Introduction: The University of Manchester will be building on three successful phases of the transformer research consortium, which has delivered world class research and results. Phases 1 and 2 focussed on the use of synthetic and natural esters in transformers at transmission voltage levels, this work led to sufficient understanding of the technology for National Grid to be able to deliver an inner London substation design incorporating synthetic ester filled transformers. Some of the successes delivered within Phase 3 were:

• progress was made in the interpretation of methanol and ethanol as potential early indicators of transformer insulation ageing. The rates of production by oil and paper and the partition between the two is now better understood. More data and case studies are required to evaluate the usefulness further

• a methanol measurement technique was developed, benchmarked within IEC and transferred to the oil analysis service provider for routine testing.

• study of oil result database for the participating utilities led to conclusions about the relative merits of different tests to show when oil is degraded. Different diagnostic techniques were compared and recommendations for possible improvements in IEC guidance were made.

• extensive laboratory testing has developed our understanding of dissolved gas production under different fault conditions. The same experiments have improved our knowledge on the response of on line gas monitors

• very useful insights have been gained into partial discharge inception and propagation in ester fluids that might lead to a revision of transformer test requirements

• Computational Fluid Dynamic (CFD) studies have shown up significant issues with existing techniques used by manufacturers offering the promise of better designs. Experimental studies have been used to successfully validate the CFD models.

Phase 4 will continue to investigate all of these areas in more depth.Under the original TOPICS project, the University of Southampton investigated corrosive sulphur issues in transformers, delivering improvements in oil reclamation operating procedures to prevent corrosion of silver, especially tap-changer contacts and a greater understanding of the failure mechanism involved with copper sulphide deposition. Research is required to investigate further aspects of oil reclamation and mitigation of corrosive sulphur in transformer oil.

Objectives:

Leading experts and academics have discussed and established a number of areas of research which has been developed into the following packages of work.

The University of Manchester program of work will investigate the following:

WP1 -  (i) Review existing loading guides for mineral oil immersed transformers to optimise operational performance and develop fundamental understanding on key factors influencing bubble formation in alternative liquids immersed transformers to ensure reliable operation.  (ii) Assess the applicability of retrofilling for life extension and/or uprating of transformers and investigate the gelling phenomenon and possible negative impacts of natural ester thin films.
WP2 - (i)  Analyse ageing results published in the literature to inform laboratory ageing experiments. Use the ageing results as well as considering ageing mechanisms, functional change of oil and paper and the end-of-life points so as to help forge the specification criteria for alternative materials which are equivalent to the ones used in IEC 60422 (oil management) and support transformer replacement decisions. (ii)  Support interpretation of oil testing through the study the dynamic behaviour of ageing markers in a model transformer under various loading profiles and recommend the temperature based calibration methodology for ageing markers. 
WP3 - Maximise the utilisation of growing databases for transformer condition assessment and develop database analysis methodologies to support transformer asset management. 
WP4 - (i)  Apply developed CFD modelling capability in simulating different winding designs and their manufacture tolerance, provide guidance for key parameters governing thermal design to support specification and design evaluation during transformer procurement. (ii)   To support ongoing operation of a design with known cooling issues, develop a complete transformer CFD model including windings and cooling system, and study the temperature profile under various load levels.
WP5 - (i)  Correlate PD partial discharge (PD) characteristics of transformer liquids detected by ultra-high frequency (UHF) sensor with conventional PD detector and high speed imaging technique. Investigate the effects of tip radius/oil quality on PD and breakdown performance of transformer liquids. (ii)  Characterise creepage discharges on alternative liquid-solid interface for applications in transformers and tapchangers.

The University of Southampton programme of work will investigate the following:

WP1 – Investigate a relatively new phenomenon of ethylene as a single fault gas experienced in some transformers by use of high temperature flow reactors to investigate conditions leading to ethylene production from mineral oils, and propose mechanisms for its formation and potential mitigation strategies
WP2 – Support oil management in older transformers through investigation of the potential for mechanical damage to aged insulation paper caused by either the flow of oil or abrasion, through the action of suspended particulates
WP3 – (i) Evaluation of techniques to remove elemental sulphur from contaminated transformer oil and thereby reduce the risk of silver corrosion in tap-changers and the remediation work required to restore condition  (ii) Understanding silver corrosion in contaminated and aged transformer oil
WP4 - Electrical and spectroscopic techniques will be assessed as measurement methods to quantify corrosive sulphur species in transformer oils as a way of identifying where copper corrosion may be occurring.

Expected Benefits: The outputs from the research being undertaken will provide the industry with improved knowledge and understanding of the optimised asset life and asset management of Transformers and Transformer Oil.