Device and method for determining the quality of a fluid, high-voltage equipment comprising the device for determining the quality

Abstract

The invention relates to a device (1) for determining the quality of a fluid, comprising a hollow body (2) made of a piezoelectric material, wherein the hollow body (2) comprises at least one opening (3, 4) for admitting a fluid, wherein at least two electrodes (5, 6) for applying a temporally variable electrical voltage, in particular an alternating voltage, and for exciting a vibration in the piezoelectric material are arranged on the hollow body (2), further comprising at least one transmitter (9) arranged in the interior of the hollow body (2) for emitting directed electromagnetic waves (10), in particular light, and at least one sensor (11) for determining a frequency spectrum of the electromagnetic waves passing through the fluid. The invention further relates to a method for determining the quality of a fluid by: (100) providing a device (1) according to the invention; (200) introducing a fluid through the at least one opening (3, 4); (300) applying a temporally variable electrical voltage to at least two electrodes (5, 6) in order to generate an oscillation for at least one predetermined vibration period; (400) emitting directed electromagnetic waves (10) by means of at least one transmitter (9) and determining at least one frequency spectrum by means of at least one sensor (11); and (500) evaluating the frequency spectrum in order to determine the quality of the fluid.

Description

[0001] 'Device and method for determining the quality of a fluid, device in high-voltage engineering comprising the device for determining the quality'

[0002] The invention relates to a device and a method for determining the quality of a fluid, in particular a transformer oil, and a device in high-voltage engineering comprising the device for determining the quality of a fluid according to the preamble of the independent claims.

[0003] In many industries, the quality of a fluid is essential. For example, in the food industry, fluids can be contaminated by foreign matter and / or unwanted byproducts and / or degradation products. This contamination can lead to a reduction in quality and can also be dangerous for consumers. In the field of mechanical engineering, machine oils in particular can be contaminated by various factors and / or contain foreign matter, rendering them unusable or no longer optimally suited for their intended purpose. Especially in high-voltage engineering, fluids such as certain gases and oils are used to electrically insulate components like transformers, capacitors, Petersen coils, and / or switches from their environment.To ensure the continuous and error-free operation of these systems, and to avoid economic losses, it is crucial to detect any potential malfunctions, particularly a reduction in the quality of the fluid used, at an early stage. A reduction in fluid quality can lead to a breakdown and / or a short circuit, which, in addition to the economic risks of a failure, poses significant dangers to life and limb.

[0004] Typically, transformers use a combination of a liquid and a solid insulating material. The solid insulating material is, for example, but by no means exclusively, cellulose paper and / or particleboard. The liquid insulating material, the transformer oil, is stable even at high temperatures and serves for insulation, spark suppression, lubrication, and / or cooling of the transformer. Defects in the solid and / or liquid insulating material, particularly in such liquid-filled transformers, result almost exclusively from the development of gases dissolved in the transformer oil and the resulting increase in its water content.One reason for the formation of these gases is, for example, the decomposition of solid and / or liquid insulating materials, which can be caused by partial discharges and circulating currents, localized overheating due to short circuits, high contact resistances, strong eddy currents, as well as by arc discharges and / or flashovers. The electrical and / or thermal energy input leads to the destruction of long-chain oil molecules, resulting primarily in the formation of hydrogen and light hydrocarbons. Additionally, the decomposition of cellulose produces carbon monoxide and carbon dioxide, which can occur in dissolved and / or undissolved form depending on the quantity of gases produced. It is also possible for water molecules to form, leading to the undesirable oil condensation.In the case of transformer oils based on ester oils, polyesters can be formed during decomposition, which occurs particularly due to the phenomena mentioned above, and these appear as solid particles in the transformer oil.

[0005] Another problem with the water contained in the transformer oil is that the water penetrates the solid insulating material, such as cellulose paper and / or particleboard, and washes the acids present in it during production into the transformer oil. This places an additional strain on the transformer, the intensity of which varies depending on various factors, such as daily temperature fluctuations (e.g., between day and night).

[0006] Therefore, it is of great importance to reliably and safely determine the quality of a fluid. A variety of different methods and devices for this purpose are known in the prior art. In particular, devices and methods are known that, for example, determine the gases dissolved in transformer oil and / or the water concentration, which have a significant influence on the dielectric strength. Many methods and devices for quality determination involve taking a sample. However, this has the disadvantage that the quality determination is neither continuous nor online, and the sampling carries the risk of further deterioration, but also of improvement, of the fluid due to the ingress or escape of foreign bodies and / or substances. In other words, the sampling can contaminate the sample.

[0007] From WO 2018 / 050500 A1, a method and a device are known which, for monitoring the breakdown voltage of a transformer oil, determine the acoustic impedance with at least one frequency band and derive a resonator quality factor from this. The resonator quality factor is the basis for calculating an acoustic imbalance, from which the breakdown voltage of the transformer oil is determined. A disadvantage of this method and this device is that they are only applicable to a small, specific range of applications.

[0008] There is therefore a great need for a device and a method for determining the quality of a fluid, particularly transformer oils, that ensures a fast, reliable, and sufficiently accurate determination of the quality to guarantee adequate, compliant, and / or optimal quality. Particular attention is paid to ensuring that the determination is as unadulterated as possible. Furthermore, the method and device should be cost-effective, operate reliably, and be suitable for continuous determination and / or use. The invention therefore aims to provide a method and a device for determining the quality of fluids that overcomes the aforementioned difficulties. In particular, at least one alternative, preferably an improvement, to the device or method presented in publication WO 2018 / 050500 Al is to be provided.

[0009] This problem is solved surprisingly simply but effectively by a device for determining the quality of a fluid, in particular a transformer oil, a method for determining the quality of a fluid, in particular a transformer oil, and a transformer comprising the device.

