A model building method for closing resistor quality detection

Abstract

A model establishment method for closing resistor quality detection, in which a closing resistor model is established based on electrical parameters and a geometric model of the closing resistor, the electrical parameters of the closing resistor including conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity, a closing resistor quality detection simulation numerical model is established based on the closing resistor model and the closing resistor electrical parameters, the closing resistor quality detection simulation numerical model includes an impulse current waveform, a temperature characteristic of the closing resistor and a stress characteristic of the closing resistor which are arranged in sequence, an impulse current based on the impulse current waveform is injected into the closing resistor quality detection simulation numerical model, and a limit value of the impulse current that the closing resistor can withstand is calculated to simulate and optimize the closing resistor quality detection simulation numerical model.

Description

Technical Field

[0001] The present invention relates to the technical field of closing resistor quality detection, and in particular to a model building method for closing resistor quality detection. Background Art

[0002] Tank circuit breakers are considered to be one of the key equipment in UHV substations. In order to ensure the normal operation of high-voltage transmission lines and substation systems, a sufficient number of reliable tap changers must be used to cooperate. In the process of opening and closing the circuit breaker, closing resistors are often used to reduce the inrush current phenomenon during closing. High-voltage DC transmission projects all use phase switching to transmit power, and most of them are equipped with circuit breaker closing resistors. During long-term operation, the closing resistor of the circuit breaker will not only be subjected to strong mechanical pressure, but also be affected by the impact current generated during the closing process. In mild cases, problems such as contact arcing, loose components or jamming may occur, while in severe cases, the closing resistor may catch fire or explode. Due to the impact of long-term opening and closing operations, the surface of the closing resistor may be damaged, and even resistor fragments may fall off. These scattered resistor fragments may cause power outages during the operation of the circuit breaker, posing a major threat to the stable operation of the power grid.

[0003] The problems with closing resistors can be divided into two main categories:

[0004] (1) The closing resistor is subjected to huge mechanical stress during the opening and closing process, which will cause microcracks on the surface of the closing resistor. These microcracks will not only affect the electrical properties of the closing resistor, but also affect the compressive strength at the location of the microcracks, thereby reducing the closing resistor's ability to withstand current.

[0005] (2) When the closing resistor is subjected to the impact current, due to its semiconductor properties, this will undoubtedly cause the closing resistor temperature to rise. Therefore, resistor fragments on the surface of the closing resistor may fall to the bottom of the tank, and a current channel may be formed between these fragments and the closing resistor, resulting in the occurrence of flashover.

[0006] Due to the large current difference between the tap changer and the busbar and the serious overvoltage caused by the arc discharge process, the closing shock problem occurs, resulting in system failure or even large-scale power outages.

[0007] The above 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

[0008] The present invention provides a model building method for closing resistor quality detection, which accurately builds and detects the impact current limit value of the closing resistor, and can evaluate the influence of the closing resistor material components to ensure the stable operation of the power system.

[0009] A model building method for closing resistor quality detection includes:

[0010] The closing resistor model is established based on the electrical parameters and geometric model of the closing resistor. The electrical parameters of the closing resistor include conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity.

[0011] A closing resistor quality detection simulation numerical model is established based on the closing resistor model and the closing resistor electrical parameters. The closing resistor quality detection simulation numerical model includes an impact current waveform, a closing resistor temperature characteristic, and a closing resistor stress characteristic which are sequentially arranged.

[0012] An impulse current based on the impulse current waveform is injected into a closing resistor quality detection simulation numerical model, and a limit value of the impulse current that the closing resistor can withstand is calculated to simulate and optimize the closing resistor quality detection simulation numerical model.

[0013] In the model establishment method for closing resistor quality detection, whether the maximum value of thermal stress at the current injection point exceeds the standard compressive strength, if not, the amplitude and waveform of the impact current are adjusted to be injected into the closing resistor quality detection simulation numerical model to calculate the limit value of the impact current that the closing resistor can withstand, until the maximum value of thermal stress at the current injection point exceeds the standard compressive strength, and the maximum value of the impact current that the closing resistor quality detection simulation numerical model can withstand is obtained.

[0014] In the model establishment method for closing resistor quality detection, the geometric model is a needle-plate model, the radius R of the needle tip in the needle-plate model is adjusted according to the withstand voltage level of the closing resistor, and the detection current is injected into the closing resistor through the needle electrode to perform closing resistor quality detection.

