Fusible link, fuse body, system and procedure

Abstract

Fusible link (1) with integrated measuring function, - with a protective housing (2) from which two electrical connection elements (3, 4) of the fuse (1) are brought out and in which at least one fusible link (5) is arranged, which electrically connects the two connection elements (3, 4) in the protective housing (2), - with a measuring device (10) which has a sensor element (11) for detecting a physical state measurement value of the fuse (1) and a transmission device (13) for transmitting the measurement value to a receiving device arranged outside the fuse (1), characterized in that - that the measuring device (10) has its own housing (12) in which the sensor element (11) is received and held and which is mechanically connected to the protective housing (2), wherein the total installation space required for the protective housing (2) and the further housing (12) corresponds to the installation space of a standardized NH fuse, wherein the measuring device (10) has a processing unit (14) for processing the measured value, which is arranged in the housing (12) and coupled to the sensor element (11) and the transmission unit (13), and wherein the processing unit (14) has a microprocessor or a microcontroller.

Description

[0001] The invention relates to a fuse with a protective housing from which two electrical connection elements are led and in which at least one fusible link is arranged, which electrically connects the two connection elements to each other, and to a measuring device comprising a sensor element for detecting a physical condition measurement value of the fuse and a transmission device for transmitting the measurement value to a receiving device arranged outside the fuse. The invention further relates to a fuse body for such a fuse, a system for monitoring the condition of an electrical circuit comprising at least one fuse, and a method for monitoring an electrical circuit with at least one such condition monitoring system.

[0002] Conductors carrying an electric current heat up. Excessively high currents can lead to excessive heating of the conductor, potentially melting the surrounding insulation and causing a cable fire. To prevent this fire hazard, an excessively high current, i.e., an overload current or a short circuit, must be interrupted promptly. This is ensured by an overcurrent protection device.

[0003] An example of such an overcurrent protection device is a fuse, which interrupts the circuit by melting one or more fusible links when the current in the circuit protected by the fuse exceeds a certain value for a specific period of time. The fuse consists of an insulating body with two electrical terminals that are electrically connected inside the insulating body by one or more fusible links. The fusible link, which has a smaller cross-section than the other conductors in the circuit, is heated by the current flowing through it and melts when the fuse's rated current is significantly exceeded for a predetermined period. Due to its good insulating properties, ceramic is most commonly used as the material for the insulating body.Such a fuse insert is, for example, known in principle from the European patent EP 0 917 723 B1 or the German patent applications DE 10 2014 205 871 A1 and DE 10 2016 211 621 A1.

[0004] Fuses are available in various designs. Besides simple appliance fuses, which consist of a simple glass cylinder containing the fusible link, there are also designs where the ceramic body is filled with sand – usually quartz sand. A distinction is made between types with solidified and unsolidified quartz sand. In a sand-solidified fuse, the fusible link is surrounded by quartz sand. The fuse housing typically consists of a ceramic body that contains the solidified sand, the electrical contacts, and the fusible link.The quartz sand acts as an arc-quenching medium: if the rated current of the fuse is significantly exceeded—for example, due to a high short-circuit current—the fuse trips. During this process, the fusible link first melts and then vaporizes due to the high temperature. This creates an electrically conductive plasma, which initially maintains the current flow between the electrical terminals—an electric arc forms. As the metal vapor from the vaporized fusible link condenses on the surface of the quartz sand grains, the arc is cooled. Consequently, the resistance inside the fuse increases to such an extent that the arc is finally extinguished. The electrical circuit protected by the fuse is thus interrupted.

[0005] In the field of fuses, low-voltage high-performance fuses, so-called NH fuses, as well as semiconductor protection fuses, so-called HLS fuses, such as those sold under the product name SITOR, are known in principle. NH fuses typically use one or more fusible links in the form of metal strips. These fusible links usually have so-called constriction rows for selective tripping of the fuse. Furthermore, at least one or more of the fusible links may have a solder deposit applied, which can be used to influence the overload characteristics of the fuse. The let-through energy value I, which is decisive for the tripping behavior of the fuse, is... 2 The t value is relatively large for NH fuses, which is why they have a rather sluggish characteristic.

