Uninterrupted power supply- this is the absence of undersupply of energy and power to the consumer. Compliance with this requirement guarantees the consumer required amount electrical energy and power. The system must have enough capacity of stations, networks must transmit the necessary energy, there must be an appropriate supply of fuel. Continuity will whistle from the whole range of capabilities of system objects. During the development of the system and during its operation, such system parameters are determined that ensure uninterrupted power supply.
Reliability is a guarantee of continuity.
From the point of view of ensuring reliable and uninterrupted power, power receivers are divided into three categories (PUE 1.2.17-1.2.20):
Electrical receivers 1 category- these are ES, the interruption of the power supply of which can lead to a danger to people's lives, a threat to the security of the state, significant material damage, disruption of a complex technological process, disruption of the functioning of especially important elements of public utilities, communications and television.
These are such electrical consumers as large metallurgical plants, chemical enterprises with a continuous production cycle, livestock farms, hospitals, water supply, sewerage. The question of the reliability of power supply to consumers is associated with the number of independent power sources, the power supply scheme and the category of consumers. Receivers of the 1st category must have at least two independent power sources with ATS no more than 1 s. (two-transformer substation; power system and plant CHP), power supply via single-circuit lines.
Two or more power sources are called independent if the violation of the regime or damage to one of them does not entail the failure of the other.
From the composition of electrical receivers of the 1st category stands out special group electrical receivers, 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.
These are, for example, circulation pumps in nuclear reactors, control systems at petrochemical enterprises. For a special group, a third independent IP (diesel generator, battery) should be provided. If it is not possible to achieve absolute safety with reserves, technological redundancy is used, devices for emergency shutdown of production.
Electrical receivers 2 categories- electrical receivers, the interruption in the power supply of which leads to a massive undersupply of products, massive downtime of workers, mechanisms and industrial transport, disruption of the normal life of a significant number of urban and rural residents.
In category 2 power supply, power supply can be interrupted from 3 hours to a day and must be through two independent inputs, but the reserve can be turned on manually. These are, for example, engineering plants, houses with electric stoves. Receivers of the 2nd category can have one or two independent power sources (it is decided specifically depending on the importance that this industrial enterprise has in the country's economy and local conditions). The power supply of electrical receivers of this category is allowed through one overhead line, or through one CL with two or more cables, or through one transformer, if it is possible to carry out emergency repairs in it or replace a damaged transformer from a centralized reserve for no more than 1 day.
Electrical receivers 3 categories- these are EPs that do not fall under the definition of categories 1 and 2. For example, receivers of auxiliary workshops that do not determine the technological process of the main production.
Power supply of category 3 ES can be carried out from one power source if the repair or replacement of damaged equipment does not exceed 1 day. But if, according to local conditions, it is possible to provide power without significant costs from a second source, then power redundancy is also applied to this category of receivers.
The reliability of power supply is ensured by the creation of an appropriate circuit (circuit reliability), the use of appropriate units, switching devices, transformers (hardware reliability). It is achieved by designing equipment and its proper operation. Reliability is also associated with modes (mode reliability), which requires the choice of reasonable decisions on the use of equipment, stations and systems, ensuring system stability, etc.
Reliability and continuity come at a cost. The higher these requirements, the more funds must be invested in the appropriate equipment.
The most significant reduction in reliability occurs as a result of system failures, which can be very severe. However, the probability of such accidents is low, and it is not economically justified to provide over high level reliability in these rare cases. It is better to allow a break in the power supply. It is important that the consumer knows what level of reliability he is guaranteed. If the consumer requires an individually high level of reliability, then you have to pay for it.
There are two fundamental approaches to assessing the reliability of power supply systems. The first one relies on regulations(PUE, GOST), in which all electrical receivers are divided into three categories. The implementation of this approach in the formation of SES formally presents no difficulties. However, as a rule, consumers belonging to different categories are connected to network nodes. At the same time, if we focus on the least responsible consumers (choose the simplest and cheapest scheme), then the most responsible consumers will not be provided with the required level of reliability. If, when choosing a scheme, to focus on them, then this can lead to unjustified complication and an increase in the cost of the SES scheme. It should also be noted that the requirements of the PUE were formulated in relation to a centralized economy, based on global economic interests. Of course, in market economic conditions, these requirements should be maintained, at least in cases of interruption of power supply, which lead to danger to life, explosions, fires and, possibly, other adverse consequences.
