A modeling method for closing resistor quality detection based on equivalent damage principle

Abstract

A closing resistor quality detection modeling method based on the equivalent destruction principle, in which a closing resistor model is established based on the electrical parameters and geometric model of the closing resistor, the closing resistor conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity of the closing resistor model are set, and a closing resistor equivalent destruction simulation numerical model is established based on the closing resistor model and the electrical parameters of the closing resistor, the closing resistor equivalent destruction simulation numerical model includes an impulse current waveform, a contact mode between closing resistors and a temperature characteristic of the closing resistor, which are set in sequence, and an impulse current injection into the closing resistor equivalent destruction simulation numerical model is formed based on the equivalent modeling of the closing resistor equivalent destruction simulation numerical model, and the limit value of the impulse current that the closing resistor can withstand is calculated to simulate and optimize the closing resistor equivalent destruction simulation numerical model.

Description

Technical Field

[0001] The invention relates to the technical field of tank circuit breaker detection, and in particular to a closing resistance quality detection modeling method based on the equivalent destruction principle. Background Art

[0002] Tank circuit breakers are one of the main equipment in UHV substations. Closing resistors are usually used to suppress the closing surge current during the opening and closing process of circuit breakers. During long-term operation, the closing resistor of the circuit breaker will not only be subjected to huge mechanical forces, but also to the impact of the impact current brought by the closing process. In mild cases, faults such as contact arcing, loose parts, and jamming may occur. In severe cases, fire or explosion may occur. The surface of the closing resistor may be damaged under the impact of long-term opening and closing operations, and even resistor debris may fall off. The scattered resistor fragments may cause power outages during the operation of the circuit breaker, which will have a serious impact on the reliability of the power grid operation. The failures of the closing resistor can be mainly divided into the following two aspects:

[0003] (1) The closing resistor is subjected to huge mechanical stress during the opening and closing process, which causes some microcracks on the surface of the closing resistor. The microcracks will affect the electrical properties of the closing resistor and the compressive strength at the microcracks will definitely be affected, so that the closing resistor will be able to withstand a certain amount of current.

[0004] (2) The closing resistor is injected with impact current. Since the closing resistor is a semiconductor, it will inevitably cause the closing resistor to heat up, so that resistor debris on the surface of the closing resistor will fall off to the bottom of the tank. The resistor debris that falls on the bottom of the tank will form a current channel between the closing resistor and the closing resistor, causing flashover.

[0005] In view of the hazards of the above two situations, domestic and foreign power research institutions continue to study the closing resistance of tank circuit breakers. The research mainly includes the following aspects: first, by optimizing the opening and closing operation process, the influence of the closing surge current on the closing resistance is reduced; second, by studying the internal material components of the closing resistance, the components of the closing resistance are adjusted to obtain the optimal closing resistance material formula; third, the connection structure and connection method of the tank circuit breaker are optimized to ensure the reliable operation of the closing resistance. It can be seen from the above research that the establishment of the closing resistance model of the tank circuit breaker has not been realized at present, and it is necessary to perform equivalent modeling on the quality detection of the closing resistance for the subsequent safe operation of the power system.

[0006] 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

[0007] The present invention provides a closing resistor quality detection modeling method based on the equivalent destruction principle, which can not only accurately establish the impact current limit value of the closing resistor, but also evaluate the influence of the closing resistor material components to ensure the stable operation of the power system.

[0008] A closing resistor quality detection modeling method based on the equivalent damage principle includes:

[0009] A closing resistor model is established based on the electrical parameters and geometric model of the closing resistor. The electrical parameters include the closing resistor conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity, and the closing resistor conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity are set as the closing resistor model.

[0010] A closing resistor equivalent damage simulation numerical model is established based on the closing resistor model and the electrical parameters of the closing resistor, wherein the closing resistor equivalent damage simulation numerical model includes an impact current waveform, a contact mode between closing resistors, and a temperature characteristic of the closing resistor, which are arranged in sequence.

[0011] Based on the equivalent destruction simulation numerical model of the closing resistor, an equivalent destruction simulation numerical model of the closing resistor is formed by injecting impulse current into the closing resistor, and the limit value of the impulse current that the closing resistor can withstand is calculated. The stress of the closing resistor under the injection current is compared with the standard compressive strength of the closing resistor to obtain the tolerance value of the closing resistor.

[0012] In the closing resistor quality detection modeling method based on the equivalent damage principle, the geometric model includes the outer circle radius, the inner circle radius and the thickness of the closing resistor sheet of the contact.

[0013] In the closing resistor quality detection modeling method based on the equivalent destruction principle, the electrical parameters of the closing resistor include the impulse current waveform, the peak value, peak time and half-peak time of the impulse current and the closing resistor input time.

