Method, computer program and measurement system for calculating at least one thermal characteristic quantity

Abstract

The present invention relates to a method for calculating at least one thermal characteristic of an electrical system based on an evaluation of the resonance points of the electrical system, and further to a computer program for carrying out such a method, and to a measurement system comprising at least one control unit designed to carry out the method.

Description

[Technical Field]

[0001] The present invention relates to a method for calculating at least one thermal characteristic of an electrical system based on an evaluation of the resonance points of the electrical system, and further to a computer program for carrying out such a method, and to a measurement system comprising at least one control unit designed to carry out the method. [Background technology]

[0002] One such thermal characteristic of an electrical system is, inter alia, the temperature at one or more points in the electrical system, and it is known to use temperature sensors to determine such temperatures by measurement techniques.

[0003] The fundamental technical problem is the high temperatures in electrical systems, due inter alia to current-heat losses and external influences, where exceeding material- or system-specific temperature limits can lead to transformation and degradation effects, which can alter the mechanical and electrical system properties in ways that are usually undesirable.

[0004] Currently, especially in distributed systems, it is often not practical to determine and monitor temperature limits during operation using temperature sensors, since the implementation of distributed temperature sensors and the associated costs are economically and logistically unacceptable. Instead, with special exceptions, a conservatively calculated limit value for the operating current is used as an abstract auxiliary quantity, particularly to prevent system degradation. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, the object of the present invention is to calculate at least one thermal characteristic quantity at reduced cost in any electrical system, including even very large electrical systems, in particular overhead energy supply lines, overhead lines and other energy transmission cables. [Means for solving the problem]

[0006] This object is achieved by a method for calculating at least one thermal characteristic quantity of an electrical system based on an evaluation of the resonance points of the electrical system as set forth in claim 1. An electrical system comprises one or more of the following components: an arrangement of electrical energy transmission lines, stationary electrical machines such as transformers, electrochemical energy converters, electrical energy storage devices, inverters, protection techniques such as fuses.

[0007] This method is a) applying a system excitation, such as an excitation AC signal or pulse pattern, to an electrical system, the system excitation including one or more pre-calculated excitation frequencies, the excitation frequencies suitable for exciting the electrical system at one or more pre-calculated resonance points of the electrical system; b) measuring at least the input and output currents of the electrical system and / or other electrical characteristic quantities from which the frequency and time dependent impedance of the electrical system can be determined; c) determining a result quantity by evaluating the electrical characteristic quantities measured in step b) by one or more analytical transformation methods at one or more pre-calculated resonance points of the electrical system; d) determining at least one thermal characteristic quantity of the electrical energy transmission line arrangement, the fixed electrical machine, the electrochemical energy converter, the electrical energy storage device, the inverter, and / or the protection technology of the electrical system by relating the resulting quantity calculated in step c) to predetermined characteristic nominal values ​​for the electrical system in defined nominal conditions. Includes:

[0008] Thermal effects on the resonance of an electrical system affect various characteristic quantities, including the input and output current transfer function and the system impedance. The selection of the appropriate system excitation criteria depends on the application and influences the required measurement technology, required accessibility, and possibly predetermined system characteristics.

[0009] The method according to the invention is therefore characterized by the appropriate use of a characteristic feature of the electrical system at its resonant frequencies, i.e., the resonances caused by the electrical load on the system. For this purpose, typical resonance points of the system are first determined, and then, in a subsequent measurement operation, excitation is carried out with an electrical signal at at least one or more resonance points, and the change in amplitude of the resonance points is evaluated.

[0010] The present invention therefore solves the above mentioned technical problems and all the further technical problems described below, by the fundamental realization that the transmission behavior of an electrical system depends on the operating temperature, and that this dependence is significant and measurable at the high frequency resonance points of the system.

[0011]

number

[0012] The application of system excitation to the electrical system can be achieved by injecting an additional AC signal, applying a randomly pulsed load profile, and / or by an AC signal already injected into the electrical system (see FIG. 7). The measurement of the input and output currents can be performed using commercially available current sensors. The determination of the at least one thermal parameter in step d) can be performed with sufficient accuracy to assess the thermal load on the electrical system. Many applications do not require high measurement accuracy, as would be possible with a temperature sensor. Therefore, the method according to the present invention can be performed without a temperature sensor at all. For example, it is also possible to utilize a temperature sensor already present in the electrical system, i.e., its signal can be used to support and / or validate the determination of the at least one thermal parameter in step d).

[0013] The characteristic nominal value of the electrical system can be determined, for example, at a defined nominal condition where the electrical system is not under load and a certain ambient temperature is present, or at least when there is no particularly high load on the system.

[0014] For example, the frequency- and time-dependent impedance of the electrical system can be determined as a result quantity in step c), and in step d) this result quantity can be related to the nominal impedance of the electrical system in nominal conditions, for example by forming a quotient, from which the thermal characteristic quantity can then be derived, for example analytically, based on a predetermined and defined thermal characteristic curve of the electrical system, or based on a predetermined table.

[0015] According to an advantageous embodiment of the invention, steps a) to d) of claim 1 are repeated at regular or irregular time intervals, thereby enabling permanent thermal monitoring of the electrical system to be carried out.

[0016] According to an advantageous embodiment of the invention, the time interval is shortened when the determined thermal characteristic approaches a predetermined limit value. In this way, monitoring can be intensified when it is foreseeable that the electrical system is approaching a critical state. If the thermal characteristic is sufficiently far from the predetermined limit value, the time interval can be extended to such an extent that possible disturbances are minimized by the excitation AC signal.

[0017] According to an advantageous embodiment of the invention, the repetition rate of steps a) to d) of claim 1 is determined based on the following criteria: i) Changes in the grid impedance of the electrical system at the grid connection point; ii) the validity of the results; iii) The degree of agreement between the resulting quantities and the thermal model of the electrical system It is contemplated that the term "internal saturation" will be defined according to one or more of:

[0018] This also makes it possible to optimally adapt the intensity of the thermal monitoring of the electrical system to the operating conditions present in each case. According to an advantageous embodiment of the present invention, when the determined thermal characteristic reaches or exceeds a predetermined limit value, at least one electrical load applied to the electrical system is automatically reduced. This automatically prevents overloading of the electrical system and thus prevents damage to the electrical system due to overload. Depending on the state of the electrical system, the electrical load may even be completely switched off.

[0019] According to an advantageous embodiment of the invention, in a defined nominal state of the electrical system: a) calculating a resonance point of the electrical system; b) calculating excitation frequencies for exciting the electrical system at one or more resonance points; It is contemplated that the following is performed in advance.

[0020] Therefore, these steps do not need to be performed again during subsequent continuous thermal monitoring in accordance with steps a) to d) of claim 1, but are performed only once in advance, or possibly again upon a specific event.

[0021] According to an advantageous embodiment of the present invention, it is contemplated that additional external resonances are generated and used to calculate the thermal state of the electrical system. In this way, the method according to the present invention can be advantageously carried out even in electrical systems that have no or very few significant resonances, or where these resonances are located at inappropriate frequencies. Such additional external resonances can be generated, for example, by connecting additional electrical components to the electrical system.

[0022] According to an advantageous embodiment of the invention, the electrical system comprises at least one grounded energy transmission line, and the shield current of at least one grounded energy transmission line is measured and evaluated to determine at least one thermal characteristic quantity. In this way, the method according to the invention can be used to determine additional parameters, particularly in electrical systems in the form of shielded cables. It is advantageous here to measure and include in the evaluation the shield currents at all ground points of the energy transmission line as additional measurements.

[0023] According to an advantageous embodiment of the invention, the electrical system is configured as an arrangement of electrical energy transmission lines, and can in particular be configured as an arrangement of overhead energy transmission lines. The method according to the invention allows such an electrical system, which has a relatively large spatial extent, to be monitored with respect to its thermal load in a particularly simple, efficient and cost-effective manner.

[0024] Furthermore, the object stated at the beginning is also achieved by a computer program comprising program code means designed to carry out the method as described above when the computer program is run on a computer. For example, the computer program can be run on a computer of a control unit of a measurement system as described below. This also makes it possible to realize the advantages mentioned above.

[0025] The object stated at the outset is also achieved by a measurement system comprising at least one control unit and current sensors connected to the control unit, the current sensors being designed for detecting input and output currents of an electrical system under test, the control unit being designed to execute the method as described above, the control unit may for example comprise a computer, by which the method is executed as a computer program, and the advantages described above can also be achieved.

[0026] The invention will now be explained in more detail on the basis of exemplary embodiments and with the aid of the drawings. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a generalized diagram showing an electrical system as a two-port or pseudo two-port. [Figure 2] FIG. 1 is a diagram illustrating two ports as a distributed parameter model. [Figure 3] FIG. 1 illustrates a two-port as a partially distributed parameter model. [Figure 4] FIG. 1 shows an arrangement for generating an artificial resonance point. [Figure 5] FIG. 1 illustrates the integration of electrical systems into various facilities and grid structures. [Figure 6] 1 is a flow chart of a method according to the present invention; [Figure 7] 1 shows an excitation system for generating system excitation, inter alia, by means of an excitation AC signal; [Figure 8] FIG. 10 is a diagram showing a simulation result of a transmission ratio. [Figure 9] FIG. 10 is a diagram showing the temperature dependence of the transmission ratio at different frequencies. [Figure 10] FIG. 1 shows a measurement setup for thermal evaluation of an electrical system. [Figure 11] FIG. 1 illustrates the interaction of control units for thermal evaluation of an electrical system. [Figure 12] FIG. 10 is a qualitative illustration of the selection process for excitation frequencies. [Figure 13] FIG. 10 illustrates criteria for readjustment based on transmission coefficients. [Figure 14] FIG. 1 shows a measurement setup for thermal evaluation of an electric energy transmission system taking into account shield currents. [Figure 15] FIG. 10 shows the transmission characteristics in non-uniform heating. [Figure 16] FIG. 10 is a diagram showing the transition of the system impedance of the electrical system at 10°C. [Figure 17] FIG. 17 shows the evolution of the system impedance of the system according to FIG. 16 at 80° C. [Figure 18] FIG. 18 is a diagram showing the difference in system impedance calculated by generating the difference between the transitions in FIGS. 16 and 17. DETAILED DESCRIPTION OF THE INVENTION

[0028] Definition of the concept "electrical system" This method is generally applicable to electrical systems. Electrical systems are described as two-port or pseudo-two-port RLC elements in a distributed parameter model (see Figures 1 and 2). Modeling electrical systems and entire system structures as RLC elements over a wide frequency spectrum is common practice [1-3]. Various systems are parameterized differently, as appropriate. Systems with multiple (sub)components, distributed systems, and systems with different thermal model sections can be represented by dividing the distributed parameter model into sections with identical characteristics (see Figure 3). The descriptive system characteristics are selected using the system impedance or impedance equivalent, but can be replaced by any acceptable model. Modeling is performed in sufficient detail for each application. System-specific influencing factors can be taken into account here. Given the differences in model implementation, the technical issues are explained below using the example of an electrical energy transmission line. This method is transferable to all other electrical systems by adapting the two-port RLC characteristics.

