Electrical system with a capacitor element

Abstract

Electrical system (100) comprising at least one capacitor element (10), at least one sensor (20, 20', 20'') configured to measure at least one parameter selected from device parameters (D) and environmental parameters (E), and a processing unit (30) configured to process the at least one parameter and evaluate a capacitor element information (CEI) of the at least one capacitor element based on the at least one parameter, wherein the capacitor element information includes one or more values ​​selected from a capacitance loss, a tangent change, a load, a remaining lifetime, and a fault condition.

Description

Embodiments relate to an electrical system having a capacitor element.Capacitors such as foil capacitors or aluminum capacitors are used in numerous applications. For example, converters that serve to adapt electrical supply signals to the required parameters of electrical devices contain such capacitor elements as basic components that are required for a proper function. In the case of foil capacitors, however, there is the risk of premature ageing, for example as a result of damage to the insulation resistance, which can lead to pyrolysis processes of the dielectric polymer used in the capacitor. The pyrolysis process can produce flammable gases due to the decomposition of the polymer material. When the housing of the condenser is leaky, these gases can escape into the environment. Consequently, there is a risk of explosion when these gases are released. Aging may be caused by a combination of environmental and operating conditions that may affect the various degradation mechanisms in various ways, such as self-healing, electrochemical corrosion, or mechanical degradation.To date, the main solution to avoid unexpected capacitor failure is to measure the capacitance and dissipation factor and compare these parameters to previous measurements, as well as to visually inspect them. Prior to measurement and testing, disconnection from the circuit is usually required.At least one object of certain embodiments is to provide an electrical system having at least one capacitor element.This object is achieved by an object according to the independent claim. Advantageous embodiments and further developments of the subject matter are characterized in the dependent claims and are also disclosed by the following description and the drawings.According to at least one embodiment, an electrical system has at least one capacitor element. The capacitor element can also be referred to below for short as a capacitor and can be a foil capacitor, for example. A foil capacitor typically comprises a dielectric polymer foil provided with electrodes. The electrodes of foil capacitors may be of metallized aluminum or zinc applied directly to the surface of the polymer foil or of a separate metal foil. To form a capacitor body, two of these conductive layers may be wound into a cylindrical coil or stacked as a plurality of individual layers. The capacitor element may also be another type of capacitor, e.g., an aluminum electrolytic capacitor. Moreover, the electrical system may include a plurality of capacitor elements, and the following description may apply to each of the plurality of capacitor elements.Furthermore, a method for monitoring the at least one capacitor element in an electrical system is specified. For the electrical system with the at least one capacitor element and for the method for monitoring the at least one capacitor element in the electrical system, the same applies as described above and below.According to a further embodiment, at least one parameter is measured, wherein the at least one parameter is selected from device parameters and environmental parameters. Furthermore, on the basis of the at least one measured parameter, capacitor element information of the at least one capacitor element can be evaluated. Accordingly, the electrical system may include at least one sensor configured to measure at least one parameter selected from the device parameters and the environmental parameters. Furthermore, the electrical system can have a processing unit which is configured to process the at least one parameter and to evaluate capacitor element information of the at least one capacitor element on the basis of the at least one parameter.Here and in the following, a device parameter can be, in particular, a parameter which relates directly to the capacitor element or at least one component thereof and / or to the electrical system or at least one component thereof, while an environmental parameter can be, for example, a parameter of the atmosphere which surrounds the capacitor element and / or the electrical system. A device parameter of a device may be an electrical parameter, such as an electrical voltage and / or an electrical current applied to the device, or a temperature of the device, or at least a component thereof. A sensor configured to measure a device parameter may be, for example, a voltage sensor, a current sensor or a temperature sensor and may be directly coupled to the device, for example, by a mechanical contact or by an inductive coupling or by an optical coupling. An environmental parameter may be, for example, the temperature of the atmosphere surrounding the condenser element or the concentration of one or more gas species contained in the atmosphere surrounding the condenser element, or vibrations or mechanical