3. Find English equivalents of the following words and word combinations in the text.

Линейные проводники; механическая прочность; разорвать на куски; давать трещину; выдерживать разницу температур; желоб; защитить от дождя; располагать вертикально/горизонтально; вторичная стойка; арматура; не такой ломкий, как стекло; распределительные цепи.

4. Give the Russian equivalents of the following expressions.

Electrically insulated, to consider electrical properties, to withdraw loading in compression, under tension, to make the forces acting, not break during installation, polymer insulations, be classified as pin or post type, to install on the cross arm of the pole, to screw on the pin, tie wire, high voltage application, to diminish strength, hanging type, variation of the suspension insulator, to sustain extraordinary pulls.

5. What answer is incorrect?

Pin – type insulator …………………

a) is design to be mounted on a pin;

b) is used for lower voltage applications;

c) is used for high voltage transmission lines;

d) is applicable for rural and urban distribution lines;

e) is designed to shed sleet and rain.

6. Answer the questions.

1. What is the function of an insulator?

2. What are the types of insulators?

3. What materials are insulators made of? What are their electrical and mechanical properties?

4. What are the main advantages of pin insulators?

Unit 7 (part 2). Conductors and insulators

1. Words to remember.

suspension insulator – подвесной изолятор

spool insulator – катушечный изолятор

strain insulator – натяжной изолятор

bulky – массивный

cumbersome – громоздкий

string – подвесной провод

a sharp curve – кривая малого радиуса

guy cable/wire – оттяжка (антенны)

to pierce – протыкать, пробивать отверстие

secondary main – вторичная электрическая цепь

clevis – скоба

tapered hole – заостренное, конусообразное отверстие

evenly – равномерно

clamp – зажим, хомут

secondary rack – вторичная стойка

to loop – соединить в петлю

2. Read the text. Suspension insulators

The higher the voltage, the more insulation is needed. Transmission lines use extremely high voltages, 69,000 to 375,000 volts, for example. At these voltages the pin or post-type insulator becomes too bulky and cumbersome to be practical, and the pin which must hold it would have to be inordinately long and large. To meet the problem of insulators for these high voltages, the suspension insulator was developed. The suspension insulator hangs from the cross arm, as opposed to the pin insulator which sits on top of it. The line conductor is attached to its lower end. Because there is no pin problem, any distance can be put between the suspension insulator and the conductor can be provided just by adding more insulators to the ‘string’. The entire unit of suspension insulators is called a string. How many insulators this string consists of depends on the voltage, the weather conditions, the type of transmission construction, and the size of insulator used. It is important to note that in a string of suspension insulators one or more insulators can be replaced without replacing the whole string.

Strain Insulators. Sometimes a line must withstand great strain for instance at a corner, at a sharp curve, or at a dead-end. In such a circumstance the pull is sustained and insulation is provided by a strain insulator. On a transmission line, this strain insulator often consists of an assembly of suspension insulators. Because of its peculiarly important job, a strain insulator must have considerable strength as well as the necessary electrical properties. Although strain insulators come in many different sizes, they all share the same principle; that is, they are constructed so that the cable will compress the porcelain. Strain insulators are sometimes used in guy cables, where it is necessary to insulate the lower part of the guy cable from the pole for the safety of people on the ground. This type usually consists of a porcelain piece pierced with two holes at right angles to each other through which the two ends of the guy wires are looped, in such a manner that the porcelain between them is in compression.

Spool Insulators. The spool-type insulator, which is easily identified by its shape, is usually used for secondary mains. The spool insulator may be mounted on a secondary rack or in a service clamp. Both the secondary low-voltage conductors and the house service wires are attached to the spool insulator. The use of such insulators has decreased greatly since the introduction of cabled secondary and service wires. The tapered hole of the spool insulator distributes the load more evenly and minimizes the possibility of breakage when heavily loaded. The ‘clevis’ which is usually inserted in this hole is a piece of steel metal with a pin or bolt passing through the bottom.