Method for testing wiring of an electrical device

Abstract

The invention relates to a method (200) for testing a connection of an electrical device (100) having a plurality of circuits. In a method (100), a plurality of test signals (160-162) are generated. Each of the plurality of test signals (160-162) has a combination of predefined harmonics, the combination of predefined harmonics having at least one higher harmonic, where the at least one higher harmonic of the plurality of test signals (160-162) is different in amplitude and / or phase. The plurality of test signals (160-162) is injected at a first point (141) of the electrical device (100) into a plurality of first connections (142-144) assigned to a plurality of circuits.

Description

Technical Field

[0001] The present invention relates to a method for testing the wiring of an electrical device, in particular for testing the wiring of an electrical device having multiple circuits, such as an electrical power engineering device in a substation or a power plant. Background Art

[0002] During the installation, repair or expansion of an electrical device (such as in a substation or a power plant), wiring errors may occur. Especially in a device having multiple circuits and / or multiple phases (such as a device for three-phase alternating current), conductors may be mixed together; for example, two outer conductors may be mixed or an outer conductor may be mixed with a neutral conductor. In addition, for example, when connecting a transformer, the polarity may be reversed. Therefore, before commissioning or re-commissioning an electrical device, the wiring is usually tested to identify wrongly connected wires and reversed polarities.

[0003] For example, a test signal can be continuously injected into a single phase at an injection point, and a measurement signal can be obtained at a measurement point remote from the injection point, where the effect of the test signal should occur if the wiring is correct. If the expected effect of the test signal is not detected at the measurement point, there may be a wiring error. This procedure is relatively time-consuming because multiple measurements are required to check multiple circuits and phases, and the measuring device must be connected according to the injection point and the measurement point for each measurement. In addition, although such measurements can be used to determine the presence of a wiring error, it is not possible to directly determine the type of wiring error, for example, whether conductors are mixed together or not connected.

[0004] The correct polarity of current and voltage transducers also needs to be checked. For example, incorrect polarity may cause a protection relay to malfunction. In a measurement circuit, incorrect polarity may cause an apparently opposite current flow direction, resulting in incorrect measurement results. For these functions, it is also important to check the correct phase assignment from the transducer to the protection relay or counter.

[0005] There are other methods for checking polarity. These can also be used to check the correct phase assignment by advancing phase by phase and testing whether the expected reaction occurs on the phase being tested.

[0006] For example, a DC voltage test can be performed. In this test, a battery is temporarily connected to one side of the transducer, and the instantaneous deflection of a milliammeter or a millivoltmeter connected to the other side is recorded. The DC current flowing during this test can magnetize the transducer. The resulting saturation may cause a protection system failure. Therefore, it is important to demagnetize each tested current transducer after the test using this method. This method can be used to check the polarity and phase assignment of the secondary wiring. However, this requires one person to operate the battery switch and another person to make the measurement at another location at exactly the same time.

[0007] In other examples, AC voltage tests with phase comparison can be carried out. In this test, an AC voltage or an AC current is applied on one side of the transducer, and the phase of the voltage or current on the other side is determined, for example, using an oscilloscope, a special phase measurement device or a relay test device with this function. If the phase comparison shows approximately 0°, the polarity is correct; in the case of 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 be carried out directly on the transducer. To test the secondary winding of a relay or a counter, there must be the same AC voltage reference at each measurement position. For this purpose, either a separate cable with an AC voltage reference is connected to the measurement point, or a common reference, such as the mains AC voltage, is used. In the second case, it must be ensured that the mains voltage has the same phase at all measurement points.

[0008] Many power engineering systems use three-phase current systems. Similarly, many test devices have at least three current or voltage outputs. Therefore, these test devices can be used to inject test signals in parallel in one operation and test the wiring of all phases. For example, test signals with different amplitudes for different phases can be used for this purpose. In particular, the amplitudes of the current and voltage can be used here, and the combination and / or subtraction of these amplitudes will produce new amplitudes that cannot be produced in other cases.

[0009] Example:

[0010] L1 = 3 L1 + L2 = 8 L1 – L2 = -2L1 + L2 + L3 = 17

[0011] L2 = 5 L1 + L3 = 12 L1 – L3 = -6L1 + L2 - L3 = -1

[0012] L3 = 9 L2 + L3 = 14 L2 – L3 = -4L1 - L2 + L3 = 7

[0013] -L1 + L2 + L3 = 11

[0014] This enables the detection of wiring errors based on the measured amplitudes, for example, if the return conductor of one phase is wrongly connected.

[0015] However, in order to be able to make a clear assignment, the current or voltage amplitudes must have relatively large differences. Therefore, it is not always possible to work with amplitudes close to the nominal range of the device (e.g., 1A, 5A or 100V). In practice, there are also often cases of multiple parallel connections or ground connections. In these cases, the current distribution or voltage distribution is achieved according to the individual resistances. Therefore, it is no longer possible to carry out a clear phase detection. SUMMARY OF THE INVENTION

[0016] There is a need for improved options to test the wiring of electrical devices having multiple circuits, which options can be carried out quickly and reliably using simple methods.

[0017] According to the invention, there is provided a method for testing the wiring of an electrical device having multiple circuits and a test device for testing the wiring of an electrical device having multiple circuits, as defined in the independent claims. The dependent claims define embodiments of the invention.

[0018] A method according to the invention for testing the wiring of an electrical device having multiple circuits includes generating a plurality of test signals. Each of the plurality of test signals has a predefined combination of harmonics, the predefined combination of harmonics having at least one, preferably at least two, higher harmonics. The amplitude and / or phase position (hereinafter generally simply referred to as "phase") of at least one higher harmonic of the plurality of test signals is different.

[0019] In other words, each of the plurality of test signals includes a predefined combination of harmonics. The phase and / or amplitude of at least one higher harmonic among these predefined harmonics is different in each of the plurality of test signals. Thus, each test signal has a unique combination of amplitude and phase in at least one harmonic.

[0020] For example, each of the plurality of test signals includes one or more harmonics that are the same in each of the plurality of test signals (in particular, the same in terms of phase and amplitude). Each test signal also includes at least one higher harmonic. For each of the plurality of test signals, the at least one higher harmonic has a certain phase variation and / or amplitude variation. Thus, the phase and / or amplitude of the at least one higher harmonic is different in different test signals.

[0021] For example, in each of the plurality of test signals, the fundamental, second, and third harmonics may be the same, and in this example, the fourth and fifth harmonics corresponding to the at least one higher harmonic may have different phases and / or amplitudes in different test signals. In a simple example, each test signal may include a fundamental harmonic and a second harmonic. The fundamental harmonic is the same in all test signals, while the second harmonic has different phases in different test signals.

[0022] The following names are used in this description. The fundamental wave of frequency f is called the fundamental harmonic. The double-frequency oscillation (2f) is called the second harmonic. Generally, an oscillation having a frequency of nf is the nth harmonic. Higher harmonics refer to all harmonics other than the fundamental harmonic. The nth harmonic is here called the (n - 1)th higher harmonic.

