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A. ROTATING HAMPER ASSEMBLY
The rotating hamper assembly consists of a tubular
section of aluminium alloy of adequate cross-section
clamped at the centre point. It rotates through
110o degrees for the closing / opening operation
of the disconnector. The size of the aluminium
alloy tube and its thickness is selected based
on the continous and short time current carrying
capacity of the required disconnector. Silver
plated copper contacts are fixed on to this rotating
aluminium alloy blade at either ends.
S&S Double Break Disconnectors are of a special
design, have a turn and twist feature. In this
design, the disconnector blade first moves in
the horizontal plane and after touching a stopper
on the fixed contact, the tubular blade itself
rotates giving a twisting motion. Only during
this twisting movement, the contacts mounted on
the moving blade actually makes contact with the
fingers on the fixed contact assembly. This rotating
motion of the blades ensures that adequate contact
pressure is build up between the fixed and moving
contacts for carrying the rated currents. This
design also has a further advantage that during
the closing operation of the disconnector, the
actual current carrying surfaces do not come into
the contact till the twisting motion occurs, there
by ensuring that there will not be any damage
to the surfaces of the contacts during the closing
of disconnector. The contacts are of the self
wiping nature and cleans the contact surfaces
while closing and opening of Disconnector. This
type of contact arrangement is called he pressure
relieving reverse loop type.
The moving aluminium alloy blades are clamped
onto the turn and twist mechanism which is housed
in an aluminum housing for 420kV and 245kV Disconnectors.
The turn and twist mechanism flange is then mounted
on to top flange of the centre insulator of each
pole.
B. FIXED CONTACT ASSEMBLIES
Each pole of the Disconnector consists of two
fixed contact assemblies. The fixed contact assembly
consists if a housing onto which the silver plated
copper contact fingers are mounted. Each contact
finger is provided with a S&S compression
to ensure that the required contact pressure is
maintained.
The fixed contact assembly also consists of a
terminal pad. The terminal connector is fixed
onto this terminal pad on four holes provided
thereon.
C. SUPPORT INSULATORS
The Double Break Disconnector consists of three
stacks of support insulators per pole or 9 stacks
per 3 pole disconnector. Out of the three insulators
per pole, the outer two insulators are stationary
and centre insulator rotates through 118 degrees
for closing / opening of the Disconnector. Due
to this reason, this type of Disconnector is also
referred to as the Double Break Centre post Rotating
type disconnector .
The fixed contact assemblies are mounted on top
of the outer stacks of insulator which are stationary
and the turn and twist mechanism along with the
rotating hamper assembly is mounted on the centre
stack of insulator.
The function of the outer stack of insulator
is to keep the fixed contacts rigid, provide the
necessary creepage distance and the insulation
between the live parts and ground. The function
of the center stack of the insulator is to rotate
though 118° degrees provide the necessary
creepage distance and the insulation between line
parts and ground. Insulator corona rings are provided
for 420kV / 245kV Disconnectors.
D. DISCONNECTOR BASE
Disconnector base is made of welded assembly.
The base consists of three flanges, two at either
ends and one at the centre for mounting the support
insulators. These flanges are provided with the
necessary holes at the required pitch circle diameter
to match with the holes provided on the insulator
base flange. The two end flanges are welded on
to the base of the disconnector adaptors. The
center flange is welded to the bearing shaft.
The bearing shaft is assembled with two numbers
taper roller bearings, aluminium bearing housing.
These bearings are seated one on top and another
on bottom of the base assembly and these ensure
smooth and free movement of the Centre rotating
post of the disconnectors. Bearing caps are provided
to ensure that water and dust do not enter the
bearings. Provision is made on the base for mounting
the mechanical constructional interlock between
disconnectorand earth switch wherever required.
The base is provided with mounting arrangements
at four / eight points for fixing the disconnector
base the supporting structure.
Earthing pad / earthing studs are provided at
two points at the extreme ends of the base for
connecting to the customers sub station earthing
systems.
E. INTER PHASE COUPLING PIPES
Inter Phase coupling pipes are provided to couple
the three phases of the Disconnector and operate
all the three phases from a common operating mechanism
in the case of Mechanically Ganged three pole
Disconnectors. These are not required in the case
of single pole Disconnectors where each pole is
operated by its own operating mechanism. The coupling
pipes are linked to one base flange on each phase
of the three pole disconnector. These are despatched
loose and are to be assembled at site. Provision
is available to do minor adjustments in length
of the coupling pipe to suit site conditions.
F. SUPPORT STRUCTURE
Wherever specified, support structure of tubular
types for 420kV disconnector and lattice type
for 245kV and below disconnectors with necessary
foundation bolts can be supplied. Plates are welded
on to this tubular support structure fabricated
out of welded sheet steel for 420kV Disconnectors
for mounting the operating mechanism boxes, the
operating mechanisms of the disconnectors / earth
switches are mounted on to the structure on plates
provided, being bolted with the angles, that are
provided on the mechanism box. The height of this
support structure can be varied to accommodate
the bus height as required by the purchaser's
layout and system.
G. OPERATING MECHANISM
Motor Operating mechanism or manual Operating
Mechanisms can be supplied as per customer requirement
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H. INTERLOCKS
The following interlocks are provided for the
Horizontal centre break disconnectors.
A mechanical constructional interlock between
the disconnector and earth switch has been provided
to ensure that the Earth Switch can be closed
only when the Disconnector is in the open position
and vive versa.
An electro-mechanical castle key type interlock
has been provided in each motor operating mechanism
for interlocking between manual and motor operation
of Disconnector / Earth switch. This ensures
that the motor circuit is cut off when the manual
operation is under progress.
In some cases, only electrical bolt coils are
provided as interlocks solely controlled by electrical
circuits.
Based on customer needs either Electro-mechanical
or Electrical interlocks will be provided.
Note:
Horizontal Double Break Disconnector can be
supplied by us either without Earth switch,
with Single Earth switch or with Double Earth
switch.
Double Break Disconnectors are normally offered
for Horizontal, normal level, upright mounting.
But on request these can be offered for other
types of mounting like series, vertical; higher
I level, underhung, tandem etc.,
Horizontal Double Break disconnectors / Earth
switches supplied by us are generally Mechanically
Ganged for operation of all three poles from
a common operating mechanism cabinet. However
we can supply 420kV Centre Break Disconnectors
with the three poles being operated by 3 separate
mechanisms, which are electrically ganged to
operated together, if so desired by the purchaser.
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