Oil-immersed transformer having an oil conservator

Abstract

The invention relates to an oil-immersed transformer comprising a transformer tank, an oil conservator, a flow channel which connects the transformer tank to a first opening in the oil conservator, a cell for receiving oil, means for conveying oil from the oil conservator into the cell, an antenna for supplying a measurement signal to the oil in the cell, and a sensor that is electrically connected to the antenna for the purpose of measuring the quality of the oil of the oil transformer.

Description

[0001] Oil transformer with an oil conservator

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to an oil transformer having an oil conservator and a technique for measuring oil quality of an oil transformer including an oil conservator.

[0004] BACKGROUND

[0005] Oil-immersed electrical transformers are power transformers typically used in power distribution networks. Such oil-immersed transformers are known, for example, from DE202008017356U1. Oil-immersed transformers comprise an oil-filled transformer tank in which the transformer core with primary and secondary windings is located. For insulation, the primary and secondary windings can be wrapped with cellulose paper. The oil serves as an electrical insulation medium and as a cooling medium for dissipating heat loss generated during transformer operation. Depending on the operating oil temperature, the oil expands and contracts in volume. This is also referred to as the "breathing" of the oil-immersed transformer.

[0006] Oil-immersed transformers usually include an oil conservator located above the transformer tank and connected to the tank via a flow channel. The oil conservator can be used to compensate for changes in the oil's volume. The oil conservator serves to accommodate the oil volume that arises due to thermal expansion of the oil during temperature fluctuations in the transformer caused by load changes or changes in the ambient temperature. An air-filled, compressible diaphragm can be arranged inside the oil conservator. Depending on the expansion state of the oil in the transformer, the diaphragm is compressed, with the interior of the transformer tank, the oil conservator, and the flow channel forming a closed system. A magnetic oil level indicator (MOG) can be used to monitor the oil level in the oil conservator.

[0007] As the oil-immersed transformer ages, the oil becomes contaminated by moisture and fibrous materials in the winding insulation. Dissolved gases produced by chemical reactions in the oil can also contaminate the oil. To ensure safe operation and avoid interruptions or power outages, the oil must be checked regularly and replaced if necessary.

[0008] Oil monitoring is typically performed in one of the following ways: An oil sample is manually taken from the transformer and sent to a laboratory for analysis. The laboratory then tests the oil's insulation resistance and dielectric breakdown voltage. Furan analysis can also be performed in the laboratory. Alternatively, the oil can be analyzed at regular intervals using a measuring device. Gas chromatography can be used for this purpose, but this has the disadvantage of being time-consuming and costly and must be performed by a specialist. Photoacoustic spectroscopy can also be performed.

[0009] Known techniques for monitoring the oil in an oil-immersed transformer also have the following disadvantages: some techniques cannot be retrofitted and require relatively high personnel expenditures for the installation and configuration of the measuring devices. It is often also necessary for the transformer to be shut down and shut down during the installation of the measuring devices. Furthermore, known measuring techniques can be affected by electromagnetic pulses. For example, measuring sensors attached directly to the surface of the transformer's main tank can be affected by partial discharges. Such partial discharges can generate electromagnetic pulses in the ultra-high frequency range (300 MHz to 3 GHz), which can lead to measurement errors or inaccuracies in the measuring devices. The ambient and / or surface temperature of the transformer can also cause problems.Electronic measuring devices operating near the leg and yoke areas of the transformer, for example, are exposed to high temperatures (oil temperature rise due to high-voltage loads). The increased temperature can cause the measuring devices to malfunction, leading to measurement errors or inaccuracies, or even measuring device failure. Measuring devices that collect oil samples from an outlet valve at the bottom of the oil-immersed transformer main tank may also be mixed with contaminated particles. Fibers and moisture from the insulating materials can combine with the oil and cause residues to settle at the bottom of the transformer. Oil samples taken in this area are often contaminated with residues, which can lead to inaccurate oil quality analysis. BRIEF SUMMARY

[0010] The present disclosure is based on the object of providing an oil transformer with an oil conservator which enables the oil quality of the oil transformer to be determined in a simple and reliable manner.

[0011] To achieve this object, an oil transformer comprising a transformer tank, an oil conservator, a flow channel connecting the transformer tank to a first opening in the oil conservator, a cell for receiving oil, means for conveying oil from the oil conservator into the cell, an antenna for applying a measuring signal to the oil in the cell, and a sensor electrically connected to the antenna for measuring an oil quality of the oil transformer is proposed.

