Method and apparatus for detecting fuse failure

Abstract

A method and apparatus for detecting fuse failure of a protective fuse (5) for protecting an associated load (7) from overcurrent and / or overload, the method comprising the steps of: measuring (S) by a current sensor element (2). A The current I flowing through the protective fuse (5) in the current path to the load (7) m ; Determine (S) B One or more failure indicators FI, each failure indicator FI being adapted to be based on a measured current I m To indicate the possible failure of the protective fuse (5); and if at least one failure indicator FI indicates the possible failure of the protective fuse (5) and if the current I measured by the current sensor element (2) m It has been stopped (I) m =0) The current flows through the protective fuse (5) or is below the predetermined current threshold (I m mth ), then automatic detection (S) C ) Protect the fuse (5) from failure.​

Description

Technical Field

[0001] The present invention relates to a method and apparatus for detecting the failure of a protective fuse used to protect an associated load from overcurrent and / or overload. Background Technology

[0002] Fuses are widely used as overcurrent protection devices with a fusible part that is heated and disconnected by the flow of overcurrent through the fuse. Different types of fuses can be used in power distribution systems. A wide variety of different types of electrical fuses exist.

[0003] Overcurrent includes any current exceeding the rated current that the load can carry under specified conditions. Even low overcurrents can overheat system components in a distribution system unless removed promptly, potentially damaging the system's insulation, conductors, and other equipment. Such overcurrents can even melt conductors and evaporate the supplied insulation. Very high currents can generate magnetic forces and can even cause busbars to bend and twist.

[0004] Generally, there are two main types of overcurrent fault conditions: overload fault conditions and short-circuit fault conditions. In a short-circuit fault condition, there is an overcurrent flowing in the circuit outside its normal current path. A short-circuit fault can be caused, for example, by insulation breakdown or a faulty electrical connection. When a short-circuit fault occurs, the current may bypass the normal load and may take a shorter path, hence the term short circuit. An overload fault condition can be defined as an overcurrent confined to the normal current path; however, this overcurrent, if allowed to persist in the circuit for an extended period, can damage equipment and / or connected wiring.

[0005] Protective fuses can be used to protect various types of loads, including inductive, capacitive, and resistive loads against overload and / or short-circuit fault conditions. For example, a protective fuse can be used to protect an electric motor connected to a motor protection switch. Motor protection switches are suitable for protecting electric motors from overload and / or external conductor failure. If motor isolation fails, motor protection may simply disconnect the motor from the power grid to prevent further damage from the grid. In this case, the motor is defective. Another typical use case is motor thermal protection, which shuts down the motor if it becomes too hot. In this case, the motor remains usable and can be restarted after a cooling period. Motor protection can be used to prevent any damage to the electric motor, such as internal faults within the motor. Three-phase motor protection switches can be connected in series with protective fuses. Therefore, in many applications, it is necessary to detect if a protective fuse has been damaged or tripped due to overcurrent. Thus, in many applications, fuse failure monitoring is required to improve the operational reliability and safety of the distribution system. For critical loads in the distribution system protected by associated protective fuses, fuse failure monitoring for the protective fuses can be implemented. Other examples include emergency power systems or battery-loaded systems. In many applications, the protective fuse is connected in series with an additional protective switch, which may include a semiconductor protective switch or an electromechanical protective switch.

[0006] Traditional methods for detecting fuse failure rely on measuring the voltage drop along the fuse, which requires measuring the potential across the fuse. To determine the potential difference at the fuse, two wires are needed and must be connected across the fuse. This increases the necessary technical effort and circuit complexity. Furthermore, in special cases, the connecting wires across the fuse may break, increasing the probability of undetected fuse failure. In such situations, the operational safety of the distribution system is compromised. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide a method and apparatus for detecting the failure of a protective fuse, which improves the reliability of failure detection without significantly increasing the complexity of the detection circuit.

[0008] According to a first aspect of the invention, the above objective is achieved by a method for detecting the failure of a protective fuse that includes the features of claim 1.

[0009] According to a first aspect, the present invention provides a method for detecting fuse failure of a protective fuse used to protect an associated load from overcurrent and / or overload, the method comprising the following steps:

[0010] Measure the current Im flowing through the protective fuse in the current path reaching the load via a current sensor element;

[0011] Determine one or more failure indicators, each failure indicator being adapted to indicate a possible failure of the protective fuse based on the measured current Im; and

[0012] Automatically detect a failure of the protective fuse if at least one of the determined failure indicators indicates a possible failure of the protective fuse and if the current Im measured by the current sensor element has stopped flowing through the protective fuse (Im = 0) or is below a predetermined current threshold (Im < Imth).

[0013] According to another aspect, the present invention provides a method for detecting a failure of a protective fuse for protecting an associated load against overcurrent and / or overload,

[0014] wherein the method comprises the following steps:

[0015] Measure the current flowing through the protective fuse to the load via a current sensor element;

[0016] Determine the thermal energy generated in the protective fuse based on the measured current; and

[0017] Automatically detect a failure of the protective fuse if the determined thermal energy exceeds a predetermined threshold and if the current measured by the current sensor element has stopped flowing through the protective fuse.

[0018] Thus, in a preferred embodiment, a failure indicator where the determined thermal energy exceeds a predetermined threshold can be evaluated as detecting that the protective fuse has failed. In an alternative embodiment, other failure indicators or combinations of failure indicators can be used to detect a failure of the protective fuse.

[0019] An advantage of the method according to the present invention is that it works reliably even in harsh environments. Another advantage of the method according to the present invention is that a failure of the protective fuse can be detected very quickly within a short detection time of less than 1 millisecond.

[0020] In a possible embodiment of the method according to the present invention, the first failure indicator includes a calculated ampere - square - second (I 2 t) value that indicates that the thermal energy generated in the protective fuse exceeds a predetermined threshold. 2 t) value that indicates that the thermal energy generated in the protective fuse exceeds a predetermined threshold.

[0021] In a possible embodiment of the method according to the present invention, the second failure indicator includes the magnitude of the measured current Im exceeding the predetermined rated current IR of the protective fuse.

[0022] In a possible embodiment of the method according to the invention, the third failure indicator comprises that the current increment or current slope (dI / dt) of the measured current Im exceeds a predetermined current increment (dI / dt max).

[0023] In a possible embodiment of the method according to the invention, each failure indicator comprises a failure indicator flag which is set or reset within the predetermined evaluation period in response to the current Im measured by the current sensor element within the predetermined evaluation period.

[0024] In a possible embodiment of the method according to the invention, the logical value of the failure indicator flag of the failure indicator set or reset during the evaluation period is stored in a register for the next evaluation period.

[0025] In a possible embodiment of the method according to the invention, the logical value of the failure indicator flag of the failure indicator is processed to calculate a confidence level which indicates the total likelihood that the protection fuse has failed.

[0026] In a possible embodiment of the method according to the invention, if the calculated confidence level exceeds a predetermined confidence level threshold and if the current Im measured by the current sensor element has stopped flowing through the protection fuse or is below a predetermined current threshold (Im < Imth), the failure of the protection fuse is determined.

[0027] In a possible embodiment of the method according to the invention, the confidence level indicating the total likelihood that the protection fuse has failed is calculated based on the logical value of the failure indicator flag and / or based on at least one external status signal.

[0028] In a possible embodiment of the method according to the invention, the external status signal comprises a switch status signal (SWSS) which indicates that the associated load has not been externally switched off by the protection switch.

[0029] In a possible embodiment of the method according to the invention, the failure indicator comprises a multi-level failure indicator.

[0030] In a possible embodiment of the method according to the invention, the first failure indicator and the second failure indicator are scaled according to the number k of parallel current paths connected to a plurality of loads.

[0031] In a possible embodiment of the method according to the invention, based on the measured current Im flowing through the parallel current path to the load, an average current Imavg is calculated, and the average current Imavg is used as the predetermined current threshold (Imth).

[0032] In a possible embodiment of the method according to the invention, if the determined thermal energy indicated by the calculated ampere squared seconds (I2t) value does not exceed a predetermined threshold, but the magnitude of the measured current Im is higher than a predetermined rated current IR, the energy input into the protection fuse by the flowing current is determined.

[0033] In a possible embodiment of the method according to the invention, if the energy determined to be input into the protection fuse by the current exceeds a predetermined threshold, an overload failure warning signal (OFWS) is automatically generated, which indicates an impending failure of the protection fuse due to an overload current.

[0034] In a possible embodiment of the method according to the invention, the energy input into the protection fuse is determined by calculating the heat transfer balance for the protection fuse, which is the difference between the heat generated by the current flowing through the protection fuse and the heat dissipated by the protection fuse.

[0035] According to another aspect, the present invention provides a fuse failure detection device configured to detect the failure of a protection fuse that protects an associated load against overcurrent and / or overload.

[0036] The fuse failure detection device includes:

[0037] A current sensor element adapted to measure the current Im flowing through the protection fuse in the current path to the load;

[0038] A determination unit adapted to determine one or more failure indicators FI, which are adapted to indicate a possible failure of the protection fuse based on the current Im measured by the current sensor element; and

[0039] A failure detection unit adapted to: automatically detect the failure of the protection fuse if at least one determined failure indicator FI indicates a possible failure of the protection fuse and if the current Im measured by the current sensor element has stopped (Im = 0) flowing through the protection fuse or is below a predetermined current threshold (Im < Imth).

[0040] In a possible embodiment of the fuse failure detection device according to the invention, the at least one failure indicator includes:

[0041] A first failure indicator FI1, which includes a calculated ampere squared seconds (I2t) value indicating that the thermal energy generated in the protection fuse exceeds a predetermined threshold.