[0029] The method is suitable for single-phase, symmetrical multi-phase, and multi-phase DC and AC systems with asynchronous loads. A sensor is required for each individual phase during implementation. Current and / or voltage harmonics can be evaluated in both DC and AC systems. Possible phase coupling effects must be taken into account in distributed parameter models, e.g., by mutual inductance. In multi-phase systems, phases can be evaluated individually for each application, e.g., to determine the thermal state of the most heavily loaded phase, or converted into a single-phase equivalent circuit in the case of symmetrical loads or a model of symmetrical components in the case of asymmetrical loads, e.g., for system identification. Existing and artificial resonance points The present invention focuses on the resonance points of electrical systems, since in these frequency ranges temperature-dependent resistance components have a significant effect and thus differences in operating temperature become apparent. However, particularly physically small systems and systems with special output filters may not have resonance points, or may have only weak resonance points, or resonance points located at very high frequencies. To make the present invention applicable, for example, parallel or series systems with predefined impedance responses can be connected to the electrical system under test (DUT - device under test) during measurements, thereby creating artificial resonance points in a usable and assessable frequency band. System Modeling An exemplary selection and classification of electrical systems to which the present invention can be advantageously applied is shown in Table 1. A distinction is made here between systems that have inherently two-port characteristics, such as energy transmission lines, and systems whose transmission behavior can also be described as one-port. The distinction is important, especially with regard to the solution algorithm and the choice of measurement points. Evidence and Examples of the Importance and Current Need for the Invention Knowledge of the actual operating temperature has many advantages. Applications include, among others, the expansion of the transmission capacity of electrical lines, "active health monitoring", "predictive health monitoring" (aging phenomena), and the enhancement of safety systems [4].

[0030] There is a great demand for concrete solutions for economical, non-invasive, and operationally employable methods that can identify system states and therefore prevent system anomalies. There is currently a public call for proposals for implementations and applications of such methods on cable routes, with rewards of up to 750,000 euros available for practical solutions [5].

[0031] The current importance of this issue is particularly evident against the backdrop of changing demand and load structures in public distribution networks. These changing structures have proven to be even more likely to contribute to cable overheating and ageing effects [6].

[0032] Moreover, current research also addresses the specific impact of the overheating effect [7, 8], which further highlights the urgent need for preventative solutions. In recent years, the expansion of the power grid in Germany has been mainly characterized by an increase in transmission capacity due to the expansion of cable cross sections and the laying of parallel lines. Furthermore, existing overhead line routes have been converted to underground cables due to political / social factors. The presented invention allows for a reduction in the demand for new expansions due to an optimized utilization of cable routes. Here, in some situations, existing measurement techniques can also be used, which have likewise been significantly expanded [9]. Rationale and special benefits for exemplary system categories The application of the presented invention is beneficial to all electrical systems, especially those listed in Table 1.

[0033] [Table 1] Permissible connections for electrical systems The system under test can be tested individually on a test bench, in a microgrid, or in parallel with the grid (see Figure 5). For the implementation of the method, it is advantageous to isolate the system behavior and calculate the microgrid or grid characteristics sufficiently regularly in advance and analytically separate them from the system evaluation. This can be done, for example, by pre-measuring the decoupled grid connection points.

[0034] FIG. 5 shows an exemplary circuit arrangement for thermal monitoring of an electrical system 1. A current sensor 21 is connected to the input side of the electrical system 1, and a current sensor 22 is connected to the output side. The current sensor 21 detects the input current of the electrical system 1, and the current sensor 22 detects the output current. To generate electrical excitation of the electrical system 1 at one or more resonance points, an excitation control function 23 is provided. The excitation control function 23 can connect the input of the electrical system 1 to one or more excitation sources 51, 52, 53, such as a current source 51, a voltage source 52, or a power grid, such as a microgrid 53. Furthermore, the electrical system 1 can be connected to a power grid or a facility 3 on the output side. Depending on the characteristics to be received, an impedance measuring device can be appropriately integrated. The measurement system 2 thus formed is controlled by a control unit 20. The control unit 20 further evaluates the sensor signals of the sensors 21, 22, thereby determining the thermal characteristics of the electrical system 1.

[0035] A further switchable impedance 12 can be connected to the input of the electrical system 1. A further switchable impedance 11 can be connected to the output of the electrical system 1. The switchable impedances 11, 12 allow for the creation of additional resonance points.

[0036] The present invention is suitable for solving many technical problems. a. How can you determine the operating temperature without using a temperature sensor? b. How should the control and control units be configured to ensure signal processing, data processing, communication, evaluation, and system control? c.How can location and system specific frequency limits be calculated to select the appropriate and optimum excitation frequency? d. How can an electrical system be excited so that large, measurable current or voltage harmonics are superimposed on the calculated excitation frequency at the system's resonance? e. For electrical systems, how can reference characteristics for temperature-dependent transmission behavior be described location-specifically and generally, within normal ranges and at critical temperatures? f. How much power can the system be excited with, or what amplitude must the superimposed current or voltage harmonics have? g. How can you identify an appropriate repetition rate for performing system adjustments and measurements? h. How can adequate additional resonances be generated in a system that has insufficient resonances? i. How can shield current be used as an additional source of information in energy transmission cables? j.How can this method be employed in a system for temperature monitoring using resonance point evaluation with or without a temperature sensor? k.How can we develop and observe aging characteristics for the transfer function of a particular system? l. How can disability characteristics be developed and observed that can serve as a basis for disability assessment and "active health monitoring"? m.How can this method be used to identify electrical systems and system structures? n.How can the operating point or load of an electrical system be evaluated by this method? o. How can the ambient temperature of a cable be calculated and monitored without an additional temperature sensor? p.How can the energy transmission capacity of overhead lines and cables be increased? Exemplary Technical Solutions Problem a. Method steps The introduction of current sensors is simpler due to their positioning at the beginning and end of the system, as opposed to the distribution of temperature sensors along the system. The present invention allows for the replacement of temperature sensors by current sensors without substantial loss of information.

[0037] A procedure for this can be presented based on Figure 6, which allows the relationship between operating current and operating temperature to be established by resonance evaluation. The flow chart in Figure 6 illustrates this method.

[0038] After start 60, the process begins with initial system tuning 61, which identifies and stores in the control / database system the characteristics of selected system parameters and grid-connection points. This includes, among other things, determining nonlinearities, frequency bands that may be excluded due to secondary uses such as "power line communication," and special characteristics of the protection technology used. Initial tuning may include, for example, checking whether the method according to the invention can be usefully implemented in the electrical system, or whether additional resonance points are necessary in some cases.

[0039] The operational method begins with system adjustment in block 62 regarding the excitation and measurement sensor configuration. First, in step 62, the system's resonance points or grid connection points (in the case of distributed systems) must be identified so that temperature-induced differences in transmission behavior can be clearly measured. For this purpose, the system usually must be additionally excited. This can be done, among other things, by one or more excitation systems according to FIG. 7.

[0040] In block 64, the frequency conditions of the electrical system may be checked to ensure, for example, that necessary boundary conditions are observed and that electrical signals present, for example in power line communications, are not disturbed. Subsequently, in block 63, it is determined which excitation frequencies are useful and appropriate for carrying out the method.

[0041] In the subsequent "Excitation" section, an excitation signal is applied to the electrical system in block 65, for example by superimposing an excitation current onto the input of the electrical system. In the "Evaluation" section, measurements of the input and output currents of the electrical system are carried out in block 66. In the following block 67, a calculation of the transmission behavior is carried out, i.e., the resulting quantities are determined from the previously measured quantities. For example, an analytical transformation of the measured data can be carried out.

[0042] In block 69, a system-dependent limit value for the transmission behavior is specified. In block 68, this limit value is compared with the transmission behavior determined in block 67, for example, the calculated thermal characteristic quantity.

[0043] Finally, in block 70, an estimation of the thermal state of the electrical system is performed. The method may be repeated periodically, for which an iteration criterion is determined in blocks 71 and 72. For example, an adaptive change of the termination resistors of the electrical system may be performed in block 71. A repetition rate for the execution of the method may be defined in block 72 depending on the operating temperature of the electrical system.

[0044] When calculating the optimum excitation frequency, the actual system spectrum and the initial execution command are taken into account, as well as system-specific preset parameters from the control and control unit. These parameters include, among others, the allowable upper and lower frequency limits, which are summarized below in a separate technical issue.

[0045] For example, Figure 8 shows the frequency-dependent transmission behavior I of a typical medium-voltage cable with a length of 8 km and a grid termination resistance of 50 ohms at a temperature of 20°C (time course V1) and a temperature of 90°C (time course V2). 出力 / I 入力 It can be seen that the operating temperature affects the transmission behavior to different degrees depending on the frequency. The specific effect depends not only on the frequency but also on the cable length, cable type, installation method, the characteristics of the grid connection point, and possibly on the filters and operating means present. In this case, the difference varies between 0 and 6 percent, but other grid types can produce differences of 0 to more than 20 percent.

[0046] It is clear that the superposition of current harmonics at the beginning of the line should have a frequency close to the system's resonance point so that clear differences in transmission behavior can be identified. The temperature change example in Figure 9 further demonstrates that for evaluation, it is necessary to find the resonance point and detect the transmission behavior at this point. While the transmission behavior at any frequency changes by only about 1% (time course V3), the current ratio has a relative change of more than 6 percent at the resonance point, here the first resonance point at about 10 kHz (time course V4). Furthermore, the signal-to-noise ratio increases, which, combined with a larger change in signal amplitude, allows for a more accurate estimation of the operating temperature and reduces the requirements for the current sensor.

[0047] After the optimal frequency band is found and excited, the input and output currents of the DUT can be measured in a time-synchronous manner, and the transmission behavior can be calculated taking into account the grid connection parameters. For example, a "handshake" method can be used for synchronization

[41] . The measured currents must then be analyzed and interpreted using appropriate methods. For example, Fourier analysis, wavelets, self-learning methods, or multiparameter analysis can be used to evaluate the results and compare them with predefined or dynamically calculated limit values. Setting limit values ​​is not part of this problem and will be discussed elsewhere. This comparison allows the thermal state of the DUT to be inferred.

[0048] Figure 10 shows a schematic measurement setup for the thermal evaluation of an electrical system. The setup according to Figure 10 corresponds roughly to the setup according to Figure 5, where the control unit 2 is shown in more detail together with the component controls 20a and the database 20b.

[0049] Since the operating temperature is not a static quantity in nature but varies depending on the load and environment, the system should repeat the presented procedure. Similarly, the electrical characteristics of the grid-connection point may also change, for example due to a new grid topology, and thus affect the resonance point. The repetition rate is part of a further check point.

