cooled Current Transformer
Oil cooled transformers are made for use on various systems ranging
from 11kv to 33kv. the basic construction of the CT is similar to
CT of all voltage classes in that the core is placed in a tank mounted
on top of the bushing and adequate paper insulation is provided
on it. The secondary leads are run through the bushing to the secondary
terminal box placed at the bottom of the bushing.
advantage of this type of construction is that the transformer is
dynamically more stable under short circuit conditions, the various
forces on the primary conductors tending to balance on another.
Requisite number of the primary turn are put on the core and the
two ends are bought out for connection into the system. The primary
ends are terminated on the terminals 30 mm dia 80mm long for easy
connection into the system.In the case of two ratio current transformer
in which the different ratios are obtained by primary reconnection,
four primary terminals are brought out on the tank(corresponding
to the two primary windings) and these are connected in series or
parallel, by connecting links provided depending upon the ratio
required. The transformers are fully sealed in construction and
are supplied filled with required quantity of oil. Adequate allowance
is made for expansion of oil due to temperature variations and as
such a breather is considered unnecessary.
Since the transformer oil is never exposed to
atmosphere the danger of its contamination is completely avoided.
It is therefore not necessary to clean the oil during the life of
the transformer. Oil fills and oil drains are, therefore not provided
on the current transformers for voltages less than 132kv. For current
transformers for 132 kv systems, oil fill and oil drain is provided
but these are purely for manufacturing convinience and these are
fully sealed before despatch.
product is type tested at ERDA, Baroda
information required for tendering
Short Time Current Rating