Overhead Conductors

DayCor® Technology 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

-V e Corona Effect E field 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. UV Ph E field e + -V e UV Photon UV Ph Corona Source Free Electron, coming out from the source Natural Air molecule UV Ph

Bi-Spectral Imaging Combined Mode Visible only display UV only mode Pinpointing the exact corona’s location UV only mode

UV-IR complimentary technologies Live End Corona Dead End Corona No corona on IR picture Corona spots using UV technology

Voltage Stress Related Failures Overloads Design Manufacturing results Mutual Influence

Environment Related Failures Contamination Birds damages Water Tree Conversion

Water 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 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 HMWPE Insulation XLPE Insulation Electrical Treeing

Water 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 Failures Broken Strand

IEEE Standard 400-2001 Notes “Partial discharge measurement is an important method of assessing the quality of the insulation of power cable systems…”

The Corona Process

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.

Schedule repair or replacement Decision Chart Corona- where? Critical component? Yes No Critical location? Material type No Yes Can it be damaged by corona? No Photons per Minute Yes AN, RI, TVI concern? No Low<1000 Corona intensity? 1000<Medium<5000 Yes High> 5000 Schedule repair or replacement Monitor for additional signs Repair or replace ASAP Repair or replace ASAP

4 conductor (“Rail”) bundle Power Line losses New York State Public Service Commission AEP – American Electric Power Line’s type 1000MV Load Corona Losses [MW/100 miles] Miles 765 KV 6.4 4 conductor (“Rail”) bundle 2,116 500 KV 1.6 113 345KV 0.6 5,910 * Yearly average corona loss at sea level based on 20% rain / 2% snow/ 78% fair weather conditions

Don’t Stop The Line…