[0006] If the fusible link heats up to a temperature above the melting point of the solder due to an electrical overload current, the solder diffuses into the fusible link material and forms an alloy with it. This increases the electrical resistance of the fusible link, leading to further heating. This accelerates the diffusion process until the fusible link in the vicinity of the solder deposit is completely dissolved, causing it to break and interrupting the current flow. In the case of a brief, permissible overcurrent, the NH fuse does not trip prematurely. However, if a short-circuit current occurs, the fusible link ruptures at the narrowing points. This creates several small arcs connected in series, whose voltages add up and thus lead to a faster tripping of the fuse.NH fuses are used, for example, to protect systems or control cabinets from fire, such as from overheated connecting cables.

[0007] Operators of electrical installations desire the ability to monitor the status of their systems. In the past, this was often achieved through visual inspection – for example, fuses were equipped with an indicator light that visually signals a tripped fuse on the outside of the fuse housing. However, there is a growing demand for this information to be accessible at any time and from any location, such as via a control room. Therefore, electrical installation devices are increasingly being equipped to provide information about their operating status. Electrical switching devices, such as arc fault circuit interrupters (AFCIs), which already possess their own control logic, can be adapted to process and provide this information with relatively little effort.

[0008] For fuses, there are solutions that use a communication module attachable to the fuse to receive and transmit the "tripped" information provided optically by the indicator light. However, attachable solutions have the disadvantage of requiring additional installation space and therefore can only be implemented in existing installations with relatively high effort. For simple retrofit applications, where an existing fuse without a communication module is replaced with a new fuse equipped with one, as part of an upgrade or modernization of the system, these attachable solutions are often not suitable because the necessary additional installation space is not available.

[0009] To solve this problem of limited installation space, which arises particularly in retrofit applications, international patent application WO 2017 / 078525 A1 describes a fuse in which a current sensor is integrated into the fuse's pressure body. This current sensor measures the current flow through the fuse during normal operation and transmits it to a sensing unit located outside the fuse. However, since relatively high temperatures can occur within a fuse, it is questionable how reliably a sensor integrated into the fuse's pressure body will function over the fuse's lifetime.

[0010] From the product catalog Jean Müller: “Fuses for low and high voltage” from 2010, a shortened fuse body with a pluggable transformer is known.

[0011] EP 1 116 252 B1 describes a high-current fuse with a housing made of electrically insulating material and, at longitudinally opposite ends of the same, a first electrical terminal and a second electrical terminal, which are electrically connected via a fusible link arranged in the housing, wherein the electrically conductive connection between the first electrical terminal and the second electrical terminal is made via a choke arranged in the housing and in series with the fusible link.

[0012] The invention is therefore based on the objective of providing a fuse, a fuse body, a system for monitoring the condition of an electrical circuit with at least one such fuse, and a method for monitoring an electrical circuit which has at least one condition monitoring system with at least one fuse, which at least partially overcome the aforementioned problems.

[0013] This problem is solved according to the invention by the fuse, the condition monitoring system, and the method for monitoring an electrical circuit according to the independent claims. Advantageous embodiments of the fuse and the fuse body according to the invention are the subject of the dependent claims.

[0014] The fuse according to the invention comprises a protective housing from which two electrical connection elements of the fuse extend and in which at least one fusible link is arranged, which electrically connects the two connection elements within the protective housing. Furthermore, the fuse comprises a measuring device which includes a sensor element for detecting a physical condition measurement of the fuse and a transmission device for transmitting the measurement value to a receiving device located outside the fuse. The measuring device has its own housing in which the sensor element is received and held, and which is mechanically connected to the protective housing, wherein the total installation space required for the protective housing and the additional housing corresponds to the installation space of a standardized NH fuse.

[0015] The protective housing, which can also be called a pressure housing or pressure body, serves to absorb the pressure that occurs when the device heats up or a safety device is triggered. Therefore, high demands are placed on the mechanical strength and stability of the protective housing. In contrast, the housing of the measuring device serves to hold and secure the sensor element and protect it from external influences such as moisture and / or dirt. Consequently, significantly lower demands are placed on the mechanical stability of this housing.

[0016] The two housings are mechanically connected. This connection can be fixed but detachable, for example, in the form of a screw connection. However, it is also possible to form the protective housing and the housing of the measuring device as a single piece, with the section corresponding to the protective housing possessing the required mechanical stability of a pressure housing. The essential aspect of the invention, however, is that the total installation space occupied by the protective housing and the housing of the measuring device corresponds to the predefined installation space of a standardized NH fuse, with the measuring device now additionally integrated within this installation space. In this way, the fuse can also be used for retrofit applications in the context of upgrading or modernizing existing systems where a conventional fuse without a measuring device is replaced.