The second approach involves an economic (quantitative) assessment of the undersupply of electricity - economic damage due to undersupply of electricity. It is recommended to use it primarily in cases where the compared options for SES schemes differ significantly in power supply reliability, as well as to evaluate measures aimed at improving reliability. The disadvantage of this approach lies in the ambiguity (inaccuracy) of the numerical values of specific damages from undersupply of electricity to consumers.
In market conditions, the economic interests of individual organizations come to the fore: electricity supply (electricity supplier) and electricity consumer. With regard to the power supply organization, economic damage will manifest itself due to a shortfall in profit due to undersupply of electricity due to interruptions in power supply, penalties for consumers for undersupply of electricity, additional costs for emergency repairs of damaged network elements, etc. Also in industrialized countries with market economies, it is considered acceptable assessment of the economic damage caused to society by power outages.
Typically, a reasonable level of reliability is selected in the power system, depending on the requirements of the consumer. They are determined during a design accident, for which reliability standards are established, for example, for the stability of power systems. It is believed that electric power elements and the system should provide a reliability level of 0.9 - 0.99 during operation. For consumers of a special group of category 1, the level of reliability is 0.999. But it is well known that accidents are possible even at such a calculated level (Chernobyl NPP). Technology can never be absolutely reliable. When determining the level of reliability, the safety of equipment, especially expensive ones, is guaranteed.
Of course, there are cases when super-heavy accidents occur in the power system and then all reliability guarantees are violated. But it is not economically feasible to protect consumers completely from such accidents. Although after such severe accidents, certain measures to improve reliability should be taken.
To ensure reliability, there are reserves: when transmitting energy through power lines, when choosing transformer power, switching devices, and station capacities. The EPS always has an emergency power reserve. The maintenance of the reserve requires certain costs both during the creation of the system and during its operation. Obviously, the costs depend on the category of consumers in terms of reliability and, accordingly, should be taken into account in the electricity tariff.
For the normal operation of an industrial enterprise, in addition to power supply reliability, it is important to maintain voltage and frequency stability.
The power supply system is a set of devices used to receive, transmit and distribute electrical energy. It is designed to supply electricity consumers of enterprises, which include electric motors of various production mechanisms and units, electric furnaces, electric welding installations, lighting and electrolysis installations, etc.
The power supply system of manufacturing enterprises should ensure uninterrupted supply of electricity to consumers, reliability, high quality electricity, the safety of electrical installations for the life and health of service personnel.
There are consumers of electricity who do not allow a break in the power supply. In particular, they include chemical and metallurgical enterprises. Here, a break in the power supply can lead to the failure of expensive equipment; in chemical plants, it can cause an explosion. In other cases, a break in the power supply entails a danger to the life of the maintenance personnel (for example, stopping the ventilation of mine workings due to a lack of electricity can lead to gas poisoning of people).
There may be other consequences caused by a power outage. Breaks in power supply are especially dangerous for industries with complex technological process when the shutdown of the equipment is accompanied by a significant undersupply to consumers of products of great importance.
Today's major cities, with their complex transportation and housing infrastructures, are also highly sensitive to power outages. As an example, it suffices to cite the case of a power outage in New York that took place in the summer of 1965. As a result, the complex urban economy was put out of action for several days (specialists call this accident the “catastrophe of the century”).
Other consumers are not so sensitive to power interruptions. For them, a power outage does not cause particularly serious consequences.
