CN-121997553-A - Transient-steady-state combined direct-current GIL temperature rise distribution rapid calculation method

CN121997553ACN 121997553 ACN121997553 ACN 121997553ACN-121997553-A

Abstract

The invention relates to the technical field of numerical simulation of power equipment, and discloses a transient-steady-state combined direct-current GIL temperature rise distribution rapid calculation method, which comprises the steps of firstly constructing a multi-physical field coupling model and obtaining initial joule heat source density; the method comprises the steps of firstly, carrying out a flow field framework, then introducing an artificial viscosity model controlled by flow field characteristic monitoring criteria, carrying out self-adaptive transient pre-calculation based on viscosity residual error cooperative relaxation, establishing a flow field framework while inhibiting numerical oscillation, then carrying out space mapping transmission based on momentum energy ratio, carrying out space reconstruction and momentum compensation on a transient speed field by using a constructed correction operator to generate an equivalent steady state solving initial value, and finally starting a steady state solver by using the initial value, and carrying out closed loop iteration comprising conductor resistivity update and closed cavity air pressure correction under a real physical environment until convergence.

Inventors

ZHANG CHANGHONG
XIE CHAO
LI MINGYANG
LI WEIGUO
YANG XU
HUANG JIAJIE
HOU MINGCHUN
YAO JUN
MAO QIANG
LU CHANGAN

Assignees

中国南方电网有限责任公司超高压输电公司电力科研院

Dates

Publication Date: 20260508
Application Date: 20251224

Claims (10)

