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Instruction Manual
2. DESIGN AND CONSTRUCTION
2.1. Inverted construction and
primary circuit
The active part of the OSKF72 current
transformer is located above the
insulator. The advantages of this
construction concern the primary circuit
conception. The primary circuit is short,
rigid and straight, minimizing heating. In
addition, it bears electrodynamics forces
more
easily,
performance,
electrodynamics and thermal effects, in
a presence of short-circuit currents. The
primary bar (simple or multiple ratios)
with magnetic circuits are centered to
assure a distributed magnetic flow in
uniform way to avoid local saturation.
This arrangement allows also better
accuracy in transient conditions.
2.2. Secondary circuit
The ring-shaped magnetic circuits are
manufactured either from very high
permeability grain-oriented steel or
from nickel alloy. In order to achieve a
satisfactory
protection cores can also be provided
with gaps.
OSKF72
may
protection cores with different burdens
and
different
Secondary turns are evenly wound
around the circumference of the ring-
shaped cores. Changing ratio is available
by means of taps on the secondary or
primary side.
© GE Grid Solutions
allowing
high
level
relating
transient
behavior,
have
metering
and
accuracy
classes.
All secondary windings are enclosed in
an aluminum box which protects them
against high frequency disturbances
while acting as a low voltage shielding
electrode.
extended up to the base by an aluminum
tube which contains all secondary leads.
The
cross
connections is designed to support
defect currents.
The bottom of the hermetic and
watertight secondary terminal box is
closed by a fitted plate, with or without
to
cable gland depending on customer
requirements.
2.3. Paper-oil insulation
Insulation
secondary circuits is made by multiple
layers of insulating papers impregnated
with mineral oil.
To protect the oil from the environment,
the CT head is closed by a metallic
bellows. The bellows adapts to the
changes in oil volume without producing
any increase or decrease in internal
pressure. This bellows resists aging and
corrosion.
This
aluminum
box
section
of
the
between
primary
is
earth
and
6
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