How to evaluate oscillogram during impulse tests in transformer of high voltage?

I live in Brazil and I work in the Quality Area ( Inspector of Electrical Equipment ).

I am researching new methods and forms to understand the impulse tests applied

in high voltage transformers and bushings ( above 500 kV) .

So, I would like your help in the following subjects :

Is there a specific paper and/ or a specialist engineer who I can contact

to talk about :

a) How to evaluate and interpret the different wave forms of

oscillogram when a failure happens in the transformer´s winding during

impulse tests?

b) How to diagnose dieletric failures in the transformer´s winding

during impulse tests, analysing and seeing the oscillogram ( wave form) ?

My principal aim is see different wave forms showed at oscillogram and if

they indicate any failure then I do have conditions to evaluate it and

elaborate my conclusion.

Answer to :

Cláudio Morais

my e-mail is : cmorais@itaipu.gov.br