[0023] In this description, the term "phase" has the following meanings: First, it is used to connect polyphase alternating currents. For example, in electrical engineering, one form of polyphase alternating current is called three-phase alternating current, which consists of three alternating currents or alternating voltages with the same frequency, and their phase angles are fixed and offset from each other by 120°. Each of these individual alternating currents or each of these individual alternating voltages can be assigned to components of a polyphase electrical device, such as the conductors of a power transmission cable or the windings of a transformer or a generator. A polyphase electrical device can thus have multiple circuits that are coupled to each other, and these circuits are called phases.

[0024] On the other hand, in this description, the term "phase" is also used to describe the phase positions of periodic signals in an electrical signal relative to each other. For example, an electrical signal such as a voltage can include a sinusoidal oscillation at 50 Hz and a sinusoidal oscillation at 100 Hz. The phase position, or simply "phase" for short, describes the phase angle between the zero crossings of these oscillations.

[0025] Each of a plurality of test signals can have a waveform that is asymmetric in the time domain. A waveform that is asymmetric in the time domain includes a fundamental harmonic (fundamental wave). The waveform is periodic with the frequency of this fundamental wave. Asymmetry in the time domain means that the waveform, which is plotted as the signal level varying with time, cannot be mapped onto itself by mirroring about the signal level axis perpendicular to the time axis. An example of such a waveform that is asymmetric in the time domain is a skewed oscillation, or a sawtooth oscillation, for example, with a rising edge having a smaller slope in amplitude and a falling edge having a larger (but negative) slope.

[0026] For example, each of the plurality of test signals may have a waveform that is asymmetric in the time domain, which is formed by superimposing a fundamental harmonic, a second harmonic, and a third harmonic, each harmonic having a corresponding amplitude factor. In this case, the waveform that is asymmetric in the time domain includes, in addition to the fundamental wave, for example, at least a second harmonic and a third harmonic. In another example, the waveform that is asymmetric in the time domain may include only a second harmonic or a third harmonic in addition to the fundamental wave. The at least one higher harmonic may include, for example, two higher harmonics, namely, a fourth harmonic and a fifth harmonic, where the amplitudes and / or phases of the fourth harmonic and the fifth harmonic are different in different test signals. The waveform that is asymmetric in the time domain, formed by the fundamental wave and the second and third harmonics, may have a fourth and a fifth harmonic superimposed thereon with different amplitudes and / or phases. For example, the first test signal among the plurality of test signals may have a fourth harmonic and a fifth harmonic in addition to the fundamental wave and the second and third harmonics, the fourth harmonic having an amplitude factor of 1.35 / 16 and a phase shift of +30° with respect to the amplitude or phase of the fundamental wave, and the fifth harmonic having an amplitude factor of 1 / 25 and a phase shift of -30° with respect to the amplitude or phase of the fundamental wave. The second test signal among the plurality of test signals may have a fourth harmonic and a fifth harmonic in addition to the fundamental wave and the second and third harmonics, the fourth harmonic having an amplitude factor of 1 / 16 and a phase shift of -30° with respect to the amplitude or phase of the fundamental wave, and the fifth harmonic having an amplitude factor of 0.5 / 25 and a phase shift of -30° with respect to the amplitude or phase of the fundamental wave. The third test signal among the plurality of test signals may have a fourth harmonic and a fifth harmonic in addition to the fundamental wave and the second and third harmonics, the fourth harmonic having an amplitude factor of 1 / 16 and a phase shift of 0° (i.e., no phase shift) with respect to the amplitude or phase of the fundamental wave, and the fifth harmonic having an amplitude factor of 0.5 / 25 and a phase shift of -30° with respect to the amplitude or phase of the fundamental wave. In the above examples, it is important that the test signals are different from each other, at least different from each other in at least one of the fourth and fifth harmonics, at least different from each other in amplitude or phase. In principle, for example, if the test signals are different from each other only in terms of the phase of the fourth harmonic, this is also sufficient. The more distinct the differences between the test signals are (for example, both the phases and amplitudes of the fourth and fifth harmonics are different), the higher the reliability with which the test signals can be identified, which is important in this method, as will be explained below.

[0027] Generally speaking, for example, the combination of harmonics of multiple test signals is designed such that any linear combination of the multiple test signals also substantially has the same characteristics as a single test signal in the time domain. For example, this can be achieved by the following means: the test signals only differ from each other in terms of higher harmonics (such as the fourth harmonic and the fifth harmonic), and are phase-synchronized with respect to the fundamental wave. If corresponding changes occur in the higher harmonics (such as the phase and / or amplitude of the fourth harmonic and the fifth harmonic), it is also possible to detect which individual signals appear in the sum signal (that is, the linear combination). Therefore, individual signals can be detected, and for the sum signal, it is also easy to determine the partial signals it contains.

[0028] At a first point of the electrical device, via multiple first connection parts assigned to multiple circuits of the electrical device, the resulting multiple test signals are injected. For example, the multiple circuits may include multiple phases of the electrical device. Different test signals among the multiple test signals are injected into each of the multiple first connection parts. In other words, different test signals are injected into each circuit of the electrical device at the first point.

[0029] At a second point of the electrical device, multiple measurement signals can be obtained at multiple second connection parts assigned to the multiple circuits. For example, in the case of a substation, the first point can be at the input of the substation, and the second point can be at one of the outputs of the substation. In another example, the first point can be on the first side of the transformer, and the second point can be on the second side of the transformer. The injected test signals and the obtained measurement signals can be used as the basis for determining the assignment between the first connection part in the multiple first connection parts and the second connection part in the multiple second connection parts respectively, so as to test the wiring of the electrical device based on the assignment, for example. Since the injected test signals are different, it is possible to clearly determine which test signal has caused the corresponding measurement signal at which second connection part, and thus the clear assignment between the first connection part and the second connection part can be determined. For example, based on the test signals, it is easy to determine confusion and also determine interruptions.

[0030] For example, in the case of a wiring error, it is possible to determine an assignment that does not correspond to the expected or predefined assignment, or there may be no assignment, or there is no complete assignment (such as due to an interruption or coupling with a completely incorrect circuit). On the other hand, in the case of no error, it is possible to determine an assignment corresponding to the predefined "target assignment".

[0031] Therefore, the test signal is clearly identified by different phases and / or amplitudes of at least one higher harmonic of different test signals, for example, the test signal is identified by different phases and / or amplitudes of the fourth and fifth harmonics in different test signals. Adding additional harmonics, such as the sixth harmonic, can increase the number of different identifications, thereby increasing the number of different test signals, so that, for example, it is possible to test test signals for wiring of electrical devices having more than three phases or circuits, such as for testing two three-phase installation components, that is, a total of six phases, or installation components having multiple circuits (such as having six or more circuits). However, in principle, it is also sufficient if only one higher harmonic in different test signals has different phases and / or amplitudes. For example, if three different phases and three different amplitudes are used in the fourth harmonic, nine different test signals may already be generated. In another example, only three different phases are used in the fourth harmonic, and three different test signals can already be generated. However, the more distinctive features there are, the better the different test signals can be distinguished from each other.

