are capable of detecting the current flowing in line 2 in an address to the ej ada from object 1, for example in cases where the magnetically stored energy in object 1 gives rise to a directed current away from object 1. It is pointed out that sensors 11-13 do not necessarily have to be constituted only by current and / or voltage sensors. Within the scope of the invention, the sensors can be of such a nature that speaking in general terms they can detect any conditions indicative of the occurrence of a fault of the nature that require the initiation of a protection function. In cases where a fault occurs that the fault current will flow in a direction away from the object 1, the device is designed so that the control unit 14 thereof will control the additional switch 6 for closing, in case it has been open, and, in addition, the overcurrent reducing arrangement 5 is operated so that the short circuit current can be derived therefrom. When, for example, object 1 is conceived to consist of a transformer, the function to the occurrence of a short circuit in it could be such that the short circuit first gives rise to a violent flow of current inside the transformer, which is detected and gives rise to the activation of the provision 5 for the purpose of the current derivation. When the current flowing to the transformer 1 has been reduced to a reduced degree, the switch 6 is forced to interrupt, although controlled by means of the control unit 14, not before the output time for energy, in the occurrence of the case, magnet e cament e * stored in the transformer 1 to flow away from the transformer 1 and be derived by means of the arrangement 5. Furthermore, the device comprises a control unit generally denoted 14. This is connected to the sensors 11- 13, to the overcurrent reducing arrangement 5 and the additional switch 6. The operation is such that when the control unit 14 by means of one or more of the sensors 11-13 receives signals indicating the presence of unacceptable fault currents. towards object 1, the overcurrent reducing arrangement 5 is immediately controlled to quickly provide the required current reduction. The control unit 14- may be positioned so that the sensor 12 has detected that the current or voltage has been reduced to a sufficient degree, controls the switch 6 to obtain the operation thereof for interruption when the overcurrent is below a predetermined level. Such a design ensures that the switch 6 has not been forced to interrupt until the current has been reduced to such a degree that the switch 6 does not have the task of interrupting said high current that is not adequately sized for that purpose. However, the mode may alternatively be such that the switch 6 is controlled to interrupt a predetermined time after the overcurrent reduction arrangement has been controlled to carry out the overcurrent reduction. The circuit switch 4 may comprise a detection arrangement of its property for the detection of overcurrent situations or otherwise the switch can be controlled by means of the control unit 14 based on information from the same sensors 11-13 which also control the operation of the overcurrent reduction arrangement. It is illustrated in Figure 3 that the additional switch 6 comprises a switch 15 having metal contacts. This switch 15 is operable between the interruption and closing operations by an operation member 16, which in turn is controlled by the control unit 14. A branch line 17 is connected in parallel on this switch 15, to the branch line comprising one or more components 18 intended to avoid the arcs in the separation of the contacts of the switch 15 causing the branch line 17 to draw the current from the contacts. These components are designed so that they can interrupt or restrict the current. Therefore, the purpose is that the components 18 normally maintain the conduction path in the shunt line 17 interrupted although the shunt lines close when the switch 15 is open so that consequently, the current is diverted to the switch 15 and that the arcs do not occur or possibly arcs that are extinguished efficiently. The components 18 comprise one or more associated control members 19 connected to the control unit 14 for control purposes. According to one embodiment of the invention, the components 18 are controllable semiconductor components, for example, GTO thyristors having necessary surge suppressors 30. A disconnect 20 for galvanic separation in the current conduction path created by means of the Lifting line 17 for the object 1 to be protected is placed in series with one or more components 18. This disconnect 20 is an operation member 21 controlled by the control unit 14. The disconnect 20 is illustrated in Figure 3 being placed on the derivation line 17 itself. This of course is not necessary. The disconnector 20 can also be placed on line 2 insofar as it ensures the real galvanic separation, by coupling in series with one or more components 18 in the established driving path by means of the series coupling so that consequently there is no possibility for the current to flow through the components 18. The device as described operates as follows: In the absence of a fault, the switch 4 is closed just like the switch 15 in the additional switch 6. The components 18 in the derivation line 17 they are in a non-conduction state. The disconnect 20 is closed. Finally, "the switch means 10 of the overcurrent reducing arrangement 5 are open, that is, they are in a non-conductive state.In this situation, the switch means 10 must, of course, have an adequate electrical resistance so that do not inadvertently reach a conductive state.The overvoltage conditions that occur in line 2 as a result of atmospheric circumstances (lightning strike) or coupling measures, may consequently not involve the voltage resistance of the switching means 10 in its non-conductive state being exceeded For this purpose it is suitable to couple at least one surge suppressor 22 in parallel with the switch means 10. In the example, such surge suppressors are illustrated on both sides of the switch means 10. In As a consequence, surge suppressors are intended to derive such surges that they might otherwise involve. A risk for inadvertent arrest in the switch means 10. The surge protectors 22 are illustrated in Figure 3 to be connected to the line 12 on both sides of the connection of the switch means 10 to the line. It is primarily desirable that at least one overvoltage diverter have its connection as close as possible upstream relative to the switch means 10. The overcurrent shunts 22 could be in place, which is indicated in Figure 3, with dotted lines 26 are connected to the branch line forming the electrical connection between switch means 10 and line 2. Such construction allows the integration of switch means 10 and at least one surge diverter 22 to an individual electrical device, whose apparatus can be brought in electrical connection with line 2 by means of a single connection. When the overcurrent state has been recorded by means of some of the sensors 11-13 or the sensor itself (this is of course done when the information from the switch sensor 4 itself can be used as a basis for the control of the reducing arrangement overcurrent 5 according to the invention) of switch 4 and this overcurrent state is of such a magnitude that a serious fault of object 1 is expected to be available, an interruption operation is only initiated as long as switch 4 is involved . In addition, the control unit 14 controls the overcurrent reduction arrangement 5 to effect such a reduction, and this is more specifically carried, by means of the control member 9, the switch means 10 in an electrically conductive state. As described above, this can occur very quickly, ie in a fraction of time required to interrupt by means of switch 4, for which reason object 1 to be protected immediately is released from the full short circuit current from the network 3 as a consequence of the switch means 10 deriving at least an essential part, and in practice the main part of the current to ground or of or tr to way to a lower potential. As soon as the current flowing into the object 1 by means of the additional switch 6 has been reduced to a required degree, which can be established on a single time basis by a time difference between the activation of the switch means 10 and the operation of the switch 6, or detecting the current flowing in the line 2 by means of, for example, the sensor 12, the operating member 16 of the switch 15 is, by means of the control unit 14, controlled to open the contacts of the switch 15. To extinguish or avoid the arcs, the component 18, for example GTO thyristors or gas switches are controlled by means of the control members 19 to establish the conductivity of the bypass line 17. When the switch 15 has been "open" and, therefore, provided the galvanic separation, the component 18 is controlled again to bring the bypass line 17 to a non-conducting state. Orient from network 3 to object 1 has been cut efficiently. In addition, the shunt line 17 has been brought into the non-conducting state, "the galvanic separation can also be effected by means of the disconnector 20 controlling the operation member 21 thereof from the control unit 14. When all these incidents have occurred, it takes the interruption by means of switch 4 which occurs as a final incident.It is important to note that the overcurrent reducing arrangement 5 as well as the additional switch 6 according to a first mode can be operated repeatedly. has established by means of the sensors 11-13 that the switch 4 has been brought to the cut, the switch means 10 are restored to a non-conductive state and the switch 15 and the disconnector 20 are closed again so that when the switch 4 the first time, the protection device is fully operable, according to another modality, however, it is contemplated that the Overcurrent Reduction 5 may require the change of one or more parts in order to operate again. It is signaled that according to an alternative embodiment of the invention, the component (s) 18 can be brought into a conducting state as soon as the overcurrent conducting arrangement 5 has been brought into a closed state and this regardless of whether the switch 15 possibly it is not open later. The control of the components 18 could then, as described above, occur by means of the control unit 14 or, alternatively, by means of a control function involving a slave following the closure of the arrangement 5. Figure 4 illustrates a first embodiment of the overcurrent reduction arrangement 5 with means of designated switches 10a. The switch means 10a have electrodes 23 and a space 24 that prevails between those electrodes. The switch means' as described so far have means 25a in order to activate the electrode space 24 to form an electrically conductive path between the electrodes. A control member 9a is positioned to control the operation of the members 25a by means of the control unit 14a. The means 25a are placed in the example to cause or at least initiate that the electrode space assumes electrical conductivity by means of which the space or part thereof forms a plasma. It is therefore essential that the means 25a be able to realize a very fast supply of drive energy towards the electrode space. It is therefore preferred that the drive energy be supplied in the form of radiant energy, which in turn is capable of effecting the ionization / initiation of the plasma in the electrode space. The means 25a comprise, according to a particularly preferred embodiment of the invention, at least one laser beam, which by means of the supply of energy to the electrode space causes the ionization / plasma formation in at least a part of the space of electrode. It is preferred according to the invention to supply with the aid of one or more laser beams or other means 25a, the energy towards the electrode space so that the entire electrode space is ionized and brought into the shape of a plasma respectively, of approximately momentary way in a way that also the entire space 24 is immediately brought to electrical conductivity. In order to reserve and optimize the use of the available (normally) restricted laser beam energy, the means 25a can, in the application of the invention, be positioned so that they can provide the ionization. formation of plasma only in one or more parts of the space 24. In the embodiment according to Figure 4, it is illustrated that the means 25a supplies the radiant energy in a single point or area 28. As will be described later, the invention also comprises the application of the radiant energy at a plurality of points or areas in the electrode space, also including one or both electrodes, or in one or more bar areas extending continuously or substantially continuously between the electrodes. By connecting the switch means 10a between the line 2 and the ground 8 (or another unit with less potential) as indicated diagrammatically in Figure 4, that is, with one of the electrodes 23 connected to the line 2 and the another electrode connected to earth 8, there will be a voltage difference between the electrodes that cause an electric field. The electric field in the opening 24 is intended to be used in order to transport or cause an electrical interruption between the electrodes, as soon as the means 25a have been controlled for actuation, that is, they have given origin to the ionization / formation of plasma in one or more parts of the electrode space. The established ionization / plasma formation will drive the electric field to deflect the space between the electrodes in order to, in this way, raise the low resistance electrical conductor to a channel, that is, an arc between the electrodes 23. It is pointed out that the invention is not intended to be restricted to use in relation to the occurrence of such electric field. Therefore, the intention is that the means 25a must be able to establish the electrical conduction between the electrodes also without a field. Due to the demand of the switch means 10a to close the current branch very quickly, it is therefore desirable when only a restricted part, for example, a point-like part of the space is ionized so that the switching means are dimensioned in such a way that the resistance of the electric field in space 24 is sufficiently high to close p However, on the other hand, switching means 10a must have a very high electrical resistance against interruptions "between the electrodes in their isolation rest position. The resistance of the electric field in space 24 must therefore be proportionally low. This on the other hand will reduce the speed, with which the switch means can be driven to establish the current derivation between the electrodes. In order to achieve an advantageous relationship between the desire for a safe actuation of the switch means and on the other hand the high electrical resistance against undesired operation, according to the invention it is preferred that the switch means be formed in such a way that with respect to its full operating environment, the electric field in space 24 has a field resistance that is not greater than 20% of the field resistance at which spontaneous interruption normally occurs, when space forms electrical insulation . This causes a proportionally lower probability of a spontaneous interruption. The resistance the electric field in the electrode space 24 in its state of isolation is adequate of no more than 20% and preferably no more than 10% of the resistance of the field to the spontaneous interruption normally takes place. In order that on the other hand an electric field is achieved in the electrode space 24, the formation of an arc in the initiation of the ionization / formation of plasma is a part of the electrode space in a relatively fast manner it is preferred that the residence in the electric field be at least 0.1%, and suitably at least 1% (E) and preferably at least 5% of the field resistance, in which normally spontaneous intrruption takes place. The electrode space 24 is, as can be seen in Figure 4, enclosed in a suitable case 32. A vacuum as well as a suitable medium in the form of gas or even fluid can for this purpose be -present in space. In the case of a gas / fluid the medium in the space is intended to be formed in such a way that it must be ionized and brought to plasma form by the drive. In such a case it would be suitable to initiate ionization / plasma formation in space 24 at a point somewhere between electrodes 23. However in Figure 4 the case conceived where either a vacuum or a suitable medium is illustrated is illustrated. in the space 24. It is preferred that the initiation of the closure takes place by means of the elaboration of the laser beam 25a, which is illustrated in Figure 4, to focus the radiated energy emitted in at least one area 28 or in the proximity of one of the electrodes by means of the appropriate optical system 27. This implies that the electrode will operate as an emitter of electrons and ions for--. establishing an ionized environment / a space in the electrode space 24 such that an arc is formed between the electrodes. One of the electrodes 23 may according to Figure 4 have an opening 29, through which the laser beam 25a is positioned to emit the radial energy from the area 28 that supports the optical system 27. Figure 5 illustrates a variant 10b of the switch means, wherein instead of the laser of the system 25b / optics 27b they focus the radiant energy in an area of action 28b, which is located between the electrodes and in a medium between those electrodes. The plasma is therefore, upon activation, intended to be developed from this area to link the ectrodes. The variant 10c of the switch means in Figure 6 differs from that of Figure 4 in the way that the auxiliary electrodes 31 have been placed between the electrodes 23c, in this case the auxiliary electrodes which are suitably annular in a form that the beam emitted by the laser beam 25c can pass through the auxiliary electrodes 31. The electrodes are intended to operate to uniformize the electric field between the electrodes 23c and can isolate one from the other, that is, they can be in a floating potential. The auxiliary electrodes result in improved safety against spontaneous interruption, reduced dimensions of the switch means and reduced sensitivity to the effect of external fields. The auxiliary electrodes may also be exposed to the laser beam / laser beam and be made to emit free charges, which further promote the drive capacity.

