Benefits of Ester Fluid
Technology
Kevin Rapp
A LT E R N AT I V E L I Q U I D S T I M E L I N E
Fluid development
2nd
generation
Synthetic esters
3rd generation
Natural esters
1st generation
Silicone oil & LFH
Basic MO
Transformer
invention
Pioneers
Developed by transformer
manufacturers – not chemist!
1890’s
1970’s
1980’s
1990’s
FR3™ TIMELINE
Cargill production
of FR3 fluid
Utility field
trials begin
Brazilian fluid
production
Full scale
accelerated life
tests completed
ASTM, IEEE
& IEC natural
ester standard
Number of units
per year
Global Patent
3rd generation
Natural esters
Transformers
available
commercially
Other
production sites
Environmental
technology
verification
Formulation
selected
1994
1996
1998
2000
2002
2004
2006
300,000
250,000
200,000
150,000
100,000
2008
2010
2012
2014
2016
2018
2020
2,500,000
2,000,000
+2,5
1,500,000
Million
1,000,000
accumulated units
New units per year
500,000
Estimated FR3 fluid filled units globally
2008
2010
2012
2014
2016
2018
2020
C O M P A R I S O N O F I N S U L AT I N G L I Q U I D S
Fluids overview
Mineral Oil
Natural Ester
(FR3 fluid)
Synthetic Ester
Silicone Oil
Base Fluid
Petroleum Oil
Vegetable Oil
Hydrocarbons
Polydimethylsiloxanes
Dielectric Capacity
Reference
Equivalent
(better for PD’s)
Equivalent
(PD is a weak spot)
Lower
(usage limited to 44kV)
Diagnostic Capability
Yes
Yes
Yes
Less
Fire point
160°C
360°C
315°C
340°C
Biodegradability
Low
High
Moderate
Very Low
Biobased
No
Yes
No
No
Oxidation
Good
Good
Very good
Very good
Aging
Average
Best
Better
Average
Cost
$
$$
$$$
$$$$
(non-free breathing)
6
C O M P A R I S O N O F I N S U L AT I N G L I Q U I D S
Mineral Oil Molecules
Natural Ester Molecule
Synthetic Ester Reaction
7
Structures reproduced from IEEE PC57.166 interim working draft October 2021
C O M P A R I S O N O F I N S U L AT I N G L I Q U I D S
Natural Ester Reaction
Alcohol
+
Acid
Ester
+
Water
8
C O M P A R I S O N O F I N S U L AT I N G L I Q U I D S
Natural ester and fatty acids structures
R1
Glycerol
backbone
Triacyl
groups
R2
R3
R1 =
Saturated fatty acid
R2 =
Or R2 =
Unsaturated
Fatty acids
R3 =
9
C O M P A R I S O N O F I N S U L AT I N G L I Q U I D S
Properties correlate with fatty acid content
% Fatty Acid Distribution versus Viscosity
palmitic
stearic
oleic
linoleic
linolenic
Viscosity
Pour Point
Gassing
Tendency
Natural Ester
C16:0
C18:0
C18:1
C18:2
C18:3
mm /sec
2
⁰C
µl/min
Soybean
Rapeseed
Canola
HO Sunflower
Palm
10.4
4.5
4.8
3.2
45.0
3.1
3.0
2.8
2.5
4.0
24.1
59.0
61.5
84.3
40.0
57.0
20.0
18.8
6.9
10.0
5.0
8.3
7.8
0.9
0.2
33
37
40
42
45
-15
-15
-9
-12
23
-78
-65
-66
-65
-
Relative Oxidation
Stability
1
1
10
100
200
10
ABOUT FR3
How was FR3 developed?
Developed by a transformer manufacturer for its
transformers, surpassing the challenges from mineral
oil and synthetic esters.
▪ Over 5 years of lab research → best balance of
properties
▪ Gaining internal confidence was their first
challenge. Lockie test was a “due diligence” test.
▪ No risk to corporate image and reputation of
OEM.
▪ Extensive testing and validation was required.