[0032] Multiple test signals can be injected into multiple first connection parts simultaneously. Similarly, multiple measurement signals can be acquired simultaneously. Since the test signals are identified based on different phases and / or amplitudes of certain harmonics, even if the test signals are carried by the electrical device simultaneously, the multiple measurement signals acquired at the second point of the electrical device can be clearly assigned to the corresponding test signals. Therefore, an appropriate measurement wiring for injecting test signals and capturing measurement signals can be achieved at one time point, and the wiring can be checked without changing the measurement wiring. Therefore, the wiring can be tested quickly. Wiring errors can be avoided because there is no need to change the measurement wiring to check the wiring of all circuits and / or phases.

[0033] According to one embodiment, the fundamental harmonic (i.e., the fundamental wave) has a frequency that is not equal to the power frequency or nominal frequency of the electrical device. The fundamental harmonic can have a frequency of, for example, 50 to 60 Hz, particularly 51 to 55 Hz, such as 52.6 Hz. Since the fundamental harmonic of the test signal is not equal to the power frequency of the electrical device, interference from other operating installation components can be avoided. Operating installation components usually generate power frequency interference signals (that is, for example, 50 Hz or 60 Hz), as well as interference signals having their higher harmonics. If the fundamental wave and higher harmonics of the test signal deviate from this power frequency and the corresponding higher harmonics, it is easy to detect and filter out interference signals from other operating installation components in the measurement signal. Since the fundamental wave has a frequency that does not deviate significantly from the nominal frequency of the electrical device, the test signal is suitable for transmission through the electrical device, for example, through a current or voltage converter having a transformer and / or a capacitor.

[0034] In one embodiment, the amplitude of the nth harmonic of the high-order harmonics whose phase and / or amplitude are not used for identification has 1 / n relative to the amplitude of the fundamental wave. 2 The amplitude factor. For example, the above-mentioned second and third harmonics may also have corresponding amplitude factors. Such amplitude factors can achieve an asymmetric waveform in the time domain. Including the waveform of the first to third harmonics with an amplitude factor of 1 / n 2 has, for example, a sawtooth waveform, and the sawtooth waveform has a steep rising edge and a shallower falling edge, so that the waveform is asymmetric in the time domain. In addition, the test signal generated in this way has substantially no DC component on average, so that saturation of current or voltage converters in electrical devices can be avoided. If at least one high-order harmonic with a varying amplitude and / or phase is additionally superimposed, as long as the amplitude is of the order of 1 / n 2 such as 1.5 / n 2 or 0.5 / n 2 , the sawtooth waveform is also basically retained.

[0035] According to one embodiment, the assignment is determined by determining the amplitude and phase of the spectral components of the harmonic frequencies in the measurement signal. The amplitude and phase of the spectral components are respectively compared with an amplitude threshold and a phase threshold. The amplitude threshold can be set based on the amplitude of the fundamental wave. The amplitude and / or phase position of the fundamental wave can be determined from the measurement signal.

[0036] In one embodiment, the at least one high-order harmonic includes fourth and fifth harmonics. 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 the fundamental wave amplitude. As described above, the amplitude of one of the other nth high-order harmonics of the predefined harmonics may have 1 / n 2 relative to the amplitude of the fundamental wave.

[0037] For example, the phase of the fourth harmonic relative to the fundamental wave may have a phase shift of +30° or 0° or -30°, and the phase of the fifth harmonic relative to the fundamental wave may have a phase shift of +30° or 0° or -30°. In other examples, the phase shift of the fourth or fifth harmonic relative to the fundamental wave can be, for example, +20° or 0° or -20°. A phase shift in the range of, for example, + / -90° can be selected, preferably in the range of + / -45°, and more preferably in the range of + / -30° relative to the phase of the fundamental wave.

[0038] According to another embodiment, the method further includes determining the polarity of the acquired measurement signal in order to test the wiring of the electrical device based on the determined polarity. In particular, the asymmetric waveform of the test signal in the time domain enables a simple and reliable determination of the polarity. For example, if the wiring of a transformer is incorrect, such as the connections on one side of the transformer being confused, the measurement signal may have a polarity opposite to that of the corresponding test signal. In the case of an asymmetric waveform in the time domain, the opposite polarity can be easily detected. For example, if the test signal has a steep rising edge and a shallow falling edge, the measurement signal with the opposite polarity has a shallow rising edge and a steep falling edge. Thus, the corresponding error in the wiring can be determined.

[0039] To determine the polarity of the acquired measurement signal, for example, for the corresponding measurement signal of the acquired measurement signal, the derivative of the measurement signal can be determined and a comparison signal can be generated by comparing the derivative with a threshold. For example, for a range of derivatives with a positive slope higher than the threshold, the comparison signal can have a positive value, while for a range of derivatives with a negative slope higher than the threshold, it can have a negative value with the same absolute value. If the average value of the comparison signal is subsequently determined, such as as a sliding average or over a period of the fundamental wave of the test signal, the polarity of the measurement signal can be determined based on the mean value of the comparison signal.

[0040] Alternatively or additionally, determining the polarity of the acquired measurement signal for the corresponding measurement signal can include determining a correlation coefficient, in particular a correlation factor, based on the corresponding measurement signal and an asymmetric waveform in the time domain. The polarity of the corresponding measurement signal can be determined based on the correlation factor. In the case of the same polarity, the correlation factor is positive, for example, its value is close to 1. In the case of opposite polarities, the correlation factor is negative, for example, its value is close to -1.

[0041] A test device for testing the wiring of an electrical device having a plurality of circuits according to the present invention includes a test signal generation device and an injection device. The test signal generation device is configured to generate a plurality of test signals. Each of the plurality of test signals has a combination of harmonics, and the combination of harmonics has at least one higher harmonic. The phase and / or amplitude of the at least one higher harmonic is different in different test signals. The injection device is configured to inject the plurality of test signals into a plurality of first connections at a first point of the electrical device. The plurality of first connections are assigned to the plurality of circuits of the electrical device. Different test signals among the plurality of test signals are injected into each of the plurality of first connections. Since the test signals are based on different combinations of harmonics, the test signals injected into the plurality of first connections at the first point are different.

[0042] In some exemplary embodiments, the test device further includes an acquisition device and a processing device. The acquisition device is configured to acquire a plurality of measurement signals at a second point of the electrical device at a plurality of second connection portions assigned to a plurality of circuits. The first point and the second point are different points of the electrical device. For example, the plurality of circuits may include a plurality of phases of the electrical device. For example, the first point may be on one side of a transformer of the electrical device, and the second point may be on the other side of the transformer. The acquisition device is configured to determine an assignment between a first connection portion among the plurality of first connection portions and a second connection portion among the plurality of second connection portions based on the injected test signal and the acquired measurement signal.

[0043] The test signal generating device may include a plurality of single-phase devices, each single-phase device generating only one test signal. The plurality of single-phase devices may be configured such that each of them generates one of the plurality of test signals based on different amplitudes and / or phases of the at least one higher harmonic. Alternatively or additionally, the test signal generating device may include a plurality of polyphase devices, such as two three-phase devices, in order to generate six test signals, and the six circuits or phases can be tested simultaneously using the six test signals. In this case, the devices can be connected to achieve the same phase for the fundamental wave, which simplifies the detection of the superimposed signal. However, when the devices are not coupled, the detection of each phase also works.

