RU2812748C2 - Multipolar electrical protection system and electrical unit containing such system - Google Patents

Abstract

FIELD: electrical protection system.

SUBSTANCE: multi-pole electrical protection system and an electrical unit containing such a system. Multi-pole electrical protection system (2), which includes many devices (4, 6, 8) for switching electric current. Each switching device has a plurality of compartments (18), each compartment containing an arc chute and a pair of detachable electrical contacts that are connected to the input (10) and output (12) connection terminals, wherein the detachable electrical contacts are movable between open and closed positions under the action of a tripping devices (20). The switching devices are separate from each other, while the input terminals (10) of each device are connected by a first connector (14) in order to maintain them at the same electrical potential, and the output terminals (12) of each device are connected by a second connector (16) in order to maintain them at the same electrical potential. The switching devices are controlled by the same common switching device (20).

EFFECT: providing higher speed and synchronization when switching, regardless of the number of poles.

13 cl, 5 dwg

Description

The present invention relates to a multi-pole electrical protection system and to an electrical installation containing such a system.

Electrical protection systems, such as circuit breakers, are switching devices that allow the electrical arc that may form when an electrical circuit is opened to be channeled and dissipated. When a circuit breaker is capable of breaking multiple electrical circuits corresponding to multiple electrical phases, also called poles, together, it is called a multi-pole circuit breaker.

Circuit breakers are generally designed for a given rating, i.e. for a given range of current and/or power.

However, changing requirements for circuit breakers, particularly due to wind power generation and the increase in the size of wind turbines, now require circuit breakers that are capable of handling very high amperage currents, in the range of up to 10 kA or even 12 kA. and in what is called the "low voltage" region, for example, between voltages that can reach from 690 V to 1200 V.

Traditional approaches for the production of modular circuit breakers no longer produce circuit breakers (circuit breakers) with acceptable speed, the increase in the number of elementary switching devices connected to each other causes problems in terms of volume and in terms of removal of heat flows created by such electrical currents with very high current.

It is to these problems that the invention addresses, more specifically, by providing a multi-pole electrical protection system with a compact and modular design, which has a high rating per pole, and whose tripping is synchronized regardless of the number of poles.

To this end, the invention relates to a multi-pole electrical protection system including a plurality of electrical current switching devices. Each switching device has a plurality of compartments, each compartment containing an arc chute and a pair of detachable electrical contacts that are connected to the input and output connecting terminals, the detachable electrical contacts being movable between open and closed positions under the action of a tripping device. According to the invention, the switching devices are separate from each other, while the input terminals of each device are connected by a first connector to maintain them at the same electrical potential, the output terminals of each device are connected by a second connector to maintain them at the same electrical potential and the switching devices are controlled by the same general disconnecting device.

By means of the invention, switching devices whose shutdown is timed can be placed so as to remove heat fluxes associated with large currents. Each switching device is classified according to the power and current associated with each pole. A common tripping device makes it possible to synchronize the tripping of each switching device with the others.

According to some advantageous but optional aspects of the invention, such an electrical protection system may combine one or more of the following features in any technically feasible combination:

- the first and second connectors of the switching device are located on the rear surface of the device, placed transversely one above the other, and each contains contact pads, each connected/connected to one of the input or output terminals, each bus contains the same number of contact pads as the switching device contains arc suppressors cameras;

- the first and second connectors of the switching device have the same design and are oriented in two opposite transverse directions, and the contact pads of the two connectors of the same device are each located in vertical planes that differ from each other;

- switching devices include the same number of arc chutes;

- each switching device contains two, three or four arc chutes;

- each arc chute of the switching device opens onto the upper surface of the switching device through a corresponding degassing opening, while the devices are spaced apart from each other in a direction orthogonal to the upper surface, so as to leave the degassing openings free from other devices;

- each switching device includes a switching mechanism for moving detachable contacts of said device, said switching mechanisms being connected to the disconnecting device;

- the disconnecting device forms part of an electronic control device, separate from the switching devices;

- the protection system includes housing bases for attachment to the electrical installation, each base containing electrical connections that are arranged to reversibly interact with the connectors of the switching device;

- the first switching device includes an actuator and a switching mechanism, the other switching devices are connected to the first switching device by a mechanical unit, which is located outside the devices and connects these devices to each other;

- the switching device, which includes the actuator, also includes a disconnecting device that operates the actuator;

- each switching device includes a common control shaft, to which detachable contacts are connected, and the shafts of each device are connected to a mechanical unit;

- the protection system contains a frame for connecting switching devices, while the frame and mechanical unit are made of non-ferromagnetic, preferably metallic, material.

