Monitoring device and method for monitoring a surge protection device and assembly

Abstract

The invention relates to a monitoring device (14) for monitoring a surge protection device (12). The monitoring device (14) has a connection (17) for the surge protection device (12). The monitoring device (14) has overload protection (20) and a detection circuit (26) configured to detect a parameter indicative of a defect and / or degradation of the surge protection device (12). A tripping element (30) is also provided, which can be activated by means of the detection circuit (26). The monitoring device (14) has a thermal disconnect device (28) that is thermally coupled to the tripping element (30). Furthermore, a method for monitoring a surge protection device (12) and an assembly (10) are described.

Description

[0001] The invention relates to a monitoring device for monitoring a surge protection device, in particular for detecting a defect in the surge protection device. Furthermore, the invention relates to a method for monitoring a surge protection device using a monitoring device, in particular for detecting a defect in the surge protection device. In addition, the invention relates to an assembly comprising a surge protection device and a monitoring device.

[0002] Surge protection devices are well-known and used in a wide variety of applications. One major area of ​​application for surge protection using such devices is at electrical power supply points in buildings or in branched power distribution systems.

[0003] Surge protection devices (SPDs), also known as surge protection devices, function by becoming low-impedance in the event of a transient or temporary overvoltage to dissipate the energy of the surge pulse. Overloads and operating conditions outside the specified ratings of the surge protection devices can lead to their failure. Typically, a failed surge protection device results in a permanently low-impedance condition, causing upstream protective devices (overcurrent protection - OCP) such as fuses or miniature circuit breakers (MCBs) to trip. To prevent a complete power outage due to overcurrent tripping in the power distribution system, additional (pre-)fuses are installed downstream of the surge protection device if necessary.

[0004] However, dimensioning these (pre-)fuses is complicated, as two criteria must be met, which make correct dimensioning difficult.

[0005] On the one hand, the (pre-)fuses must not be undersized to prevent impulse currents from tripping, and on the other hand, they must not be oversized to avoid damaging a faulty surge protection device due to high thermal stress. Generally, such (pre-)fuses are designed to trip at currents in the kiloampere range.

[0006] Surge protection devices incorporate surge protection elements, which can vary in design depending on the application. For example, varistors (MOVs) are used for surge protection types 2 and 3, while gas discharge tubes or spark gaps are typically used for surge protection type 1. However, the surge protection elements in these devices can degrade over time, resulting in leakage current. This degradation means that the surge protection device, which initially exhibits a high internal resistance when operating at mains voltage, will have a lower internal resistance due to the degradation process.The decreasing electrical resistance and the associated increase in leakage current lead to increased power dissipation in the surge protection device, which in turn can accelerate the degradation of the surge protection element. As a consequence, thermal destruction due to high leakage currents can occur, a so-called thermal runaway.

[0007] From DE 10 2024 105 682 A1, a monitoring device for monitoring a surge protection device is known, which has a detection circuit that is designed to detect a parameter that is indicative of a defect and / or degradation of the surge protection device.

[0008] DE 32 28 471 A1 describes a surge protection device consisting of at least one varistor and a spark gap connected electrically in parallel to it.

[0009] In DE 10 2013 202 796 A1 a disconnect device for a surge protection device is shown.

[0010] From DE 10 2015 008 136 A1 a switching device for surge protection devices is known which comprises mechanically pre-tensioned, impulse current-capable switching elements.

[0011] DE 10 2008 029 670 B4 shows a surge protection element.

[0012] The object of the invention is to provide a cost-effective and easy-to-implement way to detect and safely disconnect a degraded or defective surge protection device in order to protect it.

[0013] The problem is solved according to the invention by a monitoring device for monitoring a surge protection device. The monitoring device has a connection for the surge protection device. The monitoring device has overload protection, for example, a short-circuit current quenching and / or surge-switching component. The monitoring device has a detection circuit configured to detect a parameter that is indicative of a defect and / or degradation of the surge protection device, in particular a leakage current-related parameter. The monitoring device has a tripping element that can be activated by means of the detection circuit. Furthermore, the monitoring device has a thermal disconnect device that is thermally coupled to the tripping element.

