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Fredy Saravia PoicnIng. Electricista, [email protected]

Lima, Setiembre del 2009

Efecto Corona en Lneas deTransmisin

Lneas de Transmisin

Universidad Nacional de IngenieraFacultad de Ingeniera Mecnica

Departamento de Electricidad

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Efecto Corona

Descarga Elctrica autosostenida en lacual la intensidad de campo de ionizacines localizada sobre una parte en elespaciamiento entre conductores.

La descarga puede ser unipolar o bipolar. La corriente de descarga corona se

compone de impulsos de frente de ondamuy cortos (decenas de nanosegundos)con altas frecuencias creando unaradiacin electromgntica intensa.

-

N

++

+

+

+

+

+

+

+

----

--

--

--

--

--

--

----

----

--

--

--

--

+ --

+ --

+ -- --

--

--

-- --

+

++

+ ++

+

+

+

+

+

+

+ +

++

++

+

-- --

----

----

--

--+

+

+

++

+

++

++

+

+

+

++

+

+

++

+

+

+

+

+

--

--

--

--

--

--

--

++

+

+

+

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Fenmeno Corona

Tensin Crtica Disruptiva

Tensin a la cual se produce la perforacin del dielctrico. Corresponde a ungradiente en la superficie igual a la resistencia dielctrica del aire: go= 30 kV/cm bajo25C y 76 mm HG

Tensin Visual Disruptiva

Tensin a la cual el fenmeno

corona es observado

x

d

+q

-q

N

P

c

cdrdlnrmV 1.21

otb27392.3

- Factor densidad aire

b - mm Hg

m - rugosidad (0.87-1)

rC- radio conductor, cm

d - entre fases, cm.

Cc

cVVrr

dlnrmV

3.011.21

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Prdidas por EfectoCorona

Para condiciones de mal tiempo la Vdse afecta por 0.8

Prdidas Corona:Es la potencia que requieren tomar del sistema para que losiones producidos por el campo elctrico (cargas) se muevan alrededor delconductor. Es un fenmeno resistivo.

Las prdidas corona se determinan experimentalemnte mediante balances depotencia y energa. En algunos casos se realizan mediciones especiales.

kV/km/faseVVd

rfP

dOpF

C

C

521025

241

Frmula de Peek

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Factores en Prdidas Corona

Elctricos

Dependen de la frecuencia (CCr => >Pc

Nmero de conductores por faseEstado de la superficie del conductor

Calor del conductor por la Icarga

Mayor E

Menor Ud

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Formas de reducir Corona

Aumentar el dimetro del conductor.

Uso de conductores huecos

Mayor costo

Mayor seccinOtra tecnologa

Lneas de fases mltiples

Unom

kV

Conductor

por fase

Dimetro

del

Conductor

Mm

Seccin

mm2

110 1 11.3 70

220 1 21.6 240330 2 (*) 23.5 300

500 3 25.2 330

750 4 29.0 400

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Diseos Considerando Corona

Es deseable evitar el efecto coronaen condiciones de tiempo normal yreducirla en condiciones de maltiempo.

Se requiere evaluar los costos paraadoptar otros diseo (mayoresdistancias al suelo, mayor seccin,disposicin, etc.).

Se consideran valores aceptables de1 kW/milla en buen tiempo y 3

kW/milla en mal tiempo.

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Ventajas y Desventajas

Ventajas

Reduce la alta tensin de la onda de frente inclinada cuando hay descargasatmsfricas sobre las lneas, disipando la energa como prdida corona.

Desventajas.

Radio interferencias : La descarga corona emite radiaciones que se introducencomo ruidos en lneas de comunicaciones, radio, TV; siendo importanteevaluarlas en V>200 kV

Interferencia inductiva entre las lneas de potencia y de comunicaciones.

Las lneas de transmisin aumentan los campos electromagnticos yelectrostticos en magnitud sufoiciente para inducir corrientes y tensiones enlneas vecinas.

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El efecto corona se presenta cuando elpotencial de un conductor en el aire seeleva hasta valores tales que sobrepasanla rigidez dielctrica del aire que rodea alconductor. El efecto corona se manifiestapor luminiscencias o penachos azuladosque aparecen alrededor del conductor,mas o menos concentrados en lasirregularidades de su superficie.