[0050] Multiphase systems are application-specific and must be evaluated in different ways. For example, if maximum loads or faults are to be checked, the phases must be considered individually, since asynchronous loads can, for example, cause phase-specific overloads on individual operating means

[42] . However, if the aim is to identify characteristic features, it is useful to carry out an evaluation of symmetric component models

[43] . Problem b. Control unit The control unit is an essential part of the construction and implementation of the method according to claim 1. The control unit is the hardware core and is connected to current sensors at the inputs and outputs, possibly a current sensor at the ground point, an excitation system, possibly a system and a database for power grid analysis.

[0051] The specific implementation depends on the system. However, at a minimum, the information flow must be handled as shown in Figure 6, the excitation system and the grid evaluation system must be connected, and the necessary calculations and comparisons must be performed. After internal selection, the control unit specifies the system excitation parameters, such as amplitude and frequency, and initiates system excitation. The control unit then recognizes unacceptable excitation ranges and selects optimal parameters. The control unit receives measurement data, interprets it, and compares it with system-specific reference data. Further measurement and system adjustments are repeated depending on the situation. A system time is also defined here to synchronize all measured quantities, data streams, and execution instructions. This is specified for all system components, especially distributed components.

[0052] 11 shows the integration of a control unit into the overall configuration, which is particularly advantageous for measuring purely electrical parameters and deriving thermal quantities resulting therefrom. Problem c. Frequency selection In order to evaluate a frequency range for its suitability, the target network connection point (NVP) should have the following characteristics for this frequency:

[0053] i. It should be, to a good approximation, linear and time-invariant over as long as possible, but at least the duration of one measurement cycle. ii. The harmonic loads present should be low compared to the amplitude of the planned superposition in the excitation domain. However, they should be constant and measurable, at least in the sense of an LTI system. Particular attention should be paid to the resonance points of (active) filters.

[0054] iii. The superimposed harmonics are usually attenuated up to the line termination, where the signal amplitude is much larger and therefore must be measurable. iv. The excitation frequency should exceed the regulatory limits for harmonics, i.e., be greater than 2000 Hz or 9000 Hz, but at least must not exceed the THD and further limits at the grid connection point.

[0055] v. If a device for "power line communication" is present, the excitation frequency should be lower than the lowest communication band, but at least superposition should be detected and passed to the interface.

[0056] A graphical representation of the exclusion criteria for suitable and optimal excitation frequencies can be seen in Figure 12. Here, three suitable resonance points R1, R2, R3 can be found. Here, the present harmonic load at the NVP is first measured. The system is then periodically excited over a defined period to identify time-varying frequencies. In particular, RPWM wideband excitation is suitable in this regard due to the short load duration. Furthermore, a "frequency sweep" allows individual frequencies to be excited and evaluated over multiple fundamental periods, thereby identifying the presence of significant nonlinear or time-varying characteristics in the grid. If the results differ, a different excitation frequency must be selected.

[0057] Furthermore, to select the optimum frequency, it is possible to determine the frequency that is most susceptible to temperature variation, i.e., to perform an optimization of equation V. If this is not possible, selecting a static maximum value α is a good approximation. The frequency with the greatest temperature-dependent difference in transmission behavior should be selected.

[0058] Regarding the selection of the resonance point, for example, the following procedure can be carried out. The resonance point of the system is at frequency f 共振,i It has. F is the set of all resonant frequencies that occur in the system, where |F|≧1.

[0059] All f 共振 For ∈F, Δ|Z|(f 共振 ,T1,T2):=|Z|(f 共振 ,T1)-|Z|(f 共振 ,T2) is maximal for any T1 and T2.

[0060] For every element of F, the optimal frequency range can be derived. 共振 For each ∈F, there is one optimal frequency range F 最適,i is defined as follows: F 最適,i =[f 共振 -δf;f 共振 +δf],δf=δf(|Z|,f 共振 ,ε,r) where ε̂ = absolute measurement deviation, r̂ = shape factor of the excitation method, and i = |F|. Problem d. Excitation method The excitation of current harmonics or their superposition with the excitation frequency can be achieved in various ways. In particular, it is suitable to use existing operating means, such as a controllable multi-stage inverter, or to use certain existing harmonics. Figure 7 shows possible excitation systems and a selection of excitation signals.

[0061] FIG. 7 provides an overview of advantageous excitation systems and the excitation signals they can generate. For example, an excitation system for exciting an electrical system at one or more resonance points can include a current or voltage source A. A further possible excitation system can be a controllable DC / AC converter B. A further possible excitation system C can be a switchable impedance Z. A further possible excitation system D can be a switchable storage element, such as a capacitor. A further possibility is to realize system excitation by utilizing rapidly changing system states. As an example, an excitation system with a transformer E is shown.

[0062] In addition to converting DC to AC using PWM, inverters can also superimpose additional signals. In this case, the output signal is characterized by the excitation of frequency bands whose amplitudes correspond to a Gaussian distribution. Alternatively, parallel-connected current sources can be used. This is particularly useful when precise excitation of individual frequencies or narrow frequency bands is required. A further alternative is the high-frequency clocked load connection (see EP 2 385 381). This allows entire frequency bands or groups of frequency bands to be excited with different pulse patterns. As long as the load resistance is set correctly and the circuit breaker is suitable for the excitation frequency, the desired harmonic load can be achieved. Question e. Reference property To determine the effect of temperature dependence on specific frequency ranges of transmission behavior, theoretical models can be developed for the respective electrical system or line-specific measurements can be performed.

[0063] For example, measurements for a typical system can be performed in advance using a variable load resistor and possibly unit length. A temperature sensor must then be used to detect the operating temperature. The system must then be evaluated for each temperature point at each termination resistor to create a frequency-dependent transmission characteristic. However, this process only needs to be performed once per system type.

[0064] Given information about system parameters, laying or installation methods, theoretical models can more quickly describe the corresponding characteristics. This can be achieved using general line models, such as distributed parameter models. It is advantageous to take frequency-dependent effects, such as the "skin or proximity effect," into account.

[0065] Depending on the system, known standardized methods can be used to perform the measurements and record the transmission characteristics

[44] . Problem f. Excitation power In order to be able to calculate the transmission characteristics of the electrical system under test, the output current must be measured, among other things. Since the attenuation characteristics of the system depend on frequency, the characteristics determined according to Example 5 can be used in the frequency range determined according to Example 3. These attenuations, and the accuracy of the current sensor, therefore determine the excitation power at the system input. If the shield current according to Example 10 is also taken into account, then inductive coupling and shield impedance can also be taken into account as reduction factors. The following formula holds:

[0066] I 出力 min(|I 入力 |)>ζ(f 励起 Sensor Accuracy at VI The excitation power is distributed over the entire spectrum to be excited depending on the method, it is the amplitude of the specific evaluation range that is important.

[0067] Therefore, the required excitation power must be evaluated taking into account the system attenuation of the harmonics to be excited and the excitation method. Approximations regarding power ranges can be made as a preliminary design during device selection and initial system tuning, but the specific signal amplitudes must be calculated dynamically during the execution of the method. Problem g. Adjustment repetition rate Permanent measurement guarantees the fastest response time to both changes in the power grid and in the operating temperature, but this is not always beneficial: permanent operation leads to permanent losses depending on the excitation method, and harmonic loads can be newly evaluated as permanent phenomena.

[0068] The appropriate iteration rate for system adjustment is Z NVP , i.e. it depends on the rate of change of the grid topology. The more frequent and larger the changes, the more frequently the measurement system must be recalibrated. Here, both empirical and predicted deviations in NVP are taken into account. That is, if the transmission behavior changes so that it is no longer possible to assign points to a temperature-dependent function, a recalibration must be performed (see Figure 13).

[0069] The rate of change of the transmission behavior must also correspond to a reasonable thermal derivation. If this exceeds a limit, a readjustment must be made to eliminate physical line disturbances.

[0070]

number

[0071]

number

[0072] According to Figure 4, the electrical system 1 to be tested is connected to an additional impedance 4 to create an artificial resonance point, to which a measurement system 2 is then connected, to which a power grid or installation 3 can be further connected. Problem i. Shield current The shield current and its variations can be additional parameters for the evaluation of cables, for which the configuration according to Figure 14 can be used as a basis.

[0073] The configuration according to Fig. 14 corresponds in principle to the configuration according to Fig. 5 and is based on a grounded electrical energy transmission line as electrical system 1, which is configured as a shield line, and shield currents are measured at all ground points by further current sensors 24, 25. The shield currents are included in the evaluation, i.e. the control unit 2 detects these shield currents and takes them into account in the evaluation and subsequent control of the loads of the electrical system 1.

[0074] In principle, the method described in claim 1 is used, with the difference that the shield current must be measured at all grounding points to determine the shield's transmission characteristics. Furthermore, additional adjustment logic must be taken into account. The shield current is substantially affected by inductive coupling with the conductor current and by thermally induced impedance changes in the shield. A change in the conductor current directly changes the shield current. As the conductor temperature increases, the conductor's transmission behavior changes, and thus the shield current also changes directly. Furthermore, a thermally induced change in the shield's transmission behavior causes a second, delayed change in the shield current. This time delay is an indicator of the shield's heating and is highlighted as a new characteristic feature. This allows, among other things, inferences to be made about the ambient temperature or the detection of material defects in the shield.

[0075] The method can proceed as follows:

[0076] [Table 2] Problem j. Temperature monitoring By means of the method according to claim 1, overheat protection or temperature monitoring for electrical systems can be implemented.

[0077] In this regard, system-specific limits on transmission behavior are specified in advance and, if necessary, periodically inspected. After analytically isolating the system characteristics, the transmission characteristics can be used to estimate the operating temperature. Transmission characteristics can be used not only to determine homogeneous heating but also to identify inhomogeneous "hot spots." Figure 15 shows the transmission characteristics of an 8-km-long energy transmission line at 20°C. The transmission characteristics vary depending on the heating location at the beginning, end, and middle of the cable. Furthermore, they are clearly distinct from homogeneous heating. If inhomogeneous heating is detected, the signal amplitude must be sufficiently high for this secondary evaluation. Because this method does not require a temperature sensor, it is particularly suitable when monitoring is useful or necessary but retrofitting would be too complex or uneconomical.

[0078] In systems with existing temperature monitoring capabilities, this method provides additional control parameters that are independent of temperature sensors, thus improving fault safety and, in some cases, accuracy. For systems with special requirements for fault safety, such as electrical systems on aircraft or nuclear power plants, it is useful to develop individual, system-specific models for these systems. For example, extending the underlying distributed parameter model with temperature information for each line section allows for highly accurate transmission characteristics to be established. Depending on the line section and frequency range, heating in different sections can affect the transmission characteristics differently. Furthermore, when the method according to Example 19 is applied, this location criterion can be correlated with the aforementioned overheat protection method, thereby further improving fault location accuracy. Problem k. Aging characteristics The characteristics of electrical systems change due to aging and extreme operating conditions, such as transient voltages, exceeding the permissible current strength, or extremely low or high ambient temperatures. This increases the frequency of system faults and breakdowns. To identify aging-related changes in transmission characteristics, it is particularly suitable to perform measurements on the system in an unloaded state. Therefore, NVPs have no effect, and the measurement complexity relative to the reference is reduced by one dimension. Alternatively, heuristic approaches can be used to identify transmission characteristics in specific load scenarios and under well-defined conditions, and their changes can be used to infer system aging. If changes in transmission characteristics are assumed to be due to aging rather than system failure, then changes in components, particularly those susceptible to oxidation, physical stress, and possibly other reactive factors, will occur, which will in turn alter system parameters, such as capacitance equivalents. Consequently, transmission behavior will also be affected.

