CIGRE SC B2
Overhead lines
TUTORIAL PRESENTATION ON SPACERS
AND SPACER DAMPERS
by Umberto Cosmai
Convenor WG B2.25
Based on the Technical Brochure TB277 prepared
by Cigre SCB2 WG11WG11-TF5 August 2005
Study Committee B2 - Technical Advisory Group B2-AG-06
Spacer and spacer damper primary task is to
maintain the g
geometry
y of conductor bundles,,
within the design limits, under the normal
service conditions.
Spacer and spacer damper shall withstand the
mechanical
h i l lloads
d iimposed
dd
during
i iinstallation,
t ll ti
maintenance and service, including short circuits,
without failures and without damaging the
conductors.
Study Committee B2 - Technical Advisory Group B2-AG-06
CONDUCTOR BUNDLES
Twin bundles 150
150--500 kV
Spacing: 320320-600 mm
(most used 400400-450450-457mm)
Triple and quad bundles
Voltage: 380380-800 kV
Spacing:
p
g 320320-600 mm
(most used 400400-450450-457mm)
Six and eight conductor bundles
Voltage: 800800-1000 kV
Spacing: 320320-400 mm
(
(most
t used
d 320
320--400mm)
400
)
Study Committee B2 - Technical Advisory Group B2-AG-06
E
Expanded
d db
bundles
dl
850
1450
1450
Used in Russia and Brazil to
increase the power capacity of a
transmission systems
Study Committee B2 - Technical Advisory Group B2-AG-06
900
I relation
In
l i to the
h d
design,
i
spacers can b
be
classified as follows:
Rigid spacers
SemiS i-rigid
Semi
i id spacers
Articulated spacers
p
Flexible spacers
Spacer dampers
Study Committee B2 - Technical Advisory Group B2-AG-06
Rigid spacers
Do not allow any significant relative movements
and displacements of the subsub-conductor
conductor..
Are used in jumper loops (where sometimes are
counterweighted)
t
i ht d) and
d slack
l k spans only.
l
Study Committee B2 - Technical Advisory Group B2-AG-06
Semi--rigid spacers
Semi
Can accommodate small relative movements and static
di l
displacements
t b
between
t
sub
subb-conductors
d t .
Are used in transmission lines in conjunction with
vibration
ib ti d
dampers.
Study Committee B2 - Technical Advisory Group B2-AG-06
Flexible spacers
Allow large relative movements and static
di l
displacements
t b
between
t
sub
subb-conductors.
d t
Are used in transmission lines in conjunction
with vibration dampers.
Study Committee B2 - Technical Advisory Group B2-AG-06
A ti l t d spacers
Articulated
Allow large relative movement and static displacements
b t
between
sub
subb-conductors
d t
i one or more di
in
directions.
ti
Are used in conjunction with vibration dampers.
Study Committee B2 - Technical Advisory Group B2-AG-06
Spacer dampers
Are spacing devices whose inertial, elastic and damping
properties
p
p
are defined and coordinated to mitigate
g
aeolian
vibration.
They can also accommodate relative movements and static
displacements between subsub-conductors in any direction.
Except for special cases, they do not require the
application
li ti off vibration
ib ti d
dampers.
Study Committee B2 - Technical Advisory Group B2-AG-06
SPACER CLAMPS
The spacer and spacer damper clamps are generally made
of primary aluminium alloy. They shall:
Maintain a suitable grip for the whole life of the line and in
the whole range of service temperature.
Avoid any conductor damage during installation and
service.
Be free from Corona and RIV at the maximum line voltage.
Study Committee B2 - Technical Advisory Group B2-AG-06
Be installed without disassembling of any parts
Be designed to minimize the the chance of mis
mis--installation.
Be capable of being safely removed and rere-installed on the
conductors.
Allow installation survey from the ground.
Ensure that individual components will not become loose
in service.
Study Committee B2 - Technical Advisory Group B2-AG-06
Types
yp of spacer
p
clamp
p
Cantilever single-bolted
Nut cracker single
Nut-cracker
single-bolted
bolted
Cantilever single-bolted, rubber-lined
Nut-cracker rubber-lined, with latch fastener
Open clamp rubber lined, with helical rods
O
Open
clamp
l
rubber
bb covered,
d with
ith h
helical
li l rods
d
Nut-cracker spring
p g loaded
Study Committee B2 - Technical Advisory Group B2-AG-06
Cantilever clamp
Study Committee B2 - Technical Advisory Group B2-AG-06
Nut cracker clamp
Study Committee B2 - Technical Advisory Group B2-AG-06
R bb lilined
Rubber
d clamps
l
Cantilever bolted type
NutN t-cracker
Nut
k with
ith llatch
t h
fastener
Study Committee B2 - Technical Advisory Group B2-AG-06
H li ll -attached
HelicallyHelically
tt h d clamp
l
rubber lined type
Study Committee B2 - Technical Advisory Group B2-AG-06
H li ll -attached
HelicallyHelically
tt h d clamp
l
rubber covered type
Study Committee B2 - Technical Advisory Group B2-AG-06
Coil spring loaded clamp
Used mainly in Japan
Study Committee B2 - Technical Advisory Group B2-AG-06
Comparison between cantilever and nut cracker clamps
Study Committee B2 - Technical Advisory Group B2-AG-06
Bolt fasteners
Homogeneous
Bolt and nut, both made of galvanized
steel, or aluminium alloy or stainless
steel.
