Page 41 - 4587

supply network.
• In the event of a fault, the current flowing in the customer’s
earthing conductors can be much greater that for a TNS system.
• It is also possible to get unusual circulating earth currents
between properties, particularly where some properties have metal
water pipes and others have plastic.

3 Decide, whether the following statements are true or false in
relation to the information in the text. Change false statements
into true ones.
1. When a connection has not been made between the neutral
point and earth, we say that the neutral is earthed.
2. A directly earthed neutral strongly limits over voltages.
3. The choice of earthing system in both low voltage and
medium voltage networks depends on the type of installation but
not on the type of network.
4. The main objectives of an earthing system are to provide
an alternative path for the fault current to flow.
5. Although the amount of over current produced in different
types of installation differs from each other, required type of
earthing will not differ according to the type of installation.

4 Make the following phrases complete.
1. The neutral and Earth conductors are separately distributed
to … .
2. Special measures must be taken for the loads or parts of the
installation causing high … .
3. Voltage between phase to phase called … .
4. Different earthing systems are capable of carrying … .
5. Electrical power is distribution either three wires or .. .

5 Divide Text 1 into logically complete parts and give each a
subtitle.
6 Put questions to each part of Text 1.
7 Find, read and translate the sentences in Text 1 in which we
learn how to choose the earthing system.

8 Working in pairs test each other’s ability to describe system
characteristics, advantages and disadvantages of different
earthing systems.

40