[0012] The oil-immersed transformer can be any type of oil transformer that has an oil conservator to compensate for volume changes in the transformer oil. The shape of the oil conservator is not limited to any specific form. The oil conservator can be, for example, a cylinder, cuboid, cube, or prism. The oil conservator can be an expansion radiator, an conservator with a nitrogen cushion, or with a rubber bag or rubber membrane. In particular, the oil conservator can contain a compressible membrane that compresses or decompresses depending on the oil level in the oil conservator. The transformer tank, including its core and coils, is located in an oil bath. A Buchholz protective relay can be provided in the flow channel where the transformer tank is connected to the first opening in the oil conservator by the flow channel.Additional components, such as various cavities, may be provided in the flow channel. The transformer tank, the flow channel, and / or the oil conservator may be steel structures.

[0013] Depending on the shape of the oil conservator, the antenna is arranged at appropriate positions outside the oil conservator, on the oil conservator, or at or in a second opening of the oil conservator. The second opening can be a valve opening with a gas release valve (pressure relief valve) arranged therein. The second opening can be arranged at an upper end of the oil conservator or on the side of the oil conservator.

[0014] The antenna is electrically connected to the sensor. To avoid measurement inaccuracies, the antenna can be arranged or attached directly to the oil conservator. The sensor can be arranged remotely from the oil conservator, for example, > 1 m away. The antenna and the sensor can be connected via cable or via wireless interfaces (for example, via Wi-Fi or Bluetooth). The antenna can be a transmitting antenna and a receiving antenna, an integrated transmitting and receiving antenna, or two integrated transmitting and receiving antennas. In particular, the antenna(s) can be designed as Vivaldi antennas. Vivaldi antennas can be used advantageously due to their wide bandwidth, low cross-polarization, and constant group delay. The antenna(s) can also be designed as ultra-wideband (UWB) antenna(s), spiral antennas, or other antenna types.The antenna and the sensor can also be designed as a single unit or module, for example, in a housing. The sensor can further include a communication interface for communicating with a cloud computing device.

[0015] For attaching the antenna, the cells, and the means for conveying oil from the oil expansion tank into the cell, a fastening device can be provided that allows for detachable attachment of the antenna, the cells, and the means for conveying oil from the oil expansion tank into the cell to or in the oil expansion tank. Other fastening methods, such as screws or a magnetic attachment, are also conceivable.

[0016] The sensor can, for example, comprise a baseband transmitter, a baseband receiver, and a digital backend, whereby the oil quality in the oil conservator or the oil transformer can be determined using the signals generated by the baseband transmitter and the signals received by the baseband receiver. The oil quality can be quality characteristics defined in the IEC 60422 standard. In particular, the sensor is configured to use the received measurement signals to obtain information regarding the color, water content, and / or acidity of the oil, based on which a statement can be made about the quality of the oil in the oil transformer. For example, the signals are used to determine the refractive index and / or loss factor of the oil. The sensor can thus be a non-contact near-field sensor for dielectric spectroscopy.The sensor can also be configured to perform broadband dielectric spectroscopy (BDS). For example, if the sensor is designed for ultra-broadband impedance spectroscopy, the oil can be exposed to a pulsed alternating current signal. Furthermore, a combined frequency-domain / time-domain technique can be used to characterize the oil. To improve detection accuracy, the sensor can generate a baseband signal generated by combining several upconverted Gaussian signals. Additional components, such as amplifiers, oscilloscopes, and a communications interface, can be incorporated into the sensor. The sensor can also be configured to measure temperature, vibration, and / or gas evolution of the oil.

[0017] The sensor can in particular be configured to generate signals, in particular electromagnetic signals, with a frequency of 1 Hz to 3000 GHz and send them to the antenna, which transmits the signals into the oil. Signals with a frequency of 1 Hz to 3000 GHz are then received by the sensor via the antenna. The antenna can thus be designed as a unit with a transmitting and receiving antenna, so that signals sent into the oil are reflected and received again by the antenna. In particular, it can be a transceiver antenna. The signals can in particular be pulsed signals in the picosecond range. The interactions of electromagnetic waves with frequencies of 1 Hz to 3000 GHz have the advantage that they generally do not pose any health risks to humans and yet still deliver good measurement results.

[0018] Even better measurement results can be achieved if the sensor is configured to generate, transmit, and receive signals at a frequency of 3.1 GHz to 10.6 GHz. In particular, the sensor can be configured to operate in the ultra-wideband (UWB) range.

