An electrical substation (PS) is a key unit that makes it possible to organize a power supply system at facilities of various sizes, which is determined by the load-bearing level of the installation itself. Depending on the design, this type of equipment can increase or decrease the voltage, and this directly determines the intended purpose of the substation.

Main areas of application

The electrical distribution substation is responsible for receiving and converting electricity. In this case, the voltage can be lowered or increased, and, if necessary, straightened, which is determined by the needs of the consumer. At the next stage, the received energy is distributed. In cases where the voltage value is expected to increase, electricity is received, for example, from a generator, and then transmitted to the power line.

Let's watch a video of where electricity comes from:

If electricity is supplied from power lines, then in order to send it further to the consumer it is necessary to reduce the voltage. The serviced objects are production workshops, residential or urban types, microdistricts, etc.

Part of the equipment

Electrical stations and substations can be delivered to the installation site in a finished, fully assembled form or in separate blocks and assemblies, and the equipment will be called complete. Main elements and components:

1. A chamber for installing equipment in it, including a transformer, as well as a busbar. There are two versions: completely closed without mesh inserts and partially closed with a mesh-type fence.
2. Prefabricated tires. Together they represent an entire system. Electrical stations and substations can also contain separate sections, which are the same busbars separated by a switching unit.
3. A conductive system comprising busbars or cables that are connected to insulators. Such structures are located on supporting supports. It is with the help of this node electricity is transmitted.
4. Transformer in quantities from one to several units.
5. The switchgear ensures the reception and further distribution of energy. The switchgear consists of several units: switching equipment, busbars, control and protection elements.

Electrical substation design

Various types of electrical equipment of substations such as switchboards. devices are found in several versions: open, closed, complete. The first and second of these options involve use on outdoors or indoors. And complete versions, like any equipment with a similar name, are a prefabricated installation consisting of units ready for connection.

Review of existing species

Equipment of this kind is classified primarily by purpose.

In this case, the following are distinguished:

• Generating;
• Consumer;
• Conversion and distribution.

Electric generating stations and substations represent equipment responsible for generating energy, while consumer versions receive electricity from power lines and meet the needs of objects for various purposes. Converter-distribution analogues perform the function of converting voltage for the purpose of further distribution.

Equipment of this type is distinguished according to the set of tasks that are solved with its help:

• Transformer installations;
• Conversion analogues.

Transformer electrical circuit distribution substation allows you to lower or increase the voltage in accordance with the needs of the consumer, while converter technology is responsible for changing the electrical parameters (type of current, frequency value).

There is a division of such installations according to the level of importance in the energy supply system:

1. Major downgrades;
2. Deep input;
3. (power electric vehicles different types, be it railway trains, ground or underground vehicles);
4. Complete - they are a prefabricated installation consisting of individual units completely ready for connection.

Let's watch a video of what a traction substation is like:

Another type of classification represents electrical stations and substations that differ in connection diagram:

• Dead-end – receive power from one neighboring substation;
• Pass-through - equipment that is a single line with two-way power supply;
• Nodal units are a key link, since in addition to supply units they are also connected to transit units;
• Branch lines are part of the wiring of the power supply system.

In addition to the above listed versions, there is a special type of such equipment - an autonomous multi-type electrical substation. Its peculiarity lies in the ability to simultaneously combine two important functions: electricity generation, as well as its distribution further along the network, from where it goes to the consumer.

Parameters and connection diagram

There are several basic requirements for drawing up connection diagrams for the main components of electrical equipment that must be met:

1. Reliability of energy supply, consumer safety.
2. Minimum costs for operation and maintenance of equipment.
3. Convenience of working with technology.
4. Minimal risk of error in emergency situations when switching equipment operating modes is required.

The main electrical connection diagram of the distribution substation should depict the main components of the installation (switch switchgear, power transformers, switching devices, protective elements and control systems).

There are two ways of drawing up diagrams: multi-line and single-line. In the first case, all phases of the installation are necessarily shown, while the second option involves including an image of only one phase due to identity.

