Transformer volume resistivity sensor, measurement method and calibration method
By designing a transformer volume resistivity sensor based on the principle of parallel shunt, the problem that the prior art cannot accurately measure the volume resistivity of transformer insulating oil in high temperature environments is solved, and online high-precision monitoring of transformer oil is achieved.
Patent Information
- Application Number
- CN202510105746.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-23
- Publication Date
- 2025-05-06
AI Technical Summary
Existing resistivity sensors cannot be used for accurate measurement of transformer insulation oil in high temperature environments, especially the volume resistivity of transformer insulation oil with high resistance.
A transformer volume resistivity sensor is designed, using the principle of shunt in parallel between the inner electrode and the outer electrode. Based on the preset voltage, the current between the inner electrode and the outer electrode is measured, the volume resistivity of the transformer insulating oil is calculated, and a calibration method is provided to improve measurement accuracy.
It realizes online monitoring of transformer insulation oil in high temperature environments, can accurately measure the volume resistivity of high resistance value, and meets the safe operation and maintenance needs of transformer oil.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of transformer measurement, and in particular to a transformer volume resistivity sensor, a measurement method and a calibration method. Background Art
[0002] Transformer insulating oil plays a major role in insulation and heat dissipation in transformers, reactors, and mutual inductors. At the same time, filling it in the gaps of insulating materials can protect components such as the core and windings, and can reduce the oxygen content absorbed by cellulose and other materials to a minimum to delay oxygen corrosion of components. With the development of high-voltage transmission and transformation technology in the power industry, there are more and more large-capacity, high-parameter steam turbine units, which puts forward higher requirements for the safe operation and maintenance of various indicators of transformers.
[0003] Up to now, the only means of measuring the volume resistivity of insulating oil (transformer insulating oil) on the market is desktop measuring instruments, and there is no volume resistivity sensor for transformer insulating oil. However, desktop measuring instruments cannot monitor in real time.
[0004] Existing resistivity sensors cannot be applied to the measurement of transformer insulating oil. For example, the fire-resistant oil volume resistivity sensor has a narrow application range and operating temperature (20°C), while the normal operating temperature of transformer insulating oil is 90°C and the resistance value is very large. It can be seen that the fire-resistant oil volume resistivity sensor cannot be applied to the measurement of transformer insulating oil. For another example, the conductivity sensor has a large test range, but a large measurement lower limit value, and cannot accurately measure the volume resistivity of high-resistance transformer insulating oil.
[0005] Therefore, it is particularly important to develop a volume resistivity sensor suitable for transformer insulating oil, with a wide insulation detection range and high temperature detection, and its measurement and calibration method to meet the needs of online monitoring of transformer insulating oil. Summary of the invention
[0006] The purpose of this application is to provide a transformer volume resistivity sensor, a measurement method and a calibration method to achieve high-temperature online monitoring of transformer insulating oil.
[0007] To achieve the above objectives, this application provides the following solutions.
[0008] In a first aspect, the present application provides a transformer volume resistivity sensor, the transformer volume resistivity sensor comprising: an inner electrode, an outer electrode and a measurement circuit;
[0009] The inner electrode and the outer electrode are both connected to the measuring circuit;
[0010] The inner electrode is arranged inside the outer electrode, a cavity is formed between the inner electrode and the outer electrode, and an oil inlet and an oil outlet are arranged on the outer electrode;
[0011] The measuring circuit is used to measure the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage based on the parallel shunt principle; the current of the transformer insulating oil between the inner electrode and the outer electrode at the preset voltage is used to calculate the volume resistivity of the transformer insulating oil.
[0012] In a second aspect, the present application provides a transformer volume resistivity measurement method, the transformer volume resistivity measurement method using the above-mentioned transformer volume resistivity sensor, the transformer volume resistivity measurement method comprising the following steps:
[0013] obtaining the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage;
[0014] Calculating the current density of the transformer insulating oil between the inner electrode and the outer electrode according to the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage;
[0015] The volume resistivity of the transformer insulating oil is calculated according to the current density of the transformer insulating oil between the inner electrode and the outer electrode.
