Design of electrical networks: technical requirements, installation and commissioning

In the construction of new power lines, transformer substations or reconstruction, expansion, rearmament with new technical means, the design of electrical networks is first carried out. Drawings, plans, load calculations are performed taking into account the current norms. The rules provide for requirements ensuring the reliable operation of networks, auxiliary units and facilities, reliable provision of consumers, improvement of technical indicators and quality of electric power produced. Electric power lines include lines from which urban and agricultural consumers are supplied with energy, including utilities, enterprises and organizations of the production, domestic and cultural spheres.

Requirements for electric grids of agricultural consumption

The direction of the development of rural consumers' electrical networks mainly concerns the installation of lines with a voltage of 35-110 kW. They are based on sectional lines with one main voltage circuit and mutual reserve, working from transformer complex substations. Lines with mutual reserves are powered from the inputs of various substations. If the power is supplied from one transformer, then the norms of technological design of electrical networks allow connection to different systems of one substation. The backup power connection is automatically made if necessary.

The new substations under construction are connected to the switchgear of the operating substation in the cut-off of the electric lines or according to the branching scheme taking into account the throughput of the existing network. If the new and old lines follow in parallel, then the question of transferring the existing transformer to increased voltage is considered.

Requirements for transformer substations

Substations of transformer equipment are intended for use by complete sections of industrial production and closed type, made of brick, reinforced concrete panels and blocks.

The project is based on unified structures and typical units, design of devices that are subject to industrial development is allowed, if their delivery is carried out by the time when installation begins. The design of electrical networks implies the indication in the documentation of delivery dates. Not allowed a wide variety of sizes of used building structures, the minimum quantity is used.

The decisions are made on the basis of the parameters of electric networks, economical design schemes after comparing several options. Preference is given to the design that provides the lowest costs. Technical parameters of electrical networks are selected in accordance with power flows in all modes of operation.

Calculated losses are taken on the basis of permissible values of the voltage losses at the input of the pick-up and the permissible voltage index in the central power supply system. If the technical data for calculating the allowable losses are not available, then 8% of the consumption of electricity, 6.5% of production lines, livestock complexes - 4% of the nominal value are used to calculate household utilities.

The loads are determined taking into account all electricity consumers that are powered by the designed transformer. Loads are taken with a prospect for 10 years, the definition of the wire and cable section is made for 5 years from the moment of commissioning. If the project has been lying for three years and has not been realized, then the construction of electric grids is not carried out on it, the documentation data are revised.

Indicators of reliability of electrical supply

Receivers of non-agricultural consumers, feeding on agricultural networks, are categorized according to the requirements for the reliability of electrical supply. The reliability standards for each category are set out in departmental documentation and are determined by the type of consumer's input device.

The design of a rural power grid depends on the category of consumers of agricultural production, communal and household supplies. The subdivision of them into 1 and 2 categories is given in the form of a list in the guidelines for providing electricity to agricultural electric receivers.

If consumers are not on the list, then they are classified in 3 categories. The power supply of the first two categories is provided by two interchangeable transformers independent of each other. Break their supply of electricity does not exceed the time of automatic restoration of power. For this purpose, an automatic backup power supply is provided at the input to the consumer.

The centralized power supply provides a second power source in the form of a substation with two transformers or two bus sections of the same substation. If the consumer is in remote access, then for him put an autonomous backup power transformer. For unforeseen backup power supply of receivers of the first two categories, which do not allow outages for more than 0.5 hours, the design of electrical networks provides a backup source of autonomous supply, regardless of the external power supply via main lines.

General rules

The design of the constructive part and master plan is carried out taking into account the final point of development of the substation, determined by the situational perspective at the time of design. Design of electrical networks is carried out according to the norms of the Land Code. These include the decisions of local councils at the appropriate level on the seizure of land from owners for the construction of energy complexes.

The design of electrical networks uses the following information:

• Customer requirements for connecting the substation to the power system;
• Requirements of electric receivers when connected to utilities;
• The requirements of the owners of land plots in relation to the transformer and networks;
• Norms of architectural and planning solution;
• Loads and their distribution by stages of substation development taking into account tensions and categories of users;
• Technical data on the maximum loads of the transformer;
• Prospective data on the total capacity of transformers and their number;
• Requirements for the construction of a connecting circuit;
• Ways to adjust the voltage value on the buses of the transformer substation.

Sources of the above data

The design of power supply to obtain the above requirements uses the following documents:

• Schemes of power development of electric lines and technical characteristics of external power supply of the facility;
• Conditions of technical connection of the power supply company;
• Documentation on the alienation of a land plot for construction;
• Technical parameters of the customer's task.

If there is no possibility of obtaining data from primary sources or the information is obsolete, engineers make the necessary calculations and determine the missing information at the preliminary stage of construction.

The design of electrical networks and systems, thermal power plants includes the following buildings and structures:

• Production premises and workshops, main building, electrical structures, water supply and heating systems, gas and oil installations;
• Buildings and buildings for auxiliary and production purposes, starting boiler houses, warehouses, administrative and household premises, workshops and oil refills;
• Auxiliary facilities, railway tracks, stations, depots, garages;
• Wastewater treatment plants, fences, roads, roads, landscaping, temporary buildings and bomb shelters.

The design work is carried out by specialists of a high technical level, the project provides for highly efficient devices and equipment. Technical solutions are based on ensuring reliability, saving of investments and costs for further operation.

Technological equipment is located and configured with the condition of providing convenient maintenance and repair, the desire for full mechanization and a reduction in the proportion of manual work. The instruction on designing of electric networks prescribes to have the rooms of the attendants and the cabins in the premises separated by walls from the working equipment. Inside, pipes for technological purposes are not laid, except for water supply, sewerage, heating and ventilation.