Figure 7 illustrates a variant 10 of the switch means with the change that the electrodes 31d are also added here, similarly to that described with reference to 1 through Figure 6. In order to achieve the relationships described above with respect to the field resistance conditions between the electrodes 23 in the isolation state in the switch means, the characteristics of the switch means must of course adapt adequately to the intended use, i.e. the voltage conditions that will arise on the electrodes 23. The construction stages available with respect to the formation of the electrodes, the distance between the electrodes, the medium between the electrodes and the presence of possible additional fields that affect the components between the electrodes. The diffractive optical elements can be used with the invention. Diffractive optical elements are elements in which light wave fronts, whose wavefronts determine the propagation of light, are formed by means of diffraction instead of refraction. A particular type of diffractive optical elements modulate only the phase of light and not the amplitude, for which reason the components of this type have a very high transmittance. Pure phase modulation can be achieved by providing the surface of the optical component with a release structure, where the release height must be of the same order as the wavelength in order to achieve optimal function of the component. An alternative way to achieve phase modulation is to modulate the refractive index of the optical element, whose modulation is rather difficult. Diffractive optical elements can be manufactured by means of technique or graphics, which does not admit that arbitrary functions can be performed. A more flexible manufacturing mode is computer generation, in which mode the optical function can be calculated on a computer. The entirely arbitrary optical functions can then, in principle, be performed, such functions are often impossible to obtain by means of conventional refractive and reflective optical elements. The resulting face surface is subsequently transferred to a relief, for example, by means of electron beam lithography or optical lithography, both of which are well known within the semiconductor art. Such components generated by the donor, of surface release to control the phase, are frequently called "forms". Fresnell lenses are a good example. These lenses can, like all diffractive optical elements, be designed as a binary structure consisting only of two levels of release, or as a multi-level release that provides their enhanced diffraction efficiency (functional efficiency of the optical element). Figure 8 illustrates an embodiment based on an optical system 27e comprising a lens system 35, by means of which incoming laser pulses are conveyed to a diffractive optical phase element 36, a cynoform. This element is designed to have a plurality of focal points or points 28e generated starting from a single input laser pulse. These focal points 28e are distributed along the axis of symmetry between the electrodes 23e. As a consequence of the focal point 28e which is distributed along a line between the electrodes 23e, a safer establishment of an electrical conduction path between the electrodes is achieved, representing as high a probability for the drive as possible to a voltage / electric field resistance as low as possible and with the time delay as short as possible. The cinoform 36 is of low absorption and can, as a consequence, resist extremely high optical energy densities. Accordingly, the cynoform is produced from a dielectric material so as not to disturb the electric field between the electrodes to any serious degree. - In the modality according to Figure 8, the radiant energy is supplied through an opening 29e in one of the electrodes as above. Figure 9 illustrates a variant where, generally speaking, the only difference compared to the mode according to Figure 8 is that the diffractive optical element (cynoform 36f) is positioned radially externally of one of the electrodes 23f. The optical element 36f is as previously designated to deflect the laser light and focusing it is a number of points or areas distributed along the intended electrical conduction path between the electrodes. The beam groups forming the points 28f each have their own deflection angle. Therefore, the beam groups have to travel at different distances towards the respective points 28f. The advantage in locating the cynoform 36f according to Figure 9 on the side of one of the electrodes is that the cynoform will be located laterally of the strongest electric field so that the field disturbance will be at minimum u-n. The electrode design is also simplified since no opening is required for the laser light. Figure 10 illustrates an embodiment in which a laser 25g supplies the laser radiation by means of an optical system 27g symmetrically at a number of focal points or areas 28g distributed along the length of the electrode space without requiring any opening in the electrodes 23g. The optical system 27g comprises a prism or beam splitter 37 positioned to deflect the laser beam around the adjacent electrode 23g. Around this electrode 23g is provided one or preferably more cinoforms 36g (diffractive optical elements) designed to focus, possibly by means of additional lenses, the laser beam at the desired focal point 28g so that the plasma formations are generated at those points . Figure 11 illustrates a variant in which a laser beam is transported by means of an optical system 27h comprising optical fibers 38 for the formation of focal points 28h located in various places between the electrodes 23h. The optical fibers 38 can be positioned to emit light by means of lenses 3-9. Figure 12 illustrates the basic principle of a conical lens, called an axicon. The definition of such an axicon can be for each optical element that has symmetry with respect to rotation and that is capable of deflection of light by means of refraction, reflection, diffraction or combination thereof from a point source on the axis of symmetry of the element in such a way that the light intersects this axis of symmetry not in a single point as would be the case with a conventional spherical lens but along a continuous line or points or in areas along a substantial extension of this axis. It is illustrated in Figure 13 that the collimated (non-divergent) light beams are deflected by the axicon from the same angle. As a consequence of the symmetry insofar as it refers to rotation, each beam will cross the axis of symmetry at some point. From Figure 14, it appears that the light can be focused on an elongated focal area 28i and located between the electrodes 23i via the axicon 36i. This elongated focal area can, according to one embodiment of the invention, be continuously extended over the entire distance between the electrodes, although it could also adapt only a part of the space between them. Figure 15 illustrates how the intensity is related to the distance between the electrodes. The full line curve illustrates the intensity distribution in illumination with the light beam that originally had a gas intensity distribution considering that the dotted line curve illustrates the intensity distribution in the illumination with a constant intensity distribution. For the rest, it is pointed out that the invention is not restricted only to such axes, which are purely in a conical linear form. Therefore, the axicons, the crown surface which deviates from the linear cone, which will have a direct influence on the focal intensity distribution, are included within the scope of the invention.

