Oil
Refining
Key Properties - Comparison to Mineral Oil Natural & Synthetic Esters
Synthetic Polyol Esters have been used as a
PCB substitute in specialty transformer
applications since the early Eighties in the
USA. They are formed by processing fatty
acids and alcohols.
Natural Esters are produced from seeds. Vegetable Oils are Natural Esters Vegetable Oil vs. Mineral Oil Renewable Resource Much Higher Flash & Fire
Points Environmentally
Friendlier Several Performance
Improvements
Advantages Inferior oxidative stability Poorer low temperature
properties Higher Viscosity Higher Cost to Produce
Limitations Vegetable Oil vs. Mineral Oil
Naphthenic Mineral Oil
Vegetable Oil
O
O
O
O
O
O
Seed Oil Refining
RBD Vegetable Oil
CRACK, DEHUL L, FLAKE
HEXA NE EX TRACTIO N
PRES S (cano la, sunflower)
Soybea n
Meal
Sun flower &
Canola Meal
HEXA NE DIS TILLA TION
CRUDE OIL
.1-3% phosphatides
1% fatty acids
1 ppm chlorophyl
DEGUM (H
2
O, H
3
PO
4
)
lecithin
ALK ALI REFINE (NaOH)
Soap stock
BLE ACH (acidic cla y)
DEODORIZE (250°C, vacu um, steam)
Volatile impurities:
odor (aldehydes & ketones
fatty acids
HYDROGENATE / WINTERIZE (chill)
Waxes & saturated fats Beans to Crude Vegetable Oil
Soybeans Cracked Soybeans Crude Soybean Oil Seed Oil Refining
RBD Vegetable Oil
CRACK, DEHUL L, FLAKE
HEXA NE EX TRACTIO N
PRES S (cano la, sunflower)
Soybea n
Meal
Sun flower &
Canola Meal
HEXA NE DIS TILLA TION
CRUDE OIL
.1-3% phosphatides
1% fatty acids
1 ppm chlorophyl
DEGUM (H
2
O, H
3
PO
4
)
lecithin
ALK ALI REFINE (NaOH)
Soap stock
BLE ACH (acidic cla y)
DEODORIZE (250°C, vacu um, steam)
Volatile impurities:
odor (aldehydes & ketones
fatty acids
HYDROGENATE / WINTERIZE (chill)
Waxes & saturated fats RBD Oil
(Refined, Bleached, Deodorized)
RBD SBO Vegetable Oil Refining
Start with beans or seeds.
End with purified oils.
Purified oils are the starting point for
transformer oils Ester Transformer Fluids
Key Properties & Standards
T.V. Oommen, Consultant
ABB, Inc. Natural Esters for Transformers
RBD edible vegetable oils used for base.
Further processing e.g. Removal of polar
contaminates. Addition of performance enhancing
additives
Dielectric fluids from natural esters, remain highly
biodegradable, with high flash and fire points, and
can test non-toxic to sensitive species . Use of Natural Esters in Electrical
Equipment
New and Retrofill Application in the Field: Distribution Transformers: Single and Three Phase
Pole and Pad-mounted, Small Power.
Medium power Transformers
Mobile Substation Transformers
Voltage Regulators
Switchgear
Transformer- Rectifier Sets Transformer Oils Physical Properties
STD. MIN OIL
HI FIRE PT
BIOBASED
D 3487
D 5222
D 6871
Color, max.
0.5
2.5
1.0
Visual Examination
B&C
B&C
B&C
Flash Point, °C, min.
145
275
275
Fire Point, °C, min.
--
300
300
Pour point, °C, max.
-40
-21
-10
Spec. Grav., 15°C, max.
0.91
0.91
0.96
Viscosity, max. cSt: 100°C
3.0
14
15
40°C
12
130
50
0°C
76
2500
500
Interfacial Tension,
25°C, dynes/cm, min.
PROPERTY
--
40
40 Relative Flash and Fire Points
150
200
250
300
350
400
Degr
ee Cent
igr
ade (
°C)
Mineral Oil
HMWH
Silicone Oil
Natural
Ester
Flash Point
Fire Point Transformer Oils Electrical Properties
STD. MIN OIL
HI FIRE PT
BIOBASED
D 3487
D 5222
D 6871
Dielectric breakdown, KV min.:
Disk electrodes, min.
30
30
30
VDE elect., 0.04" gap, min.
20
--
20
VDE elect., 0.08" gap, min.
35
--
35
Impulse,1" gap, 25°C, min.
145
--
130
Gas. tend., µL/min, max.
30
30
0
Diss. Fact. % max, 25° C
0.05
0.05
0.2
100°C
0.30
0.30
4.0
PROPERTY Transformer Oil Chemical Properties
STD. MIN OIL
HI FIRE PT
BIOBASED
D 3487
D 5222
D 6871
Oxidative Stability:
72 hrs - % sludge, max.
0.15 / 0.1
0.15
not estab.
Acid number, max.
0.5 / 0.3
0.30
not estab.
164 hrs - % sludge, max.
0.3 / 0.2
0.3
not estab.
Acid number, max.
0.6 / 0.4
0.60
not estab.
RBOT minutes, min.
- / 195
195
not estab.
Corrosive Sulfur
pass
pass
pass
Water, ppm, max.
35
35
200
Acid number
0.03
0.03
0.06
PCB Content
not detectable
not detectable
not detectable
PROPERTY Test & Verification Data Available
Physical, chemical and electrical characteristics
Heat transfer properties
Water solubility data
Decomposition under thermal and electrical stress
Functional life test data
Long term aging data
Field performance in commercial units
Environmental performance data
Retrofilling units having other fluid types Test & Verification Data Available
References:
IEEE, CIGRE, ACS, CIRED Publications
and Proceedings
ASTM D6871-03 Standard
Manufacturers/Suppliers Literature
Published Testing Laboratories Reports
(e.g. Doble Engineering, EPRI, US EPA ETV, UL, FM) Ester Transformer Fluids
Performance & Applications
C. Patrick McShane
Cooper Power Systems Performance Improvements vs. MO
Insulating Paper Aging Rate Reduced
Essentially no Sludge Precipitate
Reduction of Paper Moisture Levels
Much Lower Gassing Tendency Value
Reduced Coking on Bare Copper
Potential Self Sealing weeping leaks Insulation Paper Aging Rate
Reduced
Accelerated Paper Life Testing using the
Sealed Tube Method, comparing aging in
natural ester fluid versus mineral oil to
reach a defined life end point: Thermal Upgraded Kraft: Up to 8 times
longer. Non-Upgraded Kraft: > 10 times longer. Comparison of Tensile Strength vs. Time
Sealed Bomb Accelerated Aging
Thermally Upgraded Paper at 170
o
C
Aging Time (hours)
0
1000
2000
3000
4000
T
ensi
l
e S
t
r
e
n
g
t
h