SISTEMAS DE TRANSMISINDE ALTO VOLTAJE EN CORRIENTE CONTINUA (HVDC)

EL EFECTO CORONA

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La descarga va acompaada de unsonido silbante y de olor de ozono. Si hayhumedad apreciable, se produce cido

nitroso. La corona se debe a la ionizacindel aire. Los iones son repelidos yatrados por el conductor a grandesvelocidades, producindose nuevos ionespor colisin. El aire ionizado resultaconductor (si bien de alta resistencia) yaumenta el dimetro eficaz del conductormetlico.


EL EFECTO CORONA

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En las lneas de transmisin, el efectocorona origina prdidas de energa y, sialcanza cierta importancia, produce

corrosiones en los conductores a causadel cido formado.El efecto corona es funcin de doselementos: el gradiente potencial en lasuperficie del conductor y la rigidezdielctrica del aire en la superficie, valorque a su vez depende de la presinatmosfrica y la temperatura.


EL EFECTO CORONA

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Donde: Vces el valor de tensin crtica disruptiva en kV. es el factor de densidad del aire. res el radio del conductor en centmetros. DMGes la distancia media geomtrica entre fases. RMGes el radio medio geomtrico. nes el nmero de conductores por fase.

kr es el coeficiente de rugosidad del conductor empleado, cuyovalor suele ser: 1 para conductores nuevos. 0,98 - 0,93 para conductores viejos (con

protuberancias). 0,87 - 0,83 para cables formados por hilos.

kmes el coeficiente medioambiental, cuyo valor suele ser: 1 cuando el aire es seco. 0,8 para aire hmedo o contaminado.

kges el factor de cableado.

El efecto corona se producir cuandola tensin de la lnea supere la tensincrtica disruptiva del aire, es decir,aquel nivel de tensin por encima delcual el aire se ioniza. La frmula msutilizada para la determinacin de latensin crtica disruptiva es lapropuesta por el ingeniero americanoF.W. Peek:

CLCULO DE LA TENSIN CRTICA DISRUPTIVA

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El clculo de RMGy DMGdepender encada caso de la geometra de la lneaelctrica.El factor de densidad del aire se calcula

como:

Donde:T es la temperatura del aire en gradoscelsius

Pes la presin del aire en milmetros demercurio.


CLCULO DE LA TENSIN CRTICA DISRUPTIVA

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Para aquellos casos en los que se produce el efecto corona, laprdida de potencia se calcula segn la frmula:

Donde:Pces la prdida de potencia en kW/km.es el factor de densidad del aire.fes la frecuencia de la lnea en HzDMGes la distancia media geomtrica entre fases.RMGes el radio medio geomtrico.Vses el valor de la tensin fase-neutro (o tensin simple) en kV.Vces el valor de tensin crtica disruptiva en kV.


CLCULO DE LAS PRDIDAS DE POTENCIA

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Physics of Corona and Gap

DischargesAC and DC Transmission Line

Corona EffectsUV Inspection Users Group MeetingFebruary 11-13, 2004

ORLANDO, Florida, USABy

Dr. P. Sarma Maruvada

Notas en espaol agregadas por Ing. Ariel Lichtigexclusivamente para curso teora de Campos-FIUBA

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Introduction

Electrical Design, Operation & Maintenance of HVTransmission Lines Requires Consideration of:

-Air Insulation

- Corona

- Insulators

All Three Aspects Require Knowledge of Electrical

Discharges in Air, Which May Comprise:- Partial Breakdown (Corona)

- Complete Breakdown (Gap Discharges)

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Corona & Gap Discharges

Coronais an electrical discharge (i.e. partialbreakdown of air insulation) occurring in the highelectric field region, generally in the vicinity ofconducting surfaces, but sometimes also nearinsulating surfaces, due to ionization processes in air.

Resulta de procesos de avalanchas de electrones bajocondiciones de campo no uniforme que produce quela avalancha cese antes de llegar a tierra.

Complete electrical breakdown of air insulationbetween two electrodes separated by a very small gapis known as a micro-gap discharge or simply as Gap

Discharge.