Figure 16 illustrates that a result similar to that of Figure 14, while the focal area 28k is related can be achieved by means of a diffraction optical element 36k, a fixed shape. Figure 17 illustrates an elongated focal area 28m in the space between the electrodes 23m, which can be achieved by means of an axicon more specifically a reflective axicon. Figure 18 illustrates a modality where a particularly designated diffractive axon 36n, a cynoform, has been designed to provide focal areas 28n and 28n ', respectively, having different shapes. In the example it is illustrated that the focal area 28n is elongated and placed on the axis of symmetry of the axicon 36n and the electrodes. In contrast, the focal area 28n 'has, as indicated to the left in Figure 18, a tubular shape in the cross section. This tubular shape is advantageously more closely towards an electrode 23n provided with an opening 29n since the periphery of the focal area 28n 'will be located relatively close to the electrode 29n provided with an opening. The focal areas 28n and 28n 'have, in Figure 18, a substantially constant intensity along the axis of symmetry although perpendicular to this axis, the intensity distribution, so much that the focal area 28n is referred to, is substantially in the form of Gauss or in the form of agreement, with the Bessel function. One advantage with a diffractive or substantial or entirely conical coaxial focusing component for the case in Figures 8, 9, 10, 14, 16, 18 is that along the efficient propagation direction of the radiant energy, the direction of propagation that is a straight line, the volume of plasma that first formed that occurs closest to the electrode, in which the radiant energy is delivered, will not be protected, reflected or will be to a degree seriously affected by radiant energy focused on points / areas that are located farther from the supply electrode. This "shadow effect" from the plasma volumes formed first could otherwise have hidden the radiant energy to efficiently reach the last foci. This is a consequence of the fact that the plasma has the ability to be able to reflect or absorb the energy r adi ante.