C O M P A R I S O N O F I N S U L AT I N G L I Q U I D S
Comparison of Aged Paper
Results of a Sealed Vessel Study
Envirotemp FR3
Mineral Oil
Sealed Tube Test - ML 152-2000
Upgraded Paper 500 hr @ 170°C
Envirotemp FR3
Mineral Oil
Sealed Tube Test - ML 152-2000
Upgraded Paper 1000 hr @ 170°C
Envirotemp FR3
Mineral Oil
Sealed Tube Test - ML 152-2000
Upgraded Paper 2000 hr @ 170°C
Envirotemp FR3
Mineral Oil
Sealed Tube Test - ML 152-2000
Upgraded Paper 4000 hr @ 170°C
Ester liquids reduce the aging rate of insulation paper via superior capability
of managing water
12
C O M P A R I S O N O F I N S U L AT I N G L I Q U I D S
Moisture Saturation of Mineral Oil, FR3 fluid and Envirotemp 360
8000
MO
FR3 fluid
7000
Moisture Saturation Content [ppm]
Envirotemp 360
6000
5000
4000
3000
2000
1000
0
-20
0
20
40
60
Temperature [°C]
80
100
120
140
13
DIELECTRIC STRENGTH
Dielectric strength of ester liquids acceptable at high water content
80
D1816 Dielectric Breakdown Strength (kV)
D1816 Dielectric Breakdown Strength (kV)
80
70
60
50
40
30
20
Envirotemp FR3 fluid
Envirotemp FR3 fluid - 2006 production
10
mineral oil
0
0
100
200
300
400
Water Content (mg/kg)
500
600
700
70
NE Fluid
Mineral Oil
60
50
40
30
20
10
0
0
20
40
60
80
100
o
Water Content (% of 20 C saturation)
14
C O M P A R I S O N O F I N S U L AT I N G L I Q U I D S
Water migrates to the fluid and hydrolysis
converts the ester + water into fatty acids
7
5
natural ester fluid - water content
800
600
3
400
2
200
1
Water in Fluid (mg/kg)
% Water in Paper
600
5
400
4
3
200
2
1
0
0
0
500
1000
1500
Aging Time at 85oC (hrs)
2000
0
0
500
1000
1500
Time at 85oC (hr)
2000
2500
0
3000
Water in Paper (%wt)
Acid Number (mg KOH/g)
Water in NE Fluid
Water in Min. Oil
Paper in Min. Oil
Dissolved Water in Fluid (ppm)
Paper in NE Fluid
4
6
natural ester fluid - acid number
water in paper
C O M PA R I S O N O F A G I N G V E S S E L
Aging Vessel after 2000 hrs at 170⁰C
Natural Ester Fluid
Mineral Oil
Fatty acids produced by hydrolysis of FR3 fluid stay in solution
versus plating out on heat generation surfaces as in mineral oil
I N S U L AT I O N I N T E R A C T I O N S
Fluid-Cellulose Interaction
Cellulose Protected by Long-Chain Ester Linkage
Esterified Linkage
6
OH
H2C
5
H
4
Primary 1o Hydroxyl
1
3
H
O
H
4
H
HO
H
H
H
O
OH
O
H
OH
H
H
O
2
OH
H2C
2o Hydroxyl
n
OH
Primary 1o Hydroxyl
CELLULOSE - OH + R - C - OH
O
=
=
O
R - C - O - CELLULOSE
17
I N S U L AT I O N I N T E R A C T I O N S
Superior moisture tolerance
Ester liquids have an exceptional ability to remove
water that is either generated by the aging of
transformer insulation paper or that is present due to
the intrusion of moisture into a sealed transformer.
5x-8x
5x-8x
1.5x-3x
Lower paper
degradation rate
Longer paper
lifespan
Longer asset
lifespan
PA P E R - E S T E R F L U I D I N T E R A C T I O N
Ester Fluids Provide Life Extension
• IEEE C57.154 (IEC 60076-14)
High temperature transformer
standard
•
Current standard 110oC hot spot with 65
AWR limits transformer capability
•
Natural ester fluid-based insulation
systems can be run 20oC warmer without
degrading life
•
Using current standards transformers
can be upgraded to provide loading
capability (Thermal Rise Ratings)
•
Design new transformers with higher
temperature ratings, achieve smaller
footprint with same or more load
capability
19
RELIABILITY & RESILIENCE
Loading capacity
vs. High temperatures
º
+20 C
Operational temperature
+20%
Added capacity
Same lifespan
RELIABILITY & RESILIENCE
Reliability & Resilience
vs. Transformer size 250 / 340 kVA (dual rated)
250 / 340 kVA
250 kVA
•
•
•
•
FR3™ fluid transformers
Mineral oil transformers
Extended loading capacity
Higher permissible hot spots
Higher paper thermal classes
Lower initial cost than the larger
mineral oil unit
F I R E C O M P A R I S O N O F I N S U L AT I N G L I Q U I D S
Fire Safety
Transformer liquids classifieds as “Fire Resistant” (K Class) must
have Fire Point minimal of 300°C
400
Flash Point
Fire Point
343
330
350
Temperature (°C)
360
308
300
300
270
250
200
155
150
165
Mineral
Oil
Synthetic
Ester
Silicone
Natural
Ester
22
ARE TRANSFORMER FIRES UNCOMMON?
