ABB Power Services

Our aim is to increase systems reliability and extend the life of their equipment with concomitant gains for our customers’ competitiveness. We support our customers with high-quality services in preventive and corrective maintenance to improve risk mitigation and improved safety. ABB's service portfolio allows utilities and industrials to maximizing the return on all assets by ensuring a high reliability, reducing life cycle costs and ensuring optimized performance while lowering environmental impact.

Wednesday, June 8, 2011

Low Frequency Heating Drying Solutions for Wet Transformers

Summary

Low Frequency Heating (LFH) drying solutions for wet transformers can help extend the life time of transformers.

The status of the oil-cellulose insulation system is one of the key parameters influencing: lifetime expectancy and reliability. The ageing rate of insulating material depends on different parameters such as original insulation material, oil temperature, water content, oxygen content and acids from oil and paper aging.  Efficient LFH drying system delivers substantial benefits including low residual moisture, shorter downtime, reduced costs, on-site process, no transport time and costs.

Drying of Transformers

The origin of water in insulation can vary: quality of original drying, ingress through breathing system or gaskets, aging of cellulose. Reduced moisture allows a longer lifetime, higher reliability and overload capability (no bubbling). Impact of moisture on the lifetime of a transformer includes:
  • Lifetime of a dry transformer is significantly longer
  • Dry transformer can withstand more load without a reduction of it’s lifetime
  • A moisture increase in the paper insulation from 3% to 4% causes ageing comparable to a 6 to 8ºC temperature rise
  • Indicative lifetime of insulation @ 80ºC: 40 years if 1% moisture in paper insulation, 10 years if 3% moisture in paper insulation
Conventional On-site Drying Solutions
  • Hot oil circulation if vacuum can not be applied
  • Hot oil circulation and vacuum cycles (+ cold trap)
  • Hot oil circulation and vacuum cycles with oil spray (plus cold trap) LFH
  • Low Frequency Heating (LFH) under vacuum (plus oil spray)
Advantages of LFH Drying Solution

  • High drying efficiency, remaining moisture down to less than 1%
  • On-site: no transportation risks, time and costs
Drying Process Expertise is a Must

Removing moisture from windings may cause a reduction of the clamping force, therefore any drying process (either online or offline) must be performed following a strict process by experienced transformer maintenance experts.
Short drying time, 30-50% shorter than conventional drying process with hot oil circulation and vacuum

14 comments:

AJ said...

Dear sir,

1)With LFH method upto what range of transformer can be processed like 132kv/220kv/400kv .
2) for Onsite : you mention no transportation how it possible to process on line.( alternative arragement)

3)since this method is applied without any cooling media what will be rated current and what about hotspots , how it is taken care of.

4)Can we compare with Mobile Vapour phase drying .
3)

ABB Power Services said...

AJ, there is really no limit to the voltage class transformer processed with LFH. Many 500kV-class transformers as large as 750MVA have been successfully processed and dried using LFH in combination with conventional processing rigs.

On-line processing is really oil reclamation, not just filtering and drying/degasification. Careful controls must be in place to accomplish this in a personnel-safe way as well as making sure the transformer (and oil) isn't damaged during the process. Temperature (as well as other parameter) controls are essential. You can contact your local ABB transformer service representative to get more information.

If you can share your experience with mobile vapor-phase drying, we can develop some comparisons. We do not have a mobile VP system for large transformers in North America.

Thank you for the thoughts. Feel free to contact me directly if you need more information.

Craig L Stiegemeier
craig.stiegemeier [at] us.abb.com

AJ said...

We have found hardly and user of LF heating plant, why? also many transformer manufacturer uses Hot air circulation under vacuum plant , cant we use LFH unit with these plant as assistance in heating process.

Hunterheatandair said...

Careful controls must be in place to accomplish this in a personnel-safe way as well as making sure the transformer (and oil) isn't damaged during the process. Heating Service Edmond

heatingontario said...

As a leading innovator of home heating, cooling and air-quality systems,we're committed to making people feel comfortable in their home environments,which includes a commitment to protect the global environment.

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AJ said...

WHY LFH HEATING HAS NOT PICK UP , IN FACT INSTEAD OF HEATING BY HOT AIR WE CAN USE LFH WITH HOT AIR WHICH WILL SHORTEN THE TIME REQUIRE FOR DRYING IS THAT CORRECT?
ALSO INSTEAD OF HOT AIR IF HOT OIL IS SPRAYED THROUGH NOZZLE TO HEAT OTHER PASSIVE PART CAN EXPEDITE THE DRYNG PROCESS.
WHAT IS THE REASON FOR NOT IN USE ON LARGE SCALE?

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Trinityserviceshvac said...

great solution, i would really try to this solution.

thanks
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ASHOK J said...
This comment has been removed by a blog administrator.
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MAYUR BUDH said...

Hi
Kindly let me know from where do I get these transformer LFH heating services in India
Pls revert at mmbudh@gmail.com

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