Figure 19 illustrates a mode where a generator lb is connected to a power network 3a by means of a transformer la. The objects that are to be protected, therefore, are represented by the transformer la and the generator Ib. The overcurrent reducing arrangement 5a and the additional switch 6a as well as the ordinary switch 4a- are apparently placed in similarity to what is evident from Figure 1 in the case that object 1 of Figure 1 is designed to forming the object according to Figure 19. Therefore, in this respect referred to with the descriptions in relation to Figure 1. The same is true for the protection operation of the overcurrent reducing arrangement 5c and the additional switch 6c in relationship with the generator lb. The generator lb must therefore in this case be equivalent to the object 1 in Figure 1 while the transformer must be equivalent to the equipment 3 in Figure 1. The overcurrent reducing arrangement 5c and the additional switch 6c, so both will be in combination with the conventional switch 4b which is able to protect the generator lb against a violent current flow in the transformer direction la. Figure 19 also illustrates the additional overcurrent reduction arrangement 5b with the associated additional switch 6b. Apparently, the overcurrent reducing arrangements 5a and 5b will therefore be placed on both sides of the transformer la. It is noted that the additional switches 6a and 6b, respectively, are placed in the connections between the overcurrent reducing devices 5a and 5b and the transformer la. The additional overcurrent r-eductor arrangement 5b is intended to protect the transformer from the violent current flows to the transformer from the generator lb. Switch 4b will apparently be able to interrupt independently in which direction, the objects la and lb a security function is desired. Figure 20 illustrates diagrammatically how the radiant energy can be delivered to the space between the electrodes 23o by means of one or more laser beams 25o on. one or more points or areas 28o relative t to an X axis of symmetry between the electrodes 23o. By using a plurality of different 25o laser beams, a very high energy can be supplied to the space between the electrodes for plasma formation. Figure 21b illustrates that a plurality of substantially parallel electrically conductive channels can be formed between the electrodes 23p. The view in Figure 21a could be formed by the vertical view of Figure 21b, in which case, the electrically conductive channels, viewed from one side, are a single row. However, it is possible to place a plurality of electrically conductive plasma channels, not only in rows - but also in columns between the electrodes. The occurrence of a plurality of electrically conductive channels simultaneously increases the driving capacity of the switch means. Figure 22 illustrates a variant where the optical system 27q comprises an axicon (refractive or diffractive) that divides the variation coming from a laser beam or the like into parts and directs those parts of radiation towards the diffractive elements (cyanoforms 36q). These cynoforms are distributed around one of the electrodes, that is, one denoted 23q in Figure 22. The same structure as in Figure 22 is shown in perspective in Figure 23. It appears that in Figure 23 in Example 4, the cinoforms 36q are placed around the electrode 23q to cause the radiant energy to be focused by diffraction at a number of points or areas 28q present along the axis of symmetry of the electrodes. The use of several 36q discrete cynoforms would seem to be simpler and not costly to perform than a continuous annular cynoform even if the latter were impossible. Semiconductor components, such as thyristor, triac, GTO, IGBT and several others, are common in today's electrical power systems, where they are mainly used as electronic valves to control, ie transport or block the flow of current electric Even if the semiconductor components have a high efficiency, good performance present and are relatively non-expensive and through the development of modern manufacturing methods, they are - mainly at high voltage electrical levels - problems that require complicated and bulky and costly technical solutions.

Through the modalities of the technical solutions presented in this specification, the alternatives to the semiconductor components were presented, they explained, such alternatives that provide simpler designs with fewer components and at lower costs. In addition, the technique presented allows the design of valve components that can withstand voltages considerably greater than the corresponding semiconductor components. Furthermore, it is of fundamental importance that the components based on the technique presented here can withstand almost unrestricted electric currents and current densities. Within the semiconductor elements of the electric power technique are used in a large number of applications. This part of the technique of electrical energy is usually called power electronics. These applications are commonly referred to as converters. A converter is an operating unit consisting of semiconductor units (electronic valves) and the necessary peripheral equipment used to change one or more of the variable characteristics and parameters of an electrical power system. Therefore, the converter can change the voltage and current level, the frequency and the number of phases. Likewise, electronic switches can be considered as converters. As a converter (current transformer) also an apparatus that interconnects a direct current system with an alternating current system is considered. In the case of the flow of energy that is in one direction from the alternating current to the direct current side, the converter operates as a rectifier. In the case of the energy flow that would occur in one direction from the direct current side to the alternating current side, the converter operates as an alternator. An AC-AC converter is dominating a frequency converter and converts an AC signal to another AC signal with an arbitrary relation to the frequency, amplitude, phase and phase position as well as the number of voltage phases . A direct current to direct current converter converts the direct current voltage to another direct current voltage.

The electronic switch can be designed for alternating current or direct current.