[0010] According to the invention, a device for determining the quality of a fluid, in particular a transformer oil, is proposed, wherein the device comprises at least one hollow body made of a piezoelectric material, wherein the hollow body includes at least one opening for the inlet of a fluid, wherein at least two electrodes for applying a time-varying electrical voltage, in particular an alternating voltage, and for exciting an oscillation in the piezoelectric material are arranged on the hollow body, further comprising at least one transmitter arranged inside the hollow body for emitting directed electromagnetic waves, in particular light, and at least one sensor for determining a frequency spectrum of the electromagnetic waves passing through the fluid.

[0011] The basic idea of ​​the invention is that the frequency spectrum of electromagnetic waves, after they have passed through the fluid, allows conclusions to be drawn about the fluid's composition and thus its quality. It has been shown that these conclusions are improved by at least local and / or at least partial separation of particles and / or components of the fluid within a layer. It should be noted that, for determining the quality, both the fluid itself and the most likely sources of contamination and / or impairments of quality are known, as explained above using the example of transformer oil. Therefore, a precise analysis of the composition is not necessary; rather, the frequency analysis already allows for a sufficiently accurate determination, since the possible constituents are already known and differ, in particular, with regard to their refractive index and / or attenuation of electromagnetic waves.

[0012] In other words, the frequency spectrum that the separated fluid should exhibit for optimal and / or sufficient quality is known. A deviation from this frequency spectrum is, in most cases, a reliable indicator of poor quality or a reduction in quality. Further analysis is therefore unnecessary. However, it is possible to draw conclusions about the fluid's components and their concentrations from the frequency spectrum. This has the advantage that components that do not impair quality but were not originally intended in this form can be disregarded, even if they affect the frequency spectrum of the electromagnetic waves passing through the fluid. Furthermore, the thickness and / or formation time of the layer(s) can provide information about the type and size of the particles and / or components.

[0013] Due to its simple design, the entire device can be placed in the fluid and allowed to flow through it. Taking a sample is unnecessary, and the device can remain permanently in a container where the fluid is stored, produced, and / or used. This prevents sample contamination, and any changes in fluid quality can be detected easily and reliably.

[0014] The device comprises a hollow body made of a piezoelectric material. Piezoelectric material is known to deform when a time-varying electrical voltage is applied. If a fluid is contained within the hollow body made of the piezoelectric material and a time-varying electrical voltage is applied to the piezoelectric material at a suitable point, the fluid inside is set in motion. Deformations and / or vibrations of the hollow body are transmitted to the fluid inside. The hollow body has several resonant frequencies, which are determined by material constants and the geometry of the hollow body. Different resonant frequencies may apply to different vibration modes. Methods for calculating and determining these frequencies, as well as the material constants, for setting desired resonant frequencies for desired vibration modes are known to those skilled in the art.The resonant frequency should also be tuned to the fluid under investigation. In particular, different resonant frequencies, and therefore different materials, geometries, and / or dimensions, are necessary for the investigation of gases. The resonant frequency is preferably in the range of 10 kHz to 10 MHz, more preferably in the range of 100 kHz to 7.5 MHz, and most preferably in the range of 500 kHz to 5 MHz. The most preferred resonant frequency is 370 kHz. A hollow cylinder is particularly preferred. A hollow cylinder is easy to manufacture and is particularly easy for a fluid to penetrate. For the investigation of transformer oil, a hollow body, especially a hollow cylinder, made of PZT ceramic (lead zirconium titanate ceramic) is particularly suitable. The height of the hollow cylinder is preferably between 10 mm and 40 mm, particularly 20 mm.The inner diameter of the hollow cylinder is preferably between 10 mm and 40 mm, particularly 21 mm. The wall thickness of the hollow cylinder is preferably between 1 mm and 15 mm, particularly 2.5 mm. It is also conceivable to line the inside of the hollow body with a piezoelectric film, particularly with PVDF film (polyvinylidene fluoride film). The film can be used to create and / or influence the piezoelectric properties of the hollow body. Alternatively and / or additionally, it is conceivable to coat the inside of the hollow body with polarized PVDF copolymer paint (polyvinylidene fluoride copolymer paint) to create and / or influence the piezoelectric properties of the hollow body.

[0015] The hollow body includes at least one opening for fluid inlet. It is also conceivable that the fluid is released through this opening. Inlet and outlet can occur simultaneously or sequentially, through the same opening or through different openings. In other words, the opening allows the fluid to enter the hollow body for quality determination and, if desired, to exit through the same or a different opening, with the precise sequence of inlet and outlet being arbitrary. Inlet and / or outlet can also be continuous. In other words, the fluid flows through the hollow body.The process steps described elsewhere, in particular the propagation of the vibrations in the fluid, the effect caused by the vibrations, and the propagation of the directed electromagnetic waves in the fluid, require considerably less time than the flow of the fluid through the hollow body. Preferably, the hollow body comprises at least two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen, or twenty openings, which may be identical and / or differently configured. Most preferably, the fluid flows into one opening and out of the other. In this way, the fluid can enter the hollow body to be subsequently examined by the device. Most preferably, at least two openings are arranged opposite each other.With regard to the design of the hollow body as a hollow cylinder, the hollow body preferably comprises two openings arranged on the end faces of the hollow cylinder.

[0016] The hollow body further comprises at least two electrodes. Preferably, the electrodes are arranged on and / or around the openings of the hollow body. A time-varying electrical voltage is applied to the electrodes. This means that a voltage potential difference between the electrodes is generated over time. It is conceivable that one of the electrodes is permanently grounded. The voltage potential difference can temporarily, but not permanently, assume the value 0 V. Particularly preferably, the electrodes are arranged opposite each other on the hollow body. In this way, the entire hollow body can be used to generate vibrations. Even more preferably, the electrodes enclose the opening and, in the case of a round opening, form a ring electrode.It is obvious that the electrode must not cover the opening and therefore must also have an opening and / or a breakthrough, which may be at least partially congruent with the opening of the hollow body, if the electrode surrounds the opening.

