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CONTROL TASKS

1 Answer the questions:

1. What are the main precautions when working on low voltage
energized equipment ?
2. What engineers should know about using conduits in power
substation designs?
3. What is physical structure and configuration of direct current
machines?
4. What are the most common contributing factors in insulation
failure?
5. What types of electrical power distribution systems do you
know?
6. What do you know about distribution systems?
7. Give a definition of switching capacity.
8. What are the methods of securing LV circuit breakers?
9. What are the most known high voltage insulation methods?
10. Which type of residual current device should you use and
when?

2 Make a written translation of the following:

On air-cooled electrical machinery, the moisture content of the
air is very important. With aging of the insulation, small hairline
cracks will appear in the insulation. Moisture will seep into these
cracks and allow an electrical path to short-circuit between
adjacent turns of wire.
Although the voltage between the turns is quite small, when
they short together, a closed loop to the magnetic flux is provided,
and this causes tremendous currents to flow in the shorted loop.
This usually destroys the electrical machine, and it has to be
removed and re-wound/replaced.
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.

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