The invention will be better understood and its other advantages will become more clearly apparent in the light of the following description of two embodiments of a multi-pole electrical protection system and electrical installation which are made in accordance with its principle, provided by way of example only and with reference to the accompanying drawings, in which :

Fig. 1 is a schematic view of a multi-pole electrical protection system according to some embodiments and, in particular, according to a first embodiment of the invention;

Fig. 2 is a perspective view of a multi-pole electrical protection system according to a second embodiment of the invention;

Fig. 3 is an enlarged view of part III in FIG. 2, with some parts hidden for ease of reading;

Fig. 4 is a perspective view of the security system of FIG. 2, if viewed along arrow IV in FIG. 2, with some of the parts hidden for ease of reading; And

Fig. 5 is an enlarged view of the protection system of FIG. 2, if viewed along arrow V in FIG. 4.

A multi-pole electrical protection system 2 according to a number of embodiments is shown in FIG. 1.

The protection system 2 contains a plurality of switching devices, for example three, here designated by references 4, 6 and 8.

Each of the switching devices 4-8 is an electrical switching device that is capable of interrupting electric current flowing through the detachable contacts and that can be switched between an open state and a closed state.

Advantageously, the switching devices 4-8 are, for example, existing circuit breaker subassemblies and/or contain existing low voltage circuit breaker components.

For example, the protection system 2 is intended for use in an electrical installation, such as an electricity distribution or generation installation. According to some examples, the electrical installation includes an electrical generator, at least one electrical load, and a switching device 2 connected between the generator and said electrical load. For example, the generator may be an air generator, in particular a wind turbine.

Switching devices 4-8 are separate from each other.

Preferably, the switching devices of system 2 are practically identical to each other and perform a similar function, so that, for simplicity, only one of these switching devices is described in detail in the following.

Each of the devices 4-8 is associated with an electrical pole or electrical phase, respectively designated by reference P4, P6 and P8.

In alternative embodiments, system 2 may include another number of switching devices. According to some examples, system 2 contains two switching devices. According to other examples, system 2 contains four switching devices. In this sense, protection system 2 is called multi-pole.

Each of the poles P4-P8 is connected to the input terminal 10 and to the output terminal 12. In the present description, the terms "input" and "output" are used to distinguish different elements of the protection system 2 and do not imply any particular direction of connection of the various elements of the protection system 2 .

For each of the devices 4-8, the input terminal 10 is connected to an input connector 14, which is installed on the corresponding device 4-8. Likewise, each output terminal 12 is connected to a corresponding output connector 16.

Each of the devices 4-8 contains a plurality of compartments 18. Advantageously, the devices 4-8 have the same number of compartments 18. In the illustrated example, each of the devices 4-8 contains three compartments 18.

Each of the compartments 18 contains an arc chute and a pair of detachable electrical contacts adjacent to the arc chute. In a broader sense, reference 18 relating to each of the compartments also includes an arc chute located in said compartment.

The detachable contacts of each pair are connected, respectively, to an input terminal or an output terminal, which are not shown. The detachable contacts are reversibly movable between open and closed positions.

For example, the separable contacts of each switching device 4-8 are connected to a control shaft common to the entire device. This shaft may be driven by a switching mechanism such as an energy storage mechanism. This mechanism can be activated by an actuator, such as an electromechanical actuator, in particular an electromagnetic actuator. In practice, this actuator may be driven by a tripping device 20.

When all the detachable contacts of one of the switching devices 4-8 are in the open/closed state, more generally the corresponding device 4-8 is also said to be in the open/closed state.

For each device 4, 6 and 8, the input terminals are connected to the same input connector 14 and are thus brought to the same electrical potential.

Likewise, for each device 4-8, the output terminals are connected to the same output connector 16 and are thus brought to the same electrical potential.

The switching devices 4-8 are connected to the same switching device 20. The switching device 20 is configured to receive and process information from each of the devices 4-8.

According to some examples, the switching device 20 may be an electronic switching device including an electronic circuit and/or a processor, particularly programmed to detect possible electrical failures based on information from each switching device 4-8, such as electrical current measurement values and/or voltage.

