overhead conductors

Overhead Conductors

DayCor® Technology is used to detect Corona Particle Discharge and Arcing

on electric grid components.

It offers you:

• Early warnings of potential future failures.• Pinpointing & Visualizing the corona effect. • Decision ability to determines the health of your critical systems components• Prioritize your particle discharge maintenance challenges • Day time work DayCor® Technology saves you by avoiding costly unscheduled outages and failures

DayCorDayCor®® Technology Technology

E field e

e

+

e

e

+

e

e

e

+

--V V ee

UV Ph

UV Ph

UV Ph

Corona is a luminous partial discharge due air ionization. The DayCor® camera pinpoints the exact source’s location by visualizing the UV photons, coming out of it.

Corona EffectCorona Effect

Corona Source Free Electron, coming out from the source

Natural Air molecule

UV Photon

Combined Mode

Visible only display

UV only mode

Bi-Spectral ImagingBi-Spectral Imaging

Pinpointing the exact corona’s location

UV-IR complimentary technologiesUV-IR complimentary technologies

No corona on IR picture Corona spots using UV technology

Live End Corona

Dead End Corona

Voltage Stress Related FailuresVoltage Stress Related Failures

• Overloads

• Design

• Manufacturing results

• Mutual Influence

EnvironmentEnvironment Related FailuresRelated Failures

• Contamination• Birds damages • Water Tree Conversion

Water TreesWater Trees

• Water migration into the insulation leads to water trees.

• Water Trees lead to decreased insulation resistance and very slight increase in leakage current.

• Water Trees do not directly produce failure.

• Water Trees lead to electrical trees which produce Partial Discharge and ultimate failure.

Water Tree ConversionWater Tree Conversion

• The high electric field caused by voltage surges result in power dissipation in the water channels existing in insulation sufficient to raise the temperature of the water and increase pressure in the water tree channel.

• This phenomena generates cavities sufficient to support partial discharge

Electrical TreeingXLPE InsulationHMWPE Insulation

Water Tree ConversionWater Tree Conversion

• Each occurrence at which PD occurs causes the size and geometry of the insulation void to change. Lowering the PD inception and extinction voltages.

• When PD extinction voltage drops below system nominal voltage, PD’s are continuous leading to electrical tree formation and ultimate insulation failure

Hardware Related FailuresHardware Related Failures

Broken Strand

IEEE Standard 400-2001 NotesIEEE Standard 400-2001 Notes

“Partial discharge measurement is an important method of assessing the quality of the insulation of power cable systems…”

The Corona ProcessThe Corona Process

UV radiation causes erosion of the internal surface of the void.

Continued erosion forms channels that develop into so-called electrical trees in the insulation

Continued corona produces further erosion until the electrical tree bridges the insulation.

Insulation System Failure

Microscopic spaces (“voids”) may be formed in insulation systems due to water tree growth, aging, installation or manufacturing defects. Continued stress over voltages can initiate corona in voids.

Why Test for Partial Discharges?Why Test for Partial Discharges?

• Partial discharge testing can detect: –Insulation defects that may have occurred during cable system installation or at the manufacturing process

–Insulation deterioration due to normal service operating conditions

• Partial discharge testing is a PREDICTIVE qualitative analysis tool that can warn from a potential upcoming system failure.

• Partial discharge testing is Non Destructive Testing method

• Partial discharge test results can be trended over time.

AN, RI, TVI concern?

Decision ChartDecision Chart

Photons per Minute

Can it be damaged by

corona?

Corona- where?

Criticalcomponent?

Material typeCritical location?

Corona intensity?

No

No

No

Yes

Yes

Yes

High> 5000

1000<Medium<5000 Low<1000

Monitor for additional signs

Schedule repair or replacement

Repair or replace ASAP

No

Yes

Repair or replace ASAP

Power Line lossesPower Line losses

AEP – American Electric Power

Line’s type 1000MV Load

Corona Losses [MW/100 miles]

Miles

765 KV6.4 4 conductor (“Rail”) bundle

2,116

500 KV1.6 113

345KV 0.6 5,910

New York State Public Service Commission

* Yearly average corona loss at sea level based on 20% rain / 2% snow/ 78% fair weather conditions

Don’t Stop The Line…Don’t Stop The Line…