End of Life 1

[mpparent]

All,

Is there an IEEE standard that says, TYPICALLY with ongoing maintenance and normal use, a unit substation, dry type transformer(from 1000kVA to 5000kVA) is End of Life after??? I seem to recall a figure of 30 years, but I'm not finding it.

Mike

 

[alehman]

no

 

[RajT]

The 30 year life is a period quoted by transf manufacturers based on historical data. What it really means is that after 30 years the transf has had a good life and that a sudden failure can be expected at any time thereafter and thus it is considered wise to change out the unit at an earliest oppertuinity

 

[jwerthman]

According to ANSI/IEEE C57.96 (Guide for Loading Dry-Type Transformers), the normal life expectancy for transformers operated within the basic loading conditions is 20 years. The basic loading condition is continuous full-load kVA at rated voltage and 30 degree C 24-hour average ambient (not exceeding 40 degrees C).

 

[mpparent]

Thanks for all of the replies..

You get a star jwerthman..

Mike

 

[njengr1]

Anyone know of any reliability surveys that include dry power transformers in the 500kva to 2500 kva range. Specifically, the mean time to failure or life expectancy.
Looking for 4160 to 13.8kV types

 

[busbar]

One reference is Appendix G — Report of transformer reliability survey in IEEE Std 493-1997 …Design of Reliable Industrial and Commercial Power Systems [Gold Book] but it looks primarily based on liquid-filled transfomers. Drytype transfomers seem to be “newer” than oil in the listed range, so it may be more difficult to find significant reliability data. With more recent improvements in materials and processes, newer dry designs may also have increasing lifespan.

An example of one undesirable rating combination sometimes found in drytypes of this range are 15kV-class primaries with 60kVBIL ratings, where 95kVBIL is standard for oil-dielectric equivalents.

 

[jbartos]

Suggestion: Visit

http://www.usace.army.mil/publications/armytm/tm5-811-1/chap4.pdf

for:
Complete coordination should be performed to ensure proper
protection for electrical equipment and systems, to obtain the required degree of availability, reliability and maintainability, and to achieve the most cost effective billing, construction, operation and maintenance costs during a station life of 25 years or less.

 

[electricpete]

I concur with busbar, the Gold Book appendix is the only authoratative source that I know of.

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[jbartos]

Suggestion: Visit

http://www.copper.org/applications/electrical/energy/trans_efficiency.html

for:
Most transformers are designed to operate for a minimum of 20-30 years at the nameplate load, if properly sized, installed and maintained. Transformers loaded above the nameplate rating over an extended period of time may have reduced life expectancy.

http://oee.nrcan.gc.ca/egi/english/dry_type/dry_save.cfm?PrintView=N&Text=N

for: 30 years of useful life-expectancy