Detection of insulation deterioration through electrical spectrum analysis

Several types of insulation deterioration common to large rotating electrical machines produce Electromagnetic Interference (EMI) at discrete frequencies or within bands of frequencies. This paper employs the use of standing wave calculations to predict these natural resonant points. Curves of measured impedance variation with frequency are presented to verify calculated values. Determination of these resonants is an important first step in real time monitoring and later physically locating a defect before failures occur.