A mini project on the transmission tower

A MINI PROJECT ON THE

TRANSMISSION TOWER

PRESENTED BY:-

ATUL YADAV

MUKESH RANJAN SINGH

NAQEEB KHAN

NAVEEN KUMAR

ELECTRICAL DEPARTMENT

FINAL YEAR,BBDU

1

INTRODUCTION

NAMING

"Transmission tower" is the name for the structure used in the industry in the United Kingdom, United States, and other English-speaking countries. The term "pylon" comes from the basic shape of the structure, an obelisk-like structure which tapers toward the top, and is mostly used in the United Kingdom and parts of Europe in everyday colloquial speech. This term is used infrequently in the United States, as the word "pylon" is commonly used for a multitude of other things, mostly for traffic cones.

2

TRANSMISSION TOWER

A Transmission tower is a tall structure, usually a

steel lattic tower, used to support an overhead

power line.

They are used in high-voltage AC and DC systems,

and come in a wide variety of shapes and sizes.

Typical height ranges from 15 to 55 metres (49 to

180 ft), though the tallest are the 370 m (1,214 ft)

towers of a 2700-metre-long span of Zhoushan

Island Overhead Powerline Tie

3

ON THE BASIS OF CURRENT

TYPES OF TOWER

1. HVAC TRANSMISSION TOWER.

2. HVDC TRANSMISSION TOWER.

3. RAILWAY TRACTION LINE TOWER.

4. TOWER FOR DIFFERENT TYPE OF

CURRENT.

4

HVAC TRANSMISSION

TOWER Three phase electric power systems are used for high

voltage (66 or 69 kV and above) and extra-high voltage

(110 or 115 kV and above; most often 138 or 230 kV

and above in contemporary systems) AC transmission

lines.

The towers must be designed to carry three(or multiples

of three) conductors.

The towers are usually steel lattices or

trusses (wooden structures are used

in Canada,Germany, and Scandinavia in some cases)

and the insulators are either glass or porcelain discs.

5

HVDC TRANSMISSION TOWER

HVDC transmission lines are either monopolar or bipolar systems.

With bipolar systems a conductor arrangement with one conductor on each side of the tower is used.

For single-pole HVDC transmission with ground return, towers with only one conductor can be used.

The towers are designed for later conversion to a two-pole system. In these cases, often conductors on both sides of the tower are installed for mechanical reasons.

6

RAILWAY TRACTION LINE

TOWER Towers used for single-phase AC railway traction

lines are similar in construction to those towers used for 110 kV-three phase lines.

Steel tube or concrete poles are also often used for these lines.

The towers of railway traction lines carry two electric circuits, so they have four conductors.

Each circuit occupies one half of the cross arm. For six electric circuits arrangement of the conductors is in three levels.

7

TOWER FOR DIFFERENT

TYPE OF CURRENT Line carry both AC and DC power circuits. One set of

towers is near the HVDC Volgograd-Donbass on Volga Hydroelectric Power Station. The other are two towers south of Stenkullen, which carry one circuit of HVDC Konti-Skan and üne circuit of the three-phase AC line Stenkullen-Holmbakullen.

Towers carrying AC circuits and DC electrode lines exist in a section of the powerline between Adalph Static Inverter Plant and Brookston the pylons carry the electrode line of HVDC Square Butte.

The overhead section of the electrode line of Pacific DC Intertie from Sylmar Converter Station to the grounding electrode in the Pacific Ocean near Will Rogers State Beach is also installed on AC pylons

8

ON THE BASIS OF LINE

SUPPORT TYPES OF TOWER 1. WOODEN POLES

2. RCC POLES

3. STEEL TUBULAR POLES

4. STEEL TOWERS

The supports for an overhead line must be capable of carrying the load due to:

Conductors

Insulators

Wind load on the support itself.

9

WOODEN POLES

Made of chemically treated wood.

Used for distribution lines especially in

areas where good quality wood are

available.

Very economical but susceptible to decay.

To protect from decay,poles have zinc or

aluminium cap at the top and Bitumen

coating at the bottom.

10

RCC POLES

Made of reinforced concrete cement.

