METHOD FOR TESTING THE WIRING OF AN ELECTRICAL SYSTEM

Description

GEBIET DER ERFINDUNG

[0001] The present invention relates to methods for testing the wiring of an electrical installation, in particular for testing the wiring of an electrical installation with multiple circuits, for example an electrical power plant in, for example, a substation or a power station. BACKGROUND

[0002] Wiring errors can occur during the installation, repair, or expansion of an electrical system, for example, in a substation or power plant. Particularly in systems with multiple circuits and / or multiple phases, such as three-phase AC systems, conductors can be reversed. For instance, two live conductors can be swapped, or a live conductor can be swapped with the neutral conductor. Furthermore, polarity can be reversed, for example, when connecting a transformer. Therefore, before commissioning or recommissioning an electrical system, a wiring test is typically performed to identify incorrectly connected conductors and reversed polarities.

[0003] For example, test signals can be injected sequentially into the individual phases at a power supply point, and a measurement signal can be recorded at a remote measuring point where, according to the intended wiring, the test signal should have an effect. If the expected effect of the test signal is not detected at the measuring point, a wiring fault may be present. This procedure is relatively complex, as several measurements must be carried out to check multiple circuits and phases, and the measuring device must be connected to both the power supply point and the measuring point for each measurement. Furthermore, while such a measurement can confirm the presence of a wiring fault, it is not immediately possible to determine the specific type of fault, such as whether conductors are reversed or disconnected.

[0004] The correct polarity of a current and voltage transformer must also be checked. Incorrect polarity can, for example, lead to a malfunction of a protective relay. In measuring circuits, incorrect polarity can result in an apparently opposite direction of current flow and thus inaccurate measurement results. For these applications, it is also important to check the correct phase assignment from the measuring transformer to the protective relay or meter.

[0005] Other methods exist for testing polarity. They can also be used to verify correct phase assignment by proceeding phase by phase and checking whether the expected reaction occurs in the phase being tested.

[0006] For example, a DC voltage test can be performed. In this test, a battery is briefly connected to one side of the current transformer, and the momentary reading of a milliammeter or millivoltmeter connected to the other side is recorded. The direct current flowing during this test could magnetize the current transformer. The resulting saturation can cause malfunctions in the protection system. Therefore, it is important to demagnetize any current transformer tested using this method afterward. This method can also be used to check the polarity and phase assignment along the secondary wiring. However, this requires one person to operate the battery switch and another person to perform the measurement at a different location at precisely the same time.

[0007] In other examples, an AC voltage test with phase comparison can be performed. In this test, an AC voltage or current is applied to one side of the instrument transformer, and the phase of the voltage or current on the other side is determined, for example, using an oscilloscope, a dedicated phase meter, or a relay tester with this function. If the phase comparison shows approximately 0°, the polarity is correct; at approximately 180°, the polarity is reversed. If the expected signal cannot be measured at a specific test point, this usually indicates a wiring problem. The phase comparison can easily be performed directly at the instrument transformer. For testing the secondary winding to the relay or meter, the same AC voltage reference must be available at the respective measurement location.For this purpose, either a separate cable carrying the AC voltage reference is laid to the measuring point, or a common reference, such as the mains AC voltage, is used. In the latter case, it is essential to ensure that the same phase of the mains voltage is available at all measuring points.

[0008] Many energy technology systems use a three-phase alternating current system.

[0009] Many test instruments also have at least three current or voltage outputs. These instruments allow test signals to be fed in simultaneously, enabling the wiring of all phases to be tested in a single operation. For example, a single test signal with different amplitudes can be used for the various phases. In particular, amplitudes for currents and voltages can be used, the combination and / or subtraction of which results in new amplitudes that would not otherwise occur.

[0010] Example: L1 = 3 L1 + L2 = 8 L1 - L2 = - 2 L1+L2+L3 = 17 L2 = 5 L1 + L3 = 12 L1 - L3 = - 6 L1+L2-L3 = -1 L3 = 9 L2 + L3 = 14 L2 - L3 = - 4 L1-L2+L3 = 7 -L1+L2+L3 = 11

[0011] This allows wiring errors to be detected based on the measured amplitude, e.g. if the return conductor of a phase is incorrectly connected.

[0012] However, the current or voltage amplitudes must differ relatively significantly to allow for unambiguous assignment. Therefore, it is not always possible to work with amplitudes close to the nominal range of the equipment (e.g., 1A, 5A, or 100V). Furthermore, in practice, it is common to find multiple parallel connections or ground connections. In these cases, the current or voltage is divided according to the respective resistances. Phase identification is then no longer unambiguous.

[0013] Publication JP 2023 096699 A discloses a method for testing the wiring of an electrical installation, wherein the test signals are fed into only a single terminal. Each test signal consists of a single higher harmonic of a reference signal. SUMMARY OF THE INVENTION

[0014] There is a need for improved methods for testing the wiring of an electrical system with multiple circuits, which can be carried out quickly and reliably using simple means.

[0015] According to the present invention, a method for testing the wiring of an electrical installation with multiple circuits and a test device for testing the wiring of an electrical installation with multiple circuits are provided, as defined in the independent claims. The dependent claims define embodiments of the invention.

[0016] A method according to the invention for testing the wiring of an electrical system with multiple circuits comprises generating several test signals. Each of the several test signals has a combination of predetermined harmonics with at least one, preferably at least two, higher harmonics. The amplitude and / or phase (hereinafter often referred to simply as "phase") of the at least one higher harmonic of the several test signals are different.

[0017] In other words, each of the multiple test signals comprises a combination of predefined harmonics. At least one higher harmonic of these predefined harmonics is varied differently in each of the multiple test signals with respect to phase and / or amplitude. Thus, each test signal has its own unique combination of amplitude and phase for at least one harmonic.

[0018] For example, each of the multiple test signals comprises one or more harmonics that are identical for each of the multiple test signals (especially with respect to phase and amplitude). Furthermore, each of the test signals comprises at least one further higher harmonic. This at least one further higher harmonic has a specific variation in phase and / or amplitude for each of the multiple test signals. The phase and / or amplitude of this at least one further higher harmonic are therefore different for the various test signals.

[0019] For example, in each of the multiple test signals, the first, second, and third harmonics may be the same, while the fourth and fifth harmonics, which in this example correspond to at least one higher harmonic, may have different phases and / or amplitudes in the different test signals. In a simple example, each test signal can include a first harmonic and a second harmonic. The first harmonic is the same in all test signals, and the second harmonic has different phases in the different test signals.

[0020] The following terminology applies to this description. A fundamental oscillation of frequency f is called the first harmonic. An oscillation with twice the frequency (2f) is called the second harmonic. In general, the oscillation with n times the frequency nf is the nth harmonic. All harmonics except the first harmonic are called higher harmonics. Higher harmonics are also called overtones. The nth harmonic is called the (n-1)th overtone.

[0021] The term "phase" has the following meanings in this description. Firstly, it is used in connection with polyphase alternating current. For example, in electrical engineering, a form of polyphase alternating current is called three-phase alternating current, which consists of three individual alternating currents or voltages of the same frequency, whose phase angles are fixed at 120° relative to each other. Each of these individual alternating currents or voltages can be assigned to components of a polyphase electrical system, such as a conductor of a power transmission cable or a winding of a transformer or generator. This allows the polyphase electrical system to have several interconnected circuits, which are referred to as phases.