[0014] Furthermore, the problem is solved according to the invention by a method for monitoring a surge protection device by means of a monitoring device, wherein the method comprises the following steps: - Recording a parameter that is indicative of a defect and / or degradation of the surge protection device, in particular a leakage current-related parameter, - Activation of a tripping element when the parameter has a value that is associated with degradation and / or a defect of the surge protection device, wherein the tripping element is arranged in a current path and thermally coupled to a thermal disconnect device, and - Separation of the object to be monitored using the thermal separation device.

[0015] The basic idea of ​​the invention is to increase the dielectric strength when the surge protection device being monitored by the monitoring device is no longer fully functional, i.e., degraded or defective. For this purpose, the relevant parameter is recorded and evaluated; that is, a value of the parameter is determined that is representative of degradation and / or a defect in the surge protection device. In this state, the tripping element in the monitoring device is activated, so that at least a partial current flows through the tripping element, thereby converting electrical energy at least partially into thermal energy (heat). The heat thus generated can then trigger a thermal disconnect device, which is thermally coupled to the tripping element, thus disconnecting the monitored surge protection device.

[0016] This results in a simply designed monitoring device that combines several functions. Specifically, the monitoring device ensures current limiting and the extinguishing of short-circuit currents thanks to its overload protection. Furthermore, the monitoring device is configured to detect a defect or degradation of the downstream monitoring device using its detection circuit. This is achieved by recording an indicative parameter, particularly a leakage current-related parameter, which thus provides an indication of a defect or degradation of the surge protection device. A defect or degradation of the surge protection device can be accompanied by a leakage current within the device, which can be detected accordingly. In addition, the monitoring device safely disconnects the surge protection device in the event of a previously detected degradation or degradation.a previously detected defect in the surge protection device. This increases the voltage withstand capability accordingly.

[0017] In general, the thermal isolation device is designed to create a galvanic isolation of the surge protection device, i.e., to galvanically isolate the surge protection device from the monitoring device, which remains connected to the current-carrying conductor.

[0018] The monitoring device and the surge protection device are, for example, two separate devices, each with its own housing. The connection for the monitoring device is located on the outside of its housing, allowing for easy connection to the surge protection device.

[0019] Alternatively, the monitoring device and the surge protection device can also be housed in a single enclosure, i.e., in a single protective device. In this case, the monitoring device and the surge protection device can also be referred to as a monitoring module and a surge protection module, respectively.

[0020] One aspect of the design is that the detection circuit is configured to evaluate the parameter in order to determine degradation and / or a defect in the surge protection device. For this purpose, the detection circuit can compare the detected parameter, particularly the leakage current-related parameter, with at least one threshold value. This threshold value can be indicative of a specific degree of degradation of the surge protection device. In principle, several threshold values ​​can be provided, each indicative of different degrees of degradation. Using this threshold value, the degree of degradation of the surge protection device can be determined, for example, low degradation (slight aging), medium degradation (moderate aging), or high degradation (significant aging).For the different levels of degradation that can be detected, a corresponding threshold value should be provided for each, so that there are several threshold values ​​in total.

[0021] Furthermore, a threshold value may be specified, serving as a limit value, whereby the threshold value is indicative of a defect in the surge protection device. The threshold value thus represents an absolute limit that is relevant to the functioning of the surge protection device. If the threshold value is reached, the surge protection device is considered defective. Should the threshold value be reached unexpectedly, the monitoring device can initiate appropriate measures to take the surge protection device out of service, for example, by disconnecting it.

[0022] Another aspect is that the thermal isolation device is positioned between the overload protection and the connection. The thermal isolation device thus ensures that the surge protection device, which is connected to the monitoring device, can be safely disconnected, thereby eliminating any galvanic connection.

[0023] In one respect, the tripping element is a resistor that is thermally coupled to the thermal disconnect device. The resistor can be switched on as needed. If a current flows through the resistor, the current is limited and the electrical power loss is converted into heat. Due to the thermal connection to the thermal disconnect device, this heat causes the thermal disconnect device to trip and disconnect the surge protection device.

[0024] The monitoring device may include a switch controlled by the detection circuit, allowing current to flow through a current path in which the tripping element is located. The detection circuit activates the switch when it detects degradation or a defect in the surge protection device, i.e., when the (leakage current-related) parameter has reached at least one threshold value. This ensures that thermal disconnection can occur early via the thermal disconnect device.

[0025] The current path can be connected in parallel to the overload protection. In other words, the overload protection is bypassed via the current path, so that in the event of an overvoltage, especially a small but prolonged overvoltage (i.e., not a voltage pulse), the current flows through the connected current path. The resulting electrical energy is converted into heat, which can be used to (prematurely) trigger the thermal disconnect device.

