A porcelain insulator early fault detection method and system

Abstract

The present invention discloses a porcelain insulator early fault detection method and system, which belongs to the technical field of power system equipment monitoring, including: simulating the electric field change when moisture enters the porcelain insulator crack, establishing an air-water two-phase flow simulation model; analyzing the electrical characteristics at the start of discharge according to the electric field distribution data obtained from the air-water two-phase flow simulation model; analyzing the relationship between arc voltage and current during arc burning and its influence on arc conductivity and arc resistance according to the initial arc conditions obtained from the electric field simulation and discharge start analysis; analyzing the characteristics of arc energy dissipation and air after discharge self-clearing according to the arc energy dissipation data calculated during the arc process; and identifying potential faults according to the analysis results. The present invention can improve the accuracy and early warning capability of porcelain insulator fault detection, thereby significantly reducing the fault risk and maintenance cost in the operation of the power system.

Description

Technical Field

[0001] The invention relates to the technical field of power system equipment monitoring, and in particular to a porcelain insulator early fault detection method and system. Background Art

[0002] Porcelain insulators have high mechanical strength, chemical stability, excellent insulation performance and strong corrosion resistance, and have been widely used in distribution networks. When firing porcelain insulators, the quartz in the material will transform from α-quartz to β-quartz during the cooling process, and the volume will decrease by 2%. This will cause strain and form many microcracks in the porcelain body. These microcracks will become larger over time under the action of electrical and mechanical stress, and eventually lead to complete radial cracks. In 10kV distribution networks, commonly used porcelain insulators include pin insulators, suspension insulators, post insulators, cross arm insulators, etc. Among them, pin insulators lack iron caps, and the porcelain between electrodes (wires and needles) is relatively thin. Therefore, rainwater can easily flow into the cracks on rainy days, reducing the insulation strength, resulting in drainage in the cracks. The narrow internal space of the crack allows the discharge to extinguish itself through the evaporation of water caused by heat, showing a self-clearing characteristic. This type of fault is referred to as porcelain insulator early failure (PIIF) in this invention.

[0003] In the actual operation of the distribution network, this situation is usually regarded as a disturbance. In terms of intensity and duration, it is not enough to cause a tripping operation. Since the discharge occurs inside the crack and has self-clearing characteristics, it is still challenging to determine whether the discharge is caused by the porcelain insulator even if the maintenance personnel take the initiative to go to the fault site for inspection. As the discharge events accumulate, PIIF will eventually evolve into a permanent ground fault and cause insulator fragmentation and line breakage. The cause of the fault can only be confirmed at this stage.

[0004] After a permanent fault occurs, the replacement cost of a pin insulator is low. However, permanent faults may lead to various accidents such as line breakage, power outages, fires, and electric shocks. The losses caused by these accidents may be thousands of times the cost of the pin insulator. In addition, its low cost also makes the commonly used monitoring methods in transmission lines (such as ultrasonic probes, non-contact microphones, and infrared cameras) very cost-effective. Therefore, if a reliable and low-cost PIIF detection and identification method can be found based on the existing distribution network operation and maintenance methods, hidden dangers can be discovered before permanent faults occur. This advances the timeline of distribution line fault handling from "after the tripping operation" to "before the tripping operation." In addition, identifying specific types of early-fault equipment can provide maintenance personnel with valuable insights for investigating hidden dangers, narrowing the scope of investigation and thus improving work efficiency.

[0005] At present, a large number of fault monitoring devices have been installed in the distribution network to monitor electrical parameters such as current, voltage and power consumption. Therefore, the detection and identification based on the electrical characteristics of PIIF is the most economical and engineering-valuable method. In early studies, many scholars used algebraic arc models, such as the Cassie model and the Mayr model, to equivalent the arc process of such arc grounding faults. In addition, some scholars have established the functional relationship between arc conductivity and parameters such as time constant, dissipated power, arc column field strength, arc length and current to be closer to the actual arc process. Improved models such as the Schwarz arc model, the KEMA arc model and the Cybernic arc model have been proposed. On this basis, simulation software such as PSCAD can be used to simulate the dynamic process of the distribution system after an arc grounding fault. In addition, many methods have been proposed to detect arc grounding faults based on the nonlinear characteristics of the arc. Steady-state detection methods use parameters such as harmonics, phase and grounding resistance. Transient detection methods rely on projection coefficients, transient energy and traveling waves. However, the above arc models are established after simplification and equivalence, which cannot reflect the actual situation of the fault point, nor can they establish the corresponding relationship between electrical characteristics and faulty equipment types. Therefore, the existing methods can only detect whether a fault occurs, but cannot determine the specific cause of the fault.

[0006] With the emergence of artificial intelligence technology, some scholars have applied artificial intelligence methods such as artificial neural networks (ANN), deep convolutional neural networks (Deep CNN) and genetic algorithms to the field of distribution network fault type identification. By using actual fault record data, they have successfully achieved the identification of various types of faults, including foreign object faults, conflicts between trees and transmission lines, lightning strikes, etc. These methods are heavily dependent on the quantity and quality of sample data sets. Only a small part of the fault data obtained from the actual distribution network has clear and accurate fault type labels, which leads to limited data sets for certain fault types. This limitation makes it difficult to meet the requirements of artificial intelligence methods for sufficient sample data sets. In addition, artificial intelligence methods also face challenges such as unclear physical meaning and poor interpretability.

[0007] In summary, the shortcomings of existing research are mainly reflected in the failure to establish the correlation between the electrical characteristics of the fault and the type of faulty equipment. Therefore, the present invention studies the generation mechanism, evolution process and electrical characteristics of PIIF. First, an air-water two-phase flow simulation model was established to study the changes in the electric field during the entry of water into the crack. Then, the electrical characteristics of PIIF were analyzed from three aspects: starting time, power-resistance change trend and fault duration. Finally, the experiments conducted in the 10kV distribution network real-type test platform verified and supplemented these characteristics. This study established the connection between the development process of PIIF and its electrical characteristics, laying a theoretical foundation for proposing a detection and identification method for PIIF. Summary of the invention

[0008] In view of the above-mentioned problems, the present invention is proposed.