[0044] The test device may be specifically designed to perform one embodiment of the above method or its embodiments, and thus also includes the advantages associated with the method described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be explained in more detail below with reference to embodiments based on the drawings. In the drawings, the same reference numerals denote the same elements.

[0046] Figure 1 A test device for testing the wiring of an electrical device having multiple phases is schematically shown according to one embodiment.

[0047] Figure 2 A method for testing the wiring of an electrical device having multiple phases is shown according to one embodiment.

[0048] Figure 3 A plurality of test signals according to one embodiment are schematically shown, which have a combination of waveforms asymmetric in the time domain and higher harmonics.

[0049] Figure 4 Schematically shown are from Figure 3 the time derivatives of a plurality of test signals.

[0050] Figure 5A comparison signal formed by comparing the derivative of a test signal with a threshold is schematically shown.

[0051] Figure 6 Another test device for testing the wiring of an electrical device having a plurality of circuits according to an embodiment is schematically shown. Detailed Description of the Invention

[0052] The present invention will be explained in more detail below based on embodiments with reference to the accompanying drawings. In the figures, the same reference numerals denote the same or similar elements. The drawings are schematic diagrams of various embodiments of the present invention. The elements shown in the drawings are not necessarily shown to scale. Instead, the various elements shown in the drawings are presented in a manner that enables those skilled in the art to understand their functions and purposes.

[0053] The connections and couplings between the functional units and elements shown in the figures can be implemented as direct or indirect connections or couplings. The connections or couplings can be implemented in a wired or wireless form.

[0054] Figure 1 A part of the electrical device 100 is schematically shown to which a test device 150 for testing the wiring of the electrical device 100 is connected. The electrical device 100 is a polyphase electrical device. Many power engineering systems use a three-phase current system. In Figure 1 the example shown, the electrical device 100 is a three-phase system. For example, the electrical device 100 can include a high-voltage device or a part thereof. The electrical device 100 includes an electrical component 110 on which two three-phase connections are provided. The electrical component 110 can include, for example, a three-phase circuit breaker, a three-phase transformer, a plurality of transformers, a capacitor, current and voltage converters, or an intermediate converter. On the first side 112, the electrical component 110 has connections to the outer conductors 120 to 122 of the three-phase power line 125. On the second side 114, the electrical component 110 has connections to the outer conductors 130 to 132 of the second three-phase power line 135. The electrical component 110 can have other connections, such as for grounding or for a neutral conductor of a star-connected three-phase system, but these other connections are not shown for the sake of clarity. Wiring errors may occur when installing the electrical component 110. For example, two outer conductors (such as outer conductors 120 and 121) may be connected in the wrong way on the first side 112 of the electrical component 110. Therefore, after installing or repairing the electrical device 100, it may be necessary to check the wiring.

[0055] To check the wiring, Figure 1 the test device 150 shown can be electrically coupled to both sides 112, 114 of the electrical component 110.

[0056] The test device 150 includes a test signal generation device 152 that generates a plurality of test signals. To test the three-phase electrical device 100, the test signal generation device 152 generates, for example, three test signals 160 to 162. The test device 150 further includes an injection device 154 through which the test signals 160 to 162 are injected into a plurality of first connection parts 142 to 144 at a first point 141 of the electrical device 100 via corresponding lines 170 to 172. The injection device 154 can, for example, adapt the test signals from the test signal generation device 152 to the nominal range of the electrical component 110 and provide them at three connection points. A set of lines including three lines 170 to 172 can be connected to three connections of the injection device 154. At the first point 141, for example, at a relatively accessible power distribution upstream of the electrical component 110, the line 170 can be connected to the outer conductor 120 to inject the first test signal into the outer conductor 120. The line 171 can be connected to the outer conductor 121 to inject the second test signal into the outer conductor 121. The line 172 can be connected to the outer conductor 122 to inject the third test signal into the outer conductor 122. Thus, the corresponding test signals are injected into each phase on the first side 112 of the component 110.

[0057] The test device 150 may further include an acquisition device 156 that is connected to three outer conductors 130 to 132 via corresponding lines 180 to 182, and the three outer conductors 130 to 132 are connected to the second side 114 of the component 110 via corresponding second connection parts 146 to 148 at a second point 145 of the electrical device 100. The second point 145 may be located at an accessible power distribution of the electrical device 100. Thus, corresponding measurement signals can be acquired for each phase on the second side 114.

[0058] The test device 150 may further include a processing device 158. The processing device 158 includes, for example, an electronic controller, such as a microprocessor controller, which is capable of, for example, executing a computer program. As will be described in detail below, the processing device 158 may be coupled to the test signal generation device 152 and the acquisition device 156 so as to drive them in a coordinated manner. 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 test signals independently of any control by the processing device 158. Thus, it is evident that the test signal generation device 152, the injection device 154, the acquisition device 156, and the processing device 158 do not necessarily have to be formed in the same housing or a single unit, but may include spatially independent units having their own housings. For example, the test signal generation device 152 together with the injection device 154 may form a unit that can operate and be set independently of any other unit including the acquisition device 156 and the processing device 158. Thus, even in a large electrical device where the first point 141 is far from the second point 145, the test device 150 can be used without the need for corresponding long lines 170 to 172 or 180 to 182.

[0059] The manner in which the test device 150 operates will be described below with reference to Figures 2 to 5 in detail. Figure 2 A method 200 is shown, which has method steps 202 to 214 that can be executed by the test device 150 to test the wiring of the electrical device 100. In particular, steps 206 to 214 may in this case be optional or replaced by other steps based on the signals generated and injected in steps 202 and 204. Figure 2 At least some of the processing steps shown in may in particular be executed using the processing device 158, for example by a computer program executed by the processing device 158.

[0060] In step 202, a plurality of test signals are generated. Specifically, a separate test signal P p (t) is generated for each phase, the test signal having a waveform that is asymmetric in the time domain and a combination of predefined harmonics, the combination of predefined harmonics having at least one higher harmonic. The flag p represents the phase for which the test signal P p (t) is intended. The plurality of test signals differ from one another in that the amplitude and / or phase position (hereinafter referred to as phase) in the at least one higher harmonic is different. For example, the test signals may be based on a common signal P(t) that has a waveform that is asymmetric in the time domain. The waveform of the common signal P(t) may approximate a sawtooth waveform. For this purpose, for example, sine signals having different amplitudes and frequencies may be used, which are approximated to a sawtooth waveform by Fourier synthesis. For example, a signal according to the following equation may be used as the common signal P(t):

[0061]

[0062] Here, A represents the amplitude of the entire signal, k represents the number of harmonics used, and f g represents the fundamental frequency of the signal. The term weights a single sine function so as to approximate a sawtooth waveform overall.

[0063] For example, a signal with A = 1, k = 3, and f g = 52.6 Hz can be formed. In other examples, A can also be selected such that the root mean square (RMS) of the signal is approximately 1. For example, A ~ 0.962 can be selected.

