HELICALLY FORMED FITTINGS

Report
HELICALLY FORMED
FITTINGS
SUPREME AND CO. PVT. LTD.
KOLKATA
Leading Manufacturer of all kinds of
Helical Fittings
 Helical
fittings are composed of multiple helical rods
which are manufactured for a particular application
meant for specific conductor which are in the form of
separated or preassembled, straight or looped
 Helical
fittings are now already in use for a wide
variety applications.
 However,
the range of its application continue to
expand
 There
may be many more applications hidden in the
womb of future, which we cant even foresee today
 This
presentation in respect of the application of
helical fittings mainly refers to T & D application
especially to the use on overhead lines and
distribution systems.
 Helically
Formed accessories can be used as
dead end termination, to support and to
connect conductors, cables.
 In
addition helically formed accessories are used to
protect or to repair conductors, for attachment to pin
insulators, as spacers on bundled conductors and for
anchoring the street lighting brackets.
 They
are also successfully used to prevent birds from
coming in accidental contacts with the conductors.

Helically Formed accessories have very successfully been used
since 1950. The employment of helical fittings is not at all limited
to overhead lines only. Helically Formed accessories in a large
measure are also used for the construction of antennas, radar
stations & for providing support to the columns in case of preengineered buildings & for anchoring submarine cables to the
ships during periodic maintenance or repairs

The effect of helical fittings is mostly based on the principle of
development of a low unit clamping strength by uniformly
distributing the clamping load over a large cross sectional area

The inside diameter of the unapplied helical rods is slightly
smaller than the outside diameter of conductor, cable or solid
rod. It provides a very good gripping force and prevents it from
slipping under tension

To ensure the full performance, the helical fitting must be
adapted matching to the outside diameter of conductor, cable
or solid rod

In addition, helical fitting and outer strand of conductor must
be of same lay direction. Unless specified otherwise, helical
fittings are of right-hand lay on delivery

Hence, it is necessary to specify on order if helical fittings for
left-hand lay conductors are required

In general, helical fittings are made from a material similar to
that of conductor or solid rod in order to avoid bimetallic
corrosion due to contact

The helical rods can be installed without use of any tool,
therefore incorrect assembly is almost impossible

It can be detected by mere eyesight whether it was correctly
installed. Hence, helical fittings can be installed by the workers
with proper guidelines.

Helical fittings are provided with a label stating for which
function and for what conductors, cables the respective
accessory is designed for.

Helical fittings can be used:
- for tension / dead end termination
- for suspension
- for splicing
- for repairing
- to armor
- to protect against damage
- to protect against abrasion
- to reduce stress
- to mark
- to space
- to damp vibrations
- to pull (installation)
- to shunt weak splices
- as inter-phase spacer
- to increase diameter of
stranded conductors, cables and solid conductors.
Based on the application we can broadly
separate Helically Formed fittings into
FOUR Groups:

Dead End Fittings

Support

Vibration Control

Conductor Accessories
DEAD END FITTINGS- USED FOR
ANCHORING WIDE RANGE OF WIRES, CABLES AND
CONDUCTORS

Guy Wire

Conductor MV

ADSS

OPGW

Insulated Neutral

Bare Conductor LV

Bare Neutral

Pole Top Make Off

Service wire/cables

Adjustable Grip Dead End

Insulator Link Assembly
SUPPORT
 Line
Ties
 AGS
 Line
Guards
VIBRATION CONTROL &
CORONA MITIGATION

Spiral Vibration Damper

Corona Coil
CONDUCTOR ACCESSORIES

Bundle Spacer

T Connector

Splices – Full Tension

Splices – Repair

Lashing Rod
DEAD END FITTINGS
GUY WIRE

A guy is a tensioned cable designed to add stability to a
free-standing structure.

Normally, Utility Poles are buried in the ground and have
sufficient shear strength to stand on their own; guys are
only needed on some poles to support unbalanced
lateral loads due to the utility wires attached to them.
Conductor MV

MV (Medium Voltage) – between 1000 volts (1 kV) and to
about 33 kV, is used for electric distribution in urban and rural
areas.

Conductors are designed for designated mechanical loads and
ratings and helical fittings are suitably designed to withstand
the mechanical rating of the conductor.
ADSS

All-dielectric self-supporting (ADSS) cable is a type of optical
fibre cable that contains no conductive metal elements. It is
used as a communication medium. It needs no additional
messenger cables for mechanical support as it is itself capable
to sustain loads required by the pylons and poles.

It is designed to be strong enough to allow lengths of up to 700
metres to be installed between support towers.

ADSS cable is designed to be light weight and small in diameter
to reduce the load on tower structures due to cable weight,
wind, and ice.
OPGW

Optical Fibre Composite Overhead Ground Wire combines
both the functions of grounding and communications.

The optical fibres within the cable can be used for high-speed
transmission of data.

The optical fibre itself is an insulator and protects against
power transmission line and lightning induction,
external noise and cross-talk.
INSULATED NEUTRAL & BARE NEUTRAL

Bare Neutral is a circuit conductor that carries current in
normal operation, which is connected to ground (or earth) and
when an insulation is applied on it the same is called as
Insulated Neutral.
Bare Conductor LV
Bare overhead conductors from other energy carriers are to
utilize air as a natural insulation for conductors suspended from
towers.
 Bare conductors are used where phase to phase separation is
done through air and insulation of phase electrode from ground
electrode is done using polymeric, porcelain or glass insulators.

POLE TOP MAKE OFFS
 Pole Top Make offs are primarily intended for pole top
termination of stay strands when an insulator is being
used.
SERVICE GRIPS
 Service Grips are usually used for service drops lower than
150 ft above which distribution grip dead end is
recommended.

