Corhodzic, Selver (2006) A New Approach to Assessment and Utilisation of Distribution Power Transformers. PhD thesis, Victoria University.

Abstract

Electrical power systems utilise several voltage levels using power transformers to transfer voltages and connect parts of the power system with different voltage levels. One of these voltage transformations is being performed in the key component of the electrical power system: the distribution power transformer. It connects the Medium Voltage (MV) 11 kV - 33 kV networks and the Low Voltage (LV) 415 V networks, enabling connection of a large number of LV customers as well as (though to a much smaller extent) access of embedded generators to the electrical distribution network. Although the Australian distribution power transformers are considered to be very efficient devices (Minimum Energy Performance Standards - MEPS Fact Sheet, 2004), still roughly 3.2% of distribution transformers’ throughput electricity is lost due to their inefficiencies. The magnitude of these significant losses attributed to distribution transformers is a consequence of: • inefficiencies due to the design, materials and technologies used in distribution transformers; • inadequate type and rating of transformers selected for a particular application. The commitments of various Australian stakeholders (the public, the government agencies, distribution utilities, regulators, electricity industry trade associations, etc.) to limit emissions of greenhouse gases and to actively contribute to the global efforts to protect our environment are closely related to the energy market reform. The recent partial deregulation of the Australian electrical supply industry has introduced competition in retail and generation sectors and also significantly changed the operational environment for the electrical distribution companies. The era of increased competition for capital has commenced. The state based regulators have reduced incentives for over-investments, however, they still request enhancement of quality of supply and improvements of customer services. These, sometimes conflicting requirements have forced the electrical distribution utilities to move focus from improving economic efficiency of electricity supply and abandon long established practices for evaluation of distribution system performances applying multi-level economic analyses and systematic assessment of performances of key system components. It seems that “low initial cost” method (without proper assessment of total life cycle costs) is becoming much more attractive solution for selection of distribution equipment. The expected steady increases in energy demands and the need to undertake effective measures to protect the environment could be partially solved by improving energy efficiency of electrical equipment. The recent focus of the Australian government on the environmental costs associated with use of electrical energy has brought the efficiency of electrical equipment (including distribution transformers) under the spotlight. Highly efficient, yet cost-effective distribution power transformers, which are fully optimised for the expected service conditions (the likely load and the operating environment), are obviously the right solution for reduction of electrical losses. Introduction and use of such equipment would present significant challenge for electrical distribution utilities and private users of distribution transformers as this would have a considerable impact on their competitive position under the new industry structure. This research explores potential design improvements and increase in efficiencies for distribution transformers trough analysis of existing design and manufacturing technologies, relevant international regulatory developments, technological advancements and general trends in the context of the Australian market. It analyses the recently introduced mandatory Minimum Energy Performance Standards (MEPS) for distribution transformer and suggests courses of action for industry, regulatory bodies and the end users, which could help to ensure that those actions are part of the global solution for complex environmental issues. In addition, this research investigates a new two-stage approach for evaluation, assessment and utilisation of distribution power transformers and as such, to some extent, is directed towards a rational risk management and technical methodology to allow Australian electrical utilities and other interested parties to deal cost-effectively with present conventional technologies for distribution transformer used by major Australian manufacturers. The new assessment method for distribution transformers is based on: • development of cost efficiency schedules for selected designs and representative kVA ratings; • thorough financial analysis of distribution transformer losses. This refined methodology highlights importance of design and costing stages in the assessment process. Further, it recommends moving from simple capitalisation of transformer losses by extending evaluation of the total operating costs through introduction of new evaluation factors based on life cycle cost concepts and on expected service and loading conditions. This research is a contribution towards development of new procedures and methodologies, which will provide guidelines and recommendations for improvement of distribution transformer performances and increase compatibility of needs and capabilities of various stakeholders: end users, standards’ setting bodies, regulators, research organisations, equipment manufacturers, designers and consultants.

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