WO2025201626A1

WO2025201626A1 - Method for determining a fault condition of an electrical part of an electrical system

Info

Publication number: WO2025201626A1
Application number: PCT/EP2024/057992
Authority: WO
Inventors: Giacomo GAREGNANI; Frank Jürgen Kassubek; Kai Hencken
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2024-03-25
Filing date: 2024-03-25
Publication date: 2025-10-02
Anticipated expiration: 2026-09-25

Abstract

The disclosure relates to a method (100) for determining a fault condition of an electrical part (11) of an electrical system (10), the method (100) comprising: – obtaining measurement data indicative of a measured temperature profile of a temperature over time at one or more positions within the electrical system (10) and a measured electrical current profile of an electrical current through the electrical part (11) over time; – obtaining characteristic data of the electrical part (11), the characteristic data comprising fault-free characteristic data indicative of a time dependency of the temperature of the electrical part (11) from the electrical current through the electrical part (11) under a fault-free operation of the electrical part (11); and – determining the fault condition based on the measurement data and the characteristic data.

Description

METHOD FOR DETERMINING A FAULT CONDITION OF AN ELECTRICAL PART OF AN ELECTRICAL SYSTEM

TECHNICAL FIELD

The present invention generally relates to the field of determining fault conditions in electrical systems, such as switchgear systems, busbar systems, electrical filter systems and similar. Specifically, the present invention relates to a method for determining a fault condition of an electrical part of an electrical system, a computer program product, a data processing system, and an electrical system.

BACKGROUND OF THE INVENTION

Thermal problems are common in electrical systems, such as electrical current distribution systems or devices, but not only. Overheating occurs typically due to changes in thermal resistances, e.g., in busbar connections or in contacts in switching devices of electrical systems. Detecting such thermal issues associated with a possible fault is difficult due to the variable current flowing in and therefore variable heating power in such systems. In addition, the thermal response is often quite slow.

Simple approaches that exploit fixed temperature thresholds are of limited or no benefit. The variability of the electric current or load limits the applicability of these simple approaches based on fixed temperature thresholds. Indeed, an electrical system, in particular an electrical part thereof, may present a fault but never surpass such fixed threshold because of low loads being applied during its operation. However, when a higher load is applied and an excessive overtemperature is reached, it might be too late to maintain or replace the faulty electrical part.

Summarizing, models based on thresholds may allow to detect a failure but do not allow to identify faults or fault conditions and to track degradation or aging of an electrical part within an electrical system, in particular not based on an increased contact resistance of the electrical part due to its operation over its lifetime.

Simple dynamic models based on thermal networks may be in principle suitable for the task of modeling the temperature response of an electrical part and could be employed to track their degradation or health status and identify faults. However, an issue with thermal networks, which makes their practical usefulness doubtful, is that their parameters are difficult to identify from data, especially if only one or a limited number of temperature sensors are available. In addition, thermal networks are often parameterized using data from healthy systems or parts, which makes a change in a parameter symptomatic of a fault (e.g., the increase of an electrical contact resistance) and difficult to capture. High fidelity models, i.e. , detailed models, e.g. based on a fully resolved simulation, e.g. using finite element or other numerical methods, on the other hand, also typically need to be adapted to the real system (including its tolerances etc.) leading to similar identification problems as in the thermal network case. Furthermore, they require a large computational effort that is not feasible for computation on a field device.

Fully data-driven models, such as neural networks, can be employed to identify anomalies, and therefore faults, in the data transmitted by a temperature sensor. While these models could be effective in flagging an issue with the system or part, it is difficult to associate an anomaly to the variation of a specific physical parameters if the model is not based on physical principles itself.

Summarizing, there is still an absence in the present field of electrical systems of a simple, robust, and physically motivated method for monitoring the health or degradation state of an electrical device subject to variable current load, which may be identified as a fault condition, before the actual fault of that condition develops into a failure occurring at a specific load. Also, it would be desirable to distinguish between fault conditions in the same or different electrical parts of the electrical system.

SUMMARY OF THE INVENTION

The above problem or need is at least partially solved or alleviated by the subject matters of the independent claims of the present disclosure, wherein further examples are incorporated in the dependent claims.

According to an aspect of the present disclosure, there is provided a method for determining a fault condition of an electrical part of an electrical system, the method comprising:

- obtaining measurement data indicative of a measured temperature profile of a temperature over time at one or more positions within the electrical system and a measured electrical current profile of an electrical current through the electrical part over time;

- obtaining characteristic data of the electrical part, the characteristic data comprising: o fault-free characteristic data indicative of a time dependency of the temperature of the electrical part from the electrical current through the electrical part under a fault-free operation of the electrical part, and optionally o at least one fault characteristic data indicative of a time dependency of the temperature of the electrical part from the electrical current through the electrical part under a fault operation of the electrical part associated with the fault condition; and

- determining the fault condition based on the measurement data and the characteristic data.

