Substation is one of the most important and widespread components in power delivery and distribution systems. With its help, the functions of current control, its conversion and reception are implemented. The quality of these and other tasks will depend on how competently the construction of the substation was completed, as well as its connection to the power line.
Substation design development
The following source materials are preliminarily prepared for the design solution:
- Terms of reference for the construction of the facility.
- Drawings and estimates.
- Construction schedule.
- Plans for the configuration, structural arrangement and materials of the substation.
- Information on the characteristics of electrical installations and construction mechanisms.
- Technological scheme of work processes.
- List of mounting hardware and fixtures to be used induring construction.
- Schemes of underground utilities indicating the map of the passage of cables, water lines and sewers.
Based on the above documents, a transformer substation project is being developed, which structurally describes the organizational map of work activities. It includes a comprehensive construction schedule with the sequence of technical operations, information on the volume of material resources, a situational plan, a transport scheme at the construction site, etc. Separately, the requirements for engineering and communication support, industrial sanitation and safety are indicated. In particular, the parameters of roads, bridges, stairs, toilets, fire extinguishing systems, etc. are described.
Varieties of substations
The degree of complexity of the object is also determined in the design decision. According to the level of complexity of the production of work activities, the following types of transformer substations are distinguished:
- Easy. Structures whose electrical installations operate under voltage from 35 to 154 kV. These are the most common substations, the construction of which is carried out within 1-3 months by one team of workers.
- Objects of medium complexity (voltage varies from 220 to 500 kV). The work involves several specialized teams for a period of 3 to 14 months.
- Especially difficult objects operating with voltage from 750 kV. Construction has been carried out for several years by a specialized organization.
Requirements for selecting a site for a substation
The choice of a future construction site for the construction of electrical substations is carried out on the basis of a master plan for the development of local territories, taking into account the requirements for the environment and environmental safety. For example, in accordance with sanitary and epidemiological standards, the distance from a transformer substation to a residential building should be at least 3 m, if we are talking about objects of low or medium fire resistance. Depending on the planned noise level from transformer substations, the minimum standard distance to residential buildings can reach 5-10 m.
The requirements for the design of the substation itself in terms of its energy efficiency are also taken into account. If possible, such structures should be located near the center of electrical loads, roads, engineering networks, etc. Often, before construction work, special landscaping of the territory is carried out for the future construction of the substation. The list of preparatory activities of this kind usually includes land work - for example, uprooting trees, removing vegetation, leveling the terrain, digging a foundation pit.
Ground requirements for substation placement
With regard to the characteristics of the soil, the site is selected taking into account engineering and geodetic studies of the territory, which include seismological, geological and hydrological information. In particular, the construction of substations is allowed on unsuitable foragricultural activities on land - as well as outside areas with industrial or natural pollution.
With regard to hydrological requirements, the level of groundwater should also be taken into account. It is not allowed to build in coastal zones, in places with erosion, near rivers and lakes. Even if it is planned to build a facility at a distance from natural hydrological features, the risks of flooding from natural runoff are taken into account. If such a danger exists, then, as a last resort, the appropriate landscaping of the territory must first be carried out in the form of creating slopes from a geogrid or other drainage-strengthening system. But such work and other preparatory measures should be evaluated from the point of view of economic feasibility. For example, for construction on soils that require an expensive foundation, a feasibility study must be completed.
Laying the foundation for the substation
Since we are talking about relatively light structures, structurally simple types of foundation platforms are used. These include reinforced concrete rod and pile structures, which are placed covering the entire perimeter of the target site. Lay foundations, for example, have the shape of the letter T and are placed horizontally relative to the surface - so that the body of the substation is strengthened vertically. Monolithic reinforced concrete platforms are laid on flat areas, and in the case of problematic terrain, it is allowed to install supportrods.
The most affordable and cost-effective foundation technology is the installation of load-bearing screw piles. The installation is implemented by screwing in steel pipes, after which a grillage is mounted, on which the construction of substations and adjacent buildings is carried out. This option is also advantageous for its versatility, as it allows construction on all types of soil except rocks. The reliability of the screw foundation is ensured by filling the pipe cavities with concrete and subsequent tying with a bar or channel. In the future, depending on the risks, additional props and fences are sometimes installed.
