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Re: [TCML] Primary Support Materials - surface tracking

My observations about surface tracking:
Firstly, A spark will travel 3 times as far along a surface than through the air. Clearly shown here with an ignition coil with a 3 inch air gap and 9 inch surface track.
So a piece of insulator placed where the field is greater than 10kV per inch (vs 30kV in air) will cause a short circuit. If that is a plastic then sustained sparking will burn. Secondly, you can prevent the creeping carbon tracking by making sure that there is little e-field at the point of contact with an insulator so that no corona will form there. If there is a conductor (eg a corona ring in air around the point of contact of conductor with insulator) then there is no corona in direct contact with the insulator and no nidus to start the burn. I was getting carbon tracking down a 10 foot fibreglass fishing rod that I used to guide sparks in my Xmas 2007 project. I fixed the problem when I realised this and changed the end conductor to be at right angles rather than parallel with the rod.


From: "Bert Hickman" <bert.hickman@xxxxxxxxxx>
Sent: Wednesday, August 25, 2010 3:48 AM
Hi Gary,
Unfortunately, PVC tends to track more quickly than many other polymers in the presence of a corona discharge. ...


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