The method of the first aspect may in particular be an at least partially or fully computer implemented method. This means that at least one, multiple or all of the steps of the method may be carried out by a data processing system, which may comprise one or more computers or computing units, which may be part of the electrical system or not, e.g., integrated therewith or connected thereto. Different steps may be carried out by the same or by different computers. A computer is herein understood as a data processing apparatus or device, which can carry out some, multiple or all steps as defined by the method. Specifically, the obtaining of the measurement data, characteristic data and/or determining of the fault condition may be carried out by the data processing system. Additionally, or alternatively, the obtaining of the measurement data may be carried out by a measurement device or system, which may optionally forward the measurement data to the data processing system such that it may obtain the measurement data.

The method of the first aspect of this disclosure allows for accurate determination of a fault condition, which is based on measurement data of a temperature profile and an electrical current profile at or in the electrical system. In particular, one of several possible fault conditions may be determined. The fault condition may be a root cause of a fault of the electrical part that may occur. The temperature profile may be a temperature measured over time, e.g., a function or graph of temperature plotted over time or data points of temperature over time. The electrical current profile may be a measured electrical current over time, e.g., a function or graph of current plotted over time or data points of current over time. The electrical current profile may be indicative of a load profile of a load over time, or the electrical current profile may be the load profile. The load may be based on the electrical current and the electrical resistance of the electrical part. The electrical current may be of an AC or DC type, for example, where in the case of an AC type the current may be in general summarized over one or more cycles, e.g. meaning the root-mean-square value or similar.

The method of the first aspect is further based on characteristic data, which may reflect the time dependency of the temperature of the electrical part based on the electrical current through the electrical part at a fault-free operation and, optionally, under at least one fault operation of the electrical part by including the at least one characteristic data. Therein, the characteristic data may be predetermined characteristic data as further described herein.

The measurement data may accordingly reflect measured or, in other words, actual timedependent data about the temperature and electrical current or load of the electrical system under operation, whereas the characteristic data may reflect expected or predetermined, e.g., theoretical, simulated and/or experiment-based, time-dependent data about the temperature and electrical current or load of the electrical system for fault-free operation and, optionally, for at least one fault operation. Having both, the measurement data, and the characteristic data, it may be possible to determine a fault condition. That is, if the expected time-dependent data under fault-free conditions is different from the actual or measured time-dependent data, in particular, sufficiently different, a fault condition of the electrical part may be determined. If having both, the fault-free characteristic data and the at least one fault characteristic data in the characteristic data, it may further be possible to identify which, if any, of the fault characteristic data or possible fault conditions (or root causes or fault origins) is being experienced, captured by the characteristic data, based on the measurement data. Alternatively, e.g., when there is only a single fault characteristic data indicative of a single fault condition in the characteristic data, it may be possible to more accurately determine the fault condition, in particular whether the electrical part is healthy or faulty and, potentially, a fault type, origin, root cause and/or severity of the fault.

For example, the fault condition may be determined based on a fitting of the measurement data with the characteristic data. For example, one or more equations may be used as further specified herein below in the detailed description of the invention. The temperature profile of the temperature over time and the electrical current profile may be equated to the characteristic data and thereby the time dependency of the temperature of the electrical part from the electrical current, for determining that there is a delta or difference between the characteristic data and the measurement data in case only the fault-free characteristic data is comprised in the characteristic data. Or, if the characteristic data further comprises one or a single fault characteristic data associated with a specific or single fault condition, by equating the temperature profile of the temperature over time and the electrical current profile to the characteristic data, it may be determined whether the fault characteristic data accounts for part of the measurement data or not, the fault condition being determined if the first mentioned is the case. Or, if the characteristic data further comprises several fault characteristic data associated with a specific or several fault conditions, by equating the temperature profile of the temperature over time and the electrical current profile to the characteristic data, it may be determined which one or more, if any, of the several fault characteristic data account for part of the measurement data or not, the fault condition of the fault characteristic data being determined, which accounts for part of the measurement data. For the equating, in particular for solving the equation, the equation may be inverted or, in other words, invert conversion may be used, for example. The equation may accordingly be solved for the unknown fault characteristic data of the several fault characteristic data, i.e., it may be determined which of several fault characteristic data is responsible for the part of the measurement data going beyond or being in addition to the one caused by the fault-free characteristic data, which may be also referred to as a nominal characteristic data, for example.