Stronger than wood poles but more costly.

Very long life and need little maintenance.

Bulky and heavy.

Widely used for distribution lines upto 33kV.

Can be manufactured at site.

11

STEEL TUBULAR POLES

Stepped pole manufactured from a single

tube , the diameter being reduced in

parallel steps.

More costly than RCC and wood poles.

Have light weight , high strength to weight

ratio and long life.

Widely used for lines upto 33kV.

12

STEEL TOWERS

Used for lines of 66kV and above.

Very long life and high degree of reliability.

Can withstand very severe weather

conditions.

Overhead HV, EHV and UHV lines mostly

use self supporting steel towers.

13

TYPES OF TOWER ON THE

BASIS OF LINE DIVERSION Type A Tower (Tangent Tower with suspension string)

o Used on straight runs and up to 2° line diversion

Type B Tower (Small Angle Tower with tension string)

o Used for line deviation from 2° to 15°

Type C Tower (Medium Angle Tower with tension string ).

o Used for line deviation from 15° to 30°.

Type D Tower (Large angle tower with tension string)

o Used for line deviation from 30° to 60°

Type E Tower (Dead End Tower with tension string)

o Used for line termination & starting

Special tower-

Suspension Tower (Span ≈ 1000 m)

o Used for River crossing, Mountain crossing etc.

Transposition Tower

o Used for transposition of tower

14

DIFFERENT TYPES OF TOWER

15

Selection of Tower Structure

Single circuit Tower/ double circuit Tower.

Length of the insulator assembly.

Minimum clearances to be maintained between ground

conductors, and between conductors and tower.

Location of ground wire/wires with respect to the

outermost conductor.

Mid-span clearance required from considerations of the

dynamic behavior of conductors and lightning protection

of the line.

Minimum clearance of the lowest conductor above ground

level.

16

Tower Design

Tower height

Base width

Top damper width

Cross arms length

17

Height of Tower Structure

18

4321 hhhhH

Height of tower is determine by-

h1=Minimum permissible ground

clearance

h2=Maximum sag

h3=Vertical spacing between conductors

h4=Vertical clearance between earthwire

and top conductor

19

Determination of Base Width

The base width(at the concrete level) is the distance

between the centre of gravity at one corner leg and

the centre of gravity of the adjacent corner leg.

A particular base width which gives the minimum total cost of the

tower and foundations.

The ratio of base width to total tower height for most towers is

generally about one-fifth to one-tenth.

Ryle

Formula

Spacing and Clearances

20

Ground Clearances

KCL *305.0182.5

33

33VKWhere-

S.No. Voltage level Ground

clearance(m)

1. ≤33 KV 5.20

2. 66 KV 5.49

3. 132KV 6.10

4. 220 KV 7.01

5. 400 KV 8.84

Minimum permissible ground clearance as per IE Rules,

1956,Rule 77(4)

21

Clearance for PowerLine Crossings

Crossing over rivers:• 3.05m above maximum flood level.

Crossing over telecommunication lines• Minimum clearances between the conductors of a power

line and telecommunication wires are :-

Voltage Level Minimum

Clearance(mm)

≤33 KV 2440

66KV 2440

132 KV 2740

220 KV 3050

400 KV 4880

22

Power line Crossing over railway tracksunder maximum sag condition minimum clearance over rail level

stipulated in the regulations for Electrical Crossings of Railway Tracks,

1963

Table. For un-electrified tracks or tracks electrified on 1,500 volts D.C.

system

System Voltage

Level

Broad Gauge Meter & Narrow

Gauge

Inside station

limits(m)

Out side

station

limits(m)

Inside

station

limits(m)

Out side

station

limits(m)

≤66 KV 10.3 7.9 9.1 6.7

132 KV 10.9 8.5 9.8 7.3

220 KV 11.2 8.8 10.0 7.6

400 KV 13.6 11.2 12.4 10.0

23

Spacing Between Conductor(Phases)