Figure 1 shows a single-line electrical diagram of a distribution substation, which reveals the operating principle of the installation that meets the needs of consumers of the third category. The main parameters are the value of HV and LV voltage (on the higher and lower side), as well as the power of the installation and the type of transformer.

Location standards and requirements

The main step-down substations should be located in close proximity to the areas of greatest load; workshop installations are always located as close as possible to the consumer. A more preferable option is a complete substation, since in this case there is no strong dependence on the building part during its installation.

Stand-alone installations require additional expenses for organizing supply networks, and at the same time losses increase. Much more preferable is the built-in option with a remote transformer.

There are permissible limits for the location of electrical equipment of this type regarding explosive serviced objects: from 0.8 to 100 m. The choice of a certain value from this range is determined by the degree of danger, as well as the location option (open, closed).

In order to ensure safe operation, as well as a sufficient level of reliability of operation of electrical equipment, the Government Russian Federation the security zone of the electrical substation is determined. This means that in the specified territory adjacent to such installations, there are restrictions on the use of land plots for their intended purpose.

Thus, given the wide choice of designs for electrical substations, their choice should be based on the compliance of the main parameters of the equipment with the operating conditions. This is the only way to ensure the safe operation of the installation, which is a key point when drawing up a connection diagram for such equipment. The complexity of a project to organize an energy supply system lies in the need to select a large number of equipment, as well as organize its coordinated operation. Therefore, a complete substation is often the preferred option.

Voltage determination on the low voltage side of the substation

If you need to calculate the voltage on the low voltage (LV) buses of substations, then the calculation must be supplemented with one more step. Voltage losses in the resistances of transformers and autotransformers and the presence of magnetic coupling between their windings must be taken into account.

Let us show the calculation sequence using the example of substation 1 of the previous diagram.

The figure shows a diagram of the connection of the elements taken into account when determining the design load of this substation 1 and indicates the powers that must be found and summed up when calculating .

Since the voltage U 1 is known (determined at the previous stage of calculation), the voltage loss in the resistance of the transformer Z t1 can be found from the voltage U 1 and power , flowing through resistance Z t1.

In this case, the voltage loss

,

and the reduced voltages on the low voltage buses of substations

.

The required voltage on the LV buses of substation 1

.

You can also use a method that involves bringing the parameters of the circuit and its mode to one transformation stage. In our example, it is advisable to bring the resistance of the LC line to a rated voltage of 110 kV. In this case, the ideal transformer is excluded from the equivalent circuit, points are combined, and resistance Z 4 is replaced by resistance:

When calculating, the voltage at point 3 should also be taken to be reduced to the same transformation stage as , i.e. think that . Both approaches to calculation are equivalent.

12.3. Calculations of the mode of lines with double-sided power supply at different voltages of power sources (at the ends)

It is widely used to calculate circuits with several independent power supplies. principle of superposition.

According to this principle, currents and powers in branches can be considered as the result of the summation of a number of components, the number of which is equal to the number of independent voltage sources.

Each of these currents is determined by the action of only one of the voltage sources when the voltages of other sources are equal to zero.

Lines with double-sided power supply with different voltages at the ends are among the electrical circuits with independent power sources. To calculate it, the superposition principle can also be applied.

Different voltages are specified at the ends of the line, for example U 1 >U 4 .

The power of the loads S 2 and S 3 and the resistance of the line sections Z kj are known, where k is the node at the beginning of the line section, j is the end node of the line section.

We need to find the power flows S kj .

In accordance with the principle of superposition known from TOE, a line can be represented by two lines (Figure b) and c)).

The power flows in the original line can be obtained as a result of superposition (summing) of the flows in these lines. Power flows in a line with equal voltages at the ends (U n.) Figure b) are determined by the well-known expressions:

Where

Where

In the line in Figure c) in the direction from a power source with a higher voltage to a source with a lower voltage, a through equalizing current I level flows. and equalizing power S ur.