[0009] Therefore, the technical problem solved by the present invention is: how to solve the problem of early failure of porcelain insulators caused by internal cracks in non-effective grounding systems, and through high-precision simulation and real-time monitoring technology, accurate monitoring of electric field changes, arc behavior and related electrical characteristics caused by moisture inside the cracks can be achieved, so as to identify and warn of potential failures in advance.

[0010] To solve the above technical problems, the present invention provides the following technical solutions: A porcelain insulator early fault detection method, comprising: simulating the electric field change when moisture enters the porcelain insulator crack, and establishing an air-water two-phase flow simulation model;

[0011] Analyzing the electrical characteristics at the start of discharge based on the electric field distribution data obtained by the two-phase flow simulation model;

[0012] According to the initial arc conditions obtained from electric field simulation and discharge initiation analysis, the relationship between arc voltage and current during arc burning and its influence on arc conductance and arc resistance are analyzed;

[0013] According to the arc energy dissipation data calculated during the arc process, the characteristics of arc energy dissipation and air after discharge self-clearing are analyzed;

[0014] Based on the analysis results, potential faults are identified.

[0015] As a preferred solution of the porcelain insulator early fault detection method described in the present invention, the establishment of an air-water two-phase flow simulation model includes simulating the water-gas two-phase flow inside the crack through the Cahn-Hilliard equation and the Navier-Stokes equation, and calculating the electric field distribution at different time points in the air-water two-phase flow simulation model.

[0016] As a preferred solution of the porcelain insulator early fault detection method of the present invention, the Cahn-Hilliard equation includes: by introducing the phase field variable To identify different phase regions and transition regions between different phases, the formula is:

[0017] ;

[0018] in, Indicates time The partial derivative of rate of change over time; represents the convection term; Indicates the velocity of the fluid in m / s; express The gradient of rate of change; represents the diffusion term, Represents divergence, used to describe The degree of divergence in space; coefficient It means controlling the diffusion rate; It represents the mobility in units of ; It represents the mixed energy density in N; Represents the interface thickness parameter, in m; represents the phase field auxiliary variable;

[0019] At the gas-liquid interface, the density varies smoothly across the two phase interface. and viscosity Define it to mean:

[0020] ;

[0021] in, Represents the density of water in units of ; Indicates the air density in units of ; Indicates the viscosity of water, in Pa·s; Indicates air viscosity, unit is Pa·s; represents the density that varies smoothly across the interface between two phases, in units of ; It represents the viscosity that varies smoothly across the interface between two phases, and its unit is Pa·s;

[0022] The Navier-Stokes equation is used to describe the mass and momentum transfer characteristics of incompressible fluids. Considering the influence of interfacial tension, the two-phase flow Navier-Stokes equation and continuity equation are expressed as:

[0023] ;

[0024] in, Represents the fluid density in units of ; It represents dynamic viscosity, the unit is Pa·s; represents the velocity gradient, Transpose of the tensor representing the velocity gradient; Indicates the flow inlet pressure, in Pa; represents a unit vector; It represents the interfacial tension of two-phase fluid, in N / m; Represents the gravity vector in units of ;formula Indicates the incompressibility of the fluid;

[0025] Convection and diffusion in the interface region will cause changes in the interface free energy, which will increase the interfacial tension. Defined as:

[0026] ;

[0027] The electrostatic field theory is used to analyze the electric field inside the insulator crack. From the potential we get:

[0028] ;

[0029] in, Represents electric potential, unit is V; Represents the dielectric constant of free space, in F / m; represents the relative dielectric constant, represents the space charge density in units of ; Represents the electric field, the unit is V / m; Represents interfacial tension, unit is N.

[0030] As a preferred solution of the porcelain insulator early fault detection method of the present invention, wherein: the analysis of the electrical characteristics at the start of discharge includes establishing a proportional porcelain insulator model, the geometric shape, position, width, depth of the crack and the electrical characteristics of the insulator, to ensure that the model reflects the physical and electrical characteristics of the actual cracked insulator;

[0031] The electric potential condition of simulating AC voltage is set in the proportional porcelain insulator model, the electric potential V of the top plane is defined as 8165×sin(100πt), and the bottom plane is grounded to simulate the electric field change under normal working voltage;

[0032] The analysis of the electrical characteristics at the start of discharge includes setting the breakdown threshold of the dielectric , and compare the maximum electric field intensity in the crack area Whether it exceeds the threshold , at any time, if Exceed , it is predicted that the discharge will occur before the voltage reaches its peak;

[0033] like Cannot exceed , then the electric field strength will decrease as the voltage decreases, and discharge will not occur.

[0034] As a preferred solution of the porcelain insulator early fault detection method of the present invention, the analysis of the relationship between arc voltage and current during arc burning and its influence on arc conductivity and arc resistance includes simulating the electrical behavior of the arc and using a thermal balance equation to describe the dynamic change of arc energy:

[0035] ;

[0036] in, Indicates arc energy, unit is J; Indicates arc voltage, unit is V; Indicates arc current, unit is A; Indicates the power dissipation in VA;

[0037] Let g represent the arc conductance in S, then the equation can be transformed into:

[0038] ;

[0039] Considering how the heat generated by the arc affects the moisture in the crack through convection and conduction, calculate the effect of moisture evaporation caused by the arc heat on the resistance in the crack:

[0040] ;

[0041] in, Represents the resistivity of water, in Ω·m; Indicates the length of the water column in m; Represents the cross-sectional area of ​​the water column in units of .

[0042] As a preferred solution of the porcelain insulator early fault detection method of the present invention, the characteristics of the air after the arc energy dissipation and discharge self-clearing include that the water flowing into the crack will evaporate under the influence of the thermal effect of the current, and the energy required for the evaporation process The calculation method is:

[0043] ;

[0044] in, Represents the density of water in units of ; Represents the volume of water in ; The specific heat capacity of water is expressed in ; Indicates the boiling point of water at standard atmospheric pressure, in K; represents the initial temperature of water, in K; It represents the latent heat of evaporation of water in kJ / kg;

[0045] The water at the air-water interface will gain energy from the arc conduction, causing it to heat up and turn into steam, and discharge the unevaporated water from the cracks, so that the arc will not reignite after the current passes through zero. After the arc is extinguished, the subsequent discharge needs to wait for the water to re-enter the cracks.