[0042] A second failure indicator FI2, which includes that the measured current Im exceeds a predetermined rated current IR of a protection fuse; and

[0043] A third failure indicator FI3, which includes that the current increment (dI / dt) of the measured current Im exceeds a predetermined current increment (dI / dtmax).

[0044] In a possible embodiment of the fuse failure detection device according to the present invention, each failure indicator FI includes a failure indicator flag FIF, which is set or reset within the predetermined evaluation period in response to the current Im measured by the current sensor element within the predetermined evaluation period.

[0045] In a possible embodiment of the fuse failure detection device according to the present invention, the failure indicator flag FIF of the failure indicator FI set or reset in the evaluation period EC is stored in the corresponding register for the next evaluation period.

[0046] In a possible embodiment of the fuse failure detection device according to the present invention, it further includes a calculation unit, which is adapted to process the failure indicator flag FIF of the stored failure indicator to calculate a confidence level, which indicates the total likelihood that the protection fuse has failed.

[0047] In a possible embodiment of the fuse failure detection device according to the present invention, if the calculated confidence level exceeds a predetermined confidence level threshold and if the current Im measured by the current sensor element has stopped flowing through the protection fuse or is lower than a predetermined current threshold (Im < Imth), the failure of the protection fuse is determined.

[0048] In a possible embodiment of the fuse failure detection device according to the present invention, the calculation unit calculates the confidence level indicating the total likelihood that the protection fuse (5) has failed according to the logical value of the failure indicator flag FIF and according to at least one external state signal.

[0049] In a possible embodiment of the fuse failure detection device according to the present invention, the external state signal includes a switch state signal (SWSS), which indicates that the associated load has not been externally switched off by the protection switch.

[0050] In a possible embodiment of the fuse failure detection device according to the present invention, the failure indicator includes a multi-level failure indicator.

[0051] In a possible embodiment of the fuse failure detection device according to the present invention, the first failure indicator FI1 and the second failure indicator FI2 are scaled according to the number k of parallel current paths connected to multiple loads.

[0052] In a possible embodiment of the fuse failure detection device according to the invention, the calculation unit is adapted to calculate the average current Imavg based on the measured current Im flowing to one or more loads through the parallel current path, wherein the calculated average current Imavg is used as a predetermined current threshold (Imth).

[0053] In a possible embodiment of the fuse failure detection device according to the invention, the failure detection unit is adapted to: if at least one failure indicator indicates that the protective fuse may fail and if the current Im measured by the current sensor element stops flowing through the protective fuse (I m =0), or if the current Im measured by the current sensor element is lower than the predetermined current threshold (I m mth If the circuit fails, a fuse failure detection signal (FFDS) will be automatically generated, which indicates the possible failure of the protective fuse due to short-circuit current.

[0054] In a possible embodiment of the fuse failure detection device according to the invention, the determining unit is adapted to calculate an ampere-seconds (I²t) value representing the heat energy generated at the protective fuse in response to a current Im measured by a current sensor element, and wherein the failure detection unit is adapted to compare the calculated ampere-seconds (I²t) value with a predetermined ampere-seconds (I²t) value to generate a fuse failure detection signal (FFDS) if the determined heat energy has exceeded a predetermined threshold and the current Im measured by the current sensor element has stopped flowing through the protective fuse and if a received switch status signal (SWSS) indicates that at least one associated load has not been externally turned off by the protective switch.

[0055] In a possible embodiment of the fuse failure detection device according to the invention, the determining unit is further adapted to: if the determined thermal energy does not exceed a predetermined threshold, but the amplitude of the measured current Im is higher than the predetermined rated current (IR), then determine the energy input to the protective fuse caused by the flowing current Im.

[0056] In a possible embodiment of the fuse failure detection device according to the invention, the failure detection unit is further adapted to generate an overload failure warning signal (OFWS) when the energy input to the protective fuse by the determined current I exceeds a predetermined threshold, wherein the generated overload failure warning signal (OFWS) indicates an impending failure of the protective fuse due to overload current.​

[0057] In a possible embodiment of the fuse failure detection device according to the invention, the determining unit is adapted to determine the energy input to the protective fuse by calculating the heat transfer balance of the protective fuse as the difference between the heat generated by the current I flowing through the protective fuse and the heat dissipated by the protective fuse.

[0058] In a possible embodiment of the fuse failure detection device according to the present invention, the current sensor component is adapted to measure DC current and / or to measure AC current flowing through the corresponding current path.

[0059] In a possible embodiment of the fuse failure detection device according to the present invention, the current sensor element is connected in series with the protective fuse in the current supply path or branch of the load, or is attached to the current supply path or branch of the load.

[0060] In a possible embodiment of the fuse failure detection device according to the invention, the failure detection unit includes an interface for receiving external status signals, particularly from a protective switch connected in series with the protective fuse along the current supply path of the load.

[0061] In a possible embodiment of the fuse failure detection device according to the invention, a user interface is included, which is adapted to output a failure warning signal, an instantaneous state of a failure indicator and an instantaneous state of a status signal, and to output a confidence level calculated by a calculation unit based on a logic value of the failure indicator flag of the failure indicator and based on at least one external status signal, the confidence level indicating the total likelihood that the protective fuse has failed.

[0062] According to another aspect, the present invention provides an adapter device comprising a fuse failure detection device according to one aspect of the present invention.

[0063] In a possible embodiment of the method according to the first aspect of the invention, a fuse failure detection signal is automatically generated if the determined thermal energy has exceeded a predetermined threshold and if the current measured by the current sensor element has stopped flowing through the protective fuse. The generated fuse failure detection signal indicates a possible failure of the protective fuse due to a short-circuit current. In particular, if the method employs several I... 2 The multi-level comparison method for limit lines involves comparing I... 2 The t-value can be used to determine fuse failure and can also cover overload events.

[0064] This has the following advantages: the fuse failure detection signal can be provided to a local or remote controller and can be considered for use in controlling the functions of a distribution system that includes protected loads.

[0065] In another possible embodiment of the method according to the first aspect of the invention, the thermal energy is calculated as an ampere-square-second value and compared with a predetermined threshold.

[0066] This has the following advantages: the ampere square second value used as the threshold can be obtained from the data sheet of the protection fuse.

[0067] In another possible embodiment of the method according to the first aspect of the invention, as an additional condition, a failure of the protective fuse is detected if the received switch status signal indicates that the associated load has not been externally turned off by the protective switch.

[0068] This has the following advantages: when the protective switch connected in series with the protective fuse has tripped via an external control signal, causing the current to stop flowing through the protective fuse, it will not result in a fuse failure detection signal that could be incorrectly interpreted as a failure of the protective fuse.

[0069] In another possible embodiment of the method according to the first aspect of the invention, if the determined thermal energy does not exceed a predetermined threshold, but the measured current amplitude is higher than a predetermined rated current, the energy input to the protective fuse caused by the flowing current is determined.

[0070] In another possible embodiment of the method according to the first aspect of the invention, if the determined energy input to the protective fuse by the current does indeed exceed a predetermined threshold, an overload failure warning signal is automatically generated, indicating an impending failure of the protective fuse due to overload current.

[0071] This provides the significant advantage of detecting impending fuse failure before it actually occurs. This allows for, for example, proactive maintenance of distribution systems that include the fuses. For instance, if a fuse has already been damaged due to overload current, its potential failure can be predicted, and corresponding countermeasures can be initiated before it completely fails.

[0072] In another possible embodiment of the method according to the first aspect of the invention, the energy input to the protective fuse is determined by calculating the heat transfer balance of the protective fuse as the difference between the heat generated by the current flowing through the protective fuse and the heat dissipated by the protective fuse.

[0073] According to another aspect, the present invention provides a fuse failure detection device including the features of claim 8.

[0074] According to a second aspect, the present invention provides a fuse failure detection device configured to detect the failure of a protective fuse used to protect an associated load from overcurrent and / or overload, wherein the fuse failure detection device comprises:

[0075] A current sensor element adapted to measure the current flowing through a protective fuse to the load;

[0076] A determining unit, adapted to determine the heat energy generated at the protective fuse based on the current measured by the current sensor element; and

[0077] A failure detection unit is adapted to automatically detect a failure of the protective fuse when the determined thermal energy exceeds a predetermined threshold and when the current measured by the current sensor element has stopped flowing through the protective fuse.

[0078] In a possible embodiment of the fuse failure detection device according to a second aspect of the invention, the failure detection unit is adapted to automatically generate a fuse failure detection signal indicating a possible failure of the protective fuse due to a short-circuit current when the determined thermal energy has exceeded a predetermined threshold and when the current measured by the current sensor element has stopped flowing through the protective fuse.

[0079] In another possible embodiment of the fuse failure detection device according to a second aspect of the invention, the determining unit is adapted to calculate an ampere-square-second value representing the heat energy generated at the protective fuse in response to the current measured by the current sensor element.

[0080] In another possible embodiment of the fuse failure detection device according to the second aspect of the invention, the failure detection unit is adapted to generate a fuse failure detection signal by comparing a calculated ampere-square-second value with a predetermined ampere-square-second value when the determined thermal energy has exceeded a predetermined threshold and the current measured by the current sensor element has stopped flowing through the protective fuse, and when the received switch status signal indicates that the associated load has not been externally turned off by the protective switch.

[0081] In another possible embodiment of the fuse failure detection device according to a second aspect of the invention, the determining unit is further adapted to: determine the energy input to the protective fuse caused by the flowing current when the determined thermal energy does not exceed a predetermined threshold, but the amplitude of the measured current is higher than a predetermined rated current.

[0082] In another possible embodiment of the fuse failure detection device according to a second aspect of the invention, the failure detection unit is adapted to generate an overload failure warning signal when the energy input from the current to the protective fuse exceeds a predetermined threshold, wherein the generated overload failure warning signal indicates an impending failure of the protective fuse due to overload current.

