Анотація
В даній статті розглядається радіаційна небезпека. Викладені загальні поняття про радіацію, небезпека радіації для людей; засоби захисту від радіації в сучасних атомних лабораторіях; умови праці з радіоізотопами та їх перевезення.
Стаття розрахована на велике коло читачів, які цікавляться радіацією.
Виконання вправ на закріплення граматичної теми
Вправа 9. Складіть анотацію до тексту.
Thermal power stations
In thermal power stations, mechanical power is produced by a heat engine that transforms thermal energy, often from combustion of a fuel, into rotational energy. Most thermal power stations produce steam, so they are sometimes called steam power stations. Not all thermal energy can be transformed into mechanical power, according to the second law of thermodynamics; therefore, there is always heat lost to the environment. If this loss is employed as useful heat, for industrial processes or district heating, the power plant is referred to as a cogeneration power plant or CHP (combined heat-and-power) plant.
R
otor
of a modern steam turbine, used in power station.
The efficiency of a steam turbine is limited by the maximum steam temperature produced. The efficiency is not directly a function of the fuel used. For the same steam conditions, coal-, nuclear- and gas power plants all have the same theoretical efficiency. Overall, if a system is on constantly (base load) it will be more efficient than one that is used intermittently (peak load). Steam turbines generally operate at higher efficiency when operated at full capacity.
Besides use of reject heat for process or district heating, one way to improve overall efficiency of a power plant is to combine two different thermodynamic cycles. Most commonly, exhaust gases from a gas turbine are used to generate steam for a boiler and a steam turbine. The combination of a "top" cycle and a "bottom" cycle produces higher overall efficiency than either cycle can attain alone.
Заняття 55
Тема: Енергетичні системи, підстанції
Граматичний матеріал: Анотаційний переклад
Вправа 1. Прочитайте та перекладіть слова за допомогою словника.
substation [ə ˈsʌbsteɪʃn̩ ]
consumer [kənˈsjuːmə]
voltage level [ˈvəʊltɪdʒ ˈlevl̩]
electrical utility [ən ɪˈlektrɪkl̩ juːˈtɪlɪti]
supervision [suːpəˈvɪʒn̩]
subsidiary [səbˈsɪdɪəri]
circuit breakers [ˈsɜːkɪt ˈbreɪkəz]
capacitor [kəˈpæsɪtə]
reduce [rɪˈdjuːs]
disjoint [dɪsˈdʒɔɪnt]
distribution substation [dɪstrɪˈbjuːʃn̩ ˈsʌbsteɪʃn̩]
number of feeders [ˈnʌmbər əv ˈfiːdəz]
switching substation[ˈswɪtʃɪŋ ˈsʌbsteɪʃn̩]
collector substation [kəˈlektə ˈsʌbsteɪʃn̩]
Вправа 2. Прочитайте та перекладіть текст українською.
Substations
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Between the generating station and consumer, electric power may flow through several substations at different voltage levels.
Substations may be owned and operated by an electrical utility, or may be owned by a large industrial or commercial customer. Generally substations are unattended, relying on SCADA for remote supervision and control.
A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages. The word substation comes from the days before the distribution system became a grid. As central generation stations became larger, smaller generating plants were converted to distribution stations, receiving their energy supply from a larger plant instead of using their own generators. The first substations were connected to only one power station, where the generators were housed, and were subsidiaries of that power station.
A 50 Hz electrical substation in Melbourne. This is showing three of the five 220 kV/66 kV transformers, each with a capacity of 150 MVA. This substation is constructed using steel lattice structures to support strain bus wires and apparatus.
Elements of a substation
A: Primary power lines' side B: Secondary power lines' side
1.Primary power lines 2.Ground wire 3.Overhead lines 4.Transformer for measurement of electric voltage 5.Disconnect switch 6.Circuit breaker 7.Current transformer 8.Lightning arrester 9.Main transformer 10.Control building 11.Security fence 12.Secondary power lines
Substations generally have switching, protection and control equipment, and transformers. In a large substation, circuit breakers are used to interrupt any short circuits or overload currents that may occur on the network. Smaller distribution stations may use recloser circuit breakers or fuses for protection of distribution circuits. Substations themselves do not usually have generators, although a power plant may have a substation nearby. Other devices such as capacitors and voltage regulators may also be located at a substation.