[0046] As a preferred solution of the porcelain insulator early fault detection method of the present invention, the potential fault identification includes: when an arc is detected in a crack of the porcelain insulator and the duration is less than a minimum time threshold, When , it is judged that the arc is triggered and extinguished due to the high local electric field intensity;

[0047] If air is left after the arc burns and the arc can be reignited within a short time after discharge, it indicates that there is a continuous high electric field strength and unstable dielectric conditions inside the crack;

[0048] When the water in the crack evaporates due to the thermal effect of the current and the calculated water evaporation energy exceeds the threshold When , it is judged that the moisture in the crack is reduced, and according to the inverse proportional relationship between the dielectric resistance and the moisture storage, it is judged that the dielectric resistance in the crack is increased.

[0049] A porcelain insulator early fault detection system, comprising:

[0050] Simulation module: simulates the change of electric field when water enters the crack of porcelain insulator, establishes air-water two-phase flow simulation model, and analyzes the electrical characteristics at the beginning of discharge;

[0051] Arc characteristic analysis module: analyzes the relationship between arc voltage and current during arc burning and its influence on arc conductivity and arc resistance;

[0052] Discharge duration analysis module: analyzes arc energy dissipation during discharge and the influence of air after discharge self-clearance;

[0053] Identification module: Identify potential faults based on the analysis results.

[0054] A computer device comprises: a memory and a processor; the memory stores a computer program, wherein: the processor implements the steps of any one of the methods of the present invention when executing the computer program.

[0055] A computer-readable storage medium stores a computer program, wherein: when the computer program is executed by a processor, the steps of any one of the methods of the present invention are implemented.

[0056] Beneficial effects of the invention: Through continuous monitoring and precise analysis of porcelain insulators, the invention can timely identify and deal with problems that may lead to serious power failures. Through detailed analysis of crack expansion and discharge behavior, more targeted maintenance measures can be implemented, thereby extending the service life of porcelain insulators and related power equipment. The system's predictive maintenance model reduces unnecessary comprehensive inspection and maintenance costs, allowing resources to be more concentrated on key parts that may fail. This resource optimization not only reduces direct maintenance costs, but also helps reduce downtime costs caused by sudden failures. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0058] Figure 1 An overall flow chart of a porcelain insulator early fault detection method provided by the first embodiment of the present invention;

[0059] Figure 2 A schematic diagram of water ingress and discharge process of a crack of a porcelain insulator early fault detection method provided by the first embodiment of the present invention;

[0060] Figure 3 A simulation schematic diagram of a porcelain insulator early fault detection method provided by the first embodiment of the present invention;

[0061] Figure 4 A simulation result diagram of a porcelain insulator early fault detection method provided by the first embodiment of the present invention;

[0062] Figure 5 A schematic diagram of voltage-electric field variation of a porcelain insulator early fault detection method provided by the first embodiment of the present invention;

[0063] Figure 6 A schematic diagram of Parc-Rarc changes of a porcelain insulator early fault detection method provided by the first embodiment of the present invention;

[0064] Figure 7 A schematic diagram of a test field circuit of a porcelain insulator early fault detection method provided by a second embodiment of the present invention;

[0065] Figure 8 A schematic diagram of an artificially manufactured crack pin insulator for a porcelain insulator early fault detection method provided by a second embodiment of the present invention;

[0066] Fig. 9 A schematic diagram of grounding equivalent resistance of a porcelain insulator early fault detection method provided by a second embodiment of the present invention;

[0067] Fig.10 FIG1 is a crack wall morphology of a porcelain insulator early fault detection method provided by the second embodiment of the present invention;

[0068] Fig.11 A discharge waveform diagram of insulator 1 of a porcelain insulator early fault detection method provided by the second embodiment of the present invention;

[0069] Fig.12 A power-resistance variation curve diagram of a porcelain insulator early fault detection method provided by the second embodiment of the present invention;

[0070] Fig.13 FIG2 is a crack wall morphology of a porcelain insulator early fault detection method provided by the second embodiment of the present invention;

[0071] Fig.14 A discharge waveform diagram of insulator 2 of a porcelain insulator early fault detection method provided by the second embodiment of the present invention;

[0072] Fig.15 A power-resistance variation curve 2 of a porcelain insulator early fault detection method provided by the second embodiment of the present invention;

[0073] Fig.16 FIG3 is a crack wall morphology of a porcelain insulator early fault detection method provided by the second embodiment of the present invention;

[0074] Fig.17 Microscope channel images of a porcelain insulator early fault detection method provided by the second embodiment of the present invention, wherein Figure (a) is a SEM image of the discharge channel; Figure (b) is a SEM image of the non-discharge area; Figure (c) is an X-ray diffraction image of the two areas;

[0075] Fig.18 This is a discharge waveform diagram of insulator 3 of a porcelain insulator early fault detection method provided by the second embodiment of the present invention. DETAILED DESCRIPTION

[0076] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0077] Example 1

[0078] Reference Figure 1 to Figure 6 , as an embodiment of the present invention, provides a porcelain insulator early fault detection method, comprising:

[0079] S1: Simulate the change in the electric field when moisture enters the cracks of the porcelain insulator, establish an air-water two-phase flow simulation model, and analyze the electrical characteristics at the start of discharge based on the electric field distribution data obtained by the two-phase flow simulation model.

[0080] Under the influence of adverse conditions such as overvoltage, mechanical stress and surface contamination, cracks may appear in pin-type porcelain insulators. These cracks are highly concealed and difficult to observe with the naked eye. They are usually between 0.1 and 0.2 mm. Under dry weather conditions, cracked insulators can still maintain sufficient insulation capacity, and the normal power frequency voltage of the system will not cause discharge. However, under rainy conditions, rainwater will flow into the cracks from top to bottom, gradually shortening the air gap. At a certain moment, the electric field strength reaches the breakdown threshold, triggering discharge. The water that enters the crack evaporates due to the thermal effect of the fault current and is discharged from the crack, causing the arc to prolong and extinguish when the current passes through zero. This process is as follows Figure 2 shown.

