High-voltage electrified body-electrified worker gap corona development model and pilot start judgment method

Abstract

The invention discloses a high-voltage electrified body-hot-line worker gap corona development model and a pilot start judgment method, and the method comprises the steps: carrying out the judgment according to the discharge physical process of a hot-line work combination gap, based on a long air gap discharge corona development model, a pilot start criterion and the like; a high-voltage electrified body-electrified worker gap corona development model is established, and a pilot initial judgment method corresponding to the model is provided. The model can simulate the corona development physical process of the gap between the high-voltage electrified body and the live working personnel under the operation impulse voltage by respectively simulating the potentials of the high-voltage electrified body and the live working personnel in the discharge development process, so as to calculate the regional space charge quantity of the gap corona region and judge whether the pilot in the gap is started or not; and a new model and a new method can be provided for live-line work combined gap discharge simulation research.

Description

A model for the development of corona between a high-voltage live conductor and a live-line worker, and a method for determining the initiation of the leader. Technical Field

[0001] This invention relates to the field of live-line work combination gap insulation simulation prediction, and in particular to a high-voltage live conductor-live-line worker gap corona development model and a leader initiation judgment method. Background Technology

[0002] With the rapid development of simulation computing technology and the deepening research on discharge mechanisms, it is now possible to simulate the discharge evolution process in long air gaps, determine the physical stages of the discharge, and predict the insulation status of the gap through modeling and simulation calculations. However, in live-line working combined gaps, the spatial structure of the gap is altered by the suspended potential of the live-line workers, making existing long air gap discharge simulation models unsuitable for direct application to insulation simulation prediction. Currently, conducting full-scale live-line working tests remains the only method for studying the breakdown process of live-line working combined gaps. However, full-scale tests suffer from problems such as heavy workload, long testing cycles, and high costs. Whenever a new voltage level emerges or the structure of the transmission tower undergoes significant changes, a new full-scale live-line working test is required to obtain the gap discharge characteristics. However, tower models, especially those for ultra-high voltage and extra-high voltage transmission towers, are enormous, making test setup difficult and requiring a large amount of steel for fabrication. Furthermore, the test requires the use of insulating ropes or rods to suspend the mannequin in the air, constantly adjusting its position to accommodate different gap lengths, further increasing the difficulty of test setup and workload. Furthermore, studying gap breakdown characteristics requires repeated application of operational impulse voltage dozens of times, which consumes enormous human and material resources. Therefore, establishing a high-voltage live conductor-live worker gap corona development model and a leader initiation judgment method that can describe the discharge evolution process and determine the physical stages of the discharge, and conducting simulation studies of the physical process of discharge in live work combined gaps, to replace or partially replace live work real-world tests, is of great significance for saving research costs. Summary of the Invention

[0003] This invention provides a corona development model and a leader initiation judgment method for the gap between a high-voltage live conductor and a live worker, in order to solve the technical problem of lacking simulation methods that conform to the actual discharge physical process of the gap in live work combinations to predict the development of the gap corona and the initiation of the leader.

[0004] To achieve the above objectives, the present invention provides a corona development model and a leader initiation judgment method for the gap between a high-voltage live conductor and a live worker, characterized by comprising the following steps;

[0005] S1. Establish a corresponding geometric model based on the required geometric structure of the gap between the high-voltage live conductor and the live worker, and set the live worker as the floating potential and the grounding electrode as the ground potential.

[0006] S2. Set the voltage on the high-voltage live conductor, and calculate the spatial electric field distribution along the axis of the gap between the high-voltage live conductor and the live worker, as well as the potential of the live worker.

[0007] S3. Use the corona initiation criterion to determine whether corona has started in the high-voltage side gap. If corona has not started, repeat step S2 to calculate the spatial electric field distribution of the gap axis and the potential of the live-line worker at the next moment until corona starts in the gap, and then the discharge enters the corona development stage.

[0008] S4. Calculate the spatial potential distribution along the gap axis and the potential of the person working on the live wire at this time, then calculate the length of the corona region of the gap, and construct a multi-layered ring charge corona development model.

[0009] S5. Calculate the potential and capacitance of each ring charge layer at this time, and then calculate the charge Q of each ring charge layer according to the following formula. i The total space charge Q in the corona region is obtained by summing the values. s ;

[0010]

[0011] In the above formula, C ij Let U be the capacitance between the i-th and j-th planar circles. i Let be the potential of the i-th layer plane circle.

[0012] S6, Determine Q s If the temperature reaches 1 μC, the gap leader is initiated and the simulation ends. If the temperature is less than 1 μC, step S5 is repeated to calculate Q at the next time step. s And reassess.