[0022] On the other hand, the term "phase" is also used in this description to describe the phase relationship between periodic signals within an electrical signal. For example, an electrical signal, such as an electrical voltage, can include a sine wave at 50 Hz and a sine wave at 100 Hz. The phase relationship, or simply "phase," describes the phase angle between the zero crossings of these oscillations.

[0023] Each of the multiple test signals can exhibit a time-domain asymmetric waveform. This time-domain asymmetric waveform includes a first harmonic (fundamental oscillation). The waveform is periodic with the frequency of this fundamental oscillation. Time-domain asymmetric means that the waveform, plotted as a signal level over time, cannot be mapped onto itself by reflection across a signal level axis perpendicular to the time axis. An example of such a time-domain asymmetric waveform is the tilting oscillation or sawtooth waveform, which might feature a rising edge with a small slope and a falling edge with a large (but negative) slope.

[0024] For example, each of the multiple test signals can exhibit a time-domain asymmetric waveform, which is formed by superimposing a first harmonic, a second harmonic, and a third harmonic, each with corresponding amplitude factors. In this case, the time-domain asymmetric waveform includes, for example, a fundamental frequency and at least a second and third harmonic. In another example, the time-domain asymmetric waveform can include, in addition to the fundamental frequency, only either the second or the third harmonic. The at least one higher harmonic can, for example, include two higher harmonics, namely a fourth harmonic and a fifth harmonic, where the fourth and fifth harmonics differ in amplitude and / or phase between the various test signals.The asymmetrical waveform in the time domain, formed from the fundamental frequency and the second and third harmonics, can be superimposed with the fourth and fifth harmonics with different amplitudes and / or phases. For example, a first test signal among several test signals can, in addition to the fundamental frequency and the second and third harmonics, contain a fourth harmonic with an amplitude factor of 1.35 / 16 and a phase shift of +30° relative to an amplitude or phase of the fundamental frequency, and a fifth harmonic with an amplitude factor of 1 / 25 and a phase shift of -30° relative to an amplitude or phase of the fundamental frequency. A second test signal among several test signals can, in addition to the fundamental frequency and the second and third harmonics, contain a fourth harmonic with an amplitude factor of 1 / 16 and a phase shift of -30° relative to an amplitude or phase of the fundamental frequency.The test signal can include the phase of the fundamental frequency and a fifth harmonic with an amplitude factor of 0.5 / 25 and a phase shift of -30° relative to the amplitude or phase of the fundamental frequency. A third test signal, among several others, can include, in addition to the fundamental frequency and the second and third harmonics, a fourth harmonic with an amplitude factor of 1 / 16 and a phase shift of 0° (i.e., no phase shift) relative to the amplitude or phase of the fundamental frequency, and a fifth harmonic with an amplitude factor of 0.5 / 25 and a phase shift of -30° relative to the amplitude or phase of the fundamental frequency. In the example above, it is important that the test signals differ from each other in at least one of the fourth and fifth harmonics, either in amplitude or phase.In principle, it is sufficient, for example, if the test signals differ from each other only in phase at the fourth harmonic. The more clearly the test signals differ from each other, for example through different phases and amplitudes in both the fourth and fifth harmonics, the more reliably the test signals can be identified, which is important for the procedure, as will be explained below.

[0025] Overall, the combination of harmonics from the multiple test signals is designed such that any linear combination of these signals exhibits essentially the same time-domain properties as the individual test signals. This can be achieved, for example, by ensuring that the test signals differ only in their higher harmonics (e.g., the fourth and fifth harmonics) and are phase-synchronous with respect to the fundamental frequency. By modifying the higher harmonics (e.g., the phase and / or amplitude of the fourth and fifth harmonics), it is also possible to identify which individual signals are present in a summed signal, i.e., the linear combination. Thus, the individual signals can be identified, and the sum signal can also be easily determined from which sub-signals it comprises.

[0026] The multiple test signals generated in this way are fed into the electrical system at a first point via several first connections, which are assigned to the multiple circuits of the electrical installation. These multiple circuits can, for example, comprise multiple phases of the electrical installation. A different test signal is fed into each of the first connections. In other words, a different test signal is fed into each circuit of the electrical installation at the first point.

[0027] At a second point in the electrical installation, multiple measurement signals can be acquired at several secondary terminals, each corresponding to a different circuit. For example, in a substation, the first terminal might be at an input, and the second at one of the outputs. Alternatively, the first terminal could be at the first side of a transformer, and the second at the second side. Based on the input test signals and the acquired measurement signals, a mapping can be established between each of the first terminals and each of the second terminals. This allows, for instance, the wiring of the electrical installation to be tested based on these mappings.Since the test signals are different, it is possible to clearly determine which test signal at which of the second terminals resulted in a corresponding measurement signal, thus establishing a clear correlation between the first and second terminals. For example, swaps or open circuits can be easily detected using the test signals.

[0028] For example, in the case of a wiring error, an assignment may be determined that does not correspond to a desired or specified assignment, or no assignment or an incomplete assignment may be possible, for example due to interruptions or connections with completely incorrect circuits. In the error-free case, however, an assignment can be determined that corresponds to a specified "target assignment".

[0029] The different phases and / or amplitudes of at least one higher harmonic of the various test signals, for example, the different phases and / or amplitudes of the fourth and fifth harmonics in the different test signals, thus ensure a unique identification of the test signals. By adding another harmonic, for example, the sixth harmonic, the number of different identifications and therefore the number of different test signals can be increased. This allows, for example, test signals for testing the wiring of an electrical installation with more than three phases or circuits, such as for testing two three-phase system sections (i.e., a total of six phases), or system sections with multiple circuits (e.g., with six or more circuits).In principle, it is sufficient if only one higher harmonic exhibits different phases and / or amplitudes for different test signals. For example, if three different phases and three different amplitudes are used at the fourth harmonic, nine different test signals can already be generated. In another example, only three different phases are used at the fourth harmonic, which can still generate three different test signals. However, the more distinguishing features are present, the better the different test signals can be differentiated from one another.

[0030] Multiple test signals can be simultaneously fed into the first several terminals. Likewise, multiple measurement signals can be acquired simultaneously. By identifying the test signals based on their different phases and / or amplitudes of specific harmonics, the multiple measurement signals acquired at the second terminal of the electrical system can be unambiguously assigned to the corresponding test signals, even if the test signals are routed through the electrical system simultaneously. Appropriate test cabling for feeding in the test signals and acquiring the measurement signals can therefore be installed and the wiring checked in a single step without altering the test cabling. This allows for rapid wiring testing. Wiring errors can be avoided because the test cabling does not need to be changed to check the wiring of all circuits and / or phases.

[0031] According to one embodiment, the first harmonic, i.e., the fundamental frequency, has a frequency that is different from the mains frequency or nominal frequency of the electrical system. The first harmonic can, for example, have a frequency in the range of 50 to 60 Hz, particularly a frequency in the range of 51 to 55 Hz, such as 52.6 Hz. By ensuring that the first harmonic of the test signals is different from the mains frequency of the electrical system, interference from other operating system components can be avoided. Operating system components typically generate interference signals at the mains frequency, i.e., at 50 Hz or 60 Hz, as well as interference signals with higher harmonics.If the fundamental frequency and higher harmonics of the test signals deviate from the mains frequency and the corresponding higher harmonics, the interference signals from other operating components can be easily detected and filtered out in the measurement signals. Since the fundamental frequency does not deviate significantly from the nominal frequency of the electrical system, the test signals are suitable for transmission via the electrical system, for example, via current or voltage transformers with transformers and / or capacitors.