With this in mind, the rules for the installation of electrical installations (PUE) provide for three categories of consumers of electricity according to the conditions for ensuring uninterrupted power supply:
1st category - consumers of electricity, the disruption of the power supply of which can lead to a danger to people's lives, significant damage to the national economy, damage to equipment, mass defective products, disruption of a complex technological process, disruption of the functions of especially important elements of the urban economy;
2nd category - consumers of electricity, the interruption in the power supply of which is associated with a massive undersupply of products, downtime of workers, mechanisms, process equipment and industrial vehicles, disruption of the normal life of a significant number of people;
3rd category - all other consumers of electricity that do not fit the definitions of consumers of the 1st and 2nd category (for example, consumers of non-serial production workshops, auxiliary workshops, small towns, etc.).
Consumers of electricity of the 1st category must be provided with electricity from two independent power sources, interruption of their power supply can only be allowed for the time of automatic activation of the backup power supply.
With a low power of consumers of electricity of the 1st category, mobile power plants, storage batteries, as well as jumpers at the lowest voltage from the nearest point with independent power supply can be used as a second power source. automatic switching on reserve (AVR).
For consumers of electricity of the 2nd category, interruptions in power supply are allowed for the time necessary to turn on the backup power by the actions of the duty personnel or the mobile operational team.
For electricity consumers of the 3rd category, interruptions in power supply are allowed for the time necessary to repair or replace a damaged element of the power supply system, but for a period not exceeding one day.
1.2.1. This chapter of the Rules applies to all power supply systems.
Power supply systems for underground, traction and other special installations, in addition to the requirements of this chapter, must also comply with the requirements of special rules.
1.2.2. Energy system (energy system) - a set of power plants, electrical and thermal networks, interconnected and connected by a common mode in the continuous process of production, conversion, transmission and distribution of electrical and thermal energy with the general management of this mode.
1.2.3. The electrical part of the power system is a set of electrical installations of power plants and electrical networks power systems.
1.2.4. Electric power system - the electrical part of the power system and receivers of electrical energy powered by it, united by a common process of production, transmission, distribution and consumption of electrical energy.
1.2.5. Power supply - providing consumers with electrical energy.
Power supply system - a set of electrical installations designed to provide consumers with electrical energy.
Centralized power supply - power supply to consumers of electrical energy from the power system.
1.2.6. Electrical network - a set of electrical installations for the transmission and distribution of electrical energy, consisting of substations, switchgears, current conductors, overhead and cable power lines operating in a certain area.
1.2.7. Electrical energy receiver (electric receiver) - an apparatus, unit, etc., designed to convert electrical energy into another type of energy.
1.2.8. Consumer of electrical energy - an electrical receiver or a group of electrical receivers, united by a technological process and located in a certain territory.
1.2.9. The normal mode of the consumer of electrical energy is the mode in which the specified values of the parameters of its operation are provided.
Post-emergency mode - the mode in which the consumer of electrical energy is located as a result of a violation in the system of its power supply before the establishment of a normal mode after the localization of the failure.
1.2.10. An independent power source is a power source that maintains voltage in the post-accident mode within the regulated limits when it disappears on another or other power sources.
Independent power sources include two sections or busbar systems of one or two power plants and substations, while simultaneously meeting the following two conditions:
- each of the sections or busbar systems in turn is powered by an independent power source;
- sections (systems) of tires are not interconnected or have a connection that automatically turns off when one of the sections (systems) of tires fails.
General requirements
1.2.11. When designing power supply systems and reconstructing electrical installations, the following issues should be considered:
- prospects for the development of power systems and power supply systems, taking into account the rational combination of newly constructed electrical networks with existing and newly constructed networks of other voltage classes;
- ensuring a comprehensive centralized power supply to all consumers of electrical energy located in the coverage area of electrical networks, regardless of their affiliation;
- limitation of short-circuit currents by limiting levels determined for the future;
- reduction of electrical energy losses;
- compliance of the decisions made with the conditions of environmental protection.
At the same time, external and internal power supply should be considered in a complex, taking into account the possibilities and economic feasibility of technological redundancy.
When resolving redundancy issues, one should take into account the overload capacity of electrical installation elements, as well as the availability of a reserve in process equipment.