1.A transient-steady-state combined direct-current GIL temperature rise distribution rapid calculation method is characterized by comprising the following steps: s1, constructing a three-dimensional multi-physical field coupling model of a direct-current gas-insulated power transmission line, performing grid discretization, setting material basic parameters, and solving a steady-state current conservation equation based on an ambient temperature condition to obtain initial joule heat source density; s2, loading the initial Joule heat source density obtained in the step S1 to a transient solver, introducing an artificial viscosity model controlled by a flow field characteristic monitoring criterion, executing self-adaptive transient pre-calculation based on viscosity residual error cooperative relaxation, establishing a flow field skeleton while inhibiting numerical oscillation, and outputting transient terminal field data comprising a speed field, a temperature field and a pressure field; S3, reading the transient terminal field data output in the step S2, performing space mapping transmission based on a momentum energy ratio, and performing space reconstruction and momentum compensation on a transient speed field in the transient terminal field data by using a correction operator constructed by a viscosity ratio and a flow state index to generate a steady state solving initial value equivalent in physical sense; And S4, starting a steady state solver by using the steady state solving initial value generated in the step S3, calculating in a real physical environment without the artificial viscosity model, and executing closed loop iteration comprising conductor resistivity updating and closed cavity gas physical property pressure correction until calculation convergence, and outputting a finally corrected steady state temperature field and flow field distribution.
2. The method for quickly calculating the transient-steady-state combined direct-current GIL temperature rise distribution according to claim 1, wherein in step S1, the process of constructing the three-dimensional multi-physical-field coupling model comprises: Generating a multi-layer prismatic grid in a region of the fluid domain, which is close to the solid wall surface, aiming at the fluid-solid coupling interface, analyzing the velocity gradient and the temperature gradient of the near wall surface, and meeting the solving requirement of the non-dimensional wall surface distance; the control equation set of the three-dimensional multi-physical field coupling model comprises a fluid mass conservation equation and a fluid momentum conservation equation aiming at an insulating gas region and a multi-physical field energy conservation equation aiming at a whole domain, wherein the fluid momentum conservation equation comprises pressure gradient force, viscous stress terms and buoyancy source terms.
3. The method for rapidly calculating the transient-steady-state combined direct-current GIL temperature rise distribution according to claim 1, wherein in step S1, the specific process of obtaining the initial joule heat source density is as follows: assuming that the whole system is at a uniform environment initial temperature, calculating potential distribution inside the high-voltage conductor by utilizing the steady-state current conservation equation; Based on the calculated potential distribution, an initial joule heat source density at an initial time is calculated from the relationship between the electric field strength and the conductor conductivity at an ambient initial temperature.
4. The rapid calculation method of transient-steady-state combined direct-current GIL temperature rise distribution according to claim 1, wherein in step S2, the artificial viscosity model is specifically constructed by using an effective dynamic viscosity model; The effective dynamic viscosity model defines that the effective dynamic viscosity of each time step is the product of the real physical viscosity of the insulating gas and an artificial gain term, the artificial gain term is composed of the sum of a unit value and a dimensionless artificial viscosity relaxation factor, and the initial value of the dimensionless artificial viscosity relaxation factor is set to be a preset high value, so that the fluid at the initial moment presents the target viscous characteristic and the Reynolds number is in a laminar state.
5. The method for rapidly calculating the transient-steady-state combined direct-current GIL temperature rise distribution according to claim 4, wherein in step S2, the specific process of performing the adaptive transient pre-calculation based on the viscosity residual collaborative relaxation comprises: calculating the convective heat transfer intensity of the surface of the high-voltage conductor in real time by adopting an average Knoop number calculation formula; Calculating a time change rate characteristic value of the Knoop number subjected to filtering treatment by utilizing the convection heat exchange intensity and combining a Knoop number derivative smoothing characteristic value formula; Substituting the characteristic value of the time change rate of the Nussel number into an artificial viscosity relaxation factor evolution equation, and updating a dimensionless artificial viscosity relaxation factor of each time step by combining a flow field stability gating function, wherein the flow field stability gating function dynamically outputs a first state value to forcedly lock the current artificial viscosity or outputs a second state value to start a viscosity attenuation process according to the magnitude relation between the characteristic value of the time change rate of the Nussel number and a preset flow field stability criterion threshold; when the characteristic value of the time change rate of the Nussel number is smaller than a preset tolerance of the change rate of the Nussel number, judging that the transient pre-calculation meets a termination condition; the flow field stability criterion threshold is a preset value for representing tolerance to the variation rate of the Knoop number, and the variation rate tolerance of the Knoop number is a preset tolerance value for judging whether flow field evolution tends to be in a quasi-stable state or not.
6. The method for rapidly calculating the transient-steady-state combined direct-current GIL temperature rise distribution according to claim 4, wherein in step S3, the specific process of constructing the correction operator comprises: determining the theoretical amplification factor of the speed field by using the ratio relation between the effective dynamic viscosity and the actual physical viscosity at the transient calculation end moment as a viscosity ratio and combining a flow state index and adopting a theoretical correction operator calculation formula; Comparing the theoretical amplification factor with a preset upper limit threshold of the numerical stability of the correction operator by using an application correction operator limiting formula, and performing small value processing to obtain an application correction operator finally applied to a speed field; defining the application correction operator as the correction operator; the correction operator numerical stability upper limit threshold is a preset value determined according to the Kurthia constraint relation between the grid size and the time step.
7. The method of claim 6, wherein in step S3, performing the specific process of generating the steady-state solution initial value based on the spatial mapping transfer of the momentum-energy ratio comprises: Substituting the transient speed field vector in the transient end field data output in the step S2 and the application correction operator determined in the step S3 into a steady-state initial speed field reconstruction formula to perform product operation, so as to obtain an initial speed field vector transmitted to a steady-state solver; And combining the initial velocity field vector with a temperature field and a pressure field which are directly transmitted in the transient terminal field data to form the steady state solving initial value.
8. The method for rapidly calculating the transient-steady-state combined direct-current GIL temperature rise distribution according to claim 4, wherein in step S4, the calculating under the real physical environment where the artificial viscosity model is removed specifically means: and forcibly setting the dimensionless artificial viscosity relaxation factor to be zero, so that the hydrodynamic viscosity is strictly equal to the real physical viscosity at the current temperature, and solving a steady state Navier-Stokes equation, a continuity equation and an energy equation.
9. The method of claim 1, wherein in step S4, the specific process of performing the update of the conductor resistivity in the closed loop iteration comprises: extracting the volume average temperature of the high-voltage conductor in a steady-state iteration process; And updating the resistivity of the conductor and the Joule heat source power density by using the volume average temperature and a conductor resistivity temperature change correction formula.
10. The method of claim 9, wherein in step S4, the specific process of performing the correction of the gas physical pressure of the closed cavity in the closed loop iteration until the calculation converges comprises: Updating the background pressure of the closed cavity by using the ratio of the average temperature of the insulating gas domain in the current iteration step to the ambient temperature in the initial inflation process through a constant volume air pressure correction formula; The solver automatically updates the global gas density field by using the updated background pressure as the operation pressure; calculating relative errors by adopting double relative error convergence criteria based on the resistivity and Joule heat source power density updated in the step S9 and the background pressure updated in the step, and judging calculation convergence when the maximum relative errors of the resistivity and Joule heat source power density and the background pressure are smaller than a preset convergence tolerance threshold; the convergence tolerance threshold is a preset tolerance value for judging whether the power-heat-air multi-physical field coupling iteration reaches an equilibrium state or not.

