METHOD FOR TESTING THE WIRING OF AN ELECTRICAL SYSTEM

Description

AREA OF INVENTION

[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 installation in, for example, a substation or a power plant. 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 sequentially injected 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] Many power systems use a three-phase AC system. Similarly, many test instruments have at least three current or voltage outputs. Using these instruments, test signals can be fed in simultaneously, allowing the wiring of all phases to be tested in a single operation. For example, a 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.

[0005] 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

[0006] This allows wiring errors to be detected based on the measured amplitude, e.g. if the return conductor of a phase is incorrectly connected.

[0007] 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.

[0008] DE 10 2014 008750 A1 discloses a method for testing and investigating connection and conductor states in a wiring system. US 3 441 842 A discloses a method for determining the location of a short circuit between a conductor pair in a short-circuited circuit by applying a harmonic-rich simulation signal. US 2004 / 008018 A1 discloses a method for identifying elements of a circuit or for tracing a circuit based on the harmonic content of an excitation signal. SUMMARY OF THE INVENTION

[0009] 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.

[0010] 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.

[0011] 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 time-domain asymmetric waveform and a combination of harmonics from a predetermined group of higher harmonics. The time-domain asymmetric waveform can be the same for all of the several test signals.

[0012] The following terms apply to this description. A fundamental oscillation of the frequency fIt is called the first harmonic. An oscillation of twice the frequency. (2f) is referred to as the second harmonic. Generally, the oscillation is characterized by the n -times frequency nf the n -th harmonic. Higher harmonics are all harmonics except the first harmonic. Higher harmonics are also called overtones. n The -th harmonic is then referred to as the (n-1) The -th harmonic is designated.

[0013] The 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 against time, cannot be mapped onto itself by reflection across an axis perpendicular to the time axis. An example of such a time-domain asymmetric waveform is the sawtooth wave, which might have, for example, a rising edge with a small slope and a falling edge with a large (but negative) slope.

[0014] The combinations of harmonics of the multiple test signals are different, i.e., each test signal has its own unique combination of harmonics.

[0015] For example, each of the multiple test signals can exhibit a time-domain asymmetric waveform, which is generated 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 second and third harmonic in addition to a fundamental frequency. In another example, the time-domain asymmetric waveform can include, in addition to the fundamental frequency, only either the second or the third harmonic. A combination of further higher harmonics with corresponding amplitude factors, such as a combination of the fourth and fifth harmonics, can be superimposed on this time-domain asymmetric waveform.In other words, in this case, the specified group of higher harmonics includes the fourth and fifth harmonics. A first combination, which, for example, is assigned to the first test signal among several test signals, can contain a fourth harmonic but not a fifth. The first test signal thus includes the first, second, third, and fourth harmonics. A second combination, which, for example, is assigned to the second test signal among several test signals, can contain a fifth harmonic but not the fourth. The second test signal thus includes the first, second, third, and fifth harmonics. A third combination, which, for example, is assigned to the third test signal among several test signals, can contain neither the fourth nor the fifth harmonic. The third test signal thus includes only the first, second, and third harmonics.

[0016] Overall, the combination of harmonics from the multiple test signals is designed such that any linear combination of these signals exhibits essentially the same asymmetric properties in the time domain 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. With appropriate encoding of the higher harmonics (e.g., 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 components of the summed signal can also be easily determined.

[0017] The multiple test signals generated in this way are fed into several first terminals at a first point in the electrical installation, each corresponding to one of the multiple circuits of the electrical system. These multiple circuits can, for example, comprise multiple phases of the electrical system. A different test signal is fed into each of the first terminals. In other words, a different test signal is fed into each circuit of the electrical system at the first point. At a second point in the electrical installation, multiple measurement signals are acquired at several second terminals, each corresponding to one of the multiple circuits. For example, in a substation, the first point could be at an input of the substation, and the second point at one of the outputs.In another example, the first terminal could be on the first side of a transformer, and the second terminal on the second side. Based on the input test signals and the acquired measurement signals, a mapping is established between each of the first terminals (of several first terminals) and each of the second terminals (of several second terminals). This allows, for example, the wiring of the electrical system to be tested based on these mappings. Since the input test signals are distinct, it can be clearly determined which test signal at each of the second terminals resulted in a corresponding measurement signal, thus establishing a unique mapping between the first and second terminals. For example, crossovers and open circuits can be easily detected using the test signals.