[0079] The newly recorded no-load characteristics allow analytical calculation of the grid-connection point characteristics, for example by applying ABCD transmission parameters. This allows the new transmission behavior to be evaluated during operation without the influence of NVP, when the grid characteristics remain constant. It is known that temperature has a substantial effect on line aging

[45] . Statistical investigation of this method allows the results to be quantified.

[0080] To measure and verify degradation due to aging, the effects that cause aging must be defined and measured. This includes, among other things, critical temperatures, temperature gradients, harmonic loads, high currents, high current gradients, and overvoltages without breakdown or partial discharge. Furthermore, constant measurements can also compile reference data and simultaneous descriptions of operating points. By evaluating various data sets, statistical relationships can be calculated between the aging-induced state in the form of transmission behavior and its changes due to operation and time. The selection of relevant data points and the evaluation itself can be optimized using self-learning methods. Problem l. Disability characteristics Based on the relationship between the spectral operating current transmission behavior and operating temperature identified here, a quality criterion for a healthy system can be developed. This criterion is expressed as the complex spectral function α(f,Zw,ケーブルタイプ,ケーブル長) This depends on the grid connection and system parameters.

[0081] The degree of damage can be determined based on deviations of the current transmission behavior within predefined framework conditions. This methodology allows the method presented here to be used as a "health monitor" for the system. Here, damage and fault events are characterized by the following relationship: If the absolute current is less than a predefined maximum current and, at the same time, the operational behavior indicates transmission behavior that suggests a current that is too high, a fault can be assumed.

[0082]

number

[49] The present invention is particularly well suited to identifying differences in resonance points, and the superposition of thermal effects improves the determination of the load or operating point. The electrical characteristics can be determined by a method augmented with a temperature sensor, as described in claim 1. The load or operating point correlates with the system's current-heat losses. When the system changes its operating point or load, instantaneous changes in the electrical characteristics occur, especially at resonance points, as well as delayed, thermally-induced changes. The superposition of this information leads to improved identification of the operating point, on the one hand, and the expected value of normal system heating, on the other hand. Intelligent self-learning methods can make predictions from this data and thus improve, for example, existing regulation systems or identification methods. Problem o. Ambient temperature To determine the ambient temperature without an additional temperature sensor, the method described in claim 1 can be extended by example 10 and possibly example 1. Once a constant condition is established, a thermal model with dominant steady-state variables can be formed. Steady-state conditions are characterized by the thermal energy caused by conductor currents and induction-induced shield currents being dissipated into the environment, while the currents following thermally varying transmission characteristics remain unchanged. If the conductor current remains constant but the transmission characteristics change, this may be due to faults, aging, or changes in ambient temperature. This distinction must be made based on an aggregated data model: faults cause rapid changes in the system's transmission behavior, aging causes constant and uniform changes in the system's transmission behavior, and ambient temperature changes cause predictable and modelable changes in the system's transmission behavior. The underlying thermal model can be optimized using initial data for soil conditions. Observation of various change processes may also identify changes in soil properties, such as drying and subsidence. Problem p. Transmission capacity The energy transmission capacity of a cable is represented by the maximum allowable current, which, based on a thermal model, ensures an allowable sustained load without causing thermal damage. Therefore, the maximum allowable current is inherently the limiting factor for energy transmission. The method of claim 1 is applied here to decouple the energy transmission capacity from the static and conservative maximum current and instead align the energy transmission with the decisive criteria of real operating parameters, in particular the operating temperature.

[0083] An advantageous application of temperature monitoring is to avoid dangerous system states and prevent the maximum permissible temperature from being exceeded. The permissible temperature of the energy transmission line will not be reached as long as the transmission behavior exceeds the limit values ​​of the evaluation criteria.

[0084] For this purpose, the transmission behavior of the system, which is line-specific, frequency-variable, and depends on the characteristics of the grid-connection point, is summarized as a max is generated.

[0085]

number

[0086] 16 to 18 show by way of example the application of the method according to the invention to an electrical line with measurement results. Two coaxial cables (500 m each, 1 mm conductor cross section, solid copper, 5 shielding, decoupled and grounded at both ends) were connected in series with a power source (Spitzenberger & Spiess). In parallel with this was connected a device for system excitation (ONIS 1000 morEnergy). The cables were wound and stored in a climatic chamber, where measurements were carried out at various ambient temperatures.

[0087] Figures 16-17 show the total system impedance of the cable and power supply versus frequency, respectively. Measurements were carried out specifically at 10 degrees and 80 degrees. Figure 18 shows the difference in the measurement results. Further exemplary embodiments The purpose of the method proposed here is to be able to describe the thermal state of an electrical system without using temperature sensors, based on predefined transmission characteristics and their temperature-dependent changes. For this purpose, the system is excited or a high-frequency signal is superimposed on it. The input current I at the system input is 入力 and the output current I at the system output 出力 Therefore, the system under test only needs to be accessible at the beginning and end. Here, the present invention measures the transmission behavior of a system with a selection characteristic α.

[0088]

number

[0089]

number

[0090] An example of a useful implementation may be as follows: In the event of a fault, cable routes laid underground suffer long downtimes due to the complexity of fault localization and, in some cases, the significant costs involved in physically reaching them. Urban areas, where cable routes are primarily used for electrical energy transmission, are particularly affected due to the multiple use of cable ducts and logistical challenges. Due to high investment costs, cable routes have proven to be used well beyond their estimated service life. Cable failures have negative consequences that depend on their location: for example, in urban areas, they can reduce the security of supply in the affected area or completely disrupt energy transmission in a PV park that is connected to the next grid connection point only via this supply line. Early recognition of a faulty cable allows preventive measures to be taken, thereby minimizing the impact of the failure.

[0091] The proposed "structural health monitoring" is based on the introduced transmission coefficient α max The transmission behavior of the system at the point of connection, which is linear and time-invariant, when supplied with power below the permitted nominal power is calculated using the complex transmission coefficient α(f,Z w ,When ,a ,system ,parameter ,(length ,of ,the ,measurement ,line ,in ,the ,DUT) ,is ,exceeded, ,the ,system ,can ,be ,considered ,to ,be ,faulty ,or ,to ,fail ,to ,occur.

[0092] In this context, the aging phenomena of the line can also be estimated. w In line analysis that does not take into account the above, the actual degradation can be estimated due to the special transmission characteristics. The cable routes of a photovoltaic power plant can sometimes be designed according to the average expected current flow, since compliance with the proposed standards allows the transmission of higher currents.

[0093] Rising outdoor temperatures due to climate change, especially in hot regions, can limit reliable and safe operation. In this case, the maximum allowable current is no longer an appropriate selection criterion, as the previous thermal model parameters are no longer valid indefinitely.

[0094] The safety factors currently selected in the cable product description can be reduced or eliminated through real-world monitoring, which increases the ampacity and reduces the required cable diameter.

[0095] The present invention can further include the following. I. Determining the temperature-dependent transmission behavior of electrical systems by resonance point evaluation a. The signal to be evaluated may be: i. Frequency-dependent current I 出力 / I 入力 transmission behavior, and / or ii. Frequency dependent grid impedance at NVP.

[0096] b. Excitation of the electrical system to identify resonance points can be achieved, among other things, by: i. Utilization of harmonics (passive) present, for example due to pulsating loads (e.g., arc furnaces) or fluctuating operating conditions, ii. Random broadband excitation; iii. Clocked broadband excitation; iv. "Frequency sweeping" by active injection of individual current harmonics, and / or v. "Frequency sweep" by active injection of harmonic frequency bands.

[0097] c. For operational superposition of current harmonics, the following can be used: i. Additional current sources in parallel with the grid; ii. A switchable variable high frequency load, and / or iii. Existing series-connected operating means, such as inverters.

[0098] iv. The above is done by using any of the following: 1. Current harmonics of individual frequencies, 2. Current harmonics with one frequency band; 3. Current harmonics with multiple frequencies, or 4. Current harmonics with multiple frequency bands.

[0099] d. Measurement of the current signal can be performed by: i. an additional current sensor; ii. Devices that implement and detect specific islanding detection methods, such as "active frequency shifting," and / or iii. Sensors already present in the protection and / or regulation technology.

[0100] e. The evaluation can be performed using one or more analytical transformation methods, such as: i. Fourier analysis, ii. Laplace transform, iii.Differential methods in interference-free systems; iv. Wavelet transform, v. Multiparameter analysis, and / or vi. Self-learning solution algorithm.

[0101] II. Configuration of the control and control unit for: a. signal processing, b. Data processing; c. Communication with external ports, excitation systems, sensors, electrical systems (DUTs), and remote databases; d. Evaluation of signals and information; and e. Excitation control.

[0102] III. Determination of location and system specific frequency limitations to select the best possible excitation frequency. IV. Methods for proper excitation to identify thermal differences at the resonance points of electrical systems.

[0103] V. Limit value α as a reference characteristic for the temperature-dependent transmission behavior of electrical systems max A method for calculating VI. Methods for determining the required and frequency-dependent excitation power.

[0104] VII. Calculating the appropriate repetition rate for performing system adjustments and measurements. IX. Methods for calculating and evaluating shield currents of energy transmission lines. X. A method for enabling or retrofitting a temperature monitoring system with or without an existing temperature sensor.

[0105] XI. Method for identifying the aging process of transmission lines, especially cables, based on resonance point evaluation. XII. Methods for "active health monitoring" of transmission lines based on resonance point evaluation.

[0106] XIII. Method for identifying an electrical system based on transmission characteristics at resonance. XIV. The load or operating point of an electrical system can be described by a thermally variable resonance point rating.

[0107] XV. Method for expanding the operating current capacity of a transmission line based on resonance point evaluation. a. In particular, with regard to site-specific permanent capacity increases based on a conservative design reality assessment of allowable operating currents; and b. In particular with regard to temporary increases in the permissible operating current (e.g. with regard to connecting lines of renewable energy plants with fluctuating power generation).

[0108] XVI. A method for assessing the change in earth surface temperature due to climate change in extremely hot regions based on the evaluation of the resonance point of transmission lines. XVII. The implementation of this method provides differential and overcurrent protection with the necessary current sensors at the beginning and end of the line. The condition of time synchronization is inherently provided by the present invention. Further advantages of the present invention: The relationship between operating temperature, current transmission behavior and limit values ​​can be calculated without temperature sensors, which would normally have to be installed along the line at great expense and equipped with a communication interface.