[0019] The cell can be a membrane, for example, a rubber membrane, designed to hold oil from the oil conservator. In particular, the oil can flow through the cell, for example, from the oil conservator into the cell and be analyzed there. Furthermore, after flowing through the cell and being analyzed, the oil can be returned to the oil conservator. Accordingly, the cell can have one or two hose connections.

[0020] The cell can be arranged within the oil conservator above a maximum oil level of the oil conservator. This ensures that the cell does not come into contact with the oil in the oil conservator. Thus, the oil quality of the oil in the oil conservator can be determined with minimal oil contact in the oil conservator. Oil contact in the oil conservator can only occur through the means for conveying oil from the oil conservator into the cell. The oil transformer can further comprise an oil level measuring device for measuring the oil level of the oil conservator. The oil level measuring device can be used, in particular, to determine the maximum oil level of the oil conservator.

[0021] Alternatively, the cell can be located outside the oil conservator at a second opening in the oil conservator. This allows for easy installation and removal of the cell. The second opening can be located at an upper end of the oil conservator. For example, the second opening is located at a highest point of the oil conservator. In this case, the antenna receives reflected signals from the signals emitted into the oil. This can prevent the measurement from being distorted by deposits in the oil at the bottom of the oil conservator. Furthermore, the second opening can comprise a valve. In this embodiment, the antenna and the sensor can be designed as a portable measuring system, which enables simple and non-contact measurement of the oil quality without major installation effort.The portable measuring system may further comprise means for conveying oil from the oil conservator into the cell. The system, consisting of the antenna, sensor, and means for conveying oil from the oil conservator into the cell, is accordingly designed as a measuring system with minimal or reduced oil contact.

[0022] The antenna can be located on the cell. For example, the antenna is glued to the outside of the cell. This allows for contactless application of measurement signals to the oil in the cell. The antenna can also be located inside the cell, which allows for even more precise measurement results. The antenna can, for example, have a meander shape. Thus, the antenna can be designed as a combined transmitting and receiving antenna, in particular as a transceiver antenna.

[0023] For reliable transmission and reception of signals, the oil-immersed transformer may further comprise an ultra-wideband baseband transmitter, an ultra-wideband baseband receiver, and a digital backend. The digital backend may comprise a processor that executes instructions of a computer program.

[0024] Furthermore, the oil transformer can comprise a computing device connected to the sensor, wherein the computing device is configured to process and visualize the measured values ​​measured by the sensor. For example, a measured frequency spectrum can be displayed. The computing device can be, for example, a laptop or tablet computer. The computing device can be configured to calculate values ​​relating to the color, water content, and / or acidity of the oil based on the measured values ​​measured by the sensor. For example, a fast Fourier transform can be applied to the measured data. Furthermore, the measured data can be extracted and visualized in a computing platform of the computing device, such as MATLAB. The computing device can also be implemented as a cloud computer.

[0025] The oil transformer may further comprise a temperature, gas, and / or vibration sensor. The temperature, gas, and / or vibration sensor may be arranged on or in the oil conservator. In particular, the sensor may be configured to detect abnormalities in the gas generated by the oil transformer. The sensor may also comprise additional sensor and electronic components that monitor regular operation and the condition of the oil transformer.

[0026] The means for conveying oil from the oil expansion vessel into the cell can comprise a hose and / or a pipe arranged at least partially within the oil expansion vessel, having a first end extending into the oil in the oil expansion vessel and a second end connected to the cell, and a pump for pumping the oil from the oil expansion vessel into the cell. The pump is preferably arranged outside the oil expansion vessel. This embodiment allows for oil quality determination with minimal oil contact. If the oil is pumped through the cell, a further hose and / or pipe is provided, which pumps the oil back into the oil expansion vessel and / or a collecting vessel.

[0027] The aspects and variants described above can be combined without this being explicitly described. Each of the described embodiment variants is therefore to be considered optional to each embodiment variant or combinations thereof. The present disclosure is therefore not limited to the individual embodiments and variants in the described order or to a specific combination of the aspects and embodiment variants.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further advantages, details and features of the oil transformers described here will become apparent from the following description of embodiments and the figures.