For example, the disconnecting device 20 is connected by data lines 22 to measuring devices 26 associated with switching devices 4-8. The disconnect device 20 is further connected by data lines 24 to one or more actuators associated with the switching devices 4-8 to switch their detachable electrical contacts between their open and closed states.

For example, measuring devices 26 may include one or more current sensors and/or voltage sensors and/or sensors configured to measure any suitable electrical quantity.

According to some examples, the trip device 20 forms part of an electronic control unit that is also configured to transmit switching commands, such as open, close, and reset commands, to each of the devices 4-8.

In particular, the trip commands sent by the trip device 20 are sent together to all switching devices 4, 6 and 8 of the protection system 2. In other words, the switching devices 4-8 are controlled by the same switching device 20.

According to some examples, a single shutdown device 20 is coupled to various devices 4, 6, and 8.

In the first embodiment, and as illustrated in FIG. 1, the disconnecting device 20 is different from the devices 4-8. The shutdown device 20 forms, for example, part of an electronic control unit, which is different from the devices 4-8.

In other words, the assignment of the switching devices 4-8 to the general switching device 20 is achieved electronically.

According to other examples, the disconnecting device 20 may be combined into one of the switching devices 4-8, wherein said one of the switching devices 4-8 that includes the disconnecting device 20 is then referred to as a “master” switching device, while the others switching devices that do not include a tripping device 20 are called "slave" switching devices.

It is not necessary, but nevertheless advantageous, that the switching devices 4-8 be removable, i.e. each of the switching devices 4-8 reversibly interacted with a corresponding housing base. More specifically, each housing base includes electrical connections that are reversibly electrically coupled to the input and output connectors 14 and 16 of the corresponding device 4-8 by simply sliding the devices 4-8 relative to the corresponding housing base in the direction of installation.

The devices 4-8 are thus easily removable and replaceable, for example when performing maintenance.

In this case, the data lines 22 and 24 themselves are also detachable, i.e. connection and/or disconnection of lines 22 and 24 occurs together with connection and/or disconnection of connectors 14 and 16 when installing/removing the switching device 4-8 to/from the corresponding housing base.

Fig. 2-5 illustrate a second embodiment of the security system 2.

In the second embodiment, these elements, which are similar to the elements in the first embodiment, have the same links plus 100, and operate in the same manner. For example, in FIG. 2-5, the protection system is indicated by reference 102. The system 102 includes three switching devices, indicated by references 104, 106 and 108, which correspond to switching devices 4, 6 and 8 of the first embodiment shown in FIG. 1. However, here again the number of switching devices is not limited and may differ.

The following will mainly describe the differences between the first and second embodiments.

The protection system 102 differs in particular from the protection system 2 in that the switching devices 104-108 are mechanically connected to each other so as to be controlled by the same tripping device 120, the latter performing a role similar or identical to that of the above-described tripping device 20.

In other words, the subordination of the switching devices 104-108 to the general tripping device 120 is achieved mechanically, for example, by means of a mechanical coupling block 124, which is described in more detail below.

Three switching devices 104-108 are mounted on a mounting frame 128. In the illustrated example, the frame 128 is formed from metal profiles connected to each other, for example, by welding. However, other embodiments of the frame 128 are possible. In the views of FIGS. 2-5, frame 128 is shown placed on a horizontal surface.

The rest of the description uses the terms "top", "bottom", "front", "behind", "side", "right", "left", etc. are given with reference to the orientation of elements of the security system 2 in the drawings, but do not imply, unless specifically stated otherwise, the specific operation of the system 2.

In fig. 3-5, frame 128 is shown in part for ease of reading. The frame 128 contains three receiving spaces 130, 132 and 134, which do not coincide with each other and which are configured to accommodate a corresponding switching device 104, 106 and 108, the devices 104-108 being thus separated. Each of the receiving spaces 130-134 herein includes a rectangular shaped horizontal plate, with the spaces 130-134 extending longitudinally parallel to each other.

Each of the switching devices 104-108 is attached to a corresponding receiving space 130-134 via flanges 136 and fasteners not shown.

Each of the switching devices 104-108 is generally parallelepiped shaped with a front surface 138. In the illustrated example, the front surfaces 138 are in a vertical plane, parallel to each other, and oriented in the same direction to facilitate use of the security system 102. The front surface 138 of the device 104 includes various controls and/or controls that are accessible to the operator to use the security system 102.

