The substation is one of the most important and common components in the systems of delivery and distribution of electricity. With its help, the functions of current control, its conversion and reception are realized. The quality of these and other tasks will depend on how well the construction of the substation was completed, as well as its connection to the power line.
Substation Design
For the design solution, the following source materials are preliminarily prepared:
- Terms of Reference for the construction of the facility.
- Drawings and estimates.
- Schedule of construction work.
- Plans for the configuration, design and materials of the substation.
- Information on the characteristics of electrical installations and construction mechanisms.
- Technological scheme of work processes.
- The list with mounting accessories and devices that will be used during construction.
- Schemes of underground communications with an indication of the map of the passage of cables, water pipes and sewers.
Based on the above documents, a transformer substation project is being developed, which structurally describes the organizational map of work events. 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 communications 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 design decision also determines the degree of complexity of the object. The following types of transformer substations are distinguished by the level of complexity of the production of work events:
- Not complicated. Structures, electrical installations of which 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.
- Particularly complex objects operating with voltages from 750 kV. The construction is carried out over several years by a specialized organization.
Requirements for choosing a site for creating a substation
The choice of a future construction site for the construction of electrical substations is carried out on the basis of the general plan for the development of local territories, taking into account environmental requirements and environmental safety. For example, in accordance with sanitary and epidemiological standards, the distance from the transformer substation to the apartment building should be at least 3 m, if we are talking about objects of small or medium degree of 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 electric loads, roads, engineering networks, etc. Often, before the construction work, a special landscaping is carried out for the future construction of the substation. The list of preparatory measures of this kind usually includes land work - for example, uprooting trees, removing the vegetation layer, leveling the relief, and arranging a foundation pit.
Ground requirements for the substation
In relation to the characteristics of the soil, the site is selected taking into account the engineering and geodetic studies of the territory, which include seismological, geological and hydrological information. In particular, the construction of substations is allowed on land unsuitable for agricultural activities - as well as outside areas with industrial or natural pollution.
Regarding hydrological requirements, the level of groundwater occurrence must 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 construct an object away from natural hydrological objects, the risks of flooding from natural effluents are taken into account. If such a danger occurs, then, in extreme cases, the corresponding improvement of the territory in the form of creating slopes from the geogrid or other drainage-strengthening system should be preliminarily performed. But such work and other preparatory measures should be evaluated in terms of economic feasibility. For example, for construction on soils that require the installation of an expensive foundation, a feasibility study should be made.
Substation foundation
Since we are talking about relatively light structures, structurally simple types of foundation platforms are used. These include reinforced concrete bar and pile structures, which are placed with the coverage of the entire perimeter of the target site. Ledge foundations, for example, have the shape of the letter T and are placed horizontally relative to the surface - so that the substation body is strengthened vertically. Monolithic reinforced concrete platforms are laid on flat areas, and in the case of a problematic relief, support rods can be installed.
The most affordable and economically optimal foundation technology is the installation of 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 beneficial for its versatility, as it allows you to perform the construction on all types of soil except rock. 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 components of the structure and equipment on a mortgaged basis. Function blocks are mounted on the foundation using metal profiles, ties and anchor joints. If necessary, special equipment can be involved in the working process, which ensures unloading at the place of operation. The building blocks of the building of the transformer substation are installed using rope winches or through special trolleys. Sometimes an intermediate technological zone of strengthening is left between the substation block and the foundation. It suits at the expense of standard supports or racks. If a reinforced concrete platform is used, then a special frame is welded to it, which will act as the intermediate base of the structure.
During the assembly of the substation, the terminals of the voltage windings are connected to switchgears. With the help of the 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 the electrical contacts must be checked. Therefore, even before the installation of functional blocks, the technological connectors of the equipment must be removed and stripped. This will allow the installation team to correctly position the structure in the area of the working platform in accordance with the electrical installation map.
Installation of the main components of the substation equipment
Electrotechnical units are delivered to the construction site, which are mounted indoors. They are pulled together with bolts, connected to each other through busbars, then they lay cables and revise the equipment.
In the premises where installation is carried out, finishing measures should be completed. After that, in accordance with the drawings, cable channels are laid. For enclosed devices, cement screed and slabs are provided. 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 for in the design decision. Moreover, during the construction of the substation, the possibility of fixing the transformer directly on the foundation or on the supporting substrate should also be technically thought out. A separate room is provided for the installation of switchgears. The neutral of electrical installations is connected to the grounding device by welding. For grounding, special buses are pre-arranged in the form of strips with a section of 40 x 4 mm. From them, a conclusion is made to the transformer.
Installation of systems to meet the substation's own needs
Regardless of the type of substation, it must have its own communication infrastructure - first of all, this applies to electrical power. To do this, an electric grid facility is located on the site or at a distance. Moreover, this source should be calculated only on the needs of the substation without supplying third-party consumers. The power supply circuit provides service lines for various units, sections and nodes of the station. To do this, lay the cables and ground loop within a separate insulated route. A substation channel of power supply, which can be an autonomous independent generator, can also be supplied to substations with a capacity of 330 kV. It is not designed for constant 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 turbine oil reservoirs. The volume of technical fluid should be 110% of the regulatory needs of a particular substation. If there is no possibility of organizing turbine reservoirs, the oil industry should be arranged at the expense of a special platform with a canopy. Barrels with technical fluid necessary for supplying the nodes and assemblies of the transformer substation are placed here. In any case, the construction of engineering structures that provide water supply and sanitation is also oriented towards the possibility of draining used oil through separate circuits for further disposal. That is, a special place for storing industrial substation waste is also being organized.
Features of the construction of modular substations
In this case, we consider the optimized design of the substation on a block-modular (sometimes mobile) basis. For its construction does not require special engineering bookmarks and special conditions. This is a completely self-sufficient object from the point of view of construction, including its own sources of energy supply. The average price of a transformer substation with a supply cable of up to 10 kV is 4-5 million rubles. The package may include basic power installations, a distribution module and the necessary switches with an introductory infrastructure.
Construction is carried out on a cleared flat site. At the first stage, a supporting metal platform is mounted on the 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 equipment is also carried out in accordance with the design scheme, according to which the equipment of the facility should be selected.
Conclusion
The design and construction part of the installation of electrical substations is implemented in accordance with the general technical standards that apply to engineering structures. In this case, 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 may amount to several million rubles, as is the case with modular designs. The choice of the type of substation, its technical content and tactics for the production of construction measures depends on many factors related to operational requirements and regulatory rules.