[0017] The time-varying electrical voltage induces a deformation of the hollow body, causing movement and / or compression of the fluid inside. This sets the fluid in motion, at least in certain areas, resulting in at least local and / or partial separation of particles as they settle. The particle separation mechanism is caused by particle enlargement. Small particles remain suspended in the fluid, while larger ones sink. Consequently, larger particles separate from the fluid. This particle enlargement is achieved by applying a force of a suitable magnitude to the motion induced in the fluid, setting smaller particles in motion while larger, more inert particles move significantly less.Collisions and adhesion of smaller particles with other smaller particles and / or larger particles are highly likely, resulting in particle enlargement. This effect is particularly pronounced when periodic oscillation is induced in the fluid. The effect described above—that smaller particles move significantly less than larger ones—depends on the relationship between average particle size, oscillation frequency, and fluid type. The same effect can be achieved with droplets of a dispersed phase. Particle separation is particularly efficient when the hollow body oscillates at a frequency between 10 Hz and 2 GHz; even more preferably, the frequency is in the range between 20 kHz and 1.6 GHz. The oscillation frequency of the hollow body can be generated by a suitably selected frequency of a periodically changing electrical voltage.Preferably, the hollow body has at least one natural frequency corresponding to the desired oscillation frequency. This increases the efficiency of the device. Most preferably, the time-varying electrical voltage is an alternating voltage or a square wave voltage with a frequency in the range between 10 Hz and 2 GHz, and even more preferably with a frequency in the range between 20 kHz and 1.6 GHz. A transmitter for emitting directed electromagnetic waves is arranged inside the hollow body. Particularly preferably, the transmitter emits directed electromagnetic waves, wherein the waves are emitted in a wave packet containing directed electromagnetic waves of different frequencies. The composition of the wave packet and / or the frequencies of the electromagnetic waves are at least partially, and preferably completely, known.Preferably, the distance traveled by the directed electromagnetic waves is known. Particularly preferably, the wavelengths of the electromagnetic waves of the wave packet or the electromagnetic wave are selected from a range between 1 nanometer and 1 centimeter, more preferably 10 nanometers to 10 millimeters, and most preferably 100 nanometers to 1 millimeter. Most preferably, the directed electromagnetic wave is a light wave and / or a wave packet comprising at least one light wave.

[0018] Furthermore, a sensor for determining the frequency spectrum of the electromagnetic waves after they have at least partially passed through the fluid, and / or for detecting phenomena caused by the directed electromagnetic waves in the fluid, is arranged in the device. Since the frequencies of the directed electromagnetic waves are at least partially known, the refractive index and / or the attenuation for the individual frequencies, or at least for some of the individual frequencies, or for a single frequency of the electromagnetic waves, can be determined taking into account known material constants. For this purpose, for example, the phase relationship of the individual phases of the individual electromagnetic waves with different frequencies can be considered and / or compared.Furthermore, it is conceivable to consider the time required by the wave packet, the electromagnetic wave, and in particular the individual waves of the wave packet, to travel the known distance between the sensor and the transmitter. During the measurement, it is conceivable that the vibration of the hollow cylinder is maintained. The vibration is particularly preferably in the ultrasonic range. The device acts as an acousto-optical modulator, with the transmitter emitting directed electromagnetic waves, in particular laser radiation, and the sensor being able to detect a frequency shift of the directed electromagnetic waves. Further conclusions about the composition can be drawn from the frequency spectrum, the refractive index, and / or the attenuation without the need for additional components in the device. Determining the refractive index and / or the attenuation is not strictly necessary for determining the quality of the device.As described elsewhere, quality determination can also be performed by comparing the frequency spectrum with a target value and / or a target range, without actually determining the aforementioned values. It is particularly preferred that the target value and / or the target value range be determined and / or defined beforehand in a calibration process.

[0019] The device preferably comprises at least two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen, or twenty identically and / or differently configured transmitters and / or at least two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen, or twenty identically and / or differently configured sensors. Preferably, at least one transmitter and at least one sensor are arranged such that the electromagnetic wave strikes the sensor directly and / or reflected. Even more preferably, at least one (other) sensor is oriented such that the electromagnetic wave does not strike the sensor directly. Raman spectroscopy can be performed using this sensor. Optionally, an optical filter is arranged in front of the sensor.Raman spectroscopy is used to determine the Raman shift, which is characteristic of materials. Furthermore, it is possible to determine other characteristic physical properties, in particular density, color, temperature, water concentration, surface tension, viscosity, relative and / or absolute humidity or saturation, acidity, electrical constant, electrical conductivity, and / or the concentration of at least one component of the fluid, and to consider these properties when determining quality.

[0020] Spectrometry, as well as the other measurement methods described above, allows direct or indirect conclusions to be drawn about the quality of the fluid. As described above, the determined frequency spectrum and / or values ​​derived from it can be compared with a target value, target values, a target range, and / or target ranges. The quality is sufficient or optimal if the frequency spectrum or values ​​derived from it correspond to the target value(s) or fall within the target range(s). In this case, for example, the fluid can continue to be used as intended and / or supplied for its intended use. The quality is therefore optimal, meets requirements, and / or is sufficient. If the frequency spectrum and / or one, several, or all values ​​derived from it lie outside the target range(s) or do not correspond to the target value or ranges, the quality is considered sufficient.If the fluid quality does not meet the target values, it is not optimal, not in accordance with requirements, and / or insufficient. In such cases, it is conceivable to dispose of, replace, clean, and / or process the fluid. Furthermore, it is conceivable to use the frequency spectrum and / or other data, taking into account known sources of contamination and the original composition of the fluid, to partially or completely determine the fluid's composition and to determine its quality based on the level, concentration, and / or presence of certain components. This allows the level, concentration, and / or presence of components that are generally harmless for the intended use of the fluid but have a greater influence on the frequency spectrum to be disregarded. In particular, it is conceivable to also consider previous measurements of the same fluid with the device according to the invention when determining the fluid quality.