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Basic Ionization Processes

Ionization and excitation by electron impactA: molcula neutra A*: excitada e inestable

A + e A*+ e (excitation)

A* A + hfp (photo-emission)A + e A++ e + e (ionization, si E es >, e no slosube de rbita sino que se separa)

Photo excitation & ionization

A + hfpA* (photo-excitation)

A + hfpA++ e (photo-ionization,con ms energa)

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Basic Ionization Processes

Electron attachment

A + e A-

RecombinationA++ B-A + B + hfp(radiative recombination, only with electrons)

The energy of photons, or the frequency of light, depends on thedifference in the orbital energies of the electron

El nitrgeno no tiene afinidad con electrones

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Discharge in Uniform Fields

Field intensified ionization & electron avalanche+ : iones, ms lentos - : electrones libres

electric field

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Discharge in Uniform Fields

Discharge development & breakdownLos iones positivos golpean el ctodo y liberan ms electrones. Si hay suficiente

campo, el proceso se autosostiene

H V

iA

Cathode

Anode

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Breakdown and Corona

Excitation of molecules and photon emission occursimultaneously with ionization.

Secondary ionization processes, due to impact of ions or

photons, play a crucial role in breakdown. In non-uniform fields, such as in a conductor-plane gap, only

partial breakdown or coronaoccurs (al disminuir el campo).

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Modes of Corona in Air

Negative DC CoronaModes:Se crea una carga espacialque cambia la distribucinde campo.

- Trichel Pulse- Negative Glow

- Negative streamerDepende se losconstituyentes (N2, O2),generacin de fotones,carga espacial.

Modes of Corona in Air: Visual

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Modes of Corona in Air: VisualAppearance of Negative DC Modes

Para punta de d=0,8 cm sobre esfera deD=7cm, gap=19 cm, exposicin

segundoTrichel

pulse

Glow

Streamer

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Modes of Corona in Air

Positive DC Corona Modes:

- Onset Streamer (el ms

importante)- Positive Glow

- Breakdown Streamer

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Appearance of Positive DC Modes

Para punta de d=0,8 cm sobreesfera de D=7cm, gap=19 cm,

exposicin segundo

Onset streamerGlow

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Gap Discharges in Air

Gap Discharges may Occur:

Between metallic hardware parts of transmission and distribution

lines; Between metallic and insulating surfaces;

On the surface of polluted insulators

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General Mechanism

g

1

U

Gap

Z

Z U2

Divisor

capacitivo

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Typical Current Pulse Produced

rT

T

d

Current

I cr

Time

ns s

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Light Emission from Discharges

Excitation: A + e A*+ e

Photo-emission: A*A + hfp

with hfp= (E2E1)

where E2is the energy of the excited state and E1is the

energy of the ground state to which the moleculereturns.

Light spectrum emitted in air is mainly that of

molecular nitrogen. Excitation potentials of N2= 6.3 eV and of

O2= 7.9 eV

La mayora de los fotones est producida por N2

Di f th El t i d Vib ti l

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Diagram of the Electronic and Vibrational

Energy Levels of the Nitrogen Molecule

Distintos tipos de fotnsegn el salto de energa

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The frequency band of light emitted is in the UV range, with the

stronger emissions having wavelengths in the range of 300 nm to500 nm and the weaker emissions in the range of 80 nm to 200 nm.

The excitation coefficient (i.e. number of molecules excited by anelectron drifting 1 cm in the field direction) depends on the

composition of air and is a function of E/p (cociente campoelctrico/presin)

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Presence of any trace gases such as argon, carbon dioxide etc.,can change the light spectrum emitted by discharges in air.

Spectroscopic data in air suggest that sparks (breakdown)produce more intense light than streamers (corona).

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Photoabsorption

Photons emitted during the avalanche development in air areabsorbed:

a) partly by other gas molecules;b) partly by the negative oxygen molecules in the gas,

leading to photo-detachment;O2

- + hfp O2 + e

Other mechanisms leading to the loss of photons are:photoionization, step ionization, dissociation and dissociativeionization

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Photoabsorption

Overall photoabsorption may be characterized by I (intensidad de

fotones):where is the absorption coefficient.

