CN101256212A - Comprehensive analysis test method for UHV power fittings - Google Patents

Abstract

The invention proposes a systematic comprehensive analysis test method for UHV level fittings which have a great influence on the safety of electric power production and operation. The method of self-defined modeling is used to form a systematic analysis method of modeling, calculation analysis, and test modification for the operating environment of electromagnetic fields of various string types of power fittings. It has changed the limitations of traditional power fittings industry estimation design and backward inspection and analysis methods. It provides technical support for the safe operation of extremely important UHV projects.

Description

Comprehensive analysis test method for UHV power fittings

technical field

The invention belongs to the technical field of ultra-high voltage power transmission and transformation, and relates to an analysis and optimization method for an electromagnetic field of an ultra-high voltage fitting, which is used to improve the electromagnetic environment for the operation of an ultra-high voltage line.

Background technique

UHV transmission has the advantages of long distance, large capacity, and low loss. It is an effective way to realize the optimal allocation of energy resources and can achieve good social and economic comprehensive benefits. The longer the transmission distance, the more obvious the advantages of UHVDC transmission in the comparison of technical and economic indicators. In the "Eleventh Five-Year Plan" of my country's power grid, DC UHV transmission will develop together with AC UHV transmission, and will eventually become an important part of the national backbone grid.

According to the characteristics of the DC transmission line, the present invention conducts numerical calculation and analysis on the electric field characteristics of the fittings of the ±800kV UHV DC transmission line, and proposes a reasonable design scheme to reduce the voltage sharing ratio of the insulators, so as to avoid strong corona discharge phenomenon. The safe operation of HVDC transmission lines provides a theoretical basis and promotes the rapid development of UHV transmission projects in my country.

At present, reducing the voltage sharing ratio of insulators mainly depends on experience. Generally, it is randomly set on the second or third piece of the insulator string, and then it is properly verified according to the field test results. For UHV grades, the electric field intensity is larger than before, and the electric field distribution is quantitatively studied. It plays an important role in reducing the voltage sharing ratio of UHV grade insulators.

Contents of the invention

The present invention is mainly aimed at the fact that the insulator string voltage sharing rate on the high-voltage side of the current transmission line insulator string is too high, which causes accelerated aging of the insulator string, and this problem will be more serious in UHV grade transmission lines. As the voltage level increases, the electromagnetic environment problems of transmission lines become more serious, and reducing the level of visible corona and radio interference is an extremely important indicator.

The present invention is achieved by taking the following technical solutions:

1. Study the influence of the size, size and position of fittings such as grading rings and shielding rings on the potential distribution and electric field distribution of insulator strings, and propose reasonable improvement plans;

2. Analyze and calculate the electric field distribution of connecting fittings, grading rings, and shielding rings, and propose an optimal design scheme for fittings according to the analysis results;

3. The technical scheme of the present invention is specifically described as follows:

(1) The first part of the technical solution: the establishment of the calculation model

Assuming that no corona is generated under the applied voltage, the insulator is clean and dry, the air humidity is low, the surface leakage current and space current are negligible, and the charge on the metal cap of the insulator remains unchanged.

(1) Since the steel feet and ball caps of the two connected insulators are both metal and in contact with each other, they can be simplified as a whole;

(2) The connection between the insulator and the iron tower adopts a ball-end hanging ring, and the connection between the insulator and the wire adopts a bowl-head hanging plate and a wire clamp. The structures of these fittings are relatively complex. Since their own shapes have little influence on the entire field, there is no need for actual description. Considering that the model description structure is mainly to determine the relative positions of wires, towers and insulators, all these metal parts are simplified into cylinders. body;

(3) According to actual calculation experience, the umbrella structure and anti-fouling groove of the glass insulator have little influence on the electric field distribution in the entire field, so the anti-fouling groove is not considered in the modeling, thereby saving memory space and speeding up the solution.

3. The second part of the technical plan: finite element model

In the UHVDC transmission system under operation, due to the existence of towers, wires, etc., the electric field of the line fittings is distributed in a three-dimensional field, and its field structure and boundary are relatively complex. Therefore, this technical solution adopts a three-dimensional finite element calculation method suitable for multi-media complex fields to carry out calculation research. The boundary value problem corresponding to the finite element model is:

The first type of boundary includes: high-voltage end, busbar equipotential, low-voltage grounding end potential.

