Method and system for calculating average temperature of arc discharge products in transformer oil tank

Abstract

The invention discloses a method and system for calculating the average temperature of arc discharge products in a transformer oil tank, and the method comprises the steps: carrying out an arc discharge experiment in a sealed oil-filled tank body of transformer oil, and measuring the arc discharge voltage, current and pressure waveform, the volume of the arc discharge products at room temperature, and the corresponding pressure in the oil tank; the time-varying temperature T (t) of the discharge product during arcing is obtained by calculating the discharge static pressure pL (t) obtained by measurement; calculating the temperature of a discharge product after arc quenching; and obtaining an average temperature change curve of the discharge product at different time stages based on the time-varying temperature of the discharge product during arcing and the average temperature of the discharge product after arc quenching.

Description

Technical Field

[0001] The invention relates to the technical field of transformer detection, and in particular to a method and system for calculating the average temperature of arc discharge products in a transformer oil tank. Background Art

[0002] When a short circuit occurs in the transformer tank, arc discharge will cause local high temperature, decompose the insulating oil and generate gas. The gas expansion causes pressure increase, which is an important reason for the tank to burst. Existing research focuses on pressure calculation, but lacks an accurate model for the temperature distribution and average temperature of gas products. Gas temperature is a key parameter for calculating pressure change, so it is of great significance to study the average temperature of arc discharge products.

[0003] The information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0004] In view of the shortcomings or defects of the prior art, a method and system for calculating the average temperature of arc discharge products in a transformer oil tank are provided to accurately reflect the average temperature of the discharge products.

[0005] The purpose of the present invention is achieved through the following technical solutions.

[0006] A method for calculating the average temperature of arc discharge products in a transformer oil tank includes:

[0007] Carry out arc discharge experiments in a sealed oil-filled tank of transformer oil, measure the arc discharge voltage, current and pressure waveforms, the volume of arc discharge products at room temperature and the corresponding pressure in the oil tank;

[0008] The time-varying temperature T(t) of the discharge product during arcing is measured to obtain the discharge static pressure p L (t) is calculated as,

[0009] Calculate the gas temperature after arc extinction, Where T(t) is the time-varying temperature of the discharge product; c is the expansion coefficient of the oil tank; p L (t) is the static discharge pressure; T 0 is the ambient temperature, i.e. room temperature; p 0 is atmospheric pressure; V g V is the volume of gas produced by discharge converted to normal temperature and pressure; 0 The volume of gas reserved in the tank.

[0010] Based on the time-varying temperature of the discharge products during arcing and the average temperature of the discharge products after arcing, the average temperature variation curves of the discharge products at different time stages are obtained.

[0011] In the method for calculating the average temperature of arc discharge products in the transformer oil tank, since the arc plasma temperature is as high as 2000-7000K, a large number of oil molecules and gas molecules will undergo thermal dissociation, and arc discharge will produce a large number of ions and radicals, which are therefore called discharge products.

[0012] In the method for calculating the average temperature of arc discharge products in the transformer oil tank, a Rogowski coil and a high-voltage differential probe are used to measure the discharge current and arc discharge voltage, and a pressure sensor and a gas / liquid dual-purpose pressure gauge are used to measure the dynamic pressure waveform generated by the discharge and the steady-state pressure after the discharge ends.

[0013] In the method for calculating the average temperature of arc discharge products in the transformer oil tank, the same capacitor charging voltage, loop parameters and electrode distance are set to ensure that the current waveform of the arc discharge is consistent, and the arcing time is controlled by the vacuum fast circuit breaker to achieve the purpose of changing the arc energy.

[0014] In the method for calculating the average temperature of arc discharge products in the transformer oil tank, arc energy is calculated based on the measured arc discharge voltage and current waveforms. Since the relationship between the gas production and the arc energy is fitted as a linear relationship, the gas production can be calculated from the arc energy.

