Power transmission line icing insulator flashover voltage probability prediction method

Abstract

The invention provides a power transmission line icing insulator flashover voltage probability prediction method, which comprises the following steps: S1, acquiring actual working condition environmental parameters of an insulator, S2, constructing a simulation model for a target insulator by adopting Fluent software based on the actual working condition environmental parameters, and simulating an air flow field and a water drop track in the simulation model; s3, determining a water drop collision coefficient and a freezing coefficient of a target insulator in the simulation model; s4, constructing an icing quality prediction model based on the water drop collision coefficient and the freezing coefficient, and determining the icing quality of the target insulator; and S5, the insulator icing pollution flashover voltage is determined based on the icing quality, the flashover voltage U50% is determined based on the insulator icing pollution flashover voltage, the flashover probability of the insulator is determined based on the flashover voltage U50%, and the flashover voltage probability obeys normal distribution.

Description

Technical Field

[0001] The invention relates to a method for predicting an insulator flashover voltage, and in particular to a method for predicting the probability of flashover voltage of iced insulators on a power transmission line. Background Art

[0002] The icing problem of transmission lines is increasingly becoming one of the important challenges to the stable operation of power systems. Icing not only increases the mechanical load on transmission lines, but may also lead to degradation of insulator performance, thereby causing flashover accidents, posing a serious threat to the safety and reliability of power systems.

[0003] In the prior art, the operation and maintenance of iced transmission lines is generally based on prior detection and post-processing, that is, parameter monitoring is performed manually or online before ice flashover occurs. Although this method can obtain corresponding parameters, it cannot judge whether ice flashover occurs on the insulator. It is only possible that flashover may occur, and then based on the staff's re-judgment, the prediction result is poor in accuracy. Post-processing is to perform corresponding operation and maintenance after the flashover accident occurs, which leads to power supply accidents.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for predicting the probability of flashover voltage of iced insulators on transmission lines. Based on the actual working conditions and environmental parameters, a corresponding insulator simulation model is established to simulate the operation process of the insulator under actual working conditions, and the ice-covered flashover voltage of the insulator is determined based on the operating process parameters, and then a probability distribution curve is determined based on the ice-covered flashover voltage, thereby improving the accuracy of the prediction results of ice-covered flashover accidents of insulators under actual working conditions, and providing more accurate data support for subsequent operation and maintenance.

[0006] The present invention provides a method for predicting the probability of flashover voltage of iced insulators on a transmission line, comprising the following steps:

[0007] S1. Obtain the actual working environment parameters of the insulator, including the liquid water content in the air, ambient temperature, wind speed, air pressure, and ice water conductivity converted to 20°C;

[0008] S2. Based on the actual working environment parameters, a simulation model of the target insulator is constructed using Fluent software, and the air flow field and water droplet trajectory are simulated in the simulation model;

[0009] S3. Determine the water drop collision coefficient and freezing coefficient of the target insulator in the simulation model;

[0010] S4. Construct an ice mass prediction model based on the water drop collision coefficient and the freezing coefficient, and determine the ice mass of the target insulator;

[0011] S5. Determine the insulator ice flashover voltage based on the ice quality, and determine the flashover voltage U based on the insulator ice flashover voltage 50％ , and based on the flashover voltage U 50％ The probability of insulator flashover is determined, where the flashover voltage probability follows a normal distribution.

[0012] Further, in step S4, the insulator ice flashover voltage is determined based on the ice mass as follows:

[0013] U=KN(γ 20 m) -a (P / P0) n ;

[0014] Among them, U is the predicted target insulator ice flashover voltage, K is the flashover voltage coefficient, N is the number of insulator strings, n is the air pressure influence index, P is the atmospheric pressure under the actual working condition of the target insulator, P0 is the standard atmospheric pressure, γ 20 is the conductivity of ice-covered water converted to 20℃, and m is the mass of ice.

[0015] Furthermore, the ice mass is determined by the following method:

[0016]

[0017] Where: α1 is the water drop collision coefficient, α2 is the freezing coefficient, ρ is the volume mass of liquid water, V is the wind speed, D is the diameter of the equivalent cylinder after the insulator surface is equivalent to a cylinder, L is the length of the insulator surface area equivalent to the cylinder, and t is the ice coverage time.

[0018] Furthermore, the water drop collision coefficient α1 is determined by the following method:

[0019]

[0020] Where: N trapped is the number of supercooled water droplets colliding with each area on the insulator surface, S0 is the projected area of ​​the cross section of each area of ​​the insulator in the incoming flow direction; b is the number of water droplets in the supercooled area per unit area at the inlet boundary.