[0018] 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".

[0019] The presence or absence of a specific harmonic, such as the fourth or fifth harmonic, thus constitutes a kind of digital encoding of the test signals. By including the sixth harmonic, the number of different combinations, and therefore the number of different test signals, can be increased. This allows, for example, test signals for testing the wiring of an electrical system with more than three phases or circuits, such as testing two three-phase system sections (a total of six phases) or system sections with multiple circuits (e.g., six or more circuits).

[0020] Multiple test signals can be simultaneously fed into the first several terminals. Likewise, multiple measurement signals can be acquired simultaneously. By encoding the test signals based on the different combinations of harmonics they contain, 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 at a single point in time 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.

[0021] According to one embodiment, the first harmonic, i.e., the fundamental frequency, of the time-domain asymmetrical signal waveform has a frequency that is not equal to the mains frequency or the nominal frequency of the electrical system. The first harmonic of the time-domain asymmetrical signal waveform 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, for example, a frequency of 52.63 Hz. By ensuring that the first harmonic of the test signals is not equal to 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 of the measurement signals. Since the fundamental frequency of the time-domain asymmetrical signal waveform has a frequency that 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.

[0022] In one embodiment, the amplitude of an nth harmonic of the group of higher harmonics has an amplitude factor of 1 / n 2< This refers to the amplitude of a fundamental oscillation of the time-domain asymmetrical signal waveform. The second and third harmonics described above can also exhibit a corresponding amplitude factor. Such amplitude factors enable the time-domain asymmetrical signal waveform to be achieved. Signal waveforms comprising the first to third harmonics and a combination of further higher harmonics, for example, the fourth and / or fifth and / or sixth harmonics, exhibit, for instance, a sawtooth-like signal shape with a steep rising edge and a shallow falling edge, resulting in a time-domain asymmetrical signal waveform. 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.

[0023] According to one embodiment, the assignments are determined by filtering the measurement signals with bandpass filters whose center frequencies correspond to the frequencies of the harmonics from the specified group of higher harmonics. The filtered measurement signals are compared with a threshold value. The threshold value can be set as a function of the amplitude of a fundamental frequency of the time-domain asymmetrical signal waveform. Since the harmonics of the test signal do not normally occur in the electrical system, the threshold value can be set relatively low, for example, to one percent of the fundamental frequency, so that even weak signals can be unambiguously assigned.With the coding of the test signals described above, a mapping between measurement signals and test signals, i.e. between first connections and second connections, can be carried out relatively easily by checking for the presence of a signal level at the outputs of the bandpass filters.

[0024] In another embodiment, the assignments are determined by identifying amplitudes in the measurement signals corresponding to the frequencies of the harmonics from the specified group of higher harmonics. These amplitudes can be determined, for example, using a discrete Fourier transform. The amplitudes thus determined are then compared to a threshold value. As described in the previous embodiment, the threshold value can be set relatively low, for example, to one percent of the fundamental frequency, so that even small amplitudes can be clearly identified. With the coding of the test signals described above, an assignment between measurement signals and test signals, i.e., between first and second connections, can be carried out relatively easily by checking for the presence of a signal level at frequencies of the corresponding harmonics.

[0025] The encoding of test signals by adding a combination of higher harmonics to the time-domain asymmetric signal shape will be described in detail below in the form of three embodiments.