[0032] In one embodiment, the amplitude of an nth harmonic of the higher harmonics, where the phase and / or amplitude is not used for characterization, has an amplitude factor of 1 / n 2< relative to the amplitude of the fundamental frequency. For example, the second and third harmonics described above can have a corresponding amplitude factor. Such amplitude factors can be used to achieve the asymmetrical waveform in the time domain. Waveforms that represent the first to third harmonics with an amplitude factor of 1 / n 2< These signals, for example, exhibit a sawtooth-like waveform with a steep rising edge and a shallow falling edge, resulting in an asymmetrical time-domain signal. Furthermore, the test signals generated in this way essentially have no DC component on average, thus preventing saturation of current or voltage transformers in the electrical system. The sawtooth-like waveform is essentially retained even when at least one higher harmonic with a modified amplitude and / or phase is superimposed, provided the amplitude is on the order of 1 / n 2< is, for example, 1.5 / n 2< or 0,5 / n 2< .

[0033] According to one embodiment, the assignments are determined by measuring the amplitudes and phases of spectral components for frequencies of the harmonics in the measurement signals. The amplitudes and phases of the spectral components are then compared with amplitude thresholds or phase thresholds. The amplitude thresholds can be set as a function of the amplitude of a fundamental frequency. The amplitude and / or phase of the fundamental frequency can be determined from the measurement signal.

[0034] In one embodiment, the at least one higher harmonic comprises the fourth and fifth harmonics. The fourth harmonic has an amplitude factor of 1.35 / 16, 1 / 16, or 0.65 / 16, and the fifth harmonic has an amplitude factor of 1.5 / 25, 1 / 25, or 0.5 / 25 relative to the amplitude of the fundamental frequency. As previously discussed, the amplitude of any of the remaining nth higher harmonics of the specified harmonics may have an amplitude factor of 1 / n² relative to the amplitude of the fundamental frequency.

[0035] The fourth harmonic can, for example, have a phase shift of +30°, 0°, or -30°, and the fifth harmonic a phase shift of +30°, 0°, or -30° relative to a phase of the fundamental frequency. In other examples, the phase shift of the fourth or fifth harmonic can, for example, be +20°, 0°, or -20° relative to a phase of the fundamental frequency. The phase shift can, for example, be selected in the range of + / -90°, preferably in the range of + / -45°, and more preferably in the range of + / -30° relative to a phase of the fundamental frequency.

[0036] According to a further embodiment, the method also includes determining the polarities of the acquired measurement signals in order to check the wiring of the electrical system based on the determined polarities. In particular, the asymmetrical waveform of the test signals in the time domain can enable a simple and reliable determination of the polarity. For example, if the wiring of a transformer is faulty, such as if connections on one side of the transformer have been reversed, the measurement signal may have a polarity opposite to that of the corresponding test signal. With an asymmetrical waveform in the time domain, the opposite polarity can be easily identified. For example, if the test signal has a steep rising edge and a shallow falling edge, a measurement signal with the opposite polarity will have a shallow rising edge and a steep falling edge.A corresponding wiring fault can thus be detected.

[0037] To determine the polarity of the acquired measurement signals, a derivative of each signal can be calculated, and a reference signal can be generated by comparing this derivative to a threshold value. The reference signal might, for example, have a positive value for areas of the derivative with a positive slope above the threshold and a negative value of the same magnitude for areas of the derivative with a negative slope above the threshold. If the mean value of the reference signal is then determined, for example, as a moving average or over one period of the fundamental frequency of the test signal, the polarity of the measured signal can be determined as a function of the mean value of the reference signal.

[0038] Alternatively or additionally, determining the polarity of the acquired measurement signals for a given signal can involve determining a correlation coefficient, in particular a correlation factor, depending on the signal and its asymmetric waveform in the time domain. The polarity of the respective signal can be determined based on the correlation factor. If the polarity is the same, the correlation factor is positive and, for example, has a value close to 1. If the polarity is opposite, the correlation factor is negative and, for example, has a value close to -1.

[0039] A test device according to the invention for testing the wiring of an electrical system with multiple circuits comprises a test signal generation device and a power supply device. The test signal generation device is configured to generate multiple test signals. Each of the multiple test signals has a combination of harmonics with at least one higher harmonic. The amplitude and / or phase of the at least one higher harmonic differ among the multiple test signals. The power supply device is configured to feed the multiple test signals into multiple first terminals at a first location in the electrical system. The multiple first terminals are assigned to the multiple circuits of the electrical system. A different test signal from the multiple test signals is fed into each first terminal of the multiple first terminals.Since the test signals are based on different combinations of harmonics, the test signals fed into the first of the several first connections are different.

[0040] In some embodiments, the test device may further comprise a detection device and a processing device. The detection device is configured to detect multiple measurement signals at several secondary terminals at a second location in the electrical installation. These secondary terminals are assigned to multiple circuits. The first and second locations are distinct parts of the electrical installation. The multiple circuits may, for example, comprise multiple phases of the electrical installation. For instance, the first location may be on one side of a transformer in the electrical installation, and the second location on the other side. The detection device is configured to determine the correspondence between each of the first terminals of the multiple first terminals and each of the second terminals of the multiple second terminals based on the input test signals and the detected measurement signals.

[0041] The test signal generation device can comprise several single-phase devices, each generating only one test signal. These single-phase devices can be configured to each generate one of several test signals based on different amplitudes and / or phases of at least one higher harmonic. Alternatively or additionally, the test signal generation device can comprise several multi-phase devices, for example, two three-phase devices, to generate six test signals, enabling the simultaneous testing of six circuits or phases. The devices can be interconnected to achieve the same phase for the fundamental frequencies, simplifying the detection of superimposed signals. However, individual phase detection also functions when the devices are not interconnected.

[0042] The test device can be designed in particular to carry out the previously described method or one of its embodiments and therefore also includes the advantages previously described in connection with the method. KURZE BESCHREIBUNG DER FIGUREN

[0043] The invention is explained in more detail below with reference to the drawings and embodiments. In the drawings, identical reference numerals denote identical elements. Fig. 1 Figure 1 schematically shows a test device for testing the wiring of an electrical system with multiple phases according to one embodiment. Fig. 2 shows a method for testing the wiring of an electrical system with multiple phases according to one embodiment. Fig. 3 schematically shows several test signals according to an embodiment, which have a time-domain asymmetrical signal shape and a combination of higher harmonics. Fig. 4 schematically shows derivations of the several test signals of the Fig. 3 after time. Fig. 5 schematically shows a comparison signal which is formed by comparing a derivative of a test signal with a threshold value. Fig. 6 Figure 1 schematically shows another test device for testing the wiring of an electrical system with multiple circuits according to one embodiment. DETAILED DESCRIPTION OF EXAMPLES OF EXECUTION

[0044] The present invention is explained in more detail below with reference to embodiments and the figures. In the figures, identical reference numerals denote identical or similar elements. The figures are schematic representations of various embodiments of the invention. The elements depicted in the figures are not necessarily shown to scale. Rather, the various elements shown in the figures are represented in such a way that their function and purpose are understandable to a person skilled in the art.

[0045] The connections and couplings between functional units and elements depicted in the figures can be implemented as direct or indirect connections or couplings. A connection or coupling can be implemented wired or wirelessly.

