METHOD FOR DETECTING UNSYMMETRICAL OSCILLATIONS DURING THE OPERATION OF AN ELECTRICAL DEVICE CONNECTED TO A HIGH-VOLTAGE NETWORK

Description

[0001] The invention relates to a method for detecting asymmetrical vibrations during the operation of an electrical device connected to a high-voltage network.

[0002] In electrical transformers, such as those used in power transmission and distribution networks, an unwanted direct current (DC) can be injected into the windings. Power electronic components in the network, such as the control of electric drives, converters for flexible AC transmission systems, or high-voltage direct current transmission, can also cause DC currents in electrical devices. Another cause of DC currents can be so-called "geomagnetically induced currents" (hereinafter also referred to as GIC).

[0003] A direct current component in the transformer core results in a magnetic flux component that is superimposed on the alternating flux. This leads to an asymmetrical excitation of the magnetic material in the core, which brings with it a number of disadvantages. Even a direct current of a few milliamperes leads to saturation of the core with magnetic flux. This is associated with a significant increase in core losses (e.g., 20-30%). Heating problems can occur, especially with large GICs. Furthermore, increased noise emissions occur during operation, which is perceived as particularly disturbing when the transformer is installed near a residential area.

[0004] Various active and passive devices are known for DC compensation or reduction of the operating noise of a transformer as an electrical device. However, before undertaking costly DC compensation measures, it should be ensured whether such a DC component is actually present. It is known that during the operation of an electrical device, such as a transformer, DC components flowing within the transformer lead to asymmetrical vibrations of the transformer.

[0005] DE 10 2017 217 530 A1 relates to an electrical device for connection to a high-voltage network with a fluid-tight tank filled with an insulating fluid and in which a core partially enclosed by a winding is arranged, a cooling unit connected to the tank, and a pump for circulating the insulating fluid of the tank via the cooling unit.

[0006] WO 2019 / 166 396 A1 concerns audio- and vibration-based systems and methods for monitoring the condition of power distribution systems. The system consists of an IAA device and a sensor unit. The IAA device, with computer-executable commands such as an audio data processing algorithm, is configured to detect and predict impending anomalies in one or more power distribution systems.

[0007] US 2017 / 227592A1 concerns a system for online bushing monitoring and geomagnetically induced current (GIC) monitoring that uses a Hall-effect current transformer and obtains the harmonic component of the signals by measuring the bushing test tap current. This is a more reliable measurement method because bushings form a capacitive voltage divider that is not subject to saturation, a disadvantage of using current transformers to obtain the signals. The system combines the existing harmonic analysis capabilities of the bushing monitoring measurement system with the measured neutral DC current to create an economical and efficient system that monitors both bushing condition and GIC conditions with a single monitoring module.

[0008] KR 2017 0053304 A relates to an acoustic spectral detector for detecting transformer abnormalities. This includes a spectrum classification unit for receiving an acoustic detection signal generated in the transformer and for analyzing a spectrum of the detection signal to generate spectrum classification information. It also includes a spectrum signal accumulation storage unit for accumulating and storing the spectrum signals, and a spectrum level comparison unit for comparing the spectrum signal of a preset time and the recently stored spectrum signal among the spectrum signals stored in the spectrum signal accumulation storage unit to generate comparison information.

[0009] EP 3 591 790 A2 relates to a method for characterizing energy quality events in an electrical system comprising the derivation of electrical measurement data for at least a first virtual counter in an electrical system from (a) electrical measurement data of or derived from energy-related signals acquired by at least a first IED in the electrical system, and (b) electrical measurement data of or derived from energy-related signals acquired by at least a second IED in the electrical system.

[0010] WO 2019 / 201 451 A1 concerns an electrical device for connection to a high-voltage network with a magnetizable core, at least one winding designed to generate a magnetic field in the core, and a group of measuring sensors that provide measurement signals on the output side.