[0083] In another possible embodiment of the fuse failure detection device according to a second aspect of the invention, the determining unit is adapted to determine the energy input to the protective fuse by calculating the heat transfer balance of the protective fuse as the difference between the heat generated by the current flowing through the protective fuse and the heat dissipated by the protective fuse.

[0084] In a possible embodiment of the fuse failure detection device according to a second aspect of the invention, the current sensor component is adapted to measure DC current.

[0085] In yet another possible alternative embodiment of the fuse failure detection device according to the second aspect of the invention, the current sensor component is adapted to measure AC current.

[0086] In another possible embodiment of the fuse failure detection device according to the second aspect of the invention, the current sensor element is connected in series with the protective fuse within the current supply path of the load, or attached to the current supply path of the load.

[0087] In one possible implementation, the current sensor element attached to the current supply path of the load can also move along the wires or busbars of the current supply path.

[0088] In another possible embodiment of the fuse failure detection device according to a second aspect of the invention, the failure detection unit includes an interface for receiving a switch status signal from a protective switch connected in series with the protective fuse along the current supply path of the load.

[0089] According to another aspect, the present invention provides an adapter device comprising a fuse failure detection device according to a second aspect of the present invention. Attached Figure Description

[0090] In the following description, different aspects of possible embodiments of the invention are described in more detail with reference to the accompanying drawings.

[0091] Figure 1 A block diagram illustrating a possible exemplary embodiment of a fuse failure detection device according to one aspect of the present invention is shown;

[0092] Figure 2A flowchart illustrating the main steps of a possible exemplary embodiment of a method for detecting the failure of a protective fuse according to another aspect of the present invention is shown.

[0093] Figure 3 Another flowchart illustrating a possible exemplary embodiment of a method for detecting the failure of a protective fuse according to one aspect of the present invention is shown;

[0094] Figure 4A , Figure 4B The diagram shows the signal diagram of the protective fuse operation under short-circuit conditions;

[0095] Figure 5 A simplified diagram is shown to illustrate the definition of the ampere-square-second value, which is used to determine the thermal energy within a protective fuse by means of the method and apparatus according to the invention.

[0096] Figure 6 A diagram is shown illustrating the operating behavior of a protective fuse used to provide protection against overload and / or overcurrent.

[0097] Figure 7 A flowchart illustrating the main steps of another possible exemplary embodiment of the method for detecting the failure of a protective fuse according to the present invention is shown;

[0098] Figure 8 A possible implementation of a trip indicator subsystem used in a method for detecting the failure of a protective fuse according to the present invention is shown;

[0099] Figure 9 Another possible implementation of a trip indicator subsystem with multi-level I2t diagnostics used in the method for detecting failure of a protective fuse according to the present invention is shown;

[0100] Figure 10 A possible implementation of the external signal subsystem used in the method for detecting the failure of a protective fuse according to the present invention is shown;

[0101] Figure 11 A flowchart illustrating the steps of another possible exemplary embodiment of the method for detecting the failure of a protective fuse according to the present invention is shown;

[0102] Figure 12 A possible implementation of a trip indicator subsystem for multi-branch assessment used in a method for detecting failure of a protective fuse according to the present invention is shown. Detailed Implementation

[0103] from Figure 1As can be seen from the schematic block diagram, the fuse failure detection device 1 according to the present invention may include three main components. In the illustrated embodiment, the fuse failure detection device 1 includes a current sensor element 2, a determination unit 3, and a failure detection unit 4. Figure 1 As shown, the fuse failure detection device 1 is connected in series with the protective fuse 5. In a possible implementation, such as... Figure 1 As shown, the fuse failure detection device 1 can be connected in series in the current supply path between the power supply 6 and the electrical load 7. In a possible implementation, it can also be... Figure 1 As shown in the block diagram, the current supply path may also include an optional protective switch 8. The electrical load 7 may be a resistive load, a capacitive load, or an inductive load.

[0104] In a possible implementation, the current sensor element 2 can be connected in series with the protective fuse 5 within the current supply path of the load 7. The current supply path can be adapted to carry either DC or AC supply current. In another possible implementation, the current sensor element 2 can also be attached to the current supply path of the load 7. In this implementation, the current sensor element 2 can be, for example, clipped onto a wire that carries the current flowing through the protective fuse 5 and the protective switch 8 to the load 7. The current generates a magnetic field, which can be detected by the current sensor element 2 attached to the current-carrying conductor or the current-carrying busbar. This implementation has the additional advantage that the current sensor element 2 can be moved along the current supply path between the power source 6 and the load 7. Therefore, the current sensor element 2 attached to the current supply path can also be manually fixed to the current-carrying conductor between the power source 6 and the load 7 at different locations. This provides greater flexibility when expanding an existing power distribution system by adding the fuse failure detection device 1 according to the invention to the corresponding system. In other words, this implementation does not require interruption of the existing current-carrying conductor between the protective fuse 5 and the electrical load 7.

[0105] exist Figure 1 In the illustrated embodiment, the fuse failure detection device 1 is disposed behind the protective fuse 5, that is, on the output side of the protective fuse 5 facing the load. In an alternative embodiment, the fuse failure detection device 1 according to the invention may also be located on the side of the protective fuse 5 facing the power supply 6.

[0106] In possible implementations Figure 1 The current sensor element 2 shown can be adapted to measure the DC current supplied by the power source 6 and supplied to the electrical load 7 via the current supply path. In an alternative embodiment, the current sensor element 2 is adapted to measure the AC current flowing from the AC current source 6 to the electrical load 7 via the current supply path.

[0107] In a possible implementation, the current sensor element 2 may include a shunt resistor connected in series with the protective fuse 5 within the current supply path of the load 7. The voltage along the shunt resistor is proportional to the current flowing through it.

[0108] In an alternative embodiment, the current sensor element 2 may include a coil, particularly a Rogowski coil, which is suitable for measuring alternating current or high-speed current pulses. Due to its low inductance, the Rogowski coil can respond to rapidly changing currents in a few nanoseconds.

[0109] The current sensor element 2 may also include other types of current sensor elements, particularly Hall effect current sensors or giant magnetoresistive (GMR) sensors. Hall effect sensors are suitable for measuring the magnitude of a magnetic field that can be caused by a current flowing along the current supply path. Therefore, in a possible implementation, the attachment of the current sensor element 2 to the current supply path does not require a current connection. In such an implementation, the fuse failure detection device 1 is currently isolated from the current supply path between the power supply 6 and the load 7. This improves the operational reliability of the fuse failure detection device 1 in the event of a high short-circuit overcurrent. Furthermore, since the current sensor element 2 is simply mechanically attached to the current supply path to measure the magnetic field when the fuse failure detection device 1 is installed on the current transmission line between the protective fuse 5 and the load 7, without interrupting the current supply path, it facilitates the expansion of existing power distribution systems.

[0110] from Figure 1 As can be seen from the block diagram, the fuse failure detection device 1 does not need to know the potentials on both sides of the protective fuse 5. According to the present invention, the fuse failure detection device 1 is located on the upstream side of the protective fuse 5 facing the power source 6 or on the downstream side of the protective fuse 5 facing the electrical load 7.

[0111] Current sensor element 2 measures the current I flowing through protective fuse 5 and notifies the measured current I of the circuit breaker. Figure 1 The fuse failure detection device 1 shown includes a determination unit 3. The determination unit 3 is adapted to determine the heat energy generated at the protective fuse 5 based on the current I measured by the current sensor element 2. In a possible embodiment, the determination unit 3 is adapted to calculate an ampere-second value representing the heat energy generated at the protective fuse 5 in response to the current I measured by the current sensor element 2.

[0112] The fuse failure detection device 1 further includes a failure detection unit 4, which is adapted to automatically detect the failure of the protective fuse 5 when the determined thermal energy does exceed a predetermined threshold and when the current measured by the current sensor element 2 has stopped flowing through the protective fuse 5.

[0113] In a possible implementation, the failure detection unit 4 is adapted to automatically generate a fuse failure detection signal FFDS when the determined thermal energy has exceeded a predetermined threshold and when the current I measured by the current sensor element 2 has stopped flowing through the protective fuse 5. The fuse failure detection signal FFDS indicates a possible failure of the protective fuse 5 due to a short-circuit current. In another possible implementation, the failure detection unit 4 is adapted to compare a calculated ampere-seconds value with a predetermined ampere-seconds value to generate the fuse failure detection signal FFDS when the determined thermal energy has exceeded the predetermined threshold and when the current I measured by the current sensor element 2 has stopped flowing through the protective fuse 5.

[0114] The I²t rating relates to the amount of energy a fuse element is allowed to pass when it clears an electrical fault. This terminology is commonly used for short-circuit conditions, and these values ​​are used for coordination within electrical networks. I²t parameters can be provided in charts in manufacturer datasheets for different fuse types. To coordinate fuse operation with upstream or downstream devices, melting I²t and clearing I²t are specified. Melting I²t is proportional to the amount of energy required to begin melting the fuse element. Clearing I²t is proportional to the total energy the fuse is allowed to pass when clearing a fault. This energy depends primarily on the current and time applied to the fuse, as well as the present fault level and system voltage. Because a fuse's I²t rating is proportional to the energy it allows to pass, it is a measure of thermal damage caused by the heat and magnetic forces generated by the fault.

[0115] In a possible implementation, the failure detection unit 4 generates a fuse failure detection signal FFDS only when the additional condition is met, i.e., when the received switch status signal SWSS indicates that the associated load 7 has not been externally turned off by the associated protective switch 8 located within the current supply path. In this implementation, the failure detection unit 4 may include an interface to receive the switch status signal SWSS from the protective switch 8, which is connected in series with the protective fuse 5 along the current supply path of the load 7. The protective switch 8 may include an electromechanical protective switch and / or a semiconductor protective switch.