1) Mecomb's formula

2) VDE formula

SW

DVcmSpacing 010.43048.0)( *

Where-

V= Voltage of system in KV

D= Diameter of Conductor in cm

S= Sag in cm

W= weight of conductor in Kg/m

20005.7)(

2

VScmSpacing Where-

V= Voltage of system in KV

S= Sag in cm

24

3) Still's formula

8.27

2

*814.108.5)(l

VcmSpacingWhere-

l = Average span length(m)

4) NESC formula

2681.3*762.0)(

LSVcmSpacing

Where-

V= Voltage of system in KV

S= Sag in cm

L= Length of insulator string in cm

25

5) Swedish formula

EScmSpacing *7.05.6)(

Where-

E= Line Voltage in KV

S= Sag in cm

6) French formula

5.10.8)(

ELScmSpacing

Where-

E= Line Voltage in KV

S= Sag in cm

L= length of insulating string(cm)

26

Offset of conductors (under ice-loading conditions)

Sleet Jump:

The jump of the conductor, resulting from ice dropping

off one span of an ice-covered line, has been the cause of many

serious outages on long-span lines where conductors are

arranged in the same vertical plane.

Offset in cm = 60 + Span in cm / 400

Clearances b/n Conductors

27

SYSTEM

VOLTAG

E

TYPE OF

TOWER

Vertical spacing

b/n

conductors(mm)

Horizontal spacing

b/n

conductors(mm)

66 kV

SINGLE

CIRCUIT

A(0-2°) 1080 4040

B(2-30°) 1080 4270

C(30-60°) 1220 4880

DOUBLE

CIRCUIT

A(0-2°) 2170 4270

B(2-30°) 2060 4880

C(30-60°) 2440 6000

132 KV

SINGLE

CIRCUIT

A(0-2°) 4200 7140

B(2-30°) 4200 6290

C(30-60°) 4200 7150

D(30-60°) 4200 8820

DOUBLE

CIRCUIT

A(0-2°) 3965 7020

B(2-15°) 3965 7320

C(15-30°) 3965 7320

D(30-60°) 4270 8540

28

220 kV

SINGLE

CIRCUIT

A(0-2°) 5200 8500

B(2-15°) 5250 10500

C(15-30°) 6700 12600

D(30-60°) 7800 14000

DOUBLE

CIRCUIT

A(0-2°) 5200 9900

B(2-15°) 5200 10100

C(15-30°) 5200 10500

D(30-60°) 6750 12600

400 KV

SINGLE

CIRCUIT

A(0-2°) 7800 12760

B(2-15°) 7800 12760

C(15-30°) 7800 14000

D(30-60°) 8100 16200

Sag and Tension Calculation

29

Parabolic formula: Catenary formula:

Span >300 mSag & TensionSpan ≤300 m

Corona

Visual corona voltage in fair weather condition is given by-

V0= corona starting voltage, KV(rms).

r= radius of conductor in cm.

D= GMD equivalent spacing b/n conductors in cm.

m= roughness factor.= 1.0 for clean smooth conductor

=0.85 for stranded conductor30

r

Dn

r

rmV log

)3.01(1.210

31

Voltage gradient at the surface of conductor at operating

voltage :-

r

DLog

V

n

g 30

Corona discharge form at the surface of conductor if g0≥

corona starting gradient i.e.

rrmg

)3.01(1.21

0

(rms kv/cm)

Conductor size will be so chosen that normal gradient of

conductor should not exceed 17.5 KV/cm.

For EHV transmission line 400KV and above use bundle

conductor from point view of corona.

Erectiona) Setting of stubs:

Template

B/B & diagonal at Template top

B/B & diagonal at stub top Ram bus shape

Stub cleats with B&N 2 each

Extra cleats to avoid failure of foundation due

to tower falling.

Threads to bisect

LP&AP

Template height at centre point & joining of 2

threads

Probe setting

b) After 14 days of curing

Built-up method:- This method consist of erection of

towers member by member. The 4 main leg members of first

section of the tower are first erected and guyed of. The cross

braces then assembled. For assembling second section a light

gin pole is placed on top of the corner legs for raising the

second section of the tower. Afterwards the gin pole is shifted

to top of second section leg to raise third section this process

is continued till complete tower is erected.