It can be used to connect or disconnect an appliance or to control or verify the active or reactive energy. An electronic valve is controllable if it can change from a block state with high voltage and low current (shutdown state) to a conductive state with low voltage and high current (on state). The great efficiency of the electronic converters depends on this bistable invention of the valves. A valve can be stable by itself, such as the thyristor or being controllable to operate in a bistable manner as a transistor. The terminology is fortunately not consistent at all. An IEC compilation can be counted in "International Electrotechnical Dictionary" and in Publ. 60050-551 IEV, "Power Electronics". There are a large number of different semiconductor components that can be completely or partially replaced by the technique that is the subject matter of the present patent application. Two examples of the state of the art presentation are "Modern Power Electronics" by 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. Among the available semiconductor components that deal with these literature references are the following: -tiristor, diode, triac, GTO (bridge closing thyristor), bipolar transistor (BJT), PWM transistor, MOSFET, IGBT (transistor) isolated gate biopolar), SIT (static induction transistor), SITH (static induction thyristor), MCT (MIST controlled thyristor), etc. I. A thyristor is switched off (transferred to a blocking state) when its current is brought to zero by external means. In self-extinguishing alternators, valves are turned off by shutdown circuits consisting of condensate, inductors and resistors. The thyristor is the dominant semiconductor component for high voltage and energy levels. The thyristor is defined as a semiconductor component that has a bistable function. It consists of three pn transistors. It can be switched from the off state to the on state and vice versa in one or two directions. The most commonly used type of thyristor is the so-called "reverse blocking diode thyristor". The thyristor has three connections: anode, cathode and gate. In the absence of the control pulse in the gate, the thyristor blocks the flow of current in both directions. With a set voltage that is positive on the anode and negative on the cathode, the thyristor is in its off state and blocks the voltage. If the imposed voltage has an opposite polarity, the thyristor is in its reverse direction of the blocking state and reverses the voltage block. The loss current in the reverse block and the blocking states increase with the size of the thyristor and the temperature and can for very large thyristors be above a few hundred mA. If the thyristor is operated by imposing a current or pulse of voltage on the gate, with the appropriate amplitude and duration, the thyristor switches from the off state to the on state and a current can flow in the direction of the anode towards the cathode. The voltage drop (the voltage over the thyristor) the so-called on-state voltage, is typically 1-2 volts for normal values in the on-state current. If the blocking (in the anode advance direction towards the cathode) of voltage exceeds the interruption of the specified overvoltage for the thyristor, it spontaneously switches from the off state to the on state. This autoactivation voltage can seriously damage the thyristor and therefore, must never be exceeded. If in high voltage applications, where the system voltage substantially exceeds the maximum voltage that a single thyristor element can, resist, several thyristors in series or cascade must be coupled. To achieve an adequate voltage division between the thyristors coupled in series, each of them must be provided with an individual RC circuit and with a resistive voltage divider: The RC circuit acts as a transient voltage divider and the resistor divides the blockade and the backward blocking respectively of the voltages to approximately the same voltage difference by thyristor without affecting the fact that different thyristors have different loss currents. further, the resistors can make the voltages on the capacitors of the RC circuits equally large. For thyristors connected in series it is of greater importance that the activation pulses of all the thyristors are simultaneous and have identical amplitudes. The deviations of the simultaneous drive result in an overvoltage on the thyristor that is driven (becomes conductive) as at least a consequence of the current flowing through the RC circuit thereof and through other thyristors. Frequently it is required that only thyristors that have been coupled together are used, that is, they have been selected to present performances adapted to the other thyristors, particularly in high frequency applications, which complicates the structure and makes the same more expensive. A triac is a bidirectional thyristor, which means that it has blocking directions or directions of advance. A triac is equivalent to two thyristors connected antiparallel and has a common gate. A triac is at first in its blocking state. The transfer to the on state can, however, be controlled by a negative pulse as well as a positive one in the gate, and this can be achieved by both possibilities on the triac. The technical performances for a triac correspond in most cases to those with a thyristor that has a corresponding size and performance. The restriction exceptions are caused by the triac that has no short rise and fall times like the thyristor and does not have the same resistance to transient voltages (dU / dt). Therefore, they are used mainly in voltage regulators that have a resistive load and for net frequencies, where rapid fluctuations in currents and voltages do not occur. A property of the triac to be bidirectional and only require an individual cooling element as well as an individual drive pulse implies that simple and relatively inexpensive structures can be designed in particular for low electrical power levels. Thyristors powered by light have, for natural reasons, a great interest for high voltages as in HVDC systems and in systems for thyristor switched base compensation systems. The primary reason is the high demands of electrical insulation. In addition, the risks are reduced since the thyristor ignites / opens spontaneously as a consequence of noise coupled to its gate. The pulses of light to the thyristor are transmitted by means of a light conductor to the thyristor from one. control unit on the ground potential. Since the light conductor consists of dielectric material, high volta insulation can be obtained. However, the light energy that can be transferred by means of light conductors is restricted and there is a risk that the thyristor system obtains a large time delay for the control signal and, consequently, a low rate of increase associated with it. of the thyristor on state current unless the thyristor is equipped with a much more complex control structure comprising an amplification function for the signal that is finally applied on the thyristor gate. However, such a structure means that the thyristor becomes more sensitive again to the noise that can be coupled by means of the gate and lead to inadvertent interruptions. A laser-driven plasma switch can fulfill the same functions as the plurality of power semiconductors and in some cases with great technical and economic advantages as a result. In the present patent application the function of a laser-operated plasma switch as a triac is specifically referred to. A laser-driven plasma switch, which is based on a momentary short circuit of an electrode space filled with gas by means of an elongated channel, ionized and electrically conductive, generated by laser light, has mainly the following advantages: The distance between the electrodes contained between the electrode system can be made large so that the biggest problems do not occur in the sizing and design of the electrode system. Electrical isolation. The structure is in that considerably simplified form and can be manufactured with lower costs. Another substantially greater advantage is that there is in principle no restriction for the maximum current that can be conducted by the plasma switch when it has been brought to its conductive state by the laser drive. The conduction of the electrical current happens through the laser light generated in the ionized channel that quickly is developed until an arc. An arc is not subject to fundamental restrictions as the maximum current, which flows through it, is related and there is accordingly no maximum limit for the current density as is the case with the semiconductor components. When the current is increased, the arc maintains an energetically advantageous current density expanding radially. This auto-tuning function has no correspondence in the semiconductor component. A third fundamental advantage is formed by the fact that a plasma switch can be designed for several high voltage levels, and can be constituted only as an individual component. Compared to a stacked semiconductor structure, which has the same function and for the same high voltage level, this results in a considerably reduced complexity, not only in the structure itself, which does not have to consist of a large number of elements semiconductors, connected precisely, but also in the drastically reduced demands on the synchronization of those components in relation to each other. A substantially reduced number of active components in an application, compared with the corresponding application achieved with semiconductor components, results in increased reliability. In addition, reduced electrical losses, reduced device costs and less complicated control systems are also achieved. An additional advantage is that the drive can be carried out quickly, in the order of a few hundred microseconds, a fact that increases the possibility of precision modulation.