The second type of boundary includes: air surrounding surface, symmetrical surface, and homogeneous second type of boundary.

Insulator steel cap and steel foot: it is a suspended conductor.

(4) The third part of the technical solution: processing of unbounded boundaries

Since the electric fields of insulator strings, connecting fittings, protective fittings, etc. are all open-field problems, it is necessary to reasonably set the artificial truncation boundary. The boundary cannot be set too large, otherwise, the amount of calculation and storage required will be very large. If the boundary is set too small, the calculation accuracy will be poor. Since the Ansoft software provides the boundary processing method of the two-dimensional unbounded field, when calculating, we first treat the field of the insulator as an axisymmetric field without considering the influence of wires, iron towers, etc., and set the unbounded boundary as the Ballon boundary , and then determine the outer truncated boundary of the three-dimensional calculation field according to the two-dimensional calculation results.

According to the analysis of the electric field of UHV fittings and insulators, a key design scheme to reduce the initial voltage bearing ratio of insulators is proposed.

1. When the lifting distance of the voltage equalizing ring is changed, the voltage distribution of the first 10 insulators will be greatly affected. It is the most suitable selection that the present invention adopts the raising distance of 320mm to 370mm.

2. For the selection of the opening angle of V-type insulator strings, after meeting the requirements of the maximum wind deflection, it is relatively appropriate to choose an opening angle between 90° and 100°.

3. The field strength near the equalizing ring is relatively large, and the maximum field strength at the rough place can exceed the breakdown field strength of air. It is the key factor for the visible corona produced by line fittings. Therefore the present invention adopts the pressure equalizing ring of full circular large section (greater than 120mm).

The beneficial effects of the present invention are:

The comprehensive analysis test method for UHV power fittings can significantly reduce the voltage sharing rate of UHV transmission line insulators and improve the electromagnetic compatibility environment of transmission lines, which is of great significance to the UHV strategy currently being promoted by the country. The reduction of the visible corona and radio interference level of UHV fittings can reduce the height of line towers and the scope of land acquisition, which will greatly reduce the construction investment of transmission lines, and reduce the impact of transmission lines on the environment. The smooth progress of the high-voltage demonstration project closely follows the UHV development strategy.

Description of drawings

Figure 1 is a simulation model (1/2) of a V-shaped suspension string in the metal loop mode of a -800kV DC unipolar transmission line;

Figure 2 is the cloud diagram of the potential distribution of the XOZ and YOZ sections;

Fig. 3 is the potential distribution diagram of the insulator;

Fig. 4 is the electric field distribution cloud map of the XOZ section;

Figure 5 is a comparison diagram of the voltage bearing rate when the lifting distance of the voltage equalizing ring of string 1 is different;

Figure 6 is a comparison diagram of the voltage bearing rate when the lifting distance of the voltage equalizing ring of the string 2 is different;

Figure 7 is a schematic diagram of the V-shaped insulator string opening angle;

Figure 8 is a comparison diagram of the voltage bearing ratio of insulators at different opening angles (the first series);

Fig. 9 shows the electric field distribution (1/2) on the surface of the fittings and wires when the lifting distance of the grading ring is 270mm.

Detailed ways

According to the accompanying drawings, the technical solution of the present invention will be further described in detail.

The present invention is achieved by taking the following technical solutions:

1. Study the influence of the size, size and position of fittings such as grading rings and shielding rings on the potential distribution and electric field distribution of insulator strings, propose reasonable improvement schemes, and obtain engineering-significant conclusions.

2. Analyze and calculate the electric field distribution of connecting fittings, grading rings, and shielding rings, and put forward suggestions for the optimal design of fittings according to the analysis results.

3. Carry out simulation analysis on the electromagnetic interference problem of UHV DC transmission, and give appropriate suggestions for UHV DC transmission project according to the analysis results. Principle of the present invention is specifically described as follows:

1) The first part of the technical solution: the establishment of the calculation model

Assuming that no corona is generated under the applied voltage, the insulator is clean and dry, the air humidity is low, the surface leakage current and space current are negligible, and the charge on the metal cap of the insulator remains unchanged.