[0116] In a possible implementation, the failure detection unit 4 is further adapted to generate an overload failure warning signal OFWS when the determined energy input to the protective fuse 5 by the current flowing along the current supply path does indeed exceed a predetermined threshold. The generated overload failure warning signal OFWS can indicate an impending (i.e., future) failure of the protective fuse 5 due to overload current. In a possible implementation, the determining unit 3 can determine the energy input to the protective fuse 5 by calculating the heat transfer balance for the protective fuse 5, which is the difference between the heat generated by the current I flowing through the protective fuse 5 and the heat dissipated by the protective fuse 5. Therefore, if the determined thermal energy does not exceed the predetermined threshold, but the measured current I is higher than the predetermined rated current, the energy input to the protective fuse 5 caused by the flowing current I can be determined. If the input energy does exceed the predetermined threshold, the failure detection unit 4 can generate an overload failure warning signal OFWS, and the overload failure warning signal OFWS can be output via the interface of the fuse failure detection device 1. Figure 1 In the illustrated embodiment, the fuse failure detection device 1 includes a data interface provided for outputting a generated fuse failure detection signal FFDS and an overload failure warning signal OFWS. The fuse failure detection signal FFDS indicates failure of the protective fuse 5 due to a short-circuit current. In this case, the protective fuse 5 has already tripped or melted due to a very high short-circuit overcurrent. Conversely, the overload failure warning signal OFWS indicates possible future failure of the protective fuse 5 due to an overload current flowing along the current supply path.

[0117] Both the Fuse Failure Detection Signal (FFDS) and the Overload Warning Signal (OFWS) can be provided to the local or remote controller to automatically trigger countermeasures. Upon receiving the FFDS signal, the local or remote controller must replace the protective fuse 5, which has already tripped due to a short-circuit current. Upon receiving the OFWS signal, the protective fuse 5 may still be operational, but it may be damaged by the flowing overload current, requiring replacement by a maintenance operator in the near future. The OFWS signal provides a warning about the potential future functional failure of the protective fuse 5 and, in possible implementations, can automatically trigger preemptive maintenance operations on the distribution system.

[0118] In the illustrated embodiment, the fuse failure detection device 1 may include a control interface to receive a switch status signal SWSS from a protective switch 8, which may be connected in series with the protective fuse 5 within the current supply path. The protective switch 8 may be a separate component, particularly a semiconductor device such as an insulated-gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or other semiconductor switching devices, such as a bipolar junction transistor (BJT) or a junction-gate field-effect transistor (JFET). Other possible implementations include thyristors or integrated gate-commutated thyristors (IGCTs). Once the protective switch 8 has turned off the electrical load 7, the switch status signal SWSS can be set to logic high, indicating that the associated load 7 has been turned off by the protective switch 8. As long as the switch status signal SWSS is logic low and indicates that the associated load has not been externally turned off by the protective switch 8, if the determined thermal energy has exceeded a predetermined threshold and the failure detection unit 4 detects that the current measured by the current sensor element 2 has stopped flowing through the protective fuse 5, the failure detection unit 4 may automatically generate a fuse failure detection signal FFDS. In this embodiment, the failure detection unit 4 may monitor the amplitude of the current measured by the current sensor element 2. If the current amplitude drops to zero, the failure detection unit 4 can determine that the current I has stopped flowing through the protective fuse 5. Therefore, in the preferred embodiment, the failure detection unit 4 generates the fuse failure detection signal FFDS only when three conditions are met. The first condition is that the calculated ampere-second square value has exceeded the predetermined ampere-second square value. The second condition is that the current I flowing through the protective fuse 5 and measured by the current sensor element 2 has stopped flowing. The third condition is that the received switch status signal SWSS indeed indicates that the protective switch 8 has not been turned off; for example, the received switch status signal SWSS is logic low.

[0119] In a possible implementation of the fuse failure detection device 1, the current sensor element 2, the determination unit 3, and the failure detection unit 4 can be integrated into a corresponding device housing. In an alternative embodiment, the different units of the fuse failure detection device 1, particularly the determination unit 3 and the failure detection unit 4, can be distributed at different locations within the power distribution system. In yet another possible embodiment, the housing of the fuse failure detection device 1 may further include… Figure 1 The block diagram shows the protective switch 8.

[0120] Figure 2 This illustrates the use of protective fuses (such as...) for testing Figure 1 The block diagram illustrates a flowchart of a possible exemplary implementation of a method for preventing the failure of a fuse (5). In the illustrated implementation, the method includes three main steps S. A S B S C。

[0121] According to one aspect, the present invention provides a method for detecting a fuse failure of a protection fuse 5, the protection fuse 5 being for protecting at least one associated load 7 against overcurrent and / or overload, the method comprising the following steps:

[0122] In step S A the current Im flowing through the protection fuse 5 in the current path to the load 7 is measured by a current sensor element 2;

[0123] In step S B one or more failure indicators FI are determined, each failure indicator FI being adapted to indicate a possible failure of the protection fuse 5 based on the measured current Im; and if at least one of the determined failure indicators FI indicates a possible failure of the protection fuse 5 and if the current Im measured by the current sensor element 2 has stopped (Im = 0) flowing through the protection fuse 5 or is below a predetermined current threshold (Im < Imth), the failure of the protection fuse 5 is automatically detected in step S C .

[0124] The advantage of the method according to the invention is that it works reliably even in adverse environments. The possibility of current isolation provides a great advantage here. Thus, the voltage level and overvoltage events can be safely kept away from the user and the logic device. In addition, the evaluation circuit can be kept away from extreme environmental conditions.

[0125] Another advantage of the method according to the invention is that the failure of the protection fuse 5 can be detected very quickly within a short detection time of less than 1 millisecond.

[0126] In a possible embodiment of the method according to the invention, the first failure indicator FI1 comprises a calculated ampere square second (I2t) value which indicates that the thermal energy generated in the protection fuse 5 exceeds a predetermined threshold.

[0127] In a possible embodiment of the method according to the invention, the second failure indicator FI2 comprises the measured current Im exceeding the predetermined rated current IR of the protection fuse 5.

[0128] In a possible embodiment of the method according to the invention, the third failure indicator FI3 comprises the current increment or current slope (dI / dt) of the measured current Im exceeding a predetermined current increment (dI / dt max).

[0129] In a possible embodiment of the method according to the invention, each failure indicator FI includes a failure indicator flag FIF which, in response to a current Im measured by the current sensor element 2 within a predetermined evaluation period EC, is set or reset within this predetermined evaluation period EC. In a possible embodiment of the method according to the invention, the logical value of the failure indicator flag FIF of the failure indicator FI set or reset in the evaluation period EC is stored in a register for the next evaluation period.

[0130] In a possible embodiment of the method according to the invention, the logical value of the failure indicator flag FIF of the failure indicator FI is processed by a calculation unit of the fuse failure detection device 1 to calculate a confidence level CONF-LEV which indicates the overall likelihood that the protection fuse 5 has failed. In a possible embodiment of the method according to the invention, if the calculated confidence level CONF-LEV exceeds a predetermined confidence level threshold and if the current Im measured by the current sensor element 2 has stopped flowing through the protection fuse 5 or is below a predetermined current threshold (Im < Imth), the determination unit 3 of the fuse failure detection device 1 determines the failure of the protection fuse 5.

[0131] In a possible embodiment of the method according to the invention, a confidence level CONF-LEV indicating the overall likelihood of failure of the protection fuse 5 is calculated based on the logical value of the failure indicator flag FIF and / or based on at least one external status signal. In addition, the amplitude of the input voltage is a possible external signal that can be monitored.

[0132] In a possible embodiment of the method according to the invention, the external status signal includes a switch status signal (SWSS) which indicates that the associated load 7 has not been externally switched off by the protection switch 8.

[0133] In a possible embodiment of the method according to the invention, the failure indicator FI includes a multi-level failure indicator.

[0134] In a possible embodiment of the method according to the invention, the first failure indicator FI1 and the second failure indicator FI2 are scaled according to the number k of parallel current paths connected to the plurality of loads 7. The idea is to monitor k fuse branches, i.e. current supply paths, by means of a single monitoring unit 1 according to the invention.

[0135] In a possible embodiment of the method according to the invention, the calculation unit calculates an average current Imavg based on the measured current Im flowing through the parallel current paths to the load 7, and this average current Imavg is used as the predetermined current threshold (Imth).

[0136] In a possible embodiment of the method according to the invention, if the determined thermal energy indicated by the calculated ampere-square-second (I2t) value does not exceed a predetermined threshold, but the magnitude of the measured current Im is higher than a predetermined rated current IR, the energy input into the protection fuse 5 caused by the flowing current is determined.

[0137] In a possible embodiment of the method according to the invention, if the determined energy input into the protection fuse 5 by the current exceeds a predetermined threshold, an overload failure warning signal (OFWS) is automatically generated, which indicates an impending failure of the protection fuse 5 due to an overload current.

[0138] In a possible embodiment of the method according to the invention, the energy input into the protection fuse 5 is determined by calculating the heat transfer balance for the protection fuse 5, which is the difference between the heat generated by the current flowing through the protection fuse 5 and the heat dissipated by the protection fuse 5.