[0011] DE 20 2018 004 493 U1 relates to an electrical device for connection to a high-voltage network comprising: a magnetizable core, at least one winding configured to generate a magnetic field in the core, and a group of measuring sensors that provide measurement signals on the output side. At least one communication unit is provided with a housing containing a GSM module and several analog and several digital measurement inputs, wherein several measuring sensors are connected to one communication unit and the respective communication unit is configured to process the measurement data obtained from the various measurement signals.

[0012] Adnan Secic et al.: "Vibro-Acoustic Methods in the Condition Assessment of Power Transformers: A Survey", IEEE Access, Vol. 7, January 1, 2019, pages 83915-83931, addresses the categorization and review of the state of the art in vibroacoustic diagnostic methods for power transformers. Continuous condition monitoring is presented, along with an overview of the causes of transformer vibrations and the acquisition and preprocessing of diagnostic data. Feature extraction in the time, frequency, and time-frequency domains, as well as mathematical modeling and system identification of dynamic systems, are also discussed.

[0013] WO 2017 / 194 349 A1 concerns a method for monitoring the commissioning and plausibility of data of a power measurement sensor in a distribution network with a computer unit that is equipped with a topology model of the monitored distribution network, that is equipped with a communication device for wireless communication with mobile devices, and that automatically detects newly added sensors in the distribution network and enters into a data exchange with the new sensor.After detecting a new power measurement sensor in the distribution network, the computer unit performs a plausibility check of the measurement data of the new power measurement sensor based on measurement data from existing power measurement sensors in the distribution network. If the measured values ​​of the new power measurement sensor are implausible, the computer unit issues a message to manually change the physical sensor connection in the distribution network, or correct the data of the new power measurement sensor, or assign the new power measurement sensor to a different distribution network.

[0014] The object of the invention is therefore to create a method of the type mentioned above with which it can be determined simply, quickly and safely whether the electrical device oscillates asymmetrically when operating in a high-voltage electrical supply network.

[0015] The invention solves this problem through the features of claim 1.

[0016] According to the invention, it is possible to quickly, easily, and with a high degree of certainty to determine whether asymmetrical vibrations occur in an electrical device, such as a power transformer, during operation. Previously, the detection of asymmetrical vibrations required complex electrical measurements or acoustic measurement series on the electrical device. The analysis of the measurement data had to be performed by experts. In other words, the known methods were very expensive. The method according to the invention, however, is not only cost-effective but can also be easily initiated without requiring any specialized knowledge. It can therefore be carried out by any user, for example, the operators of the electrical device. If asymmetrical vibrations are detected, suitable measures can be taken to suppress them.

[0017] During operation, the electrical device is connected to a high-voltage network, as described in the invention. The electrical device is therefore designed for high voltages between 1 kV and 1300 kV and is, for example, a transformer, particularly a power transformer, or an inductor. Such a transformer or inductor preferably has a tank filled with an insulating fluid. An active component is arranged in the tank, comprising a magnetizable core and at least one winding. At least one winding is connected to the alternating current high-voltage network during operation. An ester liquid or a mineral oil, for example, can be used as the insulating fluid. Besides providing electrical insulation of the active component from the tank, which is at earth potential, it also serves to cool the components.

[0018] In contrast, the electrical device is, for example, a cast resin or dry-type transformer. The windings of a dry-type transformer are arranged in a resin block or film. The resin serves as a solid insulator. A tank filled with insulating fluid is not used in a dry-type transformer.

[0019] Mathematically, the inventive method for detecting asymmetrical oscillations can be described as follows. SxN is the signal value of the frequency spectrum in arbitrary units, where x represents even (x=g), odd (x=u), or noise (x=n). N is the order number of the signal, where N=1 corresponds to the fundamental frequency and N=2, 3, 4, ... , Nmax to the harmonic overtones. Even frequencies fgN result from a supply voltage of 50 Hz according to fgN = 50 * 2 * N. Odd frequencies result from fuN = 50 * (2 * N + 1). A DC component in the electrical device causes an additional odd component to the total spectrum. If the sum of all odd components of the total spectrum is now set in the ratio R to the even components of the total spectrum, and this ratio R exceeds a previously defined threshold value, the presence of asymmetrical oscillations can be concluded.The value of R indicates the effect of asymmetrical vibrations on the core. Asymmetrical vibrations may indicate a DC component flowing through the electrical device.