[0109] The current sensors required for the method are already present in many power grids due to the installed protection technology. By integrating appropriate interfaces, this information can be used. This further reduces the size of the measurement system.

[0110] This method introduces a previously unused parameter that can be used to assess the current operating state. By monitoring the transmission behavior and knowing α, it is possible to limit the time allowed for currents that exceed the inherent allowable current of the line without risking line degradation.

[0111] It provides new quality standards for "health monitoring" of transmission lines, which can minimize system failures and constraints. · New quality criteria for the aging process of transmission lines are provided.

[0112] In underground cable routes, statistical determinations can be made regarding changes in soil conditions. For example, changes in moisture content and the progression of siltation can be observed by changes in thermal contact resistance, which can be derived by periodic measurements.

[0113] I 出力 and I 入力 Current sensors for calculating the current can be retrofitted at the beginning and end of the line at little cost. However, this method is particularly suitable if active protection technology that records these parameters has already been installed. In this case, only an interface for data transmission is required.

[0114] This method can be used for temperature monitoring or overheat protection as long as the output lines of an electrical system pass through thermally critical locations. Especially in already installed / converted facilities, installing or retrofitting temperature sensors can be uneconomical or impossible, especially in large or distributed systems. The use of this invention makes temperature monitoring possible without this retrofitting.

[0115] The accuracy of existing temperature monitoring systems can be improved. Often, sensors are not attached directly to "hot spots" and only ambient temperatures are calculated. Furthermore, in systems without redundancy, there is always a high probability of failure. The method according to Example 16 makes the temperature monitoring system more fault-tolerant due to the additional indirect monitoring and more accurate due to the correlation of results.

[0116] Recognizing unknown electrical systems based on their electrical characteristics is particularly advantageous for the purposes of dynamic system control, load management, and synthesis

[81] . Previous methods for identifying electrical systems exist, but do not take thermal effects into account

[72] . The presented method superimposes thermal effects on transmission characteristics, improving identification with an additional dimension of information.

[0117] The ability to assess the load state and operating point of an electrical complex is particularly important in unknown user control structures, for example, to recognize consumer trends or estimate system wear and tear. For example, methods exist that can assess and map a building's load profile based on its electrical charging profile across a frequency range

[82] . Based on large amounts of data, unknown loads can be recognized and identified based on their harmonics

[83] . In contrast to known methods, the proposed invention takes thermal effects into account, eliminating previous inaccuracies due to thermally varying transmission characteristics and allowing existing methods and techniques to be improved or developed. Data sets that take thermal conditions into account allow AI methods to find solutions more quickly and accurately due to the increased amount of information.

[0118] Capacity limitations on energy transmission lines pose a major obstacle to the expansion of renewable energies and the achievement of politically set climate targets. Capacity expansion is achieved through extensions and reconstructions, particularly by increasing cross-sections, laying parallel lines, and increasing voltage levels. The present invention enables cost-effective and nearly non-invasive capacity expansion by utilizing real, temperature-dependent maximum currents. Thus, application-specific, conservatively used models that previously acted as constraints can be replaced by real-world tolerances.

[0119] Examples 11-19 describe specific uses for the presented invention. The method described in claim 1 and / or example 1 serves as the basis for these and further uses. Possible uses are derived from these intended uses, and specific examples are described below.

[0120] In the framework of power grid expansion, high costs are incurred and long planning and construction times delay further development. As an alternative to expanding the energy distribution grid, power grid operators and utilities can use the present invention to quickly and cost-effectively expand the required transmission capacity of overhead lines or cables.

[0121] Manufacturers of overhead lines or cables, especially high-temperature lines, can incorporate this invention into their products to enable them to carry even higher currents, thereby gaining a market advantage and, in some cases, offering smaller cross sections to suit specific requirement scenarios and therefore selling them at a lower price.

[0122] Lower grid connection or expansion costs can also lower the cost structure of wind and solar power plant operators or large industrial customers by reducing line diameters, reducing downtime or avoiding unnecessary expansions.

[0123] (Additional) temperature monitoring allows critical systems to be monitored more reliably and in some cases more accurately. In particular, safety systems in nuclear power plants, medical technology, and electrical systems on aircraft can benefit from redundant temperature monitoring and the resulting increased safety from failures.

[0124] When this method is used on cable routes, the measured data records and their relationship to ambient temperature provide climate researchers with a new data base for detecting long-term warming trends and implied changes in soil properties.

[0125] In particular, in electrical systems or power grids with existing sensors, for example with special protection technology, this method can be used with little hardware and installation cost and associated effort: suppliers of this protection technology can directly integrate this method to provide additional functionality at little cost.

[0126] Mobile and portable embodiments are possible as long as the necessary hardware, in particular the current sensor, control unit and excitation system, is portable and the system to be tested provides connection options for the current sensor and possibly the excitation system.

[0127] The method can be used to evaluate and monitor filters and protection technologies as well, or can be integrated into existing monitoring systems as a low-cost redundant monitor.

[0128] Furthermore, the present invention can also be used to inspect conductive structures such as railway tracks and building power distribution lines, where again, temperature and possibly aging or degradation can be inferred based on characteristic features of the measured electrical parameters at one or more pre-calculated resonance points of the electrical system. [Example]

[0129] (See Figure 6) 1. A method for calculating a thermal state of an electrical system based on a resonance point assessment, comprising: a. The resonance point of the system is calculated, b. The appropriate and optimal excitation frequency is calculated; c. An excitation current is superimposed on the beginning of the line, d. (Metrologically) the input and output currents and, if applicable, the input and output voltages are calculated; e. Current components and possibly voltage components are calculated and made interpretable by analytical transformation methods; f. The measurements are compared to system-specific limits; g. The thermal state is determined; h. The method can be used for single-phase and multi-phase DC and AC systems and system structures according to FIG. 5, with symmetrical and asymmetrical loads, individually, within a microgrid and in parallel with the grid; method. [Example]

[0130] (See Figure 11) A control and control unit arrangement for integration into an arrangement for calculating the thermal state of an electrical system based on a resonance point evaluation, comprising: a. The control and control unit detects the measured input and output currents, possibly input and output voltages, and parameters of the system; b. A general-purpose communication interface; c. Evaluate the measurement data; d. Use application-specific solution methods, such as wavelets, Fourier analysis, or self-learning algorithms for evaluation; e. Calculate the optimal excitation frequency according to Example 3 and start the excitation according to Example 6; f. Access internal databases containing, among other things, important reference parameters; g. Specify an appropriate repetition rate for recalibrating the measurement system and the optimal measurement interval; h. Identifying operating temperatures based on system-specific limits; Control and control unit configuration. [Example]

[0131] (See Figure 12) 1. A method for calculating an optimal resonance point for exciting an electrical system to calculate a thermal state based on a resonance point evaluation, comprising: a. During measurement system adjustment, the characteristics of the system under test are identified; b. The system under test is linear and time-invariant over at least one measurement cycle, as determined by initial system tuning; c. The harmonic loads present in the frequency band of the resonance point should be low compared to the amplitude of the planned superposition, with particular attention paid to the characteristics of the filter or system with filter characteristics; d. The excitation frequency is above the regulatory range for harmonics or does not exceed the permissible THD, and therefore the frequency is above 2000 Hz or 9000 Hz; e. No frequency bands required elsewhere, e.g., for "power line communications," are excited; method. [Example]

[0132] 1. An excitation system for integration into an arrangement for calculating the thermal state of an electrical system by resonance evaluation, comprising: a. An excitation system according to Figure 7 is used, b. The excitation power is specified and implemented by the system according to example 6; c. The maximum clock frequency corresponds to at least the required excitation frequency according to Example 3; system. [Example]

[0133] A method for calculating temperature-dependent transmission coefficients, in particular limit values ​​at critical temperatures, for calculating the thermal state of an electrical system by resonance evaluation, comprising: a. Transmission coefficients establish system-specific and possibly grid-connection-specific correlations between operating temperatures and measured system parameters; b. Critical limits describe the system behavior at the maximum allowable temperature; c. These limit values ​​and transmission factors are determined for each individual system or series by test bench and simulation, depending on various parameters, in particular on the parameters of any existing grid connection points; method [Example]

[0134] 1. A method for calculating an optimal signal amplitude of an excitation signal for calculating a thermal state of an electrical system by resonance evaluation, comprising: a. Sensor dependent, takes into account electrical system damping; b. the optimal measurement range of the current sensor according to Example 3 is taken into account; c. The excitation power of the excitation system according to Example 4 is taken into consideration method. [Example]

[0135] 1. A method for calculating an optimal repetition rate of system excitation for calculating a thermal state of an electrical system by resonance evaluation, comprising: a. The application ensures dynamic thermal system monitoring; b. System load is minimized by excitation; c. Reassessments are conducted frequently enough; d. The current thermal state of the system is taken into account; e. The current absolute system load, especially the input current, is taken into account; f. Conditions VII and VIII of Section g are taken into account; method. [Example]

[0136] 1. A method for calculating an optimal iteration rate of system tuning for calculating a thermal state of an electrical system by resonance point evaluation, comprising: a. The statistical variation of the grid impedance at the grid connection point is taken into account; b. The absolute values ​​of the transmission characteristics are validated (whether these absolute values ​​match the expected values ​​for the corresponding excitation frequencies); c. The change in transmission characteristics can be accommodated in a thermal model; method. [Example]

[0137] 1. A method and arrangement for generating additional off-system resonances for calculating the thermal state of an electrical system by resonance evaluation, comprising: a. an electrical system (DUT) is augmented with system components that create a resonant circuit with the impedance of the DUT; b. For example, the method described in EP 3010149 can be used; c. The frequency and amplitude of the additional resonance point are dynamically determined by the control unit; d. The impact on NVPs, in particular on existing filter and protection technologies, is taken into account; e. A temperature sensor is attached to the system extension for resonance point generation to contribute to dynamic frequency adaptation; Methods and configurations. [Example]

[0138] 1. A method for taking into account shield currents in the thermal evaluation of an energy transmission line in order to calculate the thermal state of an electrical system by resonance evaluation, comprising: a. Extension of the method according to claim 1 and / or embodiment 1 for a grounded energy transmission line, b. Additional current sensors are used at all grounding points, c. The shield current is determined by inductive coupling from the conductor current; d. The shield current transmission behavior also depends on the shield temperature. e. Electromagnetic coupling is instantaneous, while thermal coupling occurs with a delay inherent in the system; f. The time evolution of the shield current transmission behavior can be used as a new qualitative parameter for various applications; g. The method can be used for single-phase and multi-phase energy transmission lines in DC and AC systems according to FIG. 5, with symmetrical and asymmetrical loads, individually, within a microgrid and integrated with the power grid; method.

