Dielectric Frequency Response (DFR) Analysis to Assess Condition of HVDC Converter Transformers

Abstract

Dielectric Frequency Response (DFR) is an advanced, non-destructive diagnostic tool used to assess the condition of transformer insulation. One important milestone for wide acceptance of DFR was the publication of IEEE Std C57.161-2018 “IEEE Guide for Dielectric Frequency Response Test” [1]. The Guide includes recommendations for instrumentation, procedures for performing the tests and has proven its effectiveness in relation to transformers of various applications and voltage levels. However, the guide lacks specific clarity regarding High-Voltage Direct Current (HVDC) converter transformers. Some recommendations of the Guide may lead to misinterpretations and inappropriate service actions that could compromise asset reliability. Given the rapid global growth of HVDC infrastructure and growing demand for reliable operation of HVDC transformers, this paper identifies recommendations that may lead to diagnostic errors and proposes targeted improvements for condition assessment of HVDC transformers using DFR. The results of this study will be reported to the IEEE working group responsible for the revision of the C57.161 DFR Guide.