[0017] The measuring device is designed to acquire a physical state measurement of the fuse, i.e., a physical measurement value that characterizes the operating state of the fuse, and to transmit this value to the receiving device located outside the fuse using the transmission device. For this purpose, electrical measurements such as electric current and / or electric voltage, as well as other physical measurements such as the temperature of the fuse, are suitable. In this way, it is not only possible to make a digital statement as to whether the fuse has blown or not. Rather, by measuring the current temperature of the fuse, it is also possible to determine whether the fuse will blow shortly or not.the current condition of the fuse and, accordingly, its remaining lifespan.

[0018] In an advantageous further development of the fuse, the measuring device has an additional sensor element for detecting another physical state measurement value of the fuse.

[0019] With the aid of the additional sensor element, another physical state measurement of the fuse – for example, current and voltage – can be acquired and transmitted to the receiving device located outside the fuse. In this way, the current operating state of the fuse can be determined more precisely. The additional sensor element can also be housed within the measuring device.

[0020] In a further advantageous embodiment of the fuse, the transmission device is also arranged within the housing of the sensor element. The transmission device can either be located in the cavity enclosed by the housing of the sensor element, or it could be fully or partially integrated into the housing wall. In this way, a compact fuse can be realized.

[0021] In one embodiment of the fuse according to the invention, the measuring device for processing the measured value further comprises a processing unit, which is also arranged in the housing of the sensor element and coupled to the sensor element and the transmission unit. The processing unit is electrically coupled to both the sensor element and the transmission unit. This coupling can be electrically conductive, i.e., wired, but also wireless, for example via radio.

[0022] In one embodiment of the fuse according to the invention, the processing unit comprises a microprocessor or a microcontroller. Advantageously, the processing unit comprises a microprocessor or a microcontroller which enables processing, for example, aggregation of the acquired measurement data and only sends a corresponding signal to the transmission unit when a predefined condition is met, in order to transmit this signal to the receiving device located outside the fuse. This significantly reduces the data volume.

[0023] In a further advantageous development of the fuse, the sensor element is designed to detect a current measurement value of the fuse and for this purpose includes a current transformer or a Hall effect sensor.

[0024] A Rogowski coil, for example, can be used as a current transformer. This is a toroidal air-core coil without a ferromagnetic core and is used, among other things, to measure alternating current. The Rogowski coil is also known as a "Rogowski current transformer." A Hall effect sensor, also called a Hall sensor, Hall probe, or Hall encoder, utilizes the Hall effect to measure magnetic fields: when a simple Hall sensor carries a current and is placed in a magnetic field perpendicular to it, it delivers an output voltage that is proportional to the product of the magnetic flux density and the current. Both a current transformer and a Hall effect sensor are suitable sensor elements for this application due to their small size.

[0025] In a further advantageous development of the fuse, the sensor element is designed to detect a temperature measurement value of the fuse.

[0026] Measuring the temperature inside a fuse not only reveals whether the fuse has already tripped, but also allows for a prediction of whether it will trip soon. This provides the opportunity to intervene before the fuse trips, if necessary. Furthermore, this information is extremely helpful for planning preventative maintenance.

[0027] In a further advantageous embodiment of the fuse, the measured value is transmitted wirelessly from the transmission device to the receiving device. For wireless transmission of the measured value from the transmission device to the receiving device, transmission methods such as Bluetooth, RFID (both active and passive), Zigbee, etc., are suitable.

[0028] In a further advantageous development of the fuse, the measuring device is designed to be energy self-sufficient. This means that the measuring device operates without an external power source. The energy required to transmit the measurement signal is then supplied, for example, via a current transformer, passive RFID, or a dedicated battery. This significantly simplifies the retrofitting of existing systems.

[0029] In a further advantageous embodiment of the fuse, one of the two connection elements passes through the housing of the measuring device. Particularly when using a current transformer, a torus-shaped housing, which is attached to one of the two connection elements of the fuse, represents a space-saving solution for integrating the measuring device into the fuse.

[0030] The inventive safety body for a fuse of the type described above has a first receiving space designed to receive the fuse element and a second receiving space designed to receive the measuring device, which is spatially separated from the first receiving space, wherein the second receiving space forms a structural unit with the first receiving space.

