Static Electrification in large core Mark III transformers

[Indiecuts]

Is there anyone that has experience with Static Electrification in large transformers? I am Looking for proceedures in oil replacement to minimize the risks.

 

[electricpete]

I'll tell you what I know. Sorry if you already know it or it misses the mark.

Large W Shell form transformers are most susceptible since they have high flow velocities. The charge builds up when high velocity cold oil is flowing. Procedure is to run pumps for 24 hours to warm oil before energizing the transformer. Perhaps more if extremely cold weather.

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[Indiecuts]

Thanks, that's exactly the type of information I'm looking for. The transformer has been down for about a month and we are reusing the old oil. The company hired to swap out the oil put the transformer under a vacuum during refill despite written instructions not to because of the Type U bushings. Can you give any further advice??