1.2.17
The categories of power receivers in terms of power supply reliability are determined in the process of designing the power supply system on the basis of regulatory documentation, as well as the technological part of the project.
1.2.18
With regard to ensuring the reliability of power supply, power receivers are divided into the following three categories.
If a substation has a power supply as its main purpose, the main need for that substation is reliability. Substations can be classified according to the main criteria that cover the types that exist in our environment. For its function in the power system. by type of operation. in its constructive form. Classification of substations according to their function in the system.
Generator Substation: This is the primary station for the energy produced by generating plants, its main task is to convert voltage into high levels to obtain savings with decreasing current. Broadcasting Substation: Its function is to connect various 115KV or 220KV power lines.
Power receivers of the first category - power receivers, the interruption of power supply of which can lead to a danger to people's lives, a threat to the security of the state, significant material damage, a disorder of a complex technological process, disruption of the functioning of especially important elements of public utilities, communication and television facilities.
Sub-transit substation: These are those that feed or connect lines of intermediate voltage level, 44 kV or 5 kV, for transportation over moderate distances and not very high loads with loads distributed along the line. Distribution Substation: Its function is to reduce the voltage to distribution levels of 2 kV to be sent to industrial or residential consumption centers where distribution transformers installed along the circuits are responsible for reducing low voltage levels, for users.
Classification of substations by type of operation. Transformer Substation: These are stations that convert the voltage in the power system into values suitable for transport or use. According to the transformation function that they perform in the power system, they are divided into.
From the composition of power receivers of the first category, a special group of power receivers stands out, the uninterrupted operation of which is necessary for an accident-free shutdown of production in order to prevent a threat to human life, explosions and fires.
Electrical receivers of the second category are electrical receivers, the interruption of power supply of which leads to massive undersupply of products, massive downtime of workers, mechanisms and industrial transport, disruption of the normal activities of a significant number of urban and rural residents.
Transformer substation: output voltage different from the input voltage; they are those that allow voltage levels to be raised or lowered from generation points, through the highest levels of transmission, to the lowest levels of sub-transport or distribution.
Flexible substation: its function is to combine some transmission lines with other distribution lines in order to ensure greater reliability and continuity of service; There is only one voltage level, so power transformers that step up or step down the voltage are not used.
Power receivers of the third category - all other power receivers that do not fall under the definitions of the first and second categories.
1.2.19
Power receivers of the first category in normal modes must be supplied with electricity from two independent mutually redundant power sources, and a break in their power supply in the event of a power failure from one of the power sources can only be allowed for the period of automatic power restoration.
Classification of substations according to their constructive way. Indoor substations: where its constituent elements are installed inside the respective buildings. Figure 2 Indoor substation. Outdoor or outdoor substations: its constituent elements are installed in ambient conditions. Ordinary substation: it has appearance but your hardware installation is open without protecting them. Encapsulated Substation: This is a substation whose living parts and voltage maintaining equipment are contained in metal cases. Mobile substation: it is characterized by the fact that the whole set of equipment is installed on a trailer.
For the power supply of a special group of power receivers of the first category, additional power must be provided from a third independent mutually redundant power source.
As a third independent power source for a special group of power receivers and as a second independent power source for other power receivers of the first category, local power plants, power plants of power systems (in particular, generator voltage buses), units designed for these purposes can be used. uninterruptible power supply, rechargeable batteries, etc.
Voltage levels and regulation, reactive power compensation
Its main purpose is to be used in emergency situations anywhere in the system. The layout, characteristics and quantity of equipment for each substation directly depend on the chosen configuration. Therefore, the general and essential description will apply to any configuration.
These are conventional type substations that will be taken as the basis, since this is the most common type of substation in Colombia. In addition to structures and supports that facilitate the arrival and departure of lines, a set called "substation basic elements". These elements are divided into 3 categories as follows.
If it is impossible to ensure the continuity of the technological process by redundant power supply, or if redundant power supply is not economically feasible, technological redundancy should be carried out, for example, by installing mutually redundant technological units, special devices for trouble-free shutdown of the technological process, operating in the event of a power failure.
Patio equipment Tabletop equipment Ancillary services. . Patio Equipment: These are the constituent elements of the power system, which are installed in the internal space of the joints, usually in an open state, exposed to environmental conditions.
Mosenergosbyt submits a note to turn on, moesk supplies voltage
The space occupied by a set of equipment belonging to the same substation output is called "Field" or "Bay", for example, "Field Field", "Transformer Bay", etc. Panel equipment: all control, measurement and protection elements, indicator lights and alarms installed in the control house and supported by substations. Its function is to facilitate the control and management of the substation by the operator.
Power supply of power receivers of the first category with a particularly complex continuous technological process that requires a long time to restore the normal mode, in the presence of feasibility studies, it is recommended to carry out from two independent mutually redundant power sources, to which additional requirements are imposed, determined by the characteristics of the technological process.