[0020] According to the invention, the communication unit has, for example, at least one analog and at least one digital input. This allows multiple sensors to be connected to a single communication unit. Not all sensors need to be acoustic sensors; the communication unit can also be connected to current, voltage, temperature, or pressure sensors. The communication unit includes, for example, a main processor and a secondary processor, as well as a storage unit in which pre-processed measured values ​​or derived values ​​can be stored and processed, e.g., by averaging. The measured values ​​from various sensors can therefore be transmitted together from a single communication unit to the data processing cloud via a long-range communication link.

[0021] The user of the method according to the invention is, for example, an operator of an energy supply network who is responsible for a number of transformers, circuit breakers, capacitor banks, spark gaps or the like.

[0022] Within the scope of the invention, any sensor capable of detecting vibrations or oscillations of the electrical device at the input side and providing electrical signals at the output side, depending on the amplitude of these vibrations, qualifies as an electrical vibration transducer, or in other words, a sensor. These electrical signals are referred to here as measured values. The electrical signals can be analogous electrical signals, for example, an electric current or a voltage whose magnitude corresponds to the amplitude of the received sound wave. However, within the scope of the invention, the measured values ​​can also be digital values, which are generated, for example, by sampling the analog signals to obtain sample values ​​and then digitizing these sample values.

[0023] Within the scope of the invention, each vibration sensor is connected to the communication unit via a short-range communication link. This short-range communication link can be, for example, a simple cable. Alternatively, the short-range communication link can be, for example, a ZigBee, Bluetooth, wireless, Ambus, or WiFi connection. The short-range communication link extends a maximum distance of 100 meters.

[0024] The connection between the communication unit and the data processing cloud is established via a long-range communication link within the scope of the invention. To establish this link, the communication unit has a long-range communication device, such as a mobile communication module based on the GPRS or UMTS standard. This device establishes a long-range communication link, preferably an IP-based data connection, with the data processing cloud. A mobile network operator or telecommunications provider can be interposed, and the long-range communication link can be established at least partially via that provider's communication network and / or at least partially via the internet. Establishing the connection then requires only minimal configuration and parameterization effort.Apart from configuring the long-range communication equipment with the information necessary to establish the long-range communication connection, e.g., installing a SIM card from a telecommunications provider, no further effort is required for the individual communication unit.

[0025] In this context, a cloud or data processing cloud is understood to be an arrangement comprising one or more data storage devices and one or more data processing devices, which can be configured through appropriate programming to perform any data processing operations. The data processing devices are typically universal data processing devices, such as servers, which initially have no specific design or programming requirements. Only through programming can the universal data processing device be enabled to execute specific functions.

[0026] If the cloud comprises multiple individual components, these are interconnected for data communication in a suitable manner, for example, via a communication network. Any type of data can be supplied to a data processing cloud for storage and / or processing. The data processing cloud itself then makes the stored data and / or the events of the data processing performed available to other devices, such as computer workstations, laptops, and smartphones connected to the data processing cloud. A data processing cloud can be provided, for example, by a single data center or by multiple networked data centers. Typically, a data processing cloud is located remotely from the high-voltage equipment.

[0027] The electrical device, as described in the invention, is designed for operation in a standard or high-voltage network, i.e., for an operating voltage between 1 kV and 1200 kV, in particular between 50 kV and 800 kV. The high-voltage network is preferably an AC network.

[0028] According to the invention, an electrical device, for example a transformer, in particular a power transformer, is a choke or the like.