The characteristic data may for example comprise at least two fault characteristic data, e.g., as explained above, each one of the at least two fault characteristic data being indicative of a time dependency of the temperature of the electrical part from the electrical current through the electrical part under a different one of two or more fault operations of the electrical part, each one of the two or more fault operations being associated with a different one of two or more fault conditions. The fault condition may be determined as at least one of the two or more fault conditions based on the measurement data and the characteristic data. Therein, the different fault conditions may have different or unique timedependent behaviors. Hence, it may be enabled that different fault conditions may be determined or distinguished from one another, which may require different handling, e.g., replacement of the electrical part or not.

In an example, the fault-free characteristic data may correspond to a fault-free thermal kernel and the at least one fault characteristic data may correspond to at least one fault thermal kernel. The respective thermal kernel may represent the thermal response (temperature over time) of the electrical part or electrical system at the position at which the temperature is measured, for a fault-free electrical part or for a faulty electrical part or electrical system. The thermal kernels may accordingly be seen as fingerprints of the time dependent behavior of the electrical part. Each one of the fault-free characteristic data and the at least one fault characteristic data, or each one of the thermal kernels, may be seen as a heating source for the measured temperature, wherein, for the purpose of determination, the heating sources may be added together in an equation as later described herein, in particular based on a linear assumption or superposition of the different characteristic data or thermal kernels. The thermal kernel may comprise a variable and/or a function. The respective characteristic data, in particular the thermal kernels, may be integrated in or by the method, for determining the fault condition, in particular in the equation previously described, in particular over the input history or time. In the equation or in or by the method, the respective characteristic data, in particular the thermal kernels, may be linearly combined, in particular superpositioned, with one another, as mentioned. The measured temperature profile or, in other words, temperature response may be fitted, e.g., with the mentioned equation, into a sum of the thermal kernels, and the equation may be solved, e.g., by inverting it and by, e.g., using a least square estimation technique. This, the equation, the thermal kernels, etc. are exemplary further described herein in more detail in the detailed description of the invention.

In an example, the method may be configured for determining a fault condition of one or more of a plurality of electrical parts of the electrical system, the method comprising: obtaining measurement data for at least one, in particular multiple of or each one, of the plurality of electrical parts or the plurality of electrical parts, the measurement data being indicative of a measured temperature profile of a temperature over time at one or more positions within the electrical system and a measured electrical current profile of an electrical current through one, each or all of the electrical parts over time;

- obtaining characteristic data for each one of the plurality of electrical parts, the characteristic data comprising: o fault-free characteristic data indicative of a time dependency of the temperature of each one of the plurality of electrical parts from the electrical current through each one of the plurality of electrical parts under a fault-free operation of each each one of the plurality of electrical parts, and o at least one fault characteristic data indicative of a time dependency of the temperature of each one of the plurality of electrical parts from the electrical current through each one of the plurality of electrical parts under a fault operation of each one of the plurality of electrical parts associated with the fault condition; and

- determining the fault condition of the one or more of the plurality of electrical parts based on the measurement data and the characteristic data.

In other words, the method may be used to determine fault conditions of one or more of a plurality of electrical parts of the electrical system. For example, the method may determine faults of two or more electrical parts of the electrical system, which may be like or, in other words, identically constructed or configured parts or different types of parts, for example. Additionally, as previously explained, different fault conditions may be determined among the electrical parts. For the measured temperature profile, a single measurement position within the electrical system may suffice. Alternatively, multiple measurement positions or measurement devices may be provided, e.g., within or at the electrical part or parts or nearby it or these.

In an example, the characteristic data may be predetermined based on one or more of at least one simulation of the electrical system, and at least one usage of the electrical system. The at least one usage may be under predetermined, experimental conditions and/or under operational condition, for example, e.g., in the application environment of the electrical system. The different types of characteristic data, i.e . , fault-free or fault characteristic data, may be determined based on the same principle or different from one another, for example.

For example, the fault condition may be based on an aging-related or, in other words, degradation-related increase of an electrical resistance of the electrical part and/or a change of electrical coupling of the electrical part, in particular to the environment and/or the electrical system and/or other electrical parts thereof or outside thereof. For example, the different fault conditions may be based on different electrical contact resistances that may have increased over operation time or lifetime of the electrical system or the electrical part. Alternatively, or additionally, the fault conditions may be based on any one of the aforementioned different types of basis for the fault condition or any other types. For example, the increased electrical resistance or the change of electrical coupling may be compared to a threshold, which may be predetermined, and indicative of the fault condition of the electrical part. In particular, the threshold may be chosen and/or the increase of the electrical resistance and/or the change of electrical coupling may be such that the fault condition exists only for a certain or predetermined load or electrical current, wherein the load or electrical current under normal or most operation may be below that such that the fault typically normally or typically does not manifest itself. Hence, by means of the method, a preemptive determination of a fault condition is possible before an actual fault would normally or in most cases manifest itself, enabling an exchange or maintenance of the electrical part before occurance of the fault.