[0014] In the closing resistor quality detection modeling method based on the equivalent damage principle, the closing resistor model also includes the closing resistor compressive strength.

[0015] In the closing resistor quality detection modeling method based on the equivalent damage principle, in the closing resistor equivalent damage simulation numerical model, the conversion formula for converting electrical energy into thermal energy is: , where Q is the heat energy converted from electrical energy, I(t) is the function of the impact current changing with time, R is the resistance value of the closing resistor, and then the heat energy causes the temperature to rise: , where Δθ is the temperature change of the closing resistor; c is the specific heat capacity of the closing resistor; m is the mass of the closing resistor. The temperature rise causes the closing resistor to expand thermally: , where ΔX is the expansion of the closing resistor; γ is the thermal expansion coefficient of the closing resistor. Finally, the closing resistor generates thermal stress due to thermal expansion: , where F is the thermal stress generated by the closing resistor when heated; E is the Young's modulus of the closing resistor.

[0016] Compared with the prior art, the present invention has the following advantages: the present invention can perform equivalent modeling of the closing resistance of a large tank-type circuit breaker, thereby solving the limitations of establishing a closing resistance model of the tank-type circuit breaker, and can evaluate the tank-type circuit breaker of the power system, thereby ensuring stable and safe operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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.

[0018] In the attached picture:

[0019] Figure 1 It is a schematic diagram of the process of the present invention;

[0020] Figure 2 A schematic diagram of a closing resistor according to an embodiment of the present invention;

[0021] Figure 3 A schematic diagram of a tank circuit breaker of an embodiment of the present invention;

[0022] Figure 4 is a schematic diagram of an impact current according to an embodiment of the present invention;

[0023] Figure 5 It is a temperature variation diagram of an embodiment of the present invention;

[0024] Figure 6 is a graph showing changes in average stress in an embodiment of the present invention;

[0025] Figure 7 Graph showing the relationship between thermal stress and impact current in an embodiment of the present invention.

[0026] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0027] 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.

[0028] 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.

[0029] 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.

[0030] like Figures 1 to 7 As shown in FIG. 1 , the closing resistor quality detection modeling method based on the equivalent damage principle includes the following steps:

[0031] A closing resistor model is established based on the electrical parameters and geometric model of the closing resistor. The electrical parameters include the closing resistor conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity, and the closing resistor conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity are set as the closing resistor model.

[0032] Based on the closing resistor model and the electrical parameters of the closing resistor, an equivalent destruction simulation numerical model of the closing resistor is established. The equivalent destruction simulation numerical model of the closing resistor includes an impulse current waveform, a contact mode between the closing resistors, and a temperature characteristic of the closing resistor, which are arranged in sequence. Furthermore, the contact of the current between the closing resistors is point contact, and the radius is 1 micron.

[0033] Based on the equivalent damage simulation numerical model of the closing resistor, an equivalent damage simulation numerical model of the impact current injection into the closing resistor is formed. Further, the current waveform is injected into the closing resistor by point injection. After a circulation time of 10ms, the temperature change and stress change are obtained, and the limit value of the impact current that the closing resistor can withstand is calculated. The stress of the closing resistor under the injection current is compared with the standard compressive strength of the closing resistor to obtain the tolerance value of the closing resistor.

[0034] In the closing resistor quality detection modeling method based on the equivalent damage principle, the geometric model includes the outer circle radius, the inner circle radius and the thickness of the closing resistor sheet of the contact.

[0035] In the closing resistor quality detection modeling method based on the equivalent destruction principle, the electrical parameters of the closing resistor include the impulse current waveform, the peak value, peak time and half-peak time of the impulse current and the closing resistor input time.

[0036] In the closing resistor quality detection modeling method based on the equivalent damage principle, the closing resistor model also includes the closing resistor compressive strength.

[0037] In the closing resistor quality detection modeling method based on the equivalent damage principle, in the closing resistor equivalent damage simulation numerical model, the conversion formula for converting electrical energy into thermal energy is: , where Q is the heat energy converted from electrical energy, I(t) is the function of the impact current changing with time, R is the resistance value of the closing resistor, and then the heat energy causes the temperature to rise: , where Δθ is the temperature change of the closing resistor; c is the specific heat capacity of the closing resistor; m is the mass of the closing resistor. The temperature rise causes the closing resistor to expand thermally: , where ΔX is the expansion of the closing resistor; γ is the thermal expansion coefficient of the closing resistor. Finally, the closing resistor generates thermal stress due to thermal expansion: , where F is the thermal stress generated by the closing resistor when heated; E is the Young's modulus of the closing resistor.

[0038] In one embodiment, see Figure 1 , methods include,

[0039] Modeling is performed based on the actual geometric parameters of the closing resistor, including the outer circle radius, inner circle radius and thickness of the closing resistor sheet.