[0015] A system for implementing a method for calculating the average temperature of arc discharge products in a transformer tank includes:

[0016] Arc discharge experimental platform, which is used to carry out arc discharge experiments in a sealed oil-filled tank of transformer oil, measure arc discharge voltage, current and pressure waveforms, as well as the volume of arc discharge products at room temperature and the corresponding pressure in the oil tank;

[0017] The time-varying temperature calculation unit of the discharge product during arcing is used to calculate the discharge static pressure p obtained by measuring the time-varying temperature T(t) of the discharge product during arcing. L (t) is calculated,

[0018] A time-varying temperature calculation unit for discharge products after arc extinction, which is used to calculate the temperature of the discharge products after arc extinction;

[0019] The arc discharge product average temperature calculation unit obtains the average temperature of the arc discharge product in the transformer oil tank based on the time-varying temperature of the discharge product during arcing and the temperature of the discharge product after arc extinction.

[0020] In the system, the arc discharge experimental platform includes a closed oil-filled box of transformer oil, an RLC circuit for arc discharge, a Rogowski coil and a high-voltage differential probe for measuring arc discharge voltage, current and pressure waveforms, and a pressure sensor for measuring the volume of arc discharge products at room temperature and the corresponding pressure in the oil tank.

[0021] In the system, the RLC circuit of arc discharge includes a high-voltage DC power supply, a capacitor, an inductor and a vacuum fast circuit breaker.

[0022] In the system, the capacitor is a pulse capacitor bank.

[0023] The system also includes a gas collection and volume statistics system for collecting the volume of discharge products, which includes a buffer bottle and a drainage and gas collection device connected to the buffer bottle via a ball valve.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention analyzes the temperature variation characteristics of the arc discharge process by combining multi-dimensional data such as the electrical parameters, pressure waveform, and gas product behavior of the arc discharge. This method not only reveals the dynamic variation law of the temperature of the arc discharge product, but also makes the calculation results closer to the actual working conditions.

[0026] The above description is only an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer and to achieve the extent that those skilled in the art can implement it according to the contents of the specification, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are exemplified below. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0028] In the attached picture:

[0029] Figure 1 It is a flow chart of a method for calculating the average temperature of arc discharge products in a transformer tank;

[0030] Figure 2 It is a schematic diagram of the arc discharge bubble observation, electrical parameters, gas production, and pressure waveform measurement platform;

[0031] Figure 3 This is a schematic diagram of a method for calculating the time-varying temperature of gas production by back-calculating the discharge static pressure;

[0032] Figure 4(a) and Figure 4(b) show the energy and gas production corresponding to different arcing times at the same current;

[0033] Figure 5 It is a schematic diagram of the average temperature change of arc discharge products.

[0034] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0035] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0036] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0037] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0038] For a better understanding, Figures 1 to 5 As shown, a method for calculating the average temperature of arc discharge products in a transformer oil tank includes:

[0039] Carry out arc discharge experiments in a sealed oil-filled tank of transformer oil, measure the arc discharge voltage, current and pressure waveforms, the volume of arc discharge products at room temperature and the corresponding pressure in the oil tank;

[0040] The discharge static pressure p is obtained by measuring the time-varying temperature T(t) of the gas produced during arcing. L (t) is calculated as,

[0041] Calculate the gas temperature after arc extinction,

[0042] Based on the time-varying temperature of the discharge products during arcing and the average temperature of the discharge products after arc extinction, the average temperature variation curves of the discharge products at different time stages are obtained.

[0043] In the preferred embodiment of the method for calculating the average temperature of arc discharge products in the transformer oil tank, since the arc plasma temperature is as high as 2000-7000K, a large number of oil molecules and gas molecules will undergo thermal dissociation, and the arc discharge will produce a large number of ions and radicals, which are therefore called discharge products.

[0044] In a preferred embodiment of the method for calculating the average temperature of arc discharge products in a transformer oil tank, a Rogowski coil and a high-voltage differential probe are used to measure the discharge current and arc discharge voltage, and a pressure sensor and a gas / liquid dual-purpose pressure gauge are used to measure the dynamic pressure waveform generated by the discharge and the steady-state pressure after the discharge ends.

[0045] In the preferred implementation of the method for calculating the average temperature of arc discharge products in the transformer oil tank, the same capacitor charging voltage, loop parameters and electrode distance are set to ensure that the current waveform of the arc discharge is consistent, and the arcing time is controlled by the vacuum fast circuit breaker to achieve the purpose of changing the arc energy.

