Natural Ester Fluid Diagnostics Weidmann 7 th Annual Technical Conference September 17, 2008 BY: C. Patrick McShane and John Luksich
Market Demand Accelerating More than 130,000 transformers in service More than 120 power transformers in service 200 MVA generator step-up retrofill 242 kv reactor new Recent US Utility announced conversions: Alliant Energy: 1P and 3P distribution, Iowa GSU substation retrofills Energy East: 1P and 3P distribution Xcel Energy: 1P distribution ComEd: 1P pole distribution & networks American Electric Power: network SMUD: distribution and network
Natural Ester Market Drivers More desirable environmental profile Improved insulation system life Increasing demand for sustainable supply Smaller carbon footprint Potential for reduced maintenance, dry-outs Greatly improves fire safety Eliminates key eco/health issues Reduces or eliminates m.o. required safeguards
Natural Ester Environmentally Preferred Rapid and complete biodegradation Equal to EPA ultimately biodegradable class. >80% in 10 day. >99% 45 days. Does not contain hazardous additives Passes OCED Acute Aquatic Toxicity No mortality (trout fry) Renewable Source contributing to Sustainability
Insulation System Life Extension Envirotemp FR3 Mineral Oil Envirotemp FR3 Mineral Oil Envirotemp FR3 Mineral Oil Sealed Tube Test - ML 152-2000 Sealed Tube Test - ML 152-2000 Sealed Tube Test - ML 152-2000 Upgraded Paper 500 hr @ 170 C Upgraded Paper 2000 hr @ 170 C Upgraded Paper 4000 hr @ 170 C 500 hours 2000 hours 4000 hours
Fire Safety FM Global Separation Requirements can be less than 1/10 distance required for mineral oil. Table 2a. Separation Distance Between Outdoor Liquid Insulated Transformers and Buildings Horizontal Distance 1 Two Hour Fire Noncombustible Combustible Vertical Approved Transformer Liquid Volume Resistant Construction Construction Construction ft Distance ft Liquid or Equivalent gal (m 3 ) ft (m) ft (m) (m) (m) Yes N/A 3 (0.9) 5 (1.5) Less Flammable 10,000 (38) 5 (1.5) 25 (7.6) 25 (7.6) (Approved Fluid) No > 10,000 (38) 15 (4.6) 50 (15.2) 50 (15.2) Mineral Oil (or unapproved fluid) N/A 1) All transformer components must be accessible for inspection and maintenance. < 500 (1.9) 5 (1.5) 15 (4.6) 25 (7.6) 25 (7.6) 500-5,000 (1.9-19) 15 (4.6) 25 (7.6) 50 (15.2) 50 (15.2) > 5,000 (19) 25 (7.6) 50 (15.2) 100 (30.5) 100 (30.5) distance from transformer distance from containment edge Table 2b. Outdoor Fluid Insulated Transformers Equipment Separation Distance 1 Liquid Approved Transformer or Equivalent Liquid Volume gal (m 3 ) Distance ft (m) Yes N/A 3 (0.9) Less Flammable 10,000 (38) 5 (1.5) (Approved Fluid) No > 10,000 (38) 25 (4.6) < 500 (1.9) 5 (1.5) Mineral Oil (or N/A 500-5,000 (1.9-19) 25 (4.6) unapproved fluid) > 5,000 (19) 50 (7.6) 1) All transformer components must be accessible for inspection and maintenance. distance from transformer distance from containment edge
Our History research begins full-scale accelerated life tests started formulation selected first distribution transformers retrofilled transformers available commercially available to OEMs first new power transformer first new mobile substation 161 kv, 200 MVA GSU retrofill ASTM natural ester standard first new GSU Major US utilities convert 100% for distribution first new 242 kv reactor 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 first distribution transformers installed utility field trials begin first GSU retrofill 69 kv, 50 MVA US EPA grants Environmential Technology Verification first utility 100% conversion for distribution 230 kv retrofills 100th power transformer installed
How to Diagnose Basic chemistry is different between NE and MO, so. Depending on the property, there can be significant differences in the initial and typical service aged values What s important is to differentiate between performance vs. diagnostic values
Key properties comparisons Similar Dielectric strength* Dielectric impulse* Color (ASTD1500) Visual Examination (ASTM D 1524) Material Compatibility