Accordingly, as a result of the position of the flows determined by formulas (1), (2) and (3), the power flows in the line with double-sided supply are determined in Figure a)

Determination of power losses DS kj is carried out according to the formula:

where k is the node of the beginning of the line section;

j – node of the end of the line section;

Then the voltages are determined.

Let's say the flow separation point is point 3, Figure 2). Let's cut the line at node 3, Figure. d)

Now you can determine the voltage or voltage drop
(DU nb) in two open-loop networks, i.e. in lines 1–3 and 4–3 1 because U 1 > U 4, then DU 1-3 > DU 4-3 and DU nb = DU 1-3

a)

Post-emergency conditions

B. The most severe are the failure and shutdown of sections 1-2 and 3-4 (closest to the power source). Let's analyze these modes and determine the greatest voltage loss DU nb in the mode when section 4-3 figure e) is turned off. Let's denote the greatest voltage loss DU 1-3 av.

The classification of electrical substations and switchgears is based on the terms and definitions established by the relevant GOSTs and regulatory and technical documentation. The main, most frequently used terms and definitions include the following: electrical substation - an electrical installation designed for receiving, converting and distributing electrical energy, consisting of transformers or other electrical energy converters, control devices, distribution and auxiliary devices in accordance with GOST 19431-84 (GOST 24291-90). Substations with transformers that convert electrical energy only by voltage are called transformer stations; and those that convert electricity by voltage and other parameters (frequency change, current rectification) are called converters. Two or more, usually three-phase, transformers can be installed on a substation. The installation of more than two transformers is accepted on the basis of technical and economic calculations, as well as in cases where two medium voltages are used at the substation. In the absence of a three-phase transformer of the required power, as well as due to transport restrictions, it is possible to use a group of single-phase transformers. A substation, as a rule, consists of several switchgear of different voltage levels, interconnected by a transformer (autotransformer) connection; attached substation (RU) - substation (switchgear) directly adjacent to the main building of a power plant or industrial enterprise (PUE, clause 4.2.7); built-in substation (RU) - substation (switchgear) occupying part of the building (PUE, clause 4.2.8); intra-shop substation (RU) - a substation (switchgear) located openly inside the workshop (without fencing), behind a mesh fence, in a separate room (PUE, clause 4.2.9); auxiliary building (APB) - a building consisting of premises necessary for organizing and carrying out work on maintenance and repair of substation equipment (PUE, clause 4.2.16); transformer substation (TS) - an electrical substation designed to convert electrical energy of one voltage into energy of another voltage using transformers (GOST 24291-90). Consumer TPs are divided into complete, closed, mast and pole; complete transformer substation (KTP) - a substation consisting of transformers, units (switchgear switchgear and switchgear switchgear) and other elements supplied assembled or fully prepared at the manufacturer for assembly (PUE, clause 4.2.10). In a package transformer substation, all high-voltage and low-voltage equipment is installed at the factory, and the substation arrives at the site in finished form, that is, as a kit. Complete transformer substations for indoor (KTP) and outdoor (KTPN) installations are produced with one or two transformers with a capacity of 250 to 2,500 kVA (in KTP) and up to 1000 kVA (in KTPN) at a voltage of 6-10 kV; from 630 to 16,000 kVA (in KTPN) at a voltage of 35 kV. These substations are equipped with protective switching equipment, measuring, signaling and electricity metering instruments and consist of a high voltage input unit, power transformer and switchgear 0.4 kV. PTS come in dead-end and walk-through types, as well as various modifications, including: kiosk, cabinet and other types. Dead-end type PTS are used for power supply settlements and agricultural consumers. Kiosk-type transformer substations (block-type) are used as dead-end transformer substations with a capacity of 250 kVA and higher with equipment serviced from the ground. Such PS are convenient and safe to maintain; mast transformer substation (MTP) - an open transformer substation, all the equipment of which is installed on a structure (including on two or more overhead line support posts) with a service platform at a height that does not require fencing of the substation (PUE, clause 4.2.11). MTP is constructed on A-, P- or AP-shaped or single-column structures made of reinforced concrete or wooden racks. All substation equipment is mounted on the A-shaped structure: disconnector, fuses, arresters, a single-phase transformer with a power of more than 10 kVA and a 0.23-0.4 kV distribution board. The substation does not have a service platform and stairs. U-shaped structures are used for substations with three-phase transformers with a power of up to 250 kVA inclusive. The transformer is located on the site at a height from the ground of at least 3.5 m. AP-shaped structures are used for substations with transformers with a power of up to 400 kVA. All equipment is mounted on them, including the disconnector. To service the MTP, a platform with railings must be installed at a height of at least 3 m. To climb the MTP, it is recommended to use ladders with a device that prohibits climbing them when the switching device is turned on; pole-mounted transformer substation (STP) - an open transformer substation, all the equipment of which is installed on a single-column overhead line support at a height that does not