[0021] The term "quality determination" refers to a qualitative and / or quantitative statement about a fluid with regard to its intended use. The quality determination can be composed of various factors and take environmental influences into account.

[0022] The term "hollow body" refers to a body that contains a cavity, which the hollow body at least partially encloses. The term "opening" refers to a recess that connects the inner cavity of the hollow body to its surroundings.

[0023] The term "electrode" refers to a structure for applying an electrical voltage. It is conceivable that further electrical components are arranged between the electrodes, forming a resonant circuit at the frequency of the hollow body. This makes the device particularly efficient.

[0024] The term "time-varying electrical voltage" refers to an electrical voltage whose value changes over time. This time-varying electrical voltage can briefly exhibit a constant value, as long as it changes at another time. This is particularly true for a square wave voltage.

[0025] The term "transmitter" refers to a suitable means for emitting directed electromagnetic waves, wherein the frequency of the directed electromagnetic waves is known, predetermined, and / or adjustable. Suitable sensors are known to those skilled in the art. Examples of suitable sensors are given elsewhere. The term "sensor" refers to a means for the qualitative and / or quantitative detection of the frequencies of the electromagnetic waves and / or of phenomena triggered by the electromagnetic waves. In particular, the sensor refers to a means for determining the complex-valued function of the frequency spectrum, the amplitude spectrum, and / or the phase spectrum.

[0026] The term "fluid" refers to a substance that continuously deforms under the influence of shear forces, in particular liquids such as water, especially distilled water, mineral water, drinking water, brewing water and / or cooling water; oil, especially edible oil, such as cold-pressed or non-cold-pressed olive oil; lubricating oil, grease, heating oil, machine oil, hydraulic oil, cleaning oil, maintenance oil and / or transformer oil; beverages, especially wine, beer, juice, lemonade, soda, spirits, rum, whiskey, liqueur, mixed drink, syrup, milk, tea and / or coffee; alcohols and / or fuels, such as gasoline, kerosene and / or diesel, especially production residues; and gases, such as toxic and / or non-toxic exhaust gas, natural gas, methane, oxygen, nitrogen, carbon dioxide, sulfur hexafluoride and / or fluoroketone.

[0027] In particular, the device can be used for determining the purity of hexane in butyl rubber production.

[0028] The invention provides a compact, cost-effective, and reliable immersion device for fluids, enabling reliable qualitative and / or quantitative determination of sample quality. This prevents sample contamination. Furthermore, the previously and elsewhere described methods for determining sample quality can be performed quickly and therefore promptly, particularly in real time. Moreover, the fluid and / or the device encompassing the fluid are not affected, and in particular not destroyed, by the previously and elsewhere described methods for determining sample quality. The sample quality determination is therefore non-destructive. Advantageous embodiments of the invention, which can be implemented individually or in combination, are described in the dependent claims.

[0029] It is conceivable that the transmitter is a light-emitting diode (LED) and / or a laser. In particular, it is conceivable that the transmitter is an LED laser. LEDs and lasers emit directed electromagnetic waves whose frequency spectrum is stable, known, adjustable, and / or determinable. An aperture diaphragm is particularly preferably arranged in front of the LED and / or the laser, and / or the aperture of the LED and / or the laser is known. Lasers are particularly suitable for emitting an electromagnetic wave that raises an irradiated molecule to a higher energy level. Occasionally, inelastic scattering occurs, resulting in a frequency shift relative to the frequency of the electromagnetic wave emitted by the laser. This frequency shift is called the Raman shift and, as described above, is a material-specific value.Therefore, Raman spectrography can be used to draw conclusions about the material of particles in the fluid and / or the fluid itself. Preferably, at least one transmitter is a laser diode and at least one other transmitter is a light-emitting diode.

[0030] The term "laser" refers to a device that emits coherent, quasi-monochromatic and sharply focused electromagnetic radiation with a wavelength between 1 nm and 1 mm.

[0031] The term "light-emitting diode" refers to a semiconductor component that emits electromagnetic waves with wavelengths between 1 nm and 1 mm. These electromagnetic waves are emitted in a non-coherent and non-monochromatic wave packet.

[0032] In a further development of the invention, it is conceivable that the sensor is a digital spectrometer. A digital spectrometer is capable of analyzing incoming electromagnetic wave packets with regard to their frequency components, in particular their complex function, their amplitudes, and / or their phase positions, and / or of determining the frequency and / or amplitude of a monofrequency electromagnetic wave. The analysis is particularly preferably performed taking elapsed time into account, so that a relationship between the individual phases of the components of the electromagnetic waves is possible. From this, conclusions can be drawn about the transit time between the transmitter and the sensor, from which the frequency-dependent refractive index can be calculated. Spectrometers are already available on very small scales; these are called spectral sensors.Their dimensions are less than 3 mm in any spatial direction, so that they can easily be incorporated into the device according to the invention.

[0033] The term "digital spectrometer" refers to a device for analyzing and displaying a spectrum. The display is in the form of digital data, which is preferably evaluated by a processor.

[0034] A further sensor, preferably an ultrasonic receiver, is preferred. This receiver can detect the influence of the fluid on ultrasonic waves, which are preferably transmitted to the fluid by the vibration of the hollow body, and thereby improve conclusions about the fluid's quality. For example, the acoustic impedance can be determined. It is preferred that the further sensor is arranged on a piezoelectric unbalanced body, in particular a plate designed as a bending resonator. The piezoelectric unbalanced body is excited to vibrate by applying a time-varying electrical voltage, while the hollow body remains unexcited. The piezoelectric unbalanced body particularly preferably generates sound waves in the range of 0.1 nm to 1000 nm. This allows for a more comprehensive evaluation of the device's quality, requiring only a few additional components.It is also conceivable that the device has at least two identical transmitters and two identical sensors, arranged at different locations within the device. This redundancy allows the device to continue operating even if one of the sensors or transmitters fails.