Transformer
Installation Risks
Overall failure rate (from Cigre TB 642) indicates
failure rates:
▪ Substation transformers = 0.53% / year
▪ Generator step-up transformers = 0.95% / year
▪ External effects on ~25% of failures
Each 400 - 800 transformers = At least one fire / year!
FM Global (insures 7% of the world’s generating
capacity) reported ~1 Billion USD losses in 10 years
FIRE SAFETY TESTING
Fire Safety – How to evaluate?
Flammability Tests - FM Global (Factory Mutual/1994)
• Target
– Determine if the ignition of internal arcs in transformers with fire resistant
fluids results in fires
• Summary
– A low energy failure heats up the transformer insulating liquid.
– The failure results in a rupture of the pressure relief valve, releasing oil to the
ambient
– The fluid deposits around the transformer on the floor
– The arc is kept and causes a high energy fault and, probably, an explosion
breaking the tank, resulting in the discharge of the hot fluid on the floor
24
FIRE SAFETY TESTING
Fire Safety – Flammability Test – Mineral Oil
• Oil Temperature
– Tank 128°C
– Channel 133°C
• Current 3784A
• Arc duration 7.77s
• Spray of hot oil and fire over
the oil in the channel
• No external ignition source
• Self ignition 350°C
25
FIRE SAFETY TESTING
Fire Safety – Flammability Test – K-Class Fluid
• Oil Temperature
– Tank 140°C
– Channel 133°C
• Current 3831A
• Arc duration 7.56s
• Disc open, no ignition
• No external fire ignition
source
26
FIRE SAFETY TESTING
•
Oil Temperature
– Tank 133~188°C
– Channel 135°C
•
Current 2939A
•
Arc duration 10s
•
Disc open, ignition of the
gases at the external
ignition source
•
External flame
extinguished after 3.5s
27
FIRE SAFETY TESTING
Fire Safety – Flammability Test – Conclusions
• The internal arc in a mineral oil insulated transformer can cause a fire
(even without external ignition source)
• The internal arc in a transformer insulated with fire resistant K-Class
fluid has no ignition
• Discharged gases from the transformer with fire resistant K-Class
fluids, in spray form, can burn if there is an external ignition source
(but no liquid fire)
• Since the quantity of energy from the initial fire is not enough to
maintain the fluid temperature, the fire is self extinguished
28
FIRE SAFETY TESTING
Fire Safety – Flammability Test – Open Tank Test
- Designed by FM Global 2002
• Goal
– Determine the possibility of reducing the distances and containment from
FM standards, without any additional protection or fire extinguishing
system.
• Summary
– External and internal failures of high energy and / or induced currents from
the system that can heat up metal pieces to glowing red (stray flux).
• Procedure
– Quickly insert a metal plate heated red hot (750°C) in a tank with fluid heated
at 130°C. Measure the temperatures and verify the occurrence of fire.
