1. Overhead Conductors

2. 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

3. -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

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

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

6. Voltage Stress Related Failures
Overloads
Design
Manufacturing results
Mutual Influence

7. Environment Related Failures
Contamination
Birds damages
Water Tree Conversion

8. 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.

9. 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

10. 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

11. Hardware Related Failures
Broken Strand

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

13. The Corona Process

14. 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.

15. 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

16. 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

17. Don’t Stop The Line…