[0139] Below, examples are described in relation to methods for implementing the method and examples of its application, in which the method can be used for single-phase and multi-phase DC and AC systems and system structures according to Fig. 5, with symmetrical and asymmetrical loads, individually, in microgrids and in parallel with the grid. [Example]

[0140] 1. A method for integrating overheat protection and / or temperature monitoring into a system without a temperature sensor, comprising: a. This method is based on Example 1, b. The limit values ​​according to Example 5 apply; c. Data regarding the temperature-dependent properties of the system exist or can be determined in advance; d. The repeatability of the measurements is determined according to Example 7; e. The system is connected to an internal regulation process or control room according to Example 2; f. A decision basis is created for possible shutdowns, isolation, and power reductions to protect the equipment, among other things; method. [Example]

[0141] 1. A method for enhancing overheat protection and / or temperature monitoring in a system by introducing additional control parameters, comprising: a. There is an electrical system with temperature monitoring, for example, by a temperature sensor, b. The monitoring system is enhanced by the method according to embodiment 1; c. Extensions introduce additional independent control parameters according to Examples 1 and 5; d. Redundancy improves fault safety and fault recognition; e. Especially in critical systems and critical processes, the instantaneous change of new control parameters allows for a faster response in the event of heating due to a fault; method. [Example]

[0142] 1. A method and arrangement for determining age-induced changes in an electrical system by temperature-dependent resonance point assessment, comprising: a. The electrical system according to Example 5 is characterized; b. the electrical system is periodically tested over a sufficient period of time according to the method of claim 1; c. The system changes its electrical properties, for example by oxidation; d. Thermally dependent changes in transmission characteristics can be identified; e. The change in transmission characteristics is an abstract measure of degradation; Methods and configurations. [Example]

[0143] 1. A method for active fault monitoring ("active health monitoring") of an electrical system by temperature dependent resonance point estimation, comprising: a. The electrical system according to Example 5 is characterized; b. The electrical system is evaluated according to Example 1; c. The fault event changes the electrical characteristics of the electrical system; d. These changes affect the transmission characteristics, e. The changes are classified and their impact on transmission behavior is interpreted; f. This data is aggregated and intelligently evaluated; g. Significant changes in transmission behavior can be directly attributed to changes in system topology or system failures; h. Grid topologies outside the system of interest are ruled out as sources of failure by recalibration or analytical differentiation; method. [Example]

[0144] 1. A method for identifying an electrical system using temperature dependent resonance point estimation, comprising: a. The transmission behavior of current harmonics or the impedance response of the electrical system is identifiable and measurable; b. There is aggregate data recorded according to Examples 1 and 5; c. These data form the basis for system identification, d. An extended measurement configuration with current and temperature sensors determines both the transmission characteristics and the operating temperature of the system to be identified; e. an intelligent self-learning algorithm performs measurements and uses the existing database to predict the best discriminatory features and test the system against them; f. Based on this evaluation, unknown electrical systems can be identified; method. [Example]

[0145] 1. A method for determining an operating point or load of an electrical system by temperature dependent resonance point estimation, comprising: a. The system under investigation and its heat transfer properties are known according to Example 5; b. an extended measurement configuration with current and temperature sensors determines both the transmission characteristics and the operating temperature of the system to be identified; c. The transmission characteristics vary depending on the load and operating point; d. An intelligent self-learning algorithm performs measurements and uses the existing database to predict the best discriminatory features and test the system against them; e. Evaluation of transmission characteristics identifies load conditions or operating points of the electrical system; method. [Example]

[0146] 1. A method for calculating ambient temperature and characteristics of an electrical cable system by temperature dependent resonance point estimation, comprising: a. The operating temperature of the cable is determined using a configuration according to the basic principles from Examples 1 and 10; b. There are expected values ​​for the absolute conductor current and transmission characteristics at the reference temperature; c. Load / current related heating of the system has an instantaneous effect on the properties according to Example 5; d. This change in characteristic in turn causes an instantaneous change in the current in the cable shield, e. The heating rate of the cable shield depends on the heat transfer from the conductor and the ambient temperature in addition to its own current-heat losses, f. The transmission characteristics of the outer conductor are determined according to the modified method of Example 5; g. Different environments have different heat transfer coefficients, which are known; h. The rate of change of the transmission characteristics of the cable shield allows for estimation of the outside temperature; method. [Example]

[0147] 1. A method for extending the transmission capacity of an electrical line by temperature-dependent resonance evaluation, comprising: a. The method according to embodiment 1 is applied to an electric energy transmission line; b. The operating current is not limited by a statically predetermined value (as is usually the case); c. Arbitrarily high currents are allowed as long as the transmission characteristics according to Example 5 do not exceed the predefined critical transmission characteristics; d. Therefore, the actual maximum current is defined according to the actual operating temperature, e. Environment-specific transmission capacity expansion is applied; method. literature [1] A. Morched, L. Marti, and J. Ottevangers, "A high frequency transformer model for the EMTP," IEEE Trans. Power Delivery, Vol. 8, No. 3, pp. 1615-1626, 1993, doi: 10.1109 / 61.252688. [2] A. Morched, B. Gustavsen, and M. Tartibi, "A universal model for accurate calculation of electromagnetic transients on overhead lines and underground cables," IEEE Trans. Power Delivery, Vol. 14, No. 3, pp. 1032-1038, 1999, doi: 10.1109 / 61.772350. [3] A.S. Morched, J.H. Ottevangers, and L. Marti, "Multi-port frequency dependent network equivalents for the EMTP," IEEE Trans. Power Delivery, Vol. 8, No. 3, pp. 1402-1412, 1993, doi: 10.1109 / 61.252667. [4] Finding Danger where It's Impossible to Look | Yokogawa Electric Corporation, [Online] Available at https: / / www.yokogawa.com / library / resources / application-notes / power-cable-monitoring-for-overheating / (accessed May 30, 2022). [5] Monitoring Electrical Cable Challenge: The Future of Underground Inspection | HeroX, [Online] Available at https: / / www.herox.com / DLCCableChallenge (accessed May 30, 2022). [6] D. Clements and P. Mancarella, “Risk of cable overheating and premature aging due to load control measures,” 2017 IEEE Manchester PowerTech, Manchester, United Kingdom, 2017, pp. 1–5, doi: 10.1109 / PTC.2017.7981024. [7] S. Czapp, F. Ratkowski, S. Szultka, and A. Tomaszewski, "Overheating of Underground Power Cable Line Due to Its Partial Exposition to Solar Radiation," 2019 24th International Conference on Methods and Models in Automation and Robotics (MMAR), Miedzyzdroje, Poland, 2019, pp. 396-400, doi: 10.1109 / MMAR.2019.8864691. [8] K. Wu et al., "Study on pyrolysis characteristics of polyethylene outer sheath of 110kV power cable under overheating defect," 2021 IEEE International Conference on Emergency Science and Information Technology (ICESIT), Chongqing, China, November 22-24, 2021, pp. 307-310, doi: 10.1109 / ICESIT53460.2021.9697002. [9] Bundesnetzagentur, “Monitoringbericht 2021 (Monitoring Report 2021)”.

[10] W. Zhu, X. Wang, A. Liang, Y. Zhao, X. Fan, and G. Liu, "Thermal Effect of Short-term Overload on High-voltage Cross-linked Polyethylene (XLPE) Cable Insulation," IOP Conf. Ser.: Mater. Sci. Eng., Vol. 746, No. 1, pp. 12001, 2020, doi: 10.1088 / 1757-899x / 746 / 1 / 012001.

[11] Y.-C. Yu and S.-W. Jee, "Investigation on the Ignition of Self-Regulating Heating Cables due to Overheating," Fire Sci. Eng., Vol. 35, No. 6, pp. 100-104, 2021, doi: 10.7731 / KIFSE.f710fe7e.

[12] DIN IEC 62895 (VDE 0276-2895), February 2019.

[13] S. Ali, A. Hanif, and Q. Ahmed, "Review in thermal effects on the performance of electric motors," 2016 International Conference on Intelligent Systems Engineering (ICISE), 2016, doi: 10.1109 / intelse.2016.7475166.

[14] R. Rothe and K. Hameyer, “Life expectancy calculation for electric vehicle traction motors regarding dynamic temperature and driving cycles,” International Electrical and Mechanical Drives Conference (IEMDC), Niagara Falls, ON, Canada, 2011, pp. 1306–1309, doi: 10.1109 / IEMDC.2011.5994793.

[15] C. Kral, A. Haumer, and S.B. Lee, "Innovative thermal model for the estimation of permanent magnet and stator winding temperatures," 2012 IEEE Energy Conversion Congress and Exposition (ECCE), Raleigh, NC, USA, 2012, pp. 2704–2711, doi: 10.1109 / ECCE.2012.6342386.

[16] Oliver Wallscheid, Tobias Huber, Wilhelm Peters, Joachim B. ·· Rocker, Real-Time Capable Methods to Determine the Magnet Temperature of Permanent Magnet Synchronous Motors - A Review: Oct. 29, 2014 - Nov. 1, 2014, Dallas, TX, USA Piscataway, NJ: IEEE, 2014. [Online] Available at http: / / ieeexplore.ieee.org / servlet / opac?punumber=7036020.

[17] T. Sebastian, "Temperature effects on torque production and efficiency of PM motors using NdFeB magnets," IEEE Trans. on Ind. Applicat., Vol. 31, No. 2, pp. 353-357, 1995, doi: 10.1109 / 28.370284.

[18] N. Amann, J. Bocker, and F. Prenner, "Active Damping of Drive Train Oscillations for an Electrically Driven Vehicle," IEEE / ASME Trans. Mechatron., Vol. 9, No. 4, pp. 697-700, 2004, doi: 10.1109 / TMECH.2004.839036.

[19] T. Orlik, J. Klock, and W. Schumacher, "Influence of magnetic saturation on sensorless-controlled interior permanent magnet synchronous motors," 2013 15th European Conference on Power Electronics and Applications (EPE), Lille, France, September 2–6, 2013, pp. 1–10, doi: 10.1109 / EPE.2013.6631753.

[20] Oliver Wallscheid, Prof. Dr.-Ing. Joachim Boecker, “Efficiency-Optimal Operation Point Control for an Interior Permanent Magnet Synchronous Motor Considering Temperature Variations,” Conference: Internationaler ETG-Kongress, Vol. 2013, 2013. [Online] https: / / www.researchgate.net / publication / 260793787_Wirkungsgradoptimale_Arbeitspunktsteuerung_fur_en_permanenterregten_Synchronmotor_mit_vergrabenen_Magneten_unter_ Available at Berucksichtigung_von_Temperatureinflussen

[21] M.Y. Frolov and A.G. Fishov, "Electric parameters identification of synchronous generator connecting to the grid," 2016 11th International Forum on Strategic Technology (IFOST), Novosibirsk, Russia, 2016, pp. 243-246, doi: 10.1109 / IFOST.2016.7884238.

[22] J. Kudelcik, P. Bury, J. Drga, P. Kopcansky, V. Zavisova, and M. Timko, “Temperature Effect on the Structure of Transformer Oil Based Magnetic Fluids Using Acoustic Spectroscopy,” Acta Phys. Pol. A, vol. 121, pp. 5-6, 1169-1171, 2012, doi: 10.12693 / APhysPolA.121.1169.