[0015] In the model building method for closing resistor quality detection, the electrical contact area between the ceramic materials of the needle plate model is at the micron level.

[0016] In the model building method for closing resistor quality detection, the closing resistor is arranged in a tank circuit breaker.

[0017] In the model building method for closing resistor quality detection, the value range of the needle tip radius R of the needle electrode is 0.001m~0.005m.

[0018] In the model building method for closing resistor quality detection, the closing resistor is arranged in a tank circuit breaker.

[0019] In the model building method for closing resistor quality detection, the temperature characteristics include specific heat capacity, and the stress characteristics include Young's modulus and thermal expansion coefficient.

[0020] Compared with the prior art, the present invention has the following advantages: the present invention accurately establishes and detects the impact current limit value of the closing resistor, and can evaluate the influence of the material components of the closing resistor, thereby ensuring the stable operation of the power system and reducing the adverse effect of the closing surge current on the closing resistor; the connection method and structure of the tank circuit breaker are optimized to ensure that the closing resistor can operate reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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.

[0022] In the attached picture:

[0023] Figure 1 It is a schematic diagram of the process of the present invention;

[0024] Figure 2 It is a front view schematic diagram of the needle plate electrode model of the present invention;

[0025] Figure 3 Schematic diagram of the needle electrode in the needle-plate electrode model of the present invention;

[0026] Figure 4 It is a schematic diagram of the structure of the closing resistance model of the present invention;

[0027] Figure 5 This is a schematic diagram of the needle plate electrode model of the present invention loaded with a closing resistor;

[0028] Figure 6 is a schematic diagram of an impact current according to an embodiment of the present invention;

[0029] Figure 7 It is a temperature variation diagram of an embodiment of the present invention;

[0030] Figure 8 Graph showing average stress variation in an embodiment of the present invention.

[0031] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0032] 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 fully convey the scope of the present invention to those skilled in the art.

[0033] 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.

[0034] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0035] like Figures 1 to 7 As shown, the model building method for closing resistance quality detection includes the following steps:

[0036] The closing resistor model is established based on the electrical parameters and geometric model of the closing resistor. The electrical parameters of the closing resistor include conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity. The important physical parameters of the closing resistor are shown in Table 1:

[0037] Table 1 Important physical parameters of closing resistor

[0038]

[0039] A closing resistor quality detection simulation numerical model is established based on the closing resistor model and the closing resistor electrical parameters. The closing resistor quality detection simulation numerical model includes an impact current waveform, a closing resistor temperature characteristic, and a closing resistor stress characteristic which are sequentially arranged.

[0040] An impulse current based on the impulse current waveform is injected into a closing resistor quality detection simulation numerical model, and a limit value of the impulse current that the closing resistor can withstand is calculated to simulate and optimize the closing resistor quality detection simulation numerical model.

[0041] In a preferred implementation of the model establishment method for closing resistor quality detection, whether the maximum value of thermal stress at the current injection point exceeds the standard compressive strength, if not, the amplitude and waveform of the impact current are adjusted to be injected into the closing resistor quality detection simulation numerical model to calculate the limit value of the impact current that the closing resistor can withstand, until the maximum value of thermal stress at the current injection point exceeds the standard compressive strength, and the maximum value of the impact current that the closing resistor quality detection simulation numerical model can withstand is obtained.

[0042] In a preferred implementation of the model establishment method for closing resistor quality detection, the geometric model is a needle-plate model, the radius R of the needle tip in the needle-plate model is adjusted according to the withstand voltage level of the closing resistor, and the detection current is injected into the closing resistor through the needle electrode to perform closing resistor quality detection.

[0043] In a preferred implementation of the model building method for closing resistor quality detection, the electrical contact area between the ceramic materials of the needle plate model is at the micron level.

[0044] In a preferred implementation of the model building method for closing resistor quality detection, the closing resistor is provided in a tank circuit breaker.

[0045] In a preferred implementation of the model building method for closing resistance quality detection, the radius R of the needle tip of the needle electrode ranges from 0.001m to 0.005m, which is consistent with the area size of the electrical contact in the electrical contact theory.

[0046] In a preferred implementation of the model building method for closing resistor quality detection, the closing resistor is provided in a tank circuit breaker.

