Study during Arcs upgrade results in major cost avoidance for AEDC

  • Published
  • By Deidre Ortiz
  • AEDC/PA
AEDC engineers performed a study during the Mid-Pressure Arc Heater (MPAH) upgrade project that led to a cost savings of approximately $3 million for AEDC.

The MPAH project is a Central Test and Evaluation Investment effort to upgrade the materials test capability of the H2 Arc Heater Altitude Test Cell at the Complex. Though initial calculations showed the MPAH upgrades would exceed the existing transformer’s maximum load, a study performed by electrical engineers Howard Frederick and Tony Acklen determined it would support the load and not need to be replaced.

Frederick explained the 161-kV transformer refurbishment, which began in 2009, served as a catalyst for the review of the transformer and credits it for leading to this savings.

“In that project, the transformer’s cooling system was restored to original condition,” he said.

Martin Johnson, Air Force electrical asset manager who launched the 161-kV transformer refurbishment project, mentioned it was much needed.

“There are ten 161-kV transformers at AEDC that are over 60 years old,” he said.

A transformer for the Engine Test Facility was refurbished first, then when one of the transformers for the Propulsion Wind Tunnel facility experienced an operational failure, then the remaining nine were refurbished.

“The transformers now have solid state controls and are connected to a new Supervisory Control and Data Acquisition system with fiber optic,” Johnson said. “The old SCADA was a computer that was a 1986 version.”

According to Acklen, these 10 older transformers are only a portion of the thirty 161-kV transformers on base, and when upgrades occur at the test facilities, it takes some research to decide on how to best meet any changes regarding power.

“The age old question at AEDC seems to be where to get power for large new equipment,” he said. “Determining the size of the transformer actually needed is something that’s a little tricky too.”

Acklen also mentioned that AEDC Power Control has been documenting the connected loads of electrical equipment.

“During the course of this documentation it became apparent that all of the equipment rarely runs at the same time, and it just made sense to explore the possibility of feeding the new load from an existing transformer in the Propulsion Wind Tunnel Plenum Evacuation System (PES) substation,” he said. “Especially since four were recently
refurbished under the Air Force contract with the manufacturer. The coolers that were installed are very good at keeping the temperature under control.

“Howard studied PES-2 because the secondary substation had the desired 6,900 volts. It had less existing load than the others, and most evident was the fact that the temperature had not exceeded 45 degrees Celsius which was way below its rated limit. Also key was complications, that I knew from experience, can arise from making a new transformer fit into the same space as an old one.”

Therefore, Acklen and Frederick calculated the new load and added it to that of the current load of the transformer.

“While the total of the two lists exceeded the rating of the transformer, we knew that electric utilities see similar ‘overload’ conditions at peak power conditions,” Frederick said. “We also knew that the IEEE (Institute of Electrical and Electronic Engineers) had a standard method for calculating effects of short-term loading of oil-filled transformers beyond that of the nameplate rating.”

After preliminary calculations, it appeared that the transformer would be able to handle the load profile required. The results were shared with Harry Clark, Air Force project manager for the MPAH project, who requested a finalized analysis. After further review, Acklen and Frederick’s findings were accepted.

“Their attention to the engineering detail required for an accurate design and their concern that taxpayer dollars be best used to meet the project requirements led to a determination that an upgrade to PES-2 was not required, saving the project an estimated $3 million.”
Johnson commends Acklen, Frederick and all the experienced power personnel at AEDC for their support leading to this success.

“We have had a very good Power System Analysis program, which is headed by Beth Baker,” he said. “This allows us to determine the condition of our electrical equipment and if the equipment can handle any additional loads.

“Howard Fredrick and Tony Acklen have always been very helpful and honest when I ask about electrical issues. I have a very good working relationship with them. There was a Service Life Extension Plan that was developed in 2013 for the electrical equipment and [they] were the main drivers in the plan.”

-AEDC-