For convenience, the transverse plane P1 of the protection system 2 is defined as a plane parallel to the front surfaces 138 of the switching devices 104-108.

Additionally, the longitudinal plane P2 is defined as a vertical plane orthogonal to the transverse plane P1.

The switching device 104 is shown enlarged in FIG. 3, the cover for the front surface 138 is hidden for easy reading. The switching device 104 includes a plurality of compartments 118 that correspond to the compartments 18 described above with reference to FIG. 1. In the illustrated example, switching device 104 includes three compartments 118. Each compartment 118 includes an arc chute, not shown, adjacent to the detachable contacts. Each arc chute opens to the top surface 140 of the device 104 through a degassing opening 142, which serves to allow emergency gases to escape from the arc chutes.

The openings 142 are preferably oriented upward to facilitate the release of emergency gases. Advantageously, the switching devices 104-108 are spaced apart from each other in a direction orthogonal to the top surface 140 of each of the switching devices 104-108 so as to leave the degassing holes 142 of each of the switching devices 104-108 free and thereby preventing the switching device 104-108 from ability to block the opening 142 of another switching device 104-108. In the illustrated example, switching devices 104-108 are spaced apart from each other in the horizontal direction.

Each switching device 104-106 includes a control shaft 144 which is positioned transversely to the corresponding device 104-106 and which projects from the side surface 146 of the devices 104-108 by an end 148 of the shaft 144. The end 148 is therefore located outside the corresponding device 104-108. Separable contacts of the same switching device 104-108 are thus connected to a common shaft 144 and switch together between open and closed states under the action of the corresponding shaft 144.

More specifically, each of the shafts 144 has the shape of a cylinder centered on an axis about which the shafts 144 are rotatably movable relative to the corresponding device 104-108, and the detachable contacts of one of the switching devices 104-108 move between an open state and a closed state when the corresponding shaft 144 rotates. When all of the detachable contacts of one of the switching devices 104-108 are in an open/closed state, more generally the corresponding switching device 104-108 is also said to be in an open/closed state.

The control shafts 144 of each device 104-108 are connected to a mechanical coupling block 124. The mechanical block 124 includes a control rod 125, which is connected to each of the control shafts 144 through levers 150. The connection between the shaft 144, lever 150 and rod 125 is more clearly visible in FIG. . 3.

The lever 150 is attached at a first end to a shaft 144 proximate to the end 148 of the shaft 144, while the second end of the lever 150, opposite the first end, is connected to the rod 125 so as to rotate about an axis that is parallel to the axis of the corresponding shaft 144. Mechanical coupling block 124 is therefore located outside each of the devices 104-108.

The translational movements of the rod 125 are thus converted into rotational movements of the shaft 144. Since the shafts 144 of all switching devices 104-108 are connected by a mechanical unit 124, the rotational movements of one of the shafts 144 are copied by the other shafts 144, so that the detachable contacts located in each of the devices 104-108 move together between open and closed states. In other words, with the mechanical unit 124, the switching of the switching devices 104-108 between the open and closed states is simultaneous.

Advantageously, the frame 128 and the mechanical unit 124 are made of a non-ferromagnetic, preferably metallic, material to avoid the formation of an induction phenomenon under the influence of electric currents flowing through the protection system 2.

Preferably, a centering rod 152 and a guide 154 are provided to assist the mechanical assembly 124 to operate correctly, particularly by keeping the shafts 144 parallel and the ends 148 aligned to reduce friction in the mechanical assembly 124 and reduce the force required to rotate the shafts 144.

The centering rod 152 includes holes that receive bearings that accommodate the ends 148 of the shafts 144. The shafts 144 are thus directed to rotate relative to the rod 152 about their respective axis.

The guide 154 is connected to the flange 136 of each of the switch devices 104-108 on the side opposite the side surface 146. It is understood that the control rod 125, the centering rod 152 and the guide 154 extend longitudinally in directions that are parallel to each other, the switch devices 104-108 such aligned in the same direction. More specifically, the shafts 144 of the devices 104-108 are parallel to each other, in the same plane, and the connections between the arms 150 and the corresponding shafts 144 are aligned.

One of the switching devices 104-108 further includes a disconnecting device.