[0013] The corona development model is a virtual cone formed by rotating a third circle with a vertex angle of 120° around an axis of symmetry. The radius of the third circle is the axial length of the corona region. The axis of symmetry is vertical. The top of the virtual cone starts from the bottom of the high-voltage charged body and is composed of any number of parallel planar circles, with equal distances between each layer of planar circles.

[0014] Each layer of planar circles represents a layer of virtual ring charge. The number of charges in each layer is determined by formula (1). The potential of each layer of planar circles decreases from top to bottom according to the potential gradient of the corona region.

[0015] The voltage on the high-voltage live conductor, the potential of the worker operating the live conductor, and the spatial potential distribution in the gap all change with time. The simulation is performed step-by-step starting from time 0. If it is necessary to calculate the potential distribution at the next time step, then t = t + dt is used, and the potential of the worker and the spatial potential distribution in the gap are recalculated based on the voltage on the high-voltage live conductor at that time. The waveform of the voltage on the high-voltage live conductor is a positive polarity switching impulse voltage, which can be represented by a double exponential function.

[0016]

[0017] In the formula, A is the amplitude coefficient, and τ2 and τ1 are the time constants of the wave tail and wave front, respectively.

[0018] This invention offers the following advantages: First, the simulation method establishes a geometric model based on various conditions, including the dimensions of the high-voltage live conductor, the size of the live-line worker, the grounding electrode, and the gap distance. Then, based on the actual discharge physical process, it establishes a conical corona development model composed of multiple layers of ring-shaped simulated charges. This model calculates and updates the spatial electric field distribution, the potential of the suspended conductor, and the quantity of space charges in real time. Finally, it uses the corona initiation criterion to determine the discharge development stage. Applying the corona development model and the leader initiation judgment method to the study of insulation strength prediction for live-line working combination gaps shows good agreement between the calculated values ​​and the results of actual tests. The corona development model and the leader initiation judgment method have strong applicability in live-line working combination gaps of transmission lines. Applying them to the study of insulation strength prediction for live-line working combination gaps can replace or partially replace actual live-line working tests, saving research costs.

[0019] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 is a schematic diagram of the multi-layered simulated annular space charge in the corona region between a high-voltage live conductor and a live worker. Detailed Implementation

[0022] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0023] Example:

[0024] Step 1: Based on the required geometric structure of the gap between the high-voltage live conductor and the live worker, establish the corresponding geometric model and spherical air domain in the finite element simulation software COMSOL Multiphysics. In the "Electrostatics" module, set the live worker to a floating potential, and set the grounding electrode and spherical air domain to ground potential.

[0025] Step 2: Set the voltage on the high-voltage charged body to the applied voltage U. app (t).

[0026]

[0027] For a positive standard operating impulse voltage of 250 / 2500 μs, the following relationship holds:

[0028] U app (250)=U max

[0029]

[0030] U app (2500)=0.5U max

[0031] In the formula, U max Let A be the amplitude of the operating impulse voltage. Based on the above relationship, the amplitude coefficient A and the time constants τ1 and τ2 can be calculated.

[0032] Calculate the initial applied voltage U at the initial time t0. app The spatial electric field distribution along the axis of the gap between the high-voltage live conductor and the live worker (t0) is calculated, and the potential U2(t) of the live worker at this time is also calculated.

[0033] Step 3: Based on the spatial electric field distribution, use the corona initiation criterion to determine whether corona has started in the high-voltage side gap. If corona has not started, repeat step 2 to calculate the spatial electric field distribution along the gap axis and the potential U2(t) of the live-line worker at the next moment t=t+dt, until corona initiation occurs in the gap, and the discharge enters the corona development stage.

[0034] Specifically, the corona initiation criterion is: N2 ≥ N1.

[0035] N1 represents the initial electron avalanche occurring at the boundary of the ionization region, z = z i Number of electrons at:

[0036]

[0037] In the above equation, z1 represents the position of the initial electron avalanche head. The ionization coefficient α and adhesion coefficient η are both functions of the electric field strength and the air pressure, and their corresponding values ​​can be determined using the Boltzmann equation solving software BOLSIG+. N2 represents the total number of electrons generated during the secondary electron avalanche.

[0038]

[0039] In the above formula, f1f2 is taken as 1×10 -3 μ is taken as 6cm -1 g(l) is a characteristic function reflecting the partial disappearance of photons at the electrode, typically taken as 0.5, and r is the radius of the initial electron avalanche head.

[0040]

[0041] In the above formula, D e It is the electron diffusion coefficient, v e It is the drift velocity of the electron, and both are functions of the electric field strength E, which can be calculated in simulation software.