Key properties comparisons Higher Acid Number Dissipation Factor Dielectric Constant Kinematic Viscosity Flash & Fire Points Relative Density Water Content (ppm) Absolute and Relative Saturation Pour Point
Key properties comparisons Lower Volume Resistivity Interfacial Tension Gassing under Electrical Stress D2300 Corrosive Sulfur
Oxidation Oxidation stability Both mineral oil and natural esters oxidize The fluids oxidize differently Products of mineral oil oxidation form sludge precipitates Products of natural ester oxidation form oligomers (larger molecules) that stay in solution The long term effect on the transformer is the same: less efficient heat transfer
Oxidation 12 Kinematic Viscosity, 100 o C (mm 2 /s) 10 8 6 4 2 Envirotemp FR3 fluid 130 o C 150 o C 170 o C mineral oil 130 o C 150 o C 170 o C 0 0 1 2 3 4 Equivalent "Normal" Lifetimes
Mineral oil 2000 hrs at 170 o C Oxidation
NE fluid 2000 hrs at 170 o C Oxidation
Cold Temperature Cold temperature performance Water saturation Viscosity Cold start
Water Saturation 5000 Water Saturation Point (mg/kg) 4000 3000 2000 1000 Envirotemp FR3 fluid from Doble Engineering mineral oil from IEEE C57.106 0 20 40 60 80 100 120 Temperature ( o C)
80 D1816 Dielectric Breakdown Strength (kv) 70 60 50 40 30 20 10 Envirotemp FR3 fluid mineral oil 0 0 100 200 300 400 500 600 700 Water Content (mg/kg)
80 D1816 Dielectric Breakdown Strength (kv) 70 60 50 40 30 20 10 Envirotemp FR3 fluid mineral oil 0 0 20 40 60 80 100 120 140 160 180 200 Water Content (% of 20 o C saturation)
Water Saturation 1000 Water Content (mg/kg) 100 20 10 IEEE C57.106 max water content in new equipment 69 kv and less mineral oil saturation (IEEE C57.106) Envirotemp FR3 fluid saturation (Doble Eng.) 1-20 -10 0 10 20 30 40 50 Temperature ( o C)
DGA Dissolved Gas Analysis IEEE C57.104 DGA Guide: Key Gases Method with rate of rise OK, but not Ratio Methods IEC Duval method recommended Gas generation & solubility similar to mineral oil Expect higher proportion of ethane compared to mineral oil due to basic fluid chemistry Fine tuning of all limits will come with additional field data and lab investigations
Field Case History Alliant Energy - 50 MVA, 69 kv, built 1957, retrofilled 2001
Dielectric Strength
Dielectric Strength (1mm converted to 2mm)
Absolute Water Content
Relative Water Content
Dissipation Factor
Acid Number
Interfacial Tension
Dissolved Gases
Dissolved CO & CO2
Ethane - The Mischief Maker!
Key Standards ASTM D687-03 Standard Specification for Natural (Vegetable Oil) Ester Used in Electrical Apparatus New IEEE C57-147-2008 IEEE Guide for Acceptance and Maintenance of Natural Esters in Transformers
New IEEE Standard Guide for NE Sec 8 - Maintenance of Natural Esters in Transf. Field Screening Test Limits for service aged fluid Currently only properties listed: Dielectric Strength Fire Point Reconditioning Reclaiming Mixtures of different fluids discussion Most are miscible and compatible Should be avoided Silicone definitely should be avoided, even traces
IEEE Standard Guide for NE Informative Annex B Alternative Oxidation Stability Test Relative Moisture Saturation DGA Information Provisional Guidelines for Trigger Value Limits Key Properties Mixtures Natural Ester with Mineral Oil Relative Cooling
IEEE Standard Guide for NE Table B.5: Provisional Guidelines for Trigger Value Limits Alternative Oxidation Stability Test Dissipation Factor Water Content Flash Point Color Viscosity Increase Inhibitor Content
Eletronorte (Brazil) 242 kv Reactor
Alliant Energy retrofill March 2004, 200 MVA, 161 kv, built 1966, Burlington Iowa
Missoula Electric retrofill December 2005 8 MVA, 230 kv, built 1980, Montana
Keyspan Energy retrofill April 2004, 25 MVA, 19 kv, New York City
Summary Typically the same properties are tested Some properties are significantly different Typically same ASTM test methods apply DGA: Similar faults produce similar gases Exception: Ethane is produced naturally Much more field data required to fine tune interpretation from field samples