Construction of the structural part
Construction technology provides for the installation of building components and equipment on the laid foundation. Functional blocks are mounted on the foundation using metal profiles, ties and anchor connections. If necessary, special equipment can be involved in the working process, which ensures unloading at the place of operation. The structural blocks of the building of the transformer substation are installed using rope winches or by means of special trolleys. Sometimes an intermediate technological reinforcement zone is left between the substation block and the foundation. She is satisfied with standard stands or racks. If a reinforced concrete platform is used, then a special frame is welded to it, which will act as an intermediate base for the structure.
In the process of assembling the substation,connection of voltage winding leads to switchgears. With the help of compression plates, mounting electrical busbars are laid. During the construction of the ground part of the transformer substation, the coincidence of the horizontal and vertical axes of electrical contacts should be checked. Therefore, even before the installation of functional blocks, the technological connectors of the equipment must be removed and cleaned. This will allow the installation team to correctly position the structure in the area of the working site in accordance with the wiring diagram for electrical installations.
Installation of the main components of the substation equipment
Electrical units are delivered to the construction site and installed indoors. They are bolted together, interconnected through busbars, then cables are laid and the equipment is revised.
In the premises where the installation is carried out, finishing activities must be completed. After that, in accordance with the drawings, cable channels are laid. For closed devices, it is planned to cover with cement screeds and slabs. High voltage input is carried out both through underground cables in the provided channels, and through overhead lines.
Power transformers can occupy several rooms, which should be provided in the design solution. Moreover, during the construction of the substation, the possibility of fixing the transformer directly on the foundation or on the carrier substrate should also be technically thought out. Separate roomprovided for the installation of switchgear. The neutral of electrical installations is connected to the grounding device by welding. For grounding, special tires are preliminarily organized in the form of strips with a cross section of 40 x 4 mm. From them, a conclusion is made to the transformer.
Installation of systems for substation own needs
Regardless of the type of substation, it must have its own communication infrastructure - first of all, it concerns electrical power. To do this, an electrical grid facility is located on the site or at a distance. Moreover, this source should be calculated only for the needs of the substation without supplying third-party consumers. The power circuit provides service lines for various blocks, sections and nodes of the station. For this, cables and a ground loop are laid within a separate isolated route. A backup power supply channel is also connected to substations with a capacity of 330 kV or more, which can be an autonomous independent generator. It is not designed for continuous power - only for temporary technological or emergency operation.
Construction of auxiliary facilities
This complex includes oil facilities. The basis of its infrastructure is formed by stationary independent reservoirs of turbine oil. The volume of technical fluid should be 110% of the regulatory needs of a particular substation. If it is not possible to organize turbine reservoirs, then the oil economy should bearranged at the expense of a special platform with a canopy. Barrels with technical liquid necessary for supplying components and assemblies of the transformer substation are placed here. The construction of engineering structures that provide water supply and sanitation, in any case, focuses on the possibility of draining used oil through separate circuits for further disposal. That is, a special place is being organized for the storage of industrial waste from the substation.
Features of the construction of modular substations
In this case, an optimized design of a substation on a block-modular (sometimes mobile) basis is considered. Its construction does not require special engineering bookmarks and special conditions. This is a completely self-sufficient facility in terms of construction, including its own sources of energy supply. The average price of a transformer substation with a supply cable up to 10 kV is 4-5 million rubles. The package may include basic power plants, a distribution module and the necessary switches with input infrastructure.
Construction is carried out on a cleared flat area. At the first stage, a supporting metal platform is mounted on frames. Panel walls are attached to it, the fixation of which is carried out by means of hardware and clamping devices. The design of block transformer substations provides the necessary niches for the integration of electrical cabinets, protective and safety devices, cooling systems and oil supply. Installation of internal equipmentis also produced in accordance with the design scheme, according to which the equipment of the object should be selected.
The design and construction part of the work on the installation of electrical substations is implemented in accordance with the general technical standards that apply to engineering structures. At the same time, the operational specifics of the facility with its needs for communication support are also taken into account. In the case of stationary transformer substations, the price of construction and installation work can vary from 20 to 50 thousand rubles. Together with the cost of equipment, the implementation of the project can be several million rubles, as is the case with modular structures. The choice of the type of substation, its technical content and tactics of construction activities depends on many factors related to operational requirements and regulations.