[0029] In one variant of the method according to the invention, the communication unit is a mobile phone. A so-called "smartphone" is particularly well suited as a mobile phone. Here, a smartphone is understood to be a high-performance mobile phone. Such mobile phones are usually already equipped with a microphone as an acoustic sensor. Furthermore, such a mobile phone has memory and a programmable unit, for example, at least one processor. However, the entire mobile phone is not used here to carry out the method according to the invention.

[0030] It serves, firstly, to connect to the data processing cloud. The mobile phone uses its microphone to record the sounds of a transformer and stores the resulting measurements on its memory unit. At predetermined time intervals, a connection is established with the data processing cloud, to which the measurements are sent individually or as averages.

[0031] In a particularly preferred embodiment, the communication unit is a communication box. The communication box is, for example, attached to the electrical device. In particular, the communication box is attached to an outer wall of the electrical device. The communication box is thus accessible from the outside.

[0032] In one variation of the method, the measured values ​​from several vibration sensors are transmitted together to the data processing cloud. However, the measured values ​​can be pre-processed beforehand, for example, averaged over a measurement period.

[0033] Advantageously, the mobile phone has a separate communication unit and a storage unit on which the measured values ​​or values ​​derived from the measured values ​​are stored. This storage unit simplifies any desired preprocessing of the measured values.

[0034] Preferably, the vibrations are recorded at various locations on the electrical device. For this purpose, the user records the vibrations of the electrical device at different points on its surface. Subsequently, an average value is calculated for all frequency components from the respective spectra obtained. Preferably, software guides the user interactively through this process, ensuring that the correct steps are performed at the right time.

[0035] Advantageously, the vibrations are recorded over a predetermined period of time. This period is preferably between 10 and 60 seconds for each measurement.

[0036] In an advantageous embodiment of the invention, the geographical location of the respective communication unit and the associated electrical device is determined by means of a position-finding antenna arranged in the communication unit and transmitted to the data processing cloud.

[0037] In a further advantageous embodiment of the invention, the acoustic signals are detected at points (A, B, C, D) on the electrical device. For this purpose, the vibration sensors are permanently installed in the electrical device.

[0038] Further advantageous embodiments and benefits of the invention are the subject of the following description of exemplary embodiments of the invention with reference to the figure of the drawing, wherein the same reference numerals refer to components that act in the same way and wherein Figure 1 schematically illustrates an embodiment of the method according to the invention and Figure 2 schematically illustrates a further embodiment of the invention.

[0039] Figure 1 Figure 1 shows an embodiment of the method according to the invention, in which a transformer 1 is schematically illustrated as an electrical device. The transformer 1 has a tank 2 filled with an insulating fluid such as an ester liquid or a mineral oil. A magnetizable core 3 is arranged in the tank 2, forming a closed magnetic circuit. The legs of the core 3 are each enclosed by two concentrically arranged windings, of which only the outer high-voltage winding 4 is visible. The windings are each connected to the phases of an alternating current high-voltage network via bushings 5.

[0040] An expansion vessel 6 serves to compensate for temperature-related volume fluctuations of the insulating fluid in the tank 2 of the transformer 1. A Buchholz relay 7 can be seen in the connecting line between tank 2 and expansion vessel 6.

[0041] Figure 1Figure 8 further shows a vibration sensor 2, depicted only schematically, which detects the vibrations of the transformer 1 at two different locations A and B. The vibration sensor 8 is connected via a Bluetooth connection 11 as a short-range communication link to a communication unit 12, here a communication box. The communication box 12 is permanently mounted on the outside wall of the tank 2. It has a storage unit on which the measured values ​​supplied by the vibration sensor 8 are stored with spatial resolution. Every 2 minutes, the communication box 12 connects to a data processing cloud 9 via a long-range communication link 13 and sends the measured values ​​stored on its hard drive to the data processing cloud 9 via the long-range communication link 13. The data processing cloud 9 performs the analysis procedure described above to detect asymmetrical vibrations of the electrical device 1.

