What points should be paid attention to in power supply design?

Key points of high voltage transmission line design

Author: Hu

In the process of power transmission, the safety problem should not be underestimated. It is necessary to strictly abide by national policies and relevant regulations, rationally design lines, and ensure the safety and stability of power channels while saving costs. This paper analyzes the problems existing in the design of high voltage transmission lines in engineering practice, and puts forward some feasible suggestions and corresponding improvement measures.

Keywords: high voltage transmission line; Design points; Security; Electric energy transmission

I. Introduction

The main task of high-voltage transmission line is to realize the transmission and distribution between power plant and substation, substation and power users, and it is also an important facility to realize high-quality transmission. The rapid development of economy has promoted the development of national electric power, and the demand for high-voltage transmission lines is increasing. In order to ensure the smooth progress of power transmission, we must consider all aspects of high-voltage transmission line construction, such as the design, products and construction of high-voltage transmission lines. The design of high voltage transmission line is the primary work of high voltage transmission line construction. Power workers should attach great importance to all aspects of high-voltage transmission line design, improve the effectiveness, practicability and safety of high-voltage transmission line design, and ensure high-quality power transmission.

Second, the characteristics and existing problems of high-voltage transmission lines

Compared with ordinary low-voltage transmission lines, high-voltage transmission lines are two completely different concepts, which are mainly manifested in the following aspects: ① In terms of safety and reliability, the safety of high-voltage transmission lines can rise to a strategic height related to the national economy and people's livelihood. This is because of the characteristics of high-voltage transmission lines, most of which are almost important transmission channels for load centers and power supplies. Its task of exchanging and distributing electricity is incomparable to ordinary low-voltage transmission lines. If the high-voltage transmission line fails, it will cause huge losses, and it is likely to paralyze a city or even a large area and the national defense industry. ② In terms of technical parameters, the electrical and structural parameters of high-voltage transmission lines are much more complicated and detailed than those of low-voltage distribution lines. The equipment used has complex technology, high difficulty, large tonnage, high structural stability and long distance. When an accident occurs, it is not only difficult to maintain, but also requires high maintenance technology and quality of spare parts. (3) Due to the complicated geographical environment along the route, it is necessary not only to cross mountains and rivers, but also to walk in the vast Gobi and urban villages. Due to many factors, especially traffic problems, it is difficult to implement. ④ In terms of operating parameters, there are higher technical specifications and operating specifications according to different voltage levels. In the actual operation and operation and maintenance process, we must strictly implement the operating norms and procedures, and a little carelessness will cause losses to the state and people's property, and even threaten personal safety.

Third, the problems and suggestions in the design

1, geological survey work

Geological survey is the primary link and foundation of high voltage transmission line design. The quality of design depends largely on the quality of geological survey. Before the implementation of geological survey, we should know the nature, characteristics, operation methods and construction conditions of the project in detail. Geological data should accurately reflect the details of topography, hydrometeorology, engineering geology and physical exploration along the line. The survey data should accurately reflect the changes of ground elevation along the line, the distribution of above-ground buildings and the management of underground pipe network. The quality of geological survey not only affects the quality of subsequent design work, but also fully reflects the sense of responsibility and professional ability of geological prospecting workers.

2, line path selection

The route selection of high voltage transmission lines is the main factor that determines the technical and economic indicators of the whole project. Under the current conditions, the choice of route is a concrete test of the technical level, policy level and problem-solving ability of engineering designers. In engineering design practice, engineering designers should not only be familiar with and master professional knowledge, but also deeply understand the knowledge and policies of other related industries when they are engaged in line selection.

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The scheme selection should be diversified, comparable and operable, the scheme combination should know how to seek advantages and avoid disadvantages, and the scheme optimization should be economical and reasonable to avoid hidden dangers for the specific implementation of the project.

3. Tower selection

At present, there are three types of towers commonly used in domestic high-voltage transmission line engineering, namely concrete towers, angle steel towers and steel pipe towers, and each type of towers has many different classifications. Various types of towers have corresponding technical regulations and specifications in terms of structural composition and use. Because all kinds of iron towers have certain conditions in use, their functions are different under different conditions, even in the same area under different meteorological conditions and different terrain conditions. Therefore, in the process of tower design and type selection, we should fully collect local relevant information, make scientific analysis, make careful calculation and carefully select the type according to the actual situation of the project location. Based on the principle of leaving room and considering the influence of climate change, it is necessary to comprehensively compare several schemes and screen out the tower combination results that are economical, safe, stable and in line with the actual situation of the project.

