SOUSA, W. V.; http://lattes.cnpq.br/4590372632393871; SOUSA, Wallysson de Vasconcelos.
Résumé:
The objective of this work is to propose a classification technique for contact
degradation level of circuit breakers, providing an indication of their operation status,
in order to determine the most appropriate time to carry out interventions and, thereby,
contributing to reduce interruptions. The dynamic resistance measurement (DRM) is a
diagnostic technique used to evaluate this degradation. The same is shown capable
of analyzing both the main and arcing contacts. All tests performed for this thesis used
DRM curves generated with reduced contact opening speed, and various test current
levels. For the tests, an alternative measurement system was adopted, consisting of a
digital oscilloscope, a stationary battery, voltage and current sensors and chromealuminum-
iron resistors. The system is able to determine the resistance values since
the beginning of the contact opening process until its total separation, allowing the
application of a test current up to 300 A. To reduce the contact opening speed, a new
system was designed, which consists of a speed reducer coupled to an asynchronous
motor, which is controlled through a frequency converter. The classification of the
contact degradation level was done in this work using Wavelet transform. The results
obtained using the Wavelet transform were compared to those using as a criterion the
prior knowledge of each sample degradation level. The results analysis highlights the
Coiflet 6 Wavelet as the most suitable for the classification of contact degradation level
of high voltage circuit breakers.