[0081] The starting moment of arc discharge depends on the effect of moisture flowing into the crack on the electric field inside the crack. In order to study the process of moisture intrusion into the crack and the distribution of the electric field inside the crack during this process, a proportional model of a pin-type porcelain insulator was established. Considering that the crack wall is rough and irregular, the spatial frequency content is used as a representation of the roughness of the crack wall, thereby generating a random surface as the crack wall, and the width of the crack is set to 0.2mm. In order to reduce the amount of simulation calculations, the area where the distance between the porcelain insulator wire slot and the iron foot is the shortest is taken for simulation. The schematic diagram of the simulation model is shown in the figure. Figure 3 shown.

[0082] In the simulation, the phase field method was combined with the Navier-Stokes equations to construct a simulation model of water-gas two-phase displacement in the narrow slit interface.

[0083] The phase field method introduces the phase field variable The Cahn-Hilliard equation is a convection-diffusion equation used to control the evolution of interface profiles. This equation states that the phase field variables The change over time is balanced by the change due to convection and diffusion:

[0084] ;

[0085] in, Indicates time The partial derivative of rate of change over time; represents the convection term; Indicates the velocity of the fluid in m / s; express The gradient of rate of change; represents the diffusion term, Represents divergence, used to describe The degree of divergence in space; coefficient It means controlling the diffusion rate; It represents the mobility in units of ; It represents the mixed energy density in N; Represents the interface thickness parameter, in m; represents the phase field auxiliary variable.

[0086] At the gas-liquid interface, the density that varies smoothly across the two-phase interface is and viscosity Define it to mean:

[0087] ;

[0088] in, Represents the density of water in units of ; Indicates the air density in units of ; Indicates the viscosity of water, in Pa·s; Indicates air viscosity, unit is Pa·s; represents the density that varies smoothly across the interface between two phases, in units of ; It represents the viscosity that varies smoothly across the interface between two phases and is expressed in Pa·s.

[0089] The Navier-Stokes equations are used to describe the mass and momentum transfer characteristics of incompressible fluids. Taking into account the influence of interfacial tension, the two-phase flow Navier-Stokes equations and continuity equations can be expressed as:

[0090] ;

[0091] in, Represents the fluid density in units of ; It represents dynamic viscosity, the unit is Pa·s; represents the velocity gradient, Transpose of the tensor representing the velocity gradient; Indicates the flow inlet pressure, in Pa; represents a unit vector; It represents the interfacial tension of two-phase fluid, in N / m; Represents the gravity vector in units of ;formula Represents the incompressibility of the fluid.

[0092] In the phase field method, convection and diffusion in the interface region will cause changes in the interface free energy, which can be used to calculate the interfacial tension. Defined as:

[0093] ;

[0094] At the same time, the size of the insulator is much smaller than the wavelength of the 50 Hz power frequency electromagnetic wave, and the electrostatic field theory can be used to analyze the electric field inside the insulator crack. From the potential we get:

[0095] ;

[0096] in, Represents electric potential, unit is V; Represents the dielectric constant of free space, in F / m; represents the relative dielectric constant, represents the space charge density in units of ; Represents the electric field, the unit is V / m; Represents interfacial tension, unit: N.

[0097] In the simulation, the bottom plane of the model is set to ground and the potential of the top plane is set to 8165×sin(100πt). The results are as follows: Figure 4 As shown in the figure. As time goes by, water gradually flows into the crack from top to bottom under the action of gravity and surface tension. Due to the different roughness of different areas on the crack surface, the lengths of different water flow paths are also different. This causes the water-air interface to not move horizontally downward, as shown at 25ms, 45ms, etc. But overall, the water-air interface will move steadily downward, and the length of the air gap will gradually decrease. In addition, under the influence of the power frequency voltage, the distribution of the electric field in the crack will also change over time.

[0098] exist Figure 4 The high electric field intensity area is mainly located near the water-air interface. Starting from 0ms, the maximum electric field intensity at each moment when water flows into the crack is recorded at intervals of 0.1ms. The curve is as follows: Figure 5 shown.

[0099] It should be noted that under the action of power frequency voltage, if the positions of the two electrodes and the properties of the dielectric between them remain unchanged, the maximum electric field strength between the electrodes will change with the voltage in each half cycle, showing a trend of first increasing and then decreasing. Therefore, if the maximum electric field strength exceeds the dielectric breakdown strength, the discharge will occur before the voltage reaches the peak value. Otherwise, the electric field strength will decrease as the voltage decreases, and the discharge will not occur.

[0100] However, for cracked porcelain insulators operating on rainy days, the length of the air gap will be shortened by water flowing into the cracks. This means that the properties of the dielectric between the two electrodes are also changing over time, and the peak value of the maximum electric field strength may occur during the rising or falling phase of the voltage within half a power frequency cycle, such as Figure 5 Therefore, as water flows into the cracks, discharge will occur not only during the voltage rising phase, but also during the voltage falling phase after the voltage reaches the peak.

[0101] S2: Based on the initial arc conditions obtained from the electric field simulation and discharge initiation analysis, the relationship between arc voltage and current during the arc burning process and its influence on arc conductance and arc resistance are analyzed.

[0102] During the arc burning process, the arc voltage and current provide energy for the arc. Part of the energy is dissipated into the surrounding environment through convection, conduction and radiation, while the remaining energy is used to maintain the plasma state of the arc. This process can be expressed by the following heat balance equation:

[0103] ;

[0104] in, Indicates arc energy, unit is J; Indicates arc voltage, unit is V; Indicates arc current, unit is A; Let g represent the arc conductance in S, then the equation can be transformed into:

[0105] ;

[0106] Considering how the heat generated by the arc affects the moisture in the crack through convection and conduction, calculate the effect of moisture evaporation caused by the arc heat on the resistance in the crack:

[0107] ;

[0108] in, Represents the resistivity of water, in Ω·m; Indicates the length of the water column in m; Represents the cross-sectional area of ​​the water column in units of .