[0031] The first receiving chamber of the fuse body is pressure-resistant, meaning it is designed to withstand the pressure generated when the fuse is triggered, and thus constitutes the pressure body of the fuse. The second receiving chamber, on the other hand, merely serves as a protective element for the measuring device and is subject to significantly lower requirements regarding its mechanical stability and strength. The first and second receiving chambers form a single structural unit; that is, the two bodies do not need to be assembled separately when replacing or installing the fuse, as they are already permanently connected, thus considerably simplifying the installation process.

[0032] In a further advantageous development, the first and second receiving spaces form a single-piece locking element. Particularly with regard to the manufacturing of the locking element using an additive manufacturing process, colloquially also referred to as "3D printing," a single-piece design of the locking element is advantageous, as it eliminates subsequent assembly steps. This further reduces the manufacturing costs of the locking element.

[0033] In a further advantageous embodiment, the one-piece locking element is made of a ceramic material or a thermostable plastic. Ceramic materials are particularly suitable for manufacturing a locking element due to their high compressive strength. Thermostable plastics, provided they are sufficiently heat-resistant, are characterized by their simplified processing and comparatively low manufacturing costs.

[0034] In a further advantageous embodiment of the fuse body, the first and second receiving chambers are permanently but detachably connected. This offers the advantage that, after the fuse has tripped, the second receiving chamber, which houses the measuring device, can potentially be reused. This is particularly relevant when the material and manufacturing costs of the measuring device are comparatively high compared to the rest of the fuse.

[0035] In a further advantageous development of the locking mechanism, the first and second receiving chambers are made of different materials. This allows both receiving chambers to be adapted to the different requirements placed upon them.

[0036] In a further advantageous development of the security structure, the receiving compartments, which are combined into a single structural unit, are surrounded by an additional shell. This additional shell, which can be made of paper or a plastic coating, for example, emphasizes the structural unity of the security structure.

[0037] The system according to the invention for monitoring the condition of an electrical circuit comprises at least one fuse of the type described above. Furthermore, the system comprises a receiving device which is arranged outside the fuse and is designed to receive a measured value transmitted by the transmission device.

[0038] Using the condition monitoring system for an electrical circuit, at least one physical condition measurement of the fuse is transmitted via the fuse's transmission device to the receiving device – for example, a control room. In this way, monitoring the condition of the fuse is possible even remotely.

[0039] The inventive method for monitoring an electrical circuit, which has at least one condition monitoring system of the type described above with at least one fuse, consists of the following steps: a) Measuring a physical value of the fuse using the measuring device; b) Transmitting the physical measured value by means of the transmission device to a receiving device of the system located outside the fuse; c) Further processing of the transmitted measurement value.

[0040] Regarding the advantages of the inventive method for monitoring an electrical circuit with at least one condition monitoring system of the type described above, reference is made to the preceding explanations concerning the advantages of the inventive fuse and the inventive fuse body. With regard to the transmission of the physical measured value formulated in step b), it should be noted that this includes both the transmission of the pure measured values, i.e., the raw data, and the transmission of measured values ​​preprocessed by the processing device – for example, aggregated or compressed.

[0041] The following section explains an exemplary embodiment of the fuse and the fuse body in more detail with reference to the accompanying figures. The figures show: Fig. 1 a schematic representation of an NH fuse known from the prior art; Fig. 2 a schematic representation of the fuse according to the invention.

[0042] In the various figures of the drawing, identical parts are always marked with the same reference symbol. This description applies to all figures in the drawing in which the corresponding part is also recognizable.

[0043] Fig. Figure 1 schematically shows the basic structure of a standardized NH fuse, as already known from the prior art. The fuse 1 has two terminal elements 3, which are made of an electrically conductive material, for example, copper. In the illustrations, the terminal elements 3 are designed as blade contacts – however, this is not essential to the invention. The terminal elements 3 are mechanically firmly and tightly connected to a protective housing 2, which is made of a solid, non-conductive, and preferably heat-resistant material, for example, a ceramic, and serves as a pressure body for the fuse 1. The protective housing 2 generally has a tubular or hollow cylindrical shape and is sealed pressure-tight to the outside, for example, by means of two sealing caps 4.The connecting elements 3 each extend through an opening formed in the end caps 4 into the cavity of the protective housing 2. In this cavity, at least one so-called fusible link 5 is arranged, which electrically connects the two connecting elements 3 to each other.

