designing 400 kv transmission line

: قال تعالى

Al‐Balqa’ Applied University

Faculty of Engineering TechnologyFaculty of Engineering TechnologyJanuary 2011

I i l F lfill f h R i f h D f B h l fIn partial Fulfillment of the Requirements for the Degree of Bachelor of

Science in Engineering Technology

DESIGNING 400 kV TRANSMISSION LINEDESIGNING 400 kV TRANSMISSION LINE

Supervisor:

Dr.Ibrahim Abu‐Harb P d BPrepared By

AmmarAmerAbu_Khaled MohammedK.Hawa

Na’elAli Nofal

CONTENT INTODUCTION TO TRANSMISSION SYSTEM.

TRANSMISSION LINES.

ELECTRICAL AND MECHANICAL DESGIN OF OHTL.

CALCULATIONS AND MATLAB FILES.

INTRODUCTION TO TRANSMISSION SYSTEMSYSTEM

Jordanian Transmission system

•The figure represents the Jordanian map with the 132kV national grid and 400 kV interconnection 4network.

Jordanian Transmission system

Elements of design•Designing 400 kV systems is a difficult job because there are many factors should be taken in mind when the designing engineers start the designing proceduredesigning procedure.•These factors depend on the system standards, economical funds for the line and availability of technical and professional persons.

• Most important factors are:

•Type of conductors•Type of conductors.•Type of towers.•Type of insulators.yp•Clearance factor.•Sag and tension.•Spacing between conductors•Spacing between conductors

I J d th i id th i l d t ll th t hi h f d thIn Jordan there is a rapid growth in loads at all the country which forced the electrical transmission company (NEPCO) to construct new lines to feed that loads with the electrical power.

shows the peak load development in Jordan

Th fi b l h th t f ti f ll l tThe figure below shows the percentage of power generation for all power plants In the Jordanian Electrical system

TRANSMISSION LINES TRANSMISSION LINES

Single and Double circuits for 400 kV

Single Circuit Double Circuit

Structures may have one of the three basic configurations: horizontal, vertical, orStructures may have one of the three basic configurations: horizontal, vertical, or delta, depending on the arrangement of the phase conductors.

Fig (2‐1) Lattice towers

The main types of towers are used in designing transmission lines:

•SUSPENSION TOWER:Most of transmission lines towers are of this type (about 80%)

•TENSION TOWERS:

This type of towers is used to carry power lines, Two main types are used:•Tension towers with small angles (less than 20º)Tension towers with small angles (less than 20 ).•Tension towers with large angles (less than 65º).

•TERMINAL TOWERS:Starting and end lines towers are the two types of terminal transmission lines towers, it i t i tit is a tension tower

•CROSSING TOWERS:Usually this type is used for crossing rivers, valleys and wide high ways.

OVERHEAD OVERHEAD LINESLINESLINES LINES CONDUCTORSCONDUCTORSCONDUCTORSCONDUCTORS

Types of conductorsTypes of conductors

1) ACSR (Aluminum Conductor Steel-Reinforced):1) ACSR (Aluminum Conductor Steel-Reinforced):

ACSR is the most common type f d d dof conductor used today

2) AAC All Aluminum Conductors:

AAC conductors are most useful whereAAC conductors are most useful where electrical loads are heavy and wherespans are short and mechanical loads

l AAC d fare low so AAC are used for power distribution.

BUNDLE CONDUCTORS

Two conductor/phase Four conductor/phase

Earth Wire A ground conductor is a conductor that is usually grounded (earthed) at the

top of the supporting structure to minimize the likelihood of direct lightningstrikes to the phase conductorsstrikes to the phase conductors.

The ground wire is also a parallel path with the earth for fault currents inearthed neutral circuits, Very high-voltage transmission lines may have twoground conductors.