Heterogeneous
Bolts of galvanized steel, aluminium
alloy and stainless steel
steel, engaged into
a threaded hole of the clamp body.
Study Committee B2 - Technical Advisory Group B2-AG-06
Anti--unscrewing elements
Anti
Energy storing type
Belleville
washer
h
Plain
washer
h
The Belleville washer is a conical spring washer able to
compensate all the clamp relaxation due to, creep, embedment,
cold flow,, etc.
A plain washer is used to support the Belleville washer.
Study Committee B2 - Technical Advisory Group B2-AG-06
Anti-unscrewing elements
Friction types
Plastic
patch
Anti-unscrewing elements such as plastic patches or ring
inserts are used on bolts and nuts to increase the thread
friction
friction.
Study Committee B2 - Technical Advisory Group B2-AG-06
Anti--unscrewing elements
Anti
Locking type
Aluminium or stainless steel “safety
safety plates”
plates of various shapes
can be installed just below the bolt head.
After tightening the bolt, the plate tabs are bent over against
the bolt head to lock it.
it
Study Committee B2 - Technical Advisory Group B2-AG-06
Breakaway bolts and nut
The upper head breaks away at the specified nominal torque.
No torque wrench is required.
Are made in
aluminium alloy or
stainless steel
Best solution
Study Committee B2 - Technical Advisory Group B2-AG-06
In alternative to breakaway bolts, zinc alloy break away
caps can be used on standard bolts
Study Committee B2 - Technical Advisory Group B2-AG-06
Bolt head directed
upward
This solution makes the
installation easier but the
correct tightening of
break--away bolts can not
break
be controlled from the
g
ground
Study Committee B2 - Technical Advisory Group B2-AG-06
Bolt head directed downward
This solution makes the installation more difficult but is
required when breakaway bolts are used
Study Committee B2 - Technical Advisory Group B2-AG-06
Helical rod attachment
The helical rods, usually four per clamp, are made in aluminium
alloy The rods distribute the clamp pressure on a relatively long
alloy.
length of conductor
The rods shall have enough elasticity to apply a suitable grip
and
d tto compensate
t any reduction
d ti off conductor
d t diameter.
di
t
Study Committee B2 - Technical Advisory Group B2-AG-06
S
Spacer
clamps
l
nott properly
l d
designed
i
d and/or
d/ iincorrectly
tl
installed, can get loose under the effect of conductor
vibrations
Conductor abrasion due to a slightly loosen clamp
Study Committee B2 - Technical Advisory Group B2-AG-06
When the looseness increases the conductor strands are
broken by the hammering of the clamp under the effect of
conductor vibrations
Study Committee B2 - Technical Advisory Group B2-AG-06
A heavy clamp may force a vibration node and produce fatigue
failure of the conductor strands at its location
Study Committee B2 - Technical Advisory Group B2-AG-06
SPACER DAMPERS
Study Committee B2 - Technical Advisory Group B2-AG-06
Twin Spacer Dampers
Study Committee B2 - Technical Advisory Group B2-AG-06
Ti l S
Triple
Spacer D
Dampers
Study Committee B2 - Technical Advisory Group B2-AG-06
Q d Spacer
Quad
S
D
Dampers
Study Committee B2 - Technical Advisory Group B2-AG-06
Diamond Spacer Dampers
Study Committee B2 - Technical Advisory Group B2-AG-06
S
Spacer
dampers
d
ffor six
i conductor
d
b
bundles
dl
Study Committee B2 - Technical Advisory Group B2-AG-06
Spacer damper for eight conductor bundles
Study Committee B2 - Technical Advisory Group B2-AG-06
Spacer damper main parts
internal
stop
external
stop
main
frame or
central
frame
articulation
clamp
Study Committee B2 - Technical Advisory Group B2-AG-06
SPACER DAMPER FRAME
The central frame can be made of aluminium alloy, galvanized
steel or cast iron. It shall:
Contain housings for the articulations.
Provide stops for the arm rotation.
Develop suitable inertial forces.
With t d short
Withstands
h t circuit
i it fforces.
Avoids audible noise induced byy the wind.
Study Committee B2 - Technical Advisory Group B2-AG-06
SPACER DAMPER ARTICULATION
The spacer damper articulations contain damping elements
generally made of elastomer.
