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Acoustic Emission Technique


 Acoustic Emission is a non-destructive, non-invasive test technique that is very useful in detecting internal defects in materials and equipment.


Among the advantages it presents can be highlighted: ease of application; low cost; possibility of carrying out the tests with the equipment in operation; detection and analysis of defects in real time; immunity to electromagnetic noise; possibility of three-dimensional location of defects.

Acoustic signals, generated inside the equipment in operation or when subjected to programmed efforts, bring important information about the integrity of these equipments. These signals are usually associated with the presence of internal defects or they can be characteristics of the equipment and its components characteristics.


Although already consolidated in other technological areas, for which it is already well established with standards, test procedures and evaluation criteria, the Acoustic Emission should be considered as a developing technique, whose potentialities have not yet been fully explored.

Firstly, as a technique for the detection of partial discharges in transformers, it is verified that this is only one of the possible contributions of the Acoustic Emission, because, due to its characteristics, it allows the detection of a large number of defects in these equipment , which may be of electrical or mechanical origin and may also lead to catastrophic failure.

Cepel, for more than 15 years, conducts studies aimed at the application and development of methodologies employing the Acoustic Emission technique. His experience in the testing of transformers and reactors is based on more than a hundred equipment evaluated, providing a large number of characteristic events that are being classified aiming at the formation of a database with its acoustic signatures.


Regarding Acoustic Emission technique, the main activities developed are:

1) research and development of methodologies for the diagnosis of high voltage equipment: online tap changer, SF6 gas insulated substations, power transformers, reactors, current transformers, circuit breakers etc;

2) studies and development in the areas of signal characterization and three-dimensional location;

3) search and classification of patterns and application of artificial intelligence;

4) formation of database of acoustic signatures;

5) provision of technical support for implementation of the technique in companies of the Electric Sector;

6) personnel training;

7) participation in standardization committees;

8) more than a hundred transformers and reactors evaluated by the technique, on site and in laboratory


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