Triac function The laser drive in an elongated focal area allows interruption from the off state to the on state at an arbitrary time point. By its construction, with a suitable combination of the electrode distance, gas pressure, gas composition and partial pressures of the partial gases and the general geometry of the encapsulation vessel, the plasma switch according to the invention has identical properties to those of a triac. Without activation, the plasma switch is present in its non-conductive shutdown state. This blocking property is bidirectional, that is, the component is electrically insulating for voltages of both polarities on the plasma switch. Activation, the plasma switch is transferred almost momentarily to its on-state conductor, in which it remains as long as the current in the arc is maintained above μn a specific design value, and as long as the voltage of the switch electrodes of plasma are maintained over a certain specific design value as well. Likewise, this conductive state is bidirectional: A plasma switch element can be made conductive for both polarities by means of the laser drive. An interruption arrangement with radiant energy drive is illustrated diagrammatically in FIG. 24. A laser beam, for example, can be used for driving. A switch arrangement 5 is operable in both polarities, which gives a bidirectional function.

Function of the Triac with shutdown circuit In an application, the function of "application setup can be completed with a possibility to deactivate the switch, that is, to transfer it to the off state.This is achieved by means of the switch (1) that automatically turns off. self-extinguishing through its construction with a suitable combination of electrode distance, gas pressure, gas composition and partial pressures of the partial gases or (2) the switch that has properties that allow external deactivation. ) The period after which the autodetection occurs can be verified and determined by the design of the structure.This deactivation function can be performed for direct current as well as alternating current systems.The case of the alternating current is one more case simple in that self-deactivation is automatically assisted by the current through the conductor arc that changes from olarity and, consequently, it passes through zero current. According to the aforementioned state, conditions are created to efficiently deactivate the plasma switch is a form that is completely equivalent to that used to deactivate a thyristor. Therefore, the case of alternating current poses less demanding demands on the structure of the plasma switch. In case (2) the plasma switch can therefore be provided with external impedance elements, which ensure that the current of the on state is reduced to zero so that the plasma switch opens and assumes its off state. The same effect can be achieved using the circumstances considered in a CA system: Just before the current changes the polarity in its passage to zero, the plasma switch is deactivated by itself as a consequence of the insufficient ionization of the gas as length of the discharge channel. During the time it takes for the current to change polarity and for the new polarity to reach a voltage, by which the fully ionized plasma channel could be electrically conductive, a sufficiently large proportion of the plasma components has a time to recombine to a degree such that the conductivity of the channel becomes too slow to sustain the repeated activation of the arc. Therefore, re-ignition is avoided and the plasma switch has assumed its off state.

In contrast, the case of direct current involves more demanding demands on the structure of the plasma switch. By precisely balancing the design parameters, such electrode distance, and especially the total gas pressure, including the gas components and the partial pressures thereof, these demands can be satisfied so that the self-deactivation A natural alternative is to allow the current to be switched to another line or component, the current in the plasma switch to be reduced to zero, and the plasma switch to be turned off. However, the simplest technical solution is to also complete the direct current component with an external current restricting circuit element. A more severe solution, albeit nevertheless efficient, is to couple in a suitable way in connection with the plasma switch mechanical switches, by means of which the plasma switch can be completely separated from the network under 11 a.

Unidirectional Triac Function A triac can be driven in two directions in its on state. The plasma switch as it has been described here is in its mainly bidirectional nature, since it has no type of diode function. However, if the laser activation is carried out during one of the two polarities of an alternating current system, the function becomes practically unidirectional, but on the condition that the rest of the plasma possibly remains as the previous drive after recombination it has a conductivity sufficiently low to withstand a spontaneous drive under polarity (the average period of the AC voltage) that is not laser activated. Figure 25 illustrates a plasma switch according to the invention with unidirectional triac function.

Bidirectional triac function with two plasma switch elements. An alternative to the modality described above is formed by two plasma switch elements having a shut-off function (auto-disactivation or external deactivation function) the plasma switch elements that are connected antiparallel between the highest and the lowest potential. The two plasma switches that have now been built and connected to the alternating current system to form two undirectional units is in accordance with that established above, they are connected to the network and in relation to each other in such a way that the current connection directions of the two switches are opposite. Since the plasma switch itself is bidirectional, this means that the two elements are designed to be laser-driven during their respective polarities, that is, during a period half of their ownership, of the AC voltage. The two plasma switches can be operated by one and the same laser beam, which requires that the optical system be provided with a luminous flux control shutter. The laser is operated at least twice per period and once per half period and the shutter can, in one embodiment be designed so that the entire amount of light emitted from the laser beam is directed alternately towards one or the other of the laser. the two elements of plasma switch. The luminous flux directional shutter can, for example, be constituted by a highly reflective rotating mirror, which by reflection from its two extreme positions directs the laser light towards each of the two light channels leading to the respective plasma switches. Another modality is to divide the laser light into two channels with an equal amount of laser effect in both channels. Each channel leads to one of those plasma switches. A luminous flux control shutter has been installed in each channel, the shutter is secured by controlled action in each drive operation, that only one of the two plasma switch elements is subjected to the driving laser light. The two plasma switch elements can also be operated by a laser for each plasma switch element, the operation of the lasers being controlled, verified and synchronized by an external electronic unit. Figures 26, 27 and 28 illustrate the described possibilities for the formation of bidirectional triac functions.

The same capacity of biodirection is of course also achieved with the corresponding coupling of two plasma switching elements, which do not have the function of self-deactivation or that have not been provided with external means for deactivation.

Thyristor Functions As described in the prior art, the thyristor has a blocking state called the off state for voltages and currents in both directions. When the thyristor is operated on its gate, it assumes its conductive state, called the ignition state, in which the current can flow in the forward direction of the thyristor, although in the opposite direction. A preferred way of achieving the same function by means of the laser-driven plasma switch means means that the laser-driven plasma switch is coupled in series with one or more diode functions, which may be of the semiconductor type. The number of diodes is determined entirely by the maximum voltage, which in an application in the view may have to be placed on them.There are two different possibilities to orient the diodes in relation to the plasma switch: With the direction of advance towards the plasma switch and with the forward direction directed away from the plasma switch.Thus, two different thyristor functions can be performed, where the resulting thyristor unit consists of the plasma switch in series with a number of diodes that obtains different directionality or It is preferred that the diodes contained in such a constellation are equipped with indivi dual or other more general impedance networks and a resistive voltage divider in order to efficiently achieve a division of equalizing voltage. The diodes are, therefore, not subjected to different voltage levels, which could exceed their specified voltage resistance. Figures 29a-d illustrate that a plasma switch according to the invention can achieve different directionals or polarities by means of one or more diodes s. As an example of how the plasma switch described above can be used with a triac function or with a thyristor function, reference is made to FIGS. 30 and 31. The circuits presented in the figures act as a change on the int. er r rup to re s. The function in Figure 30 is as follows: The upper conductor Lx is connected to an alternating voltage, considering that the lower conductor L2 is connected to ground or to a lower potential. While the voltage of the upper conductor 1i is positive without any of the plasma switches PSi and PS2 having been driven, no current can flow through the circuit. However, if the plasma switch PS2 is operated to close, a current will flow through the diode Di from the upper conductor Lx to the ground through PS2. This current flows as long as the voltage has a positive polarity. After the change of polarity to negative polarity on the upper conductor 11, a current will flow in the opposite direction. However, such a current can only flow after PSi having been driven and which then flows from the upper conductor through diodes D2 and PSi and the lower conductor through diodes D2 and PSi towards the upper conductor. Since the voltage drop over diode D2 can be made smaller than the voltage drop over the arc in PS2 in the direction from L2 to lr the current preferably flows through D2 after the polarity changes with that described instead of through PS2. PS2 may not spontaneously re-ignite in the wrong direction, and is left as a consequence to rest during the current average period with a negative plurality. In the circuit described above, the plasma switch is used in the function of a unipolar triac, that is, generally a thyristor. The circuit in Figure 31 has been provided with two additional diodes in series with respective plasma switch, which completely guarantees that the current after the polarity change is not wrongly searched to pass the plasma switch to be deactivated. Therefore, the • Additional diode prevents, as an example of external means, that this switch is reactivated ("retro-ignition"). It is considered obvious from the presentation given above that the more technical functions "than those presented here can be realized as long as a laser-operated plasma switch is used as a starting point.