[0046] In a preferred embodiment of the method for calculating the average temperature of arc discharge products in the transformer oil tank, the arc energy is calculated based on the measured arc discharge voltage and current waveforms. Since the relationship between the gas production and the arc energy is fitted as a linear relationship, the gas production can be calculated from the arc energy.

[0047] A system for implementing a method for calculating the average temperature of arc discharge products in a transformer oil tank includes:

[0048] Arc discharge experimental platform, which is used to carry out arc discharge experiments in a sealed oil-filled tank of transformer oil, measure arc discharge voltage, current and pressure waveforms, as well as the volume of arc discharge products at room temperature and the corresponding pressure in the oil tank;

[0049] The time-varying temperature calculation unit of the discharge product during arcing is used to calculate the discharge static pressure p obtained by measuring the time-varying temperature T(t) of the discharge product during arcing. L (t) is calculated,

[0050] A time-varying temperature calculation unit for discharge products after arc extinction, which is used to calculate the temperature of the discharge products after arc extinction;

[0051] Based on the time-varying temperature of the discharge products during arcing and the average temperature of the discharge products after arcing, the average temperature variation curves of the discharge products at different time stages are obtained.

[0052] In a preferred embodiment of the system, the arc discharge experimental platform includes a closed oil-filled tank of transformer oil, an RLC circuit for arc discharge, a Rogowski coil and a high-voltage differential probe for measuring arc discharge voltage, current and pressure waveforms, and a pressure sensor for measuring the volume of arc discharge products at room temperature and the corresponding pressure in the oil tank.

[0053] In a preferred embodiment of the system, the RLC circuit of the arc discharge includes a high-voltage DC power supply, a capacitor and an inductor, and a vacuum fast circuit breaker.

[0054] In a preferred embodiment of the system, the capacitor is a pulse capacitor bank.

[0055] In a preferred embodiment of the system, a gas collection and volume statistics system for collecting the volume of discharge products is also included, which includes a buffer bottle and a drainage and gas collection device connected to the buffer bottle via a ball valve.

[0056] In one embodiment, a method for calculating the average temperature of arc discharge products in a transformer oil tank includes:

[0057] Carry out arc discharge experiments in a sealed box filled with transformer oil, measure the arc discharge voltage, current and pressure waveforms, the volume of arc discharge products at room temperature and the corresponding pressure in the oil tank;

[0058] The calculation method of time-varying temperature of gas production is obtained by back-calculating the static pressure of discharge;

[0059] Carry out a large number of arc discharge experiments with the same current waveform and different arc energies, obtain the time-varying arc discharge energy and gas production, and analyze the relationship between arc discharge energy and gas production;

[0060] The average temperature of the arc products is obtained by inferring the arc pressure and arc energy according to the ideal gas state equation. The calculation method of the average temperature of the discharge products after arc extinction derived based on Fourier's heat conduction law is verified and compared with the average temperature of the arc products obtained by inferring the arc pressure and arc energy according to the ideal gas state equation.

[0061] In a preferred embodiment of the method, the RLC circuit of arc discharge includes a high-voltage DC power supply, a capacitor, an inductor and a vacuum fast circuit breaker.

[0062] In a preferred embodiment of the method, the current and voltage are measured using a Rogowski coil and a high voltage differential probe.

[0063] In the preferred embodiment of the method, the dynamic pressure waveform generated by the discharge and the steady-state pressure after the discharge are measured using a PCB102B06 pressure sensor and a gas / liquid dual-purpose pressure gauge, respectively.

[0064] In a preferred embodiment of the method, after the experiment, the volume of the gas generated by the discharge is statistically analyzed and its volume under normal pressure is measured using a water displacement gas collection method.

[0065] In a preferred embodiment of the method, the same capacitor charging voltage, circuit parameters, and electrode distance are set to ensure that the current waveform of the arc discharge is consistent, and the arcing time is controlled by a vacuum fast circuit breaker to achieve the purpose of changing the arc energy.