Management and automation

At modern power stations, control methods are provided with the use of an automated control system that allows to systematize work from a remote point, to regulate operations of calculation, signaling, protection, urgent communication. The scope of control work is adopted in the project in accordance with the instructions of departmental guidelines.

The volume of management operations is determined based on the direction of automation, the tasks of the technological processes at start-up, changing the load and stopping the operation of individual units or the entire system. Automatic control stations put various types: controlling block power stations, high-voltage lines and transformers with cross-links.

Block power plants are controlled from the central switchboard of compact distribution stands, auxiliary office control panels, general stationary installations of the compressor substation.

Measures to protect the land

Electric substations are located on the lands of private and municipal plots in accordance with the law on land legislation, a collection of acts on the protection of natural resources, building codes and regulations. The site of the future site is selected taking into account the link to the layout of the existing layout and general layout of the industrial enterprise.

The design of the regional power grid takes into account the fact that for the location of substations and electrical networks use non-agricultural land and land with low productivity. In the process of construction, a fertile layer of soil is cut and preserved, which are subsequently restored to unproductive land.

Owners of the sites involved are compensated for the agricultural land used. If the allocation of land is for temporary use, then in the future this soil is subject to secondary cultivation. The buildings in the areas allocated for the construction of power stations are economically located, the installation of subsidiary services in multi-storey houses prevails. New buildings do not block existing production and household facilities.

The design of distribution electrical networks occurs in strict accordance with the norms of building density, given in SNiP. The areas envisaged in the project for the further expansion of electrical networks are determined in accordance with the project design and economic justification. The areas of ash and slag dumps are calculated taking into account the further use of materials for fertilization in the national economy.

Entrances and roads to substation buildings are projected on one strip of land allotment, engineering communications, heating main lines, water supply and sewerage channels are placed compactly, the passing pipes do not violate the boundaries of agricultural lands.

Protection of airspace

For this purpose, when designing the project, measures and special devices are provided that ensure a reduction in the content of dust and harmful substances in the above-ground layer of the atmosphere to the standards of sanitary standards. This condition is ensured in different performance indicators of the transformer substation, including the mode of maximum power.

Measures to protect water areas

Wastewater treatment plants are constructed to protect water bodies from pollution by ingress of sewage into them. These facilities are built with due regard for sanitary standards. The method for processing waste industrial waters is selected depending on the specific operating conditions of the projected plant. High-voltage lines are built on the distances from reservoirs provided for in the regulations.

The cleaning method is affected by the type of equipment used and its capacity. The mode of use, the type of fuel, the way of removal of combustion products, the cooling system, climatic conditions and other technical parameters are taken into account. The planned discharge of sewage is coordinated with the services of state sanitary supervision, protection of fish reservoirs and other bodies.

Transport Displacement

Transport of external and internal cargo movement for the functioning of the substation is designed on the basis of a comparison of the technical and economic indicators of the options. Conveyor, railway, water, automobile or air transportation are used. Delivery of workers from their place of residence to the working area is carried out by the most efficient mode of transport, which allows to spend the least amount of time.

Transportation of goods and passengers to transformer substations located in industrial areas is tied to the general scheme of existing modes of transport and to the development of routes for future periods. There is a mutually beneficial cooperation of transport with neighboring operating and projected enterprises.

Reception, supply and storage of fuel oil, gas, oil

The daily demand for fuel oil is calculated based on the performance of all boilers with their normal capacity for 20 hours of operation. If the average temperature of the coldest month of the year is taken into account, then the calculation is carried out for 24 hours. Power plants that run on solid fuels are designed taking into account the construction of the firing unit. If water-heating peaking boilers are used, then their farming is combined with a pilot plant.

Designing of electric networks of the enterprise is made taking into account the supply of fuel oil to the starting boiler house from the main or secondary fuel oil unit. If gas is used as the main fuel, the gas regulating station is projected as part of the boiler house. The distribution node is located in the substation in a separate building or under a canopy.

The consumption of gas fuel is determined from the calculation of the maximum flow for all boilers. The gas supply is carried out separately for each distribution center, there are no planned back-up connections. The number of control devices in each distribution point is provided for one more, which is a reserve one.

Power stations are equipped with a transformer and turbine oil economy . The farm includes storage tanks for fresh and used products, pumping devices, drying plants, and recovery equipment. During the filling of transformers mobile degassing units, protected by nitrogen or film material, are used. In the substation complex, four turbine oil and transformer tanks are installed, two tanks are separately provided for the storage of engine oil.

Project of electricity supply at home

The project develops external electrical supply of residential and public houses, internal wiring is not included in its structure. Typical projects are designed to connect electric power consumers with a standard layout. If the location of the courtyard buildings is far from the standard solution, then the project is revised taking into account these changes.

The project of electricity supply of the apartment is mainly used in new buildings, in which the construction company is obliged to make the minimum number of connection points. There is a version of the project, which is called individual, allowing to include in the development of external, internal and economic power supply. The economic supply of electricity makes it possible to operate communication and air conditioning systems.

Procedure for registration of the project

The project of electricity supply of the apartment is based on technical conditions. They are developed by a representative of the electricity supplier, for which an application is submitted to the organization. The document states:

• The name and legal address of the facility;
• The design value of the voltage;
• Calculated load indicators;
• Type of connected voltage;
• Indicates the direction of energy use, for example heating and hot water production.

In addition to the application, the general plan of the site, documents on property, permits for works are enclosed.

In conclusion, it should be noted that the implementation of the project requires the availability of professional knowledge and a license, therefore, the specialists of the energy company are engaged in drafting the documents, the project alone is not done.