require fencing (PUE, clause 4.2.11). Structurally, the PS consists of individual elements, which, when assembled on site, are mounted into a single complex; distribution point (DP) - 6-500 kV switchgear with equipment to control its operation, not part of the substation (PUE, clause 4.2.12); sectioning point - a point intended for sectioning (by automatic or manual control) a section of 6-20 kV lines (PUE, clause 4.2.13); chamber - a room intended for the installation of devices, transformers and buses. A closed cell is a cell that is closed on all sides and has solid (not mesh) doors. Fenced chamber - a chamber that has openings protected completely or partially by non-continuous (mesh or mixed) fences (PUE, clause 4.2.14). The prefabricated one-way service chamber (KSO) is a type of switchgear, manufactured according to standard schemes, has many modifications, is installed only in special electrical rooms and is maintained by trained personnel; busbar system - a device that is a system of conductors, consisting of busbars installed on supports made of insulating material, running in channels, boxes or similar shells (GOST 22789-94); section (busbar system) - part of the busbar system, separated from its other part by a switching device (GOST 24291-90); current conductor - a device made in the form of buses or wires with insulators and supporting structures, intended for the transmission and distribution of electrical energy within a power plant, substation or workshop (PTEEP, terms); cell (PS, RU) - part of the PS (RU) containing all or part of the switching and (or) other equipment of one connection (GOST 24291-90); switchgear (RU) - an electrical installation for receiving and distributing electrical energy at one voltage, containing switching devices and busbars connecting them (bus sections), control and protection devices (GOST 24291-90). As a 6-10 kV switchgear, a high voltage assembly with single-pole disconnectors and a vertical arrangement of phases of one connection and one KSO chamber with a load switch and fuses for connecting a transformer are used. For 0.4 kV switchgear, low voltage assemblies with fuses and a vertical arrangement of phases of one connection are used. At substations, open (ORU), closed (ZRU) or complete (KRU) switchgears are used. An open switchgear (OSD) is an electrical switchgear whose equipment is located in the open air (GOST 24291-90). An enclosed switchgear (SGD) is an electrical device whose equipment is located indoors (GOST 24291-90). Closed substations and switchgears can be located either in separate buildings or be built-in or attached. In general, PS and RU are integral part electrical installations, which differ: by purpose - generating, converter-distribution and consumer. Generating electrical installations are used to generate electricity, conversion and distribution electrical installations convert electricity into a form convenient for transmission and consumption, transmit it and distribute it among consumers; by type of current - direct or alternating current; in terms of voltage - up to 1000 V or above 1000 V. The rated voltage scale is limited to a relatively small number of standard values, due to which a small number of standard sizes of machines and equipment are manufactured, and electrical networks are made more economical. In three-phase current installations, the rated voltage is usually considered to be the voltage between phases (phase-to-phase voltage). According to GOST 29322-92, the following scale of rated voltages is established: for AC power networks with a frequency of 50 Hz, the phase-to-phase voltage should be: 12, 24, 36, 42, 127, 220, 380 V; 3, 6, 10, 20, 35, 110, 150, 220, 330, 500, 750 and 1150 kV; for electrical networks direct current: 12, 24, 36, 48, 60, 110, 220, 440, 660, 825, 3000 V and above. According to the method of connection to the power grid, substations are divided into dead-end (block), branch (block), through (transit) and hub. Dead-end substations receive power from one or two dead-end overhead lines. Branch substations are connected by a branch to one or two passing overhead lines with one-way or two-way power supply. Passing substations are included in the cutting of one or two passing overhead lines with one-way or two-way power supply. Nodal substations, in addition to supply ones, have outgoing radial or transit overhead lines. According to the control method, substations can be: only with telesignaling; remote-controlled with tele-alarm; with telesignaling and control from a general substation control point (SCU). Substations are promptly serviced by permanent personnel on duty at the control panel, on duty at home or by operational mobile teams (OVB). Substation repairs are carried out by specialized mobile centralized repair teams or local substation personnel. In switchgear with voltages up to 1000 V, wires, buses, devices, devices and structures are selected both according to normal operating conditions (voltage and current), and according to the thermal and dynamic effects of short circuit currents (SC) or maximum permissible switched power. In switchgear and substation voltages above 1000 V, the distances between electrical equipment, devices, live parts, insulators, fences and structures are installed so that during normal operation of the electrical installation physical phenomena(heating temperature, electric arc, gas emission, sparking, etc.) could not lead to equipment damage and short circuit. In networks with a voltage of 6-10 kV, distribution points (DP) are widely used, which are an electrical switchgear, not part of the substation (GOST 242910-90), and intended for the distribution of electrical energy within the distribution network. The distribution center consists of busbars divided into sections, a certain number of cells (connections) and a control corridor. The cells are used to house switching and protective equipment: switches, current transformers (CTs) and voltage transformers (VTs), disconnectors, fuses, and protection devices. The RP control corridor is a room in which drives for switches and disconnectors are installed; A service corridor is a corridor along the switchgear chambers or cabinets, intended for servicing devices and buses. Busbars are current-carrying elements located in a metal shell, serving to connect the main circuits of the components of the package transformer substation in accordance with electrical diagram connections and design of the package substation (GOST 14695-80). 