For example, the electrical part may be an electrical contact, an electrical portion or an electrical component of the electrical system. Further, the electrical system may be formed by the electrical part or component (i.e., have only the electrical component, such that the electrical system as such is being checked for a fault condition) or may have multiple electrical parts or components. The electrical system may in particular be an electrical device. The electrical portion may be a portion of an electrical component, for example, and not necessarily the entire electrical component.

For example, the electrical part may be configured as or may be part of one of a circuit breaker and a switch, in particular an electrical switch, of the electrical system. It is noted that these are non-limiting examples and the electrical part may be configured as any other electrical component.

For example, the electrical system may be an electrical current distribution system, in particular one of a switchgear system, a busbar system, and an electrical filter system. It is noted that these are non-limiting examples and the electrical current distribution system may be configured as any other electrical current distribution system.

For example, the measured temperature may be based on a temperature measured by a temperature sensor of, e.g., on, the electrical system. The temperature sensor or device may be part of the electrical part or of a different component. It may be located at the one or more positions or configured to measure at the one or more positions of the electrical systems. Only one or several temperature sensors may be used. In addition, one or more electrical current and/or load sensors or measurement devices may be used, e.g., configured separate from the temperature sensor(s) or integrated therewith. According to a second aspect of this disclosure, there is provided a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to the first aspect of this disclosure.

The computer program product may be a computer program as such, meaning a computer program consisting of or comprising a program code to be executed by the computer.

Alternatively, the computer program product may be a product such as a data storage, in particular a computer-readable data storage medium, on which the computer program may be temporarily or permanently stored.

According to a third aspect of this disclosure, there is provided a data processing system configured to carry out the method according to the first aspect of this disclosure.

The data processing system may comprise one or more computers as previously described and, optionally, the computer program product of the second aspect of this disclosure.

According to a fourth aspect of this disclosure, there is provided an electrical system comprising an electrical part, a measurement arrangement configured to measure a temperature profile of a temperature over time at one or more positions within the electrical system and an electrical current profile of an electrical current through the electrical part over time, and the data processing system of the third aspect of this disclosure.

For example, the electrical system may also comprise several electrical parts. The measurement arrangement may comprise one or more temperature sensors and/or electrical current sensors or measurement devices, for example.

It is noted that the above aspects, examples and features may be combined with each other irrespective of the aspect involved.

The above and other aspects of the present disclosure will become apparent from and elucidated with reference to the examples described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS Exemplary embodiments will be further described with reference to Figures, wherein:

Figure 1 shows an electrical system; and

Figure 2 shows a method for determining a fault condition of an electrical part of the electrical system of Fig. 1 .

The Figures are schematic only and not true to scale. In principle, identical or like parts, elements and/or steps are provided with identical or like reference numerals in the Figures.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 schematically shows an electrical system 10 exemplary comprising several electrical parts 11 . As an example, three electrical parts 11 are shown, however, the number may be smaller, e.g., one or two electrical parts 11 , or larger, e.g., four or more electrical parts 11 . The electrical parts 11 may be like electrical parts 11 or different electrical parts 11. For example, the electrical system 10 may be an electrical current distribution system, such as but not limited to a switchgear system, a busbar system or an electrical filter system. The electrical parts 11 may be any electrical parts such as but not limited to electrical contacts, electrical portions and/or electrical components of the electrical system 10, e.g., circuit breakers and/or (electrical) switches.

A data processing system 13 may be part of the electrical system 10 or connected thereto, e.g., via a wire or wirelessly, in particular to one or more temperature and/or electrical current measurement devices 12 or sensors, exemplary shown with one for some of each electrical part 11 and exemplary positioned at each electrical part 11 . Alternatively, less or more temperature and/or electrical current measurement devices 12 may be provided. Also, or alternatively, the one or more measurement devices 12 may be located at a different position within the electrical system 10 or outside thereof but configured for measuring the temperature and/or electrical current therein. Moreover, the measurement devices 12 may be combinatory measurement devices 12 for both, the temperature and the electrical current measurement, in particular over time, or separate devices 12. Also, not all of the electrical parts 11 need to have measurement device 12, as shown for example by the electrical part 11 without measurement device 12.

The data processing system 13 may comprise a data processing device 14, in particular in the form of a processing or computing unit or a processor and a computer, and/or a computer program product 15, e.g., in the form of a computer program as such or in the form of a computer-readable storage medium, having stored thereon the computer program. When the computer program product 15 is executed by the data processing device 14, the method 100 shown in Fig. 2 is executed.