[0139] According to another aspect, the present invention provides a fuse failure detection device 1 as shown in the block diagram of Figure 1 , which is arranged to detect the failure of a protection fuse 5 for protecting an associated load 7 against overcurrent and / or overload. The fuse failure detection device 1 includes a current sensor element 2, which is adapted to measure the current Im flowing through the protection fuse 5 in the current path to the load 7. The fuse failure detection device 1 further includes a determination unit 3, which is adapted to determine one or more failure indicators FI, and the failure indicators FI are adapted to indicate a possible failure of the protection fuse 5 based on the current Im measured by the current sensor element 2. The fuse failure detection device 1 further includes a failure detection unit 4, which is adapted to: automatically detect the failure of the protection fuse 5 when at least one determined failure indicator FI indicates a possible failure of the protection fuse 5 and when the current Im measured by the current sensor element 2 has stopped (Im = 0) flowing through the protection fuse 5 or is lower than a predetermined current threshold (Im < Imth).

[0140] In Figure 1In a possible embodiment of the fuse failure detection device 1 according to the present invention as shown, at least one failure indicator FI includes a first failure indicator FI1, a second failure indicator FI2, and a third failure indicator FI3. The first failure indicator FI1 includes a calculated ampere-square-second (I2t) value, which indicates that the thermal energy generated in the protection fuse 5 exceeds a predetermined threshold. The second failure indicator FI2 includes a measured current Im exceeding a predetermined rated current IR of the protection fuse 5. The third failure indicator FI3 includes a current increment (dI / dt) of the measured current Im exceeding a predetermined current increment (dI / dt max).

[0141] In a possible embodiment of the fuse failure detection device 1 according to the present invention, each failure indicator FI includes a failure indicator flag FIF, which is set or reset within the predetermined evaluation period EC in response to the current Im measured by the current sensor element 2 within the predetermined evaluation period EC. The minimum evaluation period includes two samples from the ADC system. The maximum evaluation period may include multiple mains periods. For example, in a possible embodiment, the evaluation is performed every 10 ms (half a mains period on a 50 Hz system). Additionally, in a possible embodiment, the evaluation period can be made adaptive. The higher the stress level, the shorter the evaluation period EC can be adjusted to be.

[0142] In a possible embodiment of the fuse failure detection device 1 according to the present invention, the failure indicator flag FIF of the failure indicator FI set or reset in the evaluation period EC is stored in the corresponding register for the next evaluation period.

[0143] In a possible embodiment of the fuse failure detection device 1 according to the present invention, a calculation unit is further included, which is adapted to process the failure indicator flag FIF of the stored failure indicator FI to calculate a confidence level CONF-LEV, which indicates the total likelihood that the protection fuse 5 has failed.

[0144] In a possible embodiment of the fuse failure detection device 1 according to the present invention, if the calculated confidence level CONF-LEV exceeds a predetermined confidence level threshold and if the current Im measured by the current sensor element 2 has stopped flowing through the protection fuse 5 or is lower than a predetermined current threshold (Im < Imth), the failure of the protection fuse 5 is determined.

[0145] In a possible embodiment of the fuse failure detection device 1 according to the invention, a confidence level CONF-LEV indicating the total likelihood that the protection fuse 5 has failed is calculated by a calculation unit based on the logical value of a failure indicator flag FIF and based on at least one external status signal.

[0146] In a possible embodiment of the fuse failure detection device 1 according to the invention, the external status signal includes a switch status signal (SWSS) which indicates that the associated load 7 has not been externally switched off by a protection switch 8.

[0147] In a possible embodiment of the fuse failure detection device 1 according to the invention, the failure indicator FI includes a multi-stage failure indicator.

[0148] In a possible embodiment of the fuse failure detection device 1 according to the invention, the first failure indicator FI1 and the second failure indicator FI2 are scaled according to the number k of parallel current paths connected to a plurality of loads 7.

[0149] In a possible embodiment of the fuse failure detection device 1 according to the invention, the calculation unit is adapted to calculate an average current Tmavg based on the measured current Im flowing through the parallel current paths to the load 7, wherein the calculated average current Tmavg is used as a predetermined current threshold (Imth).

[0150] In a possible embodiment of the fuse failure detection device 1 according to the invention, the failure detection unit 4 is adapted to: automatically generate a fuse failure detection signal (FFDS) when the at least one failure indicator FI indicates a possible failure of the protection fuse 5 and when the current Im measured by the current sensor element 2 stops flowing through the protection fuse 5 (Im = 0), or when the current Im measured by the current sensor element 2 is below a predetermined current threshold (Im < Imth), the fuse failure detection signal (FFDS) indicating a possible failure of the protection fuse 5 due to a short-circuit current.

[0151] In a possible embodiment of the fuse failure detection device 1 according to the invention, the determination unit 3 is adapted to calculate an ampere-square-second (I2t) value representing the thermal energy generated at the protection fuse 5 in response to the current Im measured by the current sensor element 2, and wherein the failure detection unit 4 is adapted to: compare the calculated ampere-square-second (I2t) value with a predetermined ampere-square-second (I2t) value to generate a fuse failure detection signal (FFDS) when the determined thermal energy has exceeded a predetermined threshold and when the current Im measured by the current sensor element 2 has stopped flowing through the protection fuse 5 and when the received switch status signal (SWSS) indicates that the associated load 7 has not been externally switched off by the protection switch 8.

[0152] In a possible embodiment of the fuse failure detection device 1 according to the present invention, the determining unit 3 is further adapted to: determine the energy input to the protective fuse 5 caused by the flowing current Im when the determined thermal energy does not exceed a predetermined threshold, but the amplitude of the measured current Im is higher than the predetermined rated current (IR).

[0153] In a possible embodiment of the fuse failure detection device 1 according to the invention, the failure detection unit 4 is adapted to generate an overload failure warning signal (OFWS) when the energy input to the protective fuse 5 by the determined current I exceeds a predetermined threshold, wherein the generated overload failure warning signal (OFWS) indicates an impending failure of the protective fuse 5 due to overload current.

[0154] In a possible embodiment of the fuse failure detection device 1 according to the present invention, the determining unit 3 is adapted to determine the energy input to the protective fuse 5 by calculating the heat transfer balance for the protective fuse 5, which is the difference between the heat generated by the current I flowing through the protective fuse 5 and the heat dissipated by the protective fuse 5.

[0155] In a possible embodiment of the fuse failure detection device 1 according to the present invention, the current sensor component 2 is adapted to measure DC current and / or to measure AC current flowing through the corresponding current path.

[0156] In a possible embodiment of the fuse failure detection device 1 according to the present invention, the current sensor element 2 is connected in series with the protective fuse 5 in the current supply path of the load 7, or is attached to the current supply path of the load 7.

[0157] In a possible embodiment of the fuse failure detection device 1 according to the invention, the failure detection unit 4 includes an interface for receiving external status signals, particularly from a protective switch 8 connected in series with the protective fuse 5 along the current supply path of the load 7. Figure 1 As shown.

[0158] In a possible embodiment of the fuse failure detection device 1 according to the present invention, a user interface is included, which is adapted to output a failure warning signal, the instantaneous state of the failure indicator FI and the instantaneous state of the status signal, and output a confidence level CONF-LEV calculated by a calculation unit based on the logic value of the failure indicator flag FIF of the failure indicator FI and based on at least one external status signal, the confidence level CONF-LEV indicating the total likelihood that the protective fuse 5 has failed.

[0159] According to another aspect, the present invention provides an adapter device comprising, as shown in the figure Figure 1 The block diagram shows a fuse failure detection device 1 according to one aspect of the present invention.

[0160] According to another aspect, the present invention provides a method for detecting the failure of a protective fuse used to protect an associated load 7 from overcurrent and / or overload, wherein the method includes the following steps:

[0161] In step S A In the process, the current flowing through the protective fuse 5 to the load 7 is measured by the current sensor element 2;

[0162] In step S B In step S, the heat energy generated in the protective fuse 5 is determined based on the measured current, and if the determined heat energy exceeds a predetermined threshold and if the current measured by the current sensor element 2 has stopped flowing through the protective fuse 5, the process proceeds as follows: C The automatic detection system detects the failure of the protective fuse 5.

[0163] Therefore, the failure indicator FI used can be the determined thermal energy exceeding a predetermined threshold.

[0164] In the first step S A In this process, the current flowing through the protective fuse 5 to the load 7 is detected by the current sensor element 2. The current sensor element 2 can be used as follows: Figure 1 The block diagram shown is integrated into the housing of the fuse failure detection device 1. The current sensor element 2 may also include a separate element connected to the determination unit 3 and a failure detection unit 4 connected to the sensor signal line. The measured current I may include DC current and / or AC current.

[0165] In another step S B In this process, the heat energy generated in the protective fuse 5 is determined based on the measured current. In a possible implementation, the heat energy can be calculated as an ampere-second value and then compared with a predetermined threshold.

[0166] In another step S C In step S B The determined thermal energy received in step S is a predetermined threshold and serves as a second condition, if... A If the current I measured by current sensor element 2 has stopped flowing through protective fuse 5, a failure of protective fuse 5 is automatically detected. If such a failure is detected, a fuse failure detection signal FFDS can be generated, which indicates the possible failure of protective fuse 5 due to short-circuit current.

[0167] Figure 3A flowchart illustrating a possible implementation of a method for protecting against the failure of fuse 5 is shown.