Section method :-

Major sections of the tower are assembled on the ground and same are erected as units.

Either mobile crane or gin pole of 10m long is used.

Ground assembly(Proto) :-

This method consist of assembling the tower on ground

and erecting it as a complete unit. The complete tower is

assembled in line wise position to allow Xarms to fitted.

After assembly is completed tower is picked up from

ground with the help of crane and carried to is location and

set on its foundation.

This method is not is useful when the towers are large

and heavy and the locations are difficult.

HELICOPTER METHOD

In this method the tower is erected in section.

Bottom section is first lifted on to the stub and

then the upper section is lifted and bolted to

first section and the process is repeated till the

tower is erected. Some times complete

assembled tower is raised with the help of

helicopter. This method is adopted when

approach is impossible

Helicopter Method.

TIGHTENING OF BOLT AND

NUT The bolts & nuts are used to join the tower parts.

The bolts are of 16mm diameter and 20mm diameter

The length of bolts are various from 35mm to 80mm multiple

of 5mm.

17.5mm/21.5mm dia hole is provided on tower part for fixing

bolt & nut.

Spring washers - 16 x 3.5 mm- to tighten the bolt & nut

Flat washers 4, 5, 6, 8, 10,20 and 25mm to fill up gaps

between the tower parts.

Check for tight of B&N using torque wrench.

37

TIGHTENING OF BOLT AND

NUT The threads of bolts projecting out side shall be

punched at 3 positions and do half round welding to

ensure that nuts are not loosened in course of time

and avoid theft of angles.

Zinc epoxy painting is applied on welded portion to

avoid rusting.

38

TOWER ACCESSORIES

Danger boards.

Number plate.

Phase plate.

Anti Climbing Device.

Step bolts 16x175 mm.

Antiperch / Bird guards for suspension towers.

Hanger rods.

39

GENERAL STEPS TO BE

FOLLOWED FOR TOWER

ERECTION NO TOWER SHALL BE ERECTED ON FOUNDATION BEFORE 10

DAYS AFTER CONCRETING.

CHECK THE CORRECTNESS OF DIAGONAL AND LEVEL OF

THE STUB OF THE FOUNDATION.

TOWERS ARE TO BE ERECTED AS PER ERECTION DRAWING

ASSEMBLY OF TOWER PARTS SHALL BE MADE AS PER MARK

NUMBER WISE ENGRAVED ON THE TOWER MEMBER

CORRESPONDING TO NUMBER IN THE ERECTION DRAWING.

SPECIAL CARE SHALL BE TAKEN IN SELECTION OF MARK

NUMBER FOR TRANSVERSE AND LONGITUDINAL FACE OF

THE SQUARE BASE TOWER.40

GENERAL STEPS TO BE

FOLLOWED FOR TOWER

ERECTION ANY BUCKLING, DAMAGE TO STEEL MEMBER, DAMAGE TO

GALVANIZING SHALL BE AVOIDED

NO MEMBER SHALL BE SUBJECTED TO UNDUE STRESS.

REASON CAN BE: (i) DEFECTIVE FABRICATION.

(ii) DEFECTIVE FOUNDATION.

(iii) DEFECTIVE ERECTION METHOD.

COLLECT MATERIAL FROM STORE TALLYING WITH BOM.

PREFERABLY TRANSPORT COMPLETE TOWER OR COMPLETE

SECTION.

THE TOWER MEMBER AT LOCATION SHALL BE KEPT ON GROUND

SERIALLY ACCORDING TO THE NEED FOR FOLLOWING UP ERECTION

SEQUENCE.41

TOWER ERECTION

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

CROW BARS

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

CROW BARS

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

CROW BARS

DERRICK

DERRICK TYING ROPE

20mm POLYPROPYLENE

ROPE

CROW BARS

Tower Grounding

Used to reduce earth wire potential and stress on

insulators at the time of stroke and also for

safety.

Tower footing resistance will be 10Ω and should

not be more than 20 Ω under any condition

throughout the year.

Earth resistance depend upon soil

resistivity(general 100 Ω-m).

