Ac overhead equipment

Power is supplied to the trainset by an overhead catenary system operating at a normal voltage of 25kV. This consists of a normally horizontal contact wire made from hard drawn copper, suspended by means of wire “droppers” from a catenary wire cable. The catenary itself is supported on masts or portal frames spaced along the tracks at a maximum spacing of 73 meters apart. To equalize the wear of the pantograph carbons, the copper contact wire zig-zags on plan along the center of the track, the offset at each support point being on 230 mm straight track.

The height of the contact wire above rail level varies between the limits of 4.14 meters and 5.94 meters to accommodate minimum clearance under bridges and to satisfy requirements at level crossings.

Ex.7. Make up sentences according to the Model.

Model: The masts are spaced along the track.

Power Contact wire Clearance Pantograph Catenary

is mounted is required is supported is suspended is supplied

by means of wire “droppers”. under bridges and at level crossings. on masts or portal frames. to the train by a catenary system. on the roof a train.

Ex.8. Translate the sentences into English.

1. Электричество – более экологически безопасный вид энергии, чем другие.

2. Электрогенератор на поезде вырабатывает меньше энергии, чем электростанция.

3. Электровозы используются более часто, чем тепловозы.

4. Электрическая тяга более эффективна, чем дизельная.

5. Электровозы более мощные, чем тепловозы.

6. Самые протяженные линии электрических железных дорог находятся в России.

7. Тепловозы менее надежные и более шумные.

8. Использовать тепловозы дороже, чем электровозы.

9. Электроэнергия – это самый распространенный вид энергии.

10. Электровозы имеют меньше недостатков, чем другие виды локомотивов.

Ex.9. Speak about:

• electric traction;

• diesel traction;

• advantages and disadvantages of both types of traction;

• overhead catenary system.

Unit 7 Grounding System Installations

The current leaving the train first passes into the running rails of the railway. The running rails are connected to one another and the electrification masts at regular intervals to create a distributed earth (ground) along the railway. This distributed earth enables current to pass from the rails into the greater mass of earth and in this way it maintains the rails close to earth potential. This limits the danger to personnel working on or about the railway.

For the same reason all metalwork which is exposed to touch and may become accidentally energised is also connected to the rails. Exposed metalwork may become energised due to an insulator flashover or by coming into contact with a broken energised conductor. The earthing system also ensures that, in the event of an electrical fault, the current is of sufficient magnitude to operate the protective relays of the railway and thereby open the appropriate circuit breakers to isolate the faulty section.

Ex.1. Answer the questions:

1. Why is grounding system important?

2. How does the grounding system work?

3. What risk can be presented by metalwork?

4. How can the grounding system help in the event of an electrical fault?

Ex.2. Make up word collocations and translate them into Russian.

The current The rails The earth The personnel The metalwork The metal parts The faulty section

running leaving isolated distributed exposed working energised

by circuit breaks the train to touch by broken conductor on the railway along the railway in one direction

Ex.3. Before listening to the text below answer the questions:

1. Why is it important to ground wires?

2. What are safety rules when installing grounding system?

3. How does soil condition effect grounding installation?

Ex.4. Listen to the text and fill in the gaps.

soil, important, electricity, components, wire, condition, materials, grounding, install.