The Development of 400kV Class Synthetic Ester Transformers Products of M&I Materials Ltd.
Structure What is an ester? Industry trends for ester fluids History of esters in distribution and high performance transformers Experience to date in power transformers Cost benefits of ester fluids High voltage R&D Full scale testing and use in 400kV transformers
What is an Ester? The term ester comes from chemical linkage formed from the reaction of an alcohol & an acid Synthetic esters are manufactured from organic materials Carefully selected acids and alcohol to give chosen properties Natural esters are derived from plant oils Refined seed oils Examples include Rapeseed, Soya, Sunflower
Synthetic and Natural Esters Oxygen Stability Synthetic ester suitable for breathing and non-breathing transformers Natural esters need sealed transformer Cold Temperature Performance Synthetic ester suitable for cold climates (pour point = -56ºC) Natural ester high pour point (typically -18 ºC to -31ºC) Service History Synthetic esters have greater than 35 year history Natural ester only marketed since late 1990 s
Industry Trend for Ester Fluids Natural and synthetic esters have built up experience in distribution and small power transformers Long history of synthetic ester use in high performance applications Traction transformers Wind turbine transformers Offshore platforms Move towards higher voltage classes and larger power transformers Realisation of installation advantages from fire safety and environmental benefits
Power Transformers with Esters SYNTHETIC ESTER NATURAL ESTER High Voltage Rating Year High Voltage Rating Year 110kV 25MVA 1999 115kV 15MVA 2004 151kV 110MVA 2002 161kV 200MVA 2004 (retrofill) 238kV 135MVA 2004 230kV 8MVA 2005 (retrofill) 220kV 100MVA 2010 161kV 25MVA 2006 154kV 200MVA 2011 110kV 40MVA 2008 400kV 240MVA 2016 138kV 40MVA 2009 433kV 120MVA 2016 420kV 300MVA 2014 Development of synthetic and natural ester power transformers has happened in parallel The table shows a selection of the power transformers with synthetic and natural esters installed over the last 25 years
Cost Benefits of Ester Fluids Ester fluids bring benefits which can potentially cut installation costs Reduction in civil engineering costs due to higher level of fire safety Ability to place transformers closer to the load Removal of fire extinguishing systems, which are costly to buy and maintain Simplification of bunding schemes due to biodegradability of esters
FM Global Guidance Example
End-user: KWO Oberhasli AG SWISSI - Institute of Safety and Security Risk assessment & loss prevention consultants Conducted study to assess different fire safety situations Fire risk comparison of synthetic ester & mineral oil transformers Combinations of fluids and fire suppression systems investigated SWISSI investigated 4 fire safety options:- Mineral oil with nitrogen fire fighting system Mineral oil with water deluge system Mineral oil with sprinkler fire fighting system Synthetic ester with no protection measures
Case Study Findings Risk Mitigation: The synthetic ester option without fire suppression presented least fire risk Saving Space: KWO was granted permission that the four HV transformers as well as all distribution transformers were installed with synthetic ester Cost Benefit: Large saving in capital and maintenance costs
High Voltage R&D With Esters Many university research programs worldwide aiming to use esters at 400kV and above Corporate research programs by large OEMs ABB Siemens Alstom Grid Esters can be used for large power transformers Some adjustments to design due to impulse behaviour DGA is possible with esters
Impulse Breakdown of Esters
Full Scale 400kV Test with Synthetic Ester Joint project under UK OFGEM funding National Grid Alstom UK M&I Materials Testing of a full scale 400kV coil winding Results of testing allowed design of 400kV synthetic ester transformers National Grid decision to extend use of esters to 400kV
National Grid UK 400kV London Project Large scale project in a dense urban area Planning consent a major barrier Meet the needs of residents & planners Synthetic-ester design crucially delivered Increased fire safety Fire suppression benefits Less complex containment system Heat recovery system using waste energy Normal transformer operation Supply heat to residents & school Lower overall project costs Substation size (m²) Civil construction Containment & drainage Fire barriers/walls NG see this system as a future strategy Plan national rolled out Urban Space constrained developments. Reduce environmental impact & aids planning consent process London Power Tunnels, Seven Sisters Road, public information leaflet, 2012
Conclusions Synthetic ester based fluids have been used for many years in distribution and high performance transformers The use of ester-based fluids in power transformers is increasing Esters bring cost benefits through reduced fire protection measures and simplified bunding arrangements A large amount of R&D has been carried out looking at esters for 400kV + Full scale testing has also taken place Synthetic ester fluids are now being specified for transformers at the 400kV level
References
Power References Vattenfall, Stalon Sweden, Siemens Austria, 238kV / 135MVA Vattenfall, Lasele Sweden, Siemens Austria, 235kV / 100MVA Vattenfall, Umlusen Sweden, Ganz Ungarn - 151kV / 110MVA E-ON, Holland, Smit, 66kV / 23MVA Utility in Olszten Poland, ABB Lodz, 50kV / 25MVA Birka, Swede, ETRA 33 50kV / 21MVA Fortum Distribution AB, Sweden, ETRA 33, 44kV / 21MVA Vattenfall, Ringhals Sweden, ABB Vaasa, Finland, 50kV / 145 / 6,8MVA
Thank you Manjunath Ramakrishna Discussions Products of M&I Materials Ltd.