6-10 kV switchgears have two sections in the distribution center, fed by single or double cable lines with a cross-section from 185 to 240 mm 2 from different sections of the 6-10 kV switchgear of one (from 35-110 kV substation) or from different power centers. The sectional switch in the RP is provided with a double-sided device automatic switching on reserve (ATS), which is performed on the 0.4 kV side on contactors with a rated current from 600 to 1000 A. Depending on their location, ATS devices can be local (within one substation, for example, an ATS on a sectional switch), or close to it , or network (at various points of the network), which, when triggered, ensure restoration of power to network sections near the substation. A distribution transformer substation (DTS) is an electrical installation in which the DP and TP are combined. The RTP can accommodate transformers with a unit power of up to 1000 kVA inclusive, switchgear 6-10 kV with a certain amount cells and a complete distribution board 0.4 kV. Therefore, the RTP makes it possible to distribute electricity not only at a voltage of 0.4 kV, like a conventional TP, but also at a voltage of 6-10 kV, like in a RP. Thus, the RTP, unlike the RP, serves not only to receive and distribute electricity, but also to transform it. As a rule, several transformer substations are powered from the RTP. It is advisable to use RTP for power supply to cities and large agricultural complexes (livestock farms, poultry farms, etc.). RTPs are usually performed in a closed type. The power center (CP) is a generator voltage switchgear of power plants or a secondary voltage switchgear of a step-down substation of the power system, to which the distribution networks of a given area are connected (GOST 13109-97). These are mainly substations of 35-220 kV power systems, from which 6-10 kV distribution networks receive power. From the CPU to the distribution network, electricity is transmitted directly to the TP buses or through the RP buses. The totality of the above electrical equipment, together with the structures and premises in which they are installed, is defined by the general term - electrical installation. An electrical installation is any combination of interconnected electrical equipment within a given space or room (GOST 30331.1-95, GOST R 50571.1-93). Electrical installations and associated structures must be resistant to exposure environment or protected from this influence. Open or outdoor electrical installations are electrical installations that are not protected by the building from atmospheric influences. Electrical installations protected only by canopies, mesh fences, etc. are considered external installations (PUE). Closed or internal electrical installations - electrical installations located inside a building that protects them from atmospheric influences (PUE). Electrical rooms, that is, rooms or fenced off (for example, with nets) parts of the room in which electrical equipment is located, accessible only to qualified service personnel, according to the influence of the environment in accordance with the classification according to the PUE, are divided into the following types: dry - rooms in which relative humidity air does not exceed 60%; wet - rooms in which the relative air humidity is more than 60%, but does not exceed 75%; damp - rooms in which the relative air humidity exceeds 75%; especially damp - rooms in which the relative air humidity is close to 100% (ceiling, walls, floor and objects in the room are covered with moisture); hot - rooms in which, under the influence of various thermal radiation, the temperature constantly or periodically (more than 1 day) exceeds +35 °C (for example, rooms with dryers, kilns, boiler rooms); dusty - premises in which, due to production conditions, process dust is released; it can settle on live parts, penetrate inside machines and devices, etc. Dusty rooms are divided into rooms with conductive dust and rooms with non-conductive dust; rooms with a chemically active or organic environment - rooms in which aggressive vapors, gases, liquids are constantly or for a long time contained, deposits or mold are formed that destroy the insulation and live parts of electrical equipment. With regard to the danger of electric shock to people, the following are distinguished: premises without increased danger - premises in which there are no conditions that create increased or special danger; premises with increased danger - premises characterized by the presence of one of the following conditions creating an increased danger: dampness or conductive dust; conductive floors (metal, earthen, reinforced concrete, brick, etc.); heat; the possibility of simultaneous human contact with metal structures of the building connected to the ground, technological devices, mechanisms, etc. etc., on the one hand, and to metal housings of electrical equipment (exposed conductive parts), on the other hand; especially dangerous premises - premises characterized by the presence of one of the following conditions that create a special danger: special dampness; chemically active or organic environment; two or more high-risk conditions at the same time. In terms of the danger of electric shock to people, the territory of open electrical installations is equated to especially dangerous premises.