Description

Transient-steady-state combined direct-current GIL temperature rise distribution rapid calculation method Technical Field The invention relates to the technical field of numerical simulation of power equipment, in particular to a transient-steady-state combined direct-current GIL temperature rise distribution rapid calculation method. Background A direct current gas insulated power transmission line (GIL) is a large-capacity power transmission device, and its internal temperature rise distribution affects the insulation strength of an insulating gas, the electrical performance of an insulator, and the tightness of a metal housing. The method for acquiring the steady-state temperature rise distribution of the direct-current GIL under the rated current carrying working condition has important significance for structural optimization and safe operation evaluation of equipment. At present, multi-physical-field numerical simulation is a main means for analyzing the temperature rise characteristics of the GIL. The GIL device has larger size, the internal filled insulation gas has lower dynamic viscosity, and the natural convection of the gas area is in a high Rayleigh number state under the drive of high-voltage conductor Joule heat. When the existing numerical calculation method is used for solving the problem of high Rayleigh natural convection coupling heat transfer, the problem that the calculation stability and the calculation efficiency are difficult to be compatible is faced. If the steady state solver is directly adopted for calculation, because the buoyancy driving force is larger than the fluid viscosity resistance under the condition of high Rayleigh number, the flow field is strong in nonlinearity, and numerical oscillation is easy to be caused by starting calculation under the condition that the initial flow velocity is zero, so that the solver is not converged. To solve the convergence problem, the prior art often employs a transient solver to simulate the process of starting the system from cold to thermal equilibrium. Because the heat capacity of the metal conductor and the insulating shell is large, the thermal time constant of the system is long, and the time step of transient calculation is limited by the stability of the flow field to be smaller. The time scale difference causes that transient calculation needs to execute a large number of time step iterations, the calculation is too long, the calculation force resources are occupied, and the requirement of quick solution in engineering analysis is difficult to meet. Furthermore, existing computational models have a simplification in the physical field coupling mechanism. The conventional method usually ignores the characteristic that the resistivity of a conductor increases along with the temperature rise, adopts a heat source model with fixed power density, or ignores the characteristic that GIL is a constant volume closed container, and the internal air pressure changes along with the average temperature rise, and only adopts a constant pressure boundary. The electric field, the thermal field, the flow field and the air pressure field are mutually influenced in the running process of the direct current GIL, and the calculated temperature rise distribution is deviated from the actual running working condition due to the simplification, so that the accuracy of the simulation result is influenced. Disclosure of Invention Aiming at the problems that in the multi-physical field coupling calculation of the existing direct current gas insulated transmission line, steady state calculation convergence is difficult due to the natural convection effect of high Rayleigh number, and simple transient calculation is too long in time consumption and cannot consider calculation stability and time efficiency, the invention provides a transient-steady state combined direct current GIL temperature rise distribution rapid calculation method. According to the method, transient pre-calculation is performed by introducing an artificial viscosity model to establish a flow field topology, and a result is transmitted to a steady state solver through a space mapping operator, so that quick and stable solving under a complex flow field is realized. In order to achieve the above purpose, the invention is realized by the following technical scheme: a transient-steady-state combined direct-current GIL temperature rise distribution rapid calculation method comprises the following steps: S1, constructing a three-dimensional multi-physical field coupling model of a direct-current gas-insulated power transmission line, performing grid discretization, setting material basic parameters, and solving a steady-state current conservation equation based on an ambient temperature condition to obtain initial joule heat source density; S2, loading the initial Joule heat source density obtained in the step S1 to a transient solver, introducing an artificial viscosity model controlled by