43

Method of Tower Grounding

44

Buried Conductor

One or more conductor are connected to tower lags and buried in back filled of tower foundation.

o Used where soil resistivity is low

Counterpoise Wire

A length of wire/ Strip of 50 m is buried horizontally at depth of 0.5 m below ground. This wire is connected to tower lags.

o Used when earth resistance is very high and soil conductivity is mostly confined to upper layer)

Rod Pipe

Pipe/Rod of 3 to 4 m is driven into ground near the tower and top of rod is connected to tower by suitable wire/strip

o Used where ground conductivity increase with depth

Treated Earth Pits

Pipe/Rod of 3 to 4 m are buried in treated earth pits and top of rod is connected to tower by suitable wire/strip.

o Used in very high resistivity near tower

Tower Grounding

45

SAFETY OF TOWER ERECTION

46

47

While Loading And Unloading The Tower Parts,

Care Should Be Taken For Stacking

Systematically.

Handle The Tower Parts Carefully. While Handling

Them Wear Suitable Gloves.

Establish Clear Signal/Communication Between

The Persons Working On The Top And The People

Supplying Tower Parts, Watching Guys Pulling Etc

Special Care Shall Be Taken For R.C. Tower.

All Lifting Tools And Tackles Should Be Load

Tested As Per Standard.

48

Ensure The Derrick Used Before Tower Erection

Has Been Checked For Adequate Strength / Size.

Keep Watch On All Guys Used During Erection

Any Slippage/Failure If The Guy Can Cause

Accident.

After 5 Operations Check The Condition Of The

Rope. If Worn Out Then Reject.

Avoid All Tower Erection In Rainy Day.

Heavily Cloudy Days Avoid All Type Tower

Erection. Stop Tower Erection Of R.C.Tower.

EFFECT OF LINE

49

EFFECT ON HUMAN BEING

SHORT TERM HEALTH PROBLEM

Headaches.

Fatigue.

Insomnia.

Prickling and/or burning skin.

Rashes.

Muscle pain.

50

EFFECT ON HUMAN BEING

LONG TERM HEALTH PROBLEM

Risk of damaging DNA.

Risk of Cancer.

Risk of Leukemia.

Risk of Neurodegenerative Disease.

Risk of Miscarriage.

51

EFFECT ON ANIMALS

Many researchers are studying the effect of

Electrostatic field on animals. In order to do

so they keeps the cages of animals under

high Electrostatic field of about 30 kV/m.

The results of these Experiments are

shocking as animals (are kept below high

Electrostatic field their body acquires a

charge & when they try to drink water, a

spark usually jumps from their nose to the

grounded Pipe) like Hens are unable to pick

up grain because of chattering of their

beaks which also affects their growth.52

EFFECT ON PLANTS

High power transmission lines affects the growth of

plants.

Physiological parameter was primarily due to the

effect of reduced cell division and cell enlargement.

From various practically study it was found that the

response of the crop to EMF from 110 KV and 230

KV Power lines showed variations among

themselves. Based on the results the growth

characteristics like shoot length, root length, leaf

area, leaf fresh weight, specific leaf weight,

shoot/root ratio, total biomass content and total

water content of the four crop plants were reduced

significantly over the control plants.

53

EFFECTS ON VEHICLES

PARKED NEAR LINE

When a vehicle is parked under high voltage

transmission line an electrostatic field is

developed in it. When a person who is

grounded touches it a discharge current

flows through the human being. In order to

avoid this parking lots are located below the

transmission lines the recommended

clearance is 17 m for 345 kV and 20 m for

400 kV lines.

54

Reference Standards

55

IS-398

IS-802

IS 3853

IS 4091

IS 5613

CBIP

IE Rules, 1956

Specification of Aluminium Conductor for Over Head

Transmission Line(ACSR)

Code of Practice for use of Structural Steel in over head

Transmission Line Tower

Specification of Aluminium Steel Core Wire for Aluminium

Conductor

Code Practice for Design and Construction of Foundation of

Transmission Line Tower and Pole

Specification of Design, Installation and Maintenance of Line

above 11 KV and up to 220 KV

Manual on Transmission Line Tower, Technical Report N0. 9,

March 1977

56

THANK YOU