[0042]

[0043] Step 4: Calculate the spatial potential distribution along the gap axis and the potential U2(t) of the person working on the live wire at this time, then calculate the length of the corona region of the gap, and finally establish a multi-layer ring charge corona development geometric model in COMSOL Multiphysics.

[0044] Specifically, the length of the corona region between the high-voltage live conductor and the worker working on the live conductor can be determined using the simulated spatial potential distribution and the potential gradient E within the corona region. s The axial length x of the corona region was calculated. s The expression is:

[0045] U(x s )=U(0)-E s x s

[0046] In the above formula, U(x) is the spatial potential distribution along the gap axis, which can be calculated in simulation software.

[0047] The geometric model for the development of a multi-layered ring-shaped charge corona is a virtual cone formed by rotating a third-third circle with a vertex angle of 120° around an axis of symmetry. The radius of the third-third circle is the axial length of the corona region. The axis of symmetry is vertical. The apex of the virtual cone starts from the bottom of the high-voltage charged body and is composed of an arbitrary number of parallel planar circles, with equal distances between each layer of planar circles.

[0048] Step 5: Calculate the potential and capacitance of each layer of ring charge at this point. Each planar circle represents a virtual ring charge, and the number of charges in each layer is Q. i As determined by formula (1), the potential of each layer of planar circles decreases from top to bottom according to the potential gradient of the corona region;

[0049]

[0050] In the above formula, C ij The capacitance between the i-th and j-th planar circles can be calculated in simulation software, U. i The potential of the i-th layer plane circle can be calculated in simulation software.

[0051] Finally, the charge Q of each layer of virtual ring charge is... i By adding them together, the total space charge Q in the corona region can be calculated. s :

[0052]

[0053] In the formula, k is the number of virtual ring charge layers.

[0054] Step Six: Determine Q s If the temperature reaches 1 μC, the gap leader is initiated and the simulation ends. If the temperature is less than 1 μC, step five is repeated to calculate Q at the next time step. s And reassess.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A model for the development of corona between a high-voltage live conductor and a worker performing live-line work, and a method for determining the initiation of a leader, characterized in that: The process includes the following steps: S1. Establish a corresponding geometric model based on the required geometric structure of the gap between the high-voltage live conductor and the live worker, setting the live worker to a floating potential and the grounding electrode to a ground potential; S2. Set the voltage on the high-voltage live conductor and calculate the spatial electric field distribution along the axis of the gap and the potential of the live worker; S3. Use the corona initiation criterion to determine whether corona has started in the high-voltage side gap. If corona has not started, repeat step S2 to calculate the spatial electric field distribution along the gap axis and the potential of the live worker at the next moment, until corona initiation occurs in the gap, and the discharge enters the corona development stage; S4. Calculate the spatial potential distribution along the gap axis and the potential of the live worker at this time, and then calculate the length of the corona region in the gap to construct a multi-layer ring charge corona development model; S5. Calculate the potential and capacitance of each layer of ring charge at this time, and then calculate the charge Q of each layer of ring charge. i The total space charge Q in the corona region is obtained by summing the values. s ; In the above formula, C ij Let U be the capacitance between the i-th and j-th planar circles. i Let Q be the potential of the i-th layer of the planar circle. S6. Determine Q. s If the temperature reaches 1 μC, the gap leader is initiated and the simulation ends. If the temperature is less than 1 μC, step S5 is repeated to calculate Q at the next time step. s And reassess.

2. The corona development model and leader initiation judgment method for the gap between a high-voltage live conductor and a live-line worker, as described in claim 1, is characterized in that... The corona development model is a virtual cone formed by rotating a third circle with a vertex angle of 120° around an axis of symmetry. The radius of the third circle is the axial length of the corona region. The axis of symmetry is vertical. The top of the virtual cone starts from the bottom of the high-voltage charged body and is composed of any number of parallel planar circles, with equal distances between each layer of planar circles.

3. The corona development model and leader initiation judgment method for the gap between a high-voltage live conductor and a live-line worker, as described in claim 2, is characterized in that... Each layer of planar circles represents a layer of virtual ring charge. The number of charges in each layer is determined by formula (1). The potential of each layer of planar circles decreases from top to bottom according to the potential gradient of the corona region.

4. The corona development model and leader initiation judgment method for the gap between a high-voltage live conductor and a live-line worker as described in claim 1, characterized in that, The voltage on the high-voltage live conductor, the potential of the live worker, and the spatial potential distribution of the gap all change with time. The simulation calculation starts from time 0 and proceeds step by step. If it is necessary to calculate the potential distribution at the next time step, then t = t + dt is made, and the potential of the live worker and the spatial potential distribution of the gap are recalculated based on the voltage on the high-voltage live conductor at this time.

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