[0044] The remaining cavity is usually completely filled with an extinguishing agent 6, which serves to extinguish and cool the fuse 1 in the event of tripping and completely surrounds the fusible link 5. Quartz sand, for example, is used as the extinguishing agent 6. Instead of the in Fig. In addition to the single fusible link 5 shown in Figure 1, it is also possible to arrange several fusible links 5 in parallel within the protective housing 2 and connect them accordingly to the two contact elements 3. The type, number, arrangement, and design of the fusible links 3 can influence the tripping characteristic – and thus the tripping behavior – of the fuse 1.

[0045] The fusible link 5 is generally made of a highly conductive material such as copper or silver and has several rows of constrictions 7 and one or more solder deposits 8 – so-called solder points – along its length, i.e., in its longitudinal direction L. The tripping characteristic of the fuse 1 can also be influenced and adapted to the specific application via the rows of constrictions 7 and the solder points 8. At currents lower than the rated current of the fuse 1, only enough power is dissipated in the fusible link 5 to be quickly released to the outside as heat via the quenching sand 6, the protective housing 2, and the two terminal elements 3. The temperature of the fusible link 5 does not rise above its melting point.If a current flows that is within the overload range of the fuse 1, the temperature inside the fuse 1 continues to rise steadily until the melting point of the fusible link 5 is exceeded and it melts through at one of the constriction rows 7. In the case of high fault currents – such as those occurring due to a short circuit – so much energy is dissipated in the fusible link 5 that it is heated along virtually its entire length and consequently melts simultaneously at all constriction rows 7.

[0046] Since liquid copper or silver still exhibits good electrical conductivity, the current flow is not interrupted at this point. The molten material formed in the fusible link 5 is therefore heated further until it finally transitions into a gaseous state, forming a plasma. This creates an electric arc to maintain the current flow across the plasma. In the final stage of a fuse trip, the conductive gases react with the extinguishing agent 6, which in conventional fuses 1 usually consists of quartz sand. Due to the extremely high temperatures in the vicinity of the arc caused by the electric arc, this sand melts, leading to a physical reaction between the molten fusible link material and the surrounding quartz sand 6. Since the resulting reaction product is electrically non-conductive, the current flow between the two terminal elements 3 rapidly drops to zero.However, it must be noted that a certain mass of fusible link material also requires a corresponding mass of extinguishing agent. Only in this way can it be ensured that sufficient extinguishing agent 6 is still present at the end of the fuse shutdown to effectively contain all the conductive plasma.

[0047] In Fig. Figure 2 shows a schematic representation of the fuse 1 according to the invention. The fuse has a protective housing 2 and a further housing 12, which are arranged one behind the other in the longitudinal direction L and together have the height H of a standardized NH fuse (as found in Fig. (1) is shown. In the further housing 12, a measuring device 10 is arranged, which has a sensor element 11 for detecting a physical state measurement value of the fuse 1 and a transmission device 13 for transmitting the measured value to a receiving device (not shown) arranged outside the fuse 1. The sensor element 11 is designed here as a current transformer for measuring an electric current I flowing through the fuse 1; alternatively or additionally, other sensor elements, for example a Hall sensor or a temperature sensor, are also suitable for this purpose.

[0048] However, what is essential to the invention is that the measuring device has its own housing 12 in which the at least one sensor element is received and held, and which is mechanically connected to the protective housing - in which in Fig. In the embodiment shown in Figure 2, the fuse is fastened by means of a screw 9, although other fasteners are also suitable. The total installation space required for the protective housing 2 and the further housing 12 is the same as that of a standardized NH fuse. In other words, the total installation space occupied by the protective housing 2 and the further housing 12 corresponds to the predefined installation space of a standardized NH fuse, with the measuring device now integrated within this space in addition to the actual fuse. In this way, the fuse 1 according to the invention can also be used for retrofit applications in the context of upgrading or modernizing existing electrical systems, where a conventional fuse without a measuring device is to be replaced by the fuse according to the invention.

[0049] Consequently, the fusible link 1 according to the invention has the same height H in its longitudinal direction L as the one in Fig. 1 represented a standardized NH fuse. However, in the fuse according to the invention 1, the height H is divided into a first section with a first height H. D as well as a second section with a second height H M up. With the first height H D The height of the pressure body 2, i.e., the actual protective body 2 of the fuse 1, is designated as the second height H. M This refers to the height of the second housing 12, in which the measuring device 10 is arranged. Significantly lower requirements are placed on this housing with regard to its mechanical stability.