[23] Y. Du, M. Zahn, N. Altamirano, and M. Sarda, Moisture and temperature effects on the dielectric spectrum of transformer pressboard: Conference on Electrical Insulation and Dielectric Phenomena, October 20-24, 2002, Cancun, Quintana Roo, Mexico. Piscataway, NJ: IEEE Service Center, 2002. [Online] Available at http: / / ieeexplore.ieee.org / servlet / opac?punumber=8111

[24] J.H. Yew, M.K. Pradhan, and T.K. Saha, “Effects of moisture and temperature on the frequency domain spectroscopy analysis of power transformer insulation,” Energy Society General Meeting, Pittsburgh, PA, USA, 2008, pp. 1–8, doi: 10.1109 / PES.2008.4596244.

[25] J. Hill, Z. Wang, Q. Liu, C. Krause, and G. Wilson, “Analyzing the power transformer temperature limitation for avoidance of bubble formation,” High Voltage, Vol. 4, No. 3, pp. 210–216, 2019, doi: 10.1049 / hve.2019.0034.

[26] S.A. Mousavi, M. Sedighizadeh, A. Hekmati, and M. Bigdeli, "Artificial neural network based method for temperature correction in FDS measurement of transformer insulation," J. Phys. D: Appl. Phys., Vol. 53, No. 14, pp. 145103, 2020, doi: 10.1088 / 1361-6463 / ab62c2.

[27] T. Lochner, RM Kluge, J. Fichtner, HA El-Sayed, B. Garlyyev, and AS Bandarenka, “Temperature Effects in Polymer Electrolyte Membrane Fuel Cells,” ChemElectroChem, Vol. 7, No. 17, pp. 3545–3568, 2020, doi: 10.1002 / celc.202000588.

[28] A. Kraytsberg and Y. Ein-Eli, "Review of Advanced Materials for Proton Exchange Membrane Fuel Cells," Energy Fuels, Vol. 28, No. 12, pp. 7303-7330, 2014, doi: 10.1021 / ef501977k.

[29] Andreas Vath, "Dreidimensionale dynamische Modellierung und Berechnung von Polymer-Elektrolyt-Membran-Brennstoffzellensystemen (Three-dimensional dynamic modelling and calculation of polymer electrolyte membrane fuel cell systems)," 2009.

[30] Kejun Qian, Chengke Zhou, Vue Yuan, Malcolm Allanl, Temperature Effect on Electric Vehicle Battery Cycle Life in Vehicle-to-Grid Applications, China International Conference on Electricity Distribution (CICED), 2010, 13-16 Sept. 2010, Nanjing, China. Piscataway, NJ: IEEE, 2010. [Online] Available at http: / / ieeexplore.ieee.org / servlet / opac?punumber=5723784

[31] W. Xu, J. Xu, B. Liu, J. Liu, and X. Yan, "A multi-timescale adaptive dual particle filter for state of charge estimation of lithium-ion batteries considering temperature effect," Energy Sci Eng, Vol. 8, No. 8, pp. 2784-2798, 2020, doi: 10.1002 / ese3.694.

[32] K. Li, F. Wei, K.J. Tseng, and B.-H. Soong, "A Practical Lithium-Ion Battery Model for State of Energy and Voltage Responses Prediction Incorporating Temperature and Aging Effects," IEEE Trans. Ind. Electron., Vol. 65, No. 8, pp. 6696-6708, 2018, doi: 10.1109 / TIE.2017.2779411.

[33] K. Liu, C. Zou, K. Li, and T. Wik, "Charging Pattern Optimization for Lithium-Ion Batteries With an Electrothermal-Aging Model," IEEE Trans. Ind. Inf., Vol. 14, No. 12, pp. 5463-5474, 2018, doi: 10.1109 / TII.2018.2866493.

[34] P. Kreczanik, P. Venet, A. Hijazi, and G. Clerc, "Study of Supercapacitor Aging and Lifetime Estimation According to Voltage, Temperature, and RMS Current," IEEE Trans. Ind. Electron., Vol. 61, No. 9, pp. 4895-4902, 2014, doi: 10.1109 / tie.2013.2293695.

[35] R. Kristina Schneider Barcelos, W. Cardoso Celeste, L. Otavio Rigo Junior, and G. de Lorena Diniz Chaves, "Identification of Similar Loads for Electric Power Management in Smart Grid," IEEE Latin Am. Trans., Vol. 17, No. 08, pp. 1318-1325, 2019, doi: 10.1109 / TLA.2019.8932341.

[36] Thermal degradation of polyimide insulation and its effect on electromagnetic coil impedance, 2017, [Online] Available at https: / / www.mfpt.org / wp-content / uploads / 2019 / 10 / paper-_-jameson.pdf

[37] Mesago PCIM GmbH, PCIM Europe 2018: International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management : 5-7 June 2018 Nuernberg. Frankfurt am Main: VDE, 2018. [Online] Available at http: / / ieeexplore.ieee.org / xpl / mostRecentIssue.jsp?punumber=8402798

[38] M. Aly, E.M. Ahmed, and M. Shoyama, "Developing new lifetime prolongation SVM algorithm for multilevel inverters with thermally aged power devices," IET Power Electronics, Vol. 10, No. 15, pp. 2248-2256, 2017, doi: 10.1049 / iet-pel.2017.0327.

[39] X. Perpina, A. Castellazzi, M. Piton, M. Mermet-Guyennet, and J. Millan, "Failure-relevant abnormal events in power inverters considering measured IGBT module temperature inhomogeneities," Microelectronics Reliability, vol. 47, pp. 9-11, 1784-1789, 2007, doi: 10.1016 / j.microrel.2007.07.071.

[40] H. Bessei, Sicherungshandbuch: Starkstromsicherungen ; das Handbuch fuer Anwender von Niederspannungs- und Hochspannungssicherungen (Fuse Handbook: User's Handbook for Low-Voltage and High-Voltage Fuses), 5th ed., Lappersdorf: Kerschensteiner, 2011.

[41] G. Ziegler, Digitaler Differentialschutz: Grundlagen und Anwendungen (Digital Differential Protection: Fundamentals and Applications), 2nd edition, Erlangen: Publicis Publ, 2013, [Online] Available at http: / / swb.eblib.com / patron / FullRecord.aspx?p=1120067

[42] K. Gouramanis and C. Demoulias, "Cable Overheating in an Industrial Substation Feeder Due to Untransposed Power Cables - Measurement and Simulation," EUROCON 2005 - The International Conference on “Computer as a Tool”, Belgrade, Serbia and Montenegro, 2005, pp. 1438-1441, doi: 10.1109 / EURCON.2005.1630233.

[43] A. Hochrainer, Symmetrische Komponenten in Drehstromsystemen (Symmetrical Components in Three-Phase Systems). Berlin, Heidelberg: Springer Berlin Heidelberg, 1957.

[44] IEEE Standard for Calculating the Current-Temperature Relationship of Bare Overhead Conductors, Piscataway, NJ, USA.

[45] “Aging mechanisms and diagnostics for power cables – an overview,” IEEE Electr. Insul. Mag., Vol. 17, No. 1, pp. 14-22, 2001, doi: 10.1109 / 57.901613.

[46] V.A. Shikhin, A.E. Kochengin, and G.P. Pavliuk, "Significant Events Detection and Identification through Electrical Grid Load Profile," 2018 Renewable Energies, Power Systems & Green Inclusive Economy (REPS-GIE), Casablanca, 2018, pp. 1–5, doi: 10.1109 / REPSGIE.2018.8488857.

[47] Frolov M. Yu. and Fishov A.G., "Identification of Synchronous Generator Electric Parameters Connected to the Distribution Grid," Problems of the Regional Energetics, Vol. 33, No. 1, pp. 32-39, 2017. [Online] Available at: https: / / doaj.org / article / 070bf5bb2b1447ac9d23ca4c77f01541

[48] ​​E. Bulycheva and S. Yanchenko, "Real-time harmonic identification under varying grid conditions," Serb J Electr Eng, Vol. 18, No. 1, pp. 29-48, 2021, doi: 10.2298 / SJEE2101029B.

[49] R. McCarty and R. Piper, "Voltage~Current Curves to Characterize Thermoelectric Generators" (English), J. Electron. Mater., Vol. 44, No. 6, pp. 1896-1901, 2015, doi: 10.1007 / s11664-014-3585-4.

[50] L. Peretto et al., "Monitoring Cable Current and Laying Environment Parameters for Assessing the Aging Rate of MV Cable Joint Insulation," 2018 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Cancun, 2018, pp. 390-393, doi: 10.1109 / CEIDP.2018.8544904.

[51] F. Donazzi, E. Occhini, and A. Seppi, "Soil thermal and hydrological characteristics in designing underground cables," Proc. Inst. Electr. Eng. UK, Vol. 126, No. 6, p. 506, 1979, doi: 10.1049 / piee.1979.0119.

[52] P. Caramia, G. Carpinelli, A. Russo, and P. Verde, "Estimation of thermal useful life of MV / LV cables in presence of harmonics and moisture migration," 2003 IEEE Bologna Power Tech, Bologna, Italy, 2003, pp. 130-134, doi: 10.1109 / PTC.2003.1304300.

[53] C. Holyk and G. J. Anders, "Power Cable Rating Calculations - A Historical Perspective [History]," IEEE Ind. Appl. Mag., Vol. 21, No. 4, pp. 6-64, 2015, doi: 10.1109 / MIAS.2015.2417094.

[54] Z. Yu, S. Xiaohui, L. Jianfang, and G. Fei, "Cable Overheating Risk Warning Method Based on Impedance Parameter Estimation in Distribution Network" (in English), IOP Conf. Ser.: Mater. Sci. Eng., Vol. 199, No. 1, pp. 12044, 2017, doi: 10.1088 / 1757-899X / 199 / 1 / 012044.

[55] A. Jamali-Abnavi, H. Hashemi-Dezaki, A. Ahmadi, E. Mahdavimanesh, and M.-J. Tavakoli, "Harmonic-based thermal analysis of electric arc furnace's power cables considering even current harmonics, forced convection, operational scheduling, and environmental conditions," International Journal of Thermal Sciences, Vol. 170, pp. 107135, 2021, doi: 10.1016 / j.ijthermalsci.2021.107135.

[56] H.M. Lee, G.S. Lee, G.-Y. Kwon, S.S. Bang, and Y.-J. Shin, "Industrial Applications of Cable Diagnostics and Monitoring Cables via Time-Frequency Domain Reflectometry," IEEE Sensors J., Vol. 21, No. 2, pp. 1082-1091, 2021, doi: 10.1109 / JSEN.2020.2997696.

[57] K. Walczak and J. Gielniak, "Temperature Distribution in the Insulation System of Condenser-Type HV Bushing - Its Effect on Dielectric Response in the Frequency Domain," Energies, Vol. 14, No. 13, pp. 4016, 2021, doi: 10.3390 / en14134016.

