Search for the following keywords: Electrical and thermal stresses reliability, insulation aging, loss of life, effect of over loading, Arrhenius Model, etc.
Power Equipment: Transformer, motors, breakers, etc.
The following institutions are good source of information:
1- USA: IEEE, EPRI, NEMA,EEI, BPA, LAWD, TVA, NASA
2- Institution abroad: GIGRE, IEC, IEE
3- Manufacturers: GE, ABB, Alstom, Siemens
4- Recommended Standard references:
IEEE Std 101-1987: IEEE Guide for the Statistical Analysis of Thermal Life Test Data.
IEEE Std 99-1980 - IEEE Recommended Practice for the Preparation of Test Procedures for the Thermal Evaluation of Insulation Systems for Electric Equipment
IEEE Std C57.91,92 & 115 : IEEE Guide for Loading Mineral-Oil-Immersed Transformers.
ANSI/IEEE C57.96-1989
An American National Standard IEEE Guide for Loading Dry Type Distribution and Power Transformers
IEEE 56-1977 IEEE Guide for Insulation Maintenance of Large Alternating-Current Rotating Machinery (10,000 kVA and Larger) 1977