[0026] According to one embodiment, the thermal disconnect device comprises at least two electrical conductors which, in an initial state, are electrically connected to a solder material. The solder material also provides a mechanical connection between the at least two electrical conductors to ensure current flow through them. The current is thus conducted through the two electrical conductors and the solder material, which can heat up as a result. However, the thermal disconnect device can be designed such that, at a low current, for example, a low leakage current, the solder material does not soften to the point of breaking the connection.Only with a higher current and the associated additional heat input via the triggering element, which is thermally coupled to the thermal disconnect device, is the heat input so great that the thermal disconnect device triggers and disconnects the surge protection device.

[0027] In particular, the solder material is a low-temperature solder material. This ensures that the thermal disconnect device still reacts early, provided a corresponding current flow is present via the triggering element.

[0028] The thermal disconnect device may also include a disconnector, in particular a spring-loaded disconnector. The disconnector may be wedge-shaped. The disconnector assists in the separation of the thermal disconnect device, in particular the separation of the at least two electrical conductors. For this purpose, the disconnector can be pressed between the two electrical conductors by a spring to separate them, provided that the solder material which mechanically connects the two electrical conductors in their initial state has already softened. Preferably, the disconnector has a point or is wedge-shaped to facilitate the separation of the two electrical conductors when the disconnector is inserted between them. The spring may be pre-tensioned, and the spring is released when degradation and / or a defect in the surge protection device is detected by the detection circuit.The detection circuit can release a safety device on the pre-tensioned spring, which secures the spring in the pre-tensioned state.

[0029] Overload protection can include a spark gap, a gas discharge tube, and / or a power electronic component. Specifically, the power electronic component is a thyristor, a TRIAC (Triode for Alternating Current), or a DIAC (Diode for Alternating Current). Typically, a spark gap is used as a short-circuit current quenching and / or overvoltage-switching component. If the monitoring device is solely for monitoring the overvoltage protection device, the short-circuit current quenching and / or overvoltage-switching component can also be a gas discharge tube and / or a power electronic component.

[0030] The detection circuit includes at least one status indicator and / or a communication interface. The status indicator allows the status of the monitoring device and / or the surge protection device to be displayed directly on the monitoring device itself. The communication interface also enables the transmission of this information to a separate device and / or a control center, so that the status can be accessed at a location other than where the monitoring device is installed. In general, the status of the surge protection device and / or the monitoring device can be displayed or transmitted.

[0031] The detection circuit can be configured to control a display mode (status indicator) that depends on the degradation of the surge protection device. This can involve controlling a color, brightness, and / or flashing frequency. The different display modes ensure that the user is clearly informed about the degree of degradation of the surge protection device, allowing them to quickly and intuitively recognize the extent of the degradation. Green, yellow, and red are typical indicator colors used to visually represent the degree of degradation. Similarly, the flashing speed can intuitively indicate the degree of degradation, for example, slow flashing for low degradation and fast flashing for high degradation.A continuous light can indicate a defective surge protection device, i.e., when the limit value has been exceeded.

[0032] Furthermore, a module is provided that includes a surge protection device and a monitoring device of the aforementioned type. The surge protection device and the monitoring device are connected in series. The aforementioned advantages and properties apply analogously to the module. The module can be a protective device, as previously explained.

[0033] The basic functionality of the assembly, i.e., the monitoring device and the downstream surge protection device, is that the monitoring device protects the surge protection device.

[0034] Accordingly, the monitoring device is a fuse for the surge protection device, with the monitoring device and the surge protection device connected in series. It is therefore possible that the monitoring device replaces a previously used (pre-)fuse. Consequently, the monitoring device can also be considered a (pre-)fuse.

[0035] This is important because the monitoring device also solves the aforementioned problem of correctly sizing the (pre-)fuse of the surge protection device. Furthermore, the monitoring device can be adapted to the different technologies of surge protection devices or configured accordingly. This is preferably done by the manufacturer.

[0036] The early detection of degradation of the surge protection device made possible by the monitoring device also offers the advantage of reducing potential downtime, as the surge protection device can be replaced before it fails due to excessive degradation or a defect.

