Diagnostics of technical condition on load tap changers by acoustic emission method using different types of measuring transducers

Results of scientific research works considering selection of measuring transducer applied for registration of acoustic emission (AE) signals generated by on load tap changers (OLTC) are presented in the paper. During the coupling process AE signals are generated by: the mechanical setup of tap changer, contacts operation and partial discharges. For most OLTC types, the working medium is insulation oil in which the acoustic wave being formed propagates to the steal tank. There exists a possibility to register AE signals with a piezoelectric transducer attached to the outer tank surface or with a hydrophone immersed in the oil. AE signal obtained in such manner contains information which describes operation of the power tap changer and the selector. A comparative analysis of AE signals generated by OLTC working under laboratory conditions in three setups, each applying measuring transducers with different transmittance, is presented in the paper. In measurements three types of transducers were applied: wide band transducer type WD AH-17 from Physical Acoustics Corporation, hydrophone type TC4038 from Reson and accelerometer type 4514 - B - 001 from Brüel & Kjær. The comparative analysis was performed in order to determine their suitability for OLTC technical condition diagnosis. Based on the results achieved one transducer which allows the registration of acoustic events generated by the mechanical setup as well as by electric phenomena occurring during OLTC operation was selected.