[0064] The test signal P p (t) each also includes at least one higher harmonic, where the amplitude and / or phase of the at least one higher harmonic is different in different test signals. In the following example, the at least one higher harmonic includes two higher harmonics, namely the fourth and fifth harmonics. In other examples, additional or different harmonics may be used to distinguish between different test signals. However, in principle, one higher harmonic is already sufficient to distinguish between different test signals. The advantage of using multiple higher harmonics is that this improves the distinguishability between test signals (e.g., when the test signals are subject to interference or noise). The test signals are encoded by different amplitudes and / or phases in at least one higher harmonic. This encoding can represent, for example, phase information in a polyphase electrical system, which indicates the phase of the electrical device 100 to which the test signal is assigned.

[0065] To encode the phase information into the sawtooth signal, the amplitudes and phases of, for example, two higher harmonics are slightly changed. For example, the fourth and fifth harmonics are changed to encode this phase information while keeping the fundamental wave and the second and third harmonics unchanged. Overall, only five harmonics are used to limit the bandwidth of the test signal.

[0066] The following equation shows the definition of the modified test signal y(t) containing five harmonics (k = 5).

[0067]

[0068] The amplitude change a n and the phase change used can be represented by introducing an amplitude modifier A[n] and a phase modifier P[n] for the nth harmonic. For example, both can have three specific values, for example, represented as -1, 0, and +1. The assignment of a n and in the above equation is shown in Table 1 below.

[0069]

[0070] Table 1: Amplitude and Phase Changes

[0071] Obviously, the amplitude and phase changes can also be represented in other ways, for example, directly represented by the corresponding amplitude factor and phase angle. Obviously, values other than three can be used to represent the changes, for example, two values or more than three values. The phase angles in Table 1 are represented in radians. 0.5 rad corresponds to approximately 28.6°. In other examples, other phase angles can be used to represent the changes, such as + / -20° or + / -40°.

[0072] Due to the relatively small amplitudes of the fourth and / or fifth harmonics, the asymmetrical waveform changes only to a negligible extent. Lower harmonics, such as the second and third harmonics, are less suitable for encoding phase information because they significantly affect the asymmetry of the signal in the time domain and may thus complicate the detection, especially the detection of polarity. Higher harmonics, especially the seventh harmonic or higher harmonics, are also less suitable because current and voltage converters usually attenuate high frequencies to a greater extent, which may weaken the transmission and detection.

[0073] This amplitude and phase change scheme has three fixed values for two amplitude modifiers and two phase modifiers, enabling the encoding of 3 2+2 = 81 different code words. Obviously, as an alternative, only one amplitude change or one phase change can be used. For example, in the case of only one phase change, the value of the amplitude modifier A[n] is 0, that is, the value of the amplitude change a n is 1.

[0074] To increase the robustness of the encoding, for example, only five code words are used among the 81 possible code words. These five code words are hereinafter referred to as CWS, CW1, CW2, CW3, and CW4 respectively. CWS represents a sawtooth test signal with no change. CW1 - CW4 can be used to identify four different phases or circuits of an electrical device. In a three-phase device and power grid, the code word CW4 for the fourth phase is usually not required, but it is discussed here at least for reasons of symmetry.

[0075] Table 2 below shows an example of the assignment of code words to the amplitude and phase modifiers A and P.

[0076]

[0077] Table 2: Mapping of Code Words to Amplitude and Phase Modifiers

[0078] All 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 can be calculated for each combination of the codewords used to obtain the Hamming distance between the codewords. Table 3 below shows the Hamming distances obtained.

[0079]

[0080] Table 3: Hamming distances between codewords

[0081] The minimum distance between all the codewords used is 4, which enables the detection and correction of single errors, such as incorrectly detected amplitude or phase values. Additionally, two incorrectly detected modifiers may be detected as errors but cannot be corrected. In the case of a single incorrect symbol, the next valid codeword with a Hamming distance of 1 is used. If the distance is larger, the codeword is considered incorrect.

[0082] In this case, this would mean that the phase information of a highly distorted signal cannot be decoded correctly, but it is still possible to detect that it is a valid polarity test signal.

[0083] A signal with a fundamental frequency of 52.6 Hz can be used for this method. The signal is limited to the fifth harmonic, with a maximum frequency of 263 Hz. Since the coding used is static coding, no higher frequencies are generated due to modulation. Conventional current and voltage converters are capable of transmitting these relatively low frequencies without significant attenuation or phase shift.

[0084] Figure 3 The waveforms of the test signals based on the codes CW1, CW2, and CW3 for phases 1, 2, and 3 and the test signal without change based on the code CWS are shown. From Figure 3 it can be seen that the asymmetric waveforms in the time domain are clearly recognizable for all test signals, that is, these signals basically all have relatively steep rising edges and relatively shallow falling edges compared to the rising edges.

[0085] In step 204, the test signals 160 to 162 generated for phases 1, 2, and 3 are injected into the outer conductors 120 to 122 at the first point 141 via the first connection parts 142 to 144. The test signals 160 to 162 can be injected simultaneously. The test signals injected in this way pass through the electrical component 110, which includes, for example, one or more transformers or capacitors or other electrical engineering equipment, such as a circuit breaker. On the second side 114, due to the injected test signals, the electrical component 110 outputs output signals on the three outer conductors 130 to 132. When the electrical component 110 is correctly connected, for example, it is expected that the test signal injected onto the outer conductor 120 will be substantially output onto the outer conductor 130. For example, in the case of a transformer, the voltage will change. However, it is expected that the waveform will remain substantially unchanged. Similarly, when the electrical component 110 is correctly connected, for example, it is expected that the signal injected into the outer conductor 121 will be substantially output onto the outer conductor 131, and the signal injected into the outer conductor 122 will be substantially output onto the outer conductor 132.

[0086] In the case of incorrect wiring, where the outer conductors 121 and 122 are connected in the wrong way, conversely, the signal injected onto the outer conductor 121 is output onto the outer conductor 132, and the signal injected into the outer conductor 122 is output onto the outer conductor 131.

[0087] In step 206, a plurality of measurement signals are acquired at the second point 145. The plurality of measurement signals can be acquired simultaneously or sequentially. In the acquisition device 156, the acquired measurement signals can optionally be preprocessed (e.g., by filtering). For example, analog and / or digital filters can be used to preprocess the measurement signals in order to, for example, suppress interference caused by resistance, inductance, or capacitance coupling, such as the resistance voltage drop due to current flowing through a common return conductor. Such interference may affect the outer conductors 120 to 122 and 130 to 132, for example, from an adjacent system that is in operation. In addition, for example, a notch filter for the power supply frequency (e.g., 50 Hz, 60 Hz, or 16.7 Hz or a combination thereof) can be used to filter out interference from the adjacent system. Additional notch filters can be used to filter the measurement signals to filter out the higher harmonics of the power supply frequency. Alternatively or additionally, a low-pass filter can be applied to the measurement signals to eliminate the higher harmonics and other interference. In this case, the cut-off frequency may be higher than the frequency of the highest harmonic used in the test signal. Finally, a high-pass filter can be applied to the measurement signals to remove low-frequency interference, where the cut-off frequency can be lower than the fundamental frequency of the test signal. The preprocessing of the measurement signals can improve the reliability of the wiring check and the sensitivity to interference from adjacent systems in operation.

