Transformer oil dielectric loss factor on-line measurement sensor and measurement method

Abstract

The invention relates to the technical field of transformer oil detection, in particular to a transformer oil dielectric loss factor online measurement sensor and a measurement method. The sensor comprises a measuring electrode, a high-voltage electrode and a PCB (Printed Circuit Board), wherein the measuring electrode and the high-voltage electrode are electrically connected with the PCB; the excitation circuit is used for converting a digital signal generated by the single-chip microcomputer into an excitation signal and outputting the excitation signal to the high-voltage electrode; the excitation feedback circuit is used for transmitting the excitation signal acting on the high-voltage electrode as a negative feedback signal to the single-chip microcomputer; the response circuit is used for sending a current signal collected by the measuring electrode as a response signal to the digital-to-analog converter, and the digital-to-analog converter converts the current signal into a digital signal and sends the digital signal to the single-chip microcomputer; and the single-chip microcomputer calculates the dielectric loss factor of the transformer oil according to the phase difference based on the negative feedback signal and the response signal. On-line measurement of the oil dielectric loss factor of the transformer is realized by utilizing a frequency sweep method by combining a single-chip microcomputer system, a columnar electrode and other hardware systems according to a dielectric loss testing principle.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transformer oil detection, and particularly relates to a transformer oil dielectric loss factor on-line measurement sensor and a measurement method. BACKGROUND

[0002] The power transformer is one of the core node devices with the highest individual value in the power system, and once a serious fault occurs, the power system will be non-forced to shut down, causing serious social and economic losses. Therefore, it has great application value to ensure the safe operation of the power transformer. The transformer oil is the main insulating medium of the power transformer, and the quality thereof is directly related to the operation reliability of the power transformer. Real-time monitoring of the quality of the transformer oil is one of the key means.

[0003] According to the national standards GB / T 7595, IEC 60156 and other standard documents, the transformer oil dielectric loss factor is an important parameter index reflecting the damp and deterioration of the transformer insulation. On-line measurement of the dielectric loss factor has important engineering significance for evaluating the insulation performance. The dielectric loss factor is the ratio of the active power consumed to the reactive power when the test sample is subjected to an applied voltage, that is, the tangent value of the dielectric loss angle , which is mathematically related to the phase difference between the current flowing through the dielectric and the voltage in the electric field as . The dielectric loss factor can be obtained by measuring the phase difference between the current and the voltage.

[0004] At present, the dielectric loss of the transformer oil is measured by using a high-voltage bridge test method. This test method needs to collect the transformer oil sample offline, which consumes labor cost and test time. The high-voltage bridge is too large to be used on-line, and the external construction frequency voltage is easy to be disturbed by the electromagnetic field on site. SUMMARY

[0005] The purpose of the present application is to provide a transformer oil dielectric loss factor on-line measurement sensor and a measurement method. By using the dielectric loss test principle, combining a single-chip microcomputer system and a columnar electrode hardware system, and using the sweep frequency method, the transformer oil dielectric loss factor can be measured on-line.

[0006] To achieve the above purpose, the present application adopts the following technical solutions:

[0007] A transformer oil dielectric loss factor on-line measurement sensor comprises a measurement electrode, a high-voltage electrode and a PCB circuit board, wherein the measurement electrode and the high-voltage electrode are electrically connected to the PCB circuit board.

[0008] The PCB circuit board is provided with a single-chip microcomputer, a digital-to-analog converter, an excitation circuit, a response circuit and an excitation feedback circuit, the excitation circuit is used for converting a digital signal generated by the single-chip microcomputer into an excitation signal and outputting the excitation signal to the high-voltage electrode, and the excitation feedback circuit is used for delivering an excitation signal acting on the high-voltage electrode as a negative feedback signal to the single-chip microcomputer.

[0009] The response circuit is used for sending a current signal collected by the measuring electrode to the digital-to-analog converter as a response signal, and the digital-to-analog converter converts the current signal into a digital signal and sends the digital signal to the single-chip microcomputer.