[0168] The process begins with step S0. In another step S1, it is determined whether current flow is detectable. If the amplitude of the flowing current I measured by the current sensor component 2 exceeds a predetermined threshold during a predetermined minimum time period, current flow is detected. If current flow has been detected in step S1, the measured ampere-second value of the current I can be calculated in step S2 and compared with a predetermined ampere-second threshold. This predetermined ampere-second threshold includes parameters that can be set during initialization in the configuration memory of the determining unit 3. In a possible implementation, the ampere-second threshold stored in the configuration memory can also be adjusted by a user or operator through a user interface, or by an external controller through the data interface of the fuse failure detection device 1. Other parameters that can be set in the configuration register or configuration memory may include the rated current visible to the load 7 or the rated current of the type of fuse used. In a possible implementation, the comparison of the calculated ampere-second value with the predetermined ampere-second threshold can be performed by a comparator in the failure detection unit 4. This can be a hardware comparator or a logical representation within the program code of the μController. In a possible implementation, the ampere-second value can be calculated based on the measured current every ten milliseconds in a possible implementation. This duration can vary depending on the usage. In a possible implementation, the duration used to calculate the ampere-second value is adjustable. If the ampere-second value does not exceed a predetermined threshold, then in step S3 as follows... Figure 3 Further comparisons are made as shown in the flowchart. In step S3, it is determined whether the measured current actually exceeds a predetermined rated current that can be read from the configuration memory of the fuse failure detection device 1. If this is not the case, the protective fuse 5 is still within its normal operating range and no critical condition has occurred. Conversely, if the measured current exceeds the predetermined rated current, the energy input to the protective fuse 5 caused by the flowing current I can be calculated or determined in step S4. In a possible implementation, the determining unit 3 determines the energy input to the protective fuse 5 in step S4 by calculating the heat transfer balance for the protective fuse 5. The heat transfer balance includes the difference between the heat generated by the current I flowing through the protective fuse 5 and the heat dissipated by the protective fuse 5. If the energy input to the protective fuse 5 by the current I does exceed a predetermined threshold, in a preferred embodiment, the failure detection unit 4 can generate an overload failure warning signal OFWS in step S4, which indicates a possible impending failure of the protective fuse 5 due to an overload current.

[0169] Therefore, if the thermal energy represented by the calculated ampere-second squared value does not exceed a predetermined threshold, but the current flowing through the protective fuse 5 is higher than the predetermined rated current (i.e., in the case of overload current), an overload failure warning signal OFWS is generated. In a preferred embodiment, if the critical energy input to the protective fuse 5, as indicated by the calculated heat transfer balance, may damage the protective fuse 5, the overload failure warning signal OFWS is automatically generated.

[0170] In step S5, it is determined whether the current I flowing through the protective fuse 5 and measured by the current sensor element 2 has stopped. If the current I is still flowing, the process cycles back to step S2, as follows. Figure 3 The flowchart is shown. Conversely, if the monitored current I has stopped flowing, then in step S6 it is determined whether it is due to an external protection switch (such as...). Figure 1 The protective switch 8) shown in the block diagram causes an interruption of current I. In a possible implementation, the received switch status signal SWSS is evaluated to determine whether an external shutdown has been performed. If the received switch status signal SWSS indicates an external shutdown, the process loops back to step S1, as... Figure 3 The flowchart is shown. However, if the switch status signal SWSS indicates that no external shutdown has been performed, it is concluded in step S7 that the protective fuse 5 has been tripped due to high short-circuit current. In this case, the failure detection unit 4 can also automatically generate a fuse failure detection signal FFDS in step S7, which indicates the possible failure of the protective fuse 5 due to short-circuit current.

[0171] from Figure 3 It can be seen that there are two parameters that can be set externally, namely the predetermined ampere-second threshold I. 2 t max and rated current I R In one possible implementation, the two parameters can be set during the initialization phase. In another embodiment, these parameters can also be adjusted via a user or data interface during operation of the fuse failure detection device 1. The data interface can connect the fuse failure detection device 1 to a remote or local controller that can set parameters during operation of the power distribution system. Furthermore, the rated current I can be adjusted according to the load 7 to be protected by the protective fuse 5. R In one possible implementation, the allowable rated current I can be read from a database or from local memory integrated into the load 7 to be protected. R .

[0172] The protective fuse 5 includes fusible elements. These fusible elements within the protective fuse 5 can melt to protect downstream loads connected to the protective fuse 5. The protective fuse can also be referred to as a sacrificial device in a circuit. The fusible elements within the protective fuse 5 are specifically designed to continuously carry a specific amount of current without breaking. This is referred to as the rated current I of the protective fuse 5. R If current I flows through the bridge of these components or the restriction of the fuse 5, heat is generated. The fuse elements continue to carry current as intended until an equilibrium is reached in heat transfer. This equilibrium is achieved when the generated heat equals the dissipated heat.

[0173] Conversely, if an imbalance in heat transfer occurs due to an overcurrent condition (such as overload or short circuit), the amount of heat generated exceeds the amount of heat dissipated. This, in turn, causes a temperature rise at the fusible element of the protective fuse 5, which is implemented through a limiting section or weakness. If the temperature rise does reach the melting point of the fusible element (e.g., 1085°C for copper or 962°C for silver), the element bridge within the protective fuse 5 does begin to melt and break, causing the current I flowing through the protective fuse 5 to the protected load 7 to be interrupted. In the case of a short circuit, the fusible element within the protective fuse 5 begins to melt and then disconnects the protected load 7 from the power supply 6 within milliseconds. During this time period, an electric arc can be generated within the fuse 5, as well as... Figure 4A , Figure 4B The signal diagram is shown below.

[0174] The heat generated during the interruption of the fault current through the protective fuse 5 can be expressed in Joules, commonly referred to as ampere-square second. The heat energy is proportional to the square of the current I during the operating time t.

[0175] The generated heat energy can be expressed as the ampere-square-second value of melting, the ampere-square-second value of the electric arc, and the ampere-square-second value of clearing.

[0176] The value of molten ampere square seconds I 2 t is the heat energy transferred by the protective fuse 5 after the overcurrent occurs until the fuse element melts.

[0177] The ampere-square-second value of the electric arc is the heat energy transferred by the protective fuse 5 during the arc time of the protective fuse 5.

[0178] The ampere-square-second value for clearing is the sum of the ampere-square-second value for melting and the ampere-square-second value for arcing.

[0179] Figure 5The calculation of the ampere-second square value is shown. There are melting time and arcing time. Melting time includes the time span from the onset of the overcurrent condition to the moment arcing begins within the protective fuse 5. This is followed by arcing time, i.e., the time span between the melting of the fuse link and the interruption of the overcurrent. If the point of no return has been reached, the protective fuse 5 melts and interrupts the current supply path.

[0180] Figure 6 The operation of the protective fuse 5 for short-circuit overcurrent protection and overload current protection is shown.

[0181] Overcurrent is any current exceeding the rated current that a connected load, device, or component can carry under specified conditions. Even moderate overcurrents can rapidly overheat system components unless they are removed in time.

[0182] Overload fault conditions include overcurrents confined to the normal current path. Typically, this is less than the protected load or the applied rated current I. R A 600% overcurrent is called an overload fault current. Overload conditions often occur in applications or systems when temporary surge currents are present continuously in the system, such as due to mechanical blockages or equipment malfunctions.

[0183] Typically, it is greater than the rated current I of the protected device or load. R The 600% overcurrent is called the short-circuit fault current. Short-circuit conditions can occur due to events such as accidents, improper application, or insulation breakdown.

[0184] Figure 6 A graph showing the characteristic curves of protective fuse 5 is displayed. Protective fuse 5 has three main operating regions. As long as the measured current I is lower than the rated current I... R This ensures normal operating behavior and protects fuse 5 from damage. If the current I exceeds the predetermined rated current I... R In a possible implementation, lead supplied at the copper limiting section or bridge may diffuse into the bridge elements, thereby lowering the melting temperature of the fused bridge element. The reduced melting temperature might be, for example, 170°C. Therefore, overload currents causing material to diffuse into the connecting bridge elements could lead to a decrease in melting temperature over time, eventually causing the bridge elements to break. In the case of a short circuit, very high currents cause the bridging copper elements to break almost immediately, as the initial melting temperature of copper eventually reaches approximately 1083°C.

[0185] The determination unit 3 of the fuse failure detection device 1 can continuously determine the heat energy generated in the protective fuse 5 based on the current measured by the current sensor element 2. No detection or warning signal is generated as long as the protective fuse 5 is within its normal operating range. Overload conditions can be detected by continuously monitoring the calculated heat transfer balance.

[0186] The heat transfer balance indicates the difference between the heat input and the heat dissipated by the protective fuse 5.

[0187] Heat input can be calculated as ΔQ + =R*I 2 *Δt.

[0188] The dissipated heat can be calculated as ΔQ - =λ(T) n -T0)*Δt.

[0189] Here, Δt is the unit of time increment.

[0190] T0 is, for example, an ambient temperature of 35°C.

[0191] T n It is to infer the temperature.

[0192] R is the resistance at the fuse element; and

[0193] I represents electric current.

[0194] T n+1 =T n +ΔT

[0195] Where ΔT is the temperature difference, it can be calculated as follows:

[0196] ΔT=(ΔQ + -ΔQ - )*C*Δt

[0197] Where C is the heat capacity.

[0198] For the lead and restricted fuse elements protecting fuse 5, the heat input can be calculated separately. This calculation can be performed by a computing unit (i.e., a processor or microprocessor).

[0199] In possible implementations Figure 1 The fuse failure detection device 1 shown may also include at least one temperature sensor element suitable for measuring the instantaneous temperature T at the protective fuse 5. The measured temperature can be used to verify the calculated inferred temperature or for calibration purposes.

[0200] In a possible implementation, the fuse failure detection device 1 can be integrated into other devices. In a possible implementation, the fuse failure detection device 1 can be integrated into an adapter device. This adapter device can be used to connect an electrical load or electrical load control device to a power supply system's wires or busbars. In a possible implementation, the adapter device may also include a protective switch 8 and a protective fuse 5.