[0046] Fig. 1 Figure 1 schematically shows a section of an electrical installation 100, to which a test device 150 is connected for testing the wiring of the electrical installation 100. The electrical installation 100 is a multi-phase electrical installation. Many power engineering systems use a three-phase alternating current system. In the Fig. 1 In the example shown, the electrical installation 100 is a three-phase installation. The electrical installation 100 can, for example, comprise a high-voltage installation or a part thereof. The electrical installation 100 includes an electrical component 110, which has two three-phase connections. The electrical component 110 can, for example, include a three-phase circuit breaker, a three-phase transformer, several transformers, capacitors, current and voltage transformers, or intermediate transformers. On a first side 112, the electrical component 110 has connections that are connected to phase conductors 120 to 122 of a three-phase power line 125. On a second side 114, the electrical component 110 has connections that are connected to phase conductors 130 to 132 of a second three-phase power line 135.The electrical component 110 may have additional connections, for example, for grounding or for a neutral conductor of a three-phase system in a star connection; however, these additional connections are not shown for clarity. Wiring errors can occur during the installation of the electrical component 110. For example, two live conductors, such as live conductors 120 and 121, may be connected incorrectly on the first side 112 of the electrical component 110. Therefore, after installation or repair of the electrical system 100, it may be necessary to check the wiring.

[0047] To check the wiring, the following can be done: Fig. 1 The test device 150 shown is electrically coupled to both sides 112, 114 of the electrical component 110.

[0048] The test device 150 comprises a test signal generation device 152, which generates several test signals. For example, to test the three-phase electrical system 100, the test signal generation device 152 generates three test signals 160 to 162. The test device 150 further comprises a feed device 154, with which the test signals 160 to 162 are fed via corresponding lines 170 to 172 at a first point 141 of the electrical system 100 into several first terminals 142 to 144. The feed device 154 can, for example, adapt the test signals from the test signal generation device 152 to a nominal range of the electrical component 110 and make them available at three terminals. A cable assembly comprising the three lines 170 to 172 can be connected to the three terminals of the feed device 154.At the first point 141, for example, a relatively easily accessible distribution point before the electrical component 110, line 170 can be connected to the phase conductor 120, so that a first test signal is fed into the phase conductor 120. Line 171 can be connected to the phase conductor 121 to feed a second test signal into the phase conductor 121. Line 172 can be connected to the phase conductor 122 to feed a third test signal into the phase conductor 122. Thus, a corresponding test signal is fed into each phase on the first side 112 of the component 110.

[0049] The test device 150 can further comprise a detection device 156, which is connected via corresponding lines 180 to 182 to the three outer conductors 130 to 132, which are connected to the second side 114 of component 110, at a second location 145 of the electrical installation 100 via corresponding second connections 146 to 148. The second location 145 can be situated at an easily accessible distribution point of the electrical installation 100. Thus, a corresponding measurement signal can be detected for each phase on the second side 114.

[0050] The test device 150 can further comprise a processing device 158. The processing device 158 includes, for example, an electronic control unit, such as a microprocessor control unit, which can, for example, execute a computer program. The processing device 158 can be coupled to the test signal generation device 152 and the detection device 156 in order to control them in a coordinated manner, as will be described in detail below. In other examples, the processing device 158 is not connected to the test signal generation device 152, and the test signal generation device 152 generates the test signals independently of any control by the processing device 158.It is therefore clear that the test signal generation device 152, the feed device 154, the detection device 156, and the processing device 158 do not necessarily have to be housed in the same enclosure or unit, but can comprise spatially independent units with their own enclosures. For example, the test signal generation device 152, together with the feed device 154, can form a unit that can be operated and installed independently of another unit comprising the detection device 156 and the processing device 158. This allows the test device 150 to be used even in large electrical installations where the first location 141 is spatially far from the second location 145, without requiring correspondingly long cables 170 to 172 or 180 to 182.

[0051] The operating principle of the test device 150 is described below with reference to the Figuren 2 bis 5 will be described in detail. Fig. 2 Figure 200 shows a method 200 with method steps 202 to 214, which can be performed by the test device 150 to test the wiring of the electrical system 100. In particular, steps 206 to 214 can be optional or replaced by other steps based on the test signals generated and fed in in steps 202 and 204. At least some of the steps described in Figure 200 are optional. Fig. 2 The processing steps shown can be carried out in particular with the processing device 158, for example by means of a computer program which is executed by the processing device 158.

[0052] In step 202, several test signals are generated. Specifically, a separate test signal is generated for each phase. P p (t) generated, which exhibits a signal shape asymmetrical in the time domain and a combination of predefined harmonics with at least one higher harmonic. The index p designates the phase for which the test signal P p (t) The multiple test signals differ from each other in that their amplitude and / or phase (hereinafter also referred to as phase) differ at least at one higher harmonic. For example, the test signals can be based on a common signal. P(t) based on a signal shape that is asymmetrical in the time domain. The signal shape of the common signal. P(t) It can approximate a sawtooth waveform. For example, sine waves with different amplitudes and frequencies can be used, which, via Fourier synthesis, approximate the sawtooth waveform. For example, the common signal could be... P(t) a signal according to the following equation can be used: P t = A ∑ n = 1 k 1 n 2 sin 2 πnf g t

[0053] Here, A represents the amplitude of the entire signal, k the number of harmonics used, and fg the fundamental frequency of the signal. The term 1 n 2 It weights the individual sine functions to approximate the sawtooth signal shape in total.

[0054] For example, a signal can be equipped with A = 1, k = 3 and fg = 52.6 Hz. In other examples, A can also be chosen such that the RMS value of the signal is approximately 1. For example, A can be chosen to be approximately 0.962.

[0055] Each of the test signals P p (t) The test signals also include at least one higher harmonic, where the amplitude and / or phase of this higher harmonic differ between the various test signals. In the example described below, the higher harmonic includes two higher harmonics, namely the fourth and fifth harmonics. In other examples, additional or different harmonics can be used to distinguish the various test signals. In principle, however, a single higher harmonic is sufficient to differentiate the various test signals. The advantage of using multiple higher harmonics is that it improves the differentiation of the test signals, for example, if the test signals are disturbed or noisy. The different amplitudes and / or phases in the higher harmonic provide a kind of encoding for the test signals.This coding can, for example, represent phase information in a multi-phase electrical system, indicating which phase of the electrical system 100 the test signal is assigned to.

[0056] To encode the phase information into the sawtooth-like signal, the amplitude and phase of, for example, two higher harmonics are slightly modified. For instance, the fourth and fifth harmonics are altered to encode this phase information, while the fundamental frequency and the second and third harmonics remain unchanged. In total, only five harmonics are used to limit the bandwidth of the test signal. The following equation shows the definition of the modified test signal. y(t) with five harmonics (k=5). y t = ∑ n = 1 k a n 1 n 2 sin 2 πnf g t + φ n

[0057] The amplitude variations and phase variations used φ n can be achieved by introducing an amplitude modifier A[n] and a phase modifier P[n] for the n-te Harmonics are represented. Both can, for example, have three specific values, which are denoted, for example, by -1, 0, and +1. The mappings used to a n and φ n The equation above is shown in Table 1 below. Table 1: Amplitude and phase variation Parameter Koeffizienten n = 1 n = 2 n = 3 n = 4 n = 5 an 1 1 1 A[4] = 1: 1,35 A[5] = 1: 1,50 A[4] = 0: 1,00 A[5] = 0: 1,00 A[4] = -1: 0,65 A[5] = -1: 0,50 φ n 0 0 0 P[4] = 1: 0,5 rad P[5] = 1: 0,5 rad P[4] = 0: 0,0 rad P[5] = 0: 0,0 rad P[4] = -1: -0,5 rad P[5] = -1: -0,5 rad

[0058] It is clear that amplitude and phase variations can also be represented in other ways, for example, directly by the corresponding amplitude factors and phase angles. It is also clear that a number other than three values ​​can be used for variation, for example, two or more than three. The phase angles are given in radians in Table 1. 0.5 rad corresponds to approximately 28.6°. In other examples, other phase angles can be used for variation, for example, + / -20° or + / -40°.

