Overhead Conductors
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Transcript of Overhead Conductors
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Overhead Conductors
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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
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--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
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Combined Mode
Visible only display
UV only mode
Bi-Spectral ImagingBi-Spectral Imaging
Pinpointing the exact corona’s location
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UV-IR complimentary technologiesUV-IR complimentary technologies
No corona on IR picture Corona spots using UV technology
Live End Corona
Dead End Corona
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Voltage Stress Related FailuresVoltage Stress Related Failures
• Overloads
• Design
• Manufacturing results
• Mutual Influence
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EnvironmentEnvironment Related FailuresRelated Failures
• Contamination• Birds damages • Water Tree Conversion
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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.
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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
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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
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Hardware Related FailuresHardware Related Failures
Broken Strand
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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…”
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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.
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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.
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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
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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
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Don’t Stop The Line…Don’t Stop The Line…