29
FIRE SAFETY TESTING
Fire Safety – Flammability Test – Open Tank Test
- Mineral Oil
30
FIRE SAFETY TESTING
Fire Safety – Flammability Test – Open Tank Test
- FR3 Natural Ester (NE) Fluid
31
FIRE SAFETY TESTING
Fire Safety – Flammability Test – Open Tank Test
- FR3 NE Fluid 95.5% + 4.5% Mineral Oil
32
Natural & Synthetic
Mineral
oil transformer
Ester
K-Class
transformers
Building
Reduced
clearances
Fire
wall
Automatic fire
suppression system
Mineral oil containment and
suppression rocks
FR3 fluid simplified
border
™
33
FR3fluid.com
B I O D E G R A D AT I O N
Oxidation of natural ester liquid important for biodegradability
Biodegradation Rate of Dielectric Fluids
Aerobic Aquatic Biodegradation
Envirotemp FR3 fluid
conventional transformer oil
sodium citrate reference material
(EPA "ultimate biodegradability")
60
40
20
test performed per EPA OPPTS 835.3100 by
Thomas A. Edison Technical Center
Franksville, WI 53126 USA
Wisconsin DNR Laboratory #252021770
report issued April 23, 1999
0
0
5
10
15
20
25
Elapsed Time (days)
30
35
40
45
100
OPPTS 835.3100
10% + 10 days
80
Biodegradation Rate (%)
CO2 Evolution (% of theoretical max)
100
75
50
25
0
silicone
mineral oil synthetic
ester
natural
ester
36
OECD TOXICITY TESTING
Acute Aquatic and Oral Toxicity
Acute aquatic toxicity of Envirotemp FR3 fluid
Test
Method
Acute Aquatic Toxicity
Lethality Using Rainbow Trout
Acute Aquatic Toxicity
a
b
Dose
(mg/L)
Mortality
(# of fish)
a
LC50
(mg/L)
NOAEC
(mg/L)
OECD 203
Environment Canada
1,000
1,000
0
0
> 1,000
> 1,000
> 1,000
> 1,000
ASTM D608, OECD 203
10,000
0
> 10,000
> 10,000
b
LC50 = lethal concentration killing 50% of fish
NOAEC = no observable adverse effect concentration
Acute oral toxicity of Envirotemp FR3 fluid
Method
Test
Animals
Dose
(mg/kg)
% Mortality
Total
14 Day Average Body Weight (g)
Initial
7 Day
Final
OECD 420
Sighting
1F
2,000
0
226.0
251.2
259.9
Main
5F
5M
2,000
2,000
0
0
221.5
285.3
265.0
352.0
280.6
378.8
37
REDUCED CLEANUP COSTS
Environmental Advantages
FR3  and other natural ester liquids are developed from renewable feedstocks
Non-toxic, non-hazardous, readily biodegradable
▪ OECD oral and aquatic toxicity tests – zero mortality
▪ >98% vegetable oil
▪ Carbon Neutral
FR3 can help minimize potential damage from spills
▪ Readily biodegradable
▪ Less likely to permeate soil and reach water table
▪ Cleanup using bioremediation can be an advantage
38
DIELECTRIC PERFORMANCE
Electrical performance of FR3 natural ester fluid is equal or
better than mineral oil
• More than seven series of tests have
confirmed performance:
• Basic dielectric tests AC. LI, SS, CW
• Testing gaps up to 65 mm and
evaluation of Kappeler Curve
• Evaluation of Interfacial Creep
• BDV at low temperature conditions
• Long gap tests up to 150mm
(1800kV) with inhomogeneous field
• Tap Changer testing
• Partial Discharges Inception Voltage
39
DIELECTRIC PERFORMANCE
Permittivity affects field distribution
Calculation
with MO
Calculation
with NE
Uniform in the center
Higher concentration in
the corners
40
DIELECTRIC PERFORMANCE
Dielectrics of FR3 fluid and Mineral Oil were equivalent
41
DIELECTRIC PERFORMANCE
Long gap tests confirmed equivalent breakdowns
LI 1.2µs x 50µs – negative polarity
2000
600
Negative Lightning Impulse (kV)
500
AC 60 Hz (kV)
400
300
200
100
NE Fluid Withstand (1%)
Min. Oil Withstand (1%)
NE Fluid Breakdown (avg)
Min. Oil Breakdown (avg)
60
50
600
500
400
NE Fluid Withstand (1%)
Min. Oil Withstand (1%)
NE Fluid Breakdown (avg)
Min. Oil Breakdown (avg)
300
200
10
20
30
50
100
200
Fluid Gap (mm)
10
20
30
40
50
100
200
Fluid Gap (mm)
2000
Positive Switching Impulse (kV)
1000
900
800
700
Stress between Tap Changer contacts
FR3 fluid results
for MR OLTC were
better than MO
1000
900
800
700
600
500
400
NE Fluid Withstand (1%)
Min. Oil Withstand (1%)
NE Fluid Breakdown (avg)
Min. Oil Breakdown (avg)
300
200
50
70
100
Fluid Gap (mm)
150
200
42
DIELECTRIC PERFORMANCE
Partial Discharge Inception of NE higher than SE or MO
> Partial Discharge
Inception Voltage
(PDIV) for different
temperatures and
water contents
(needle – disc) for
Natural Ester,
Synthetic Ester, and
Mineral Oil.
43
Thank You
Email: Kevin_Rapp@Cargill.com