[0010] The single-chip microcomputer calculates the dielectric loss factor of the transformer oil according to a phase difference based on the negative feedback signal and the response signal.

[0011] Further, the high-voltage electrode is a cylindrical electrode, and the high-voltage electrode is provided with a plurality of micropores through which oil flows, and the diameter of the micropores is 0.5-2mm.

[0012] Further, the measuring electrode is a closed cylinder, and the PCB circuit board is located in the measuring electrode.

[0013] The high-voltage electrode and the measuring electrode are arranged side by side, the PCB circuit board is connected with a communication interface, and the communication interface is located at the top of the measuring electrode.

[0014] Further, the measuring electrode and the high-voltage electrode are connected to a mounting seat, and the communication interface is located in the mounting seat.

[0015] Further, the excitation circuit includes a power amplifier circuit and a function generator, the function generator converts a digital sine signal output by the single-chip microcomputer into an analog sine voltage signal, and then the analog sine voltage signal is applied to the high-voltage electrode after passing through the power amplifier circuit.

[0016] Further, the response circuit and the excitation feedback circuit respectively include a signal amplification circuit, a filter circuit, a comparison circuit and a shaping circuit.

[0017] The response signal and the feedback signal are respectively amplified by the signal amplification circuit, filtered by the filter circuit to remove high-frequency noise, removed by the comparison circuit to remove background noise, and input to the digital-to-analog converter after being shaped by the shaping circuit.

[0018] An online measurement method of a dielectric loss factor of transformer oil, which uses the above-mentioned online measurement sensor of the dielectric loss factor of transformer oil to measure;

[0019] The online measurement method includes the following steps:

[0020] The measuring electrode and the high-voltage electrode are immersed in the transformer oil.

[0021] A continuous excitation signal is applied to the high-voltage electrode, and the excitation signal is used as a negative feedback signal. Real-time data collection;

[0022] Real-time acquisition of current signals from measuring electrodes ;

[0023] Calculate the negative feedback signal and current signal phase difference The medium loss factor of the oil is calculated based on the phase difference. Among them, the dielectric loss factor It is frequency The function.

[0024] The technical solution provided by this invention may include the following beneficial effects:

[0025] This scheme achieves online measurement of transformer oil dielectric loss factor through coordinated circuit control of high-voltage electrode and measuring electrode. The sensor is small in size and can measure the dielectric loss of transformer oil at different frequencies.

[0026] By setting response and excitation signals, dual-circuit feedback for dielectric loss measurement is achieved, reducing interference from external signals in dielectric loss factor measurement and improving the reliability of measurement results. Attached Figure Description

[0027] Fig. 1 This is a schematic diagram of the structure of an online transformer oil dielectric loss factor measurement sensor according to an embodiment of the present invention;

[0028] Fig. 2 This is a diagram of the sensor's signal transmission.

[0029] Fig. 3 This is a flowchart of the online measurement method;

[0030] The components include: measuring electrode 1, high voltage electrode 2, PCB circuit board 3, communication interface 4, and mounting base 5. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0032] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected, it can be mechanical connection, or electrical connection, it can be directly connected, or indirectly connected through intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] The transformer oil dielectric loss factor on-line measurement sensor according to an embodiment of the present application will be described below in combination with Figs. 1-2

[0034] The transformer oil dielectric loss factor on-line measurement sensor according to an embodiment of the present application comprises a measurement electrode 1, a high-voltage electrode and a PCB circuit board 3, the PCB circuit board 3 is provided with a first lead pin and a second lead pin, the measurement electrode 1 is electrically connected with the first lead pin, and the high-voltage electrode is electrically connected with the second lead pin.

[0035] The PCB circuit board 3 is provided with a single-chip microcomputer, a digital-to-analog converter, an excitation circuit, a response circuit and an excitation feedback circuit, the excitation circuit is used for converting the digital signal generated by the single-chip microcomputer into an excitation signal and outputting the excitation signal to the high-voltage electrode, and the excitation feedback circuit is used for delivering the excitation signal acting on the high-voltage electrode as a negative feedback signal to the single-chip microcomputer.

