Ali Naderian
Project Manager of High Voltage Testing
Kinectrics Inc.

The dryness and aging state of oil-paper insulation is a key factor in reliability of a power transformer, since moisture has deleterious effects on dielectric integrity and insulation aging rates. Water in oil paper insulation decreases the dielectric withstand strength, accelerates cellulose aging and causes the emission of bubbles at high temperatures. Knowledge of the actual moisture concentration is required in order to decide for further actions as for example on-site drying.

Current methods to estimate paper moisture from the oil are inaccurate. To use equilibrium diagrams, transformer has to be in equilibrium state which is hard to achieve and to detect this state. For spare transformers which are cold, the traditional methods can cause huge error up to 200% to 400%. In the last 2 decades, dielectric diagnostic methods have been developed, take advantage of the strong correlation between moisture in paper and pressboard and the dielectric properties like polarization currents and dissipation factor. These methods promise to give higher accuracy and are designed for onsite moisture determination.

In this presentation the basics of the Dielectric Frequency Response (DFR) test, interpretation, and application will be presented along with a few case studies results

Ali Naderian received his B.Sc. and M.Sc. degrees from Sharif University of Technology in 1998 and the University of Tehran in 2000, respectively. During studies, his part-time employment experience included ISC (1997-1999) for design and testing of switchgear, and ITS (1999-2001) for designing and testing of power transformers and testing transformers. He was co-designer of a 3x300kV cascade HV testing transformer. He compared commercially available RTV coatings for outdoor insulators in his PhD thesis during his research at the University of Waterloo (2003-2006).

He has been a project manager of high voltage testing at Kinectrics Inc (Formerly Ontario Hydro Research) since 2006 working on diagnostics of power transformers, high voltage cables, and outdoor insulators. He performs on-line and off- line PD measurements for HV apparatus. His research interests include partial discharge, dielectric frequency response, and frequency response analysis. He is a registered professional engineer in Ontario and a member of the IEEE Transformer Committee, an active member of IEEE Dielectric Frequency Response Task Force, IEEE PC57.152 Transformer Field Test Guide, and C57.125 Failure Analysis and Reporting Guide