Study of piezoelectrets for detecting partial discharge in transformers

Author(s)

Yvan Gutnik

• Document type: Master's Dissertation
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2014-04-25

Examining board members

Ruy Alberto Corrêa Altafim; Arnaldo Gakiya Kanashiro; Cacilda de Jesus Ribeiro

• Advisor: Ruy Alberto Corrêa Altafim

Abstract

Partial discharges acoustic detection is a very important preventive and predictive maintenance tool for transformers. In this research, a new acoustic piezoelectric sensor, based in Brazilian technology, was presented. However, before the construction of the prototype, an extensive literature was analyzed, including partial discharge, methods of discharges detection, piezoelectricity, electrets, piezoelectrets, manufacturing of the piezoelectret proposed to detection of discharges and signal processing tools, in special the homomorphic deconvolution. Basically, the prototype developed consists of a piezoelectret sensor and an amplifier circuit, assembled in a special metallic box, to shield any electromagnetic interference. During the tests, it was detected the need to create new circuits and to improve laboratory methodologies. A new impulse high-voltage generator electromagnetically shielded can be cited as an example of these circuits here developed. The new testing methodology aimed to present the evolution of the acoustic behavior of a discharge in different environments, in other words, from signals without echoes to signals containing echoes and distorted by the environment. In the processing signals context, another important contribution was the decision to analyze the acoustic signals of partial discharges by homomorphic deconvolution, which has allowed the reconstruction of the original acoustic signal without echo. (AU)

• FAPESP's process: 11/04960-3 - Piezoelectric sensors based on thermo-formed and cold piezoelectrets for acoustic detection of electrical discharge into power transformers
• Grantee: Yvan Gutnik
• Support Opportunities: Scholarships in Brazil - Master