1.2.12. When solving the issues of development of power supply systems, repair, emergency and post-accident modes should be taken into account.
1.2.13. When choosing independent mutually redundant power sources that are objects of the power system, one should take into account the possibility of a simultaneous dependent short-term decrease or complete loss of voltage for the duration of the relay protection and automation in case of damage to the electrical part of the power system, as well as a simultaneous long-term loss of voltage on these power sources in case of heavy system accidents.
1.2.14. Requirements 1.2.11-1.2.13 must be taken into account at all intermediate stages of development of power systems and power supply systems.
1.2.15. The design of electrical networks should be carried out taking into account the type of their service (permanent duty, duty at home, mobile teams, etc.).
1.2.16. The operation of electrical networks with a voltage of 2-35 kV can be provided both with an isolated neutral and with a neutral grounded through an arcing reactor or resistor.
Compensation for the capacitive earth fault current must be applied at the values of this current in normal conditions:
- in networks with a voltage of 3-20 kV, having reinforced concrete and metal supports on overhead power lines, and in all networks with a voltage of 35 kV - more than 10 A;
- in networks that do not have reinforced concrete and metal supports on overhead power lines:
- more than 30 A at a voltage of 3-6 kV;
- more than 20 A at a voltage of 10 kV;
- more than 15 A at a voltage of 15-20 kV;
in generator voltage circuits of 6-20 kV generator-transformer units - more than 5A.
The operation of electrical networks with a voltage of 110 kV can be provided both with a solidly grounded and with an effectively grounded neutral.
Electrical networks with a voltage of 220 kV and above should only work with a solidly grounded neutral.
Categories of electrical receivers and ensuring the reliability of power supply
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. 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, disruption of a complex technological process, disruption of the functioning of especially important elements of public utilities, communications and television.
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 people's lives, 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.
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 provided 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. 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), uninterruptible power units designed for these purposes, batteries and etc. 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. 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.
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.
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.
Voltage levels and regulation, reactive power compensation
1.2.22. For electrical networks, technical measures should be provided to ensure the quality of electrical energy in accordance with the requirements of GOST 13109.
1.2.23. Voltage regulation devices must ensure that the voltage on the buses with a voltage of 3-20 kV of power plants and substations to which distribution networks are connected is not lower than 105% of the nominal during the period of the greatest loads and not higher than 100% of the nominal during the period of the least loads of these networks. Deviations from the specified voltage levels must be justified.
1.2.24. The choice and placement of reactive power compensation devices in electrical networks are based on the need to ensure the required network throughput in normal and post-accident modes while maintaining the required voltage levels and stability margins.
With regard to ensuring the reliability of power supply, power receivers are divided into the following three categories:
Category I power receivers - power receivers, the interruption of power supply of which may entail: danger to human life, significant damage to the national economy; damage to expensive basic equipment, mass defective products, disruption of a complex technological process, disruption of the functioning of especially important elements of public utilities.
From the category I electrical receivers, a special group of electrical receivers is distinguished, the uninterrupted operation of which is necessary for an accident-free shutdown of production in order to prevent a threat to human life, explosions, fires and damage to expensive basic equipment.
Category II electrical receivers are electrical receivers whose power supply interruption 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.
Category III power receivers - all other power receivers that do not fit the definitions of categories I and II.
Category I power receivers 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.
For the power supply of a special group of power receivers of category I, 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 category I, local power plants, power plants of power systems (in particular, generator voltage buses), special uninterruptible power units, batteries, etc. can be used. .
If it is impossible to ensure the necessary 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.
Power supply of power receivers of category I with a particularly complex continuous technological process that requires a long time to restore the operating mode, if there are feasibility studies, it is recommended to carry out from two independent mutually redundant power sources, which are subject to additional requirements determined by the characteristics of the technological process.
Category II electrical receivers are recommended to be supplied with electricity from two independent mutually redundant power sources.
For power receivers of category II, 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.