[0026] In one embodiment, the specified group of higher harmonics includes a fourth harmonic and a fifth harmonic. The combinations for the various test signals are selected as described above: a first combination includes the fourth harmonic but not the fifth. A corresponding digital representation of this combination can be denoted by 10, where the first digit represents the presence (1) or absence (0) of the fourth harmonic, and the second digit represents the presence (1) or absence (0) of the fifth harmonic. A second combination includes the fifth harmonic but not the fourth. The corresponding digital representation of this combination is 01. A third combination includes neither the fourth nor the fifth harmonic, and the corresponding digital representation of this combination is 00.Therefore, a combination of just two harmonics can provide a sufficient number of test signals for testing a three-phase electrical system.

[0027] In another embodiment, the specified group of higher harmonics includes a sixth harmonic in addition to the fourth and fifth harmonics. Combinations for the various test signals can be selected as follows, with only the corresponding digital representation of these combinations listed for simplicity. In this digital representation, the first digit indicates the presence (1) or absence (0) of the fourth harmonic, the second digit the presence (1) or absence (0) of the fifth harmonic, and the third digit the presence (1) or absence (0) of the sixth harmonic. For example, a first combination is 100, a second combination is 010, and a third combination is 001.These combinations provide a sufficient number of test signals for testing a three-phase electrical system, with a Hamming distance of two between the three combinations, ensuring reliable detection of the combinations even with noisy or disturbed signals.

[0028] In yet another embodiment, the specified group of higher harmonics comprises the fourth, fifth, and sixth harmonics. Combinations for the various test signals can be selected as follows, with only the corresponding digital representations of these combinations listed for simplicity. For example, a first combination is 001, a second combination is 010, a third combination is 011, a fourth combination is 100, a fifth combination is 101, and a sixth combination is 110. These combinations provide a sufficient number of test signals for testing an electrical installation with two times three phases or up to eight circuits.

[0029] In a further embodiment, the predefined group of higher harmonics additionally includes amplitude factors that can be assigned to the higher harmonics. A unique combination of harmonics assigned to the respective test signal can additionally include one or more amplitude factors from the predefined group. For example, a first combination can have a specific higher harmonic, such as the fourth harmonic, with a first amplitude factor, such as 1 / 16. A second combination of the different combinations can have the same higher harmonic, i.e., the fourth harmonic, with a second amplitude factor, such as 1 / 24. A third combination of the different combinations can have the same higher harmonic, i.e., the fourth harmonic, with a third amplitude factor, such as 1 / 48.It should be noted that the amplitude factors, in this example the first, second, and third amplitude factors, are different. Further combinations can be based on a different higher harmonic, such as the fifth harmonic. With appropriate coding, phases of several multiphase systems, for example, several three-phase systems, or several circuits can be distinguished from one another, and thus their wiring can be tested simultaneously.

[0030] 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.

[0031] 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 acquired signal can be determined as a function of the mean value of the reference signal.

[0032] 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.

[0033] A test device according to the invention for testing the wiring of an electrical system with multiple circuits comprises a test signal generation device, a feed device, a detection device, and a processing device. The test signal generation device is configured to generate multiple test signals. Each of the multiple test signals has a time-domain asymmetrical waveform and a combination of harmonics from a predetermined group of higher harmonics. The combinations of harmonics of the multiple test signals are different. The feed 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 multiple first terminals at the first location are different. The detection device is designed to detect multiple measurement signals at multiple second terminals at a second location in the electrical installation, each corresponding to a different circuit. The first and second locations are distinct parts of the electrical installation. The multiple circuits can, for example, comprise multiple phases of the electrical installation. For instance, the first location might be on one side of a transformer in the electrical installation, and the second location on the other side.The detection device is designed to determine assignments between each first connection of the several first connections and a second connection of the several second connections based on the input test signals and the detected measurement signals.

[0034] 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 combinations of harmonics. 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, simplifying the detection of superimposed signals. However, individual phase detection also functions when the devices are not interconnected.

[0035] 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. BRIEF DESCRIPTION OF THE FIGURES

[0036] 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. 4schematically 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

[0037] 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.

