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With oil-filled transformers it is important to note that very
little moisture content is required to tremendously decrease the
insulation value of the oil. Only 30 parts of water per million parts
of oil can decrease the insulation capability by 50%.

3 Give Ukrainian equivalents of the following:

circuit-protective devices current-limiting devices
motor-operated disconnect medium-voltage circuits
switches
series-connected motors compound-connected
machine
air-cooled electrical machinery magnetic flux
hardwired control circuit low-voltage protection
earthing system insulation fault,
distribution substation primary distribution system,
isolating switches load switches,
switching capacity short-circuit making capacity
residual current device earth loop impedance
bolted to the bus receptacle connection
electric field strength gradient rapid insulation failure

4 Tell whether each of the following statements is true or false
according to the text. Correct the false statements to make
them true:

1. It is necessary to plan the whole job in advance so that you can
take every precaution, including arranging for help in case of
paralyzing shock.
2. The typical design of a cable system will include conduit burial
depth, bending radius, calculations on conduit fill, and
determination of cable ampacity de-rating.
3. If high-voltage protection is required, then the starter’s auxiliary
contacts or the overload contacts can be programmed.
4. 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.
5. The purpose of the isolating function is to cut off the supply
from all or a discrete section of the installation by separating the

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