[0109] If the order , we get the classic black box arc model:

[0110] ;

[0111] Time constant τ and dissipated power It can be expressed in different forms according to different assumptions. Such as Mayr, Schwarz, Cybernetic, etc. These models have achieved good results in arc simulation. Taking the Cybernic arc model as an example, and The schematic diagram of the changing trend is as follows Figure 6 shown.

[0112] As the power supplied to the arc by the Parc decreases, the energy required to maintain the arc burning This results in a decrease in arc temperature and diameter, resulting in a decrease in arc resistance Increase rapidly. When it decreases to its minimum value, It will reach its maximum value at a faster speed. This is the main reason for the "zero shoulder" in the arc current waveform.

[0113] After the air gap in the crack breaks down, the current will flow through the water area and the arc area. Since the arc length is less than 2cm, the resistance is low during the intense burning process. The conductivity of rainwater ranges from tens of Ω·m to hundreds of Ω·m. Combined with the calculation formula of resistance , it can be inferred that when the air gap in the crack is just broken through, Much greater than .

[0114] According to the above analysis, when the power input to the crack decreases, However, the thermal effect of the current causes rainwater in the cracks to heat up and evaporate, shortening the length of the water area. At the same time, due to the limitation of the crack wall, the cross-sectional area of ​​the water area remain relatively constant. This will result in Therefore, before the power is reduced to a certain level, the resistance change between the wire and the iron foot is mainly caused by The decrease in Will follow 's decrease but first decreases and then increases.

[0115] S3: Based on the arc energy dissipation data calculated during the arc process, the characteristics of arc energy dissipation and high-temperature air after discharge self-clearing are analyzed.

[0116] For an arc under open space conditions, the energy dissipated by convection and radiation will cause thermal ionization of the air around the arc. The ionized air will be converted into part of the arc plasma, which is visually manifested as an increase in the arc column diameter. This phenomenon makes it easy for the arc to reignite after the current passes zero due to the presence of residual high-temperature air. However, the size of the air region within the crack is limited, and most of the energy dissipated by the arc is absorbed by the crack surface. Compared with the arc in the open space, the arc in the crack has less residual high-temperature air after the current passes zero, making it difficult to reignite.

[0117] Furthermore, as mentioned above, the water flowing into the crack will evaporate under the influence of the thermal effect of the current. The energy required for this evaporation process It can be calculated using the following equation:

[0118] ;

[0119] in, represents the density of water, represents the volume of water, is the specific heat capacity of water, The boiling point of water at standard atmospheric pressure. represents the initial temperature of water, It represents the latent heat of vaporization of water.

[0120] The width of the insulator crack is about 0.1~0.2mm. Combined with the actual size of the common P-6 and P-10 porcelain insulators, the volume of water flowing into the insulator crack is about 20~40 . It only needs to absorb about 51.7~103.4J of energy to completely evaporate. In addition, the water near the air-water interface will gain additional energy from the arc conduction, causing it to heat up and quickly turn into steam. This process will expel the unevaporated water from the crack, making it difficult to reignite the arc after the current passes through zero. After the arc is extinguished, the subsequent discharge needs to wait for the water to re-enter the crack, thus repeating the process. Figure 2 The process shown.

[0121] S4: Based on the analysis results, identify potential faults.

[0122] When the electric field strength inside the crack exceeds the breakdown threshold When the high electric field strength can cause the ionization of the air, the discharge process has begun; when the arc is detected in the crack of the porcelain insulator and the duration is lower than the minimum time threshold When the arc is triggered and extinguished due to the high local electric field strength, it is judged that the arc is triggered and extinguished due to the high local electric field strength; if high-temperature air is left after the arc burns, and the arc can be reignited in a short time after the arc discharge, it indicates that there is a continuous high electric field strength and unstable dielectric conditions inside the crack; when the water in the crack evaporates due to the thermal effect of the current, and the calculated water evaporation energy exceeds the threshold When the water content in the crack decreases, the dielectric resistance in the crack will increase.

[0123] Furthermore, the start of discharge may occur in the voltage rising stage or in the voltage falling stage, and there is a "post-peak breakdown" phenomenon; the change process of inter-electrode resistance lags behind the change process of power, and only begins to increase after the power decreases to a certain level; when the starting moment of the fault is in the voltage rising stage, the discharge duration is less than 10ms, and when the starting moment of the fault is in the voltage falling stage, the discharge duration will be less than 5ms; as the number of faults accumulates, the interval between two discharges will gradually shorten.

[0124] The above embodiments also include a porcelain insulator early fault detection system, specifically:

[0125] Simulation module: simulates the change of electric field when moisture enters the crack of porcelain insulator, establishes air-water two-phase flow simulation model, and analyzes the electrical characteristics at the beginning of discharge.

[0126] Arc characteristic analysis module: Analyze the relationship between arc voltage and current during arc burning and its influence on arc conductivity and arc resistance.

[0127] Discharge duration analysis module: Analyzes the arc energy dissipation during the discharge process and the impact of high-temperature air after discharge self-clearing.

[0128] Identification module: Identify potential faults based on the analysis results.

[0129] The computer device may be a server. The computer device includes a processor, a memory, an input / output interface (I / O for short) and a communication interface. The processor, the memory and the input / output interface are connected via a system bus, and the communication interface is connected to the system bus via the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store data cluster data of the power monitoring system. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal via a network connection. When the computer program is executed by the processor, a method for detecting early faults of porcelain insulators is implemented.

[0130] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but are not limited to this.

[0131] Example 2

[0132] Reference Figure 7 to Figure 14 , as another embodiment of the present invention, provides a porcelain insulator early fault detection method, comprising:

[0133] In order to verify the unique characteristics of porcelain insulator early failure proposed in the above analysis process, a porcelain insulator early failure simulation test was carried out in a 10kV distribution network real test field.