The background of the method 100 is that it is typical to monitor the thermal behavior of electrical systems 10 such as the one shown in Fig. 1 since overheating thereof and/or of one or more of its electrical parts 11 is one of the major causes for their failures. A difficulty for thermal monitoring is given by the variability in the electrical current or the thereon based load, which may causes varying heating by Joule’s effect. Variations may occur during daily operation but also across days or weeks of operation, depending on how the electrical system 10 is used and its specific application.

The variability of the electric current or load limits the applicability of approaches based on fixed temperature thresholds. Indeed, an electrical system 10, in particular a electrical part 11 thereof, may present a fault, e.g., the electrical part 11 being an electrical contact, an electrical portion of an electrical component, or a full electrical component, but never surpass such fixed threshold because of low loads being applied during its operation. However, when a higher load is applied and an excessive overtemperature is reached, it might be too late to maintainance or replace the electrical part 11 .

Summarizing, models based on thresholds may allow to detect a failure but do not allow to identify faults or fault conditions and to track degradation or aging of an electrical part 11 within an electrical system 10, in particular not based on an increased contact resistance of the electrical part 11 due to its operation over its lifetime.

Simple dynamic models based, e.g., on thermal networks have been explored. Thermal networks, specifically, are in principle suitable for the task of modeling the temperature response of an electrical part 11 and could be employed to track their degradation or health status and identify faults. However, an issue with thermal networks, which makes their practical usefulness doubtful, is that their parameters are difficult to identify from data, especially if only one or a limited number of temperature sensors are available. In addition, thermal networks are often parameterized using data from healthy systems or parts, which makes a change in a parameter symptomatic of a fault (e.g., the increase of an electrical contact resistance) and difficult to capture. Fully data-driven models, such as neural networks, can be employed to identify anomalies, and therefore faults, in the data transmitted by a temperature sensor. While these models could be effective in flagging an issue with the system or part, it is difficult to associate an anomaly to the variation of a specific physical parameters if the model is not based on physical principles itself.

Summarizing, there is still an absence in the present field of electrical systems 10 of a simple, robust, and physically motivated method for monitoring the health or degradation state of an electrical device or system subject to variable current load, which may be identified as a fault condition, before the actual fault of that condition occurs at a specific load. Also, it would be desirable to distinguish between fault conditions in the same or different electrical parts 11 of the electrical system 10.

Figure 2 schematically and exemplary illustrates a method 100 solving the aforementioned. Namely, the method 100 may be for determining a fault condition of one or more of the electrical parts 11 of the electrical system 10, which may be an electrical device, e.g., one of the aforementioned types of systems or devices. A fault condition may be associated with or relate to a degraded or aged state, in particular but not only in terms of increased electrical contact resistance or loss of contact for the electrical current to go through the respective electrical part 11 . As such, the fault does not necessarily need to occur and be recognized as such, specifically when the electrical current and thereby applied load is low enough during operation not to trigger or result in the fault. However, early recognition of the fault condition, i.e., that the electrical part 11 may experience the fault, may be beneficial, because then the electrical part 11 may be repaired, exchanged or similar before an actual fault occurs based on its fault condition, e.g., under a higher load during its operation.

For this purpose, the method 100 comprises in a step 101 obtaining measurement data. The measurement data may be indicative of a measured temperature profile of a temperature over time at one or more positions within the electrical system 10. As previously explained, for example, the position may be within or at one of the electrical parts 11 . Further, the measurement data may be indicative of a measured electrical current profile of an electrical current through the electrical part 11 over time. The measurement data may be obtained by the one or more measurement devices 12 and/or the data processing system 13, e.g., the measurement data being forwarded to the data processing system 13. The measurement data may accordingly represent, reflect and/or comprise temperature measurements and electrical current measurements over time of the operation of the electrical system 10.

Further, the method 100 comprises in a step 102 obtaining characteristic data of the electrical part 12 for which the fault condition is to be determined. The characteristic data may be obtained by the data processing system 13. The step 102 may be carried out before, after or simulatenously to step 101 of the method 100. The characteristic data may comprise different kinds of characteristic data, namely one or both of a fault-free characteristic data and one or more fault characteristic data.

The fault-free characteristic data may be indicative of a time dependency of the temperature of the electrical part 11 from the electrical current through the electrical part 11 under a fault-free operation of the electrical part 11 . The fault-free characteristic data may thereby reflect the expected temperature depending on the electrical current through the electrical part 11 over time, when the electrical part 11 is healthy or, in other words, not significantly aged or degraded, and thereby not likely to experience a fault, hence being a fault-free electrical part 11 . The method 100 may thereby deal with the time-dependent or dynamic load conditions of the electrical part 11 based on physical considerations about the heat transfer in the electrical system 10, i.e. , based on the characteristic data, and is therefore able to determine a fault from temperature and electrical current measurements.