shocks. A sensor configured to measure an environmental parameter may be, for example, a temperature sensor or a gas sensor, which may preferably be arranged in the atmosphere surrounding the capacitor element, or a vibration sensor arranged in contact with a component of the electrical system.The electrical system can be, for example, a converter for converting an electrical signal, which is characterized by an electrical voltage, an electrical current and / or a frequency, into another electrical signal. For example, the converter is configured to convert a high voltage AC input signal having a particular frequency to an output signal having a different voltage and / or frequency. In addition, the electrical system may be another electrical device that includes at least one capacitor element.According to a further embodiment, during the operation of the electrical system and / or of the at least one capacitor element, the at least one parameter is measured in real time and the capacitor element information is evaluated in real time. Thus, the capacitor element information of the at least one capacitor element can be obtained during the operation of the electrical system, and no switching off, switching off or other intervention in the electrical system is necessary in order to obtain the at least one capacitor element information. Moreover, information may be provided to an operator of the electrical system on the basis of the capacitor element information. Preferably, the at least one parameter is continuously measured during operation of the electrical system. Moreover, it may also be possible for the at least one parameter to be measured continuously when the electrical system or at least parts thereof are shut down or even switched off. Continuous execution of a measurement can mean, in particular, that the measurement is carried out repeatedly, for example in specific measurement time intervals which are separated by measurement-free time intervals without execution of the measurement, or even permanently, i.e. substantially or even completely uninterrupted by measurement-free time intervals. The measurement of the at least one parameter can be carried out, for example, every few minutes or every few seconds or every 2 seconds or every 1 second or every 100 ms or else at shorter time intervals or permanently. The same can also apply to the evaluation of the capacitor element information by the processing unit.In particular, the electrical system and method described herein may provide one or more safety means, which may be used alone or in combination to provide an integral safety environment for the at least one capacitor element during operation. In particular, the one or more safety means can be implemented in the electrical system such that the electrical system can acquire data and process and evaluate the data further in order to obtain information about the at least one capacitor element. Based on the obtained information, for example, a status report or an alarm can be generated in order to inform an operator about the state of the capacitor element and / or about measures to be taken.According to a further embodiment, the capacitor element information comprises one or more states of the capacitor element, which can be used for determining a current state of the capacitor element and / or possible measures to be taken, and in particular can comprise one or more values selected from a capacitance loss, a tangent change, a load, a remaining lifetime and a fault state. In particular, the capacitor element information may be an instantaneous value or a temporal development of a value. Thus, the capacitor element information may include one or more values selected from a momentary loss of capacitance, a temporal evolution of the loss of capacitance, a momentary change of tangent, a temporal evolution of the change of tangent, a momentary voltage, a voltage accumulated over time, a remaining lifetime, and an error condition. The loss of capacitance, the change of tangent and / or the voltage can contribute to a state of aging of the capacitor element, for example. The stress can be caused in particular by mechanical stress and / or electrical stress and / or temperature-induced stress. Temperature-related stress may be caused by the temperature of the capacitor element or a component thereof and / or by the temperature of the environment. Electrical voltages may be caused by the voltage and / or current applied to the capacitor element. Mechanical loading may be caused by vibrations and / or mechanical shocks acting directly on the capacitor element and / or indirectly via other components of the electrical system. A fault condition may be a state of the capacitor element that may cause a harmful and / or hazardous situation for the electrical system.According to a further embodiment, the evaluation of the capacitor element information can take place on the basis of empirical models and / or simulations and / or determined threshold values. In particular, the evaluation can preferably be carried out with the aid of mathematical formulas and / or algorithms that are based on empirical models and / or simulations and / or determined threshold values. The models, simulations and threshold values can be specifically adapted to the at least one capacitor element, so that different mathematical formulas and / or algorithms are used for different capacitor elements, for