Typical values of at atmospheric pressure are:

For N2, = 0.3 cm-1,

O2, = 30 cm-1,Air, = 5 cm-1

A menor , se propaga mayor distancia

The presence of moisture in air reduces by about 25%.

xe0II

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Radiation from a Corona Discharge

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Radiation from Sun

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Corona Onset Gradient (en kV pico/cm)

c0c r

K1EmE

E0and K are empirical constants (for positive dc,E0=33.7 & K=0.24, for negative dc & ac, E0=30.0

kV/cm & K = 0.30) = (273+t0).p/(273+t)p0 is the relative air density; t is

the temperature and p the pressure of ambient air andt0and p0are reference values; (t0= 25C and p0= 760

mm) rcis the conductor radius in cmm conductor surface irregularity factor, depende de la

rugosidad superficial del conductor

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Corona Effects on AC and DC

Transmission Lines

For both ac and dc lines: Corona (power) Loss (CL)

Electromagnetic Interference (EMI) (Includes RI, TVI, etc.,)

Audible Noise (AN)

Ozone, NOxetc.For dc lines:

Space Charge Effects

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AC Space Charges and Corona Loss

+++

+++ +

++++

+++

+ + ++

--

------- - -

-+

++++

+

+

++ + +

+

- ---

------ - - -

-

-----

---- - - -

--

--

-------

-----

- - - - --

-----

--- +

+

++

+

+

+

+

++

+

+

+++

+++++

+ ++

--

-----

------

- - - --

--

---

----

-

--

--

--

- - --

--

--

-- -

++ +

++

+++

+

+++

++

+

++

( a )( b )

( c ) ( d )

( e ) ( f ) I dba c tc e gfUIcorIcorona es capacitiva, pordesplazamiento de la carga espacial.

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Main Types of DC Transmission Lines

Unipolar Lines

Bipolar Lines

Metallic return

( Optional)

AC System AC SystemAC SystemAC System

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Physical Description of Unipolar Corona

Unipolar ions created near the conductor drift towards the ground, fillingthe entire space

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Physical Description of Bipolar Corona

Ions of both polarities fill the space, creating two unipolar regionsand a bipolar region

PositiveNegative RegionRegion

BipolarRegion

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Generation of RI

Corona current pulse

trains are injected intoconductors

The high-frequency

current components

propagate along the

conductors andproduce RI near the

transmission line.

time

T

T

c+

DC Positive

DC Negative

AC

time

time

c-

c+TPulsos aleatoriamentePulsos menores

Ambos tipos

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Corona & Gap Discharge Current Pulse

Characteristics

Both positive andnegative corona, aswell as gap

discharge, currentpulses have a fast-rising front (1 a 50ns) and a slowly

decaying tail (50 a200 ns) as shown

cr

cr0.1 I

0.9 I

crI

Tr Time

Current

dT

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Corona Current Pulse Characteristics

Type of Pulse Amplitude

(mA)

Rise-time

(ns)

Duration

(ns)

Repetition

Rate

(pulses/s)

Positive Corona

Negative Corona

Gap Discharge

10 50

1 10

500 - 2000

50

10

1

250

100

5

103 5.10

3

104- 10

5

102 5.10

3

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Corona Current Pulse Characteristics

Frequency Spectra of

Corona and Gap DischargePulses

0.01 0.1 1.0 10.0 100.0 1000.050

110

100

90

80

70

60

Frequency, MHz.

F(

)

,dB

PositiveGap

Negative

RI Characteristics of AC Lines

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RI from transmission lines is generally defined in terms of threecharacteristics:

1. Frequency Spectrum

0

10

20

30

40

50

60

70

0.2 0.3 0.5 1 2 3 5 10 20 300.1

Frequency, MHz

RI,

dB(V/m)

QP

RI Ch t i ti f AC Li

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2. Lateral Profile (proporcional a 1/D)

0

10

20

30

40

50

60

70

075 50 25 25 50 75 100100- - - -

RI,dB(V/m

)QP

Distance, m


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3. Statistical Distribution

40 6020 25 30 35 45 50 55 65

0.51.0

2.0

5.0

10.0

20.0

30.040.0

50.0

60.0

70.0

80.0

90.0

95.0

98.0

99.0

99.8

99.9

Perce

ntageTimeAboveA

bscissa

RI, dB ( V /m ) QP

RI Characteristics of DC Lines

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Lateral Profile

0

10

20

30

40

50

60

70

075 50 25 25 50 75 100100- - - -

RI,dB(V/m

)QP

Distance, mEl positivo contribuyemucho ms a laradiointerferencia.Producida por lasdescargas tipo streamer.