It is allowed to supply electrical receivers of category II by one BJI, including those with a cable insert, if it is possible to carry out emergency repairs of this line for a period of not more than 1 day. The cable inserts of this line must be made with two cables, each of which is selected according to the highest BJI continuous current. It is allowed to power category II electrical receivers through one cable line, consisting of at least two cables connected to one common device.
In the presence of a centralized reserve of transformers and the possibility of replacing a damaged transformer within a period of not more than 1 day, it is allowed to supply power consumers of category II from one transformer.
For power receivers of category III, 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.
Chapter 1.2. Power supply and electrical networks
(Agreed with Gosstroy of the USSR on August 3, 1976;
approved by the Main Technical Administration and Gosenergonadzor of the USSR Ministry of Energy on July 5, 1977)
GUARANTEE:
Since January 1, 2003, chapter 1.2 of section 1 of the "Electrical Installation Rules" of the sixth edition has become invalid. See chapter 1.2 of section 1 "Power supply and electrical networks" as amended by the seventh edition, approved by order of the Ministry of Energy of the Russian Federation of July 8, 2002 N 204
Scope, definitions
1.2.1. This chapter of the Rules applies to all power supply systems. Power supply systems for underground, traction and other special installations, in addition to the requirements of this chapter, must also comply with the requirements of special rules.
1.2.2. An energy system (energy system) is a set of power plants, electrical and thermal networks interconnected and connected by a common mode in the continuous process of production, conversion and distribution of electrical energy and heat with the general management of this mode.
1.2.3. The electrical part of the power system is a set of electrical installations of power plants and electrical networks of the power system.
1.2.4. The electrical power system is the electrical part of the power system and the receivers of electrical energy powered by it, united by a common process of production, transmission, distribution and consumption of electrical energy.
1.2.5. Power supply is the provision of electrical energy to consumers.
The power supply system is a set of electrical installations designed to provide consumers with electrical energy.
1.2.6. Centralized power supply is the power supply of consumers from the power system.
1.2.7. An electrical network is a set of electrical installations for the transmission and distribution of electrical energy, consisting of substations, switchgears, current conductors, overhead (VL) and cable power lines operating in a certain area.
1.2.8. A receiver of electrical energy (electric receiver) is a device, unit, mechanism designed to convert electrical energy into another form of energy.
1.2.9. A consumer of electrical energy is a power receiver or a group of power receivers, united by a technological process and located in a certain area.
1.2.10. An independent power source of an electrical receiver or a group of electrical receivers is a power source on which voltage is maintained within the limits regulated by these Rules for the post-emergency mode, when it disappears on another or other power sources of these electrical receivers.
Independent power sources include two sections or busbar systems of one or two power plants and substations, while simultaneously meeting the following two conditions:
1) each of the sections or bus systems, in turn, is powered by an independent power source;
2) bus sections (systems) are not interconnected or have a connection that is automatically disconnected when one of the bus sections (systems) malfunctions.
General requirements
1.2.11. When designing power supply systems and reconstructing electrical installations, the following issues should be considered:
1) the prospect of development of energy systems and power supply systems, taking into account the rational combination of newly constructed electrical networks with existing and newly constructed networks of other voltage classes;
2) ensuring a comprehensive centralized power supply to all consumers located in the coverage area of electrical networks, regardless of their departmental affiliation;
3) limitation of short-circuit currents by limiting levels determined for the future;
4) reduction of electrical energy losses.
At the same time, external and internal power supply should be considered in a complex, taking into account the possibilities and economic feasibility of technological redundancy.
When resolving redundancy issues, one should take into account the overload capacity of electrical installation elements, as well as the availability of a reserve in process equipment.
1.2.12. When solving the issues of development of power supply systems, repair, emergency and post-accident modes should be taken into account.
1.2.13. When choosing independent mutually redundant power sources that are objects of the power system, one should take into account the possibility of a simultaneous dependent short-term decrease or complete loss of voltage for the duration of the relay protection and automation in case of damage to the electrical part of the power system, as well as a simultaneous long-term loss of voltage on these power sources in case of heavy system accidents.