[0016] In a third aspect, the present application provides a calibration method for the transformer volume resistivity sensor described above, the calibration method comprising the following steps:
[0017] Prepare a plurality of different standard transformer insulating oils and determine the true value of the volume resistivity of each standard transformer insulating oil;
[0018] Using a transformer volume resistivity sensor to measure and obtain the current of each calibrated transformer insulating oil between the inner electrode and the outer electrode at a preset voltage;
[0019] The preset voltage and the current of the calibrated transformer insulating oil between the inner electrode and the outer electrode at the preset voltage are used as input, and the true value of the volume resistivity of the calibrated transformer insulating oil is used as a label to construct sample data;
[0020] The sample data is used to calibrate a volume resistivity calculation model so that a deviation between a calibration value of the volume resistivity of the calibrated transformer insulating oil output by the volume resistivity calculation model and a true value of the volume resistivity of the calibrated transformer insulating oil is less than a deviation threshold, thereby obtaining a calibrated volume resistivity calculation model.
[0021] In a fourth aspect, the present application provides another transformer volume resistivity measurement method, the transformer volume resistivity measurement method comprising the following steps:
[0022] obtaining the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage;
[0023] According to the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage, the volume resistivity of the transformer insulating oil is obtained using a calibrated volume resistivity calculation model; the calibrated volume resistivity calculation model is obtained using the above calibration method.
[0024] According to the specific embodiments provided in this application, this application has the following technical effects.
[0025] The present application provides a transformer volume resistivity sensor, a measurement method and a calibration method. The transformer volume resistivity sensor of the present application includes an inner electrode, an outer electrode and a measurement circuit. The sensor realizes the measurement of small current under high resistance based on the parallel shunt principle, and can meet the needs of online measurement of transformer oil volume resistivity. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0027] Figure 1 A schematic structural diagram of a transformer volume resistivity sensor provided in one embodiment of the present application.
[0028] Figure 2 A flowchart of a transformer volume resistivity measurement method provided in one embodiment of the present application.
[0029] Figure 3 A flow chart of a calibration method for a transformer volume resistivity sensor provided in one embodiment of the present application.
[0030] Figure 4 A flowchart of another transformer volume resistivity measurement method provided in one embodiment of the present application.
[0031] Description of reference numerals:
[0032] 1. Connector; 2. Sensor housing; 3. Circuit board; 4. Housing connection; 5. Oil inlet; 6. Inner electrode; 7. Outer electrode; 8. Temperature sensitive element; 9. Oil outlet. DETAILED DESCRIPTION
[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0034] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0035] In an exemplary embodiment, Figure 1 As shown, a transformer volume resistivity sensor is provided, which comprises: an inner electrode 6, an outer electrode 7 and a measuring circuit; the inner electrode 6 and the outer electrode 7 are both connected to the measuring circuit; the inner electrode 6 is arranged in the outer electrode 7, a cavity is formed between the inner electrode 6 and the outer electrode 7, and an oil inlet 5 and an oil outlet 9 are arranged on the outer electrode 7; the measuring circuit is used to measure the current of the transformer insulating oil between the inner electrode 6 and the outer electrode 7 under a preset voltage based on the parallel shunt principle; the current of the transformer insulating oil between the inner electrode 6 and the outer electrode 7 under the preset voltage is used to calculate the volume resistivity of the transformer insulating oil.
[0036] In another exemplary embodiment, the above-mentioned measurement circuit is arranged on the circuit board 3, and the measurement circuit includes: a voltage source, a parallel resistor, a current sensor and a signal processing circuit; the positive electrode of the voltage source is connected to the positive electrode of the current sensor, the negative electrode of the current sensor is respectively connected to the inner electrode 6 and one end of the parallel resistor, and the outer electrode 7 and the other end of the parallel resistor are connected to the negative electrode of the voltage source; the signal processing circuit includes a signal acquisition circuit, a signal amplification circuit and a single-chip microcomputer connected in sequence; the current sensor is connected to the signal acquisition circuit.
[0037] The single chip microcomputer is used to calculate the current of the transformer insulating oil between the inner electrode 6 and the outer electrode 7 at a preset voltage using the following formula;
[0038]
[0039] Wherein, I is the current of the transformer insulating oil between the inner electrode and the outer electrode at the preset voltage, I 测 is the current output by the current sensor, U is a preset voltage provided by a voltage source, and R is a parallel resistor.
[0040] Among them, is the current of the transformer insulating oil between the inner electrode 6 and the outer electrode 7 under a preset voltage, is the current output by the current sensor, is the preset voltage, and the preset voltage is provided by a voltage source, and is a parallel resistor.