In the illustrated example, the tripping device 120 is mounted on the switching device 104, which is the switching device located at the bottom in FIG. 2-4. The disconnect device 120 is preferably located in a receptacle provided for this purpose on the face of one of the switch devices 104-108.

Alternatively (not shown), the shutdown device 120 is mounted on another of the switching devices 106 or 108, or even elsewhere, for example, on one of the switching devices 104-108.

In the illustrated example, switching device 104 also includes an actuator 156 shown in FIG. 2, with actuator 156 being driven by tripping device 120.

The actuator 156 is configured to receive a trip command from the disconnect device 120 and operate an energy storage mechanism, which is not shown, which mechanism rotates the shaft 144 of the device 104 so as to switch the detachable contacts of the device 104.

The rotational motion of the shaft 144 of the device 104 is transmitted through the mechanical block 124 to the shafts 144 of the other switching devices 106 and 108, separating the separable contacts of the devices 106 and 108.

In other words, the switching devices 104-108 are controlled by the same common shutdown device 120, which is located on or in the switching device 104 herein.

The breakaway contacts of the arc chute are connected to an input connector 114 and an output connector 116, which can be seen in FIG. 4 and 5.

In the illustrated example, connectors 114 and 116 are located on the rear surface 158 of each of the devices 104-108, with the rear surface 158 opposite the front surface 138.

Each of the input 114 and output 116 connectors includes a rectangular beam 160 and pads 162 that may be attached to or integrated into said beam 160. In the illustrated example, two beams 160 are shown transversely on the rear surface 158 of each of the devices 104-108, one over the other, with the beams 160 attached to the switching devices 104-108 by means of fasteners such as screws.

Each pad 162 includes a base 164, which is attached to a corresponding beam 160 by means of fasteners, and a mounting bus 166. The bus 166 here has the form of an elongated block placed vertically in length and protruding from the base 164. Each bus 166 includes through holes, which are designed to cooperate with other fastening elements of the electrical installation, these fastening elements not being shown.

Advantageously, the input 114 and output 116 connectors are of the same design, with the input 114 and output 116 connectors mounted in opposite directions on the rear surface 158 of the switching devices 104-108.

For convenience, direction D1 is defined as a horizontal direction located in the transverse plane P1 and oriented in the same direction as the side surface 146, i.e. to the right in Fig. 5. Similarly, the direction D2 is defined as the direction parallel to D1 and oriented in the opposite direction, i.e. to the left in Fig. 5.

Thus, in the example illustrated in FIG. 5, connectors 114 are oriented in direction D1, while connectors 116 are oriented in direction D2.

For example, output connector 116 is inverted (upside down) relative to input connector 114 such that pads 162 of input connector 114 are not aligned with pads 162 of output connector 116.

In this way, the mounting rails 166 of the pads 162 do not obstruct the circulation of air flow on the rear side of the device. This promotes, through natural convection, the removal of heat generated by the electrical current flowing at the level of each pad 162.

Of course, to assist in cooling the switching devices 104-108, a forced convection system using a fan may be provided.

For example, the mounting rails 166 of the same device 104-108 are thus located in vertical planes parallel to the planes P2, which are different from each other.

Advantageously, each input 114 and output 116 connector of the device 104-108 contains the same number of pads 162 as the corresponding device 104-108 contains arc chutes, with each pad 162 aligned with the corresponding arc chute on a plane parallel to the longitudinal plane P2.

In the illustrated example, each device 104-108 includes three arc chutes, while each of the connectors 114 and 116 includes three pads 162 that align with the three arc chutes of the corresponding device 104-108.

The presence of pads 162 that are connected to each of the arc chutes, these pads 162 being connected to each other by a beam 160, makes it possible to reduce the heating of the middle pad 162, i.e. that pad 162 that is located between two other pads 162 of the same connector 114 or 116, which is thus reduced relative to the situation in which the pads 162 were not connected to each other by the beam 160.

It is understood that, in the second embodiment of the protection system 102, the use of switching devices 104-108, which are separate from each other but controlled by the same common tripping device 120, makes it possible to maintain, in a relatively small volume, high currents through an efficient removal of heat and emergency gases.

Numerous aspects of the second embodiment may be implemented independently of the first embodiment. Likewise, the second embodiment may be implemented independently of the first embodiment.

In particular, the mechanical assignment of the switching devices to the disconnecting device can be realized independently of the electronic assignment.

