The Benefits of On-line DGA Tap Changer Monitoring

Kelman, North America Randy Cox

1. Tools on hand:

A. Oil QualityB. InfraredC. Smoke from ventD. Flickering lightsE. That doesnt sound right

The Past

The Recent Past

1. Tools on hand:

A. Oil QualityB. InfraredC. Smoke from ventD. Flickering lightsE. That doesnt sound rightF. Manual DGA sampling

LTC DGA Challenges

Sealed (previous history hidden in oil) Free breathing (constant loss of information) Manual sampling (just a snapshot, possibly missing

an incipient fault) Introduction of the human factor in the sampling

process Interpretation of results

Interpretation Of Results

Various laboratories offer this service. Training classes are available. On line LTC DGA alarms available with an 8

gas system to alert the user to a rising problem.

Why Perform Dissolved Gas Analysis on Load Tap Changers?

1. It can be done.2. Problems that once had to either be stumbled

upon during routine internal inspections, or discovered during the event of a transformer relay operation, can now be better managed and more readily identified.

3. With the right tools and training it is simple to perform.

4. Why work on something that doesnt have a problem???

Why Do It On Line? Real time information. Contacts move, so problems can develop and then a

tap change occurs and the information moves out of the oil until the unit returns to that tap position.

Contact replacement is expen$ive, and contact overheating tends to spread once it starts.

It can prevent a load tap changer failure, and potential transformer failure.

The technology is now available in an 8 gas system, with the capability of alerting the user to problems in their infant stage for both the main tank and load tap changer simultaneously.

Dont Let This Happen To You

Reversing contact welded closed at Ethylene values less than 400 ppm.

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Acetylene Ethylene Ethane Methane

What are your Questions?