Transformer oils - Production, performance and in-service behaviour Johan Grövik Nynas AB TRANSFORM Partner
Nynas Nynas AB founded 1928 Swedish based company Approximately 850 employees Turnover 2 billion EURO 28 Sales channels More than 18 TRO depots Market leader of transformer oils with market share of 25 % Johan Grövik M.Sc Chemical Engineering M.Sc Business Administration Market Manager Electrical Industry e-mail: johan.grovik@nynas.com 06.06.2013 Page 2
Outline Oil demand in the world 2012 versus transformer oil Manufacturing of a transformer oil Failure statistics Selection of insulating oil Maintenance of an insulating oil Summary 06.06.2013 Page 3
Naphthenic crude supply Proven Naphthenic crude reserves for the next 70 years TOTAL= 4442 million Mt BASE OIL= 36 million Mt TRO = 1,2 Million Mt 06.06.2013 Page 4
Basic: -Chemical composition of crude oil Mineral insulating oil is made from crude oil by different refining processes. The constituents are hydrocarbons combined in various structures and sizes. 06.06.2013 Page 5
Trends in the world of refining Technical trend - Development of base oils with high VI Focus on lubrications - Market >36 Mt Key driver for engine oils - To minimize friction - Fuel efficiency TRO oils do not have that technology driver! It require a low VI oil for best performance 06.06.2013 Page 6
What are the requirements of an insulating oil? Provide good cooling Act as an electrical insulator Have an excellent cold start property Material compatibility Last the lifetime of transformer Act as an information carrier 06.06.2013 Page 7
Production of insulation oil 06.06.2013 Page 8
A modern hydrotreatment refinery 06.06.2013 Page 9
Distillation 06.06.2013 Page 10
Hydro-treating processes 06.06.2013 Page 11
Degree of refining Before hydrotreatment Before HT (%) C A (IR) C A 25% 25 C N 30 C C N 30 P 45 Sulphur C P 45 2 IP346 Sulphur 2 10 IP346 10 After hydrotreatment After HT (%) A T B NSC S C A (IR) C A 15 15 10 10 5 5 C N 42 50 50 C N 42 50 50 C P 43 40 45 C Sulphur P 43 40 45 0.03 <0.01 0. IP346 Sulphur 0.032.0 0.01 1 0.01 <1 IP346 2 1 <1 Carbon type distribution determined with IR analysis 06.06.2013 Page 12
Failure statistics 06.06.2013 Page 13
Failure rates of substation transformers Failures / population info. 69-100 kv 100-200 kv 200-300 kv 300-500 kv >700 kv ALL Failures 145 206 136 95 7 589 Transformer - years 15077 46152 42635 29437 219 135491 Failure rate 0,96% 0,46% 0,32 0,32% 3,20% 0,43% Failure rate for step up transformers = 0,46 % Ref; April 2012 Electra 06.06.2013 Page 14
Failure rate conclusion Preliminary results; (data collection still in progress) I. Study based on 150 000 unit years II. Totally 685 failures III. Data from 48 utilities Old study from 1983 (failures occurring 1968-1978) Concluded a failure rate benchmark of 2% Average failure rate = 0,44% Main fault locations (*=GSU transformer) 45-49* % of failures related to windings 26-11* % of failures related to tap changers 9*-17 % of failures related to bushings 7-19* % of failures related to lead exits Ref; April 2012 Electra 06.06.2013 Page 15
Generic failure model; 2 perspective methodology Stress / Strength Strength Stress encountered Damage from incidents Maintenance Failure Transformer quality Analysis => information Maintenance actions Incidents Grid design Operations Protection equipment Time 06.06.2013 Page 16
What is the lifetime of a transformer dependent on? Operating conditions Design / Manufacturing / Material Ambient temperature Design and materials Manufacturing and installation Follow up and maintenance Electricity quality/protection equipment Operations e.g. load Maintenance 06.06.2013 Page 17
Selection of insulating oil 06.06.2013 Page 18
Product Data Sheets 06.06.2013 Page 19
Values and benefits - life cycle perspective Low viscosity oils Good oxidation stability High solvency Lower operating temperatures Low acid values and low sludge production Keep sludge dissolved in oil Better circulation properties Less maintenance over time Slow degradation of oil and paper Longer transformer life 06.06.2013 Page 20
Values and benefits daily operations Low pour point Good flow properties at very low temperatures Transformer can be energized in low temperatures Excellent insulator Can withstand very high electrical stress Excellent compatibility with cellulose Very strong and stable insulation system enable compact design and high voltages Information carrier Record & store fault gases Allow to detect electrical & thermal faults Diagnostic tool to prevent failures and avoid outages 06.06.2013 Page 21
Selection of transformer oil 06.06.2013 Page 22
Maintenance 06.06.2013 Page 23
Antioxidant molecule and specification limits DBPC IEC 60296 Edition 4. 2012 Uninhibited Not detectable Trace Max 0,08 Inhibited Max 0,40 Di-tert-butyl-para-cresol ASTM D 3487 Type I Max 0,08 Type II Max 0,30 06.06.2013 Page 24
1 24 47 70 93 116 139 162 185 208 231 254 277 300 323 346 369 Acidity level and inhibitor content 0,4 Inhibitor (%) 0,3 0,2 0,1 Acidity (mg KOH/g) 0-400 oil immersed power transformers No of samples (increased inhibitor content to the right) 06.06.2013 Page 25
Maintenance strategy Historical data Oil status Analysis DGA status What? How? Diagnostic Who? Why? Information Decisions Maintenance New investment Upgrade etc. Risk level 06.06.2013 Page 26
Summary; Standards for insulating oils IEC 60296 Fluids for electrotechnical applications Unused mineral insulating oils for transformers and switchgear IEC 60296 Before filling into a transformer IEC 60422 Mineral insulating oils in electrical equipment Supervision and maintenance guidance IEC 60422 After filling into a transformer IEC 60156 Insulating liquids Determination of breakdown voltage at power frequency test method Test & Measuring methods 06.06.2013 Page 27
Summary Transformer oil quality Excellent insulator Low Viscosity & VI Superior long term stability Operations Cooling - As low temperature as possible Oxygen - Protection systems Loading - Do not over load Maintenance Antioxidant levels - Monitor and top up 06.06.2013 Page 28
Nynas Group Head Office P.O. Box 10700 SE-121 29 Stockholm Sweden Transformer oils My contact details; - Production, performance and in-service behaviour Johan Grövik johan.grovik@nynas.com Phone: + 46 70 658 68 35 johan.grovik@nynas.com 06.06.2013 Page 29