Regional Technical Seminar

Agenda: Megger On-line Monitoring Regional Technical Seminar - June 23rd 2026

Advanced Field Testing Techniques for Transformer Life Extension

Abstract:

Recent revisions to IEEE C57.152, Guide for Diagnostic Field Testing of Fluid-Filled Power Transformers, Regulators, and Reactors, provides updated guidance on advanced field‑testing methods for power transformers. These advanced techniques can help detect and mitigate insulation, mechanical, and electrical degradation, thereby reducing the risk of premature failures and potentially catastrophic events. Given the exceptionally long lead times and rising costs associated with transformer replacement, accurate condition assessment of these critical and expensive assets is more important than ever. This paper will also address advanced methods for bushing evaluation as an integral component of comprehensive transformer condition assessment.

Offline Cable Diagnostics and Methods

Abstract:

Offline diagnostic testing of medium- and high-voltage cable systems has become an essential component of modern asset management and reliability-centered maintenance programs. Traditional withstand testing alone is often insufficient to provide a complete assessment of cable condition, particularly in aging infrastructure and critical utility applications where early defect detection is necessary to prevent unexpected failures. Advanced diagnostic techniques such as Tan Delta (TD) and Partial Discharge (PD) testing provide valuable insight into insulation health, degradation mechanisms, workmanship defects, accessory conditions, and localized insulation weaknesses before catastrophic failure occurs.

This session discusses modern offline cable diagnostic methodologies with a primary focus on Damped AC (DAC) technology and its application in PD detection and localization. The advantages of DAC excitation compared to conventional VLF sinusoidal testing are explored, including reduced stress on cable insulation, improved sensitivity for PD measurements, and enhanced suitability for long cable systems and aged assets. The session will also examine the integration of Tan Delta measurements alongside PD diagnostics to provide a more comprehensive evaluation of cable condition and insulation aging.

Special emphasis will be placed on PD localization techniques, interpretation of PD patterns, calibration considerations, and practical field challenges encountered during testing of shielded power cable systems. Real-world case studies will demonstrate how combined diagnostic approaches using DAC, Tan Delta, and PD testing can improve maintenance decision-making, reduce unplanned outages, and support condition-based asset management strategies. The session will further discuss best practices, limitations of various testing methods, and considerations for selecting the most appropriate diagnostic approach for different cable system applications.

Presented by: Yash Godhwani

Yash Godhwani is the Cable Applications Team Lead at Megger, where he has been contributing for over six years. He holds both bachelor’s and master’s degrees in electrical engineering and has extensive experience in transformer testing and substation asset diagnostics. His expertise lies in advanced cable testing and diagnostics, including partial discharge analysis, tan delta, very low frequency (VLF) testing, and fault location. Yash is also an active member of IEEE and CIGRE, reflecting his commitment to advancing industry knowledge and best practices.

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