Pole GuyingMore Complicated Than Meets the Eye
NRECA TechAdvantage 2014Presented by
Jason Settle, [email protected]
Pole Guying
Strength of components NESC vs. RUS Guy Factor Grounding
2
Pole Guying
Purpose Support fully loaded design tension of conductors Applied wind and ice load
3
Guy Lead
Guy Attachment Height
Guy Attachment
AnchorPole
Guy
The Components of a Guyed Structure
4
The strength of the guy-anchor assembly is dependent on: Strength of the guy wire de-rated to 90% of the
RBS (NESC Table 261-1) Strength of the guy attachment including the
bolt and washer Strength of the anchor and rod Holding power of the soil in which the anchor is
installed Only as Strong as the Weakest component
5
Guy Hardware
6
Thimble-eye Bolt
7
Johnny Ball & Guy Strain Insulator
8
Guy Wire Strength Data
9
Item MaterialAssembly
E1.1 E1.1L E1.2b Bolt, machine 5/8
(12,400 lbs)3/4
(18,350 lbs)None
d Washer, curved 3 square(7,800 lbs)
4 square(14,200 lbs)
None
v Guy attachment Standard(6,600 lbs)
Heavy Duty(8,500 lbs)
90% of guy wire
y Guy wire 3/8 SM(6,255 lbs)
3/8 HS steel(9,720 lbs)
7/16 SM(8,415 lbs)
Total Guy Strength 6,255 lbs 8,500 lbs 8,415 lbs
RUS Guy Assemblies & Strength
10
11
RUS Standard Washer Allowed Load
RUS standards allow no more than 910 pounds per square inch of compression for washers on wood poles and crossarms.
12
13
14
RUS Standard Distribution Anchor Assemblies
Anchor Type RUS DesignationMaximum Holding Power (lbs)*
ExpandingF1.8 8,000 F1.10 10,000 F1.12 12,000
Screw (Power Installed)
F2.8 8,000 F2.10 10,000 F2.12 12,000
*Maximum Holding Power based on installation in Class 5 Soil
15
Soil Class DescriptionsClass Description
1 Solid rock
2 Dense sand, hard silts, course gravel
3 Compact clay & gravel mixed, shale, hardpan
4 Compacted sand, clay-pan, compacted gravel
5 Loose sand, gravel & clay, compacted course sand
6 Clay loam, damp clay, compacted fine sand, loose course sand
7 Silt loam, loose sand fines, wet clay, miscellaneous fill
8 Swamp, saturated loam, marshland
Types of Soils for Anchor Placement
16
Rating (pounds) 6,000 8,000 10,000 12,000
Item Anchor Rod F1.6 F1.8 F1.10 F1.4
x Anchor RodThimble Eye
5/8 x 7 5/8 x 7 N/A N/A
x Anchor RodTwin Eye
N/A N/A 3/4 x 8 3/4 x 8
z Anchor (sq. in.) 90 100 120 135
Expansion Anchors
17
Expansion (Bust) Anchors
Un-expanded Anchor
Expansion Tool
Illustration courtesy of Hubble Power Systems (Chance)18
Screw Anchors
Double Helix
Single Helix
Illustration courtesy of Hubble Power Systems (Chance)19
20
Spacing of Anchors
5 feet
5-ft for standard duty
8-ft for heavy duty
21
Guying Situations Change in conductor size New wire sagged against old wire Line angles Dead-ends Grade B Crossings Spans that exceed the ruling span by 150% Long crossings
22
Guy & Anchor Selection Depend on:
Horizontal pull at the guy attachment Guy resultant tension in the down guy Soil type in which the anchor is installed Available materials and assemblies
23
Guys Anchors
E1.1 ( 6,255 lbs) F1.6 (6,000 lbs)
E1.1L (8,500 lbs)* F1.8 (8,000 lbs)
E1.2 (9,720 lbs)* F1.10 (10,000 lbs)
Standard Guy and Anchor Assemblies
* 3/8 HS steel
24
Guy & Anchor Grade of Construction
RUS requires Minimum Grade C on distribution Must match highest Grade of construction on pole
Transmission underbuild Grade B Railroad, Limited Access Hwy Grade B
25
Type of Guy Loads
Transverse Forces acting perpendicular to the line
Wind blowing on ice loaded conductors Tension in the wire
Longitudinal Forces acting parallel to the line
Maximum loaded design tension
26
Deadend Guying Calculations
Guy
Hei
ght (
Hg)
A,B
,C
Hei
ght
Neu
tral H
eigh
t
Tension
Guy Lead (Lg)27
Dead-end guyingGh = Mt/Hg
Gh = Horizontal pull at guy attachment
Mt = Sum of moments due to tension in the wire
Hg = Average guy attachment height
NESC construction grade = C NESC loading district = Light
Primary cond. = 1/0 ACSR 6/1, Neutral cond. = 2 ACSR 7/1
Pole height and class = 40 ft, Class 4, SYP
Pole-top assembly = C5.71L (RUS Assembly)
28
*NESC Load factors for deadend guyed structures defined in Rule 250B
Type of Loading Grade BGrade C
Crossing ElsewhereTransverse wind 2.50 2.20 1.75Transverse wire tension 1.65 1.10 1.10
Longitudinal load at dead-ends 1.65 1.10 1.10
*Adapted from NESC Table 253-1, 2012 Edition
29
*NESC Load factors for Extreme Weather when applicable
Type Loading Grade BGrade C
Crossing ElsewhereRule 250 C Extreme Wind
Wind Loads 1.00 0.87 0.87All other loads 1.00 1.00 1.00
Rule 250D Extreme ice with concurrent wind 1.00 1.00 1.00
*Adapted from NESC Table 253-1, 2012 Edition
Applied to NESC 250B load if a structure or its supported facilities exceed 60 feet above ground or water.