RI Ch t i ti f DC Li

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Statistical Distribution

40 6020 25 30 35 45 50 55 65

0.5

1.0

2.0

5.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

95.0

98.0

99.0

99.8

99.9

Percenta

geTimeAbove

Abscissa

RI, dB ( V /m ) QP

Audible Noise Generation and

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Audible Noise Generation andPropagation

Generated Corona AcousticPulse

AN Propagation

- 2

- 1

0

1

2

400 10 20 30 50 60 70 80

Time, s.

Pressure,

Pa.

r

P

O

2

xx

R

1-

AN Characteristics of AC Lines

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AN Characteristics of AC Lines

Audible noise from AC lines is described, similar to RI, in terms offrequency spectrum (figure below), lateral profile and statistical

distribution

6331 125 250 500 1000 2000 8000 160004000

30

40

50

60

SoundPressureL

evel,dBabove20

PA

Frequency, Hz

Corona-generated Hum Noise

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Corona-generated Hum Noise

Oscillatory movement of the ionic space charge creates hum noise attwice power frequency; Figure shows lateral profile of hum noise

70

60

50

40

0 10 20 30 40 50

Lateral Distance From Center Phase, m.

SoundPressure

Level,dBabove

20PA

AN Ch t i ti f DC Li

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AN Characteristics of DC Lines

Lateral profile & Statistical distribution are similar to those for RI;Frequency spectrum is given below

6331 125 250 500 1000 2000 8000 160004000

30

40

50

60

SoundPressureL

evel,dBabove20

PA

Frequency, Hz

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DC Electric Field & Space Charge

Profiles

E

(kV/m)

20

30

10

40

60

70

80

90

100

-10 0 10 20 30 40 500

5

10

15

20

25

Computed Electric Field

j(nA/m

)

- +

Distance from Centre of Line, m

NegativePole

Positive P ole

Measured Electric

Field

ComputedCurrent Density

Measured

Current Density

g

50

g

2

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DC Fields & Ions Design Criteria

Design criteria for electric fields and ion currents under DC linesare established on the basis of human perception studies

Based on such studies, the following design limits have been

proposed:E = 25 kV/m (en ca 10 kV/m)

j = 100 nA/m2 (corriente inica)

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Corona Tutorial

Dave PhillipsSubmarine Operating Authority Engineering

Space and Naval Warfare Systems Center

IEEE Joint Technical Committee Meeting 200

Orlando, Florida7 January10 January

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What Is Corona?

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What Is Corona?

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What Is Corona?

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What Is Corona?

Corona is a luminous

discharge due to ionization ofthe air surrounding anelectrode, caused by a

voltage gradient exceeding acertain critical value.

E l f C d C

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Example of Conductor Corona

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Whats The Fuss?

Corona from conductors andhardware may cause audible noise

and radio noise

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Whats The Fuss?


and radio noiseAudible noise from conductors may

violate noise standards

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Que es este alboroto?


and radio noiseAudible noise from conductors may

violate noise standards

Radio noise from conductors mayinterfere with communications ornavigation

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Whats The Fuss?

Corona from conductors and hardwaremay cause audible noise and radio noise

Audible noise from conductors mayviolate noise standards

Radio noise from conductors may

interfere with communications ornavigation

Corona loss may be significant whencompared with resistive loss of

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Whats The Fuss?