When the characteristic data comprises only the fault-free characteristic data, in a step 103 of method 100, which may follow steps 101 and 102, the fault condition may be determined, based on the measurement data and the characteristic data. In particular, a discrepancy between the measurement data and the characteristic data, in particular between the measured temperature profile and measured electrical current profile and the time dependency of the temperature from the electrical current, may suggest that a fault condition is present. In other words, because the measured temperature profile and measured electrical current profile deviate, in particular by at least a threshold over time, from the expected time dependency of the temperature for the measured electrical current for a fault-free operation of the electrical part 11 , it may be assumed that a fault condition is present or, in other words, the electrical part 11 is faulty, e.g., having an increased electrical contact resistance or loss of electrical contact, which may be a potential cause for a later fault.

The method 100 may also or alternatively be performed with step 103 of method 100, which may be carried out after the steps 101 and 102, if the characteristic data comprises both, the fault-free characteristic data and one or more of the fault-characteristic data. The at least one fault characteristic data may be indicative of a time dependency of the temperature of the electrical part 11 from the electrical current through the electrical part 11 under a fault operation of the electrical part 11 associated with the or a (certain) fault condition. In other words, for the particular or certain fault condition, the time dependency of the temperature of the electrical part 11 from the electrical current may be known, e.g., by means of predetermination. By obtaining the characteristic data, the data processing system 13 may be provided with this knowledge.

In the case of the characteristic data comprising both, the fault-free characteristic data and one or more of the fault-characteristic data, the determination of the fault condition may be made more reliably and/or the specific or certain fault condition of the electrical part 11 may be determined. For example, the determining of the fault condition may be based on a fitting of the measurement data with the characteristic data, which is now further explained in terms of the computational operation of the data processing system 13, by means of exemplary mathematical formulas or equations as basis thereof.

For example, the fault-free characteristic data may correspond to or be provided as a fault- free thermal kernel and the at least one fault characteristic data may correspond to or be provided as at least one fault thermal kernel. The thermal kernels may be denoted as k. The thermal kernels may represent the thermal response (temperature over time) of the electrical part 11 at the position at which the temperature is measured, for a fault-free electrical part 11 and for a faulty electrical part 11 . The measured temperature may be denoted as T(t), where t may denote the time. The thermal kernel, e.g., in the case of having only fault-free characteristic data in the characteristic data or, in other words, having only the fault-free thermal kernel, may link the effect of the thermal load, which may be denoted by L, with the temperature T(t), e.g., by the equation (1): The temperature increase of the electrical part(s) 11 and/or the electrical system 10 may be based on the electrical current running through these and based on Ohmic heating. In case of Ohmic heating of the electrical part 11 , typically L(s) = /?/²(s) applies, where R denotes the electrical resistance and I is the electrical current. The thermal kernel k describes the thermal response of a healthy or fault-free electrical part 11 at the position of the temperature measurement, e.g., at the location of the temperature measurement device 12. For example, the electrical resistance of the electrical part 11 may be below a threshold, qualifying it as healthy or fault-free. The equation (1) is physically motivated by the Green’s function formulation of the solution of the heat equation.

It may be assumed that there are N additional thermal loads Lj with I = 1 , ... , N that are associated to a change in the electrical losses in the electrical part 11 of the electrical system 10, and that the thermal response due to these additional thermal loads is added linearly, in particular by superposition, on top of the healthy or fault-free temperature profile or dependency. Moreover, it may be assumed that the temperature response at the position of measurement associated to each additional load has the same form as equation (1), i.e. , the convolution with appropriate thermal kernels kj, so that the temperature including the one or more fault thermal kernels kj can be written as equation (2):

This assumption is in general valid, if the thermal heat equation of the electrical system 10 remains approximately linear. Due to the different spatial distributions for the loads Lj and L, the fault thermal kernels kj differ from each other and also differ from the fault-free thermal kernel k. Also, the fault-related load(s) Lj(t) may have a different time dependency than fault-free-related load L(t), i.e., the ratio of the loads may not be constant, but in case of a pure electrical resistance variation, the loads may be proportional to each other. Even then, the associated thermal kernels kj have different time response characteristics. This can be used to identify and distinguish the different fault conditions or cases, that is, which part has an anomalous additional load Lj with respect to the nominal healthy or fault-free electrical part 11 response.