[58] A. Specht and J. Bocker, "Observer for the rotor temperature of IPMSM," 2010 14th International Power Electronics and Motion Control Conference (EPE / PEMC 2010), Ohrid, Macedonia, 2010, doi: 10.1109 / EPEPEMC.2010.5606818.

[59] A. Specht, O. Wallscheid, and J. Bocker, "Determination of rotor temperature for an interior permanent magnet synchronous machine using a precise flux observer," 2014 International Power Electronics Conference (IPEC-Hiroshima 2014 ECCE-ASIA), Hiroshima, Japan, 2014, pp. 1501–1507, doi: 10.1109 / IPEC.2014.6869784.

[60] M. Ganchev, C. Kral, and T. Wolbank, "Hardware and software implementation of sensorless rotor temperature estimation technique for Permanent Magnet Synchronous Motor," 2012 Electrical Systems for Aircraft, Railway and Ship Propulsion (ESARS), Bologna, Italy, 2012, pp. 1–6, doi: 10.1109 / ESARS.2012.6387420.

[61] M. Ganchev, C. Kral, and T. Wolbank, "Sensorless rotor temperature estimation of permanent magnet synchronous motor under load conditions," IECON 2012 - 38th Annual Conference of IEEE Industrial Electronics, Montreal, QC, Canada, 2012, pp. 1999–2004, doi: 10.1109 / IECON.2012.6388895.

[62] D. D. Reigosa, F. Briz, P. Garcia, J. M. Guerrero, and M. W. Degner, "Magnet Temperature Estimation in Surface PM Machines Using High-Frequency Signal Injection," IEEE Trans. on Ind. Applicat., Vol. 46, No. 4, pp. 1468-1475, 2010, doi: 10.1109 / TIA.2010.2049816.

[63] D. Reigosa, F. Briz, M.W. Degner, P. Garcia, and J.M. Guerrero, "Magnet temperature estimation in surface PM machines during six-step operation," 2011 IEEE Energy Conversion Congress and Exposition (ECCE), Phoenix, AZ, USA, 2011, pp. 2429–2436, doi: 10.1109 / ECCE.2011.6064091.

[64] C. Kral, A. Haumer, and S.B. Lee, "A Practical Thermal Model for the Estimation of Permanent Magnet and Stator Winding Temperatures," IEEE Trans. Power Electron., Vol. 29, No. 1, pp. 455-464, 2014, doi: 10.1109 / TPEL.2013.2253128.

[65] T. Bauml, C. Jungreuthmayer, and C. Kral, "An innovative parametrization method for a thermal equivalent circuit model of an interior permanent magnet synchronous machine," IECON 2011 - 37th Annual Conference of IEEE Industrial Electronics, Melbourne, Vic, Australia, 2011, pp. 1746-1751, doi: 10.1109 / IECON.2011.6119570.

[66] X. Lu, S. Zhou, and C. Zhao, "Finite element method analyses of ambient temperature effects on characteristics of piezoelectric motors," Journal of Intelligent Material Systems and Structures, Vol. 25, No. 3, pp. 364-377, 2014, doi: 10.1177 / 1045389X13498309.

[67] S. Cheng, Du Yi, J.A. Restrepo, P. Zhang, and T.G. Habetler, "A Nonintrusive Thermal Monitoring Method for Induction Motors Fed by Closed-Loop Inverter Drives," IEEE Trans. Power Electron., Vol. 27, No. 9, pp. 4122-4131, 2012, doi: 10.1109 / TPEL.2012.2188045.

[68] J.H. Yew, T.K. Saha, and A.J. Thomas, “Impact of temperature on the frequency domain dielectric spectroscopy for the diagnosis of power transformer insulation,” 2006 IEEE Power Engineering Society General Meeting, Montreal, Que., Canada, 2006, 7th ed., doi: 10.1109 / PES.2006.1709037.

[69] S.A. Mousavi, M. Sedighizadeh, A. Hekmati, and M. Bigdeli, "Artificial neural network based method for temperature correction in FDS measurement of transformer insulation," J. Phys. D: Appl. Phys., Vol. 53, No. 14, pp. 145103, 2020, doi: 10.1088 / 1361-6463 / ab62c2.

[70] M. Sippola and R. E. Sepponen, "Accurate prediction of high-frequency power-transformer losses and temperature rise," IEEE Trans. Power Electron., Vol. 17, No. 5, pp. 835-847, 2002, doi: 10.1109 / TPEL.2002.802193.

[71] W. Wang, Y. Liu, J. Bi, Y. Gong, and Y. Deng, "Effect Factors Analysis of Frequency Domain Spectroscopy Test," 2012 IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC), Shanghai, China, 2012, pp. 1–5, doi: 10.1109 / APPEEC.2012.6307328.

[72] B. Gustavsen and A. Semlyen, "A Robust Approach for System Identification in the Frequency Domain," IEEE Trans. Power Delivery, Vol. 19, No. 3, pp. 1167-1173, 2004, doi: 10.1109 / TPWRD.2003.822530.

[73] D.D. Macdonald, E. Sikora, and G. Engelhardt, "Characterizing electrochemical systems in the frequency domain" (Eng), Electrochimica Acta, Vol. 43, 1-2, pp. 87-107, 1998, doi: 10.1016 / s00134686(97)00238-7.

[74] R. Srinivasan, BG Carkhuff, MH Butler, and AC Baisden, "Instantaneous measurement of the internal temperature in lithium-ion rechargeable cells," Electrochimica Acta, Vol. 56, No. 17, pp. 6198-6204, 2011, doi: 10.1016 / j.electacta.2011.03.136.

[75] R.R. Richardson and D.A. Howey, "Sensorless Battery Internal Temperature Estimation Using a Kalman Filter With Impedance Measurement," IEEE Trans. Sustain. Energy, Vol. 6, No. 4, pp. 1190-1199, 2015, doi: 10.1109 / TSTE.2015.2420375.

[76] Y. Beck and R. Machlev, "Harmonic Loads Classification by Means of Currents' Physical Components," Energies, Vol. 12, No. 21, pp. 4137, 2019, doi: 10.3390 / en12214137.

[77] P. Netzharmonie, “Netzharmonie Schlussbericht (Final Report): FKZ 0325757A-L”.

[78] M. Li, C. Zhou, and W. Zhou, "A Revised Model for Calculating HV Cable Sheath Current Under Short-Circuit Fault Condition and Its Application for Fault Location-Part 1: The Revised Model," IEEE Trans. Power Delivery, Vol. 34, No. 4, pp. 1674-1683, 2019, doi: 10.1109 / TPWRD.2019.2918159.

[79] IEC 60544: Electrical insulating materials - Determination of the effects of ionizing radiation - Part 1: Radiation interaction and dosimetry, IEC, June 2013.

[80] M. Celina, K.T. Gillen, J. Wise, and R.L. Clough, "Anomalous aging phenomena in a crosslinked polyolefin cable insulation," Radiation Physics and Chemistry, Vol. 48, No. 5, pp. 613-626, 1996, doi: 10.1016 / 0969-806X(96)00083-7.

[81] E. Carpaneto, G. Chicco, R. Napoli, and M. Scutariu, "Electricity customer classification using frequency domain load pattern data," International Journal of Electrical Power & Energy Systems, Vol. 28, No. 1, pp. 13-20, 2006, doi: 10.1016 / j.ijepes.2005.08.017.

[82] H. Li, Z. Wang, T. Hong, A. Parker, and M. Neukomm, "Characterizing patterns and variability of building electric load profiles in time and frequency domains," Applied Energy, volume 291, pages 116721, 2021, doi: 10.1016 / j.apenergy.2021.116721.

[83] S. Zhong and K.-S. Tam, "A Frequency Domain Approach to Characterize and Analyze Load Profiles," IEEE Trans. Power Syst., Vol. 27, No. 2, pp. 857-865, 2012, doi: 10.1109 / TPWRS.2011.2170592.

Claims

1. 1. A method for calculating at least one thermal characteristic of an electrical system (1) based on an evaluation of resonance points (R1, R2, R3) of said electrical system (1), said electrical system comprising one or more of the following components: an arrangement of electrical energy transmission lines, stationary electrical machines such as, for example, transformers, electrochemical energy converters, electrical energy storage devices, inverters, protection techniques such as, for example, fuses, a) applying a system excitation to the electrical system (1), the system excitation comprising one or more pre-calculated excitation frequencies, the excitation frequencies being suitable for exciting the electrical system (1) at one or more pre-calculated resonance points (R1, R2, R3) of the electrical system; b) at least the input current (I 入力 ) and output current (I 出力 ), and / or other electrical characteristics that allow determining the frequency and time-dependent impedance of the electrical system (1); c) determining a result quantity by evaluating the electrical characteristic quantities measured in step b) by one or more analytical transformation methods at one or more pre-calculated resonance points (R1, R2, R3) of the electrical system (1); d) determining at least one thermal characteristic quantity of the electrical energy transmission line arrangement, the fixed electrical machine, the electrochemical energy converter, the electrical energy storage device, the inverter and / or the protection technology of the electrical system (1) by relating the resulting quantity calculated in step c) to predetermined characteristic nominal values ​​for the electrical system in defined nominal conditions; A method comprising:

2. 2. The method of claim 1, wherein steps a) to d) of claim 1 are repeated at regular or irregular time intervals.

3. 3. The method according to claim 2, wherein the time interval is reduced when the determined thermal characteristic quantity approaches a predetermined limit value (α).

4. The repetition rate of steps a) to d) of claim 1 is determined based on the following criteria: i) the change in the grid impedance of the electrical system (1) at the grid connection point (NVP); ii) the validity of said result quantity; iii) the degree of agreement between the resultant quantities and a thermal model of the electrical system (1); 4. The method according to claim 2 or 3, characterized in that it is defined according to one or more of the following:

5. 5. The method according to claim 1, wherein at least one electrical load applied to the electrical system (1) is automatically reduced when the determined thermal characteristic reaches or exceeds a predefined limit value.

6. In a defined nominal state of the electrical system (1), a) calculating the resonance points (R1, R2, R3) of the electrical system (1); b) calculating an excitation frequency for exciting the electrical system (1) at one or more resonance points (R1, R2, R3); 6. The method according to claim 1, wherein the step of:

7. The method according to any one of claims 1 to 6, wherein additional resonance points outside the system are generated and used to calculate the thermal state of the electrical system (1).

8. 8. The method according to claim 1, wherein the electrical system (1) comprises at least one grounded energy transmission line, and wherein a shield current of at least one of the grounded energy transmission lines is measured and evaluated to determine the at least one thermal characteristic quantity.

9. A computer program comprising program code means designed to carry out the method according to any one of claims 1 to 8, when the computer program is run on a computer.

10. At least one control unit (20) and an input current I of the electrical system (1) to be tested 入力 ) and output current (I 出力 and current sensors (21, 22, 23, 24) connected to the control unit (20), the current sensors (21, 22, 23, 24) being designed to detect a voltage drop across the ...

Images