example. The processing unit can comprise or be, for example, a microprocessor or a personal computer.The evaluated states in the form of the evaluated capacitor element information can be monitored and checked in real time in order, for example, to ensure that the capacitor element meets the specification, i.e. is in a proper operating state, and / or to determine the state of aging and / or to ensure that one can react correctly to the evaluated state if necessary. In particular, the measured characteristic(s) and / or the capacitor element information can / can be stored and used for monitoring and / or as a basis for decision, e.g. for the further use or the replacement of the capacitor element.According to a further embodiment, a plurality of parameters selected from device parameters and environmental parameters are measured, wherein the parameters can be processed individually and / or in combination for evaluating the capacitor element information. Consequently, the at least one sensor of the electrical system can comprise or be a plurality of sensors which are designed to measure a plurality of parameters selected from device parameters and environmental parameters.According to a further embodiment, the at least one sensor comprises one or more sensors configured to measure an electrical operating state of the capacitor element and / or of the electrical system or of a component thereof. The electrical state can be an operating voltage which is preferably present at the at least one capacitor element and / or an operating current which is preferably present at the at least one capacitor element. Furthermore, the at least one sensor can comprise one or more sensors which are designed to measure a temperature of the at least one capacitor element or of a component thereof. In particular, the at least one sensor may comprise one or more sensors configured to measure at least one DC voltage, a DC current, a ripple voltage and a temperature of a maximum temperature, which may also be referred to as a hot spot, of the at least one capacitor element or of a housing of the at least one capacitor element. If the temperature of the housing of the at least one capacitor element is measured, the processing unit may be configured to estimate a hot-spot temperature within the housing of the at least one capacitor element based on the measured temperature of the housing. The temperature sensor can be, for example, a thermocouple which is connected mechanically or by adhesive to the housing of the capacitor element.The electrical system particularly preferably has at least one first sensor, which is configured to measure an electrical operating state of the capacitor element and / or of the electrical system, and at least one further sensor, which is configured to measure the temperature of the capacitor element. Additionally or alternatively, the at least one sensor preferably comprises one or more sensors configured to measure one or more ambient humidity(s), an ambient temperature, mechanical actions such as vibrations and mechanical shocks, one or more gas types. Accordingly, the environmental parameters may be selected from an environmental humidity, an environmental temperature, vibrations, one or more gas species.In particular, the one or more gas type(s) may be selected from a gas type that may arise during a pyrolysis event of one or more components of the capacitor element. The pyrolysis event is an example of a failure condition of the capacitor element that may represent a potential risk of damage to the electrical system. The gas species measurement may also be referred to as a pollution measurement, with which the pollution can be determined with respect to a potentially harmful gas species in the electrical system. As explained above, the capacitor element may be a foil capacitor with a polymer foil or another capacitor that contains a polymer component that can be pyrolyzed in the case of too high a temperature in the housing of the capacitor element. Pyrolysis can produce one or more combustible gas species. The polymer may include or be, for example, polypropylene (PP), which may decompose into propylene, methane, propane, etc. Alternatively or additionally, the polymer film can comprise or be one or more of the following materials: polyethylene terephthalate, polyester (PET), polyphenylene sulfide (PPS), polyethylene naphthalate (PEN), polycarbonate (PP), polystyrene (PS) and polytetrafluoroethylene (PTFE). In the event of a leak in the housing, the decomposition gases can escape from the housing and lead to an explosion when a specific concentration in the environment is reached. Based on the gas measurement, the concentration may be monitored and as the concentration approaches or reaches the flammability threshold (LFL), a warning or alarm may be triggered.Further advantages, advantageous exemplary embodiments and further developments result from the exemplary embodiments described below in connection with the figures, in which:FIGS. 1A and 1B show schematic representations of an electrical system having at least one capacitor element and a method for monitoring the at least one capacitor element in an electrical system according to a plurality of exemplary embodiments.In the exemplary embodiments and figures, identical, similar or identically acting elements are each provided with the same reference numerals. The elements shown and their size relationships to one