4. Tower foundation design

In engineering practice, there are many forms of tower foundation, such as common reinforced concrete precast foundation, common reinforced concrete cast-in-place foundation, digging foundation, pile foundation and anchoring foundation. Special foundation needs special design under certain conditions (such as long-span foundation, leaning tower foundation, etc.). ). According to different tower types and different geological and topographic conditions, different foundations and configuration methods are adopted. Therefore, in the process of design and use, it is necessary to analyze specific problems. Don't grab your eyebrows and beard, there is no on-site screening, no detailed calculation, and no blind selection and use of foundations according to the actual situation of the project. This situation can easily lead to the waste of the project and bring great hidden dangers to the normal operation after the project is completed.

Four. Problems needing attention in lightning protection design of high voltage transmission lines

Shielding protection in lightning protection design of high voltage transmission lines

The shielding protection in lightning protection design of high-voltage transmission lines is mainly to shield the external interference of high-voltage transmission line system with the help of computer technology and its device performance, thus protecting the equipment in power system. When designing the shielding protection scheme, we should pay attention to all aspects of the high-voltage transmission line before designing the shielding protection scheme, and then we can design a more effective and applicable shielding protection scheme to protect the equipment of the power system and its normal operation more effectively.

2. Grounding protection in lightning protection design of high voltage transmission lines

Grounding protection in lightning protection design of high voltage transmission lines actually refers to connecting the equipment of power system with the earth through grounding devices, which is a very traditional lightning protection method and the most effective safety protection measure. Its working principle is to introduce the strong current and voltage appearing in high-voltage transmission lines into the earth through grounding devices, so as to realize the lightning protection of power system equipment.

3. Lightning protection problems in lightning protection design of high voltage transmission lines.

The design of lightning rod for high voltage transmission lines has great influence on the quality of lightning protection design for high voltage transmission lines. At present, the lightning protection design of high voltage transmission lines mostly adopts double lightning protection wires. The advantage of using double lightning conductor is that it can effectively protect the phase line, reduce the shielding range of the phase line as much as possible, and reduce the phenomenon of lightning disconnection. In addition, the use of lightning rod can reduce the damage caused by lightning to high-voltage transmission lines, and then ensure the normal operation of power system.

4. Equipment protection in lightning protection design of high voltage transmission lines

Equipment protection in lightning protection design of high voltage transmission lines depends on various devices to realize lightning protection of power system. This lightning protection method is more complicated, because the staff of the power system need to check the equipment regularly and deal with the problems in time. If the problems in the equipment cannot be repaired, it is necessary to replace new equipment to protect the availability of lightning protection devices and increase the lightning protection effect accordingly. In addition, in order to improve the effectiveness of the lightning protection scheme, the distance between high-voltage transmission lines should also be considered. In the actual lightning protection design, as long as the ground protrusions are within 40 meters from the side conductors, some measures should be taken to improve them, so as to reduce their lightning attraction and avoid the lightning damage caused by these ground protrusions. Moreover, lightning protection devices should be installed where the ground protrusions appear, which can effectively prevent the impact of lightning on high-voltage transmission lines and ensure the normal power supply of high-voltage transmission lines and the normal operation of power systems.

Concluding remarks

The times are progressing and science and technology are developing. It is precisely because of these changes that China has gradually become stronger. In such a big environment, we should pay more attention to engineering design. High voltage transmission line is the main tool to complete power transmission and distribution. For this reason, designers should have a sense of responsibility and mission. At the same time, they should learn more new professional knowledge, enrich themselves and improve their abilities.

refer to

[1] Shi Shengzhi. Research on live working tools and working methods for AC UHV transmission lines [D]. North China Electric Power University, 20 13.

[2] Research on Yao Xin ±660kv DC transmission tower and stringing technology [D]. North China Electric Power University, 20 14.

Li Shuang. Research on Path Optimization and Engineering Design of Anxin 35KV Transmission Line [D]. North China Electric Power University, 20 14.

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The power supply design of residential quarters must determine the nature, capacity, grade and building electrical design standard of power supply according to the construction scale, building type and standard of residential quarters. Based on reality, moderately ahead, to meet the needs of development.

(1) 19 floors above the high-grade residential and ordinary residential fire electricity, residential hospitals (equivalent to county) important electrical equipment for the first-class load; 10- 18 floor ordinary residential fire electricity, high-rise ordinary residential elevator, domestic water pump, staircase lighting electricity and residential district-level shopping mall business hall, lobby lighting, elevator and fire electricity with an area of more than 3000ff 12 are secondary loads; The electricity consumption of other residential quarters and public buildings that are not within the above range is Grade III load.