[0047] In a preferred implementation of the model building method for closing resistor quality detection, the temperature characteristics include specific heat capacity, and the stress characteristics include Young's modulus and thermal expansion coefficient.

[0048] In one embodiment, see Figures 1 to 8, a model method for closing resistor quality detection, the method includes the following steps in sequence: (1) combining the material parameters of the closing resistor, using COMSOL simulation software to build a closing resistor quality detection simulation model; closing resistor quality detection simulation model: 1. Establishment of the needle-plate electrode model, the radius size of the plate electrode and the cone radius size of the needle electrode; 2. Setting the basic model specifications, conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity of the closing resistor to improve the accuracy of the model, setting the peak value, peak time and half-peak time of the impulse current, as well as the closing resistor input time, etc. to accurately establish the model, (2) By comparing the thermal stress of the closing resistor with the standard compressive strength, it is determined whether the closing resistor is failed, thereby achieving the purpose of quality detection, providing an accurate basis for the closing resistor quality detection, and verifying the accuracy of the simulation, as well as correcting the simulation model, optimizing the grounding network model, and obtaining a unified model of the substation grounding network, such as Figure 1 shown.

[0049] The embodiment uses three impulse currents of different amplitudes, with a flow time of about 10ms. Figure 6 As shown in the figure, by setting different impulse currents, the accuracy of the closing resistance quality detection modeling based on the equivalent destruction principle under two conditions of temperature change and stress change is analyzed.

[0050] Numerical simulation is performed by injecting an impulse current of the above waveform into the closing resistor. The impulse current waveform is fitted according to the actual current waveform by simulation software, and the electric energy is highly consistent with the actual current waveform, which can ensure that the simulation is highly similar to the actual experimental results.

[0051] Depend on Figure 7 It can be seen that, overall, the temperature is in a process of continuous increase, with a short period of flatness in the middle. As the impact current changes from positive to negative, the temperature rise rate changes from fast to slow. From the waveform analysis, it can be seen that the maximum temperature is 356.1℃. As the impact current increases from 1.16kA to 2.54kA, the temperature of the closing resistor shows a continuous upward trend. Analysis shows that as the impact current amplitude continues to increase, the energy generated by the impact current will continue to increase, the current will be converted into more heat, the energy will increase, and then the temperature change will increase. The temperature change curve conforms to the formula derivation.

[0052] Depend on Figure 8 It can be seen that there is a direct relationship between stress and temperature, so that the change in stress is highly similar to the change in temperature. Analysis shows that the change in temperature is proportional to the change in stress, and the proportionality coefficient is the product of Young's modulus and the thermal expansion coefficient. As the impulse current amplitude increases, the temperature difference will increase, and the increase in temperature difference leads to an increase in thermal stress. When the thermal stress exceeds the standard compressive strength threshold of the closing resistor, it is determined that the closing resistor has reached the failure threshold, so as to achieve the closing resistor quality detection.

[0053] In the above analysis results, the closing resistor quality detection modeling includes various parameter indicators of the closing resistor and the impulse current waveform. When the thermal stress of the closing resistor reaches the standard compressive strength threshold of the closing resistor, the quality detection of the closing resistor is achieved.

[0054] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.

Claims

1. A model building method for closing resistor quality detection, characterized in that: The steps include: The closing resistor model is established based on the closing resistor electrical parameters and geometric model. The closing resistor electrical parameters include conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity. A closing resistor quality detection simulation numerical model is established based on the closing resistor model and the closing resistor electrical parameters. The closing resistor quality detection simulation numerical model includes an impact current waveform, a closing resistor temperature characteristic, and a closing resistor stress characteristic which are sequentially arranged. Injecting an impulse current into a closing resistor quality detection simulation numerical model based on the impulse current waveform, calculating a limit value of the impulse current that the closing resistor can withstand to simulate and optimize the closing resistor quality detection simulation numerical model; Among them, the electrical contact area between the ceramic materials of the needle-plate model is at the micrometer level; The radius R of the needle tip of the needle electrode ranges from 0.001m to 0.005m.

2. A model building method for closing resistor quality detection according to claim 1, characterized in that: The closing resistor is arranged in the tank type circuit breaker.

3. The model building method for closing resistor quality detection according to claim 1 is characterized in that: The temperature properties include specific heat capacity, and the stress properties include Young's modulus and thermal expansion coefficient.

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