[0041] In another exemplary embodiment, the circuit board 3 is connected to a connector 1 , and the connector 1 is used to output a sensor signal.
[0042] In another exemplary embodiment, the transformer volume resistivity sensor further includes a temperature-sensitive element 8, which is connected to the single-chip microcomputer; the temperature-sensitive element 8 is disposed in a cavity between the inner electrode 6 and the outer electrode 7. Exemplarily, the temperature-sensitive element 8 includes a PT1000 sensing element and a connecting wire, the PT1000 sensing element is fixed to the insulating member and fixed by glue pouring, the connecting wire passes through the insulating member and is connected to the circuit board 3 and is fixed by glue pouring.
[0043] In another exemplary embodiment, the transformer volume resistivity sensor further includes a sensor housing 2, the measuring circuit is disposed in the sensor housing 2, and the inner electrode 6 and the outer electrode 7 are both threadedly connected to the end of the sensor housing 2. Exemplarily, the outer electrode 7 is threadedly connected to the housing connection portion 4 at the end of the sensor housing 2, the inner electrode 6 is threadedly connected to the housing connection portion 4, and the inner and outer electrodes 7 are isolated by an insulating layer.
[0044] In an exemplary embodiment, a transformer volume resistivity measurement method is provided, wherein the transformer volume resistivity measurement method uses the above-mentioned transformer volume resistivity sensor, such as Figure 2 As shown, the transformer volume resistivity measurement method includes the following steps 101 to 103.
[0045] Step 101, obtaining the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage.
[0046] Step 102, calculating the current density of the transformer insulating oil between the inner electrode and the outer electrode according to the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage.
[0047] Step 103, calculating the volume resistivity of the transformer insulating oil according to the current density of the transformer insulating oil between the inner electrode and the outer electrode.
[0048] The formula for calculating the current density of the transformer insulating oil between the inner electrode and the outer electrode is:
[0049] j = I / S;
[0050] Wherein, j is the current density of the transformer insulating oil between the inner electrode and the outer electrode, I is the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage, and S is the cross-sectional area of the cavity between the inner electrode and the outer electrode.
[0051] Among them, the formula for calculating the volume resistivity of transformer insulating oil is:
[0052] ρ=K / σ;
[0053] σ=j / E;
[0054]
[0055] Wherein, ρ is the volume resistivity of the transformer oil insulating oil, K is the electrode constant, σ is the conductivity of the transformer insulating oil, j is the current density of the transformer insulating oil between the inner electrode and the outer electrode, E is the electric field strength, U is the preset voltage, x is any radial position between the inner electrode and the outer electrode, R is the radius of the outer electrode, and r is the radius of the inner electrode.
[0056] In another exemplary embodiment, the above steps 101 and 103 apply a DC constant voltage through the voltage source of the above transformer volume resistivity sensor, and collect the total current of the transformer insulating oil during operation through the inner electrode and the outer electrode of the above transformer volume resistivity sensor. The current and current density of the transformer oil with insulating properties are calculated to detect the volume resistivity of the transformer oil. The measurement principle is as follows:
[0057] (1) Since the conductivity effect of the dielectric will produce a current density J(t) that varies with time, the total current is equal to the sum of the polarization (displacement) current and the conduction current, which is expressed as:
[0058]
[0059] Among them, the total current J(t) is the sum of the conduction current E(t) and the displacement current dD(t) / dt, and σ is the conductivity of the dielectric (i.e., volume resistivity).
[0060] (2) Under the action of DC voltage, there is no periodic polarization process in the dielectric, and the loss in the dielectric is only caused by conductivity. At this time, the displacement current dD(t) / dt=0, so the current density can be expressed as:
[0061] J(t)=σE(t)
[0062] (3) According to the Maxwell equation of electrostatic field, the distribution expression of the electric field voltage U in the insulating medium is:
[0063]
[0064] The electric field strength E inside the electrode x for:
[0065] E x =U / (xln(R / r))
[0066] Where U is the voltage between the inner and outer electrodes, i.e. the preset voltage, e x is the electric field intensity at radius x, Q is the total charge in the Gaussian surface, ε0 is the vacuum dielectric constant, ε r is the relative dielectric constant of the insulating medium, l is the axial length of the insulating electrode;
[0067] (4) According to the current density formula:
[0068] j=I / S
[0069] The actual measured current of the transformer oil by the sensor under a DC constant voltage can be calculated, where j is the current density of the transformer insulating oil between the inner electrode and the outer electrode, I is the current of the transformer insulating oil between the inner electrode and the outer electrode under a preset voltage, and S is the cross-sectional area of the cavity between the inner electrode and the outer electrode.