[0030] Fig. 1 shows a schematic representation of an embodiment of an oil transformer with an oil conservator; and

[0031] Fig. 2 shows a schematic representation of an embodiment of an oil expansion tank with an antenna unit, a sensor and a computing unit; and

[0032] DETAILED DESCRIPTION Fig. 1 shows a schematic representation of an embodiment of an oil transformer with an oil conservator. The oil transformer comprises a transformer tank 10 and an oil conservator 20. A flow channel 30 connects the transformer tank 10 to a first opening 22 in the oil conservator 20. The first opening 22 is arranged at a lower end of the oil conservator 20. The transformer tank 10 includes a corresponding opening. In the transformer tank 10, the transformer 15 is mounted on support blocks 60 in an oil bath 40. The oil conservator 20 is shown in Fig. 1 as an example above the transformer tank 10 in a cylindrical shape. Other shapes (e.g. cuboid, cube or prism) and arrangements (at the same height as the transformer tank 10, further above, etc.) of the oil conservator 20 are conceivable.

[0033] Oil 40 is located in the flow channel 30 and the housing 26 of the oil conservator 20. As described above, the oil conservator 20 serves to absorb oil due to thermal expansion of the oil during temperature fluctuations in the transformer 15, caused by load changes or changes in the ambient temperature. As indicated by the surface 42 of the oil in the oil conservator 20, the oil level in the oil conservator 20 changes accordingly. The oil in the oil conservator 20 compresses a membrane 28 depending on the oil level in the oil conservator 20, which is decompressed again when the oil level 42 drops. A pressure relief valve 50 for discharging excess gas is provided in a second opening 24 at an upper end of the oil conservator 20. Furthermore, the oil transformer comprises an oil level measuring device 25 for measuring the oil level 42 in the oil expansion tank 20.For the sake of clarity, other components of the oil transformer, such as the transformer core, the coils, and a Buchholz protection relay, are not shown in the schematic representation of Fig. 1. As an alternative to the embodiment of the oil conservator 20 with the membrane 28, an oil conservator of the Atmoseal type or another type may also be provided.

[0034] Figure 2 shows a schematic representation of an exemplary embodiment of an oil expansion tank. The oil expansion tank 20 is the oil expansion tank 20 shown in Figure 1, with the same reference numerals in Figures 1 and 2 referring to the same elements.

[0035] The arrangement shown in Fig. 2 comprises a cell 55 for receiving oil 40 from the oil expansion vessel 20, means 57, 58 for conveying oil 40 from the oil expansion vessel 20 into the cell 55, an antenna 85 for applying a measurement signal to the oil 40 in the cell 55, a sensor 70 electrically connected to the antenna 85 for measuring an oil quality of the oil transformer, and a computing device 90. The means 57, 58 for conveying oil 40 from the oil expansion vessel 20 into the cell 55 comprise a hose 57 arranged at least partially in the oil expansion vessel 20, having a first end extending into the oil 40 in the oil expansion vessel 20 and a second end connected to the cell 55, and a pump 58 for pumping the oil 40 from the oil expansion tank 20 into the cell 55. The hose 57 extends through the opening 24, with the cell 55 being arranged outside the oil expansion tank 20 at the opening 24.

[0036] In Fig. 2, a minimum oil level 42 is shown in the oil expansion tank 20, wherein the hose 57 is designed such that the first end of the hose 57 always extends below the minimum oil level 42.

[0037] The pump 58 pumps oil 40 from the oil expansion tank 20 into the cell 55. It is also conceivable for the pump 58 to pump the oil 40 through the cell 55, i.e., the oil 40 is returned to the oil expansion tank 20. The pump 58 is designed as an electric pump and is electrically connected to the antenna 85. The pump 58 is arranged near the antenna 85.

[0038] According to an alternative embodiment (not shown), the cell 55 is arranged in the oil expansion vessel 20, in particular above a maximum oil level of the oil expansion vessel 20.

[0039] The antenna 85 is mounted on an outer wall of the cell 55 and electrically connected to the sensor 70. In this embodiment, the antenna 85 is designed as a meander-shaped transceiver Vivaldi antenna.

[0040] Opposite the underside 21 of the oil expansion tank 20, at an upper end of the oil expansion tank 20, is the opening 24, which is closed by a pressure relief valve 50. The antenna 85, which is electrically connected to the sensor 70, is arranged above the opening 24.

[0041] The sensor 70 comprises a baseband transmitter 71, a baseband receiver 72, and a digital backend 73, and is electrically connected to a computing device 90 via a cable. The baseband transmitter 71 generates pulsed excitation signals for the antenna 85, with reflected signals being forwarded to the baseband receiver 72. The digital backend 73 controls the transmission and reception of the signals by the baseband transmitter 71 and the baseband receiver 72. The sensor 70 is configured to transmit and receive pulsed signals with a frequency of 1 Hz to 3000 GHz via the antenna 85. The system preferably operates in the ultra-wideband range, so that the sensor 70 is configured to transmit and receive signals with a frequency of 3.1 GHz to 10.6 GHz via the antenna 85. The sensor 70 sends and receives measurement signals via the antenna 85, with the aid of which the quality of the oil in the oil expansion tank 20 can be determined.This embodiment allows for advantageous portability, which reduces the time required to check oil quality.