30
Conductor Physical Data Transverse Wind
Name Size/StrandDia.(in)
RBS(lb)
Light(lb/ft)
Medium(lb/ft)
Heavy(lb/ft)
Sparate2 ACSR
7/10.325 3640 0.2438 0.2750 0.4417
Raven1/0 ACSR
6/10.398 4380 0.2985 0.2993 0.4660
Penguin4/0 ACSR
6/10.563 8350 0.4223 0.3543 0.5210
Merlin336 ACSR
18/10.684 8680 0.5130 0.3947 0.5613
Transverse Wind Load for 1-ft of Conductor
31
Mt = (Dt Hc Ft)
Mt = Moment due to tension in the wire
DT = Fully loaded design tension
DT = 50% RBS
1/0 ACSR = 0.50(4,380 lbs) = 2,190 lbs
2 ACSR = 0.50(3,640 lbs) = 1,820 lbs
Hc = Height of conductor above grade (RUS C5.71L)
Ft = NESC wire tension load factor = 1.10 (grade C)
Step 1: Moment Due to Tension (Mt)
32
Step 1: Moment due to tension (Mt)
Wire DT(lb) x Hc (ft) x Ft (ft) = Mt(ft-lb)
A-phase 2190 x 32.5 x 1.10 = 78,293
B-phase 2190 x 32.5 x 1.10 = 78,293
C-phase 2190 x 32.5 x 1.10 = 78,293
Neutral 1,820 x 28.5 x 1.10 = 57,057
(Dt Hc Ft) = 291,936
Mt = 291,936 ft-lbs
33
Step 2: Horizontal Pull (Gh)
Hg = Height of guy attachment = 31.75-ft (RUS drawing C5.71L)
Mt = 291,936 ft-lbs
Gh = 291,936/31.75 = 9,195
Gh = 9,195 lbs
HgMtGh
34
Guy Resultant or Total Guy Load (Gr)
LgHgLg
GhGr22
Gr = Guy resultant tension (lbs)
Gh = Horizontal pull at guy attachment (lbs)
Hg = Height of guy attachment (ft)
Lg = Guy lead length (ft)
35
LgHgLg
GhGr22
lbs 13003.6931.75
31.7531.759,195Gr22
Total Guy Load (Gr) = 13,004 lbs
Guy Resultant for Example 1
(Equation Method for 1:1 Guy Lead)
36
Guy Factors
Gf = Guy Factor
Lg = Guy lead length
Hg = Guy attachment height
Hg
Lg
Lg
2Hg2LgGf
37
1.41430230230Gf
1.80320230220Gf
2.23615230215Gf
Guy Factors
30
30
30
1520
30
1 to 1 2 to 3 1 to 2
38
1:1 Guy LeadGf*GhGr
lbs 001,131.414*9,195Gr
Guy Resultant for Example 1
(Guy Factor Method)
lbs 579,161.803*9,195Gr
lbs 560,20236.2*9,195Gr
2:3 Guy Lead
1:2 Guy Lead
39
Guy Leads
Specify and stake adequate guy leads Not based on truck setup
Short guy leads can cause Significant increase in total guy load Pole buckling due to the vertical component of guy
tension
Guy Lead
Buckling
40
Pole Buckling Short Guy Leads
Small Pole Class
Heavy Wire Tension
Specify a larger class pole
41
Guy Lead (ft)
Guy Attachment Height (ft)
30 32 34 36 38 40 42
10 3.16 3.35 3.54 3.74 3.93 4.12 4.32
15 2.24 2.36 2.48 2.60 2.72 2.85 2.97
20 1.80 1.89 1.97 2.06 2.15 2.24 2.33
25 1.56 1.62 1.69 1.75 1.82 1.89 1.96
30 1.41 1.46 1.51 1.56 1.61 1.67 1.72
35 # # # 1.43 1.48 1.52 1.56
40 # # # # # 1.41 1.45
Guy Factors
42
43
Clearance from Guys to Other Conductors
Adapted from NESC Table 235-6
Bare Guy Wire
Insulator Link
Secondary and Neutral 6 inches 4.5 inches
12 kV Primary 6 inches 4.5 inches25 kV Primary 10 inches 7.5 inches
44
Code Violation!
45
Grounding Anchor Guys and Span Guys
Rule 215C2 All anchor guys and span guys shall be effectively grounded.
Only EXCEPTION is to use a guy insulator Fiberglass guy strain insulators Johnny Balls used in the past
Eliminated EXCEPTION for triplex service conductors Guys on secondary poles must be grounded Big change for many utilities Per Bulletin 1724E-153 RUS considers it to be non-
standard construction when guy wires are not effectively grounded.
46
RUS Use of Insulator Links