Figure 32 illustrates diagrammatically that a switch arrangement 5r is coupled in series on line 2r previously described between network 3r and object Ir. Switch arrangement 5r suitably comprises switch means lOr with the previously described characteristics , ie, switch means having an electrode space adapted to be electrically conductive by means of radiant energy. However, this is not shown more clearly in Figure 32. As shown from Figure 32, the switch arrangement 5r is intended to have a purely switch function, i.e. the feed of the Go object or possibly the power supply. in the opposite direction it can occur by means of the switch means lOr when they are in a conducting state. When the need exists, the switch means lOr can be made to inhibit the passage of current relatively quickly, for example for protection of the object Ir or possibly the network 3r of the current flow from the object ld. In order to achieve the deactivation by means of the switch means lOr in alternating current connections it is sufficient that the means for supplying energy to the electrode space stop working with such a power supply. In the following passage through zero, the extinction of the arc by the switch means lOr is intended to take place in such a way that the power supply is terminated. In direct current application, it is probably necessary to sustain the same deactivation function by taking measures to reduce or eliminate the voltage difference over the switch means lOr. Such means may consist of a switch 31 coupled in parallel to the switch means lOr. The closing of the switch means 31 means that the current is diverted by passing the switch means 10, a fact which causes the arc in the switch means 10 to be extinguished. In the case of a measurement it would not be sufficient, with additional switches, it could as a complement in the same be placed on either side of the switch means lOd in the line 2r to completely disconnect the switch means lOr from the line 2r . The purpose with Figure 32 is to illustrate that the switch arrangement 4r according to the invention can find general switch applications, in which it may be a matter of protecting several devices but also the interrupting energy in several load situations in one direction more general. It should be noted that the description presented above, should only be considered as illustrative for inventive idea, on which the invention is constructed. Therefore, it is obvious to the person skilled in the art that detailed modifications can be made without departing from the scope of the invention. As an example it can be mentioned that according to the invention it is not necessary to use a laser to supply the ionization / formation of plasma energy to the space 24. Also, other radiant sources, for example electronic cannons, or other supply solutions of energy can be applied insofar as the demands for speed and reliability according to the invention are satisfied. It should be noted that the switch means 10 can according to the invention be applied for protection "of electrical objects on currents related to failure also in other operational cases than those illustrated in Figures 1, 3 and 19, where the device in accordance with the invention is positioned in order to reduce the negative effects of the relatively slow interruption time of the switch 4. Therefore, the switch means according to the invention does not necessarily need to be related to the operation for such switch 4. Finally, it must be observed that the invention is very suitable for alternating current as well as for direct current.

Claims (51)

1. A device for switching electric power comprising at least one electrical switching arrangement, characterized in that the switching arrangement comprises at least switching means, which comprise an electrode space that is convertible between a state of isolation and its electrical and an electrically conductive state, and means for causing or at least initiating the electrode space or at least a portion thereof to assume an electrical conductivity and that means for causing or at least initiating the electrode space to assume the conductivity that are adapted to supply electrical energy to the electrode space in the form of radiant energy carries space or at least a part thereof to the shape of a plasma.

2. The device according to any preceding claim, characterized in that the means for causing or at least initiating the electrode space or a part thereof assumes the electrical conductivity, comprises at least one laser beam.

3. The device according to any of the preceding claims, characterized in that the switching means are formed in such a way that the electric field is present in its insulating condition between the electrodes, whose field promotes or generates an electrical flash between the electrodes causing or initiating the electrode space to assume the electrical conductivity.

4. The device according to claim 3, characterized in that the electric field in the insulating condition of the electrode space has a field resistance substantially less than the field resistance, in which the spontaneous interruption occurs.

5. The device according to claim 3 or 4, characterized in that the electric field in the insulating condition of the electrode space has a field strength that is not more than 30%, suitably not more than 20% and preferably not more than 10% of the field resistance, at which the spontaneous interruption occurs.

6. The device according to any of claims 3-5, characterized in that the Electric field in the insulating condition of the electrode space has a field resistance that is at least 0.1%, suitably at least 1% and preferably at least 5% of the field resistance, at which spontaneous interruption occurs.

7. The device according to any preceding claim, characterized in that the means for causing or at least for initiating the electrode space to assume the electrical conductivity are positioned to supply the radiant energy in such a way that the lower resistance of the electric field, to the fact that the electrode space can be operated to assume electrical conductivity is minimized.

8. The device according to any preceding claim, characterized in that the means for causing or at least initiating the electrode space to assume the electrical conductivity, are positioned to supply the radiant energy to the electrode space in such a way that a delay of The time between the radiant energy of arrival and the developed conductivity of the electrode space is reduced to a minimum.

9. The device according to any preceding claim, characterized in that the switch means and the means for causing or at least initiating the electrode space to assume the electrical conductivity are positioned so that the establishment of the electrical conductivity in the space of The electrode is substantially independent of the electric field resistance present between the electrodes of the switching means in their insulating state.

10. The device according to any preceding claim, characterized in that the means for supplying the activation energy to the electrode space are arranged to apply the radiant energy or at least one in the vicinity of at least one of the electrodes.

11. The device according to any preceding claim, characterized in that the means for supplying the activation energy to the electrode space are positioned to locate the radiant energy at a point or area in the space between the electrodes.

12. The device according to any preceding claim, characterized in that the members for supplying the drive energy to the electrode space are positioned to apply the radiant energy at two or more points or areas between the electrodes.

