Technical library

For testing and partial discharge (PD) diagnostic purposes many different test voltage wave shapes and frequencies have been established over the past years. Their application is well proven and is guided by IEEE 400 norm.

The dielectric response of the overall transformer insulation is an invaluable source of information for those involved in the manufacture, operation and maintenance of power and distribution transformers. One of the greatest advances in the use of the transformer insulation dielectric response is without a doubt the possibility of performing advanced diagnostics of the oil-paper insulation to determine the moisture concentration of the solid insulation and the quality of the liquid insulation.

The process of demagnetisation from the material viewpoint and its implications for transformer testing.

A cable replacement strategy and diagnosis method for water trees in XPLE cables has been developed at the Botkyrka 24 kV network. Measurement reports from 1996-2002 highlight improvements in age-analysis, overall effectiveness and cost.

Modern technology and developments in signal acquisition and analysis techniques have provided new tools for transformer diagnostics. Of particular interest are dielectric response measurements where insulation properties of oil-paper systems can be investigated.

This paper will talk about a non-traditional method of field testing that utilises the superposition of two waveforms of dissimilar frequencies to achieve a power swing and out-of-step condition.

Throughout this document, field experience is summarised when a three-winding transformer is removed from service and put to a series of testing procedures including DF, FDS and tip-up test on the high voltage bushings. Results of the analysis, experimental data and conclusions made based on the obtained results are presented herein.