[0037] Since the monitoring device has overload protection, i.e., the short-circuit current-extinguishing and / or over-voltage-switching component, the monitoring device is basically designed to extinguish or interrupt a fault and / or short-circuit current of a few amperes up to the maximum short-circuit current.

[0038] The following cases must be distinguished: The surge protection device is fundamentally intact. When a surge occurs, the overload protection device forwards the incoming surge pulse to the downstream surge protection device. The surge protection device then properly dissipates the surge.

[0039] The surge protection device is aged and / or defective. When a surge occurs, the surge pulse is forwarded to the surge protection device. Because the surge protection device is aged or defective, the current increases, activating the overload protection. The surge pulse is then extinguished or diverted by the overload protection. This can be detected by the detection circuit.

[0040] As explained above, in the event of an overvoltage, the overload protection can switch simultaneously with the surge protection device in order to dissipate an impulse or surge current.

[0041] Overload protection, i.e., the component capable of extinguishing short-circuit currents and / or switching overvoltages, is particularly relevant when the downstream surge protection device is disabled, for example, to extinguish a follow current. If the surge protection device is not disabled, it can still perform this function, so that the overload protection only provides a low-impedance path for the impulse current discharge.

[0042] The detection circuit ensures that an aged, but not yet defective, surge protection device is detected early, specifically during normal operation or at a normal operating voltage, i.e., when no overvoltage pulse is present. This can also occur, for example, if a leakage current flowing to ground through the surge protection device is detected by the monitoring device, particularly its detection circuit, during normal operation or at a normal operating voltage. The leakage current is not large enough to activate or trigger the overload protection. Furthermore, the leakage current is not large enough to trigger the (thermal) disconnect device.

[0043] The monitoring device can therefore have a parallel circuit comprising the overload protection and the detection circuit. In this respect, the overload protection and the detection circuit are connected in parallel to each other. However, the overload protection and the detection circuit are each connected in series with the surge protection device. The leakage current present during normal operation due to degradation of the surge protection device is routed through the detection circuit, since the overload protection is in a non-conductive state during normal operation.

[0044] Alternatively, as described above, the detection circuit can be used to detect that the overload protection of the monitoring device diverts or extinguishes the overvoltage pulse, since this is no longer possible for the overvoltage protection device due to its degradation.

[0045] The monitoring device can be implemented cost-effectively because the detection circuit is connected in parallel to the overload protection, meaning the detection circuit only needs to be designed up to the protection level of the overload protection. Furthermore, the monitoring device, and especially the detection circuit, can be designed to be compact and space-saving.

[0046] Further advantages and features of the invention will become apparent from the following description and the drawings, to which reference is made. The drawings show: - Fig. 1 a schematic representation of an assembly according to the invention in a first embodiment, - Fig. 2 a schematic representation of an assembly according to the invention in a second embodiment, - Fig. 3 a schematic representation of a thermal separation device that can be used in a monitoring device according to the invention, and - Fig. 4 a schematic overview of a flowchart of the inventive method for monitoring a surge protection device.

[0047] In Fig. Figure 1 shows an assembly 10 comprising a surge protection device 12 (SPD) and a monitoring device 14. In the illustrated embodiment, the SPD and the monitoring device 14 are shown as separate devices, each with its own independent housing. Alternatively, however, the SPD and the monitoring device 14 can also be housed in a common housing, i.e., in a single device, namely a protection device. In this respect, the SPD and the monitoring device 14 can also be referred to as a surge protection module and a monitoring module, respectively.

[0048] As from Fig. As can be clearly seen in Figure 1, the surge protection device 12 and the monitoring device 14 are connected in series, the monitoring device 14 having a connection 16 serving as an input and a connection 17 serving as an output, to which the surge protection device 12 is connected.

[0049] The monitoring device 14 has an internal conductor structure 18 which includes an overload protection 20 in a first current path 22. The overload protection 20 is in Fig. 1 is represented, for example, as a spark gap, in particular as a horn spark gap.

[0050] The conductor structure 18 also has a second current path 24, which is parallel to the first current path 22, which will be discussed below.

[0051] Furthermore, the monitoring device 14 includes a detection circuit 26, which is generally configured to detect a parameter that is indicative of degradation and / or a defect of the surge protection device 12, for example, a leakage current-related parameter. This parameter is therefore, in particular, a parameter that indicates that a leakage current is flowing through the surge protection device 12, which is associated with degradation or a defect of the surge protection device 12.