[0036] The response circuit is used for sending the current signal collected by the measurement electrode 1 as a response signal to the digital-to-analog converter, and the digital-to-analog converter converts the current signal into a digital signal and sends the digital signal to the single-chip microcomputer.

[0037] The single-chip microcomputer calculates the dielectric loss factor of the transformer oil according to the phase difference based on the negative feedback signal and the response signal.

[0038] The present scheme realizes the on-line measurement of the dielectric loss factor of the transformer oil through the cooperation of the high-voltage electrode and the measurement electrode 1 and the circuit control, the sensor has a small volume, and the dielectric loss of the transformer oil can be measured at different frequencies. The double-circuit feedback of the dielectric loss measurement is realized through the setting of the response signal and the excitation signal, the interference of external signals in the dielectric loss factor measurement is reduced, and the reliability of the measurement result is improved.

[0039] It should be noted that the measurement electrode 1 and the high-voltage electrode are made of corrosion-resistant metal, for example, aluminum alloy or stainless steel.

[0040] ​Preferably, the high-voltage electrode is a cylindrical electrode, and the high-voltage electrode is provided with a plurality of micropores for the transformer oil to pass through, and the diameter of the micropores is 0.5-2 mm. The micropores are circular micropores arranged on the high-voltage electrode, which is beneficial to the passage of the transformer oil and reduces the interference of the transformer oil tension on the test results.

[0041] In order to further reduce the volume of the sensor, the measuring electrode 1 is a closed cylinder, and the PCB circuit board 3 is located in the measuring electrode 1; the high-voltage electrode and the measuring electrode 1 are arranged side by side, and the PCB circuit board 3 is connected with a communication interface 4, and the communication interface 4 is located at the top of the measuring electrode 1. The communication interface 4 is used for connecting an external signal line, and is preferably an RS-485 interface.

[0042] In order to facilitate the installation of the sensor, the measuring electrode 1 and the high-voltage electrode are connected to a mounting seat 5, and the communication interface 4 is located in the mounting seat 5. The mounting seat 5 is made of plastic and is used for fixing the two motors and the communication interface 4. The measuring electrode 1 and the high-voltage electrode are fixed to the mounting seat 5 in a clamping manner or an embedding manner. It can be understood that the communication interface 4 is exposed at the top of the mounting seat 5, so as to facilitate the insertion of the external data line.

[0043] Further, the excitation circuit comprises a power amplifier circuit and a function generator, the function generator converts the digital sine signal output by the single-chip microcomputer into an analog sine voltage signal, and then the analog sine voltage signal is applied to the high-voltage electrode after passing through the power amplifier circuit. In the scheme, the excitation signal is applied in a sweep frequency mode, the single-chip microcomputer generates a sine signal (digital signal) with continuously changing frequency, the signal generator converts the digital sine signal output by the single-chip microcomputer into an analog sine voltage signal, and the power amplifier circuit amplifies the signal, and the amplified voltage signal is applied to the high-voltage electrode as the excitation signal.

[0044] Further, the response circuit and the excitation feedback circuit respectively comprise a signal amplifier circuit, a filter circuit, a comparison circuit and a shaping circuit; the response signal and the feedback signal are respectively amplified by the signal amplifier circuit, filtered by the filter circuit to remove high-frequency noise, compared by the comparison circuit to remove background noise, and input to the digital-to-analog converter after being shaped by the shaping circuit. Specifically, the measuring electrode 1 collects a weak current signal, which is an nA-level response signal, the signal is amplified by the signal amplifier, the filter circuit filters out high-frequency noise, and the response signal is further compared with the background noise to obtain the response signal after removing the background noise. The shaping circuit removes the signals exceeding the limited amplitude in the response signal, and converts the signals into digital signals through analog-to-digital conversion (ADC).

[0045] Correspondingly, the application also provides a transformer oil dielectric loss factor on-line measurement method, which uses the transformer oil dielectric loss factor on-line measurement sensor.