another are not to be regarded as true to scale, rather individual elements, such as layers, components, devices and regions, may have been shown excessively large for better illustration and / or for better understanding.FIG. 1A shows an electrical system 100 having at least one capacitor element 10; FIG. 1B shows a method for monitoring the at least one capacitor element 10 in the electrical system. The following description applies equally to FIGS. 1A and 1B.Although the electrical system 100 is illustrated as having exactly one capacitor element 10, the electrical system 100 may include more than one capacitor element 10. The following description of features and embodiments with respect to the shown one capacitor element 10 may therefore apply similarly to any of a plurality of capacitor elements in the electrical system 100. For example, the electrical system 100 may include an inverter or may be an inverter, as discussed in the general part. Alternatively, the electrical system may also be any other electrical device that includes at least one capacitor element. The at least one capacitor element 10 may be, for example, a foil capacitor having one or more electrode layers separated by a polymer material comprising or consisting of, for example, polypropylene. Alternatively or additionally, other types of capacitor elements are also possible.The electrical system 100 further comprises a system space 90, in which the at least one capacitor element 10 is located. The system space 90 can house in particular further or even all electrical and electronic components of the electrical system 100 and can also be referred to as a chamber. Furthermore, the electrical system has one or more sensors 20, 20', 20". Three sensors 20, 20', 20" are shown in FIG. 1A only by way of example. However, fewer or more than the three sensors shown are also possible. Depending on the respective sensor type, each of the sensors 20, 20', 20" is configured such that, in a method step 1, as illustrated in FIG. 1B, it measures at least one parameter selected from device parameters D and environmental parameters E.In addition, in a method step 2, as illustrated in FIG. 1B, the electrical system 100 comprises a processing unit 30 which is configured to process the one or more parameters D, E and to evaluate capacitor element information CEI of the at least one capacitor element 10 on the basis of the at least one parameter D, E. Although the processing unit 30 is illustrated outside the system space 90 in FIG. 1A, the processing unit 30, or at least portions thereof, may also be disposed within the system space 90.By performing one or more evaluations, the processing unit 30 may provide capacitor element information CEI, wherein the capacitor element information CEI includes one or more information selected from a capacitance loss, a tangent change, a voltage, a remaining lifetime, and a fault condition, as generally explained in the Background Art.During the operation of the electrical system 100 and / or of the at least one capacitor element 10, the at least one parameter D, E can be measured in real time in method step 1 and the capacitor element information CEI can be evaluated in real time in method step 2. Furthermore, on the basis of the capacitor element information CEI, information can be provided to an operator of the electrical system, which is indicated as method step 3 in FIG. 1B. Method step 3 may also comprise monitoring and / or storing the CEI and / or the one or more measured parameters D, E. Preferably, the at least one parameter D, E is continuously measured during operation of the electrical system, as explained in the general part. Moreover, it may also be possible for the at least one parameter D, E to be measured continuously when the electrical system 100 or at least parts thereof are shut down or even switched off.The sensors 20, 20', 20" may be configured to measure one or more of the following device parameters D and environmental parameters E: an electrical operating state of the capacitor element 10 and / or the electrical system 100, or a component thereof, may be measured, as indicated by the example sensor 20 in FIG. 1A. The electrical state can be an operating voltage which is preferably present at the at least one capacitor element 10 and / or an operating current which is preferably present at the at least one capacitor element 10. Moreover, a temperature of the at least one capacitor element 10 may be measured as indicated by the example sensor 20' in FIG. 1A. Consequently, the electrical system 100 may include one or more sensors configured to measure at least a DC voltage, a DC current, a ripple voltage and a temperature at a hot spot of the at least one capacitor element or a housing of the at least one capacitor element. If the temperature of the housing of the at least one capacitor element is measured, as shown in FIG. 1A, the processing unit 30 may be configured to estimate a maximum temperature within the housing of the at least one capacitor element, which may also be referred to as a hot spot, based on the measured temperature of the housing. Temperature sensor 20' may be, for example, a thermocouple attached to the housing of capacitor element 10.Moreover, one or more ambient humidity(s), ambient temperature, mechanical impacts such as vibrations and mechanical shocks, one or more gas species may be measured as indicated by the example sensor 20" in FIG. 