Corona from conductors and hardware maycause audible noise and radio noise

Audible noise from conductors may violate noisestandards

Radio noise from conductors may interfere withcommunications or navigation

Corona loss may be significant when comparedwith resistive loss of conductors

Corona can cause possible damage to polymericinsulators

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Corona Discharge Currents are Impulsive

Ic(t)

t

0.010.1 sec

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Physical Parameters of Corona

Corona is caused by the ionization of the media (air)surrounding the electrode (conductor)

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Corona onset is a function of voltage

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Corona onset is a function of voltage

Corona onset is a function of relative air density Corona onset is a function of relative humidity

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Corona and the Electric Field

Corona is NOT solely a function of the Electric Field

Corona is a function of the electric field on the surface of theelectrode (conductor)

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Corona is NOT solely a function of the Electric Field

Corona is a function of the electric field on the surface of theelectrode (conductor)

Corona is also a function of the radius of curvature of theelectrode (conductor)

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Corona is NOT solely a function of the Electric FieldCorona is a function of the electric field on the surface of the

electrode (conductor)Corona is also a function of the radius of curvature of the

electrode (conductor)Corona is also a function of the rate of decay of the electric

field away from the electrode (conductor)

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Corona and the Relative Air

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Corona and the Relative AirDensity


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Corona has an inverse relationship with air density


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Corona has an inverse relationship with air density

Standard line designs that perform well at sea level, mayhave significant corona issues if used on lines that are

installed over mountainous areas

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Corona and the Humidity

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Corona has an inverse relationship with humidity at powerfrequencies

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Corona has an inverse relationship with humidity at powerfrequencies

Fair weather corona is more prevalent in low humidity

environments

Corona Is Dependent

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Surface Condition Of The

Conductors

Corona Is DependentS f C di i Of Th

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Conductors Corona is enhanced by irregularities on the conductor

surface

Corona Is DependentS f C diti Of Th

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surface

Irregularities include: dust, insects, burrs and scratches

and water drops present on new conductors


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surface Irregularities include: dust, insects, burrs and scratches

and water drops present on new conductors Corona will generally be greater on new conductors and

will decrease to a steady-state value over a period ofapproximately one year in-service


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ConductorsCorona is enhanced by irregularities on the

conductor surface Irregularities include: dust, insects, burrs and

scratches and water drops present on newconductors

Corona will generally be greater on newconductors and will decrease to a steady-

state value over a period of approximatelyone year in-service

Corona is significantly increased in foulweather.

Corona Is Dependent On

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Corona Is Dependent OnLocal Electrode Geometry


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Non-Critical Surfaces

Non-Critical Surface

Critical SurfacesNumber of Elements =210

Critical Section


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r

S

Ground Plane V = 0

Sphere V = V0


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0 0.5 1 1.5 2 2.5 3 3.5 4 4.50

500

1000

1500

2000

2500

3000Actual Electric Field vs. Distance

Distance (cm)

ElectricField(V/cm

)

1 cm

2 cm

3 cm

4 cm

5 cm

6 cm

7 cm8 cm

9 cm

Why is it a special problem for

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Why is it a special problem for

voltage upgrades?If the voltage of a transmission line is increased

without changing the line design, the electric field

at the surface of the line conductors (and hardware)

will increase. This increase will cause additional

corona

The same can be said for compact transmission

lines

Practical Consequences

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1. Larger conductors betterto a point

2. Use conductor bundles to reduce corona

3. Corona phenomena much worse in foul we

4. Compact lines more susceptible5. New conductors can lead to poor corona p

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Ca tions Regarding Radio Noise

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Cautions Regarding Radio Noise

Radio noise from corona should not be confused with radionoise generated by spark discharge

High frequency complaints are almost always due to

sparks


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sparks Causes of spark discharges can be located and repaired


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sparks Causes of spark discharges can be located and repaired

Corona is a DESIGN ISSUE


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Radio noise caused by corona cannot be reduced bychanging the line configuration near where the noiseproblem is occuring. The source of the problem can beseveral miles away

A dibl N i

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Audible Noise

Can get broadband noise and hum

Load can affect audible noise

For measurement see:

ANSI/IEEE Standard 656-1992IEEE Standard

For Measurement of Audible Noise from Overhead

Transmission Lines

Audible Noise

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Audible Noise

May be present as 120 Hz Hum or broadband noise

Can be affected by load

Audible Noise

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Audible Noise

Audible Noise

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Audible Noise


Audible Noise

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Audible Noise


Can be affected by load

Audible Noise in Context

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50

55

60

65

Audible

Noise dBA

30 meters

from

centerline

NumerouscomplaintsModerate

complaintsNo

complaints

Source: BPA study

Common design limit53 dBA

EPA RegulationsEffect Level Area

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Effect Level Area

Outdoor

activity

Indoor

activity

Ldn< 55 dBA

Residential areas

and farms where.. quiet is a basis

for use

Leq(24)< 55 dBA

Areas where

people spend

limited time

Ldn< 45 dBA

Leq(24)< 45 dBA

Residential

Other

Ldn(has a -10 dB adder nightime) Leq(24)(24 hour average)

Tradeoff: Magnetic Field vs. Audible Noise

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x

y

Effect of Changing Conductor Phasing

A

B

C

A or C

B

C orA

WhiteABCABC Super Bundle

RedABCCBA Low Reactance

500 kV Double Circuit Line

Magnetic Field is Reduced

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0

5

10

15

20

25

0 20 40 60 80 100 120

Distance from Center Line

MagneticF

ield(mG

ABCABC Super Bundle

ABCCBA Low Reactance

Audible Noise is Increased

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52

54

56

58

60

62

64

0 20 40 60 80 100 120

Distance from Center Line (m)

AudibleNoise(dBA

ABCCBA (Low Reactance)

ABCABC (Super Bundle)

Audible Noise is Increased

Corona Loss

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What is it?

Whenever corona occurs on a transmission line, there is a corresponding loss ofenergy called corona loss. This loss is one of the reasons why the transmission of

electric energy between two points is not perfect.

When can it be a problem?

Generally, corona loss is significantly less than resistive loss. However, at highervoltages, high altitudes and during foul weather, corona loss can actually exceedresistive loss.

A Word On Corona Losses

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Whenever corona occurs on a transmission line, there is acorresponding loss of energy called corona loss. This

loss is one of the reasons why the transmission of electricenergy between two points is not perfect


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Whenever corona occurs on a transmissionline, there is a corresponding loss of energycalled corona loss. This loss is one of the

reasons why the transmission of electricenergy between two points is not perfect

Generally, corona loss is significantly less

than resistive loss. However, at highervoltages, high altitudes and during foulweather, corona loss can actually exceedresistive loss

Example Losses (sea level)

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Example Losses (sea level)

Line

Voltage (kV)

Bundle

n x 2a

Load

MVA

I2R Loss

kW/km

Corona Loss (kW/km)

Average Maximum

362

550

800

2 x 3.16

3 x 3.3

4 x 3.3

400

900

2000

41

52

93

2

4

8

26

78

208

Corona On Hardware

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Transmission line hardware is usually tested in thelaboratory prior to being selected to determinewhether is corona free. This test is often done on asingle phase system in order to conserve laboratory

space.

It has been found that the traditional method of

energizing the system to 110% of the rated line toground voltage is not sufficient, especially for lines

of more compact design. Apparently, the hardware

is exposed to higher gradients in the field than those

Corona On Hardware

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Corona On Hardware

Corona On Hardware

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Corona On Hardware

Transmission line hardware is usually tested in thelaboratory prior to being selected to determine whether iscorona free. This test is often done on a single phasesystem in order to conserve laboratory space

Corona On Hardware

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Corona On Hardware

Transmission line hardware is usually testedin the laboratory prior to being selected todetermine whether is corona free. This test is

often done on a single phase system in orderto conserve laboratory space It has been found that the traditional method

of energizing the system to 110% of the rated

line to ground voltage is not sufficient,especially for lines of more compact design.Apparently, the hardware is exposed to highergradients in the field than those to which the

hardware was tested

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DAOS EN LINEAS DE SUB

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TRANSMISION

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DAOS EN SUBESTACIONES

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DAOS EN LINEAS DE TRANSMISION

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DEFECTOS TIPICOS

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DEFECTOS CAUSADOS POR ELEFECTO CORONA

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EFECTO CORONA

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FIN DE LA EXPOSICION

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LT-2.3 Corona Set09