[0021] Furthermore, the freezing coefficient is determined by the following method:

[0022] The surface area of ​​the insulator is equivalent to a cylinder with a length of L and a diameter of D;

[0023] Construct a freezing coefficient calculation model:

[0024]

[0025] Where: w is the liquid water content in the air, V is the wind speed, h is the convective heat transfer coefficient, T s is the ice-covered surface temperature when the ice-covered surface is in dynamic equilibrium, T is the ambient temperature, and D i is the equivalent cylinder diameter after ice coverage, d i is the ice thickness, N u is the Nusselt number; R e is the Reynolds number; P is the air pressure, where:

[0026]

[0027] The beneficial effects of the present invention are as follows: Through the present invention, a corresponding insulator simulation model is established based on the actual working conditions and environmental parameters, so as to simulate the operation process of the insulator under the actual working conditions, and determine the icing pollution flashover voltage of the insulator based on the operation process parameters, and then determine the probability distribution curve based on the icing pollution flashover voltage, so as to improve the accuracy of the prediction results of icing pollution flashover accidents occurring on the insulator under the actual working conditions, and provide more accurate data support for subsequent operation and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0029] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below:

[0031] S1. Obtain the actual working environment parameters of the insulator, including the liquid water content in the air, ambient temperature, wind speed, air pressure, and ice water conductivity converted to 20°C;

[0032] S2. Based on the actual working environment parameters, a simulation model of the target insulator is constructed using Fluent software, and the air flow field and water droplet trajectory are simulated in the simulation model;

[0033] S3. Determine the water drop collision coefficient and freezing coefficient of the target insulator in the simulation model;

[0034] S4. Construct an ice mass prediction model based on the water drop collision coefficient and the freezing coefficient, and determine the ice mass of the target insulator;

[0035] S5. Determine the insulator ice flashover voltage based on the ice quality, and determine the flashover voltage U based on the insulator ice flashover voltage 50％ , and based on the flashover voltage U 50％The probability of insulator flashover is determined, where the flashover voltage probability follows a normal distribution. In other words, the flashover voltage U 50％ Obey the normal distribution law, that is, U~N(u,σ 2 ), the normal distribution curve can be determined in advance by the prior art, and u in the distribution represents the flashover voltage U 50％ In the above process, the target insulator is simulated by the environmental parameters of the actual working conditions, so the collision coefficient and the freezing coefficient can be determined, and then the ice mass within the set ice time t can be predicted based on the freezing coefficient and the water drop collision coefficient, and then the corresponding flashover voltage U can be predicted, and then the flashover voltage U can be calculated based on the flashover voltage U 50％ ;Calculation of flashover voltage Uflashover voltage U 50％ It is determined by the existing method, which will not be elaborated here. Finally, the calculated flashover voltage U 50％ Substituting it into the normal distribution curve, the corresponding probability can be determined. Through the above method, the corresponding insulator simulation model is established based on the actual working conditions and environmental parameters, so as to simulate the operation process of the insulator under the actual working conditions, and determine the icing pollution flashover voltage of the insulator based on the operation process parameters, and then determine the probability distribution curve based on the icing pollution flashover voltage, so as to improve the accuracy of the prediction results of icing pollution flashover accidents of insulators under actual working conditions, and provide more accurate data support for subsequent operation and maintenance.

[0036] In this embodiment, in step S4, the insulator ice flashover voltage is determined based on the ice mass as follows:

[0037] U=KN(γ 20 m) -a (P / P0) n ;

[0038] Among them, U is the predicted target insulator ice flashover voltage, K is the flashover voltage coefficient, N is the number of insulator strings, n is the air pressure influence index, P is the atmospheric pressure under the actual working condition of the target insulator, P0 is the standard atmospheric pressure, γ 20 is the conductivity of ice-covered water converted to 20℃, and m is the mass of ice.

[0039] In this embodiment, the ice coverage mass is determined by the following method:

[0040]

[0041] Among them: α1 is the water drop collision coefficient, α2 is the freezing coefficient, ρ is the volume mass of liquid water, V is the wind speed, D is the diameter of the equivalent cylinder after the insulator surface is equivalent to a cylinder, L is the length of the cylinder equivalent to the insulator surface area, and t is the ice coating time. When calculating, the surface of the insulator needs to be equivalent to an equivalent cylinder with a length of L and a diameter of D. The surface area of ​​the equivalent cylinder is equal to the surface area of ​​the insulator, which can effectively simplify the entire calculation process and ensure the accuracy of the final result.