[0042] Computing device 90 is a laptop computer or any other type of computer configured to process and visualize the measured values ​​measured by sensor 70. In particular, computing device 90 is configured to calculate values ​​regarding the color, water content, and / or acidity of the oil based on the measured values ​​measured by sensor 70. For example, a fast Fourier transform can be applied to the measured data.

[0043] The oil transformer further comprises a temperature, gas, and / or vibration sensor 65. The temperature, gas, and / or vibration sensor 65 is arranged in the oil expansion tank 20. The temperature, gas, and / or vibration sensor 65 is configured to send measurement data to the sensor 70 and / or to the computing device 90. For this purpose, the temperature, gas, and / or vibration sensor 65 can comprise a communication interface that enables communication with the sensor 70 and / or the computing device 90. The communication interface can be arranged at the opening 24 and, for example, provide a wired connection to the sensor 70. If the temperature, gas, and / or vibration sensor 65 is designed as a gas sensor, it can be configured to detect abnormalities in the gas generated by the oil transformer.The sensor may also include additional sensor and electronic components that monitor regular operation and condition of the oil transformer.

[0044] In the presented embodiments, various features and functions of the present disclosure have been described separately and in specific combinations. However, it is understood that all or some of these features and functions can be freely combined with one another, unless explicitly excluded.

Claims

CLAIMS 1. An oil transformer comprising a transformer tank (10), an oil conservator (20), a flow channel (30) connecting the transformer tank (10) to a first opening (22) in the oil conservator (20), a cell (55) for receiving oil (40), Means (57, 58) for conveying oil (40) from the oil expansion tank (20) into the cell (55), an antenna (85) for applying a measuring signal to the oil (40) in the cell (55), and a sensor (70) electrically connected to the antenna (85) for measuring an oil quality of the oil transformer.

2. Oil transformer according to claim 1, wherein the sensor (70) is configured to transmit and receive signals having a frequency of 1 Hz to 3000 GHz via the antenna (85).

3. Oil transformer according to one of the preceding claims, wherein the sensor (70) is configured to transmit and receive signals having a frequency of 3.1 GHz to 10.6 GHz via the antenna (85).

4. Oil transformer according to one of the preceding claims, wherein the cell (55) is arranged within the oil conservator (20) above a maximum oil level of the oil conservator (20).

5. Oil transformer according to one of claims 1 to 3, wherein the cell (55) is arranged outside the oil expansion vessel (20) at a second opening (24) of the oil expansion vessel (20).

6. Oil transformer according to claim 5, wherein the second opening (24) is arranged at an upper end of the oil expansion tank (20) and / or the second opening (24) comprises a valve (50).

7. Oil transformer according to one of the preceding claims, wherein the antenna (85) is arranged on or in the cell (55).

8. Oil transformer according to one of the preceding claims, wherein the antenna (85) is designed as a combined transmitting and receiving antenna.

9. Oil transformer according to one of the preceding claims, wherein the sensor (70) comprises: an ultra-wideband baseband transmitter (71), an ultra-wideband baseband receiver (72) and a digital backend (73).

10. Oil transformer according to one of the preceding claims, further comprising a computing device (90) connected to the sensor (70), wherein the computing device (90) is configured to process and visualize the measured values ​​measured by the sensor (70).

11. Oil transformer according to claim 10, wherein the computing device (90) is configured to calculate values ​​relating to color, water content and / or acid content of oil in the oil expansion tank (20) based on the measured values ​​measured by the sensor (70).

12. Oil transformer according to one of the preceding claims, further comprising a temperature, gas and / or vibration sensor (65) arranged on or in the oil expansion tank (20).

13. Oil transformer according to one of the preceding claims, wherein the means (57, 58) for conveying oil from the oil conservator (20) into the cell (55) comprises a hose (57) arranged at least partially in the oil conservator (20) and / or a pipe (57) having a first end extending into the oil (40) in the oil conservator (20) and a second end connected to the cell (55), and a pump (58) for pumping the oil (40) from the oil conservator (20) into the cell (55).

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