[0134] Distribution feeders of different lengths, types, and numbers will generate different capacitive currents in the distribution system. Due to the limited area of ​​the test site, it is impractical to build real distribution feeders of different lengths. Therefore, we constructed six sets of lumped parameter line modules using resistors, inductors, and capacitors as the equivalent of real distribution feeders. Their parameters are shown in Table 1. Combining these six sets of lumped parameter line modules with the 400m real overhead line erected at the test site, the system can have distribution feeders of different lengths, types, and numbers.

[0135] In the test of the present invention, referring to Table 1, modules 1, 2 and 6 were used. Figure 7 The wiring of the platform and the method of simulating PIIF are described. and Used to change two neutral point grounding methods. and Used to connect different feeders to the system. and Closed and When disconnected, the system operates in the neutral ungrounded mode and the capacitive current is approximately 2.1A. , , and Closed When disconnected, the system is set as a resonant grounding system, and the capacitive current is about 17.8 A. The arc suppression coil works in overcompensation mode, so that the maximum residual current at the grounding point is 2.7 A.

[0136] The PIIF simulation module mainly consists of six parts: aluminum conductor, support insulator, crack insulator, sprinkler, data recording system and equivalent resistance of concrete pole. .

[0137] Table 1 Phase parameters of lumped parameter line module

[0138]

[0139] The insulators used in the test are P-6T and P-10T porcelain insulators commonly used in 10kV distribution networks. A chisel is used to hit the conductor groove of the insulator, forcing the insulator to split in half at this position. Figure 8 As shown, the crack width is 0.1~0.2mm.

[0140] Compared with the split insulators in actual distribution networks, artificially manufactured split insulators have two main differences:

[0141] Crack location: Cracks may appear in any radial direction of the actual porcelain insulator. However, since the discharge is concentrated in the area between the bottom of the wire groove and the iron foot, the location of the crack has little effect on the test results.

[0142] Porcelain body damage degree: During the manufacturing process of artificial crack insulators, the porcelain body at the bottom of the conductor slot will inevitably be damaged to a certain extent. However, compared with the overall thickness of the porcelain body, the thickness of the damaged part is less than 5%.

[0143] In summary, the artificial crack insulators used in the experiment can be regarded as equivalent to the crack insulators in the actual distribution network.

[0144] The amount of rainfall per unit time is used to assess rainfall intensity, such as light rain (<2.5 mm / h · ), moderate rain (2.6~7.5 mm / h · ) and heavy rain (7.6~50 mm / h · ). In the test, a sprinkler device was used to simulate rainfall, which mainly includes three parts: a water pump, a water pipe and a sprinkler head. The sprinkler head is located about 1 meter above the crack insulator, with a maximum allowable flow rate of 8 liters per hour, which can affect an area of ​​about 0.5~0.8 square meters. The rainfall intensity simulated by the sprinkler device is about medium to heavy rain. In fact, the surface of the porcelain insulator is smooth, and excess rainwater will not accumulate on the surface of the insulator, which has little effect on the process of water entering the crack. Therefore, the rainfall intensity has little effect on the development of PIIF. The sprinkler device only needs to provide enough water to trigger the discharge.

[0145] The data logging system is used to record the voltage and current waveforms of the PIIF. The voltage between the aluminum conductor and the ground in the fault simulation module is measured using a voltage divider (ratio 1000 / 5, accuracy ±1.0%). The iron leg of the crack insulator is connected to the ground through a ground wire. The ground wire is passed through a current transformer (ratio 30 / 5, accuracy ±0.5%) to measure the ground current. The secondary side of the voltage divider and the current transformer is connected to a waveform monitoring recorder, which records data at a sampling rate of 100kHz.

[0146] In actual distribution networks, the iron crossarms of most reinforced concrete towers are not effectively grounded. When PIIF occurs, the current path is as follows: Fig. 9 As shown by the blue line in the figure, that is, conductor → crack insulator → iron cross arm → concrete → steel bar → ground. Therefore, the transition resistance consists of three parts: the resistance of the crack insulator , the resistance of concrete tower and the grounding resistance of the concrete tower .

[0147] Grounding resistance of concrete tower Depends on the type of grounding device and the resistivity of the soil. According to the design specifications of 10 kV distribution networks, the grounding resistance of concrete towers should generally not exceed 30 Ω. Ru mainly comes from the concrete between the iron crossarm and the steel bars. Under dry conditions, the resistivity of concrete ranges from 3500 to 8000 Ω·m, and even under wet conditions, it can still reach 500 to 2500 Ω·m. This makes Ru reach the order of 102 ~103 Ω. Therefore, in the test, a 500 Ω resistor is connected at the fault point for equivalent + ,Right now Figure 7 shown .

[0148] Take the fault simulation test under the neutral point ungrounded system as an example. and Closed, the test steps are as follows:

[0149] Step 1: Closure , make the potential of the aluminum stranded wire in the fault simulation module equal to the fault phase, observe the fault recording device, and ensure that no discharge occurs within 1 minute before proceeding to step 2.

[0150] Step 2: Start the fault recording device to record the voltage of the aluminum stranded wire and the grounding current passing through the fault branch, and at the same time start the water pump to spray water mist onto the surface of the insulator at a uniform speed.

[0151] Step 3: After intermittent discharge occurs several times or permanent breakdown occurs, disconnect .

[0152] Step 4: Remove the cracked insulator, replace it with a new one, and repeat steps 1 to 3.

[0153] In two different non-effectively grounded systems, tests were conducted using P-6T and P-10T insulators. Three representative test groups were selected to present and analyze the results, as shown below:

[0154] In this test, the test was automatically stopped after 26 self-clearing discharges. After the test, the morphology of the crack wall was as follows: Fig.10 As shown in the figure, the yellow area is the area not affected by the early fault, the red area is the area affected by the early fault, and the red arrow points to the discharge mark.

[0155] It can be observed that there are several thin and bright traces distributed on the crack surface, which are obviously different from the nearby blue-gray porcelain. These traces extend from the iron foot to the wire, and the length of some traces is only about 2 / 3 of the thickness of the porcelain. This is consistent with the analysis of the discharge process mentioned above. As water gradually flows into the crack, the electric field in the air gap is distorted, resulting in breakdown and the formation of an arc. The energy transferred by the arc to the crack surface causes the porcelain to melt. After the arc is extinguished, the molten porcelain cools and solidifies to form Fig.10 The traces shown. As the water evaporates and drains out of the crack, the arc will extend toward the wire. Some arcs extinguish before fully extending to the wire, resulting in discharge traces mainly on the iron foot side.