[0059] Due to the relatively small amplitudes of the fourth and / or fifth harmonics, the asymmetrical signal shape changes only slightly. Lower harmonics, such as the second and third, are less suitable for encoding phase information because they significantly affect the signal's asymmetry in the time domain and could therefore complicate detection, especially of polarity. Even higher harmonics, particularly the seventh or higher, are also less suitable because current and voltage converters typically attenuate high frequencies much more strongly, thus potentially impairing transmission and detection.

[0060] This scheme of amplitude and phase variation, with three fixed values ​​for the two amplitude and two phase modifiers, allows the encoding of 3² + 2 ≤ 81 different codewords. It is clear that alternatively, only one amplitude variation or only one phase variation can be used. For example, with only one phase variation, the amplitude modifiers A[n] the value 0, so the amplitude variation has the value 1.

[0061] To increase the robustness of the coding, only five of the 81 possible codewords are used, designated below as CWS, CW1, CW2, CW3, and CW4. CWS represents an unmodified sawtooth-like test signal. CW1–CW4 can be used to identify four different phases or circuits of an electrical installation. The codeword CW4 for the fourth phase is generally not needed in three-phase installations and networks, but is discussed here for the sake of symmetry.

[0062] Table 2 below shows an example of the assignment of codewords to the amplitude and phase modifiers A and P.

[0063] All the different codewords differ from each other in at least two modifiers. The sum of the differences between the amplitude and phase modifiers A and P for each combination of codewords used can be calculated to obtain the Hamming distance of the codewords. Table 3 below shows the resulting Hamming distances.

[0064] There is a minimum spacing of 4 between all codewords used, which allows a single error, such as an incorrectly detected amplitude or phase value, to be detected and corrected. Additionally, two incorrectly detected modifiers can be detected as errors, but not corrected. In the case of a single incorrect symbol, the next valid codeword with a Hamming spacing of 1 is used. If the spacing is greater, it is considered an incorrect codeword.

[0065] In this context, this would mean that the phase information of a highly distorted signal cannot be correctly decoded, but it can still be recognized as a valid polarity check signal.

[0066] The method uses a signal with a fundamental frequency of 52.6 Hz. Limiting the signal to the fifth harmonic results in a maximum frequency of 263 Hz. Since the encoding used is static, there are no higher frequencies due to modulation. Conventional current and voltage converters can transmit these relatively low frequencies without significant attenuation or phase shifts.

[0067] Fig. 3 Shows signal waveforms of the test signals for phases 1, 2, and 3 based on the codings CW1, CW2, and CW3, as well as the unchanged test signal based on the coding CWS. As can be seen from the Fig. 3 As can be seen, the asymmetrical signal shape in the time domain is clearly recognizable in all test signals, meaning that the signals all essentially have a relatively steep rising edge and a relatively flat falling edge compared to the rising edge.

[0068] In step 204, the generated test signals 160 to 162 for phases 1, 2, and 3 are fed into the outer conductors 120 to 122 at the first terminal 141 via the first terminals 142 to 144. The test signals 160 to 162 can be fed in simultaneously. The test signals fed in thus pass through the electrical component 110, which may include one or more transformers, capacitors, or other electrotechnical equipment, such as circuit breakers. At the second terminal 114, the electrical component 110 outputs signals on the three outer conductors 130 to 132 based on the fed-in test signals. With a correctly connected electrical component 110, for example, the test signal fed in on outer conductor 120 is expected to be output essentially on outer conductor 130, for example, with a changed voltage in the case of a transformer.The signal shape would, however, be expected to remain essentially unchanged. Similarly, with correctly connected electrical component 110, for example, the signal fed into the outer conductor 121 is expected to be output essentially on the outer conductor 131, and the signal fed into the outer conductor 122 is expected to be output essentially on the outer conductor 132.

[0069] In the case of faulty wiring, where the outer conductors 121 and 122 have been connected in reverse, the signal fed into outer conductor 121 is output to outer conductor 132 and the signal fed into outer conductor 122 is output to outer conductor 131.

[0070] In step 206, several measurement signals are acquired at the second position 145. These signals can be acquired simultaneously or sequentially. The acquired measurement signals can optionally be pre-treated in the acquisition device 156, for example, by filtering. For instance, the signals can be pre-processed with analog and / or digital filters to suppress interference caused by resistive, inductive, or capacitive coupling, such as a resistive voltage drop due to current flow through a common return conductor. Such interference can, for example, affect the outer conductors 120 to 122 and 130 to 132 from adjacent operating systems. Furthermore, notch filters for mains frequencies, such as 50 Hz, 60 Hz, or 16.7 Hz, or a combination thereof, can be used to filter out interference from adjacent systems.Additional notch filters can be used to filter the measurement signals for higher harmonics of the mains frequency. Alternatively or additionally, low-pass filters can be applied to remove higher harmonics and other interference from the measurement signals. The cutoff frequency can be higher than the frequency of the highest harmonic used in the test signals. Finally, a high-pass filter can be applied to remove low-frequency interference from the measurement signals, with the cutoff frequency being lower than the fundamental frequency of the test signals. Preprocessing the measurement signals can increase the reliability of the wiring verification and reduce susceptibility to interference from adjacent operating systems.

[0071] Step 208 involves determining the relationship between test signals and measurement signals. In other words, step 208 identifies the test signals within the measurement signals. This identification can include determining the amplitudes and phases of spectral components for frequencies of the specified harmonics, particularly the higher harmonics used for encoding. The amplitudes and phases of these spectral components can then be compared with amplitude thresholds or phase thresholds. The amplitude thresholds can be set based on the amplitude of a fundamental frequency of the time-domain asymmetrical waveform.

[0072] If the fundamental frequency fg was chosen appropriately as described above, for example to be 52.6 Hz, then there will be no overlap with the mains frequency or higher harmonics of the mains frequency.

[0073] As previously described, the information for identifying a phase is robustly encoded in sawtooth-like test signals. This allows verification of the correct polarity and phase assignment without the need for a common reference and without dependence on the signal amplitude.

[0074] Decoding modified sawtooth-like test signals from the acquired measurement signals can be carried out, for example, in the following steps.

[0075] As a first step, the received measurement signal can be filtered with a low-pass filter to limit its bandwidth to, for example, 263 Hz, i.e., to the frequency that was used as the highest frequency in generating the test signals. In the example above, a fundamental frequency of 52.6 Hz was used, so the highest frequency of the fifth harmonic is 263 Hz. For example, an eighth-order Butterworth low-pass filter can be used as a pre-filter for this purpose.

[0076] In a second step, the measurement signal is analyzed for the frequency components of the five harmonics used in this example. The period of each of these signals of interest is known (for example, 52.6 Hz and integer multiples thereof), and therefore, a Goertzel algorithm, for instance, can be used to perform a discrete Fourier transform (DFT). The Goertzel algorithm provides the amplitude and phase and is applied to all frequencies of interest, for example, the five frequencies of the five harmonics used. Longer integration intervals of, for example, 20 periods can be used to further suppress noise and interference by exploiting an averaging effect.

