Sawtooth-Based FDS for Rapid and Accurate Testing of Transformer Oil–Paper Insulation

Frequency domain spectroscopy (FDS) is a common nondestructive test method for insulation diagnosis of a transformer. Rapid and accurate testing can help improve the efficiency of FDS. However, the long test duration of conventional FDS and the unsatisfactory accuracy of existing accelerated FDS methods limit the application of insulation conditions of transformers. To tackle these problems, a new testing method named sFDS is proposed, aiming to achieve rapid and accurate testing. The proposed sFDS consists of two main parts to achieve the goal: first, the test duration is reduced by using sawtooth and regression analysis. Second, to ensure test accuracy, a multidomain signal accurate processing technique is proposed. Specifically, first, a filtering algorithm is used to isolate the noise. Second, the phase correction is used to improve the precision of time-frequency conversion. Third, the line interpolation method is utilized to accurately extract spectral data to compute dielectric loss and complex capacitance. To verify the practicality of sFDS, an sFDS test platform is built and compared with existing accelerated FDS techniques through practical experiments. The results indicate that sFDS performs superiorly in rapidity and accuracy. Meanwhile, sFDS has the potential to become a general method for evaluating more electrical objects.