[0088] In step 208, the allocation between the test signal and the measurement signal is determined. In other words, in step 208, the test signal is identified in the measurement signal. Identifying an individual test signal in the measurement signal may include determining the amplitude and phase of the spectral components for the frequencies of predefined harmonics, in particular for the frequencies of the higher harmonics used for coding in the measurement signal. The amplitude and phase of these spectral components can be compared with an amplitude threshold and a phase threshold respectively. The amplitude threshold can be set according to the amplitude of the fundamental wave of the asymmetric waveform in the time domain.

[0089] If the fundamental frequency f is properly selected as described above g , for example 52.6 Hz, there is no overlap with the power supply frequency or the higher harmonics of the power supply frequency.

[0090] As described above, the information for identifying the phase is robustly encoded in the sawtooth test signal. This enables the correct polarity and phase allocation to be checked without the need for a common reference and independently of the signal amplitude.

[0091] The modified sawtooth test signal can be decoded with the acquired measurement signal in the following steps, for example:

[0092] In the first step, the received measurement signal can be filtered using a low-pass filter to limit its bandwidth to, for example, 263 Hz, that is, to the frequency used as the highest frequency when generating the test signal. In the above example, 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.

[0093] In the second step, the measurement signal is examined for the frequency components of the five harmonics used in this example. The period duration of each signal of interest is known (for example 52.6 Hz and its integer multiples), so a discrete Fourier transform (DFT) can be performed using, for example, the Goertzel algorithm. The Goertzel algorithm provides the amplitude and phase and is applied to all frequencies of interest, for example to the five frequencies of the five harmonics used. A longer integration interval (for example 20 periods) can be used to additionally suppress noise and interference by taking advantage of the averaging effect.

[0094] Finally, the phase information is decoded. The amplitudes of the fourth and fifth harmonics are normalized according to the average amplitude of the first three harmonics. For example, the discriminator then tests the deviation of the amplitudes and phases of the harmonics from the values shown 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 between the two) to the detected amplitude and phase modifiers and assigns them to one of 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, the detector accepts it as the correct codeword. Based on the phase information determined in this way, it is possible to determine which test signal is included in which measurement signal, and thus determine the outer conductor output by the input test signal.

[0095] If the reported Hamming distance is two or greater, the Hamming distance can be used as a polarity check signal, but phase information cannot be reliably derived from it. However, at least it is detected that the test signal is significantly disturbed, and this disturbance can be output to the operator.

[0096] Based on the assignment between the test signal and the measurement signal determined in step 208, it is possible to easily determine whether the expected test signal is obtained at the corresponding outer conductors 130 to 132. If the assignment does not meet the expectation, incorrect wiring may be determined.

[0097] In step 210, the polarity of the measurement signal obtained at the second point 145 is determined. The polarity is detected based on the asymmetric waveform in the time domain.

[0098] For example, the polarity can be detected in the following way: The amplitude of the harmonic is compared with the detected fundamental wave. 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 value, it is considered a valid sawtooth signal, that is, a sawtooth signal with the correct polarity. In the case of correct polarity, all harmonics have substantially the same phase as the fundamental wave except for the set phase change. In the case of signal inversion, each second harmonic in the frequency domain is inverted, resulting in a phase shift of 180. This is significantly greater than the phase change. Therefore, only when the phase value of the second harmonic is 0° and 180° (+ / - 30°), and the phase value of the third harmonic is only 0° (+ / - 30°) is it considered a sawtooth signal with the correct polarity. In the case of a polarity of ~0°, it is considered the correct polarity, and in the case of a polarity of ~180°, it is considered the incorrect (inverted) polarity.

[0099] In a further example, the polarity can be evaluated as follows. For a measurement signal that can be preprocessed as described above, the corresponding derivative is formed in the time domain. For example, the corresponding derivative can be determined by using a time-discrete numerical differentiation of the difference between the signal levels obtained in the time series, or implicitly determined by a suitably adjusted filter structure, for example by using an analog operational amplifier as a differentiating circuit or a digital filter structure. Figure 4 Shows the derivative dM p (t) of the measurement signals M p (t) for phases p = 1, 2, and 3, which is obtained in response to test signals for phases 1, 2, and 3 based on the encoded CW1, CW2, and CW3 (in the case of correct wiring and correct polarity). For example, the corresponding auxiliary signal Q p (t) can be formed for each of the derivatives according to the following rule:

[0100]

[0101] In this case, δ is a threshold value used to suppress noise and other unwanted interferences. Figure 5 The auxiliary signal Q 1 (t) for the test signal of phase 1 is shown by way of example. Based on the auxiliary signal Q p (t), the corresponding average value is calculated over a certain period of time This average value can be calculated, for example, at discrete times, such as the period duration T of the fundamental wave of the test signal, or continuously calculated by a low-pass filter. If this average value exceeds a defined positive threshold, it indicates a positive polarity (short rising edge and long falling edge). If the average value is below a defined negative threshold, it indicates a negative polarity (long rising edge and short falling edge). Thus, the polarity change for each phase can be easily determined, for example, a polarity change that may occur due to incorrect wiring.

[0102] In step 212, the phase assignment and polarity determined in this way can be output, for example, on a display device for the user.

[0103] For example, a first test signal for phase 1 can be output on line 170, a second test signal for phase 2 can be output on line 171, and a third test signal for phase 3 can be output on line 172. If the electrical device 100 is correctly wired, 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. The test device 150 can also indicate that the test signals are output and detected with a positive polarity. Wiring errors (such as outer conductor confusion or incorrect wiring that causes polarity inversion (e.g., at a transformer)) can be recognized by the operator based on the output.

[0104] Alternatively or additionally, in step 214, the detected phase assignment can be compared with the target assignment, and / or the detected polarity can be compared with the target polarity. If a deviation between the detected state and the target state has been determined, a warning can be automatically output.

[0105] The electrical device 100 can also have other connections, such as other three-phase connections, and their wiring can be checked in the same manner as described above. For example, these connections may involve auxiliary circuits or control circuits, and depending on the type of the circuit, the above method can also be used for testing.

[0106] If multiple circuits or phases are tested, they can use a common neutral conductor (N for L1, L2, and L3) or completely independent circuits (L1+N1, L2+N2, L3+N3). In this case, various wiring errors are also conceivable and can be detected using this method. If a wiring error occurs, multiple ground connections may appear. For example, a current clamp can be used to measure the current passing through the ground connection as one of multiple measurement signals. The described method enables the use of the assignment to detect which test signals can be detected in the ground connection, so that desired and undesired ground connections can be identified.

[0107] Figure 6 Part of another electrical device 600 is schematically shown to which a test device 650 for testing the wiring of the electrical device 600 is connected. The electrical device 600 includes a plurality of circuits that can be assigned to one or more phases. In Figure 6In the example shown, the electrical device 600 includes two circuits 601 and 602 that are substantially separated from each other. However, the circuits 601 and 602 can also be assigned to one phase of a polyphase system, that is, the same phase in a polyphase system, or assigned to multiple different phases in a polyphase system, or can be connected to each other through their neutral conductors. In other examples, the electrical device 600 can include more than two circuits. For example, the electrical device 600 can include a high-voltage device or a part thereof. Each of the circuits 601 and 602 can include one or more electrical components, such as current or voltage converters 610, 630, secondary wiring 612, 632, matching converters, test plugs 614-619, 634-639, test switches 611, 631, counters, and / or protection devices, such as relays 613, 633.