1A. Accordingly, the environmental parameters E may be selected from, for example, an environmental humidity, an environmental temperature, vibrations, one or more gas species.Preferred aspects of the electrical system and method are described below, which comprise preferred safety means and methods for operating the electrical system and the capacitor element. All aspects may be implemented individually or combined together, thereby combining multiple safety means and methods in the electrical system 100. Moreover, all aspects may be combined with the features and embodiments described in the general part.Aspect 1: The method uses the data of one or more different sensors, e.g. selected from sensors that measure one or more of the following quantities: temperature, electrical properties, vibrations, humidity, contamination, etc., which are acquired as real-time data from the system room and / or the capacitor. This data is processed by the processing unit, i.e., a microprocessor or personal computer, and various calculations such as the development of the capacity loss, the development of the tangent change, the voltage, the remaining life, etc. are performed based on algorithms and mathematical formulas and models. Operating conditions are monitored and checked in real time to ensure that the capacitor meets specifications and that action can be taken as needed.Aspect 2: In conjunction with and in addition to Aspect 1, the method further comprises the real-time detection of the electrical conditions of the electrical system and / or of the capacitor and the temperature at or in the housing or at a hotspot of the capacitor. With the data acquired, the system may be able to calculate the current strain and calculate the previous capacity losses over time and estimate the capacity losses over time in the future using the history of the strains. The remaining lifetime can also be calculated with these data.Aspect 3: In conjunction with and in addition to Aspect 1, the method further includes real-time detection of one or more parameters of the environment of the electrical system and / or the system space and / or the capacitor, e.g., one or more parameters such as humidity, temperature, vibrations, etc. Conditions may be checked based on the detected data to find situations that may negatively affect the electrical system and / or the capacitor. An algorithm receives these data as inputs, interprets them, and can generate an alarm with detailed information according to certain thresholds and rules.Aspect 4: In conjunction with and in addition to claim 1, the method further comprises detecting contamination in the system space in real time such that gas leakage from one or more of the condensers can be detected. The change in fouling may be caused by an increase in the concentration of gases formed during pyrolysis of the polymer, e.g., polypropylene, of the capacitor element, which may form one or more gas species such as propylene, methane, propane, etc., that are flammable even at low concentrations. The values may be stored and used to monitor and / or trigger an alarm when the gas concentration is near the lower flammability limit (LFL).Aspect 5: The electrical system has a number of sensors of different types, e.g. sensors for measuring temperature, electrical parameters, vibrations, moisture, dirt etc., which acquire real-time data from the system space and / or the capacitor. This data is processed by the processing unit, i.e., a microprocessor or personal computer, and various calculations such as the development of the capacity loss, the development of the tangent change, the voltage, the remaining life, etc. are performed based on algorithms and mathematical formulas and models. Operating conditions are monitored and checked in real time to ensure that the capacitor meets specifications and that action can be taken as needed.Aspect 6: In connection with and in addition to aspect 5, the electrical system has at least one sensor which measures the electrical operating conditions of the electrical system and / or of the capacitor in real time, and at least one sensor which measures the temperature on or in the housing or on a hotspot of the capacitor in real time. The acquired data is received by the processing unit and capacity loss, tangent change, voltage and / or remaining lifetime is calculated based on algorithms and mathematical formulas and models. These values may be stored and used for monitoring and / or as a basis for decisions.Aspect 7: In conjunction with and in addition to aspect 5, the electrical system has at least one sensor which measures the environmental conditions of the operation of the electrical system and / or of the system space and / or of the environment of the capacitor, for example room temperature, humidity, vibrations etc., in real time. The captured data is received by the processing unit and the environmental conditions are checked using algorithms and thresholds to determine whether the capacitor can meet the conditions and to determine the aging that has already occurred. The values may be stored and used for monitoring and / or as a basis for decisions.Aspect 8: In conjunction with and in addition to Aspect 5, the electrical system has at least one sensor which measures the contamination of the system space in real time. The acquired data is received by the processing unit and based on algorithms and thresholds the gas level is checked