Abstract :
RECENT DEVELOPMENTS in the knowledge of the factors influencing the rate of deterioration of insulating materials have extended the power of engineering statistics for determining the amount of accrued physical depreciation in electric equipment. Procedures based on these developments and adapted to the particular case under investigation should be of considerable help in valuation work. A short time ago the author had occasion to determine the depreciation of the electrical components of a utility property of substantial size containing a number of generators and transformers of varying age. Recognizing the importance of heat in the deterioration of insulating materials, an investigation was made of the company´s records with respect to the age and temperature history of the windings of the individual items of equipment, to which this principle was applied with gratifying results.