Both or any one of the fault-free characteristic data and the fault characteristic data may be predetermined based on at least one simulation of the electrical system 10 and/or at least one usage of the electrical system 10, for example. In particular, the fault-free thermal kernel k may be determined by dedicated usage or experiments and the additional fault thermal kernels kj may either be determined by dedicated use, experiments and/or by simulations. The thermal kernel k describing the fault-free, nominal or initial healthy temperature over electrical current behavior of the electrical part 11 can be determined when the electrical system 10 is fielded to adapt the method 100 to its environmental conditions.

The determination of the additional loads Lj, or more general the detection of new, abnormal heating sources in the electrical system 10 can be done when the electrical system 10 is not operated in steady conditions, but the electric current changes over time. In particular, the determination of the fault condition may be determined based on measurement data obtained during a period of a temperature increase over time, in particular a substantially and fast enough, in particular substantially exponential, temperature increase and/or wherein the period of the temperature increase over time may be during a start-up phase of the electrical part or between steady-state temperatures of the electrical part, for example. In the case of multiple temperature measurements, multiple thermal kernels can be used, e.g., describing the effect of a fault condition on the measurement. This may lead to a large number of equations (one for each measurement) that can be used to obtain a predicted temperature behaviour and to identify and quantify a fault condition.

In the case of Ohmic losses, all loads may take the form of L_t = RJ² , where it may be assumed that the same current is flowing through all positions of Ohmic heatings of the electrical system 10. Therefore, conditions where the current switches to a new, but approximately constant mode can be used for the analysis, as well as if the current is variable over time. Alternatively, if the current is measured, an analysis which instead of Lj determines the corresponding Rj can be used. In this case, the detection of fault conditions and the origin of the fault becomes independent of the operating conditions. Extensions to the case where the current I might be different for different positions are easy to derive, as long as the current through each position is known.

Determining Lj or Rj is in general efficient and robust because of the linear nature of the problem. For instance, least square estimation techniques are suitable for this purpose, in particular for the case of the linear assumption made above. While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the claims.

As used herein, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Further, as used herein, the phrase “at least one” or similar, e.g., “one or more of’, in reference to a list of one or more entities should be understood to mean at least one entity selected from any one or more of the entities in the list of entities, but not necessarily including at least one of each and every entity specifically listed within the list of entities and not excluding any combinations of entities in the list of entities. This definition also allows that such entities may optionally be present other than the entities specifically identified within the list of entities to which the phrase “at least one” or similar refers, whether related or unrelated to those entities specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B” or, equivalently “at least one of A and/or B” or, equivalently “one or more of A and B”, “one or more of A or B”, or “one or more of A and/or B”) may refer, in one example, to at least one, optionally including more than one, A, with no B present (and optionally including entities other than B); in another example, to at least one, optionally including more than one, B, with no A present (and optionally including entities other than A); in yet another example, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other entities). In other words, the phrases “at least one,” “one or more,” and “and/or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B, and C,” “at least one of A, B, or C,” “one or more of A, B, and C,” “one or more of A, B, or C,” and “A, B, and/or C” may mean A alone, B alone, C alone, A and B together, A and C together, B and C together, A, B, and C together, and optionally any of the above in combination with at least one other entity. As used herein, the phrase “being indicative of’ may for example mean “reflecting” and/or “comprising”. Accordingly, an entity, element and/or step referred to herein as “being indicative of [...]” can be synonymously or interchangeably used herein with one, two or all of said entity, element and/or step “comprising [.. and said entity, element and/or step “reflecting Further, as used herein, phrases such as “based on”, “related” or “relating”, “associated” and similar are not to be seen exclusively in terms of the entities, elements and/or steps to which they are referring, unless otherwise stated. Instead, these phrases are to be understood inclusively, unless otherwise stated, in that, for example, an entity, element or step referring by any of these phrases or similar, e.g., being “based on”, an or another entity, element or step, does not exclude that the respective entity, element or step may be further or also “based on” any other entity, element or step than the one to which it refers.

The designation of methods and steps as first, second, etc. as provided herein is merely intended to make the methods and their steps referenceable and distinguishable from one another. By no means does the designation of methods and steps constitute a limitation of the scope of this disclosure. For example, when this disclosure describes a third step of a method, a first or second step of the method do not need to be present yet alone be performed before the third step unless they are explicitly referred to as being required per se or before the third step. Moreover, the presentation of methods or steps in a certain order is merely intended to facilitate one example of this disclosure and by no means constitutes a limitation of the scope of this disclosure. Generally, unless no explicitly required order is being mentioned, the methods and steps may be carried out in any feasible order. Specifically, the terms first, second, third or (a), (b), (c) and the like in the description and in the claims are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

In the context of the present invention any numerical value indicated is typically associated with an interval of accuracy that the person skilled in the art will understand to still ensure the technical effect of the feature in question. As used herein, the deviation from the indicated numerical value is in the range of ± 10%, and preferably of ± 5%. The aforementioned deviation from the indicated numerical interval of ± 10%, and preferably of ± 5% is also indicated by the terms “about” and “approximately” used herein with respect to a numerical value.