[0077] Finally, the phase information is decoded. The amplitude of the fourth and fifth harmonics is normalized based on the average amplitude of the first three harmonics. A discriminator then checks the harmonics for amplitude and phase deviations from the values ​​specified in Table 1 and assigns a value of +1 (if > 150% of the nominal value), -1 (if < 50% of the nominal value), or 0 (if in between) to the detected amplitude and phase modifiers, assigning them to one of the 81 possible codewords. The Hamming distance between the received codeword and all five valid codewords can then be calculated. If a codeword with a distance of 0 or 1 is found, it is accepted by the detector as a valid codeword. Based on the phase information thus determined, it can be ascertained which test signal is contained within which measurement signal and therefore on which phase conductor an input test signal is output.

[0078] If a Hamming distance of two or more is reported, it can be used as a polarity test signal, but phase information cannot be reliably derived from it. However, it does at least indicate that the test signal is significantly disturbed, which can be communicated to an operator.

[0079] Based on the mapping between test signals and measurement signals determined in step 208, it can be easily established whether the expected test signals have been detected on the corresponding outer conductors 130 to 132. If the mappings are not as expected, a wiring fault can be identified.

[0080] In step 210, the polarities of the measurement signals, which were acquired at the second position 145, are determined. The polarity detection is based on the asymmetrical signal shape in the time domain.

[0081] For example, polarity detection can be performed as follows: The amplitudes of the harmonics are compared to the detected fundamental frequency. If the second and third harmonics are within ±50% of the expected relative amplitude and the phase is within ±30° (0.5 rad) of the expected values, this is considered a valid sawtooth-like signal, i.e., a sawtooth-like signal with correct polarity. With correct polarity, all harmonics have essentially the same phase as the fundamental, apart from the set phase variation. In the case of an inverted signal, every second harmonic is inverted in the frequency domain, resulting in a phase shift of 180°. This is considerably larger than the phase variation.Therefore, a phase value of 0° and 180° (+ / - 30°) for the second harmonic, but only 0° (+ / - 30°) for the third harmonic, is considered a sawtooth-like signal with correct polarity. A polarity of approximately 0° is considered correct, while one of approximately 180° is considered incorrect (inverted).

[0082] In another example, polarity can be assessed as follows. For the measurement signals, which can be pre-treated as described above, respective time-domain derivatives are calculated. A given derivative can be determined, for example, by a discrete-time numerical derivative using differences between temporally recorded signal levels, or implicitly through appropriately adapted filter structures, such as by using an analog operational amplifier as a differentiator or in digital filter structures. Fig. 4 shows resulting derivatives dM p (t) / dt for the measurement signals M p (t) for phases p = 1, 2, and 3, which are obtained in response to the test signals for phases 1, 2, and 3 based on the codes CW1, CW2, and CW3 (with correct wiring and polarity). A corresponding auxiliary signal can be provided for each of the derivatives. Q p (t) be formed, for example according to the following regulation: Q p t = 1 , wenn M p t dt > δ − 1 , wenn M p t dt < − δ 0 , sonst

[0083] Here, δ is the threshold value used to suppress noise and other unwanted interference. Fig. 5 shows the auxiliary signal as an example. Q 1 (t) for the test signal for phase 1. Based on the auxiliary signal Q p (t) A corresponding average will be calculated. Q p ( tThe average value is calculated over a specific period. This average can be calculated, for example, over a discrete time period, such as the period T of the fundamental frequency of the test signals, or continuously using a low-pass filter. If this average exceeds a defined positive threshold, a positive polarity is indicated (short rising edge and long falling edge). If the average falls below a defined negative threshold, a negative polarity is indicated (long rising edge and short falling edge). A polarity reversal, which can occur, for example, due to faulty wiring, can thus be easily determined for each phase.

[0084] In step 212, the phase assignments and polarities determined in this way can, for example, be displayed on a display device for a user.

[0085] For example, a first test signal for phase 1 can be output on line 170, a second test signal for phase 2 on line 171, and a third test signal for phase 3 on line 172. With correct wiring of the electrical system 100, the test device 150 indicates for line 180 that the first test signal has been detected, for line 181 that the second test signal has been detected, and for line 182 that the third test signal has been detected. Furthermore, the test device 150 can indicate that the test signals were output and detected with positive polarity. Wiring errors, such as reversed phase conductors or incorrect wiring that leads to polarity inversion, for example at a transformer, can be identified by an operator based on the outputs.

[0086] Alternatively or additionally, in step 214 the detected phase assignments can be compared with target assignments and / or the detected polarities with target polarities, and a warning can be automatically issued if a deviation between the detected state and the target state is found.

[0087] The electrical installation 100 may have further connections, for example, additional three-phase connections, the wiring of which can be checked in the same manner as described above. These connections may, for example, relate to auxiliary circuits or control circuits, which, depending on the type of circuit, can also be tested using the above procedure.

[0088] When testing multiple circuits or phases, these can share a common neutral conductor (N for L1, L2, and L3) or be completely separate circuits (L1+N1, L2+N2, L3+N3). Various wiring errors are possible here as well and can be detected using this method. Wiring errors can result in multiple ground connections. Using a current clamp, for example, the current through the ground connection can be measured as one of several test signals. The described method allows the identification of which test signals were detected in the ground connection, thus distinguishing between desired and undesired ground connections.

[0089] Fig. 6 Figure 1 schematically shows a section of another electrical installation 600, to which a test device 650 is connected for testing the wiring of the electrical installation 600. The electrical installation 600 comprises several circuits, which can be assigned to one or more phases. In the Fig. 6 In the example shown, the electrical installation 600 comprises two circuits 601 and 602, which are essentially separate from each other. However, circuits 601 and 602 can also be assigned to one phase of a multiphase system, i.e., the same phase of the multiphase system, or to several different phases of a multiphase system, or be connected to each other via their neutral conductors. In other examples, the electrical installation 600 can comprise more than two circuits. For example, the electrical installation 600 can comprise a high-voltage system or part thereof. Each of the circuits 601 and 602 can comprise one or more electrical components, such as current or voltage transformers 610, 630, secondary wiring 612, 632, matching transformers, test plugs 614-619, 634-639, test switches 611, 631, meters, and / or protective devices, such as relays 613, 633.

[0090] After installation or repair of the electrical system 600, it may be necessary to check the wiring. To check the wiring, the following can be used: Fig. 6 The test device 650 shown is electrically coupled to both circuits 601 and 602.

[0091] The test device 650 comprises several test signal generation devices, which generate several test signals. In Fig. 6 Two test signal generation devices 652 and 654 for generating two test signals are shown. The multiple test signals can also be generated by a single test signal generation device. Each of the test signal generation devices 652 and 654 is associated with a corresponding (not shown) feed-in device, with which the test signals are fed into the electrical system 600 via corresponding lines at corresponding feed-in points. The feed-in devices can, for example, adapt the test signals from the test signal generation devices 652 and 654 to a nominal range required at the corresponding feed-in point. In the in Fig. 6 In the example shown, the test signal from the test signal generation device 652 can be fed, for example, into test plugs 616, 617 on a secondary side of a transformer 610, such as a current transformer or voltage transformer. Alternatively, the test signal from the test signal generation device 652 can also be fed into test plugs 614, 615 on a primary side of the transformer 610, as shown by the dashed lines. By feeding the signal into the primary side, the polarity and wiring of the transformer 610 can also be checked. When feeding the signal into the primary side, correspondingly higher currents may be required for current transformers and correspondingly higher voltages for voltage transformers. Similarly, the test signal from the test signal generation device 654 can be fed, for example, into test plugs 636, 637 on a secondary side of a transformer 630.Alternatively, the test signal from the test signal generation device 654 can also be fed into test plugs 634, 635 on a primary side of the converter 630, as shown by the dashed lines, in order to additionally check the polarity and wiring of the converter 630.