to determine if gases exit the condenser through the housing, indicating an internal fault. The values are stored and may be used for monitoring and / or alarm when the gas level is close to the low flammability limit (LFL).As a result of aspects 2 and 6, unexpected higher voltages can be detected and measured with accuracy. This results in a loss of capacitance and a shortening of the service life. If the expected lifetime is less than indicated, measures can be taken early to replace or re-design the capacitor. If the load is less than expected, another capacitor may be selected for use, thus saving cost and space.As a result of aspects 3 and 7, the states and their effects on the capacitor are recognized at an early stage, so that measures can be taken and further damage can be avoided.As a result of aspects 4 and 8, gas leakage can be detected before the low flammability limit (LFL) concentration is reached, thereby avoiding a catastrophic situation.According to aspects 2 and 6, electrical and / or thermal measured variables are monitored and continuously used in real time for the calculation of voltage, capacitance loss and service life and also the fluctuations thereof. To date, capacity and loss factor during maintenance have been measured manually.According to aspects 3 and 7, ambient conditions can be detected so early that measures can be taken to modify or mitigate their effect. To date, these conditions are usually not checked in real time, for example in converters, and thus also not taken into account in their effect on the capacitors.According to aspects 4 and 8, gas leakage may be detected before the severe flammability limit is reached in the system room, thereby avoiding a catastrophic situation. To date, noxious gases are not controlled and have caused explosion.Alternatively or in addition to the features described in connection with the figures, the exemplary embodiments shown in the figures can have further features described in the general part of the description. In addition, features and exemplary embodiments of the figures can be combined with one another, even if such a combination is not expressly described.The invention is not limited by the description with reference to the exemplary embodiments. Rather, the invention features any novel feature and any combination of features, including in particular any combination of features from the claims, even if this feature or combination itself is not expressly stated in the claims or exemplary embodiments.Reference Character List1, 2, 3 Method step 10 Capacitor element 20, 20', 20" Sensor 30 Processing unit 100 Electrical system D, E Parameter CEI Capacitor element information

Claims

An electrical system (100) comprising at least one capacitor element (10), at least one sensor (20, 20', 20") configured to measure at least one parameter selected from device parameters (D) and environmental parameters (E), and a processing unit (30) configured to process the at least one parameter and evaluate capacitor element information (CEI) of the at least one capacitor element based on the at least one parameter, wherein the capacitor element information comprises one or more information selected from a capacitance loss, a tangent change, a load, a remaining lifetime and a fault condition.The electrical system of claim 1, wherein the electrical system includes a plurality of sensors configured to measure a plurality of parameters selected from device parameters and environmental parameters.The electrical system according to any of the preceding claims, wherein the at least one sensor comprises one or more sensors configured to measure an electrical operating state of the capacitor element and / or the electrical system.The electrical system of any preceding claim, wherein the at least one sensor comprises one or more sensors configured to measure at least one of a DC voltage, a DC current, a ripple voltage, and a temperature at a hot spot of the at least one capacitor element or a housing of the at least one capacitor element.The electrical system of claim 4, wherein the processing unit is configured to estimate a maximum temperature inside the housing of the at least one capacitor element based on the measured temperature of the housing.The electrical system of any preceding claim, wherein the at least one sensor comprises one or more sensors configured to measure an ambient humidity, an ambient temperature, vibrations, one or more types of gases.The electrical system of claim 6, wherein the one or more gas species is selected from a gas species that can be generated during a pyrolysis process of one or more components of the capacitor element.The electrical system of any preceding claim, wherein the capacitor element is a foil capacitor comprising a polymeric foil.The electrical system according to any of the preceding claims, wherein the processing unit comprises a microprocessor and / or a personal computer.The electrical system according to any one of the preceding claims, wherein during operation of the electrical system and / or the at least one capacitor element the at least one parameter is measured in real time and the capacitor element information is evaluated in real time.The electrical system according to any of the preceding claims, wherein based on the capacitor element information, information is provided to an operator of the electrical system.

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