[0201] In another possible embodiment, the fuse failure protection device 1 may further include a user interface with a graphical display unit. In this embodiment, the fuse failure detection signal FFDS and / or the overload failure warning signal OFWS can be displayed to the operator of the power system to assist the operator in taking necessary countermeasures when either the FFDS or OFWS signal is displayed. The display unit of the user interface may also display parameters set for the fuse failure detection device 1, particularly the rated current I. R And a predetermined ampere-square-second threshold. In a possible implementation, in Figure 2 , Figure 3 The method according to the invention shown in the exemplary flowchart can be executed by a processor or FPGA integrated in the fuse failure detection device 1. The fuse failure detection device 1 can be a mobile handheld device 1 with an integrated current sensor element 2, which can be clipped onto the wire or bus of the power path of the load 7.

[0202] Figure 7 A flowchart illustrating the main steps of an exemplary embodiment of a method for detecting the failure of a protective fuse 5 according to one aspect of the present invention is shown. It illustrates the process with confidence level assessment. Figure 3 The flowchart shown is a generalized variation. For example... Figure 7 As shown, the process begins with step S0. In the first step S1, the current Im flowing through the protective fuse 5 in the current path to at least one load 7 is obtained by the current sensor element 2. Figure 7 In another step S2 of the flowchart shown, it is checked whether any fault indicator flag FIF has been set to true in the previous evaluation cycle EC. If so, and Figure 7If, in step S3 of the flowchart, the measured current Im is found to have a zero amplitude, then in a possible implementation, an external state signal predicting that the measured current Im is zero can be evaluated in step S5. If no Failure Indicator Flag (FIF) set to true exists in the previous evaluation cycle EC, then the tripping condition can be evaluated in step S4 based on the measured current Im used for that evaluation cycle EC, and the obtained FIF can be stored for the next evaluation cycle EC. If the measured current Im is not found to be zero at step S3, the FIF flag is also re-evaluated. This is important so that as long as the current Im continues to flow, it is always updated for the next EC cycle.

[0203] As in Figure 7 As shown in the flowchart, in step S6a, the Failure Indicator Flag (FIF) can be processed to calculate the confidence level CONF-LEV, which indicates the total likelihood that the protective fuse 5 has failed. The calculated confidence level can indicate to the user which conditions have been met, regardless of whether the actual fuse has tripped. The confidence level indicating the total likelihood that the protective fuse 5 has failed can be based on the logic value (H / L) of the Failure Indicator Flag (FIF) and on at least one external status signal (also... Figure 7 (as shown in the figure) to calculate. In a possible implementation, the external status signal may include a switch status signal SWSS, which indicates that the associated load 7 has not been externally turned off by the protection switch 8.

[0204] The confidence level CONF-LEV can also reflect the history of a specific indicator across various (potentially adjustable) evaluation periods EC. This provides information about the electrical stress the system exhibits over time.

[0205] Providing a parallel structure within the trip indication subsystem allows for differentiation between different confidence levels. In this way, the indication of a tripped fuse becomes more reliable. The more Failure Indication Flags (FIFs) that are set, the greater the likelihood that the protective fuse 5 has tripped or broken.

[0206] The choice of quantization time (i.e., the length of the evaluation period EC) can depend on the implementation of the analog-to-digital converter system. Typically, the protective fuse 5 operates in the range of a few milliseconds. Choosing an ADC clock that is 10 to 100 times faster than the system time constant is a viable approach. This still results in relatively low requirements for the ADC site, thus allowing for easy implementation of the ADC system. The proposed evaluation can be based on actual sampling points or on pre-calculated RMS values.

[0207] Figure 8 It shows in Figure 7The flowchart shown illustrates possible implementations of the trip indicator subsystem in step S4. For example... Figure 8 As shown, several failure indicators can be used. For each failure indicator FI, an associated failure indicator flag FIF can be provided. Figure 8 In the illustrated embodiment, the first failure indicator includes a calculated ampere-seconds (I²t) value that indicates or represents the thermal energy generated in the protective fuse 5 exceeding a predetermined threshold. If the calculated I²t value is higher than the predetermined threshold, then... Figure 8 Set the corresponding I²t flag FIF1 as shown. If the calculated ampere-second squared I²t value is lower than a predetermined threshold, then... Figure 8 Reset the corresponding I2t flag FIF1 as shown.

[0208] The second failure indicator FI2 may include a measured current Im whose amplitude exceeds the predetermined rated current IR of the protective fuse 5. If the measured current Im exceeds the predetermined rated current IR, then... Figure 8 Set the corresponding IR flag FIF2 as shown. Conversely, if the measured current Im does not exceed the predetermined rated current IR of the protective fuse 5, then... Figure 8 Reset the IR flag FIF2 as shown.

[0209] The third failure indicator FI3 may include the measured current increment or current slope dI / dt of the current Im exceeding a predetermined current increment. If the current slope of the measured current Im exceeds the maximum predetermined current increment dI / dtmax, then... Figure 8 Set the corresponding dI / dt failure indicator flag FIF3 as shown. Conversely, if the current slope of the measured current does not exceed the predetermined current increment, then... Figure 8 Reset the corresponding dI / dt failure indicator flag FIF3 as shown.

[0210] Figure 9 Another variation of the trip indicator subsystem with multi-level I2t diagnostics is shown.

[0211] The illustrated subsystem considers that a typical protective fuse 5 can have a non-constant I²t value that depends on the time and magnitude of the current Im applied to the protective fuse 5. The lower the magnitude of the measured current Im, the higher the I²t value used to trip the protective fuse 5. If the magnitude of the current Im drops below the rated current IR, the I²t value may reach infinity, and the protective fuse 5 will never trip. Therefore, more accurate predictions can be achieved if multiple values ​​I²t(I1, t1); I²t(I2, t2); I²t(In, tn) are provided to the trip indicator subsystem. These multiple values ​​can typically be selected from the datasheet of the protective fuse 5 manufacturer. Interpolation can be applied between the available data points, as long as these data points are not too far apart from each other. The I²t evaluation block can now adjust its comparison value I²t(In, tn) based on the actual current Im or the average current calculated over the last n evaluation samples. In addition to classic melting fuses, the characteristics of electromechanical / bimetallic circuit breakers can also be used... Figure 9 The techniques shown in the flowchart are used to cover this.

[0212] Figure 10 It shows in Figure 7 Another variation of the external signal subsystem applied in step S5 of the flowchart shown. In this embodiment, further improvements can be made by monitoring the input voltage Uin on the gate side of the protective fuse 5. This value is generally quite readily available because the measuring device for evaluating the fuse current can be connected to the bus of the power distribution system supplying power to multiple fuse branch circuits. Therefore, a potential shutdown of the power grid should not be misinterpreted, as this could also result in zero-load current. By also monitoring the input voltage Uin on the power grid side of the protective fuse 5, misinterpretations of fuse failure can be avoided. If the input voltage Uin on the power grid side of the protective fuse 5 is lower than a predetermined minimum voltage Umin, then as Figure 10 Set the corresponding flag to represent the input voltage Uin as shown. Alternatively, other external status signals can be used, such as... Figure 10 The power switch status is shown. If the power switch is on, it can be used as follows: Figure 10 Set the corresponding power switch label as shown.

[0213] Furthermore, the confidence level of the total likelihood that the protective fuse 5 has failed can be calculated based on the logic value of the failure indicator flag, and can also be based on... Figure 10 The calculation is performed using the external status signals shown in the flowchart. These external status signals include the status signal representing the input voltage Uin on the power grid side of the protective fuse 5, the load switch status, and the power supply switch status. Furthermore, any knowledge of the external switch status can be used to avoid any kind of misinterpretation of the logic value of the failure indicator flag FIF.

[0214] Figure 11 Another flowchart is shown to illustrate an improved general system for multi-branch monitoring.

[0215] After obtaining the measured current amplitude in step S1a, the average current can be calculated in step S1b and stored in association with the determined load switch state, such as... Figure 11 As shown.

[0216] If, in step S3, the measured current amplitude is found to be less than the calculated average current value, and in step S5, the external status signal predicts that the measured current is less than the average current, then in step S6b, it is determined that the protective fuse 5 has tripped. Figure 11 As shown.

[0217] If load 7 is relatively constant or used as a basis for slow dynamics, then Figure 11 The multi-branch evaluation method shown provides the best results. Furthermore, multi-branch evaluation is particularly effective if the fuse ratings for each branch are equal. Moreover, multi-branch evaluation is more accurate when fewer electrical branches are provided. If the load is switched by a switching unit, the switching state of the corresponding switching unit should be applied to the evaluation unit. The calculated ampere-second (I²t) value and the measured amplitude of the current Im both represent the sum / integral value of the entire system. However, the high current slope value dI / dt is independent of the number of branches. Therefore, the failure indicator FI is the best indicator for multi-branch evaluation. Additionally, the individual branches of the protection fuse 5 that actually tripped may still be unknown. However, the branches can be detected by opening all load switches and checking the corresponding current Im.

[0218] Figure 12 It shows the use of in Figure 7 Another possible implementation of the improved trip indicator subsystem for multi-branch evaluation in step S4 of the flowchart shown. In the implementation shown, the first failure indicator FI1 (i.e., the calculated ampere-second I²t value) and the second failure indicator FI2 (i.e., the amplitude of the measured current Im) can be scaled according to the number k of parallel current paths or branches connected to multiple loads 7. In the case of multi-branch evaluation, several parallel current paths, i.e., branches, can be monitored. Therefore, the I²t evaluation and Im / IR comparison are scaled by the number k of parallel branches. Conversely, the current slope (i.e., the dI / dt value) is independent of the number of parallel branches. This can be used to detect trip events. The idea of ​​adding multi-level I²t monitoring is also applicable to... Figure 12 The implementation method is shown in the flowchart.