[0108] After installing or repairing the electrical device 600, it may be necessary to check the wiring. To check the wiring, Figure 6 the test device 650 shown can be electrically coupled to both the circuits 601 and 602.

[0109] The test device 650 includes multiple test signal generating devices that generate multiple test signals. Figure 6 Two test signal generating devices 652 and 654 for generating two test signals are shown. The multiple test signals can also be generated by a common test signal generating device. Each of the test signal generating devices 652 and 654 is assigned a corresponding injection device (not shown), through which the test signal is injected into the electrical device 600 at the corresponding injection point via the corresponding line. The injection device can, for example, adapt the test signals from the test signal generating devices 652, 654 to the required nominal range at the corresponding injection point. In Figure 6 the example shown, the test signal from the test signal generating device 652 can be injected, for example, at the test plugs 616, 617 on the secondary side of the converter 610 (such as a current converter or a voltage converter). Alternatively, the test signal from the test signal generating device 652 can also be injected at the test plugs 614, 615 on the primary side of the converter 610, as shown by the dashed line. Injection on the primary side enables additional checking of the polarity and wiring of the converter 610. In the case of injection on the primary side, the current converter may require a correspondingly higher current, and the voltage converter may require a correspondingly higher voltage. Similarly, the test signal from the test signal generating device 654 can be injected, for example, at the test plugs 636, 637 on the secondary side of the converter 630. Alternatively, the test signal from the test signal generating device 654 can also be injected at the test plugs 634, 635 on the primary side of the converter 630, as shown by the dashed line, to additionally check the polarity and wiring of the converter 630.

[0110] The test device 650 further includes a plurality of acquisition devices for acquiring measurement signals. In Figure 6 the example of, the test device 650 includes two acquisition devices 651 and 653, which are respectively coupled to the first and second circuits 601, 602 through corresponding lines. For example, the acquisition device 651 can be coupled to the test plugs 618, 619 at the test switch 611 to acquire the voltage on the test switch 611 as a measurement signal. As an alternative, as shown by the dashed line, the acquisition device 651 can be connected to the test plugs 616, 617 to acquire the voltage on the secondary side of the converter 610, or connected to the current clamp 620 to acquire the current passing through the wiring 612. In the same way, the acquisition device 653 can be coupled to the second circuit 602. As Figure 6 shown, the acquisition device 653 can be coupled to the test plugs 638, 639 at the test switch 631 to acquire the voltage on the test switch 631 as a measurement signal. As an alternative, the acquisition device 653 can be coupled to the test plugs 636, 637 to acquire the voltage on the secondary side of the converter 630, or connected to the current clamp 640 to acquire the current passing through the wiring 632.

[0111] The test device 650 further includes a processing device 655, which is shown as a separate component in Figure 6 . In other examples, the processing device 655 can also be designed to 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 controller, such as a microprocessor controller, which can, for example, execute a computer program. As will be described in detail below, the processing device 655 can be coupled to the test signal generation devices 652, 654 and the acquisition devices 651, 653 to drive them in a coordinated manner. 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 test signals independently of any control of the processing device 655. The test signal generation devices 652, 654, the acquisition devices 651, 653, and the processing device 655 do not have to be formed in the same housing or a single unit, but can include spatially independent units with their own housings. For example, the test signal generation devices 652, 654 can each form a unit that can operate and be set independently. Another unit can include the acquisition devices 651, 653 and the processing device 655 and be coupled to the test signal generation devices 652, 654. Thus, even in a large electrical device where the injection point is far from the measurement point, the test device 650 can be used without the need for a corresponding long line between the test signal generation devices 652, 654 and the corresponding injection point.

[0112] As described above with reference to Figures 1 to 5As described in detail, the test device 650 operates in a manner that basically corresponds to the operation of the test device 150. As described above, Figure 2 the method 200 shown in

[0113] p In step 202, two test signals are generated in this case. A separate test signal P p (t) is generated for each of the circuits 601, 602, the test signal having a waveform that is asymmetric in the time domain and a combination of predefined harmonics, the combination of predefined harmonics having at least one higher harmonic. The flag p indicates the circuit to which the test signal P

[0114]

[0115] Here, A represents the amplitude of the entire signal, k represents the number of harmonics used, and f g represents the fundamental frequency of the signal. The term weights the individual sine functions so as to approximate a sawtooth waveform overall.

[0116] For example, a signal with A = 1, k = 3, and f g = 52.6 Hz can be formed. In other examples, A can also be selected such that the root mean square (RMS) of the signal is approximately 1.

[0117] Each of the two test signals P p (t) also includes at least one higher harmonic, where the phase of the at least one higher harmonic is different in the different test signals. In the example described below, the at least one higher harmonic includes only one higher harmonic, namely the fourth harmonic. Thus, the test signals are encoded. For example, this encoding can represent circuit information in the electrical system 600 having two circuits 601 and 602, identifying the circuit to which the test signal is assigned.

[0118] To encode circuit information into a sawtooth signal, the phase of the fourth harmonic is slightly changed while the fundamental, second, and third harmonics remain unchanged. Overall, to limit the bandwidth of the test signal, only five harmonics are used. The following equation gives the definition of the modified test signal y(t) that includes four harmonics (k = 4).

[0119]

[0120] The phase change used can be represented by introducing a phase modifier P[4] for the fourth harmonic. For example, this can have two specific values, such as represented as -1 and +1. The assignment of used in the above equation is, for example:

[0121]

[0122] For P[4] = 1, and for P[4] = -1,

[0123] With Figure 1 a description similar to the example given, each value of the phase modifier P[4] represents a code word here. For example, P[4] = 1 is code word CW1 and P[4] = -1 is code word CW2.

[0124] In step 204, as described above, the generated test signal is injected into circuits 601 and 602. The test signals can be injected simultaneously. The test signal injected in this way passes through electrical components, which include, for example, one or more transformers or capacitors or other electrical engineering equipment, such as circuit breakers or test switches. Based on the injected test signal, an output signal is generated at the above-mentioned measurement points. When the electrical components are correctly connected, for example, it is expected that the test signal injected into circuit 601 will be output basically at the test plugs 618 and 619 of test switch 611. For example, in the case of injecting test plugs 614 and 615, the voltage will change. However, it is expected that the waveform will remain basically unchanged. Similarly, when the electrical components are correctly connected, for example, it is expected that the signal injected into circuit 602 will be output basically at the test plugs 638 and 639 of test switch 631.

[0125] In the case of incorrect wiring, for example, the lines of the first circuit 601 and the lines of the second circuit 602 are connected in the wrong way. On the contrary, the signal injected into the first circuit 601 may exist in the second circuit 601, and / or the signal injected into the second circuit 602 may also exist in the first circuit 601.