[0038] 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.

[0039] Fig. 1Figure 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. 1In 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.

[0040] 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.

[0041] 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.

[0042] The test device 150 further comprises 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.

[0043] The test device 150 further comprises 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-in 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-in 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.

[0044] The operating principle of the test device 150 is described below with reference to the Figures 2 to 5 will be described in detail. Fig. 2 Figure 200 shows a method with process steps 202 to 214, which can be performed by the test device 150 to test the wiring of the electrical system 100. At least some of the steps in Figure 200 are shown in Figure 200. 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.

[0045] In step 202, several test signals are generated. Specifically, a separate test signal is generated for each phase. P p (t) This generates a signal shape that is asymmetrical in the time domain and a combination of harmonics from a predefined group of higher harmonics. The index p designates the phase for which the test signal P p (t)This is intended. The combinations of harmonics of the multiple test signals are different, so the test signals are also different. 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 can be used according to the following equation: P t = A ∑ n = 1 k 1 n 2 sin 2 πnf g t

[0046] 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.

[0047] For example, a signal can be equipped with A = 1, k = 3 and fg = 52.63 Hz can be formed. In other examples, A It can also be chosen so that the effective (RMS) value of the signal is approximately 1. For example, A ~0.962 will be selected.

[0048] Each of the test signals P p (t) includes further higher harmonics. For example, the test signal includes P 1 (t) For a first phase, additionally the fourth harmonic, the test signal P 2 (t) for a second phase additionally the fifth harmonic, whereas the test signal P 3 (t) The third phase does not include either the fourth or the fifth harmonic. Overall, the test signals for a three-phase system are calculated, for example, according to the following equation and table: P p t = A ∑ n = 1 k H n p sin 2 πnf g t signal Harmonious H n ( p ) n 1 2 3 4 5 P 1 ( t ) 1,0 0,25 0,111... 0,0625 0,0 P 2 ( t ) 1,0 0,25 0,111... 0,0 0,04 P 3 ( t ) 1,0 0,25 0,111... 0,0 0,0

[0049] In this case, a binary representation of the phase number was used in principle. p used and the amplitudes of the fourth and fifth harmonics adjusted or coded accordingly: Phase p Binary representation H 4 ( p ) H 5 ( p ) 1 10 1 4 2 (unchanged) 0.0 (removed) 2 01 0.0 (removed) 1 5 2 (unchanged) 3 00 0.0 (removed) 0.0 (removed)

[0050] The test signals have a time-domain asymmetric waveform, which, as will be described later, allows the polarity to be distinguished. The fundamental frequency of the test signals can be selected to create a time-varying signal that can be transmitted via current or voltage transformers of the system 100, for example, via transformers and / or capacitors. Furthermore, the test signals have essentially no DC component, thus preventing saturation of the current or voltage transformers. The fundamental frequency of the test signals can be selected to be within a favorable transmission range of the current or voltage transformers. For example, the fundamental frequency can be close to the nominal frequency of the transformers, i.e., close to the mains frequency.On the other hand, the fundamental frequency of the test signal should ideally not coincide with the fundamental frequency or harmonics of the mains frequency used or other frequencies occurring in the power system, in order to ensure the best possible separation between test signals and disturbances. The aforementioned fundamental frequency of 52.63 Hz, for example, meets these requirements for systems with a nominal frequency of 50 Hz or 60 Hz, as can be seen in the table below. fundamental frequency 2. Harm. 3. Harm. 4. Harm. 5. Harm. Test signal 52.63 Hz 105,26 157.89 Hz 210.52 Hz 263.15 Hz 50 Hz network 50.00 Hz 100.00 Hz 150.00 Hz 200.00 Hz 250.00 Hz 60 Hz network 60.00 Hz 120.00 Hz 180.00 Hz 240.00 Hz 300.00 Hz

[0051] However, other frequencies greater than 50 Hz and less than 60 Hz can also be used.

[0052] 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 phase encoding 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.