The ground conductors not only used to protect the lines from the lightning strikes but also contain a fiber optic, used for communications and remote control

of power systemp y

The ground wire that used in 400kV transmission system isOptical Ground Wire (OPGW)Optical Ground Wire (OPGW).

OPGW has three main types

1) Stainless steel loose tube type OPGW.

22)) NonNon--metallic loose tube type OPGW. metallic loose tube type OPGW.

33)) Aluminum spacer type OPGW.Aluminum spacer type OPGW.)) p ypp yp

Types of insulators1) Tension insulators:

usually they are used when h i h 6the span is more than 360m

2) Suspension insulators:usually they are used if the span between tower is 360 m or less, and with heavy conductors.

3) Ground Wire InsulatorsThe ground wire insulators are used to suspend theThe ground wire insulators are used to suspend theoverhead ground wires on the high-voltage transmission lines.

Materials of InsulatorMaterials of InsulatorA) Porcelain.

) h d l l

has a mechanical strength and a high electrical insulationits demerit that it is hard to detect the damage on it.

B) Toughened Glass Insulators.•It Has a high electrical insulation as porcelain insulators•Its advantage that it does not affected by the thermal g ystresses,• it is susceptible to breakage and more expensive than porcelain

C) Polymer Insulators•It has a light weight and it still very long time without polluting with dust.•But it may be damaged by corona effect, or physical deterioration which may not be apparent.

ELECTRICAL AND MECHANICAL DESIGN OF OHTLDESIGN OF OHTL

Electrical Mechanical parameters parameters

Electrical parameters

Line resistance

Line Inductance

LineCapacitanceresistance Inductance p

Resistance: Conductor resistance is affected by these factors:‐

Frequency (‘skin effect’)

Resistance: Frequency ( skin effect ) Temperature The material of conductorThe material of conductor

The direct current resistance of a conductor is given by:

ρL ρ: Conductor resistivity, Ω.m

ΩA

ρLR DC L : Conductor length, m.A : Cross sectional of conductor area, m2.

Th l i i f d i i bThe alternating current resistance of a conductor is given by:

)1(RACR sypyDC Ys : skin effect factorYp : proximity factorAC spDC Yp : proximity factor

The conductor resistance increases as temperature increases. As in this equation:tTR 2

tTtT

RR

1

2

1

2

O

O

I d t f d bl i it f th h liInductance of double circuit of three phase line

We use the following equations to find the g qGMD between each phase group

4

22122111

422122111

cbcbcbcbBC

babababaAB

DDDDD

DDDDD

422122111

22122111

cacacacaAC

cbcbcbcbBC

DDDDD

The equivalent GMD per phase is

)**(eg 3ACBCAB DDDDGMD

Double circuit configuration

The equivalent GMR per phase is

)(

)(2b

214 2

21b

b

aab

aaSSA

DDDDD

DDDDDS

)(

)(

214 2

21b

214 2

21b

ccb

ccSSC

bbbSbbSB

DDDDD

DDDDDS

)( 2121 ccccSSC S

Where is the GMR of bundled conductors (D b=0 7788*r)bSDWhere is the GMR of bundled conductors (Ds =0.7788 r)

, and Ds is the GMR of the individual conductors. S

The equivalent GMR :

The inductance per-phase is

The equivalent GMR :

mHGMRGMDL x /ln102 7

GMR L

Capacitance of double circuit of three phase lineThe GMRc of each phase is similar to the GMRL, with the exception that (rb)is used instead of (Ds

b ).This will result the following equations:

b Drr

21

21

bbb

B

aaA

Drr

Drr

3CBAC rrrGMR

21

21

ccb

C

bbB

Drr

Drr

The per‐phase equivalent capacitance to neutral is obtained by:

/l

2 0 mFGMDC

lnGMRGMD

c

The equivalent circuit of short transmission line The equivalent circuit of short transmission line

The sending end voltage of line is : IZVV The sending‐end voltage of line is :RlineRS IZVV

The sending‐end current and receiving –end is: II The sending end current and receiving end is:RS II

We can represent the line constants as matrix:p

rs VBAV A=D= 1

B= Zline

rs IDCI

lineC= 0

CORONA DETERMINATIONF Aff CFactors Affect on Corona: Atmosphere C d i Conductor size Spacing between conductors Line voltage

Dielectric strengthgdepends on:

h h i

h

the atmospheric temperature . The atmospheric pressure.

