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eng 1 Hz dissipation factor
Rabalino, Diego; Oppedisano, Vince; Petrof, Kenneth
Transformers Magazine Vol. 9, No. SE1, 2022
The dielectric frequency response has evolved into a definitive analysis to determine the condition of the insulation system. The analysis of the NB DFR tests spectrum provides valuable pieces of information that can be used for the diagnostics of high voltage equipment. A case study has been conducted for a 10 MVA, 69/13.09 kV Dyn1 two-winding transformer that is tested in the field after OLTC repairs and before re-energization.
Hrčak ID: 277837


eng Oil-impregnated paper bushing insulation diagnostics
Robalino, Diego; Güner, Ismail; Werelius, Peter
Transformers Magazine Vol. 4, No. 5, 2017
As reported in CIGRE TB 642, windings, tap changers and bushing related failures are the major contributors to transformer failure. About 17 % of transformer breakdowns are caused by bushing failure which is often followed by explosion, tank rupture, fre and potential human harm. To date, the insulation system in high voltage and extra-high voltage bushings is mainly oil-impregnated paper and resinimpregnated paper; in fewer cases, resin-bonded paper. Some of the advantages of using oil-impregnated paper bushings, listed in CIGRE TB 445, are th...
Hrčak ID: 195048


eng HV instrument transformer condition assessment
Robalino, Diego
Transformers Magazine Vol. 6, No. 5, 2019
This article discusses the application of dielectric frequency response for the analysis of the insulation in MV, HV and EHV instrument transformers. Overall condition assessment of instrument transformers should not be limited to the analysis of the electro-magnetic circuit; it must also include a reliable method to analyse the insulation of instrument transformers.
Hrčak ID: 228366


eng A smart way to minimize test time for transformer dielectric measurements
Duplessis, Jill; Ohlen, Matz
Transformers Magazine Vol. 2, No. 4, 2015
Dielectric response measurements for the moisture and oil conductivity assessment of transformers are well understood, internationally accepted and growing in use. Of the two principal dielectric response methods, an AC method called Dielectric Frequency Response (DFR, also Frequency-Domain Spectroscopy, FDS) is preferred due to its robustness against noise. The time requirement of a DFR measurement is lengthy compared to that of other electrical test methods. An earlier approach to accelerate test time combined DC (time domain) and AC (frequen...
Hrčak ID: 181931


eng Why is water killing power transformer insulation?
Anglhuber, Martin
Transformers Magazine Vol. 4, No. 3, 2017
Water is a threat to the insulation of oil (or ester) insulated power transformers. It leads to reduced breakdown strength of the oil and an accelerated aging of the cellulose insulation. Dielectric frequency response analysis is a suitable and accurate way to assess the water content of the insulation and it helps to determine the condition and remaining lifetime of the transformer. Prior drawbacks of this technology, such as long measurement times and complex assessment, can be eliminated using modern software. The polarization depolarization...
Hrčak ID: 185304