[0035] Furthermore, it is conceivable that the transmitter is oriented in such a way that the directed electromagnetic waves are reflected by an internal surface of the hollow body and / or by a reflector. This reflection can lengthen the path of the directed electromagnetic waves. As a result, the directed electromagnetic waves undergo greater modulation, thereby improving the accuracy of the quality factor determination.

[0036] The term "reflector" refers to a component and / or a coating that is suitable to reflect directed electromagnetic waves at least partially, preferably completely.

[0037] Preferably, the reflector is arranged in the device such that the vibrations of the hollow body are not transmitted to it. One way to achieve this is by incorporating at least one damping element. Furthermore, it is conceivable to dimension the hollow body, made of piezoelectric material, such that when vibrations occur under the influence of the time-varying electrical voltage, at least one node is formed at which the reflector is located. Suitable methods for determining and / or calculating the dimensions and design of the hollow body are known to those skilled in the art. This ensures that the measurement is not distorted by the vibration of the reflector.

[0038] Furthermore, it is conceivable that the device comprises a circuit board, the circuit board being at least partially contained within the cavity of the hollow body, and the sensor and transmitter being arranged on the circuit board. The circuit board preferably divides the cavity into sub-cavities. It is conceivable that the vibrations from the piezoelectric cylinder are transmitted to the circuit board, and that the circuit board thus contributes to the transmission of vibrations to the fluid in the hollow body. Circuit boards are particularly well suited for connecting the components placed on them, especially the sensor and the transmitter, to form at least one circuit. Other conceivable components include at least one processor, at least one controller, at least one clock generator, at least one power source, at least one means of data transmission, at least one energy storage device, and / or at least one data storage device.

[0039] More preferably, the device comprises an ultrasonic receiver rigidly connected to it in a manner described elsewhere. The ultrasonic transmitter receives the ultrasonic wave transmitted to the fluid via the circuit board after it has passed through the fluid. It is also conceivable to arrange a rigid ultrasonic reflector opposite the circuit board, with the circuit board acting as an ultrasonic sensor. Similarly, it is conceivable to arrange an ultrasonic sensor on the circuit board.

[0040] In one embodiment, it is conceivable that the sensor and transmitter are arranged such that the directed electromagnetic waves strike the sensor. That is, the sensor detects the directed electromagnetic wave directly or after at least one reflection. From this, conclusions about the material can be drawn in a suitable manner, as described elsewhere. For example, the spectral analysis of the electromagnetic wave, the determination of the refractive index (indirectly or directly), or an acousto-optical examination can be performed.

[0041] Additionally or alternatively, it is conceivable that the sensor and the transmitter are arranged such that the directed electromagnetic wave propagates past the sensor. In other words, the electromagnetic wave does not reach the sensor. With this arrangement, other investigations, such as Raman spectrography, as described elsewhere, can be carried out. In particular, it is conceivable that at least two sensors are arranged in the device, wherein at least one first sensor is arranged such that the directed electromagnetic wave reaches the sensor, and at least one second sensor is arranged such that the directed electromagnetic wave does not reach the sensor.It is also conceivable that the device comprises at least two transmitters, wherein at least one first transmitter is arranged such that the directed electromagnetic waves it emits strike at least one sensor, and at least one second transmitter is arranged such that the directed electromagnetic waves it emits do not directly strike any sensor. The first transmitter is particularly preferably a light-emitting diode (LED) and the second sensor is a laser, in particular a laser diode.

[0042] In a further development, it is also conceivable that the device includes at least one energy harvesting means and / or a data transmission means. The energy harvesting means enables a long-term energy supply for the device without it being connected to an external energy source or a depletable local energy source. Particularly with regard to transformers, this allows for the continued use of a closed insulation design for the transformer. A piezoelectric element, which is set into vibration by the transformer's vibration, and / or an induction coil, which extracts a very small portion of the electrical energy via the transformer's electromagnetic field, are particularly suitable for this purpose. The data transmission means enables the transmission of the data collected by the device to a receiver.The measurement results, intermediate values, and / or the determined quality as a final value can be transmitted directly. Data transmission is preferably wireless. Furthermore, it is conceivable that the device includes a processor for the direct evaluation of the measured values ​​acquired by the sensors and / or a data storage device for storing the measured values ​​or the results of the evaluation performed by the processor. It is also conceivable that the device includes a controller, in particular a microcontroller, for controlling the device. The controller can be identical in component type to the aforementioned processor.

[0043] It is assumed that the definitions and / or explanations of the terms mentioned above apply to all aspects described below, unless otherwise stated. Furthermore, process steps and / or features of process steps described above in connection with the device are also conceivable embodiments of the process described below, and features of a device described below in connection with the process are conceivable embodiment features of the device described above.

[0044] Furthermore, according to the invention, a method for determining the quality of a fluid is proposed, comprising the following steps: a. Providing a device described elsewhere; b. Introducing a fluid, in particular a transformer oil, through at least one of the openings; c. Applying a time-varying electrical voltage to at least one of the electrodes to generate a vibration for at least a predetermined vibration period; d. Emitting directed electromagnetic waves by means of at least one transmitter and determining at least one frequency spectrum by means of at least one sensor; and e. Evaluating the frequency spectrum to determine the quality of the fluid.As described elsewhere, the frequency spectrum of an electromagnetic wave or wave packet after passing through a fluid is particularly suitable for inferring the fluid's composition, provided the type of fluid and any potential undesirable foreign substances and / or components present are already known. Therefore, this method offers a simple, cost-effective, and reliable way to determine the quality of a fluid. The vibration serves, in particular, to bring about at least a local and / or partial separation of particles and / or components of the fluid.

