ABSTRACT
A power system is composed of a number of components, such as lines, cables, transformers, circuit breakers and disconnectors. Electric power components are typically assigned a capacity rating and an estimated life. The two parameters are related, and it is assumed that if the component does not experience overloading an excess of its rating, it will stay in service in the stated useful life, whereas if it experiences excessive loading, its useful life will be decreased. During it useful life, electrical equipment experiences multiple stresses that affect its performance. These factors are electrical stresses voltage, current, on-off cycling, overloading, electrostatic discharges PD and corona, mechanical stresses vibrations, shocks, extreme temperatures and temperature changes, humidity, corrosive environment and dust. However, many failures often considered normal life failures are actually infant mortality failures. Wear-out is a fact of life due to fatigue or depletion of materials. A product’s useful life is limited by its shortest-lived component.
