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On oil-cooled machinery (i.e., transformers), moisture can only
be detected by regular oil samples. Moisture will be sucked into
the oil via the oil expansion air vent, through the continuous
process of transformer heating and cooling cycles.
Special air dryers and absorbents can assist in decreasing the
rate the moisture is absorbed into the oil.
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%.

4 Read Text 3:
Text 3
Excessive Temperature

On air-cooled electrical machinery, prolonged high temperature
causes thermal aging. This causes the insulation to become brittle.
Eventual failure can occur due to moisture penetration as just
discussed, or by physical contact of conductors.
In oil-filled transformers the effect is called insulation aging.
Chemical aging occurs more rapidly at high temperatures, with the
loss of insulation life being almost exponential with temperature.
As an example – for a standard 65°C (temperature rise) rated
insulation the loss of life increases from 0.001% per hour at 100°C
to 0.05% per hour at 140°C and 1.0% per hour at 180°C.
Translated into time span the expected insulation life would be
11.4 years at 100°C, 83 days at 140°C, 100 hours at 180°C.
It is fairly clear to see the importance of maintaining a daily
record of the operating temperatures and ensuring that all electrical
equipment are kept at low ambient temperatures.

5 Make a written translation of Text 3.

6 Pick out from Texts 1-3 all the sentences containing Modal
Verbs and translate them into Ukrainian.

7 Speak about organic and inorganic insulation materials
using Text 1.

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