Surely each of us has noticed booths in the courtyards of residential buildings with many electrical wires coming from them. Such a small building is called a complex word at first glance - an electrical transformer substation.

Many people still don’t know what this building is and what it is used for. We will talk about this in this article.

As you know, the main advantage of electricity over other types of energy is the ability to transmit it over long distances with low losses. However, small losses are still inevitable, since the wires have their own resistance and heat up as a result of transmission through them electric current.

In order to reduce transmission losses to a minimum, it is necessary to transmit current at high voltage, because In this case, the current strength can be reduced, as a result of which the heating of the wires will significantly decrease, resulting in a reduction in current loss. The principle is quite simple - the longer the power transmission line (PTL), the more voltage is used on it.

Electric current generators in power plants produce low current for efficient transmission of voltage over long distances, so they use transformers increasing type.

After the current is delivered to the consumer via the power line, in order to use it for domestic purposes, the voltage must again be reduced to 500, 380 or 220 volts, which we have in the home in the outlet. Transformer substations are used for this purpose. downward type.

It is the step-down substations that are those structures that stand in most courtyards of residential buildings. Receiving high voltage current, they convert it into 220-volt, which is used to power most household electrical appliances.

Speaking in simple language, a step-down transformer substation consists of the following main parts.

• Introductory part - receiving high voltage current.
• Transformer - current conversion.
• The output part is the low voltage current output.

In addition to being divided into step-up and step-down, transformer substations are usually divided into block-type and container-type substations. The first differ from the second only in their housing - a block electrical substation is installed in a concrete room and assembled on site - that is, it is stationary. Container-type substations use a metal structure as a housing, and they are assembled and equipped at the manufacturing plant. Such substations are transportable and can be moved from one place to another without any problems.

If you are interested in the prices for these units, you can familiarize yourself with them, for example, in the company catalog http://www.ru.all.biz/. There are various companies involved in the production and sale of transformer substations.