[0042] The data processing cloud 9 features software that performs a Fourier transform on the transmitted measured values. This is followed by the calculation of the ratio R, as described above. From the value of R, the inventive method determines whether, and if so, to what extent, asymmetrical vibrations are present and, if so, to what order of magnitude the transformer is subjected to a DC component. The user thus gains certainty about the DC component based on the result of the method and can then initiate appropriate countermeasures to suppress any DC component that may be detected.

[0043] The data processing cloud can be accessed with a laptop or computer 10 to obtain the results of the analysis.

[0044] Figure 2Figure 1 shows a further embodiment for carrying out the method according to the invention; a transformer 1 is again recognizable as an electrical device, which corresponds to the one described in Figure 1. Figure 1 The transformer shown essentially corresponds to the one shown. In contrast to the one in Figure 1 The transformer shown has transformer 1 according to Figure 2 However, four vibration sensors 8 are arranged inside the tank 2. Each vibration sensor 8 is connected via a short-range communication link 11, again a Bluetooth connection, to a communication unit 12, which in the illustrated embodiment is not permanently attached to the transformer 1. Rather, the communication unit 12 is located in a nearby housing (not shown) approximately 20 m away from the transformer 1.

[0045] The communication unit 12 has four inputs, allowing all four sensors 8 to be connected to it simultaneously. The vibrations generated during the operation of the transformer 1 are detected by the sensors 8, which generate an analog electrical signal, in this case a current, depending on the amplitude of the vibrations. The analog signals are sampled, and the resulting samples are digitized. These digitized values ​​are referred to here as measured values.

[0046] The aforementioned measured values ​​are transmitted to the communication unit 12 via the short-range communication link 11. This unit has a storage unit (not shown) on which the measured values ​​are stored.

[0047] In one variant of the method according to the invention, the measured values ​​are preprocessed; for example, the measured values ​​transmitted at 2-second intervals are averaged over a period of 2 minutes, and the averaged values ​​are stored on the storage unit. Every 2 minutes, the communication unit 12 establishes a connection with the data processing cloud 9 via a long-range communication link 13. The measured values, the averaged measured values, or values ​​derived from the measured values ​​are transmitted to the data processing cloud 9. This cloud then uses suitable software to analyze the measured values; in other words, a Fourier transform is performed, and the resulting spectrum is examined for the presence of asymmetrical oscillations. The analysis method is described in more detail above.

Claims

1. A method for detecting asymmetrical vibrations of a transformer or a choke (1) during operation of the transformer or the choke (1) connected to a high voltage grid, in which - vibrations arising when operating the transformer or the choke (1) are measured by means of multiple vibration sensors (8) that are arranged at different points (A, B, C, D) of the transformer or the choke (1), which provide measurement values on the output side, - the measurement values and / or the values derived from the measurement values are transmitted, via a short-range communication link (11), to a communication unit (12), - the measurement values and / or the values derived from the measurement values are transmitted, via a long-range communication link (13), by the communication unit (12) to a data processing cloud (9), - the measurement values and / or the values derived from the measurement values are split into their frequency parts by the data processing cloud (9) by means of a Fourier transformation, obtaining a frequency spectrum, - depending on a fundamental frequency of the high-voltage supply grid, even and odd frequency parts of the frequency spectrum are determined and put into a ratio R to one another, - the presence of asymmetrical vibrations is inferred if the ratio R exceeds a predetermined threshold value.

2. The method according to claim 1, characterised in that each communication unit (12) has a memory unit on which measurement values and / or values derived from the measurement values are stored.

3. The method according to claim 2, characterised in that by means of an antenna for position determination, arranged in a communication unit (12), the geographical position of the respective communication unit (12) and of the transformer or choke (1) connected to it is determined and transmitted to the data processing cloud (9).

4. The method according to any one of claims 2 or 3, characterised in that the communication unit is a mobile phone (8, 12).

5. The method according to any one of the preceding claims, characterised in that the vibrations are measured over a preset period of time.

6. A computer program for a computing device, characterised in that it is suitable for carrying out the method according to any one of claims 1 to 5.

7. A storage medium, characterised in that a computer program according to claim 6 is stored thereon.