[0053] Fig. 3 shows the signal shapes of the test signals for phases 1, 2, and 3, as well as a sum signal of the test signals for phases 1, 2, and 3 divided by three. As can be seen from the Fig. 3As can be seen, the asymmetrical signal shape in the time domain is clearly recognizable in all test signals and also in the sum signal; that is, the signals all essentially have a relatively steep rising edge and a relatively flat falling edge compared to the rising edge.

[0054] In step 204, the generated test signals 160 to 162 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, for example, one or more transformers or 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, it is expected, for example, that the test signal fed in on outer conductor 120 will be output essentially on outer conductor 130, for example, with a changed voltage in the case of a transformer. However, the signal shape would be expected to remain essentially unchanged.Similarly, if electrical component 110 is correctly connected, 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 output essentially on the outer conductor 132.

[0055] 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.

[0056] 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.

[0057] 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 narrowband filters or a discrete Fourier transform for the fourth and fifth harmonics. Once the fundamental frequency has been determined... fg If a suitable frequency is chosen as described above, for example 52.63 Hz, there will be no overlap with the mains frequency or higher harmonics of the mains frequency.

[0058] By comparing the amplitude of the fundamental frequency of the respective measurement signal with the amplitudes of the higher harmonics, for example with the amplitudes of the fourth and fifth harmonics, the signal shapes can be determined. P1 (t), P2 (t) and P 3 (t)Differentiated signals can be identified. Since the relevant harmonics of the test signal do not occur in the normal operation of the power engineering system 100, relatively low threshold values ​​can be used for comparison, for example, 1% or 4% of the fundamental frequency. This allows even weak signals to be clearly identified. The following table shows an example of test signal detection using a threshold of 1%. H 4 H 5 Detected signal > 1% H 1 (available) < 1% H 1 (not available) Phase 1 P 1 ( t ) < 1% H 1 (not available) > 1% H 1 (available) Phase 2 P 2 ( t ) < 1% H 1 (not available) < 1% H 1 (not available) Phase 3 P 3 ( t ) > 1% H 1 (available) > 1% H 1 (available) Buzzer PS ( t )

[0059] For example, the test signal P 1 (t) A fault is detected when the amplitude of the fourth harmonic is greater than 1% of the fundamental frequency's amplitude and the amplitude of the fifth harmonic is less than 1% of the fundamental frequency's amplitude. The test signal P 2 (t)It is detected when the amplitude of the fourth harmonic is less than 1% of the fundamental frequency's amplitude and the amplitude of the fifth harmonic is greater than 1% of the fundamental frequency's amplitude. The test signal P 3 (t) A fault is detected when the amplitude of the fourth harmonic is less than 1% of the fundamental frequency's amplitude and the amplitude of the fifth harmonic is less than 1% of the fundamental frequency's amplitude. A sum signal of the three test signals is then used. P1 (t), P2 (t) and P 3 (t) exhibits both the fourth and the fifth harmonic, so that the sum signal P(t) It is recognized when the amplitude of the fourth harmonic is greater than 1% of the amplitude of the fundamental oscillation and the amplitude of the fifth harmonic is greater than 1% of the amplitude of the fundamental oscillation.

[0060] In the example above, the test signals were generated using different combinations of the fourth and fifth harmonics. To achieve greater robustness, for example, additional harmonics can be used. The table below shows an example of encoding using the fourth, fifth, and sixth harmonics with a Hamming distance of two and even parity. Phase p Coding H 4 ( p ) H 5 ( p ) H 6 ( p ) 1 100 1 4 2 (available) 0 (not available) 0 (not available) 2 010 0 (not available) 1 5 2 (available) 0 (not available) 3 001 0 (not available) 0 (not available) 1 6 2 (available)

[0061] In other examples, not only the presence or absence of a harmonic can be used for encoding, but also its amplitude. For example, only the fourth harmonic can be used, which, however, has different amplitudes for the different test signals: Phase p Coding H 4 ( p ) 1 00 1 4 2 2 01 2 3 1 4 2 3 10 1 3 1 4 2

[0062] The thresholds for detecting the different amplitudes of the fourth harmonic must be adjusted accordingly. In the example shown above, relatively small amplitudes were used for the fourth harmonic. The amplitude of a harmonic, for example the fourth harmonic, can also be chosen to be larger, i.e., larger than, for example, 1 / 16. It is important to ensure that the asymmetry in the time domain remains sufficiently significant. With appropriate encoding, not only individual phases but also various phase combinations can be distinguished.