[0066] In a preferred embodiment of the method, arc discharge experiments with different boundary conditions are carried out by changing the oil filling amount in the oil tank, the material of the oil tank, and the structural size of the oil tank to change the boundary conditions of the arc discharge.

[0067] In one embodiment, the method includes,

[0068] Carry out arc discharge experiments in a sealed box filled with transformer oil, measure the arc discharge voltage, current and pressure waveforms and the volume of arc discharge products;

[0069] A method for calculating the time-varying temperature of gas production is obtained by back-calculating the formula provided by the present invention based on the static pressure of the discharge;

[0070] Carry out a large number of arc discharge experiments with the same current waveform and different arc energies, obtain the time-varying arc discharge energy and gas production, and analyze the relationship between arc discharge energy and gas production;

[0071] According to the ideal gas state equation, the average temperature of the arc discharge product can be obtained by inverse calculation from the discharge static pressure and the arc gas production;

[0072] Based on Fourier's heat conduction law, considering the heat conduction process between the discharge product and the transformer oil, the calculation method of the average temperature of the discharge product after arc extinction is derived, T g (t) = T L +[T g (t)-T L ]e -αt The average temperature of the arc products was obtained by inverse calculation of the arc pressure and arc energy according to the ideal gas state equation for verification and comparison.

[0073] In this implementation case, an arc discharge experimental platform in oil is built based on the RLC circuit, including the electrical parameter measurement of voltage and current, gas production volume statistics, discharge transient pressure measurement, etc. The schematic diagram of the experimental platform is shown in the figure. Figure 2 ;

[0074] In this implementation case, the calculation method of the time-varying temperature of gas production can be obtained based on the back calculation of the discharge static pressure. The derivation process is as follows: Figure 3 As shown, the specific method is as follows:

[0075] The liquid pressure measurement result is a gauge pressure. When calculating the pressure inside the bubble in the closed box, the gauge pressure needs to be converted into absolute pressure. Thus, the calculation method of the time-varying temperature of gas production obtained by back-calculating the discharge static pressure is obtained, as shown in formula (1).

[0076]

[0077] When the arc is extinguished, the amount of gas-generating substance n(t) remains unchanged. The pressure drop in the oil at this time is caused by the decrease in gas-generating temperature. Therefore, T(t) can be measured by the pressure sensor to obtain p L (t) is calculated. Finally, the discharge gas production temperature drops to room temperature, and the gas production temperature drop process in the steady-state pressure stage can be calculated by formula (2).

[0078]

[0079] In this embodiment, the current waveform of the arc discharge is ensured to be consistent, the arcing time is controlled by a vacuum fast circuit breaker, the discharge energy of the arc is changed, and a large number of experiments are carried out inside different tanks. It is found that the discharge gas production and the arc energy can be approximately expressed using a linear relationship, as shown in Figure 4 (a) and Figure 4 (b). The gas production is about 150mL / kJ. The arc energy gas production conversion coefficient β is introduced to describe the relationship between the arc energy and the gas production. According to the definition of the arc energy gas production coefficient β, the arc gas production equation can be written as:

[0080] n(t)=βW arc (t)(3)

[0081] Where β is the arc energy gas conversion coefficient, W arc (t) is the arc energy.

[0082] In this implementation case, the calculation method of the average temperature of the discharge product after arc extinction derived from Fourier's heat conduction law is verified and compared with the average temperature of the arc product obtained by inverse calculation of the arc pressure and arc energy according to the ideal gas state equation, such as Figure 5 As shown, with the continuous injection of arc energy, the average temperature of the discharge product gradually decreases from the instantaneous high temperature at the beginning of the arc and tends to be stable. During the continuous injection of arc energy, the average temperature of the discharge product is about 2000-8000K. As the arc is extinguished, due to the lack of continuous energy injection, the gas production temperature gradually decreases to room temperature. The calculation results of the average temperature calculation method of arc products established based on the two methods are basically consistent. The present disclosure reveals the temperature change law of arc discharge products and proposes a method for calculating the average temperature of arc discharge products in the oil tank. The invention can be used for research on transformer explosion protection and provides a basis for dynamic pressure simulation calculation.