Substations may be on the surface in fenced enclosures, underground, or located in special-purpose buildings. High-rise buildings may have several indoor substations. Indoor substations are usually found in urban areas to reduce the noise from the transformers, for reasons of appearance, or to protect switchgear from extreme climate or pollution conditions.
Types
Substations may be described by their voltage class, their applications within the power system, the method used to insulate most connections, and by the style and materials of the structures used. These categories are not disjointed; to solve a particular problem, a transmission substation may include significant distribution functions, for example.
Transmission substation
SF6 110 kV instrument current transformer TGFM series, Russia
A transmission substation connects two or more transmission lines. The simplest case is where all transmission lines have the same voltage. In such cases, substation contains high-voltage switches that allow lines to be connected or isolated for fault clearance or maintenance.
Transmission substations can range from simple to complex. A small "switching station" may be little more than a bus plus some circuit breakers. The largest transmission substations can cover a large area (several acres/hectares) with multiple voltage levels, many circuit breakers and a large amount of protection and control equipment.
Distribution substation
A distribution substation in Scarborough, Ontario
A distribution substation transfers power from the transmission system to the distribution system of an area. It is uneconomical to directly connect electricity consumers to the main transmission network, unless they use large amounts of power, so the distribution station reduces voltage to a level suitable for local distribution.
The input for a distribution substation is typically at least two transmission or sub-transmission lines. Input voltage may be, for example, 115 kV, or whatever is common in the area. The output is a number of feeders. Distribution voltages are typically medium voltage, between 2.4 kV and 33 kV depending on the size of the area served and the practices of the local utility. The feeders run along streets overhead (or underground, in some cases) and power the distribution transformers at or near the customer premises.
Switching substation
Switchyard at Grand Coulee Dam, USA, 2006
A switching substation is a substation without transformers and operating only at a single voltage level. Switching substations are sometimes used as collector and distribution stations. Sometimes they are used for switching the current to back-up lines or for parallelizing circuits in case of failure.
A switching substation may also be known as a switchyard, and these are commonly located directly adjacent to or nearby a power station.
Вправа 3. Дайте відповіді на питання.
What is a substation?
What do substations transform?
How may be substations owned and operated?
What do substations include?
What equipment do substations have?
What are the elements of substation?
What are the types of substations?
What do you know about transmission (distribution, switching) substations?
Вправа 4. Виберіть правильні твердження по тексту.
A substation is a part of an electrical instrument.
Substations transform voltage from high to low, or the reverse, or perform any of several other important functions.
A substation may include transformers to change voltage levels between low transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages.
The first substations were connected not to only one power station, where the generators were housed, and were subsidiaries of that power station.
In a large substation, circuit breakers are used to interrupt any short circuits or overload currents that may occur on the network.
Other devices such as capacitors and voltage regulators may also be located at a substation.
The simplest case is where all transmission lines have the same voltage.
A distribution substation transfers power from the transmission system to the distribution system of an area.
Input voltage may be, for example, 200 kV, or whatever is common in the area.
A switching substation is a substation without transformers and operating only at a single voltage level.
Вправа 5. Розшифруйте абревіатури.
a.c., a.f., bev., cgs., c.p.s., db, d.c., e.m.f., e.v., i.f., r.f., sq.
Вправа 6. Перекладіть речення.
Selection of the location of a substation must consider many factors.
Sufficient land area is required for installation of equipment with necessary clearances for electrical safety, and for access to maintain large apparatus such as transformers.
Where land is costly, such as in urban areas, gas insulated switchgear may save money overall.
The site must have room for expansion due to load growth or planned transmission additions.
Environmental effects of the substation must be considered, such as drainage, noise and road traffic effects.
A grounding (earthing) system must be designed.
The total ground potential rise, and the gradients in potential during a fault (called "touch" and "step" potentials), must be calculated to protect passers-by during a short-circuit in the transmission system.
The substation site must be reasonably central to the distribution area to be served.
In a common design, incoming lines have a disconnect switch and a circuit breaker.
In some cases, the lines will not have both, with either a switch or a circuit breaker being all that is considered necessary.