[0063] 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.

[0064] In step 210, the polarities of the measurement signals acquired at the second position 145 are determined. Polarity detection is based on the asymmetrical signal shape in the time domain. For the measurement signals, which may have been pre-processed as described previously, respective time-domain derivatives are calculated. A given derivative can be determined, for example, by a discrete-time numerical derivative using differences between temporally acquired signal levels, or implicitly by 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 the phases p = 1, 2 and 3 as well as for the sum signal. A descriptive auxiliary signal can be used 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

[0065] This is δ Threshold 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.

[0066] In step 212, the phase assignments and polarities determined in this way can, for example, be displayed on a display device for a user.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] Fig. 6Figure 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. 6In 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.

[0072] 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.

[0073] The test device 650 comprises several test signal generation devices, which generate multiple test signals. In Fig. 6Two 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 Fig. 6In 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.

[0074] The test device 650 further comprises several detection devices for acquiring measurement signals. In the example of the Fig. 6The 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. 6As 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.

[0075] The test device 650 further comprises a processing device 655, which is located in the Fig. 6The 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.

[0076] The operating principle of the test device 650 essentially corresponds to that previously described with reference to the Figures 1 to 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.

[0077] 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 generates a signal shape that is asymmetrical in the time domain and a combination of harmonics from a predefined group of higher harmonics. The index p designates the circuit for which the test signal P p (t) is planned, for example, p=1 for circuit 601 and p=2for circuit 602. The combinations of harmonics of the multiple test signals are different, so the test signals are also different. 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 can be used according to the following equation: P t = A ∑ n = 1 k 1 n 2 sin 2 πnf g t

[0078] A here 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.

[0079] For example, a signal can be equipped with A = 1, k = 3 and fg = 52.63 Hz can be formed. In other examples, A It can also be chosen so that the effective value (RMS) of the signal is approximately 1.

[0080] Each of the test signals P p (t) includes further higher harmonics. For example, the test signal includes P 1 (t) additionally the fourth harmonic and the test signal P 2 (t) Additionally, the fifth harmonic. The test signals for the two circuits 601 and 602 are calculated, for example, according to the following equation and table: P p t = A ∑ n = 1 k H n p sin 2 πnf g t signal Harmonious H n ( p ) n 1 2 3 4 5 P 1 ( t ) 1,0 0,25 0,111... 0,0625 0,0 P 2 ( t ) 1,0 0,25 0,111... 0,0 0,04

[0081] In this case, a binary representation of the circuit number was used in principle. p used and the amplitudes of the fourth and fifth harmonics adjusted or coded accordingly: circuit p Binary representation H 4 ( p ) H 5 ( p ) 1 10 1 4 2 (unchanged) 0.0 (removed) 2 01 0.0 (removed) 1 5 2 (unchanged)

[0082] If additional circuits are to be included in the analysis, appropriate binary representations can be used to adjust the higher harmonics accordingly. For more than four circuits, further harmonics can be used, for example... H 6 (p) and / or H 7 (p). The test signals have a time-domain asymmetric waveform, which, as will be described later, allows the polarity to be distinguished. The fundamental frequency of the test signals can be selected to create a time-varying signal that can be transmitted via current or voltage transformers of the system 600, for example, via transformers and / or capacitors. Details on this were previously discussed in connection with the Figures 1 to 5 discussed and apply to the example of Fig. 6in the same way, where, for example, phase 1 corresponds to circuit 601 and phase 2 to circuit 602.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] Step 208 involves determining the mapping between test signals and measurement signals. In other words, step 208 identifies the test signals within the measurement signals. This identification can be achieved using narrowband filters or a discrete Fourier transform for the fourth and fifth harmonics.

