Overall Transformer Diagnostics with routine and advanced technologies

Duration: one day

Presenter:          Diego Robalino, Principal Engineer, Megger North America

Short course description


  • Understanding the need for transformer maintenance and diagnostics

o   Reference Standards and latest updates

  • IEEE
  • IEC
  • NETA
  • Electro-magnetic Condition Assessment

o   Routine Testing

  • Transformer Turn Ratio & Polarity
  • Static Winding Resistance
  • Leakage Reactance
  • Excitation Current

o   Core saturation and demagnetization

o   Sweep Frequency Response Analysis

  • Test Modes
  • Correlation with routine tests
  • Interpretation of results


  • Insulation Diagnostics and Condition Assessment

o   Dielectric Frequency Response (DFR), Capacitance and Power Factor (C & PF) diagnostics

  • Fundamentals of Capacitance, PF and DFR testing methodologies
  • Temperature dependence of power factor – Table or Individual Temperature Correction
  • Application on Power & Distribution Transformers (XY model)
  • Application on Bushings and Instrument Transformers
  • PF of insulating liquids
  • Voltage Dependence
  • Status of IEEE DFR guide
  • Case Studies

o   Liquid Insulation Analysis

  • Sampling and Testing
  • Fundamentals of DGA and Interpretation methods


About the presenter

Dr. Diego Robalino currently works for Megger as a Principal Engineer, where he specializes in the diagnosis of complex electrical testing procedures for primary substation equipment. While doing research in power system optimization with a focus on aging equipment at Tennessee Technological University, Robalino received his electrical engineering Ph.D. from that institution. With an international background spanning the distance from South America to Eastern Europe, he’s garnered additional education experience in project management and electric drives/automation. Robalino has 20+ years of involvement in the electrical engineering profession with management responsibilities in the power systems, oil and gas, and research arenas managing the design, construction and commissioning of electrical and electro-mechanical projects. Dr. Robalino is a senior member of the IEEE and member of the IEEE transformers main committee where he actively participates in the development of guides and standards specially related to FDS/DFR technology. Other memberships include ASTM and PMI. His multidisciplinary engineering interests had  lead him to author and co-author papers and articles, as well as present at major international energy industry conferences and association meetings representing Megger.