20190924Avista to Staff CS2 06-25-07.pdf

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120 Prospect Street
Ballston Spa, NY 12020
Phone [phone]
FAX [phone]
E-mail [e-mail]

Charles T. Raymond, P.E.
Transformer Inspection
Areva GSU
213/284/355 MVA
Areva S/N 316322
Inspections performed on-site

Charles T. Raymond, P.E. June 25, 2007

Background
This transformer was manufactured in Gebze, Turkey in 2002 as a spare for a duplicate transformer that failed in service and was scrapped after investigation.
This transformer experienced a failure during factory impulse tests, shipping damage that required factory disassembly and repair at the ESI repair facility in Westminster,
CA, and an insulation failure in service that required return to Gebze, Turkey for
repair.
It subsequently developed evidence of gassing in service as detected by the Severon gas monitor. Of particular concern were the levels of ethylene and acetylene. These gases indicated a high probability of insulation degradation.
On site testing and inspections followed to assess the condition of the transformer.

Site Inspections
Mr. Scott Wilson performed on-site tests and made internal inspections after the oil was removed. I was provided results of the tests and a video of his inspections as well as his descriptions as conveyed through phone conversations.

The following is a summary of my opinions:
1. The makeup of the combustible gases indicates a high probability of insulation failure.
2. Based on the history of this transformer and the prior duplicate, operation
of this transformer with these high gas contents is inadvisable.
3. The on-site electrical tests indicated an elevated power factor between the low voltage windings.
4. The in-tank inspections did not indicate any evidence of a problem that could be identified and corrected without going through extensive
disassembly in a transformer facility.
5. The transformer, if properly constructed, should have been capable of performing in the service conditions encountered including operations in back-feed from the 500kV system. This was investigated in detail previously by Dr. Degeneff both theoretically and in conjunction with
transients as measured by the Areva transient measuring equipment.
Charles T. Raymond, P.E. June 25, 2007

6. The transformer should not be considered operational without a thorough
teardown investigation. This will undoubtedly necessitate a complete rewind to restore serviceability.
7. Because of the cost of a teardown, investigation, and rewind, replacement would be a more economical option and should result in a more reliable
transformer.

C.T. Raymond
6/25/07