INSULATED CROSS-ARM
AND
WORLDWIDE EXPERIENCE OF COMPACT LINES
Dimensional diagram for a conventional HV line.
Schematic of two-pole 115-kV compact line design with shield wires
removed and MOV-type lightning arrestors installed as required.
Typical compact configurations
Rigid (left) and Pivoted(right) insulated
cross-arm(schematic view)
Testing of a 420 kV insulated cross-arm
Deformation of the insulated cross-arm with
increasing load F res
Pictures of the world’s first ever 400 kV
compact lines with composite insulators
Emergency restoration systems with insulated cross-arms
with re-arrangement of the quad bundle
420 kV compact line (under conductor tension) next to the existing
conventional 420 kV line, right of the image the city motorway, in the
background the skyline of Dubai
Countries conducted studies on compact line design
Spain:
IBER-DUERO, S.A. carried out a study to optimize line design of a short length of 2.34km of a 132kV
transmission line. Composite insulators were considered to form a rotary cross-arm where a rigid column
insulator was placed horizontally working in tension and a long rod composite insulator used as a tie-bar
working in tension. Both were joined to form an apex from which conductor clamp is suspended. The other
ends of both insulators were fixed to the tower by universal joints to allow rotation of the cross-arm about an
inclined axis in case of broken wire condition.
Italy:
ENEL conducted studies to determine limits of line compaction. Rotating insulator cross-arms were considered.
France:
EDF carried out studies to develop methods for design of compact high voltage lines at 90kV. An experimental
line of 1200m was built to study the feasibility of various compaction techniques. Composite insulators were
adopted for insulated cross-arms to form both rigid and pivoted types.
Japan:
Studies and extensive tests were carried out to develop polymeric inter-phase spacers for 66kV transmission
lines to find effective means for dealing with conductor galloping under ice loading. Inherent flexibility of
polymeric composite insulators helps in attenuating vibrations of conductors during galloping.
Utilities’ contribution in development of compact lines
 Puget Energy, North America – 230kV Compact line.
 BPA, USA – 43.1km line upgrading from 115 to 230kV.
 PacifiCorp(Utah), USA – 46 to 138kV and 220 to 345kV upgrading.
 Otter Tail Power Company, USA – 41.6 to 115kV upgrading.
 Niagra Mohawk(now National Grid), USA – 115kV test spans of compact line.
 Manitoba Hydro, Canada – 115 to 230 kV upgrading.
 Ontario Hydro, Canada – 115 to 230 kV upgrading & new 230kV compact
line.
 COPEL, Brazil – 138 and 230 kV compact lines.
 Queensland Electricity Commission, Australia – 275 kV compact line.
PUGET ENERGY 230kV Compact Line
BPA, USA – 43.1km line upgrading
Comparison of original 115kV and upgraded 230kV line
Original 115kV Line
Upgraded 230kV
Line
Right-of-way width
30.5m
30.5m
Conductor
ACSR Dove
ACSR Dove
Insulators
I-string – all 3 phases
V-string – Centre
phase
Strut – Outer phases
No of units
6
9
Structure
H-Frame, wood pole
H-Frame, wood pole
Phase Spacing
3.66m
3.66m
Horizontal Post Insulator Cross-arm
PacifiCorp(Utah) 46 to 138kV
230/345-kV upgraded wood pole line next
to conventional 345-kV line PacifiCorp(Utah)
230-kV structure prior to conversion
PacifiCorp(Utah)
345-kV design after conversion from 230 kV
PacifiCorp(Utah)
Midspan spacers used on test line
Otter Tail 41.6 to 115kV Upgrading
115-kV uprated structure with line arrester
Otter Tail Power Company
Manitoba Hydro Existing 115kV & Upgraded
230kV Line
Ontario Hydro’s compact and conventionaldimensioned 230-kV lines
COPEL’s 138-kV compact line
COPEL’s 230-kV compact line
Insulated Cross arm
Integrated model showing all concepts of compact
line (IPS, EGLA, ICA, HTLS and ABC)
ACKNOWLEDGEMENT
 Acknowledgement is expressed to EPRI, USA.
 Reference and Photographs extracted for presentation from
EPRI Transmission Line Reference Book – 115-345kV
Compact Line design and Book on Silicon Composite
Insulators by K. Papailiou et. al.
 Regards and Thanks to all associates
THANK YOU