[0045] It is conceivable that the emission of directed electromagnetic waves by means of at least one transmitter and / or the determination of at least one frequency spectrum by means of at least one sensor, in addition to step d, takes place at least for a period of time before and / or after step d, in particular during step b, step c, and / or step e. Particularly preferably, the emission of directed electromagnetic waves by means of at least one transmitter and / or the determination of at least one frequency spectrum by means of at least one sensor takes place continuously, in particular during the process. It is further preferably conceivable that steps b to e.The process is repeated continuously and / or after a predetermined period, wherein the emission of directed electromagnetic waves by means of at least one transmitter and / or the determination of at least one frequency spectrum by means of at least one sensor is carried out continuously during the repetitions and / or during the predetermined period. Furthermore, it is conceivable that the evaluation of the frequency spectrum to determine the quality of the fluid is also carried out continuously, in particular throughout the entire process, during the repetitions and / or during the predetermined period. In a further development, it is conceivable that in step d. the time-varying electrical voltage is applied at least for an initial measurement period.In particular, the hollow body is made of piezoelectric material, and the time-varying electrical voltage is designed such that mechanical vibrations, especially in the ultrasonic range, are transmitted to the fluid. This creates compressions in the fluid, whereby the refractive index in the fluid changes in a manner characteristic of the fluid in connection with the compression. In other words, a Bragg grating is present in the fluid. A laser beam directed at a suitable angle onto this moving Bragg grating experiences both a spatial rotation, known as the Bragg angle, and a Doppler frequency shift, which manifests as a frequency change in the directed electromagnetic wave. Multiple beam paths, each rotated by the Bragg angle relative to its neighboring beam path, can occur.Both the Bragg angle and the frequency modulation are material-specific, as they depend on the grating constant of the Bragg grating and / or the refractive index. In other words, the device operates like an acousto-optic modulator. A deviation from the values ​​specified for the fluid can therefore indicate a reduction in the fluid's quality factor. In particular, the refractive index of water differs significantly from that of oil, resulting in different angles and frequency modulations. Therefore, the water content in transformer oil, which, as described above, is a factor reducing the quality factor, can be determined and / or taken into account. Furthermore, the speed of sound waves in the material can be determined, allowing conclusions to be drawn about the fluid's quality factor. For example, the acoustic impedance of the fluid can be determined, which may deviate if the quality factor is reduced.Furthermore, it is conceivable that in step d. the time-varying electrical voltage is essentially constant, at least for a second measurement period. In other words, the time-varying electrical voltage is not applied and therefore has a value of 0 V and / or undergoes no or only a slight change during the second measurement period. In other words, no vibration is transmitted from the hollow body and / or the circuit board to the fluid during the second measurement period. For example, it is conceivable to perform Raman spectrography and / or spectrography of the medium at rest in this state. The spectrography of the medium at rest should be carried out, in particular, taking into account the phase relationship of individual electromagnetic directed waves that are part of a wave packet. It is known that the refractive index is material-specific and frequency-dependent.Raman spectrography can be used to analyze the composition of particles present in fluids.

[0046] The term "essentially" means that there is only a minor, and in particular non-significant, change, alteration, and / or deviation from the relevant conditions. Specifically, a change of no more than 1 mV per second is covered by the term "essentially".

[0047] Furthermore, it is conceivable that the evaluation in step e. includes at least one comparison with empirically, theoretically, computationally, simulation-based, and / or historically determined values ​​stored in a database. This allows for a quick and easy assessment of the fluid's quality without the need for complex calculations or determinations. The empirical data for the database can be generated through targeted evaluations by identifying fluids with optimal composition and fluids at various quality levels, where a reduction in quality can be deliberately induced. Additionally, the corresponding measured values ​​for different fluid qualities can be determined using theoretical, computational, and / or simulation-based methods. It is also conceivable to utilize historical values ​​from previous fluid tests.In particular, it is conceivable to build the database using empirical and historical data and then supplement it with theoretical, computational, and simulation methods. The data can include, in particular, previous measurements of the same fluid to account for gradual changes in quality. This gradual change in quality can then be used to identify potential sources of defects. For example, a malfunction in the manufacturing process and / or a malfunction of the device in which the fluid is introduced and / or used can be detected.

[0048] In further training, it is conceivable that the determination of the fluid quality in step e. includes the determination of the water content, acid content, ester content, particle density, particle size, dielectric strength, surface tension, density, viscosity, dielectric material value, and / or loss factor. The specific determination of one, several, or all of the aforementioned values ​​allows for a more comprehensive picture of the fluid quality, particularly of a transformer oil. The quality can thus be determined in a more differentiated manner. Water, acid, and esters, in particular, have a specific refractive index; therefore, frequency spectral analysis and / or the acousto-optical analysis method are especially suitable for determining these. The particle density and / or particle size can be determined, in particular, by a separation rate in step c. and / or by a Raman frequency analysis described elsewhere.The dielectric strength and / or surface tension can be determined, in particular, from the other specified values. Furthermore, the dielectric strength and / or surface tension can be derived from the acoustic impedance. All values ​​can also be determined with sufficient accuracy by comparison with empirically, theoretically, computationally, simulation-based, and / or historically determined values, as described elsewhere.

[0049] According to the invention, a device for high-voltage applications comprising transformer oil and at least one other device described elsewhere is proposed. In general, the device and the method are suitable for determining the quality of any fluid. However, the device according to the invention for determining the quality is particularly well suited for use in devices for high-voltage applications comprising transformer oil. This is due to the potential sources of damage that contribute to a reduction in the quality of transformer oil. These can be determined particularly well and reliably by the device described elsewhere. The quality of transformer oil is particularly affected by the formation of water and / or acid in the transformer oil. Water and / or acid have a refractive index that differs significantly from that of oil.Furthermore, polyester particles can form during the decomposition of transformer oil, particularly if it is an ester-based transformer oil. The polyester particles settle significantly faster than esters when the fluid is set into vibration, thereby altering the oil's refractive index. In high-voltage applications, a capacitor, a Petersen coil, and / or a switch is particularly preferred. A transformer is the most preferred device.

[0050] Further details, features, and advantages of the invention will become apparent from the following description of the preferred embodiments in conjunction with the dependent claims. The features shown in the embodiment can be implemented individually or in combination with one another. The invention is not limited to the exemplary embodiments. The exemplary embodiments are shown schematically in the figures.

