An approach to insulation condition monitoring and life assessment in emerging electrical environments

Distributed generation, dc transmission and distribution, and power electronics for ac/dc/ac conversion bring the advantages of increased control and flexibility in electric power management. These advantages also introduce challenges that must be managed. An electrical environment where voltage is not anymore strictly sinusoidal implies that a new approach for the design and maintenance of electrical insulation systems has to be devised. Non-sinusoidal voltage supply often causes increased failure probability and, thus, reduced reliability and life of an electrical asset. This research addresses the implications of the transient and steady waveform distortion introduced by power electronic systems and dc supply, for which the electrical insulation was designed and tested through consolidated criteria based on sinusoidal voltage supply. Based on condition monitoring, a health index definition is proposed, which allows the condition of the insulation of an electrical apparatus to be assessed as a function of operation time, and, based on the aging and life models, the evaluation of maintenance actions and of the feasibility and extent of life extension plans to be carried out.