Technical library

Improved transformer insulation assessment using dielectric response analysis.

The increased usage of the phase shifting transformers in various fields within power systems has introduced new challenges in performing on-site maintenance testing.

This paper will demonstrate the advantages of applying a variable low frequency AC waveform and, using temperature-to-frequency conversion techniques developed, and also the ability to correct any resistance value automatically to a to a known temperature corrected result.

The necessity of HV cable testing is a given fact. So far, two testing methods, 24 hour soak or resonance testing are commonly used. This paper describes a comparison of test power demand dependent from voltage shape and test capacitance as well as the power consumption of test systems for different test techniques.

This paper discusses the investigation of the tripping of a 400 kV substation due to improper operation of a bus-bar protection scheme.

Dielectric testing techniques in the time and frequency domains are increasingly being used by transformer manufacturers, power utilities and researchers for transformer oil-paper insulation systems condition assessment.

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.