[0126] In step 206, as described above for example, a plurality of measurement signals are acquired at test switches 611 and 631. The plurality of measurement signals can be acquired simultaneously or sequentially. In acquisition devices 651, 653, the acquired measurement signals can optionally be pre-processed (e.g., by filtering).

[0127] In step 208, the assignment between the test signal and the measurement signals is determined. In other words, in step 208, the test signals are identified in the measurement signals. Each test signal can be identified in the measurement signals by a filter or a discrete Fourier transform for the fourth harmonic, as described in the example in conjunction with Figure 1 above.

[0128] Based on the assignment between the test signals and the measurement signals determined in step 208, it can be easily determined whether the expected test signals are acquired at the corresponding test plugs 618, 619, 639, and 639. If the assignment does not meet the expectation, incorrect wiring may be determined.

[0129] In step 210, the polarities of the measurement signals acquired at test plugs 618, 619, 638, and 639 are determined. As described above with reference to Figure 1 electrical device 150, the polarity is detected based on an asymmetric waveform in the time domain.

[0130] In step 212, the circuit assignment and the polarity determined in this way can be output, for example, on a display device for the user.

[0131] Alternatively or additionally, in step 214, the detected circuit assignment can be compared with a target assignment, and / or the detected polarity can be compared with a target polarity. If a deviation between the detected state and the target state has been determined, a warning can be automatically output.

[0132] In summary, the above different test signals can quickly and reliably check the wiring of the electrical device. The test signals have a combination of an asymmetric waveform in the time domain and predefined harmonics, the combination of the predefined harmonics having at least one higher harmonic, wherein the amplitude and / or phase of at least one higher harmonic of the plurality of test signals are different. Since the test signals are not affected by direct current, no saturation effect occurs, for example, in a transformer or a capacitor, so the test signals can be transmitted through the converter without problems. In addition, the test signals allow detection of polarity errors and clear differentiation of the individual phases. The threshold value used here to identify the higher harmonics can be selected relative to the fundamental wave, and thus is independent of the absolute amplitude of the signal. Therefore, the method is also applicable to partial signals, which may occur due to current distribution or in the case of an unwanted ground connection.

[0133] All different test signals and their linear combinations have the same asymmetry characteristics in the time domain and can therefore be reliably assigned to polarities.

[0134] Using additional harmonics and / or additional different amplitudes allows for discrimination between more than three phases. This enables, for example, simultaneous discrimination between additional phases, such as in a 2x 3-phase system, or the use of a coding with a Hamming distance greater than 1 to increase the robustness against amplitude errors.

Claims

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

2. The method of claim 1, wherein the plurality of test signals (160-162) are injected into a plurality of first connections (142-144) simultaneously.

3. The method according to claim 1 or 2, wherein the at least one high-order harmonic comprises a fourth harmonic and / or a fifth harmonic. 4 . The method according to claim 1 , wherein the combination of predefined harmonics comprises, in addition to the fundamental wave, at least a second harmonic and / or a third harmonic.

5. The method according to one of the preceding claims, wherein the fundamental wave of the predefined harmonics has a frequency which is not equal to the power supply frequency of the electrical device. 6 . The method according to claim 1 , wherein the fundamental frequency of the predefined harmonics has a frequency of 50 to 60 Hz, optionally 51 to 55 Hz, and again optionally 52.6 Hz.

7. The method according to claim 1 , wherein the at least one higher harmonic comprises a fourth and a fifth harmonic, wherein the fourth harmonic has an amplitude factor of 1.35 / 16 or 1 / 16 or 0.65 / 16 relative to the amplitude of a fundamental wave of the predefined harmonic, and the fifth harmonic has an amplitude factor of 1.5 / 25 or 1 / 25 or 0.5 / 25, wherein the amplitude of one of the other n higher harmonics of the predefined harmonic has an amplitude factor of 1 / n relative to the amplitude of the fundamental wave of the predefined harmonic. 2 The amplitude factor.

8. The method according to claim 1 , wherein the at least one higher harmonic comprises a fourth and a fifth harmonic, 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 the phase of the fundamental wave of the predefined harmonic.

9. The method according to any one of the preceding claims, further comprising: - at a second point (145) of the electrical device (100), a plurality of measurement signals are acquired (206) at a plurality of second connections (146-148) assigned to the plurality of electrical circuits.

10. The method according to claim 9, further comprising: - Based on the injected test signals (160-162) and the acquired measurement signals, determining (208) a distribution between first connections of a plurality of first connections (142-144) and second connections of a plurality of second connections (146-148), respectively.

11. The method of claim 10, wherein determining (208) an allocation comprises: - determining the amplitude and phase of spectral components of predefined harmonic frequencies in the measurement signal, and - Comparing the amplitude and phase of the spectral component to an amplitude threshold or a phase threshold. 12 . The method of claim 11 , wherein the amplitude threshold is set based on the amplitude of a fundamental wave of a predefined harmonic.

13. The method according to any one of claims 10 to 12, further comprising: - outputting to a user the allocation between the first connections of the plurality of first connections and the second connections of the plurality of second connections, respectively, and / or - comparing the assignment between the first connections of the first plurality of connections and the second connections of the second plurality of connections respectively with a predefined assignment between the first connections of the first plurality of connections and the second connections of the second plurality of connections respectively.

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

15. The method according to claim 9 and claim 14, further comprising: - determining (210) the polarity of the acquired measurement signal in order to test the wiring of the electrical device according to the determined polarity.

16. The method of claim 15, wherein determining (210) the polarity of the acquired measurement signals for respective ones of the acquired measurement signals comprises: - determining the derivative of the corresponding measurement signal, - generating a comparison signal by comparing the derivative with a threshold value, - determining the average value of the comparison signal, and - Determining the polarity of the corresponding measurement signal based on the average value of the comparison signal.

17. The method of claim 15, wherein determining (210) the polarity of the acquired measurement signals for respective ones of the acquired measurement signals comprises: - determining a correlation factor based on the corresponding measurement signal and the asymmetric waveform in the time domain, and - Determining the polarity of the corresponding measurement signal based on the correlation factor.

18. A testing device for testing the wiring of an electrical device having a plurality of circuits, comprising: - a test signal generating device (152) configured to generate a plurality of test signals (160-162), wherein each of the plurality of test signals (160-162) has a combination of predefined harmonics, the combination of predefined harmonics having at least one higher harmonic, wherein the amplitude and / or phase of at least one higher harmonic of the plurality of test signals (160-162) are different, and - an injection device (154) configured to inject the plurality of test signals (160-162) into a plurality of first connections (142-144) assigned to a plurality of circuits at a first point (141) of the electrical device (100), wherein a different test signal of the plurality of test signals (160-162) is injected into each first connection of the plurality of 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 testing device according to claim 18 or 19, further comprising: - acquisition means (156) configured to acquire, at a second point (145) of the electrical device (100), a plurality of measurement signals at a plurality of second connections (146-148) assigned to the plurality of electrical circuits.

21. The testing device according to claim 20, further comprising: - a processing device (158) configured to determine, based on the injected test signals (160-162) and the acquired measurement signals, an allocation between first connections of the plurality of first connections (142-144) and second connections of the plurality of second connections (146-148), respectively.

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.

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