[0040] The conductivity, thermal expansion coefficient, Young's modulus, density and specific heat capacity of the closing resistor are set to improve the model accuracy.

[0041] The peak value, peak time and half-peak time of the impact current, as well as the closing resistance input time, are set to accurately establish a model, and the closing resistance model is simulated to realize the equivalent destruction principle of the power system and the closing resistance quality detection equivalent modeling.

[0042] The present invention is further described below with reference to the accompanying drawings and examples. The examples use three impulse currents of different amplitudes, with a flow time of about 10ms. Figure 3As 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.

[0043] 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.

[0044] Depend on Figure 5 It can be seen that, overall, the temperature is in a continuous rising process, 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 622℃. As the impact current increases from 300A to 700A, the temperature of the closing resistor shows a continuous rising trend. From the following formula:

[0045]

[0046]

[0047] From the analysis, it can be seen that as the amplitude of the impact current I continues to increase, the energy generated by the impact current will continue to increase, the current converted into heat will increase, Q will increase, and then the temperature change will increase. The temperature change curve conforms to the formula derivation.

[0048] Depend on Figure 6 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. There is a stage where the change becomes slow, but this stage is very short and has the characteristic of lagging behind the impact current. According to the formula

[0049]

[0050]

[0051] Analysis shows that temperature change is proportional to stress change, and the proportionality coefficient is the product of Young's modulus and thermal expansion coefficient. As the impulse current amplitude increases, the temperature difference increases, and the increase in temperature difference leads to an increase in thermal stress. The curve changes are all corresponding to the formula derivation.

[0052] The above simulation process is to find the limit value of the impact current that the closing resistor can withstand. Figure 7 Analysis shows that, under the condition that the size and number of contact points are consistent, and the parameters of the closing resistor are consistent, only the amplitude of the impact current is changed to find the impact current limit that the closing resistor can withstand. Figure 7It can be seen that when the impulse current is 709A, the thermal stress value at the injection point of the closing resistor has reached the standard compressive strength of the closing resistor, thus finding the impulse current withstand limit value of the closing resistor.

[0053] In the above analysis results, the closing resistor quality detection modeling based on the equivalent destruction principle includes various parameter indicators of the closing resistor, the impulse current waveform, and when the thermal stress of the closing resistor reaches the standard compressive strength 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 closing resistor quality detection modeling method based on the equivalent damage principle, characterized in that: The steps include: A closing resistor model is established based on a first electrical parameter and a geometric model of the closing resistor, wherein the first electrical parameter includes a closing resistor conductivity, a thermal expansion coefficient, a Young's modulus, a density, and a specific heat capacity, and the closing resistor conductivity, the thermal expansion coefficient, the Young's modulus, the density, and the specific heat capacity are set as the closing resistor model; A closing resistor equivalent damage simulation numerical model is established based on the closing resistor model and the second electrical parameter of the closing resistor, wherein the closing resistor equivalent damage simulation numerical model includes an impulse current waveform, a contact mode between closing resistors, and a temperature characteristic of the closing resistor, which are arranged in sequence, wherein the second electrical parameter of the closing resistor includes an impulse current waveform, an impulse current peak value, a peak time, and a half-peak time, and a closing resistor input time; Based on the equivalent destruction simulation numerical model of the closing resistor, an equivalent destruction simulation numerical model of the closing resistor is formed by injecting impulse current into the closing resistor, and the limit value of the impulse current that the closing resistor can withstand is calculated. The stress of the closing resistor under the injection current is compared with the standard compressive strength of the closing resistor to obtain the tolerance value of the closing resistor.

2. A closing resistance quality detection modeling method based on equivalent damage principle according to claim 1, characterized in that: The geometric model includes the outer radius, inner radius and thickness of the closing resistor of the contact.

3. The closing resistance quality detection modeling method based on the equivalent damage principle according to claim 1 is characterized in that: The closing resistor model also includes the closing resistor compressive strength.

4. The closing resistance quality detection modeling method based on the equivalent damage principle according to claim 1 is characterized in that: In the closing resistance equivalent damage simulation numerical model, the conversion formula of electrical energy into thermal energy is: , where Q is the heat energy converted from electrical energy, I(t) is the function of the impact current changing with time, R is the resistance value of the closing resistor, and then the heat energy causes the temperature to rise: , where Δθ is the temperature change of the closing resistor; c is the specific heat capacity of the closing resistor; m is the mass of the closing resistor. The temperature rise causes the closing resistor to expand thermally: , where ΔX is the expansion of the closing resistor; γ is the thermal expansion coefficient of the closing resistor. Finally, the closing resistor generates thermal stress due to thermal expansion: , where F is the thermal stress generated by the closing resistor when heated; E is the Young's modulus of the closing resistor.

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