[0156] Take the 6 self-clearing discharges that occurred within 4 seconds in this test as an example. The waveform is as follows: Fig.11 As shown. The 2nd, 3rd and 6th discharges occurred in the rising stage after the voltage passed zero, while the 1st, 4th and 5th discharges occurred in the falling stage after the voltage reached the peak, showing the phenomenon of "post-peak discharge". At the moment of discharge, the voltage between the wire and the iron foot dropped rapidly, and the current surged. After 0.91 to 1.28ms, the voltage between the wire and the iron foot gradually recovered, which appeared as the arc extinction spike on the waveform. At the same time, the current dropped to zero and remained until the next discharge occurred.

[0157] by Fig.11 Taking the second discharge as an example, the power-resistance change curve between the wire and the iron foot is as follows Fig.12 As shown. After the discharge occurs, the system injects energy into the crack, and after a short oscillation process, it begins to decrease. When the energy decreases to about 60% of its maximum value, the resistance decreases by about 1.85%. Similarly, when the energy decreases to about 40% of its maximum value, the resistance decreases by about 25.6%. As the energy continues to decrease, the resistance begins to increase rapidly.

[0158] After the arc is cleared, the system enters the oscillation recovery process. The maximum overvoltage reaches 1.4 times the normal operating voltage of the system. Fig.11 The six self-clearing discharges shown can be divided into three groups: the first and second, the third and fourth, and the fifth and sixth. In each group, the subsequent discharge occurs after the previous discharge self-clears and before the system returns to normal. However, there is at least 40ms between the two discharges. During the previous discharge, the water that flowed into the crack was expelled due to the combined effect of Joule heating and the pressure caused by water vapor. This makes it impossible for the electric field strength to reach the breakdown threshold after the previous discharge self-clears, even if the air gap in the crack is subjected to the overvoltage of the system. The second discharge can only occur after water re-enters the crack and distorts the electric field in the air gap.

[0159] After 67 self-clearing discharge processes, the test was stopped actively. The morphology of the crack wall is as follows: Fig.13As shown in the figure, the yellow area is the area not affected by the early fault, the red area is the area affected by the early fault, and the red arrow points to the discharge mark.

[0160] It can be seen that as the number of discharges increases, more discharge marks appear on the crack wall, and these discharge marks become more obvious. At one of these marks, the crack surface is severely eroded. Taking the 17 self-clearing discharges that occurred within 7 seconds in this experiment as an example, the waveform is as follows Fig.14 shown.

[0161] Compared with the previous set of tests, although the neutral point grounding method has changed, the discharge waveform still shows similar characteristics. For example, the first and fourth discharges occurred in the decline phase after the voltage reached the peak, showing a "post-peak discharge" phenomenon. The discharge duration increased, but still did not exceed half a power frequency cycle.

[0162] by Fig.14 Taking the first discharge as an example, the power-resistance change curve between the wire and the iron foot is as follows Fig.15 shown.

[0163] Similar to the results in the ungrounded system, when the power was reduced to 80% of its maximum value, the resistance decreased by 3.81%, when the power was reduced to 60%, the resistance decreased by 5.38%, and when the power was reduced to 40%, the resistance increased by only 1.78%.

[0164] After the discharge is cleared, the resonant grounding system also enters the recovery process, but it is different from the recovery process of the ungrounded system. First, the voltage gradually rises over several cycles, generating an overvoltage of about 1.15 times the normal operating voltage of the system. Then it begins to decline until it returns to the normal voltage. Due to the delayed appearance of the maximum overvoltage in the resonant grounding system, the time interval between the two discharges will be longer.

[0165] After 191 self-clearing discharges, the fault becomes a permanent ground fault and can no longer be self-cleared. The crack wall has the following shape: Fig.16 The yellow area in the figure is the area not affected by the early fault, the red area is the area affected by the early fault, and the red arrow points to the discharge mark.

[0166] It can be seen that six very obvious discharge marks are formed on the wall. In addition to these six marks, there is also a discharge channel with a larger diameter, which is caused by the arc process during permanent breakdown. The surface morphology of the channel and the surface morphology of the area where no discharge occurs are photographed using a scanning electron microscope. The results are as follows: Fig.17 shown.

[0167] Fig.17It shows that the ceramic body around the channel has undergone a phase change. The crystal structure in the ceramic body has changed to an amorphous state (glassy structure). For areas without discharge, the ceramic body still maintains its crystal structure. This shows that the local temperature in the channel reaches more than 1300°C.

[0168] The test takes 1s at the beginning, 4s in the middle, and 2s at the end. The waveform within these 7s is as follows Fig.18 As shown. In the development stage of PIIF, the interval between two consecutive discharges is relatively long. However, as the number of discharges increases, the number of discharge traces increases, and the degree of crack surface erosion gradually intensifies. This increases the width of the crack, allowing more water to flow into the crack. After the arc is self-cleared, a certain amount of water remains in the crack, shortening the discharge interval. This eventually leads to a permanent ground fault. After the permanent fault occurs, a large amount of porcelain around the discharge channel melts. In the molten state, the metal oxides in the porcelain, such as Ionizes the charged particles. This increases the conductivity of the channel, making the fault unable to self-clear.

[0169] Early fault identification in distribution networks is a challenging and important topic. Many existing studies focus on the detection and treatment of permanent ground faults, ignoring the key significance of fault warning in improving the reliability of distribution networks. Through simulation, theoretical analysis and field tests, the present invention reveals the mechanism and electrical characteristics of PIIF. From the three aspects of start-up time, power resistance change trend and fault duration, the corresponding relationship between the development process of PIIF and its electrical characteristics is established. In addition, the existence of these characteristics is not affected by the porcelain insulator model and the neutral point grounding method. These conclusions lay the foundation for the identification and early warning of PIIF.

