Pole GuyingMore Complicated Than Meets the Eye

NRECA TechAdvantage 2014Presented by

Jason Settle, P.E.jason.settle@gdsassociates.com

Pole Guying

Strength of components NESC vs. RUS Guy Factor Grounding

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Pole Guying

Purpose Support fully loaded design tension of conductors Applied wind and ice load

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Guy Lead

Guy Attachment Height

Guy Attachment

AnchorPole

Guy

The Components of a Guyed Structure

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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

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Guy Hardware

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Thimble-eye Bolt

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Johnny Ball & Guy Strain Insulator

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Guy Wire Strength Data

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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

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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.

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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

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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

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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

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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

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Spacing of Anchors

5 feet

5-ft for standard duty

8-ft for heavy duty

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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

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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

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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

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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

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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

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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)

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*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

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*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.

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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

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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)

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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

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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

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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)

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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)

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Guy Factors

Gf = Guy Factor

Lg = Guy lead length

Hg = Guy attachment height

Hg

Lg

Lg

2Hg2LgGf

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1.41430230230Gf

1.80320230220Gf

2.23615230215Gf

Guy Factors

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30

30

1520

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1 to 1 2 to 3 1 to 2

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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

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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

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Pole Buckling Short Guy Leads

Small Pole Class

Heavy Wire Tension

Specify a larger class pole

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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

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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

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Code Violation!

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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.

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RUS Use of Insulator Links