Most used elastomers are: Chloroprene (Neoprene) rubber,
EPDM rubber, NBR rubber, silicon rubber and special
compounds.
d
Study Committee B2 - Technical Advisory Group B2-AG-06
Elastomers shall:
Have high hysteresis losses.
Withstand the attack of ozone and UV radiation.
M i t i th
Maintain
the properties
ti iin th
the whole
h l range off service
i
temperature.
Maintain the properties for the expected life of the line.
Study Committee B2 - Technical Advisory Group B2-AG-06
In relation to the number of articulations per arm,
spacer dampers can be classified as follows:
Single articulation
Double articulation
The majority of modern spacer dampers are single
articulation
ti l ti ttype.
Study Committee B2 - Technical Advisory Group B2-AG-06
Damping mechanism
The damping mechanism is based on the dissipation of the
subsub
b-conductor
d t vibration
ib ti energy.
The spacer damper extracts energy from the sub
sub--conductors
by means of the elastomer flexibleflexible- damping elements used in
the articulations.
To do that the the spacer damper arms shall rotate allowing
the elastomer to absorb energy by deformation.
Wh th
When
the b
bundle
dl vibrates
ib t with
ith no relative
l ti movements
t b
between
t
sub--conductors, the main frame of the spacer damper shall
sub
develop inertial forces able to determine arm rotations and
consequently dissipation of energy.
Study Committee B2 - Technical Advisory Group B2-AG-06
Inertial reaction
During subsub-conductor aeolian vibrations,
the inertial reaction of the central frame
allow
ll
arm rotation
t ti th
thus di
dissipation
i ti off energy
Study Committee B2 - Technical Advisory Group B2-AG-06
Spacer or spacer damper system
Is the complex of spacer units and the relevant scheme
off distribution
di t ib ti along
l
th
the liline.
The inin-span distribution is the main factor for the control of
sub--span oscillation. Damping capacity although not
sub
detrimental is not required.
The distribution schemes consider unequal subsub-spans
((staggered
gg
scheme)) to avoid transfer of oscillations
between subsub-spans and to limit the number of sub
sub--spans
oscillating simultaneously at a given wind speed.
Study Committee B2 - Technical Advisory Group B2-AG-06
Quad bundles are more prone to oscillate than triple.
Twin and diamond bundles are the least critical.
The maximum subsub-span
p length
g adopted
p
in critical areas is
around 65m.
I non severe conditions
In
di i
sub
subb-span off 80m
80 h
have b
been used
d
without problems.
Expanded bundles are not subjected to subsub-span
oscillations and require less spacers than normal
bundles
bundles.
Study Committee B2 - Technical Advisory Group B2-AG-06
The end sub
sub--spans are kept shorter to prevent their
oscillation (that would damage the hardware) and to increase
the torsional stability of the bundle.
Sh t end
Short
d subsub
b-spans also
l contributes
t ib t marginally
i ll tto th
the
prevention of galloping.
In cold Countries end subsub-spans length of 25
25--35 m are
considered suitable.
In hot Countries end subsub-spans length of 35
35--45 m have
been used.
Study Committee B2 - Technical Advisory Group B2-AG-06
Spacer and spacer damper performance
The spacer dampers control aeolian vibration by means of their
inherent damping capacity.
Aeolian vibration can also be controlled by nonnon-rigid spacers
(semi--rigid, flexible or articulated)and vibration dampers.
(semi
The spacers or spacer dampers control subsub-span oscillation by
means of a suitable inin-span distribution.
Galloping can not be fully controlled by normal spacer and
spacer
p
dampers.
p
Study Committee B2 - Technical Advisory Group B2-AG-06
Spacer dampers equipped with torsional dampers (one or two
per span)
p
p ) are used for controlling
g severe subspan
p oscillations.
A pendulum arm connected to the spacer damper frame
through a damping articulation can control subsub-span oscillation
mitigating the torsional vibration modes of the bundle
Study Committee B2 - Technical Advisory Group B2-AG-06
Spacer dampers equipped with detuning pendula are used for
controlling
gg
galloping.
p g
Detuning pendula applied on spacer damper frames also
improve the performance of these devices in controlling
aeolian vibrations and sub
sub--span oscillations
oscillations.
Study Committee B2 - Technical Advisory Group B2-AG-06
I
International
i
l standard
d d and
d publications
bli i
relevant
l
to
spacers and spacer dampers
IEC 61854 St
Standard
d d 1998
1998--09
Overhead lines - Requirements and tests for spacers
CIGRE Technical brochure TB277 - August 2005
Prepared by SCB2 WG11WG11-TF5
State of the art survey on spacer and spacer dampers
Part 1 General description
Part 2 Technical aspects
P t3C
Part
Currentt practice
ti
EPRI - Transmission Lines Reference Book
Wind Induced Conductor Motion - 2009
Study Committee B2 - Technical Advisory Group B2-AG-06