(2) There are two methods to calculate the load density: the first method is the capacity per unit area, that is, 25W/m2 for ordinary houses and 60W/m2 for air conditioners.

The other is based on household electricity consumption.

The first method can be used for preliminary estimation in planning and design stage, and the second method can be used for correction in engineering design stage. (3) According to the building area and building area, the selection of substation should follow the following principles:

(1) every 2krTi2 or 40× 10' set up a lOkV substation with a total construction area; When the load capacity of the community exceeds 3× 104 kVA, the llO/ 10kv substation can be considered.

(2) Substations are generally equipped with one transformer in each group. The service building area should be controlled at 3 -5× 104. High-rise residential buildings and public buildings should be equipped with a single transformer. The area of the distribution room should leave room for development.

(3)③ 10kv distribution station and substation should be box-type, which has the advantages of reducing floor space, saving investment, and facilitating rotation and maintenance.

(4) Capacitor compensation should be carried out at the low voltage side of each substation.

⑤ Set electric meters according to the charging methods of local power supply departments and the regulations of municipal (street lamp) departments.

(4) Wiring of high and low voltage distribution system and laying of outdoor wires

(1) When there is a first-class load in the residential area, dual power supply and single bus should be used for sectional power supply. For the community with the highest secondary load, appropriate reliability guarantee should also be given under possible conditions.

(2) 10kv distribution system shall be connected through closed-loop network. At this time, the Lokv side of the substation consists of three units, namely, the incoming and outgoing lines and the transformer room (lightning arrester is added on the bus). Load switches without fuses can be selected for incoming and outgoing lines.

When two lOkV power supplies are used, one is standby and the other is used, the open-loop network is used for wiring operation.

③ The power supply radius of l0/0.4/0.23kV substation should be less than or equal to 250m, the power supply voltage of 380/220V is three-phase four-wire system, and its low-voltage outgoing lines are divided into the following three types:

Radial: that is, each building is directly powered by cables. The advantage of this distribution method is that it does not affect each other in case of failure, and the disadvantage is high cost.

Trunk type: that is, the cable is distributed overhead after being led to the load center. The advantages of this distribution mode are low investment and convenient maintenance, but it takes up space and affects the appearance.

Ring network connection: each staircase is internally provided with a 7c junction box. The power supply reliability of closed-loop network connection is obviously greater than that of open-loop network connection.

(4) For residential quarters with a certain scale, outdoor wires are generally laid by cables, which can be directly buried when the number is small, and cable pipe blocks or cable tunnels should be used when the number is large; If the scale of the community is small, in order to save investment, the overhead form or the combination of cable and overhead can be adopted.

The depth of directly buried cable shall not be less than 0.7m, and protection and anti-freezing measures shall be taken.

⑤ lOkV power supply is usually used for high-rise residential buildings, and low-voltage power supply can also be used if it is close to the substation.

⑥ Insulated wires should not be directly buried outdoors. For non-important loads, when the line distance is less than 15m, the permeable gas pipe (GG) should be buried, but reliable waterproof and anticorrosion measures should be taken.

⑦ Single-phase 220V power supply can be used for lighting loads below ⑦30A, otherwise 380/220V three-phase four-wire power supply system should be used.

(5) Design of weak current part in residential area

(1) The telecom design of residential area is generally planned and designed by the telecom professional department, and telecom sub-offices and telephone stations can be set according to the size of residential area. When the telephone station is built together with other buildings, it should be located in the room below the fourth floor and above the first floor (in non-humid areas), with the windows facing south. Telephone communication lines shall be embedded in the housing.

(2) Outdoor telephone cables shall be laid in the same way as the power lines. If they are directly buried, they shall be parallel to the power cables, and the distance between them shall be 0.5m.

③ The receiving mode of cable TV signal source is decided by local cable TV station. Generally, there is only one set of receiving equipment in a residential area, which is transmitted to the building through a coaxial cable with a characteristic impedance of 75Cl. When overhead mode is adopted, it shall not be directly laid on the roof between two buildings, otherwise it shall be lowered to the lightning protection area: the overhead cable shall not be less than 4.5m, and its suspension wire shall be grounded by lightning protection. In areas where there is no cable TV, we should consider setting up an antenna TV system.

(4) Fire fighting system and safety alarm, call for help and intercom system should be set up in the community.