(1) Since the steel feet and ball caps of the two connected insulators are both metal and in contact with each other, they can be simplified as a whole;

(2) The connection between the insulator and the iron tower adopts a ball-end hanging ring, and the connection between the insulator and the wire adopts a bowl-head hanging plate and a wire clamp. The structures of these fittings are relatively complex. Since their own shapes have little influence on the entire field, there is no need for actual description. Considering that the model description structure is mainly to determine the relative positions of wires, towers and insulators, all these metal parts are simplified into cylinders. body;

(3) According to actual calculation experience, the umbrella structure and anti-fouling groove of the glass insulator have little influence on the electric field distribution in the entire field, so the anti-fouling groove is not considered in the modeling, thereby saving memory space and speeding up the solution.

2) The second part of the technical solution: finite element model

In the UHVDC transmission system under operation, due to the existence of towers, wires, etc., the electric field of the line fittings is distributed in a three-dimensional field, and its field structure and boundary are relatively complex. Therefore, this project adopts the three-dimensional finite element calculation method suitable for multi-media complex fields to carry out calculation research. The boundary value problem corresponding to the finite element model is:

The first type of boundary includes: high-voltage end, busbar equipotential, low-voltage grounding end potential.

The second type of boundary includes: air surrounding surface, symmetrical surface, and homogeneous second type of boundary.

Insulator steel cap and steel foot: it is a suspended conductor.

3) The third part of the technical solution: processing of unbounded boundaries

Since the electric fields of insulator strings, connecting fittings, protective fittings, etc. are all open-field problems, it is necessary to reasonably set the artificial truncation boundary. The boundary cannot be set too large, otherwise, the amount of calculation and storage required will be very large. If the boundary is set too small, the calculation accuracy will be poor. Since the Ansoft software provides the boundary processing method of the two-dimensional unbounded field, when calculating, we first treat the field of the insulator as an axisymmetric field without considering the influence of wires, iron towers, etc., and set the unbounded boundary as the Ballon boundary , and then determine the outer truncated boundary of the three-dimensional calculation field according to the two-dimensional calculation results.

The following is an explanation of the analysis and research on the voltage distribution and electric field distribution characteristics of the V-shaped suspension string insulators:

1) -800kV DC unipolar operation

①Simulation model

Since the insulator model has a symmetrical property (front and rear symmetry), only 1/2 of it needs to be calculated when modeling. The simulation model is shown in Figure 1. Note: The operating voltage of the DC transmission line is usually -800kV during unipolar operation. This is because the radio interference generated by the negative polarity voltage is smaller than that of the positive polarity voltage, and the lightning protection of the negative polarity voltage is better than that of the positive pole. .

②Calculation result

a. The cloud diagram of the potential distribution of the whole field is shown in Figure 2, which respectively shows the cloud diagrams of the potential distribution of the whole field in the XOZ and YOZ sections;

b. The voltage bearing rate of the insulator, as shown in Figure 3, the insulator potential distribution diagram, in which, string 1-the insulator string far away from the tower side. String 2-the insulator string near the tower side; Table 1 shows the voltage bearing ratio of each insulator in string 1 and string 2 calculated according to the built model;

Table 1 Voltage bearing rate of each insulator

c. The electric field distribution cloud diagram is shown in Figure 4, which shows the electric field distribution cloud diagram of the XOZ section;

d. The voltage bearing rate distribution of insulators with different voltage grading ring elevation distances is shown in Figure 5 and Figure 6. Figure 5 shows that when the voltage grading ring elevation distances are 270mm, 320mm, and 370mm, the calculated first The voltage bearing ratio of each insulator sheet in a string of insulators;

Figure 6 shows the calculated voltage bearing ratio of each insulator sheet in the second string of insulators when the lifting distance of the voltage equalizing ring is 270mm, 320mm, and 370mm respectively;

Table 2 and Table 3 show the voltage bearing ratio values of the first 10 pieces of insulators in the first string and the first 10 pieces of insulators in the second string when the lifting distance of the grading ring is 270mm, 320mm, and 370mm respectively.