[0046] The on-line measurement method comprises the following steps:

[0047] The measurement electrode 1 and the high-voltage electrode are immersed in the transformer oil;

[0048] The high-voltage electrode continuously applies an excitation signal, and the excitation signal is taken as a negative feedback signal Real-time acquisition is performed;

[0049] The current signal acquired by the measurement electrode 1 is acquired in real time

[0050] The phase difference between the negative feedback signal and the current signal is calculated , and the dielectric loss factor of the oil is calculated according to the phase difference , wherein the dielectric loss factor is a function of the frequency .

[0051] Other configurations and the like of a transformer oil dielectric loss factor on-line measurement sensor and a measurement method according to an embodiment of the present application and operations are known to those skilled in the art, and will not be described in detail here.

[0052] In the description of the present specification, the description referring to the terms "embodiment", "example", and the like means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. Illustrative expressions of the above terms in the present specification do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0053] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.​

Claims

1. An on-line transformer oil dielectric loss factor sensor, characterized by, The transformer oil dielectric loss factor on-line measuring sensor comprises a measuring electrode, a high-voltage electrode and a PCB circuit board, and the measuring electrode and the high-voltage electrode are electrically connected with the PCB circuit board; The PCB circuit board is provided with a single-chip microcomputer, a digital-to-analog converter, an excitation circuit, a response circuit and an excitation feedback circuit, the excitation circuit is used for converting a digital signal generated by the single-chip microcomputer into an excitation signal and outputting the excitation signal to the high-voltage electrode, and the excitation feedback circuit is used for delivering an excitation signal acting on the high-voltage electrode as a negative feedback signal to the single-chip microcomputer; The response circuit is used for sending a current signal collected by the measuring electrode as a response signal to the digital-to-analog converter, and the digital-to-analog converter converts the current signal into a digital signal and sends the digital signal to the single-chip microcomputer; The single-chip microcomputer calculates the transformer oil dielectric loss factor according to a phase difference based on the negative feedback signal and the response signal.

2. The sensor of claim 1, wherein, The high-voltage electrode is a cylindrical electrode, and the high-voltage electrode is provided with a plurality of micropores through which oil flows, and the diameter of the micropores is 0.5-2 mm.

3. The sensor of claim 1, wherein, The measuring electrode is a closed cylinder, and the PCB circuit board is located in the measuring electrode; The high-voltage electrode and the measuring electrode are arranged side by side, the PCB circuit board is connected with a communication interface, and the communication interface is located at the top of the measuring electrode.

4. The sensor of claim 3, wherein, The measuring electrode and the high-voltage electrode are connected to a mounting seat, and the communication interface is located in the mounting seat.

5. The sensor of claim 1, wherein, The excitation circuit comprises a power amplifier circuit and a function generator, the function generator converts a digital sine signal output by the single-chip microcomputer into an analog sine voltage signal, and then the analog sine voltage signal is applied to the high-voltage electrode after passing through the power amplifier circuit.

6. The sensor of claim 1, wherein, The response circuit and the excitation feedback circuit each comprise a signal amplification circuit, a filter circuit, a comparison circuit and a shaping circuit; The response signal and the feedback signal are respectively amplified by the signal amplification circuit, filtered by the filter circuit to remove high-frequency noise, removed of background noise by the comparison circuit and input to the digital-to-analog converter after being shaped by the shaping circuit.

7. A method for on-line measurement of dielectric loss factor of transformer oil, characterized by The transformer oil dielectric loss factor on-line measuring sensor is used for measurement; The on-line measuring method comprises the following steps: The measuring electrode and the high-voltage electrode are immersed in transformer oil. The high-voltage electrode continuously applies the excitation signal as a negative feedback signal Real-time acquisition is performed; Real-time acquisition of current signals acquired by measurement electrodes ; computing a negative feedback signal and a phase difference of a current signal computing a dielectric loss factor of the oil from the phase difference wherein the dielectric loss factor is a function of the frequency .​

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