Final Report of the 2004 - 2007 International Enquiry on Reliability of High Voltage Equipment - Part 4: Instrument Transformers

Results from a world wide utility survey of failures and service experience with instrument transformers rated for 60 kV and above are presented. The surveyed service experience comprises 1 290 335 single phase instrument transformer years. Statistical information about 690 major and 2 489 minor failures - such as origin, cause and failed subcomponent - are provided. In addition, failure frequencies as a function of voltage level, technology, age, design and maintenance strategy are presented.