An approach to life estimation of electrical plant components in the presence of harmonic distortion

Harmonic distortion can affect significantly the reliability of electrical plant components by increasing the degradation rate of electrical insulation. This paper presents life models which enable estimation of failure times of the electrical insulation of the main components of industrial electrical plants, i.e. capacitors, cables, motors and transformers, when the prevailing aging stresses are voltage and temperature and harmonics give rise to considerable voltage and current distortion. The models are inserted in a probabilistic framework, which accounts for the inherently random nature of harmonics. It is shown that the degradation rate can become much larger than in the sinusoidal case, especially due to the contribution of harmonics to voltage peak magnification: also current distortion can play an important role. Hence, significant life reduction can be expected in the components which are subjected to harmonics.