273

92.3t

b

Where:b: Atmospheric pressure (mm Hg).t : Atmospheric temperature (0C)273 t t : Atmospheric temperature ( C).

Critical Corona VoltagesA Disruptive Critical VoltageA. Disruptive Critical Voltage

It is the minimum phase voltage at which corona occurs:

)r

D.r.ln(.mV equ

oC r

B. Visual Critical Voltage

l3.01**103 4 deq

gThe visual critical voltage Vv for single &three phase lines be obtained:

ln*3.01**

2103VV rr

mr eqv

Where r is the conductor radius in meter mv is the (irregularity factor).d Th l t di t b t d tdequ: The lowest distance between conductors.

MechanicalParameters

TOWERS HEIGHTLINE

SPAN

CONDUCTOR CLEARANCE SAG AND CLEARANCE

AND SPACING

CONDUCTOR

SAG AND TENSION

VIBRATION

Span definitions Basic or normal span : The normal span is the most economicalpspan for which the line is designed over level ground.

Average span : Average span :• The average span is the mean span length between dead ends.

Dead End Span :• A dead end span is the one in which the conductor is dead‐endedat both ends.at both ends.

Wind Span : Th i d i th t hi h th i d i d t t•The wind span is that on which the wind is assumed to acttransversely on the conductors and is taken as half the sum of twospans.

Weight span

•The weight span is the horizontaldistance between the lowest points ofthe conductorsthe conductors.

Ruling or equivalent span• It is the weighted average of the varying span lengths.

...... 334

33

32

31 nlllllL

....4321 n

r lllllL

Sag calculation

) S i l i l l

Sag is defined as: the increment in length of overhead lines that suspended between two points, and there are two cases.

1) Symmetrical suspension level:when the two supports are at the same level.

TlwS

*8* 2

T*8

WhWhere:S: sag at the middle of span (m)w: conductor’s weight (N/m)l: horizontal distance of span (m)T: conductor tension (N)( )

2) Unsymmetrical suspension level2) Unsymmetrical suspension levelWhen the two supports are at different level

Conductor VibrationConductor Vibration

Aeolian Vibration:It is a high‐frequency (5-100 Hz) low amplitude (2.5-5 cm)

ill i d b l l i ( / )oscillation generated by low velocity (0.5-10 m/sec).

Galloping Vibration:It is a low frequency (0.1-1Hz) high amplitude (several

) lf i d ib i hi h ff i l d meters) self excited vibration which can affect single and bundle conductors.

Conductor spacing and clearancesConductor spacing and clearances

Conductor spacing and clearances must be maintained Conductor spacing and clearances must be maintainedaccording to standards.

An empirical formula commonly used for determining the spacingof aluminum conductor lines is :

150

=Spacing metersVd Where:d: is sag in metersV: is line voltage in kV150

And here some typical values of spacing are:

V: is line voltage in kV

yp p g

TOWERS HEIGHT The overall height of the tower is:

H = C + So + 3*SA + SB + SC+ SE

Where :C l d•C = statutory clearance to ground

•SA = length of suspension insulator set•SB, SC and SE = vertical distances between cross-arms and conductor above or to earth-wire•So = sag of conductor (proportional to the g (p psquare of the span).

kV SAMRAkV SAMRA AMMAN NORTH CALCULATIONSAMMAN NORTH CALCULATIONS400 400 kV SAMRAkV SAMRA‐‐AMMAN NORTH CALCULATIONSAMMAN NORTH CALCULATIONS