[0092] The test device 650 also includes several detection devices for capturing measurement signals. In the example of Fig. 6 The test device 650 comprises two detection devices 651 and 653, which are connected to the first and second circuits 601 and 602, respectively, via corresponding lines. For example, detection device 651 can be connected to test plugs 618 and 619 on the test switch 611 to detect a voltage at the test switch 611 as a measurement signal. As indicated by the dashed lines, detection device 651 can alternatively be connected to test plugs 616 and 617 to detect a voltage on the secondary side of the transformer 610 or to a current clamp 620 to detect a current through the wiring 612. Detection device 653 can be connected to the second circuit 602 in the same manner. As shown in Fig. 6 As shown, the sensing device 653 can be connected to the test switch 631 using the test plugs 638, 639 to detect a voltage at the test switch 631 as a measurement signal. Alternatively, the sensing device 653 can be connected to test plugs 636, 637 to detect a voltage on the secondary side of the converter 630 or to a current clamp 640 to detect a current through the wiring 632.

[0093] The test device 650 further comprises a processing device 655, which is located in the Fig. 6 The processing device 655 is shown as a separate component. In other examples, it can also be integrated with one of the test signal generation devices 652, 654 or the detection devices 651, 653. The processing device 655 includes, for example, an electronic control unit, such as a microprocessor control unit, which can, for example, execute a computer program. The processing device 655 can be coupled with the test signal generation devices 652, 654 and the detection devices 651, 653 to control them in a coordinated manner, as will be described in detail below. In other examples, the processing device is not connected to the test signal generation devices 652, 654, and the test signal generation devices 652, 654 generate the test signals independently of control by the processing device 655.The test signal generation devices 652, 654, the detection devices 651, 653, and the processing device 655 need not be housed in the same enclosure or unit, but can comprise spatially independent units with their own enclosures. For example, the test signal generation devices 652, 654 can each form a unit that can be operated and installed independently. Another unit can comprise the detection devices 651, 653, and the processing device 655 and be coupled to the test signal generation devices 652, 654. This allows the test device 650 to be used even in large electrical installations where the power supply points are located far from the measuring points, without requiring correspondingly long cables between the test signal generation devices 652, 654, and the respective power supply points.

[0094] The operating principle of the test device 650 essentially corresponds to that previously described with reference to the Figuren 1 bis 5 The detailed operating procedure of test device 150 is described. As previously described, this can be done in Fig. 2 The procedures shown 200 are carried out by the test device 650 to test the wiring of the electrical system 600.

[0095] In step 202, two test signals are generated in this case. A separate test signal is generated for each circuit 601, 602. P p (t) This signal is generated and exhibits a time-domain asymmetric waveform and a combination of predefined harmonics with at least one higher harmonic. The index p denotes the circuit for which the test signal is generated. P p (t) is planned, for example, p=1for circuit 601 and p=2 for circuit 602. The two test signals differ in that their phase angles (hereinafter also referred to as phase) differ at least one higher harmonic. For example, the test signals can be based on a common signal. P(t) based on a signal shape that is asymmetrical in the time domain. The signal shape of the common signal. P(t) It can approximate a sawtooth waveform. For example, sine waves with different amplitudes and frequencies can be used, which, via Fourier synthesis, approximate the sawtooth waveform. For example, the common signal could be... P(t) a signal according to the following equation can be used: P t = A ∑ n = 1 k 1 n 2 sin 2 πnf g t

[0096] Here, A represents the amplitude of the entire signal, k the number of harmonics used, and fg the fundamental frequency of the signal. The term 1 n 2 It weights the individual sine functions to approximate the sawtooth signal shape in total.

[0097] For example, a signal can be equipped with A = 1, k = 3 and fg = 52.6 Hz. In other examples, A can also be chosen such that the RMS value of the signal is approximately 1.

[0098] Each of the two test signals P p (t) The test signals also include at least one higher harmonic, the phases of which differ between the various test signals. In the example described below, the at least one higher harmonic includes only one higher harmonic, namely the fourth harmonic. The test signals are thus assigned a code. This code can, for example, represent circuit information in electrical system 600 with the two circuits 601 and 602, indicating which circuit the test signal is assigned to.

[0099] To encode the circuit information into the sawtooth-like signal, the phase of the fourth harmonic is slightly modified, while the fundamental frequency and the second and third harmonics remain unchanged. Only four harmonics are used in total to limit the bandwidth of the test signal. The following equation defines the modified test signal. y(t) with four harmonics (k=4). y t = ∑ n = 1 k 1 n 2 sin 2 πnf g t + φ n

[0100] The phase variations used can be represented by introducing a phase modifier P[4] for the fourth harmonic. This can, for example, have two specific values, which are denoted, for instance, by -1 and +1. The mapping used to φ n For example, in the equation above: φ 1 = 0 , φ 2 = 0 , φ 3 = 0 , φ 4 = 0.5 rad for P[4] = 1 and φ 4 = -0.5 rad for P[4] = -1.

[0101] Similar to the example of the Figur 1 As described, each value of the phase modifier P[4] represents a codeword, e.g. P[4] = 1 is codeword CW1 and P[4] = -1 is codeword CW2.

[0102] In step 204, the generated test signals are fed into circuits 601 and 602 as described previously. The test signals can be fed in simultaneously. These signals then pass through the electrical components, which may include one or more transformers, capacitors, or other electrotechnical devices such as circuit breakers or test switches. Output signals are generated at the measuring points described above based on the fed-in test signals. With correctly connected electrical components, the test signal fed into circuit 601 is expected to be output primarily at test plugs 618 and 619 of test switch 611, for example, with a different voltage if fed in at test plugs 614 and 615. However, the signal waveform would be expected to remain essentially unchanged.Similarly, with correctly connected electrical components, for example, it is expected that the signal fed into circuit 602 will be essentially output at the test plugs 638, 639 of the test switch 631.

[0103] In the case of faulty wiring, where, for example, the wires of the first circuit 601 and the wires of the second circuit 602 have been connected in reverse, the signal fed into the first circuit 601 could be present in the second circuit 602 and / or the signal fed into the second circuit 602 could be present in the first circuit 601.

[0104] In step 206, several measurement signals are acquired, for example, as previously described at test switches 611 and 631. The multiple measurement signals can be acquired simultaneously or sequentially. The acquired measurement signals can optionally be pre-processed in the acquisition devices 651 and 653, for example, by filtering.

[0105] In step 208, a mapping between test signals and measurement signals is determined. In other words, step 208 identifies the test signals within the measurement signals. The identification of the individual test signals within the measurement signals can be achieved using filters or a discrete Fourier transform for the fourth harmonic, as previously described in the example of... Figur 1 described.

[0106] Based on the mapping between test signals and measurement signals determined in step 208, it can be easily verified whether the expected test signals have been detected at the corresponding test plugs 618, 619, 638, and 639. If the mappings are not as expected, a wiring fault can be identified.

