Corona, Arcing, Partial Discharge & Predictive Maintenance UV Inspection Magazine

Seeing Corona - The Daytime UV Inspection Magazine

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Editorial

The Corona Inspection Breakthrough

In this issue:

Updated:
Dec 2007

With the advent of Non Ceramic High Voltage Insulators, i.e. Insulators made of Plastic Polymer; a new importance is reached in the detection and eradication of Electric Corona on high-tension equipment as found on overhead power lines and in substations.

Corona damage

Above: Polymer Insulators with Corona Damage

Missing Corona Ring

Above: Missing Corona Ring

Many installed polymer insulators do not have protection for Corona damage. Some insulators are not equipped with grading corona rings and others have damaged or missing rings. Some grading corona rings are not installed correctly or may have the wrong design or size.
The invisible corona on a polymer insulator and its hardware can seriously damage the insulator, resulting in flash-over or flash-under conditions. Electric corona on a polymer insulator can damage the sheds and the membrane that is keeping the fiberglass rod system intact. If this happens pin holes can let moisture inside the protective membrane and the insulator will have an internal short. The corona may also damage the insulator so that it shears off. The corona can corrode the insulator ends and jeopardize the structural integrity of the insulator. Electric Corona together with the Nitrogen and moisture in the air produces Ozone and Nitric Acid! A no-no for Polymers.

Above; Severe loss of material due to Corona.

Above: Faulty 110 kV Insulator Removed & Tested at 50 kV!

In any of these cases, the possibility of a line drop is real and could happen at any time when the corona is existent on the insulator. The early detection of Electrical Corona is extremely important to keep the integrity of the electrical grid.

The Ofil DayCor® Solar Blind UV Corona Detection Camera System makes the detection of Corona easy during daytime conditions even in bright sun light conditions. The DayCor® is the most important tool available to the Electric Utility Industry in its quest to improve the Electrical Grid by finding and correcting Electrical Corona Problems.

Jan K. Eklund,
Ofil's representative in USA

jan@eklundir.com
P: 770-578-4435
F: 770-578-9899
© Copyright 2007 EKLUND INFRARED Inc.

DayCor® Superb - Ofil’s handy inspection tool for daily PdM and PM tasks in substations and distribution lines

"In 2007 Ofil has launched successfully the DayCor® Superb corona camera. The new DayCor® Superb is a held camera dedicated to enable easy and accurate corona and arcing detection for foot patrol.."

Solving Radio Interference complaints at BPA:
"The DayCor camera pinpointed the problem on the the conductors which reduced the amount of outage time needed to fix the problem."

Findnig defects of insulators at Russian railways
"Results of testings confirm the efficiency DayCor at finding insulators defects by railway car motion"

Radio Interference Case Study
A case study about resolving a radio interference problem for the FAA air traffic control tower at the Rochester New York airport.

Reproduction of fault causing flashovers.
Laboratory test with UV camera on insulators removed from power line

Inspection of Polymer Insulators
"...A major research project was conducted by EPRI about predictive maintenance of transmission lines and substations..."

Internal and External Defects in Polymer Insulators
"...A test was designed to check possible degradation of NCIs due to internal defects. Three types of defects..."

Surface Discharge at RWE Eurotest Lab
"...A partial discharge (PD) test, carried out at RWE Eurotest on a silicon cable revealed high partial discharge levels that could not be explained..."

EPRI - EKPC Polymer Failure Investigation
"...Between 1996 and 1998 East Kentucky Power Cooperative experienced six failures of polymer insulators over a range of voltage level..."

Critical Polymer Defects
“...When I detect severe activities on polymer insulators – I know that these are distinct signs of problems..."

Winyah Generating Plant,
Santee Cooper Corona Imaging
"The corona camera has helped in determining which insulators and structures was being contaminated"

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