Figure 3. Concept of electric energy transmission

 

The voltage is reduced at the 500 kV/220 kV EHV substation to the high-voltage level and high-voltage lines transmit the energy to high-voltage substations located within cities.

At the high-voltage substation the voltage is reduced to 69 kV. Sub-transmission lines connect the high-voltage substation to many local distribution stations located within cities. Sub-transmission lines are frequently located along major streets.

The voltage is reduced to 12 kV at the distribution substation. Several distribution lines emanate from each distribution substation as overhead or underground lines. Distribution lines distribute the energy along streets and alleys. Each line supplies several step-down transformers distributed along the line. The distribution transformer reduces the voltage to 230/115 V, which supplies houses, shopping centers, and other local loads. The large industrial plants and factories are supplied directly by a subtransmission line or a dedicated distribution line as shown in Fig. 3.

The overhead transmission lines are used in open areas such as interconnections between cities or along wide roads within the city. In congested areas within cities, underground cables are used for electric energy transmission. The underground transmission system is environmentally preferable but has a significantly higher cost. In Fig. 3 the 12-kV line is connected to a 12-kV cable which supplies commercial or industrial customers. The figure also shows 12-kV cable networks supplying downtown areas in a large city. Most newly developed residential areas are supplied by 12-kV cables through pad-mounted step-down transformers as shown in Fig. 3.

 

1. Read and translate the text.

2. Read the text again and make a plan in the form of questions.

3. Read and decide if the following statements are true (T) or false (F).

1) A single-phase AC system is used for most transmission lines.

2) At nuclear power plant energy is generated by means of atomic fission.

3) Disconnect switch is a large switch that interrupts the load and fault current.

4) 25 kV is enough for the transmission of energy over long distances.

5) The sub-transmission line supplies current to the large factories and plants.

 

4. Match the words in the box with their corresponding definitions below.

 

Distribution, circuit breaker, switchgear, dam, transmission system, substation, fission.

 

 

1) A metallic circuit of three or more conductors used to send energy usually at high voltage over a considerable distance

2) the final stage in electricity delivery

3) a barrier to obstruct the flow of water, especially one of earth, masonry, etc., built across a stream or river

4) the splitting of the nucleus of an atom into nuclei of lighter atoms, accompanied by the release of energy

5) any of several devices used for opening and closing electric circuits, esp those that pass high currents

6) an installation at which electricity is received from one or more power stations for conversion from alternating to direct current, reducing the voltage, or switching before distribution by a low-tension network

7) a device for interrupting an electric circuit to prevent excessive current, as that caused by a short circuit, from damaging the apparatus in the circuit or from causing a fire.

 

5. Look through the text and connect the verbs with prepositions and make sentences

interconnection appropriate equal mixed connected protected insulates increased

Of/to/for/from/to/with/from/to

TEXT 12. Transmission Line Structures

An overhead transmission line (OHTL) is a very complex, continuous, electrical/mechanical system. Its function is to transport power safely from the circuit breaker on one end to the circuit breaker on the other. It is physically composed of many individual components made up of different materials having a wide variety of mechanical properties, such as:

• flexible vs. rigid

• ductile vs. brittle

• variant dispersions of strength

• wear and deterioration occurring at different rates when applied in different applications within one micro-environment or in the same application within different micro-environments