[0051] Specifically, we show:

[0052] Fig. 1 shows a device according to the invention in perspective view;

[0053] Fig. 2 shows the device according to the invention without the hollow body in a perspective view;

[0054] Fig. 3 shows the circuit board of the device according to the invention together with the components arranged on it in a perspective view;

[0055] Fig. 4 shows an enlarged section of the circuit board shown in Fig. 3 in a perspective view;

[0056] Fig. 5 shows a flowchart of the individual steps of a method according to the invention;

[0057] Fig. 6 shows a device according to the invention in high-voltage technology with a device according to the invention in perspective view; and

[0058] Fig. 7 shows an enlarged section of the device according to the invention shown in Fig. 6 in high voltage technology with the device according to the invention in perspective view.

[0059] Fig. 1 shows a perspective view of an embodiment of a device 1 according to the invention. The device 1 according to the invention comprises a hollow body 2 made of a piezoelectric material. The hollow body 2 is designed as a hollow cylinder without any end surfaces. Therefore, the hollow cylinder 2 has a first opening 3 at one end face and a second opening 4 at the opposite end face. Fluid can flow into and / or out of the interior of the hollow body 2 through the first opening 3 and / or the second opening 4. A first electrode 5 and a second electrode 6 are arranged around the openings 3 and 4. A protective sleeve is arranged on the second electrode 6, extending from the outer surface. If a time-varying electrical voltage is applied to the electrodes 5 and 6, the hollow body 2 is set into vibration due to the piezoelectric material.Particularly preferred is a periodic, time-varying electrical voltage, the frequency of which corresponds to a natural frequency of the hollow body 2. This causes the hollow body 2 to vibrate, and this vibration is transmitted to the fluid contained within the hollow body 2. In other words, the hollow body 2 vibrates and transmits the vibrations to the fluid. Heavier components of the fluid sink to the bottom of the hollow body 2. The time-varying electrical voltage is transmitted to the first electrode 5 via a first terminal 7, which is connected to the first electrode 5, and to the second electrode 6 via a second terminal 8, which is connected to the second electrode 6. The device 1 further comprises a circuit board 12, which is arranged at least partially inside the hollow body 2 and which is explained in detail in Figures 2 to 4.The circuit board 12 is arranged centrally within the hollow body 2, such that the circuit board 12 encloses an interior space with part of the outer surface of the hollow body 2. The device further comprises a data transmission means 14, which in this embodiment is a connector. In another preferred embodiment, not shown, the data transmission means 14 is a transmitter that can transmit the data wirelessly.

[0060] Fig. 2 shows the device 1 according to the invention in a perspective view without the hollow body 3 (see Fig. 1). In addition to the components described in Fig. 1, a transmitter 9 is visible. The transmitter 9 is an LED with a known emission spectrum. The transmitter 9 emits electromagnetic waves bundled together in a wave packet, the frequency, amplitude, and phase relative to each other of the individual waves being known. A sensor 11 is arranged next to the transmitter 9. The sensor 11 is a spectral sensor. That is, the sensor 11 is capable of detecting the individual spectra of the incident electromagnetic waves, in particular the amplitude and phase. A reflector 13 is arranged on the hollow body opposite the transmitter 9.The electromagnetic waves emitted by transmitter 9 pass through the fluid in cavity 3 and strike the reflector 13, which reflects the electromagnetic waves so that, after passing through the fluid again, they reach sensor 11. The amplitude allows conclusions to be drawn about the attenuation of the individual waves of the electromagnetic wave packet. The phase relationship provides information about the refractive index. Attenuation and refractive index allow conclusions to be drawn about the components of the fluid. From this, a quantitative and / or qualitative statement can be made about the quality of the fluid. In the device 1 shown in Fig. 2, the total refractive index of the fluid is determined. It is also conceivable that transmitter 9 is capable of emitting laser light.If the hollow body 3 vibrates during the emission of the laser light, these vibrations, when transmitted to the fluid, also cause vibrations in the fluid, resulting in local compressions. These vibrations are particularly prevalent in the ultrasonic range. The fluid thus forms a Bragg grating across the denser and less dense areas, which propagates in one direction. The laser light striking this Bragg grating is deflected at an angle, the Bragg angle, and undergoes a frequency shift. The magnitude of the Bragg angle and the frequency shift can provide information about the composition of the fluid, as these are material-specific.If transmitter 9 is able to emit both wave packets with different electromagnetic waves of different frequencies and laser light, both investigation methods can be carried out, and a particularly comprehensive picture of the quality of the fluid can be given.

[0061] Fig. 3 shows the circuit board 12 with the components arranged on the circuit board 12.

[0062] Components include the connections 7, 8, the transmitter 9, the sensor 1 1 and the means for data transmission 14. Furthermore, a processor 15 is arranged on the circuit board 12, which evaluates the data received from the sensor 1 1 and controls the device.

[0063] Fig. 4 shows an enlarged view of a section of the circuit board 12. An electromagnetic wave 10 emitted by the transmitter 9 is shown schematically. Another electromagnetic wave 10, shown schematically, which has been attenuated as it passes through the fluid, is received by the sensor 11.

[0064] Fig. 5 shows a flowchart for a method according to the invention. In step a.100, the device 1 (see Figs. 1 to 4) is provided. It is provided in such a way that the fluid to be examined can flow into the device 1. This can be done, for example, by temporarily or permanently connecting it to appropriate ports on a vessel containing the fluid. Alternatively, the device 1 can be placed directly into the fluid to be examined. It is also conceivable that the device is part of a piping system through which the fluid is conveyed.

[0065] In the subsequent step b.200, fluid is introduced through the at least one opening 3, 4 into the hollow body 2 of the device 1. This can be done actively by setting the fluid in motion. It is also conceivable that the introduction occurs under the influence of gravity, either by placing the fluid into a container in which the device is located, or by placing the device into a container with fluid. Step a.100 and step b.200 can have at least a partial temporal overlap.