Claims

1. A method for detecting fuse failure of a protective fuse (5) for protecting an associated load (7) from overcurrent and / or overload, The method includes the following steps: The current I flowing through the protective fuse (5) in the current path to the load (7) is measured by the current sensor element (2). m ; Define one or more failure indicators FI, each failure indicator FI being adapted to be based on a measured current I. m To indicate the possible failure of the protective fuse (5); as well as If at least one failure indicator FI indicates a possible failure of the protective fuse (5) and if the current I measured by the current sensor element (2) m The current has stopped flowing through the protective fuse (5) or is below the predetermined current threshold I. mth The system will automatically detect the failure of the protective fuse (5).

2. The method according to claim 1, wherein, The first failure indicator FI1 includes a calculated ampere-second value, which indicates that the heat generated in the protective fuse (5) exceeds a predetermined threshold.

3. The method according to claim 2, wherein, The second failure indicator FI2 includes the measured current I. m Exceeding the predetermined rated current I of the protective fuse (5) R .

4. The method according to claim 1, wherein, The third failure indicator FI3 includes the measured current I. m The current increment or current slope dI / dt exceeds the predetermined current increment dI / dt max .

5. The method according to claim 1, wherein, Each failure indicator FI includes a failure indicator flag FIF, in response to the current I measured by the current sensor element (2) within a predetermined evaluation period EC. m The failure indicator flag FIF is set or reset within the predetermined evaluation period EC.

6. The method according to claim 5, wherein, The logical value of the failure indicator flag FIF of the failure indicator FI, which is set or reset in the evaluation cycle EC, is stored in a register for the next evaluation cycle.

7. The method according to claim 6, wherein, The instantaneous and historical logical values ​​of the failure indicator flag FIF of the failure indicator FI are processed to calculate a confidence level that indicates the total likelihood that the protective fuse (5) has failed.

8. The method according to claim 7, wherein, If the calculated confidence level exceeds a predetermined confidence level threshold and if the current I measured by the current sensor element (2) m The current has stopped flowing through the protective fuse (5) or is below the predetermined current threshold I. mth If so, the failure of the protective fuse (5) is determined.

9. The method according to claim 7 or 8, wherein, The confidence level indicating that the protective fuse (5) has failed is calculated based on the logic value of the failure indicator flag and / or based on at least one external status signal, including the input voltage, load switch status and / or power supply switch status on the input side of the protective fuse (5).

10. The method according to claim 9, wherein, The external status signal includes a switch status signal (SWSS), which indicates that the associated load (7) has not been externally turned off by the protection switch (8).

11. The method according to claim 1, wherein, The failure indicator FI includes a multi-level failure indicator.

12. The method according to claim 3, wherein, The first failure indicator FI1 and the second failure indicator FI2 are scaled according to the number k of parallel current paths connected to multiple loads (7).

13. The method according to claim 1, wherein, Based on the measured current I flowing to the load (7) through the parallel current path m Calculate the average current I mavg The average current I mavg Used as the predetermined current threshold I mth .

14. The method according to claim 2, wherein, If the determined thermal energy indicated by the calculated ampere-second value does not exceed the predetermined threshold, but the measured current I m The amplitude is higher than the predetermined rated current I. R The energy input to the protective fuse (5) caused by the flowing current is determined.

15. The method according to claim 14, wherein, If the energy input to the protective fuse (5) by the current exceeds a predetermined threshold, an overload failure warning signal (OFWS) is automatically generated, which indicates an impending failure of the protective fuse (5) due to overload current.

16. The method according to claim 15, wherein, The energy input to the protective fuse (5) is determined by calculating the heat transfer balance for the protective fuse (5), wherein the heat transfer balance is the difference between the heat generated by the current flowing through the protective fuse (5) and the heat dissipated by the protective fuse (5).

17. A fuse failure detection device (1) configured to detect the failure of a protective fuse (5) for protecting an associated load (7) from overcurrent and / or overload. The fuse failure detection device (1) includes: A current sensor element (2) adapted to measure the current I flowing through the protective fuse (5) in the current path to the load (7). m ; Determining unit (3), adapted to determine one or more failure indicators FI, said one or more failure indicators FI adapted to determine based on the current I measured by said current sensor element (2). m To indicate the possible failure of the protective fuse (5); as well as Failure detection unit (4), adapted to: if at least one determined failure indicator FI indicates a possible failure of the protective fuse (5) and if the current I measured by the current sensor element (2) m The current has stopped flowing through the protective fuse (5) or is below the predetermined current threshold I. mth The system will automatically detect the failure of the protective fuse (5).

18. The fuse failure detection device according to claim 17, wherein, The at least one failure indicator FI includes: A first failure indicator FI1 includes a calculated ampere-second value, which indicates that the heat generated in the protective fuse (5) exceeds a predetermined threshold. The second failure indicator FI2 includes the measured current I. m Exceeding the predetermined rated current I of the protective fuse (5) R ,as well as The third failure indicator FI3 includes the measured current I. m The current increment dI / dt exceeds the predetermined current increment dI / dt max .

19. The fuse failure detection device according to claim 17 or 18, wherein, Each failure indicator FI includes a failure indicator flag FIF, in response to the current I measured by the current sensor element (2) within a predetermined evaluation period EC. m The failure indicator flag FIF is set or reset within the predetermined evaluation period EC.

20. The fuse failure detection device according to claim 19, wherein, The failure indicator flag FIF of the failure indicator FI, which is set or reset in the evaluation cycle EC, is stored in the corresponding register for the next evaluation cycle.

21. The fuse failure detection device according to claim 17, further comprising a calculation unit adapted to process a stored failure indicator flag FIF of the failure indicator FI to calculate a confidence level indicating the total likelihood that the protective fuse (5) has failed.

22. The fuse failure detection device according to claim 21, wherein, If the calculated confidence level exceeds a predetermined confidence level threshold and if the current I measured by the current sensor element (2) m The current has stopped flowing through the protective fuse (5) or is below the predetermined current threshold I. mth If so, the failure of the protective fuse (5) is determined.

23. The fuse failure detection device according to claim 21, wherein, The calculation unit calculates the confidence level of the total likelihood that the protective fuse (5) has failed, based on the logic value of the failure indicator flag FIF and at least one external status signal.

24. The fuse failure detection device according to claim 23, wherein, The external status signal includes a switch status signal (SWSS), which indicates that the associated load (7) has not been externally turned off by the protection switch (8).

25. The fuse failure detection device according to claim 17, wherein, The failure indicator FI includes a multi-level failure indicator.

26. The fuse failure detection device according to claim 18, wherein, The first failure indicator FI1 and the second failure indicator FI2 are scaled according to the number k of parallel current paths connected to multiple loads (7).

27. The fuse failure detection device according to claim 21, wherein, The calculation unit is adapted to calculate based on the measured current I flowing to the load (7) through the parallel current path. m To calculate the average current I mavg The average current I calculated mavg Used as the predetermined current threshold I mth .

28. The fuse failure detection device according to claim 17, wherein, The failure detection unit (4) is adapted to: if the at least one failure indicator FI indicates a possible failure of the protective fuse (5) and if the current I measured by the current sensor element (2) m Stop the flow through the protective fuse (5), or if the current I measured by the current sensor element (2) m Below the predetermined current threshold (I) mth If the circuit fails, a fuse failure detection signal (FFDS) is automatically generated, which indicates the possible failure of the protective fuse (5) due to short circuit current.

29. The fuse failure detection device according to claim 17, wherein, The determining unit (3) is adapted to respond to the current I measured by the current sensor element (2). m To calculate the ampere-square-second value representing the heat energy generated at the protective fuse (5), and wherein the failure detection unit (4) is adapted to: if the determined heat energy has exceeded a predetermined threshold and the current I measured by the current sensor element (2) m The flow through the protective fuse (5) has stopped, and if the received switch status signal (SWSS) indicates that the associated load (7) has not been externally turned off by the protective switch (8), the calculated ampere-second value is compared with the predetermined ampere-second value to generate a fuse failure detection signal (FFDS).

30. The fuse failure detection device according to claim 29, wherein, The determining unit (3) is further adapted to: if the determined thermal energy does not exceed the predetermined threshold, but the measured current I m The amplitude is higher than the predetermined rated current I. R Then the current I flowing is determined. m The energy input to the protective fuse (5) caused by this.

31. The fuse failure detection device according to claim 30, wherein, The failure detection unit (4) is adapted to: if the determined current I measured by the measured current is... m If the energy input to the protective fuse (5) exceeds a predetermined threshold, an overload failure warning signal (OFWS) is generated, which indicates an impending failure of the protective fuse (5) due to overload current.

32. The fuse failure detection device according to claim 17, wherein, The determining unit (3) is adapted to determine the energy input to the protective fuse (5) by calculating the heat transfer balance for the protective fuse (5), wherein the heat transfer balance is the difference between the heat generated by the current flowing through the protective fuse (5) and the heat dissipated by the protective fuse (5).

33. The fuse failure detection device according to claim 17, wherein, The current sensor element (2) is adapted to measure DC current and / or to measure AC current flowing through the corresponding current path.

34. The fuse failure detection device according to claim 17, wherein, The current sensor element (2) is connected in series with the protective fuse (5) in the current supply path of the load (7), or is attached to the current supply path of the load (7).

35. The fuse failure detection device according to claim 17, wherein, The failure detection unit (4) includes an interface for receiving an external status signal from a protection switch (8), which is connected in series with the protection fuse (5) along the current supply path of the load (7).

36. The fuse failure detection device according to claim 17, comprising a user interface adapted to output a failure warning signal, an instantaneous state of the failure indicator FI and an instantaneous state of a status signal, and outputting a confidence level calculated by a calculation unit based on the logic value of the failure indicator flag FIF of the failure indicator FI and based on at least one external status signal, the confidence level indicating the total likelihood that the protective fuse (5) has failed.

37. An adapter device comprising a fuse failure detection device (1) according to any one of claims 17 to 36.

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