[0050] The sensor element 11 is connected to the processing unit 14, which is located in the Fig. In the exemplary embodiment shown in Figure 2, a circuit board is schematically depicted, which is equipped with components suitable for processing the measurement signal and is electrically connected. Likewise, the transmission device 13 is electrically connected to the processing device 14, which is also depicted as a circuit board. The transmission device 13 can, for example, be an RFID module, whereby both active and passive RFID solutions are suitable. Other transmission technologies – advantageously wireless – such as Bluetooth or Zigbee are also suitable. In the illustration in Fig. In the embodiment shown in Figure 2, the transmission device 13 is integrated into the wall of the further housing 12. This has the advantage that the transmission power can be significantly lower than with a transmission device 13 arranged inside the housing 12, although an arrangement inside the housing is also possible. Reference symbol list 1 fuse 2 Protective housings / pressure bodies 3 Connection element 4 Cap 5 fusible links 6 extinguishing agents 7 narrow passages 8 Lotdepot 9 screw 10 Measuring device 11 Sensor element 12 cases 13 Transmission device 14 Processing unit H height L Longitudinal direction

Claims

[1] Fusible link (1) with integrated measuring function, - with a protective housing (2) from which two electrical connection elements (3, 4) of the fuse (1) are brought out and in which at least one fusible link (5) is arranged, which electrically connects the two connection elements (3, 4) in the protective housing (2), - with a measuring device (10) which has a sensor element (11) for detecting a physical state measurement value of the fuse (1) and a transmission device (13) for transmitting the measurement value to a receiving device arranged outside the fuse (1), characterized by , - that the measuring device (10) has its own housing (12) in which the sensor element (11) is received and held and which is mechanically connected to the protective housing (2), wherein the total installation space required for the protective housing (2) and the further housing (12) corresponds to the installation space of a standardized NH fuse, wherein the measuring device (10) has a processing unit (14) for processing the measured value, which is arranged in the housing (12) and coupled to the sensor element (11) and the transmission unit (13), and wherein the processing unit (14) has a microprocessor or a microcontroller. [2] Fusible link (1) according to claim 1, characterized by , that the measuring device (10) has a further sensor element (11) for detecting a further physical state measurement value of the fuse (1). [3] Fusible fuse (1) according to any one of the preceding claims, characterized by, that the transmission device (13) is also arranged in the housing (12) of the sensor element (11). [4] Fusible fuse (1) according to any one of the preceding claims, characterized by , that the sensor element (11) is designed to detect a current measurement value of the fuse (1) and for this purpose has a current transformer or a Hall effect sensor. [5] Fusible fuse (1) according to any one of the preceding claims, characterized by , that the sensor element (11) is designed to detect a temperature measurement value of the fuse (1). [6] Fusible fuse (1) according to any one of the preceding claims, characterized by , that the transmission of the measured value from the transmission device (13) to the receiving device is wireless. [7] Fusible fuse (1) according to any one of the preceding claims, characterized by , that the measuring device (10) is designed to be energy self-sufficient. [8] Fusible fuse (1) according to any one of the preceding claims, characterized by , that one of the two connection elements (3, 4) passes through the housing (12) of the measuring device (10). [9] Safety element for a fuse (1) designed according to any one of claims 1 to 8, - with a pressure-tight first receiving chamber designed to receive the fusible link (5), and - with a second recording space designed to accommodate the measuring device (10), spatially separated from the first recording space and having lower mechanical stability, - whereby the second recording room forms a structural unit with the first recording room. [10] Security body according to claim 9, wherein the first receiving space and the second receiving space form a one-piece security body. [11] Locking element according to claim 10, wherein the one-piece locking element is formed from a ceramic material. [12] Security body according to claim 9, wherein the first receiving space and the second receiving space are firmly but detachably connected to each other. [13] Security body according to claim 12, wherein the first receiving space and the second receiving space are formed from different materials. [14] Security body according to one of the preceding claims, wherein the receiving spaces combined to form a structural unit are surrounded by an additional shell. [15] System for monitoring the condition of an electrical circuit, - with at least one fuse (1) according to any one of the preceding claims 1 to 8, - with a receiving device which is arranged outside the fuse (1) and is designed to receive a measured value transmitted by the transmission device (13). [16] Method for monitoring an electrical circuit comprising at least one condition monitoring system according to claim 15 with at least one fuse (1) according to any one of claims 1 to 8, comprising the steps: - Measuring a physical measured value of the fuse (1) using the measuring device (10); - Transmitting the physical measured value by means of the transmission device (13) to a receiving device of the system arranged outside the fuse (1); - Further processing of the transmitted measurement value.

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