[0052] The detection circuit 26 is assigned to the overload protection 20 in order to detect and subsequently evaluate the (leakage current-relevant) parameter based on the overload protection 20, in particular its state.

[0053] Furthermore, the monitoring device 14 includes a thermal disconnect device 28, which is arranged between the terminal 18 serving as an outgoing connection and the conductor structure 18, in particular between the terminal 17 serving as an outgoing connection and the overload protection 20.

[0054] The thermal disconnect device 28 is thermally coupled to a release element 30, which is arranged in the second current path 24 of the conductor structure 18. The release element 30 can be a resistor, as shown in Fig. 1 is shown.

[0055] In addition to the triggering element 30, a switch 32 is also arranged in the second current path 24, which can be controlled by the detection circuit 26.

[0056] The detection circuit 26 detects and evaluates the (leakage current-relevant) parameter, whereby this can be done by comparing the detected (leakage current-relevant) parameter with at least one threshold value to determine whether the (leakage current-relevant) parameter has reached the threshold value.

[0057] Should this be the case, it can be concluded, among other things, that the surge protection device 12 is degraded or defective. This means that the surge protection device 12 is no longer fully functional, so that any overvoltage could no longer be safely diverted by the surge protection device 12.

[0058] For this reason, the detection circuit 26 is set up to control the switch 32 so that it closes in order to close the second current path 24.

[0059] In the event of an overvoltage, a current flows via the second current path 24 and thus through the triggering element 30, which is designed as a resistor, thereby converting electrical energy into thermal energy (heat).

[0060] Since the triggering element 30, designed as a resistor, is thermally coupled to the thermal disconnecting device 28, this results in the thermal disconnecting device 28 triggering from a certain thermal energy (heat), which depends on the electrical energy, in order to disconnect the surge protection device 12 from the mains, i.e. to perform a galvanic isolation.

[0061] In that case, both the first current path 22 and the second current path 24 would be disconnected from the surge protection device 12 via the thermal disconnect device 28.

[0062] In this context, the term "disconnecting" the surge protection device 12 refers to the situation where the surge protection device 12 is not connected to the network even if the monitoring device 14, in particular the overload protection 20, were in an electrically conductive state.

[0063] In Fig. Figure 3 shows the thermal separation device 28 schematically. This comprises a first electrical conductor 34 and a second electrical conductor 36, which are in an initial state that is in Fig. As shown in Figure 3, the components are connected both electrically and mechanically via a solder material 38. In the initial state, a current can therefore flow through the first electrical conductor 34, the solder material 38, and the second electrical conductor 36.

[0064] The first electrical conductor 34 can be assigned to the conductor structure 18, i.e., connected to it, whereas the second electrical conductor 36 is assigned to the terminal 17 serving as the outgoing, i.e., connected to it.

[0065] The thermal disconnect device 28 can also include a disconnector 40, which in the illustrated embodiment is designed as a wedge. The disconnector 40 can be pre-tensioned by a spring 42, so that a mechanical force is exerted on the two electrical conductors 34, 36 to effect mechanical separation if the solder material 38 softens due to thermal stress. The pre-tensioned spring 42 can be held in the pre-tensioned position by its mechanical attachment to the solder material 38. Alternatively, the pre-tensioned spring 42 can have a locking mechanism that is actively released, in particular by a release signal from the detection circuit 26, whereby the spring 42 pushes the disconnector 40 towards the solder joint.

[0066] With the monitoring device 14, it is therefore possible to extinguish a current limit as well as an occurring short-circuit current by means of the overload protection 20 in the form of the spark gap protecting or supporting the surge protection device 12 in regular operation.

[0067] Furthermore, the (leakage current-relevant) parameter for the overvoltage protection device 12 to be monitored is continuously recorded by the detection circuit 26, which is indicative of a degradation or a defect of the overvoltage protection device 12, making it possible to detect a degradation or a defect of the overvoltage protection device 12 particularly early.

[0068] Should this be the case, the release element 30 is activated by the detection circuit 26 actuating the switch 32 to close the second current path 24 in which the release element 30 is located. A current then flows through the second current path 24, thereby converting at least part of the electrical energy in the release element 30 into thermal energy, which causes the thermal separation device 28, in particular the solder material 38, to heat up.