LINE CALCULATIONS

LINE LINE CALCULATIONS

ELECTRICAL MECHANICAL LINE’S

PARAMETERSLINE’S

PARAMETERSPARAMETERS PARAMETERS

ELCTRICAL PARAMETERS

LINE LINE

CAPACITANCE CORONA LINE LINE RESISTANCE

CAPACITANCE AND

INDUCTANCE

CORONA VOLTAGE

LINE EFFICIENCY

Choice of voltage level &CircuitsChoice of voltage level &Circuits configuration

Voltage level selection depends on the equation below theVoltage level selection depends on the equation below thevalue of power taken from NEPCO 600 MW so the suitablevalue:

Selecting the number of circuits depends on the SIL(surge impedance loading)p g)

The characteristic impedance = 320

R i t l l tiResistance calculation

ACSR 560/50 conductor is used in the line with a RDC =0.0514 ohm at 20 °C

The resistance of ACSR at a temperature rise 65oC is :p

line inductance and capacitance Line inductance and capacitance are measured by using the GMD method for the bundled conductor

Tower spacing (in mm) GMD method calculation

The GMD and GMR values can be found to calculate the line inductance and capacitancethe line inductance and capacitance

Short transmission line equivalent circuitShort transmission line equivalent circuit

ΩZline 3069.728042.5The impedance of line per‐phase is:

The Receiving end voltage line to line is: kV Vr 094.230

A.II sr 842506.1345e peda ce o e pe p ase s:

The receiving ‐end and sending end current:

The sending end voltage line to line is: kVVs 3718139236 e se d g e d vo tage e to e s: kVVs 3718.139.236

The sending end active power is: MWPs 2934.848

Voltage regulation and line efficiency

Voltage regulation :

g g y

Line effLine eff.

Double circuits eff.

Corona effect calculation Corona starting voltage : according to the equation shown

previously the corona starting voltage equal g g

Visual critical voltage :for polished conductor will equal

Total corona losses :found by using an empirical formula

MECHANICAL CALCULATIONS

SPAN CALCULATION

SAG CALCULATION

TOWER HEIGHT CALCULATION CALCULATION HEIGHT

Span calculationConductor used in the line (SAMRA-AMMAN NORTH) is ACSR 560/50 mm,

Span calculation

with cross section diameter = 26.7 mm.

As the spans between the line towers not equal the ruling(equivalent) span is found p q g( q ) p

Sag CalculationsSag Calculations By taking an example of two towers sag at symmetrical spacing the value

of sag equalof sag equal

The maximum sag of conductor at bad weather (15m/s wind velocity and ice thickness about 10mm) :

Tower height

H = C + So + 3*SA + SB + SC + SE I l i l h 6515Insulator string length = 6515 mm

Sag = 3380 mm

Insulator-arm distance =2470,2635,1985mm from upper to lower

Maximum clearance= 15000mm

H= 15+3*(6 515)+3 38+2 470+2 635+1 985H= 15+3*(6.515)+3.38+2.470+2.635+1.985=45.015 m

l t th t h i ht f NEPCO (48 )close to the tower height from NEPCO (48m)

CHAPTER FIVECHAPTER FIVE

MATLAB M‐FILEBy using MATLAB all values calculated in the project were found in a program that Designed for any line –not only this line‐.

1) At first step the line power, voltage and power factor at the receiving side will: g

2) The outputs of the program will shown like below

3)Ci i fi i ill b l d fi d h li i d d i3)Circuit configuration will be selected to find the line inductance and capacitance

4) The tower spacing in meter and the conductor radius in millimeter will input4) The tower spacing in meter and the conductor radius in millimeter will input

5) Then Matlab calculate the value of GMD and GMR

6) The output of the program at the final step is

By comparing the results that we calculated and that ones from MATLAB, the error in results is too smallerror in results is too small..

182kV182kV

230.5 kV

2.13kW/phase/kmkW/phase/km