Any reference signs in the claims should not be construed as limiting the scope.

Claims

1 . A method (100) for determining a fault condition of an electrical part (11 ) of an electrical system (10), the method (100) comprising: obtaining measurement data indicative of a measured temperature profile of a temperature over time at one or more positions within the electrical system (10) and a measured electrical current profile of an electrical current through the electrical part (11) over time; obtaining characteristic data of the electrical part (11), the characteristic data comprising fault-free characteristic data indicative of a time dependency of the temperature of the electrical part (11) from the electrical current through the electrical part (11 ) under a fault-free operation of the electrical part (11 ); and determining the fault condition based on the measurement data and the characteristic data.

2. The method (100) of claim 1 , the characteristic data further comprising at least one fault characteristic data indicative of a time dependency of the temperature of the electrical part from the electrical current through the electrical part under a fault operation of the electrical part associated with the fault condition.

3. The method (100) of claim 2, wherein the characteristic data comprises at least two fault characteristic data, each one of the at least two fault characteristic data being indicative of a time dependency of the temperature of the electrical part (11 ) from the electrical current through the electrical part (11) under a different one of two or more fault operations of the electrical part (11), each one of the two or more fault operations being associated with a different one of two or more fault conditions, and wherein the fault condition is determined as at least one of the two or more fault conditions based on the measurement data and the characteristic data.

4. The method (100) of claim 2 or 3, wherein the fault-free characteristic data corresponds to a fault-free thermal kernel and the at least one fault characteristic data corresponds to at least one fault thermal kernel.

5. The method (100) of any one of claims 2 to 4, wherein the method (100) is configured for determining a fault condition of one or more of a plurality of electrical parts of the electrical system, the method comprising: obtaining measurement data for at least one of the plurality of electrical parts or the plurality of electrical parts, the measurement data being indicative of a measured temperature profile of a temperature over time at one or more positions within the electrical system (10) and a measured electrical current profile of an electrical current through one, each or all of the electrical parts (11) over time;

- obtaining characteristic data for each one of the plurality of electrical parts (11), the characteristic data comprising: o fault-free characteristic data indicative of a time dependency of the temperature of each one of the plurality of electrical parts (11) from the electrical current through each one of the plurality of electrical parts (11 ) under a fault-free operation of each each one of the plurality of electrical parts (11), and o at least one fault characteristic data indicative of a time dependency of the temperature of each one of the plurality of electrical parts (11) from the electrical current through each one of the plurality of electrical parts (11 ) under a fault operation of each one of the plurality of electrical parts (11) associated with the fault condition; and

- determining the fault condition of the one or more of the plurality of electrical parts (11 ) based on the measurement data and the characteristic data.

6. The method (100) of any one of the previous claims, wherein the fault condition is determined based on a fitting of the measurement data with the characteristic data.

7. The method (100) of any one of the previous claims, wherein the characteristic data is predetermined based on one or more of o at least one simulation of the electrical system (10), and o at least one usage of the electrical system (10).

8. The method (100) of any one of the previous claims, wherein the fault condition is based on an aging-related increase of an electrical resistance of the electrical part (11) and/or a change of electrical coupling of the electrical part (11). -zz-

9. The method (100) of any one of the previous claims, wherein the electrical part (11 ) is an electrical contact, an electrical portion or an electrical component of the electrical system (10).

10. The method (100) of any one of the previous claims, wherein the electrical part (11 ) is configured as or is part of one of a circuit breaker and/or a switch of the electrical system (10).

11 . The method (100) of any one of the previous claims, wherein the electrical system (10) is an electrical current distribution system, in particular one of a switchgear system, a busbar system, and an electrical filter system.

12. The method (100) of any one of the previous claims, wherein the measured temperature is based on a temperature measured by a temperature sensor (12) of the electrical system (10).

13. A computer program product (15) comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method (100) of any one of the previous claims.

14. A data processing system (13) configured for carrying out the method (100) of any one of the claims 1 to 12.

15. An electrical system (10) comprising an electrical part (11), a measurement arrangement configured to measure a temperature profile of a temperature over time at one or more positions within the electrical system (10) and an electrical current profile of an electrical current through the electrical part (11) over time, and the data processing system (13) of claim 14.