13. The device according to claim 12, characterized in that the means for supplying the activation energy to the electrode space are positioned to locate the two or more points or areas of radiant energy along a line extending between the electrodes, the line corresponding to the extension of the desired electric conduction path between the electrodes.

14. The device according to any preceding claim, characterized in that the means for supplying the activation energy to the electrode space are arranged to apply the radiant energy in one or more areas (28i, k, m, n), the longitudinal axes of which extend substantially along the direction of the electric conduction path that is intended between the electrodes.

15. The device according to claim 14, characterized in that the means for supplying activation energy to the electrode space are adapted to form the elongated focal area within a tubular shape.

16. The device according to claim 14 or 15, characterized in that the means for supplying the activation energy to the electrode space, are adapted to form the elongated area so as to link, integer or substantially entire, the space between the e 1 ect rodos.

17. The device according to claims 14 or 15, characterized in that the means for supplying the activation energy to the electrode space are adapted to form two or more elongated focal areas in the electrode space, the focal areas which are longitudinally located after another along the path of electrical conduction destined between the electrodes.

18. The device according to claims 1-10, characterized in that the means for supplying activation energy to the electrode space are adapted to apply the radiant energy on at least one of the electrodes as well as between them.

19. The device according to claims 10-18, characterized in that at least one of the electrodes in the electrode space has an opening, through which the means for supplying activation energy are positioned to direct the radiant energy.

20. The device according to claims 15 and 19, characterized in that the means for supplying the activation energy towards the electrode space are adapted to locate the area of tubular radiant energy in the vicinity of that electrode having an opening and so that the axis of the tubular radiant energy area is substantially concentric to the axis of the opening in the electrode.

21. The device according to any preceding claim, characterized in that the auxiliary electrodes to equalize the electric field and / or to activate the participation in the activation process of the auxiliary electrodes that are exposed to the radiant energy and, as a result, are capable of emitting free charges, are placed in space, between the electrodes.

22. The device according to any of claims 10-21, characterized in that the means for supplying electric power to the electrode space comprises a system for controlling the electromagnetic wave energy.

23. The device according to claim 22, characterized in that the control system comprises at least one refractive, reflective and / or diffractive element.

24. The device according to claim 23, characterized in that the element is formed by an axicon.

25. The device according to claim 23, characterized in that the element is formed by a cynoform.

26. The device according to claim 23, characterized in that the elements comprise optical fibers 38.

27. The device according to any of claims 23-26, characterized in that the control system is located radially outward from the electrodes and adapted to direct groups of rays towards the space between the ect ects.

28. The device according to any of claims 23-27, characterized in that the control system is adapted to divide the laser pulses in an annular configuration around one of the electrodes.

29. The device according to any preceding claim, characterized in that at least one overvoltage diverter is connected in parallel to the switching means.

30. The device according to any preceding claim, wherein the electrical object is connected to a power grid or other equipment included in the power plant, the device comprising a switching device in a line between the object and the network / equipment, characterized in that the switching means are connected to the line between the object and the switching device, and that the switching means are operable for overcurrent bypass within a period substantially shorter than the time of interruption of the switching device.

31. The device according to claim 30, characterized in that the switching device is formed by a circuit breaker.

32. The device according to claim 21 or 31, characterized in that it comprises an additional switch placed in the line between the switching device and the object, the additional switch that is placed between the switching means and the object and is adapted to interrupt lower voltages and currents than the switching device, and therefore capable of executing a shorter interruption time than the switching device and that the additional switch is adapted to interrupt when the overcurrent to, or from the object is has reduced by means of the switching means, although substantially before the switching device.

33. The device according to claim 32, characterized in that it comprises a control unit connected to the detection arrangement and to the additional switch in order to achieve the activation of the additional switch for interruption purposes when the overcurrent to or from the object is indicated , by means of the detection arrangement, to be below a predefined level.

34. The device according to any of claims 32-33, characterized in that the additional switch comprises a switch on which a bypass line having one or more components is coupled, to avoid the arcs in the contact separation of the switch, causing the derivation line to take care of the current conduction from the contacts.

35. The device according to claim 34, characterized in that one or more of the components in the branch line can be closed in the conduction by means of the control of the control unit.

36. The device according to claim 34 or 35, characterized in that one or more components are formed by controllable semiconductor components.

37. The device according to any of claims 34-36, characterized in that one or more components are provided with at least one surge suppressor.

38. The device according to any of claims 34-37, characterized in that a disconnect for galvanic separation is placed in series with one or more components.

39. The device according to claim 38, characterized in that the disconnect is coupled to the control unit to be controlled by it to open after the switch has been controlled to have closed and one or more components have been placed in a condition to interrupt the derivation line.

40. The device according to any preceding claim, characterized in that the protected object is formed by an electrical device with a magnetic circuit.

41. The device according to claim 40, characterized in that the object is formed by a generator, transformer or motor.

42. The device according to any of claims 1-41, characterized in that the object is formed by an energy line, for example a cable.

43. The device according to any preceding indication, characterized in that two switching means are placed on either side of the object to protect it from the two sides.

44. The device according to claim 1, characterized in that it comprises a control unit, connected to the switching means and to the overcurrent conditions detecting arrangements, the control unit that is placed to control the switching means for closing in base to the information from the detecting arrangement of overcurrent conditions when it is required for reasons of protection. ~

45. The device according to claim 44, and one or more of the claims 34, 36 and 40, characterized in that one and the same control unit is positioned to control, based on the information from the overcurrent conditions detecting arrangement , the switching means and the additional switch.

46. The use of a device according to any preceding claim, for the protection of an object against the s obr ecorr i ent is related to failure.

47. The device according to any preceding claim, characterized in that the means for supplying the driving energy to the electrode space are adapted to focus the radiant energy on a plurality of elongated focal areas their tanci alment e parallel, the longitudinal axes of which they are located substantially along the direction of the electric conduction path directed between the electrodes.

48. The device according to any preceding claim, characterized in that one or more switching means, possibly in addition to the complementary diodes or other components are arranged to form the switching or converter functionalities.

49. The device according to claim 48, characterized in that the functionalities are triac and thyristor functionalities.

50. A method in an electric power plant for protection of an electrical object of the over-current is related to failure, characterized in that the derivation of the overcurrent is achieved by means of switching means, when the overcurrent conditions have been detected by means of an arrangement for such detection, the switching means, which are placed for derivation of the overcurrent to ground or some other unit with a relatively low potential, which is closed for bypass of the overcurrent by imparting an electrode space, which is present in the switching means, the electrical conductivity by supplying the radiant energy to the electrode space with the aid of the driving means.

51. The method according to claim 50, characterized in that the additional switch, which is placed in a line between, a switching device and the object, and between the switching means and the object 1, is operated for interruption after that the overcurrent to or from the object has been reduced by means of the switching means.