[0107] In step 210, the polarities of the measurement signals acquired at test plugs 618, 619, 638, and 639 are determined. Polarity detection is based on the asymmetrical signal shape in the time domain, as previously described with reference to electrical system 150. Figur 1 was described.

[0108] In step 212, the circuit assignments and polarities determined in this way can, for example, be displayed on a display device for a user.

[0109] Alternatively or additionally, in step 214, the detected circuit assignments can be compared with target assignments and / or the detected polarities with target polarities. A warning can be automatically issued if a deviation between the detected state and the target state is found.

[0110] In summary, the various test signals described above enable a quick and reliable inspection of the electrical system's wiring. These test signals have a time-domain asymmetric waveform and consist of a combination of predefined harmonics with at least one higher harmonic. The amplitude and / or phase of this higher harmonic differs between the various test signals. Because the test signals are DC-free, no saturation effects occur in components such as transformers or capacitors, allowing for seamless transmission via converters. Furthermore, the test signals enable the detection of polarity errors and the unambiguous differentiation of individual phases.The threshold values ​​used to identify the higher harmonics can be chosen relative to the fundamental frequency and are therefore not dependent on the absolute amplitude of the signals. This method thus also works with partial signals that can occur, for example, due to current sharing or unwanted ground connections.

[0111] The individual different test signals, as well as linear combinations thereof, exhibit the same asymmetrical properties in the time domain and can therefore be reliably assigned a polarity.

[0112] By using additional harmonics and / or different amplitudes, more than three phases can be distinguished. This allows, for example, the simultaneous differentiation of further phases, such as in 2 x 3 phase systems, or the use of an encoding with a Hamming distance greater than one to improve robustness against amplitude errors.

Claims

1. A method for testing wiring of an electrical installation having multiple circuits, characterized by: - generating (202) multiple test signals (160-162), wherein each of the multiple test signals (160-162) has a combination of predefined harmonics having at least one higher harmonic, wherein the amplitude and / or phase of the at least one higher harmonic of the multiple test signals (160-162) are different, and - injecting (204) the multiple test signals (160-162) into multiple first connections (142-144), which are assigned to the multiple circuits, at a first point (141) of the electrical installation (100), wherein a different test signal of the multiple test signals (160-162) is injected into each first connection of the multiple first connections (142-144).

2. The method according to Claim 1, wherein the multiple test signals (160-162) are injected simultaneously into the multiple first connections (142-144).

3. The method according to Claim 1 or Claim 2, wherein the at least one higher harmonic comprises fourth and / or fifth harmonics.

4. The method according to one of the preceding claims, wherein the combination or predefined harmonics comprises, in addition to a fundamental, at least second and / or third harmonics.

5. The method according to one of the preceding claims, wherein a fundamental of the predefined harmonics has a frequency not equal to a mains frequency of the electrical installation.

6. The method according to one of the preceding claims, wherein a fundamental of the predefined harmonics has a frequency in the range of 50 to 60 Hz, optionally a frequency in the range of 51 to 55 Hz, again optionally a frequency of 52.6 Hz.

7. The method according to one of the preceding claims, wherein the at least one higher harmonic comprises fourth and fifth harmonics, wherein the fourth harmonic has an amplitude factor of 1.35 / 16 or 1 / 16 or 0.65 / 16, and the fifth harmonic has an amplitude factor of 1.5 / 25 or 1 / 25 or 0.5 / 25 relative to an amplitude of a fundamental of the predefined harmonics, wherein an amplitude of one of the other nth higher harmonics of the predefined harmonics has an amplitude factor of 1 / n2 relative to an amplitude of the fundamental of the predefined harmonics.

8. The method according to one of the preceding claims, wherein the at least one higher harmonic comprises fourth and fifth harmonics, wherein the fourth harmonic has a phase offset of +30° or 0° or -30°, and the fifth harmonic has a phase offset of +30° or 0° or -30° relative to a phase of a fundamental of the predefined harmonics.

9. The method according to one of the preceding claims, furthermore comprising: - acquiring (206) multiple measurement signals at multiple second connections (146-148), which are assigned to the multiple circuits, at a second point (145) of the electrical installation (100).

10. The method according to Claim 9, furthermore comprising: - determining (208) assignments between in each case a first connection of the multiple first connections (142-144) and a second connection of the multiple second connections (146-148) on the basis of the injected test signals (160-162) and the acquired measurement signals.

11. The method according to Claim 10, wherein determining (208) assignments comprises: - determining amplitudes and phases of spectral components for frequencies of the predefined harmonics in the measurement signals, and - comparing the amplitudes and phases of the spectral components with amplitude threshold values or phase threshold values.

12. The method according to Claim 11, wherein the amplitude threshold values are set on the basis of an amplitude of a fundamental of the predefined harmonics.

13. The method according to one of Claims 10-12, furthermore comprising: - outputting the assignments between in each case a first connection of the multiple first connections and a second connection of the multiple second connections to a user, and / or - comparing the assignments between in each case a first connection of the multiple first connections and a second connection of the multiple second connections with predefined assignments between in each case a first connection of the multiple first connections and a second connection of the multiple second connections.

14. The method according to one of the preceding claims, wherein each of the multiple test signals (160-162) has a waveform that is asymmetric in the time domain.

15. The method according to Claim 9 and Claim 14, furthermore comprising: - determining (210) polarities of the acquired measurement signals in order to test the wiring of the electrical installation depending on the determined polarities.

16. The method according to Claim 15, wherein determining (210) polarities of the acquired measurement signals for a respective measurement signal of the acquired measurement signals comprises: - determining a derivative of a respective measurement signal, - generating a comparison signal by comparing the derivative with a threshold value, - determining an average of the comparison signal, and - determining the polarity of the respective measurement signal on the basis of the average of the comparison signal.

17. The method according to Claim 15, wherein determining (210) polarities of the acquired measurement signals for a respective measurement signal of the acquired measurement signals comprises: - determining a correlation factor on the basis of a respective measurement signal and the waveform that is asymmetric in the time domain, and - determining the polarity of the respective measurement signal on the basis of the correlation factor.

18. A test device for testing wiring of an electrical installation having multiple circuits, characterized by: - a test signal generation device (152) that is configured to generate multiple test signals (160-162), wherein each of the multiple test signals (160-162) has a combination of predefined harmonics having at least one higher harmonic, wherein the amplitude and / or phase of the at least one higher harmonic of the multiple test signals (160-162) are different, and - an injection device (154) that is configured to inject the multiple test signals (160-162) into multiple first connections (142-144), which are assigned to the multiple circuits, at a first point (141) of the electrical installation (100), wherein a different test signal of the multiple test signals (160-162) is injected into each first connection of the multiple first connections (142-144).

19. The test device according to Claim 18, wherein the test device (150) is configured to perform the method according to one of Claims 1-8.

20. The test device according to Claim 18 or Claim 19, furthermore comprising: - an acquisition device (156) that is configured to acquire multiple measurement signals at multiple second connections (146-148), which are assigned to the multiple circuits, at a second point (145) of the electrical installation (100).

21. The test device according to Claim 20, furthermore comprising: - a processing device (158) that is configured to determine assignments between in each case a first connection of the multiple first connections (142-144) and a second connection of the multiple second connections (146-148) on the basis of the injected test signals (160-162) and the acquired measurement signals.

22. The test device according to Claim 21, wherein the test device (150) is configured to perform the method according to one of Claims 9-17.