These are very simple to apply and ensure a tight assembly
and prevent distortion.
Adjustable Grip Dead End
 Adjustable Grip Dead Ends are designed for use on
Transmission, Antenna, Communications, and other
types of guyed structures that require use of large guy
strand.
 Adjustable Grip dead-end components such as the
housing, U-Bolt, and hex nuts allow for adjustment in
guy tensions.
Insulator Link Assembly
 Insulator Link Assembly is designed to link two stay
insulators in series on unearthed overhead line
structures.
 The insulators can be placed in any required position on
the stay, to which they are attached at either end by Guy
Grip Dead Ends.
SUPPORT
Line Ties

Line Ties are generally used to secure the conductors in the grooves of
insulators.
These are broadly classified as:1.
Distribution Ties
2.
Side Ties
3.
Spool Ties for reel insulators
4.
Plastic Ties for covered conductors



The selection of the material to manufacture the ties depends on the type of
conductor used e.g. aluminium alloy wires or aluminium clad steel wires for
aluminium conductors, galvanized steel wires and plastic wires used for
covered conductors.
The ties are supplied with an elastomeric tie pad which is designed for
abrasion protection with bare conductors.
AGS
AGS i.e. Armour Grip Suspension is a kind of helical fitting designed
to reduce the static and dynamic stresses induced at a support point
such that the conductor and its strands are protected against the
effects of oscillations.
 The whole set comprises of :
1.
Armour Rods which are designed to protect the conductor by
reducing bending, compression, and abrasion at the support
point.
2.
AGS Clamps are basically manufactured from aluminium alloy
treated as a housing of the helical fitting after fitment with the
neoprene cushion applied with the conductor. The connecting
fasteners with the hardware fittings is galvanised steel.

3.
Insert made from Rubber Cushion reinforced with aluminium
sheet works as a cushion on the conductor and absorbs stresses
induced at the support point.
Plastic Pre-form Ties
 These are intended for use with covered conductors to
avoid abrasion of insulation in the conductors but are
designed to be used for a particular area since at
particular field conditions burning or tracking may
occur in the tie.
Line Guards

Line Guards are used to protect the conductor against
bending, compression, abrasion, arc over, and to
provide repair, particularly where hand ties are used.
MOTION CONTROL & CORONA MITIGATION
Spiral Vibration Damper

Damping devices are designed for the single purpose of reducing vibration.

Spiral Vibration Dampers are designed to reduce Aeolian Vibration in conductors,
generated by wind.

These are manufactured from solid polyvinyl chloride and are helically formed.

These are non corrosive and have surface hardness which does not abrade the OFC.

The gripping part of the SVD should be installed about 100-120 mm away from
other fittings.

One SVD at each end of a span is adequate unless spans exceed 245metre where it
is recommended that two are installed at each end.
CORONA COIL for ADSS
 Corona Coil is installed over the ends of the structural
reinforcing rods. The gripping section secures the unit to
structural reinforcing rods and the coil section encircles the
metallic rod ends, providing electrical shielding.

The design is based on the effective outside diameter of the
cable and while installation the alignment of the rods are kept
in view to be at the center of the coil section and also making
sure that no metallic rods extend beyond the open end of the
coil section. This is critical to the performance of the corona
coil.
CONDUCTOR ACCESSORIES
Bundle Spacer

Bundle Spacer keep the sub-conductors within a span at
designed spacing to avoid damage caused by clashing, twisting
or entwining.

Where motion control is a concern, rigid spacers are used in
conjunction with Stockbridge dampers to give sufficient
damping and spacing results.
T Connector
 T-Connectors are used to join main and tap conductors
mechanically. While used for street lighting in equal spans,
extra poles can be eliminated
Splices – Full Tension

These are designed to restore electrical and mechanical
strengths of existing joints that have been found to develop
abnormally high resistances. The rods perform this function by
shunting current around the installed joint and provide
additional heat radiation surface.
Splices – Repair

Repair Splices are non-tension splices and are used where
some of the outer strands of the conductors are damaged.

The installation restores the strength and conductivity of the
conductor and the split feature eliminates any necessity of
cutting and re-splicing the line.
Lashing Rod


Lashing Rods are helically formed wires to secure
the bearer wire to the service cables.
The number of lashing rods will depend on the
length of the service.
ACCESSORIES FOR HELICAL
FITTINGS
Thimble Clevis made up of ductile iron / aluminium alloy
and acts as a interface connection fitting used in
attaching guy wire, dead ends, insulators and eye bolts.
 Thimbles are intended for providing a minimum bend
radius for installation of dead ends in order to avoid
fatigue failure
 Pulling Eye is designed to facilitate safe, fast installation
of guy-grip dead ends at the anchor rod.
 Guy Guards are secured to guy wires after installation to
protect them from acts of vandalism, accidental contact
with industrial machinery, and intrusion by large wildlife
or domestic animals.

PERFORMANCE PARAMETERS
Resiliency
 Flashover & withstand voltages
 Radio Interference Voltage
 Pull Off Load Tests
 Failure Containment Test
 Electrochemical Test

WORLD OF SUPREME
HELICALS
BIBLIOGRAPHY
www.google.com
 www.wikipedia.com
 EATS 43-15
 EATS 43-91
 EATS 43-92
 BS 3288
 Modern Trends & Practices in Power Sub-Transmission
and Distribution Systems (Vol.1 & Vol.2) – Central Board
of Irrigation & Power
 MS O-17 Tender Book for Yorkshire Electricity
Distribution Ltd

THANK YOU

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