[0087] By comparing the amplitude of the fundamental frequency of the respective measurement signal with the amplitudes of the higher harmonics, for example with the amplitudes of the fourth and fifth harmonics, the signal shapes can be determined. P 1 (t) and P 2 (t) They can be distinguished. Since the relevant harmonics of the test signal do not occur in the normal operation of the power engineering system 600, comparisons can be made using relatively low threshold values, for example, 1% or 4% of the fundamental frequency. This allows even weak signals to be clearly identified.

[0088] 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.

[0089] 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.

[0090] In step 212, the circuit assignments and polarities determined in this way can, for example, be displayed on a display device for a user.

[0091] 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.

[0092] In summary, the various test signals described above, which exhibit a time-domain asymmetric waveform and different combinations of higher harmonics, enable a fast and reliable inspection of the electrical system's wiring. 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 allow for the detection of polarity errors and the unambiguous differentiation of individual phases. The threshold values ​​used to identify the higher harmonics can be selected relative to the fundamental frequency and are therefore independent of the absolute amplitude of the signals.The method therefore also works with partial signals, which can occur, for example, due to current splitting or unwanted ground connections. Larger threshold values ​​can also be used, for example, 4% instead of 1%. This makes the method tolerant of frequency-dependent amplitude changes, such as the frequency response of converters.

[0093] For the individual test signals and their harmonics, it is not necessary to evaluate the phase relationship. Therefore, this method is tolerant of minor phase shifts, such as the frequency-dependent phase response of transducers. Furthermore, no synchronization between the test signal generation device and the detection device is required.

[0094] 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.

[0095] 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. Method for testing a wiring of an electrical installation having a plurality of circuits, comprising: - generating (202) a plurality of test signals (160-162), - feeding (204) the plurality of test signals (160-162) into a plurality of first terminals (142-144), associated with the plurality of circuits, at a first location (141) of the electrical installation (100), wherein another test signal of the plurality of test signals (160-162) is fed into each first terminal of the plurality of first terminals (142-144), - detecting (206) a plurality of measurement signals at a plurality of second terminals (146-148), associated with the plurality of circuits, at a second location (145) of the electrical installation (100), and - determining (208) associations between respectively a first terminal of the plurality of first terminals (142-144) and a second terminal of the plurality of second terminals (146-148) based on the fed test signals (160-162) and the detected measurement signals, characterized in that each of the plurality of test signals (160-162) has an asymmetrical waveform in the time domain and a combination of harmonics from a predetermined group of higher harmonics, wherein the combinations of harmonics of the plurality of test signals (160-162) are different.

2. Method according to claim 1, wherein the plurality of test signals (160-162) are simultaneously fed into the plurality of first terminals (142-144).

3. Method according to claim 1 or claim 2, wherein the predetermined group of higher harmonics comprises fourth and fifth harmonics.

4. Method according to any one of the preceding claims, wherein the asymmetric waveform in the time domain comprises at least second and / or third harmonics in addition to a fundamental oscillation.

5. Method according to any one of the preceding claims, wherein a fundamental oscillation of the asymmetrical waveform in the time domain has a frequency unequal to a mains frequency of the electrical installation.

6. Method according to any one of the preceding claims, wherein a fundamental oscillation of the asymmetric waveform in the time domain has a frequency in the range of 50 to 60 Hz, optionally a frequency in the range of 51 to 55 Hz, further optionally a frequency of 52.63 Hz.

7. Method according to any one of the preceding claims, wherein an amplitude of an n-th harmonic of the group of higher harmonics has an amplitude factor of 1 / n2 relative to an amplitude of a fundamental oscillation of the asymmetric waveform in the time domain.