[0070] In an exemplary embodiment, a calibration method for the transformer volume resistivity sensor is provided, and the calibration method includes the following steps 201 to 204.
[0071] Step 201, prepare a plurality of different calibrated transformer insulating oils, and determine the true value of the volume resistivity of each calibrated transformer insulating oil.
[0072] Step 202: Use a transformer volume resistivity sensor to measure and obtain the current of each type of calibrated transformer insulating oil between the inner electrode and the outer electrode at a preset voltage.
[0073] Step 203 , taking the preset voltage and the current of the calibrated transformer insulating oil between the inner electrode and the outer electrode at the preset voltage as input, and taking the true value of the volume resistivity of the calibrated transformer insulating oil as a label, to construct sample data.
[0074] Step 204, using the sample data to calibrate the volume resistivity calculation model, so that the deviation between the calibration value of the volume resistivity of the calibrated transformer insulating oil output by the volume resistivity calculation model and the true value of the volume resistivity of the calibrated transformer insulating oil is less than a deviation threshold, and a calibrated volume resistivity calculation model is obtained.
[0075] like Figure 3As shown, in another exemplary embodiment, in the above step 201, a real transformer insulating oil with a high impedance value of 0-4×1010Ω·m is prepared by a method of high-temperature cracking and aging of transformer oil, and used as a calibration transformer insulating oil. A volume resistivity tester that complies with GB / T 5654-2007 is used for measurement to obtain the real value of its volume resistivity, thereby solving the problem of no high resistance standard liquid.
[0076] like Figure 3 As shown, in another exemplary embodiment, in the above step 202, a temperature control module with an independent PID algorithm is formulated to achieve temperature control of the calibration transformer insulating oil, the prepared calibration transformer insulating oil is temperature controlled to 90°C, and the current of the calibration transformer insulating oil is measured using a transformer volume resistivity sensor.
[0077] like Figure 3 As shown, in another exemplary embodiment, in the above step 204, the calibration volume resistivity calculation model is calibrated using the current and the real value of the volume resistivity of different calibration transformer insulating oils, so that the deviation between the calibration value of the volume resistivity of the calibration transformer insulating oil output by the volume resistivity calculation model and the real value of the volume resistivity of the calibration transformer insulating oil is less than the deviation threshold, that is, the formula is satisfied. Among them, ρ2 is the true value of the volume resistivity of the calibrated transformer insulating oil, and ρ3 is the calibrated value of the volume resistivity of the calibrated transformer insulating oil.
[0078] In an exemplary embodiment, another transformer volume resistivity measurement method is also provided, such as Figure 4 As shown, the process includes the following steps 301 to 302.
[0079] Step 301, obtaining the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage.
[0080] Step 302, according to the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage, the volume resistivity of the transformer insulating oil is obtained using a calibrated volume resistivity calculation model; the calibrated volume resistivity calculation model is obtained using the calibration method of the above embodiment.
[0081] According to the specific embodiments provided in this application, this application has the following technical effects.
[0082] The transformer volume resistivity sensor of the present application uses the conductivity characteristics of transformer oil to realize the detection of micro-currents in transformer oil by the sensor. At the same time, a calibration method and a measurement method suitable for the transformer volume resistivity sensor are proposed to realize the calibration and measurement of transformer oil by the sensor. Since the volume resistivity sensor of the present application can realize the detection of tiny currents in transformer oil, the voltage change of transformer oil during the test process can be calculated, thereby realizing accurate testing of transformer oil volume resistivity, which is suitable for monitoring the volume resistivity index in high-voltage transformers in power systems.
[0083] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0084] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.
Claims
1. A transformer volume resistivity sensor, characterized in that: The transformer volume resistivity sensor comprises: an inner electrode, an outer electrode and a measuring circuit; The inner electrode and the outer electrode are both connected to the measuring circuit; The inner electrode is arranged inside the outer electrode, a cavity is formed between the inner electrode and the outer electrode, and an oil inlet and an oil outlet are arranged on the outer electrode; The measuring circuit is used to measure the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage based on the parallel shunt principle; the current of the transformer insulating oil between the inner electrode and the outer electrode at the preset voltage is used to calculate the volume resistivity of the transformer insulating oil.