The parts of the auxiliary system are as follows. Control cabinet protective screen shielding system. . Although the efficiency of transformers is usually high, the losses that occur in them are an important part of the system losses. Therefore, the maximum possible reduction of such losses should be achieved while minimizing operating costs.
Depending on the number of transformers installed in substations, the way the load is distributed, and how they operate when they are in parallel with different load conditions, more efficiency can be achieved in the delivery system.
1.2.20
Power receivers of the second category in normal modes must be provided with electricity from two independent mutually redundant power sources.
For power receivers of the second category, in the event of a power failure from one of the power sources, power supply interruptions are permissible for the time necessary to turn on the backup power by the actions of the duty personnel or the mobile operational team.
Determination of the number of transformers. It is always preferable to choose one transformer instead of two or more to suit a given load level, unless special conditions are imposed on the system. Reserve power is provided from a neighboring substation. This is due to the fact that, in general, the installation of one transformer guarantees minimal costs. If the consumer's standby power requirements require the installation of more than one transformer, try not to exceed two.
The reliability of power supply to consumers is related to the number of power sources, the power circuit and the category of receivers. Receivers of electrical energy can be divided into three categories. First category: receivers in which the interruption of the power supply can endanger human life or significant material damage due to deterioration of installations, mass defective production or long-term disruption of the technological production process.
1.2.21
For power receivers of the third category, power supply can be carried out from one power source, provided that power supply interruptions necessary to repair or replace a damaged element of the power supply system do not exceed 1 day.
There is a PUE (rules for the installation of electrical installations), where you can determine the classification of electrical consumers and get acquainted with their conditional division in terms of reliability. If we consider a multi-storey building and a hospital, then the reliability of the second should be higher. Since resuscitation and operating rooms are connected to the power supply here, therefore, an emergency shutdown can lead to the loss of human life or its threat.
Reliability category change
Third category: receivers not included in the above categories, which are not decisive in the fundamental process of production or services. Consumers of the first category must have power from two independent sources that can provide food reservations for other consumers. When uninterrupted service is guaranteed from two substations, one transformer can be installed in each of them. When this is done from a single substation, it is necessary to have at least one transformer in each section of the rods.
If we consider a chemical enterprise, then a power outage will result in an explosion, casualties and material damage, hence this facility is important and requires a reliable power supply.
All objects are carefully studied, and they are assigned categories of reliability.
- First. This group is also called very important. Since here the lack of power leads to irreversible processes, and, most importantly, creates a danger to human life, the state, and an emergency situation can be created that will result in great material damage. Therefore, an uninterruptible power supply from two independent sources is turned on here, when automatic switching from one bus to another is carried out in a matter of fractions of a second. Also in the first group, in order to increase reliability, a third source is provided, for example, batteries, autonomous mini-power plants, etc. This source is intended for a special group. They can also feed the second energy carrier.
- Second. An emergency power off can lead to mass marriage, disruption of the technical process, and people's livelihoods. It also uses two independent and interchangeable sources. This group is used by a significant number of electrical consumers.
- Third. Those consumers that are not included in the first two categories belong to group 3. It uses one source of power supply, only a prerequisite is to stop the power supply for no more than one day. The source can be one transformer transformer substation and 72 hours of outages are allowed in one year.
Power supply requirements
In this case, the power of the transformers must be chosen in such a way that, if one of them fails, the other provides the supply of first class consumers, taking into account the permissible overload capacity of these transformers. The use of reserve power for first-class consumers should be automatic.
In unitary substations with two transformers, it is convenient to keep sections of low-voltage rods in independent operation. When one of the transformers is disconnected, the other takes on the load as a result of the connection of an automatic sectionalizer. Supply to consumers of the second category must be ensured by automatic reservation or manually by service personnel. When supplied from a substation, two transformers or a backup transformer must be provided for several substations supplying second class consumers, so that replacement of a defective transformer can occur within a few hours.
Electrical receivers of each category, according to the installation rules, have certain requirements.
- In the 1st group of electrical receivers power must be connected from independent power supplies. And if we are talking about a special group of receivers, then a third independent mutually redundant electrical unit is additionally provided. Thus, an uninterrupted and reliable power supply is ensured. Since power failures can lead to human casualties, property damage, violation of the technical process, TV failure, etc.
- In the second group of electrical receivers also comes from two independent sources. The only difference is that here a certain amount of time is allowed for connection backup source, while in the first category, switching is carried out automatically. Backup power can be connected by a mobile operational team or duty personnel. A power interruption in this group can lead to downtime for workers and electrical equipment, and stop production.
- In power receivers of the third group food is provided by one source and the break in food cannot be more than 24 hours.