Table 2 Comparison of voltage bearing ratios of the first 10 insulators in the first string at different lifting distances

Table 3 Comparison of voltage bearing ratios of the first 10 insulators in the second string at different lifting distances

e. The analysis results of the insulator voltage bearing ratio at different opening angles. Figure 7 shows a schematic diagram of the opening angle of a V-type insulator string. The opening angle is the angle between two strings of insulators. Figure 8 shows that when the opening angle is divided into Schematic diagram of the comparison of the voltage bearing ratio of each insulator sheet in the first string of insulators obtained according to the calculation results of the aforementioned model at 90 degrees, 100 degrees and 110 degrees,

f. The electric field on the surface of fittings and wires is shown in Figure 9, which shows the electric field distribution (1/2) on the surface of fittings and wires when the elevation distance of the grading ring is 270mm.

③ UHV power fittings based on electromagnetic field optimization design scheme.

a. When changing the lifting distance of the grading ring, it will have a great influence on the voltage distribution of the first 10 insulators. It is the most suitable selection that the present invention adopts the raising distance of 320mm to 370mm.

b. For the selection of the opening angle of the V-type insulator series, after meeting the requirements of the maximum wind deflection, it is relatively appropriate to choose the opening angle between 90° and 100°.

c. The field strength near the equalizing ring is relatively large, and the maximum field strength at the rough place can exceed the breakdown field strength of air. It is the key factor for the visible corona produced by line fittings. Therefore this patent adopts the pressure equalizing ring of full circular large section (>120mm).

The above-mentioned embodiments do not limit the present invention in any form, and all technical solutions obtained in the form of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims (5)

1, comprehensive analysis testing method for extra-high voltage electric power gold tool, it comprises that step is as follows:

(1) the electric Field Calculation model of the extra high voltage direct current transmission line gold utensil of the realistic environment of structure:

Suppose that corona free produces under institute's making alive, the insulator cleaning is dry, and air humidity is low, can ignore along face leakage current and space current, and the electric charge on the insulator metal cap remains unchanged;

The steel pin and the ball cap of two continuous insulators all are metals, and are in contact with one another, and are reduced to integral body;

Insulator adopts ball-eye with being connected of iron tower, adopts socket-clevis eye and wire clamp with being connected of lead, because the shape of ball-eye, socket-clevis eye and these gold utensils of wire clamp is little to whole field domain influence, above-mentioned gold utensil all is reduced to right cylinder;

The umbrella-shaped structure of glass insulator and antifouling groove, little to whole field domain Electric Field Distribution influence, in modeling, do not consider antifouling groove;

(2) adopt the dimensional Finite Element method that is applicable to the complicated field domain of multimedia that institute's established model in the step (1) is carried out computational analysis, determine the zoning of extra high voltage direct current transmission line gold utensil electric field, determine the cutoff boundary method of field domain;

(3) calculate of the influence of gold utensils such as grading ring, shading ring to the insulator chain electric field distribution characteristic;

(4) according to result of calculation, propose to reduce the appropriate design scheme of insulator voltage share rate: determine that suitable grading ring raises distance, determine suitable V-type insulator chain subtended angle, select the heavy in section grading ring of full circle shape, and grading ring is polished rough place in manufacturing and installation process.

2, comprehensive analysis testing method for extra-high voltage electric power gold tool according to claim 1, it is characterized in that, when not considering that lead, iron tower etc. influence, the field domain of insulator is treated as axially symmetric field, the unbounded border is set to the Ballon border, determines the outer cutoff boundary of three-dimensional computations field domain then according to two-dimentional result of calculation.

3, comprehensive analysis testing method for extra-high voltage electric power gold tool according to claim 1 is characterized in that, when change grading ring raise apart from the time, raise apart from 320mm in scope between the 370mm.

4, comprehensive analysis testing method for extra-high voltage electric power gold tool according to claim 1 is characterized in that, for the selection of V-type insulator chain subtended angle, after the requirement of satisfying maximum windage yaw, selects subtended angle between 90 degree are spent to 100.

5, comprehensive analysis testing method for extra-high voltage electric power gold tool according to claim 1 is characterized in that, the area of section of described grading ring is greater than 120mm.

Images