8. Method according to any one of the preceding claims, wherein determining (208) associations comprises: - filtering the measurement signals with bandpass filters whose centre frequencies correspond to the frequencies of the harmonics from the predetermined group of higher harmonics, and - comparing the filtered measurement signals with a threshold value.

9. Method according to any one of the preceding claims, wherein determining (208) associations comprises: - determining amplitudes of frequencies in the measurement signals corresponding to the frequencies of the harmonics from the predetermined group of higher harmonics, and - comparing the determined amplitudes with a threshold value.

10. Method according to claim 8 or claim 9, wherein the threshold value is set as a function of an amplitude of a fundamental oscillation of the asymmetric waveform in the time domain.

11. Method according to any one of the preceding claims, wherein a first combination of the different combinations has a fourth harmonic and no fifth harmonic, a second combination of the different combinations has a fifth harmonic and no fourth harmonic, and a third combination of the different combinations has neither the fourth nor the fifth harmonic.

12. Method according to any one of the preceding claims, wherein a first combination of the different combinations has a fourth harmonic and no fifth harmonic, a second combination of the different combinations has a fifth harmonic and no fourth harmonic, and a third combination of the different combinations has no fourth and no fifth harmonic.

13. Method according to any one of the preceding claims, wherein a first combination of the different combinations has only a determined higher harmonic with a first amplitude factor, a second combination of the different combinations has only the determined higher harmonic with a second amplitude factor, and a third combination of the different combinations has only the determined higher harmonic with a third amplitude factor, where the first, second and third amplitude factors are different.

14. Method according to any one of the preceding claims, further comprising: - outputting the associations between respectively a first terminal of the plurality of first terminals and a second terminal of the plurality of second terminals to a user, and / or - comparing the associations between respectively a first terminal of the plurality of first terminals and a second terminal of the plurality of second terminals with predetermined associations between respectively a first terminal of the plurality of first terminals and a second terminal of the plurality of second terminals.

15. Method according to any one of the preceding claims, further comprising: - determining (210) polarities of the detected measurement signals to test the wiring of the electrical system depending on the determined polarities.

16. Method according to claim 15, wherein determining (210) polarities of the detected measurement signals for a respective measurement signal of the detected measurement signals comprises: - determining a derivative of a respective measurement signal, - generating a comparison signal by comparing the derivative with a threshold value, - determining a mean value of the comparison signal, and - determining the polarity of the respective measurement signal as a function of the mean value of the comparison signal.

17. Method according to claim 15, wherein determining (210) polarities of the detected measurement signals for a respective measurement signal of the detected measurement signals comprises: - determining a correlation factor as a function of a respective measurement signal and the asymmetric waveform in the time domain, and - determining the polarity of the respective measurement signal as a function of the correlation factor.

18. Testing device for testing a wiring of an electrical installation having a plurality of circuits, comprising: - a test signal generating device (152) configured to generate a plurality of test signals (160-162), - a feeding device (154) configured to feed the plurality of test signals (160-162) into a plurality of first terminals (142-144), associated with the plurality of circuits, at a first location (141) of the electrical installation (100), wherein another test signal of the plurality of test signals (160-162) is fed into each first terminal of the plurality of first terminals (142-144), - a detection device (156) configured to detect, at a second location (145) of the electrical installation (100), a plurality of measurement signals at a plurality of second terminals (146-148) associated with the plurality of circuits, and - a processing device (158) configured to determine associations between respectively a first terminal of the plurality of first terminals (142-144) and a second terminal of the plurality of second terminals (146-148) based on the fed test signals (160-162) and the detected measurement signals, characterized in that - each of the plurality of test signals (160-162) has an asymmetrical waveform in the time domain and a combination of harmonics from a predetermined group of higher harmonics, wherein the combinations of harmonics of the plurality of test signals (160-162) are different.

19. Testing device according to claim 18, wherein the testing device (150) is configured to carry out the method according to any one of claims 1-17.