Reliability categories of building/facility power supply
Power supply requirements
During this time, power limits may be introduced, taking into account the overload capabilities of the transformers that remain in service. Depending on the importance of production or services, a decision may be made to have a single source of energy. Third-party receivers typically only have one power supply.
Similar to the definition of efficiency in other machines, transformers are defined by the ratio between output power and input power. Losses in transformers can be classified as no-load, no-load and no-load losses. Vacuum losses are mostly hysteresis and parasitic in the core of the transformer, and for practical purposes can be considered constant and independent of the state of charge.
- A residential building, where there is a presence of electric stoves, belongs to group 2.
- The house in which there are 8 apartments and electric stoves is the 3rd group.
- Garden plots - 3.
- A room with fire fighting equipment - 1.
- Hostel where more than 50 people live - 2. Less than 50-3.
- Individual heating point and central heating point - 1.
- Buildings where more than 2 thousand people work - 1.
- High-rise buildings over 16 floors - 1.
- Sanatorium buildings and rest houses - 1.
- State insurance and financial institutions with security alarms and fire-fighting devices - 1.
- Libraries with security equipment - 1.
- Libraries where one thousand copies of books are stored - 2.
- Preservation of copies of books up to 100 units - 3.
- Preschool and school institutions with security equipment - 1.
- Hotels with security and fire-fighting equipment - 1.
- Canteens, cafes and other places for eating - 1.
- Consumer service buildings (hairdressing salons with more than 15 people, ateliers with 50 people and dry cleaners with a capacity of 500 kg) - 2.
- Museums of federal, regional and republican significance - 1.
- Medical buildings with intensive care, an operating room, a ward for premature babies - 1.
- Temporary objects - 3.
A building that has a 3rd group and is powered by one line, security and fire equipment should be connected to autonomous sources.
Standby power supplies for household consumers
The load losses are the sum of the copper losses in the high and low voltage windings, plus a group of smaller losses that are grouped as additional losses. The latter can be ignored for the purposes of this article. Since the charge of the transformer is proportional to the current, the loss of copper. proportional to the square of the load.
Thus, there will be total losses. Although three or more transformers may be installed in a substation, as previously stated, it is recommended that the number not exceed two, which is why this condition is chosen. When there is a substation with two transformers, it can be operated more economically when the number of them connected at any given time creates the minimum loss for a given load profile. For this, not only the active power losses in the transformers themselves, but also the active power losses that appear in the system, due to the reactive power requirements of the transformers.
Power consumers and lighting are connected from transformers.
Transformer substations are used for public buildings built-in or attached.
A residential building can be powered from attached substations only if they are filled with a liquid dielectric.
The use of TP in a residential building and a school institution is prohibited.
Introducing this problem, the analysis of losses during the circulation of the reagent in the system is omitted. The total transformer losses expressed in the equation follow the parabola equation. From the above analysis, it is explained that the parabolas corresponding to parallel transformers have a less pronounced slope, and the interception with the y-axis occurs in more high point compared to the behavior of parabolas of independent transformers. The same analysis is valid for a transformer.
The operating mode to obtain the most economical operation has the disadvantage of controlling the transformer switches. This aspect is the limit of this practice and should be carefully considered as these switches are expensive and require maintenance for a certain number of operations. Only in the case of a favorable technical and economic effect, this procedure can be successfully applied.
TP should be placed in such a way that there is a possibility of round-the-clock access for organizations and personnel involved in maintenance.
Schemes (description)
A prerequisite for the receivers of the first group are independent power sources. And in the event of a power failure, it is automatically restored from backup power supply. Electricity of independent sources is carried out from different substations or from one. In this case, certain conditions must be met:
- Buses or sections are connected from independent sources;
- There should be no connection between busbars or sections. Shutdown occurs automatically in an emergency.
Batteries, uninterruptible power supplies, local power plants can serve as a backup power source.
Fig.1
Figure 1 shows a radial diagram of category 1 consumers. During an emergency power outage on one of the sections, the circuit breaker on the bus will automatically close.
Fig.2
The second scheme in Fig. 2 displays consumers of the 2nd category. Can also be used for 1 group.
An emergency power off on one of the sections will not prevent the continuation of the second section.
Fig.3
Figure 3 shows a diagram of category 3 consumers. Using an emergency source, the scheme can be used for category 1 consumers.
Who determines and how
The criteria for choosing categories in the power supply are the number of people. First of all, their safety and the level of material damage are considered if a power outage occurs. For such purposes, the designers developed a classifier various kinds power supply. It indicates the types of buildings, objects, you just need to select the desired building with a certain category.
In industrial buildings, to determine the desired power supply group, technologists are involved and the document SP 31–110–2003 and PUE (rules for electrical installations) are used.
It all depends on the danger and possible material damage. The lower it is, therefore, the category will be lower and vice versa. For example, an object associated with a fire is always assigned the first category.