Additionally, frame 128 can be used in the above-described security system 2 and is not exclusive to the second embodiment.

Moreover, the connectors 114 and 116, both in terms of their design and their arrangement, are not exclusive to the second embodiment and can be applied to the security system 2 of the first embodiment.

In general, in the various embodiments described above, only one switching device 20 or 120 is required to slave the switching devices 4-8 or 104-108. Thus, it is possible to produce protection systems 2 or 102 that exhibit higher switching performance while using switching devices incorporating existing low voltage circuit breaker components without the need to design specific new components, which is economically and industrially advantageous.

The embodiments and embodiments mentioned above may be combined with each other to create new embodiments of the invention.

Claims (17)

1. Multi-pole electrical protection system (2; 102), including many devices (4, 6, 8; 104, 106, 108) switching electric current, and each switching device has many compartments (18; 118), each containing an arc extinguishing device a chamber and a pair of detachable electrical contacts, which are connected to the input (10) and output (12) connecting terminals, and the detachable electrical contacts are movable between open and closed positions under the action of a disconnecting device (20; 120), characterized in that the switching devices are separate from each other, in that the input terminals (10) of each device are connected by a first connector (14; 114) in order to maintain them at the same electrical potential, in that the output terminals (12) of each device are connected by a second connector (16; 116) in order to maintain them at the same electrical potential, and the fact that the switching devices are controlled by the same general disconnecting device (20; 120). 2. Protection system (2; 102) according to claim 1, characterized in that the first and second connectors (14, 16; 114, 116) of the switching device (4, 6, 8; 104, 106, 108) are located on the rear surface (158) devices are arranged transversely one above the other, and each contains contact pads (162), each connected/connected to one of the input or output terminals, each bus contains the same number of contact pads as the switching device contains arc chutes (18; 118 ). 3. Protection system (2; 102) according to claim 2, characterized in that the first and second connectors (14, 16; 114, 116) of the switching device (4, 6, 8; 104, 106, 108) have the same design and oriented in two opposite transverse directions (D1, D2), the connecting pads of two connectors of the same device are each located in vertical planes that differ from each other. 4. Protection system (2; 102) according to any of the previous paragraphs, characterized in that the switching devices (4, 6, 8; 104, 106, 108) include the same number of arc chutes (18, 118). 5. Protection system (2; 102) according to the previous paragraph, characterized in that each switching device (4, 6, 8; 104, 106, 108) contains two, three or four arc extinguishing chambers (18, 118). 6. Protection system (2; 102) according to any of the previous paragraphs, characterized in that each arc chute of the switching device (4, 6, 8; 104, 106, 108) opens onto the upper surface (140) of the switching device through a corresponding hole ( 142) degassing, and in that the devices are spaced apart from each other in a direction orthogonal to the upper surface (140), so as to leave the degassing holes free from other devices. 7. Protection system (2) according to any of the previous claims 1 to 6, characterized in that each switching device (4, 6, 8) includes a switching mechanism for moving detachable contacts of said device, and said switching mechanisms are connected to a tripping device (20). 8. Protection system (2) according to the previous paragraph, characterized in that the disconnecting device (20) forms part of an electronic control device different from the switching devices (4, 6, 8). 9. Protection system (2) according to any one of claims 7 and 8, characterized in that the system includes housing bases designed for attachment to the electrical installation, each base containing electrical connections that are arranged to reversibly interact with the connectors (14, 16) switching devices (4, 6, 8). 10. Protection system (102) according to any one of claims 1-6, characterized in that the first switching device (104, 106, 108) includes an actuator (156) and a switching mechanism, other switching devices are connected to the first switching device mechanically block (124), which is located on the outside of the devices and connects these devices to each other. 11. Protection system (102) according to the previous paragraph, characterized in that the switching device (104, 106, 108), which includes an actuator (156), also includes a disconnecting device (120), which operates this actuator . 12. Protection system (102) according to any one of claims 10 and 11, characterized in that each switching device (104, 106, 108) includes a common control shaft (144), to which detachable contacts are connected, the shafts of each device connected to the mechanical block (124). 13. Protection system (102) according to any one of claims 10-12, characterized in that the system contains a frame (128) for attaching switching devices (104, 106, 108), and in that the frame and the mechanical block (124) are made made of non-ferromagnetic, preferably metallic, material.