[0066] In the next step, c. 300, a time-varying electrical voltage is applied to at least one electrode 5, 6 to generate a vibration in the hollow body 2 for at least a predetermined vibration period. During this vibration period, the vibrations transmitted from the hollow body 2 to the fluid cause a separation of individual components of the fluid inside the hollow body 2. The length of the vibration period is determined in particular by the size of the hollow body 2 and the type of fluid. It is evident that complete separation of the individual components is not required.

[0067] Subsequently, in step d. 400, directed electromagnetic waves 10 are emitted by means of the transmitter 9 and received by means of the sensor 1, whereby a frequency spectrum is determined. Step d. 400 can be divided into two steps, wherein in a first sub-step 410 an electromagnetic voltage is still applied to the electrodes 5, 6 of the device 1 and the hollow body 2 thus vibrates. In the subsequent second sub-step 420, no time-varying electrical voltage is applied. As described elsewhere, different measurements can be taken here, which are influenced by different material- and / or composition-specific values.

[0068] In the next step, e.g., 500, the values ​​recorded by sensor 1 1 are evaluated to determine the quality of the fluid. This can be done, in particular, by comparing the values ​​with previously determined values.

[0069] Fig. 6 shows a device according to the invention in high-voltage technology 20 with a device 1 according to the invention in a perspective view. The device in high-voltage technology 20 is designed as a transformer. The transformer contains transformer oil, the quality of which is determined by the device 1.

[0070] Fig. 7 shows an enlarged section of the device 20 according to the invention shown in Fig. 6 in high-voltage technology, with the device 1 according to the invention in a perspective view. The device 1 comprises a housing 16 in which the components of the device 1 shown in Figs. 1 to 4 are accommodated. The device 1 is connected to the transformer via a connection flange 17, through which the transformer oil flows from the transformer into the housing 16 or vice versa. Opposite the connection flange 17, an interface 18 is arranged, by means of which electrical energy is supplied to the device 1 for generating the time-varying electrical voltage and / or for supplying the components and / or via which data transmission is enabled.

[0071] Reference numeral list Device Hollow body First opening Second opening First electrode Second electrode Connection first electrode Connection second electrode Transmitter Electromagnetic wave Sensor Circuit board Reflector Means of data transmission Processor Housing Connection flange Interface Device in high-voltage technology Step a. Step b. Step c. Step d. First sub-step Second sub-step Step e.

Claims

Patent claims 1. Device ( 1 ) for determining the quality of a fluid, in particular a transformer oil, comprising a hollow body (2) made of a piezoelectric material, wherein the hollow body (2) comprises at least one opening (3 , 4) for the inlet of a fluid, wherein at least two electrodes (5 , 6) for applying a time-varying electrical voltage, in particular an alternating voltage, and for exciting an oscillation in the piezoelectric material are arranged on the hollow body (2), further comprising at least one transmitter (9) arranged inside the hollow body (2) for emitting directed electromagnetic waves (10), in particular light, and at least one sensor (1 1 ) for determining a frequency spectrum of the electromagnetic waves passing through the fluid.

2. Device ( 1 ) according to claim 1 , characterized in that the transmitter (9) is a light-emitting diode and / or a laser.

3. Device ( 1 ) according to claim 1 or 2, characterized in that the sensor ( 1 1 ) is a digital spectrometer i st.

4. Device ( 1 ) according to one of claims 1 to 3 , characterized in that the transmitter (9) is oriented such that the directed electromagnetic waves ( 10) are reflected by an inner surface of the hollow body and / or by a reflector ( 13 ).

5. Device (1) according to one of claims 1 to 4, characterized in that the device (1) comprises a circuit board (12), wherein at least a part of the cavity of the hollow body (3) is bounded by the circuit board (12) and at least one side wall of the hollow body (3), wherein the sensor (11) and the transmitter (9) are arranged on the circuit board (12).

6. Device (1) according to one of claims 1 to 5, characterized in that the sensor (11) and the transmitter (9) are arranged such that the directed electromagnetic waves (10) hit the sensor (11).

7. Device (1) according to one of claims 1 to 6, characterized in that the sensor (11) and the transmitter (9) are arranged such that the directed electromagnetic waves (10) propagate past the sensor (11).

8. Device (1) according to one of claims 1 to 7, characterized in that the device (1) comprises at least one means for energy harvesting and / or a means for data transmission (14).

9. Method for determining the quality of a fluid comprising the following steps: a. (100) providing a device (1) according to any one of claims 1 to 8; b. (200) introducing a fluid, in particular a transformer oil, through the at least one opening (3, 4); c. (300) Applying a time-varying electrical voltage to at least two electrodes (5, 6) to generate an oscillation for at least one predetermined vibration period; d. (400) Emitting directed electromagnetic waves ( 10) by means of at least one transmitter (9) and determining at least one frequency spectrum by means of at least one sensor ( 1 1 ); and e. (500) Evaluating the frequency spectrum to determine the quality of the fluid.

10. Method according to claim 9, wherein in step d. (400) the time-varying electrical voltage is applied at least for a first measurement period. 1 1. Method according to claim 9 or 10, wherein in step d. (400) the time-varying electrical voltage is substantially constant at least for a second measurement period.

12. Method according to one of claims 9 to 1 1 , wherein in step e. (500) the evaluation comprises a comparison with empirically, theoretically, computationally, simulation-based and / or historically determined values ​​stored in a database.

13. Method according to any one of claims 9 to 12, wherein the determination of the quality in step e. (500) comprises the determination of a water content, an acid content, an ester content, a particle density, a particle size, a dielectric strength, a surface tension, a density, a viscosity, a dielectric material value and / or a loss factor.

14. Device in high-voltage technology (20) comprising transformer oil and comprising at least one device ( 1 ) according to any one of claims 1 to 8.

15. Device in high-voltage technology (20) according to claim 14, characterized in that the device in high-voltage technology (20) is a transformer.

Images