[0170] The present invention focuses on the fault development process and waveform characteristics at the fault point. Combining the theoretical basis with various waveform measurement units in the distribution network is the next step in proposing the PIIF identification method.

[0171] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A porcelain insulator early fault detection method, characterized in that: include: Simulate the change in electric field when water enters the cracks of porcelain insulators and establish an air-water two-phase flow simulation model; Analyzing the electrical characteristics at the start of discharge based on the electric field distribution data obtained by the two-phase flow simulation model; According to the initial arc conditions obtained from the electric field simulation and discharge initiation analysis, the relationship between arc voltage and current during arc burning and its influence on arc conductance and arc resistance are analyzed; According to the arc energy dissipation data calculated during the arc process, the characteristics of arc energy dissipation and air after discharge self-clearing are analyzed; Based on the analysis results, potential faults are identified; The establishing of the air-water two-phase flow simulation model includes simulating the water-gas two-phase flow inside the crack by using the Cahn-Hilliard equation and the Navier-Stokes equation, and calculating the electric field distribution at different time points in the air-water two-phase flow simulation model; The Cahn-Hilliard equation includes identifying different phase regions and transition regions between different phases by introducing a phase field variable φ, and the formula is: in, represents the partial derivative with respect to time t, which is used to describe the rate of change of φ with time; represents the convection term, u represents the velocity of the fluid in m / s, represents the gradient of φ, and the dot product represents the rate of change of φ in the velocity direction; represents the diffusion term, Represents divergence, used to describe The degree of divergence in space; coefficient represents the controlled diffusion rate, γ represents the mobility, and the unit is m 3 ·s / kg, λ represents the mixing energy density, the unit is N, ε represents the interface thickness parameter, the unit is m, ψ represents the phase field auxiliary variable; At the gas-liquid interface, the density ρ is smoothly varied across the two-phase interface. BD and viscosity μ BD Define it to mean: Among them, ρ w Indicates the density of water in kg / m 3 , ρ air Indicates air density in kg / m 3 , μ w Indicates the viscosity of water, in Pa·s, μ air Indicates air viscosity, unit is Pa·s; The Navier-Stokes equation is used to describe the mass and momentum transfer characteristics of incompressible fluids. Considering the influence of interfacial tension, the two-phase flow Navier-Stokes equation and continuity equation are expressed as: Where ρ represents the fluid density in kg / m 3 , μ represents dynamic viscosity, unit is Pa·s, represents the velocity gradient, represents the tensor transpose of the velocity gradient, p represents the flow inlet pressure in Pa, I represents the unit vector, F st It represents the interfacial tension of the two-phase fluid, the unit is N / m, g represents the gravity vector, the formula is Indicates the incompressibility of the fluid; Convection and diffusion in the interface region will cause changes in the interface free energy, which will increase the interfacial tension F st Defined as: The electrostatic field theory is used to analyze the electric field inside the insulator crack, and the electric field E is obtained through the potential: The analysis of the relationship between arc voltage and current during arc burning and its influence on arc conductance and arc resistance includes simulating the electrical behavior of the arc and using a heat balance equation to describe the dynamic change of arc energy: Among them, Q s represents arc energy, u represents arc voltage, the unit is V; i represents arc current, the unit is A; P loss represents the dissipated power; u and i represent the arc voltage and current respectively; Let g represent the arc conductance, then the equation can be transformed into: Considering how the heat generated by the arc affects the moisture in the crack through convection and conduction, calculate the effect of moisture evaporation caused by the arc heat on the resistance in the crack: Among them, ρ w Represents the resistivity of water, L w Indicates the length of the water column, S w represents the cross-sectional area of ​​the water column; The analysis of electrical characteristics at the start of discharge includes establishing a proportional porcelain insulator model, the geometry, location, width, depth of the crack and the electrical characteristics of the insulator, to ensure that the model reflects the physical and electrical characteristics of the actual crack insulator; The electric potential condition of simulating AC voltage is set in the proportional porcelain insulator model, the electric potential is defined as 8165×sin(100πt) of the top plane, and the bottom plane is grounded, simulating the electric field change under normal working voltage; The analysis of the electrical characteristics at the start of discharge includes setting the breakdown threshold E of the dielectric X , and compare the maximum electric field strength E in the crack area max Whether it exceeds the threshold E X , at any time, if E max More than E X ,It is predicted that the discharge will occur before the voltage reaches the peak; If E max Cannot exceed E X , then the electric field strength will decrease as the voltage decreases, and discharge will not occur; The potential fault identification includes: when an arc is detected in a crack of a porcelain insulator and the duration is less than a minimum time threshold t min When , it is judged that the arc is triggered and extinguished due to the high local electric field intensity; If air is left after the arc burns and the arc can be reignited within a short time after discharge, it indicates that there is a continuous high electric field strength and unstable dielectric conditions inside the crack; When the water in the crack evaporates due to the thermal effect of the current, and the calculated water evaporation energy exceeds the threshold value W min-lat When , it is judged that the moisture in the crack is reduced, and according to the inverse proportional relationship between the dielectric resistance and the moisture storage, it is judged that the dielectric resistance in the crack is increased.

2. The porcelain insulator early fault detection method according to claim 1, characterized in that: The analysis of arc energy dissipation and the characteristics of the air after discharge self-clearance includes, The water flowing into the crack will evaporate under the influence of the thermal effect of the current. The energy required for the evaporation process is W lat The calculation method is: W lat =ρ0V[c(T2-T1)+r] Where ρ0 represents the density of water in kg·m 3 , V represents the volume of water m 3 ; c represents the specific heat capacity of water kJ / (kg·K), T2 represents the boiling point of water at standard atmospheric pressure K, T1 represents the initial temperature of water K, and r represents the latent heat of evaporation of water kJ / kg; The water at the air-water interface will gain energy from the arc conduction, causing it to heat up and turn into steam, and discharge the unevaporated water from the cracks, so that the arc will not reignite after the current passes through zero. After the arc is extinguished, the subsequent discharge needs to wait for the water to re-enter the cracks.

3. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 2 are implemented.

4. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 2 are implemented.

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