the development of 400kv class synthetic ester … · national grid uk 400kv –london project...

Copyright 2017 M&I Materials Ltd. Products of M&I Materials Ltd.

The Development of 400kV Class

Synthetic Ester Transformers

Copyright 2017 M&I Materials Ltd. www.midel.com

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 EstersSYNTHETIC 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

London Power Tunnels, Seven Sisters Road, public information leaflet, 2012

• NG see this system as a future strategy

• Plan national rolled out

− Urban

− Space constrained developments.

• Reduce environmental impact & aids

planning consent process

• 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


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

Copyright 2017 M&I Materials Ltd. Products of M&I Materials Ltd.

Thank you

Manjunath Ramakrishna

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