Technical Session Highlights

Yaw Nyanteh - HICO America

For design purposes, the interaction between the electromagnetic field and the active components can be split into two (2): high and low frequency regimes. It is usual to assume that during the high frequency regime, the inductive reaction of the windings compared to the capacitive reaction is marginal. Hence the transformer design focuses on the capacitive aspects of the windings during the first few micro seconds. The conventional definition of the magnetic vector potential is then utilized as a means of computing the magnetic field when the inductive reactance is engaged in all of the winding sections.

This presentation will introduce a different definition of the vector potential that provides an alternate interpretations of transformer action. It will be shown how this potential can be used to determine the response of winding (turns, sections etc.) during impulse. Some conventional design and manufacturing considerations for higher voltage class windings will be highlighted to show how these windings are manufactured to withstand high voltage impulses in the field.

Drew Welton - Vice President of Sales

One of the more common causes of mechanical failure in power transformers (PT) comes from exposure to through faults. Most of today’s transformer protective relay systems provide comprehensive monitoring of these potentially damaging events but are rarely activated. In this paper we will define the characteristics of a through-fault, investigate various proper settings for a through-fault monitor, and present an actual case study of a severely damaged transformer exposed to this condition. We will also see examples of detecting mechanical failure in the transformer as it relates to a through-fault condition.

Kenneth Petroff - Megger

Electromechanical testing is at the heart of transformer assessment; from the factory to the field, turns ratio, winding resistance, and short circuit impedance tests are performed to ensure that fundamental transformer components, the winding, core, and tap changers, are fit for continued service. This presentation unveils some unknown factors influencing fundamental testing and provides guidance to novel methods simplifying transformer testing and securing long term operation.

Bruce Forsyth - Cargil

The trend to use natural ester liquid rather than fossil-fuel-based mineral oil in liquid-filled transformers continues to rapidly increase. Natural ester liquids offer three primary benefits over mineral oil. These include a) significantly higher fire safety, b) higher biodegradability and other environmental benefits, and c) reduced aging of the cellulose insulation, which allows increased life expectancy and/or the ability to increase the capacity of the transformer without decreasing its life expectancy compared to a mineral oil filled transformer. 

This presentation focuses on the specific mechanisms that result in reduced aging of cellulose insulation in natural ester liquids, and the options they present to transformer users. 

Vince Oppedisano - Megger

Transformer maintenance has long explained the methods, diagnostics, and the merits of offline transformer testing. It is well understood, and the equipment used for measurements is well established. On the other hand, dissolved gas analysis is relatively new, with many myths and beliefs shared amongst people in the transformer field. Whether it is using oil labs (with extracted oil samples), or more recently, the online DGA instruments (oil is always present for measurement)used for field assessment, one requires a basic understanding of the technologies used, the limits and advantages for each, together with the diagnostic tools used to find issues and prevent the early loss of a transformer. 

This presentation explains the most common technologies used for dissolved gas analysis and provides insight into which is best suited for specific applications, while also providing a basic review of the methods used for alarm conditions and diagnostic assessment. 

Sami Debass - Electric Power Research Institute (EPRI)

This presentations summarizes the lessons learned from recent failures happening in different utilities around the world. It is important to highlight not only the technical impact of critical equipment failure, but also, the financial and social impact for the utility and the community. The presentation will look into reported failures and will open the discussion about How to mitigate future failures.

Volney Naranjo - Renewables Business Development Manager

A known and significant challenge in the renewables sector is the early degradation of transformers associated to solar photovoltaic and wind generation. This affects the reliability, efficiency, economic performance, operation as well as the public perception of the renewable industry. This session explains the common causes of early degradation, provides a review of mitigation approaches, and discussed the recommended maintenance and testing practices to extend the life of the transformers in a renewables fleet.