[0083] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0084] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A method for calculating the average temperature of arc discharge products in a transformer oil tank, characterized in that: These include, Carry out arc discharge experiments in a sealed oil-filled tank of transformer oil, measure the arc discharge voltage, current and pressure waveforms, the volume of arc discharge products at room temperature and the corresponding pressure in the oil tank; The discharge static pressure p is obtained by measuring the time-varying temperature T(t) of the gas produced during arcing. L (t) is calculated as, Calculate the gas temperature after arc extinction, Based on the time-varying temperature of the discharge products during arcing and the average temperature of the discharge products after arc extinction, the average temperature variation curves of the discharge products at different time stages are obtained. Where T(t) is the time-varying temperature of the discharge product; c is the expansion coefficient of the oil tank; p L (t) is the static discharge pressure; T0 is the ambient temperature, i.e. room temperature; p0 is the atmospheric pressure; V g It is the volume of gas produced during discharge converted to normal temperature and pressure; V0 is the volume of gas reserved in the tank.

2. The method for calculating the average temperature of arc discharge products in a transformer oil tank according to claim 1, characterized in that: Preferably, since the temperature of the arc plasma is as high as 2000-7000K, a large number of oil molecules and gas molecules will undergo thermal dissociation, and the arc discharge will produce a large number of ions and radicals, which are therefore called discharge products.

3. The method for calculating the average temperature of arc discharge products in a transformer oil tank according to claim 1, characterized in that: The discharge current and arc discharge voltage were measured using a Rogowski coil and a high-voltage differential probe, and the dynamic pressure waveform generated by the discharge and the steady-state pressure after the discharge were measured using a pressure sensor and a gas / liquid dual-purpose pressure gauge.

4. The method for calculating the average temperature of arc discharge products in a transformer oil tank according to claim 1, characterized in that: The same capacitor charging voltage, circuit parameters and electrode distance are set to ensure the consistency of the arc discharge current waveform. The arc burning time is controlled by the vacuum fast circuit breaker to achieve the purpose of changing the arc energy.

5. The method for calculating the average temperature of arc discharge products in a transformer oil tank according to claim 1, characterized in that: The arc energy is calculated based on the measured arc discharge voltage and current waveforms. Since the relationship between the discharge gas production and the arc energy is fitted as a linear relationship, the gas production can be calculated from the arc energy.

6. A system for implementing the method for calculating the average temperature of arc discharge products in a transformer oil tank according to any one of claims 1 to 5, characterized in that: These include, Arc discharge experimental platform, which is used to carry out arc discharge experiments in a sealed oil-filled tank of transformer oil, measure arc discharge voltage, current and pressure waveforms, as well as the volume of arc discharge products at room temperature and the corresponding pressure in the oil tank; The time-varying temperature calculation unit of the discharge product during arcing is used to calculate the time-varying temperature T(t) of the discharge product during arcing by measuring the discharge static pressure p L (t) is calculated, A time-varying temperature calculation unit for discharge products after arc extinction, which is used to calculate the temperature of the discharge products after arc extinction; The arc discharge product average temperature calculation unit obtains the discharge product average temperature variation curves at different time stages based on the time-varying temperature of the discharge product during arcing and the average temperature of the discharge product after arcing.

7. The system according to claim 6, characterized in that The arc discharge experimental platform includes a closed oil-filled tank of transformer oil, an RLC circuit for arc discharge, a Rogowski coil and a high-voltage differential probe for measuring the arc discharge voltage, current and pressure waveforms, and a pressure sensor for measuring the volume of arc discharge products at room temperature and the corresponding pressure in the oil tank.

8. The system according to claim 7, characterized in that The RLC circuit of arc discharge includes a high voltage DC power supply, capacitors and inductors, and a vacuum fast circuit breaker.

9. The system according to claim 8, characterized in that The capacitor is a pulse capacitor bank.

10. The system according to claim 6, characterized in that It also includes a gas collection and volume statistics system for collecting the volume of discharge products, which includes a buffer bottle and a drainage and gas collection device connected to the buffer bottle via a ball valve.

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