2. The transformer volume resistivity sensor according to claim 1, characterized in that: The measuring circuit comprises: a voltage source, a parallel series resistor, a current sensor and a signal processing circuit; the positive electrode of the voltage source is connected to the positive electrode of the current sensor, the negative electrode of the current sensor is connected to the inner electrode and one end of the parallel resistor respectively, and the other ends of the outer electrode and the parallel resistor are both connected to the negative electrode of the voltage source; The signal processing circuit comprises a signal acquisition circuit, a signal amplification circuit and a single chip microcomputer connected in sequence; The current sensor is connected to the signal acquisition circuit; the single chip microcomputer is used to calculate the current of the transformer insulating oil between the inner electrode and the outer electrode under a preset voltage using the following formula; Wherein, I is the current of the transformer insulating oil between the inner electrode and the outer electrode at the preset voltage, I 测 is the current output by the current sensor, U is a preset voltage provided by a voltage source, and R is a parallel resistor.
3. The transformer volume resistivity sensor according to claim 2, characterized in that: The transformer volume resistivity sensor further comprises a temperature-sensitive element, and the temperature-sensitive element is connected to the single-chip microcomputer; The temperature sensitive element is arranged in a cavity between the inner electrode and the outer electrode.
4. The transformer volume resistivity sensor according to claim 2, characterized in that: The transformer volume resistivity sensor further comprises a sensor housing, the measurement circuit is arranged in the sensor housing, and the inner electrode and the outer electrode are both threadedly connected to the end of the sensor housing.
5. A method for measuring transformer volume resistivity, characterized in that: The transformer volume resistivity measurement method uses the transformer volume resistivity sensor according to any one of claims 1 to 4, and the transformer volume resistivity measurement method comprises the following steps: obtaining the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage; Calculating the current density of the transformer insulating oil between the inner electrode and the outer electrode according to the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage; The volume resistivity of the transformer insulating oil is calculated according to the current density of the transformer insulating oil between the inner electrode and the outer electrode.
6. The transformer volume resistivity measurement method according to claim 5, characterized in that: The formula for calculating the current density of the transformer insulating oil between the inner electrode and the outer electrode is: j = I / S; Wherein, j is the current density of the transformer insulating oil between the inner electrode and the outer electrode, I is the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage, and S is the cross-sectional area of the cavity between the inner electrode and the outer electrode.
7. The transformer volume resistivity measurement method according to claim 5, characterized in that: The formula for calculating the volume resistivity of transformer insulating oil is: ρ=K / σ; σ=j / E; Wherein, ρ is the volume resistivity of the transformer oil insulating oil, K is the electrode constant, σ is the conductivity of the transformer insulating oil, j is the current density of the transformer insulating oil between the inner electrode and the outer electrode, E is the electric field strength, U is the preset voltage, x is any radial position between the inner electrode and the outer electrode, R is the radius of the outer electrode, and r is the radius of the inner electrode.
8. A calibration method for a transformer volume resistivity sensor according to any one of claims 1 to 4, characterized in that: The calibration method comprises the following steps: Prepare a plurality of different standard transformer insulating oils and determine the true value of the volume resistivity of each standard transformer insulating oil; Using a transformer volume resistivity sensor to measure and obtain the current of each calibrated transformer insulating oil between the inner electrode and the outer electrode at a preset voltage; The preset voltage and the current of the calibrated transformer insulating oil between the inner electrode and the outer electrode at the preset voltage are used as input, and the true value of the volume resistivity of the calibrated transformer insulating oil is used as a label to construct sample data; The sample data is used to calibrate a volume resistivity calculation model so that a deviation between a calibration value of the volume resistivity of the calibrated transformer insulating oil output by the volume resistivity calculation model and a true value of the volume resistivity of the calibrated transformer insulating oil is less than a deviation threshold, thereby obtaining a calibrated volume resistivity calculation model.
9. The calibration method according to claim 8, characterized in that: The volume resistivity calculation model is a neural network model or a mathematical function model.
10. A method for measuring transformer volume resistivity, characterized in that: The transformer volume resistivity measurement method comprises the following steps: obtaining the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage; According to the current of the transformer insulating oil between the inner electrode and the outer electrode at a preset voltage, the volume resistivity of the transformer insulating oil is obtained using a calibrated volume resistivity calculation model; the calibrated volume resistivity calculation model is obtained using the calibration method described in any one of claims 8-9.