11
High Voltage Braced High Voltage Braced Insulator Insulator
AssembliesAssemblies Design & ApplicationDesign & Application
Panel Session PN23Panel Session PN23
2008 IEEE Transmission & Distribution 2008 IEEE Transmission & Distribution Exposition & ConferenceExposition & Conference
April 24, 2008 Chicago, ILApril 24, 2008 Chicago, IL
22
High Voltage High Voltage Braced Braced
Insulator Insulator AssembliesAssemblies
Design & ApplicationDesign & Application
A. C. Baker: A. C. Baker: Overview & general Overview & general commentscomments
R. A. Bernstorf: R. A. Bernstorf: Strength ratingsStrength ratings
D. G. Powell: D. G. Powell: Horizontal Vee stabilityHorizontal Vee stability
R. K. Kihara: R. K. Kihara: ConstructionConstruction
33
Armless ConstructionArmless Construction
44
Load Capacity Load Capacity ImprovementImprovement
Maximum Allowable Vertical (Weight) Load
REFERENCES: 1) ANSI C29 STANDARDS, (C29.2, 29.7, C29.12, & C29.17) 2) IEEE STANDARD 987, “IEEE Guide for Application of Composite Insulators” 3) NEMA STANDARD PUB. HV-2, “Application Guide for Ceramic Insulators”
Conventional Vertical String
Horizontal Line Post
Braced Post
Assembly
Porcelain
RTL
( RTL = 0.5 M&E)
RCL
(RCL = 0.4CS)
For α = 45º
For α = 30º Polymer
RTL
(RTL = 0.5 SML)
RCL
(RCL = 0.5 SCL)
.707 RTL .500 RTL
RTL range
RCL range
VMAX
range
7,500 – 25,000 lbs. 650 – 1,900 lbs. 2,500 - 14,000 lbs.
d
d θ
α
55
Braced Insulator Braced Insulator AssemblyAssembly
66
Vertical Load Carrying Capacity vs. Transverse Loading for a Typical 230 kV Horizontal Vee
0
1000
2000
3000
4000
5000
6000
7000
8000
0 500 1000 1500 2000 2500 3000 3500 4000
Horizontal Load H, lbs.
Ver
tical
Lo
ad V
lbs.
230 Kv Horizontal Vee
Post: Max Working Loads Cantilever = 1,000 lbs. Tension/Compression = 7,500 lbs
Brace: Max .Working LoadTension = 12,500 lbs.
77
Unbalanced Unbalanced Longitudinal LoadsLongitudinal Loads
LL1 1 ≠≠ LL22
T = (V sin θ – H cos θ) tan ω
88
Horizontal Vee Horizontal Vee Longitudinal Longitudinal DisplacementDisplacement
L1 L2
99
HorizontalHorizontal Vee Lines Vee Lines • Wind stability limit can be lower than Wind stability limit can be lower than
maximum wind speed usually considered.maximum wind speed usually considered.
• HV assemblies subjected to unbalanced HV assemblies subjected to unbalanced longitudinal loads will be displaced in longitudinal loads will be displaced in direction of higher load.direction of higher load.
• Changes in sag will counteract the Changes in sag will counteract the unbalancing load, establishing new unbalancing load, establishing new equilibrium at each support point.equilibrium at each support point.
• Iterative solution needed.Iterative solution needed.
1010
Horizontal VeeHorizontal Vee Wind Speed Wind Speed StabilityStability Limit Limit
0
50
100
150
200
250
300
350
0 10 20 30 40 50 60 70 80
Number of Spans
Win
d S
tab
ility
Lim
it, k
m/h
r
1111
230 kV Horizontal Vee 230 kV Horizontal Vee LineLine
Ref. INMR Quarterly Review Quarter 1 2004
1212
Rotated Horizontal VeeRotated Horizontal Vee
Ref. INMR Quarterly Review Quarter 1 2004
1313
Braced Post Used as a Braced Post Used as a Longitudinal Restraint Longitudinal Restraint
PointPoint
Ref. INMR Quarterly Review Quarter 1 2004
1414
Tripod Longitudinal Tripod Longitudinal Restraint Restraint AssemblyAssembly
1515
Other Loading Other Loading ConsiderationsConsiderations
• Suspension insulators: tension loads only.Suspension insulators: tension loads only.
• Brace: no compression loadsBrace: no compression loads..
• Polymer posts: combined loading effects Polymer posts: combined loading effects
• Some Porcelain posts designed for Some Porcelain posts designed for tension /compression only. tension /compression only. Do not use for Braced Post Assemblies.Do not use for Braced Post Assemblies.
• Posts : consider buckling strengthPosts : consider buckling strength
• These subjects will be covered in detail in These subjects will be covered in detail in later presentations.later presentations.
1616
Electrical Design Electrical Design • Brace and Post insulator components Brace and Post insulator components must be properly coordinated.must be properly coordinated.
• Individual components must be Individual components must be adequate to withstand the power adequate to withstand the power frequency and impulse electrical frequency and impulse electrical stresses in service.stresses in service.
• Assembly Leakage Distance.Assembly Leakage Distance.
• Assembly Dry Arc Distance.Assembly Dry Arc Distance.
• Manufacturers should be consulted Manufacturers should be consulted concerning need for corona rings.concerning need for corona rings.
1717
SummarySummary • Two types of Braced Insulator Assemblies: Two types of Braced Insulator Assemblies: Braced Posts & Horizontal Vees Braced Posts & Horizontal Vees (fixed or articulated posts)(fixed or articulated posts)
• Different mechanical characteristics.Different mechanical characteristics.
• Braced Posts primarily polymer.Braced Posts primarily polymer.
• Consider Horizontal Vee wind stability limits. Consider Horizontal Vee wind stability limits.
• Longitudinal restraint assemblies can Longitudinal restraint assemblies can increase the wind stability limit for a increase the wind stability limit for a Horizontal Vee line.Horizontal Vee line.
• Installation of some Horizontal Vees may Installation of some Horizontal Vees may require special construction techniques. require special construction techniques.