[0042] In this embodiment, the water drop collision coefficient α1 is determined by the following method:

[0043]

[0044] Where: N trapped is the number of collisions between supercooled water droplets and various areas on the insulator surface, S0 is the projected area of ​​the cross section of each area of ​​the insulator in the incoming flow direction; b is the number of water droplets in the supercooled area per unit area at the inlet boundary, and the parameters in the collision coefficient are all obtained based on statistics of the simulation software. Only through the simulation software can the parameters in the calculation formula of α1 be obtained.

[0045] The freezing factor is determined as follows:

[0046] The surface area of ​​the insulator is equivalent to a cylinder with a length of L and a diameter of D;

[0047] Construct a freezing coefficient calculation model:

[0048]

[0049] Where: w is the liquid water content in the air, V is the wind speed, h is the convective heat transfer coefficient, T s is the ice surface temperature when the ice is in dynamic equilibrium, T is the ambient temperature, and D i is the equivalent cylinder diameter after ice coverage, d i is the ice thickness, N u is the Nusselt number; R e is the Reynolds number; P is the air pressure, where:

[0050]

[0051] Among them, e(T s ) is calculated using the same formula as e(T). Here, e(T s ) and e(T) are both intermediate variables and have no actual physical meaning.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution 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 solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for predicting the probability of flashover voltage of iced insulators on transmission lines, characterized by: The following steps are involved: S1. Obtain the actual working environment parameters of the target insulator, including the liquid water content in the air, ambient temperature, wind speed, air pressure, and ice water conductivity converted to 20°C; S2. Based on the actual working environment parameters, a simulation model of the target insulator is constructed using Fluent software, and the air flow field and water droplet trajectory are simulated in the simulation model; S3. Determine the water drop collision coefficient and freezing coefficient of the target insulator in the simulation model; S4. Construct an ice mass prediction model based on the water drop collision coefficient and the freezing coefficient, and determine the ice mass of the target insulator; S5. Determine the insulator ice flashover voltage based on the ice quality, and determine the flashover voltage U based on the insulator ice flashover voltage 50％ , and based on the flashover voltage U 50％ The probability of insulator flashover is determined, where the flashover voltage probability follows a normal distribution.

2. The method for predicting the probability of flashover voltage of iced insulators on transmission lines according to claim 1 is characterized by: In step S4, the insulator ice flashover voltage is determined based on the ice mass as follows: U=KN(γ 20 m) -a (P / P0) n ; Among them, U is the predicted target insulator ice flashover voltage, K is the flashover voltage coefficient, N is the number of insulator strings, n is the air pressure influence index, P is the atmospheric pressure under the actual working condition of the target insulator, P0 is the standard atmospheric pressure, γ 20 is the conductivity of ice-covered water converted to 20℃, and m is the mass of ice.

3. The method for predicting the probability of flashover voltage of iced insulators on transmission lines according to claim 2 is characterized by: The ice mass is determined by the following method: Where: α1 is the water drop collision coefficient, α2 is the freezing coefficient, ρ is the volume mass of liquid water, V is the wind speed, D is the diameter of the equivalent cylinder after the insulator surface is equivalent to a cylinder, L is the length of the insulator surface area equivalent to the cylinder, and t is the ice coverage time.

4. The method for predicting the probability of flashover voltage of iced insulators on transmission lines according to claim 3 is characterized by: The water droplet collision coefficient α1 is determined by the following method: Where: N trapped is the number of supercooled water droplets colliding with each area on the insulator surface, S0 is the projected area of ​​the cross section of each area of ​​the insulator in the incoming flow direction; b is the number of water droplets in the supercooled area per unit area at the inlet boundary.

5. The method for predicting the probability of flashover voltage of iced insulators on transmission lines according to claim 3 is characterized by: The freezing factor is determined as follows: The surface area of ​​the insulator is equivalent to a cylinder with a length of L and a diameter of D; Construct a freezing coefficient calculation model: Where: w is the liquid water content in the air, V is the wind speed, h is the convective heat transfer coefficient, T s is the ice surface temperature when the ice is in dynamic equilibrium, T is the ambient temperature, and D i is the equivalent cylinder diameter after ice coverage, d i is the ice thickness, N u is the Nusselt number; R e is the Reynolds number; P is the air pressure, where:

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