(
l
b/
i
n
2
)
0
5000
10000
15000
20000
R
e
t
a
i
n
e
d

T
e
ns
i
l
e

S
t
r
e
n
g
t
h
(
%
o
f
u
nag
ed)
100
75
50
25
0
mineral oil
EFR3
(error bars = 1
)
natural ester Visual Comparison vs. Aging Time
Sealed Tube Test - ML 152-2000
Upgraded Paper 2000 hr @ 170°C
Sealed Tube Test - ML 152-2000
Upgraded Paper 4000 hr @ 170°C
Sealed Tube Test - ML 152-2000
Upgraded Paper 500 hr @ 170°C
Sealed Tube Test - ML 152-2000
Upgraded Paper 1000 hr @ 170°C
Natural Ester
Mineral Oil
Natural Ester
Mineral Oil
Natural Ester
Mineral Oil
Natural Ester
Mineral Oil Essentially no Sludge Precipitates
Mineral oils, when oxidized tend to form
and precipitate sludge, potentially reducing
dielectric and thermal performance.
Natural ester oils, when oxidized, tend to
polymerize but not form sludge precipitates. Hot Oil, Open Beaker Aging Test
Edible Oil Base HMWH Base
Conventional MO Reduction in Paper Moisture
A ging T im e at 170
o
C (hours)
0
1000
2 000
3000
Water Co
n
t
e
n
t (w
t %)
0
1
2
3
4
5
6
7
m in e ra l o il
n a tu ra l e ste r
re tro fill Lower Gassing Rate
ASTM D2300 Gassing Tendency: Mineral Oil typically around -5
µL/min. Natural Esters between -50 to - 80
µL/min.
Doble Partial Discharge -TCG: Mineral Oil -------------
1,500 ppm Natural Esters ----------
1,100 to 1,300 ppm Reduced Coking Tendency
Immersed Hot Copper Surface Test: With air head space, natural ester produced
1/40 coking relative to mineral oil. With nitrogen head space, natural ester
produced non-detectable coking. Relative Coking on Hot Copper
Mineral Oil Produced Up to 40 Times by Weight Aerobic Aquatic Biodegradation
Test Method: EPA OPPTS 835.3100
Elapsed Time (days)
0
5
10
15
20
25
30
35
40
45
CO
2

E
v
ol
ut
i
o
n (
%
of
t
heor
e
t
i
c
a
l
m
a
x
)
0
20
40
60
80
100
B
i
ode
gr
adat
i
on (
%
)
0
25
50
75
100
"100% biodegradable" above 60% of theoretical maximum CO
2
evolution
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
sodium citrate reference material
(EPA "ultimate biodegradability")
Envirotemp FR3 fluid

conventional transformer oil
Edible Oil Based
Mineral Oil
Ultimate Biodegradability Control Sample Initial Commercial Uses of
Natural Esters
Distribution and small power units:
New Units 1999
Retrofill 1999
Medium Power Transformers:
Retrofill 2001
New Units 2003
TR Sets
Retrofill 1999:
Switchgear
New Units 2002: Field Performance
Average Values of Nine 3 Phase Pad-
Mounted Transformers 77th Month Samples
New
Ave.
Std. Dev.
Moisture ppm
15
33
14
Dielectric Strength
62
70
10
Fire Point
359
359
2
Viscosity
32.7
32.4
0.3
Dissipation