[0069] At a certain point, this leads to the disconnection of the surge protection device 12 by means of the thermal disconnect device 28, whereby the surge protection device 12 is galvanically isolated.

[0070] The dielectric strength can therefore be increased.

[0071] In addition, the monitoring device 14 has a status indicator 44, which can be used to display, among other things, the status of the monitoring device 14 and / or the surge protection device 12 on the monitoring device 14 itself.

[0072] The detection circuit 26 can control a display mode of the status indicator 44 that depends on the degradation of the surge protection device 12. A color, brightness, and / or flashing frequency can be controlled.

[0073] Furthermore, the monitoring device 14 can include a communication interface 46. Information about the status of the monitoring device 14 and / or the surge protection device 12 can be transmitted via the communication interface 46 to a separately designed device, so that the status or condition can also be retrieved at a location other than the installation location of the monitoring device 14.

[0074] In Fig. Figure 2 shows an alternative embodiment of assembly 10, which differs from the first embodiment according to Fig. 1 differs in that the second current path 24 is led to a further connection 48 of the monitoring device 14.

[0075] The surge protection device 12 can be bypassed via the additional connection 48 using a bridging conductor 50, so that a current flow is ensured even if the surge protection device 12 has been galvanically isolated.

[0076] In the embodiment shown, the first current path 22, in which the overvoltage protection 20 is provided, would be disconnected via the thermal disconnect device 28.

[0077] In principle, the resistor that serves as the trigger element 30 can be a graphite pellet.

Claims

[1] Monitoring device (14) for monitoring a surge protection device (12), wherein the monitoring device (14) has a connection (17) for the surge protection device (12), wherein the monitoring device (14) has an overload protection (20), wherein the monitoring device (14) has a detection circuit (26) which is configured to detect a parameter which is indicative of a defect and / or degradation of the surge protection device (12), wherein a release element (30) is provided which can be switched on by means of the detection circuit (26), and wherein the monitoring device (14) has a thermal disconnect device (28) which is thermally coupled to the release element (30). [2] Monitoring device (14) according to claim 1, characterized by , that the detection circuit (26) is set up to evaluate the parameter in order to determine a degradation and / or a defect of the surge protection device (12). [3] Monitoring device (14) according to claim 1 or 2, characterized by , that the thermal disconnect device (28) is arranged between the overload protection (20) and the connection (17). [4] Monitoring device (14) according to any one of the preceding claims, characterized by , that the release element (30) is a resistor which is thermally coupled to the thermal disconnect device (28). [5] Monitoring device (14) according to any one of the preceding claims, characterized by , that the monitoring device (14) has a switch (32) which is controlled by the detection circuit (26) so that a current flow can occur via a current path (24) in which the triggering element (32) is located. [6] Monitoring device (14) according to claim 5, characterized by , that the current path (24) is connected in parallel to the overload protection (20). [7] Monitoring device (14) according to any one of the preceding claims, characterized by, that the thermal separation device (28) has at least two electrical conductors (34, 36) which are electrically connected to a solder material (38) in an initial state, in particular wherein the solder material (38) is a low-temperature solder material. [8] Monitoring device (14) according to any one of the preceding claims, characterized by , that the thermal separation device (28) has a separator (40), in particular a spring-loaded separator. [9] Monitoring device (14) according to any one of the preceding claims, characterized by , that the overload protection (20) comprises a spark gap, a gas discharge tube and / or a power electronic component, in particular a thyristor, a TRIAC or a DIAC. [10] Monitoring device (14) according to any one of the preceding claims, characterized by that the detection circuit (26) includes at least a status indicator (44) and / or a communication interface (46). [11] Assembly (10) comprising a surge protection device (12) and a monitoring device (14) according to one of the preceding claims, wherein the surge protection device (12) and the monitoring device (14) are connected in series. [12] Method for monitoring a surge protection device (12) using a monitoring device (14), comprising the following steps: - Detecting a parameter that is indicative of a defect and / or degradation of the surge protection device (12), - Switching on a release element (30) when the parameter has a value that is associated with degradation and / or a defect of the surge protection device (12), wherein the release element (30) is arranged in a current path (24) and is thermally coupled to a thermal disconnect device (28), and - Disconnecting the surge protection device (12) to be monitored by means of the thermal disconnect device (28). [13] Method according to claim 12, characterized by , that the parameter is compared with at least one threshold value to determine the degradation and / or defect of the surge protection device (12).

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