Техническое чтение для энергетиков. Бухарова Г.П. - 63 стр.

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65
water is then passed through this cooling coil. Since the presence of even a minute
percentage of water in the oil reduces its insulating properties to an enormous degree,
it is extremely important that no water should escape through any leak, should one
occur.* In order to prevent this, the tank is made oil-tight and the oil is put under
pressure. If a leak should develop, oil will leak into the tubes (which does not much
matter) instead of the water leaking into the oil.
In confined spaces, and where a supply of water is not available, air-blast cooling
may be adopted. The tank is now dispensed with**, and a blast of cold air is forced
over the transformer windings. Cooling by this means is usually confined to
transformers operating on the lower voltages.
* it is extremely important that no water should escape through any leak, should one occur крайне
важно, чтобы вода не просачивалась через какое-либо неплотное соединение, в случае, если
таковое окажется; should escape – форма сослагательного наклонения глагола, которая
употребляется для выражения цели в придаточных предложениях-подлежащих, вводимых
союзом that после, безличного оборота типа it is important, should one occur = if one should
occur; should употребляется в условном предложении для выражения малой вероятности
действия, обозначенного инфинитивом глагола; leak – означает: утечка, отверстие;
неплотное соединение
** the tank is now dispensed with в этом случае обходятся без бака; (to) dispense with
обходиться без чего-либо. Предлог with занимает место непосредственно после глагола, в
силу особенностей английских пассивных оборотов.
Transformer Oil
The oil used for transformer immersion is a pure hydrocarbon (mineral) oil, obtained
by refining crude petroleum. Its insulating properties are very adversely affected by
the presence of even a minute proportion of water, and so it must be clean and
practically free from moisture. Certain oils tend to form a sludge in the course of
time, this being due to the slow formation of solid hydrocarbons. If this sludge should
form on the windings themselves it tends to produce overheating. Certain high-grade
qualities are called non-sludging oils, and these should be used in transformers in
which the working temperature of the oil exceeds 80° C.
The use of the oil-expansion chamber reduces the tendency of the oil to form sludge,
since the access of atmospheric oxygen is effectively prevented. The addition of the
breather also keeps the oil dry.
CURRENT TRANSFORMERS
Why Current Transformers are Used. – A current transformer is an instrument
transformer for the transformation of current from one value to another, usually a
lower one, or for the transformation of current at a high voltage into a proportionate
current at a low voltage with respect to earth potential. Current transformers are used
in conjunction with alternating-current meters or instruments where the current to be
measured is of such magnitude that the meter or instrument current coil cannot
conveniently be made of sufficient carrying capacity. They are also used wherever

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