Copyright 2011 M&I Materials Ltd. Products of M&I Materials Ltd.
Retrofilling with Ester Based Transformer Dielectric Fluid to Improve Fire Safety, Moisture Tolerance and
Environmental BehaviourMarch 2011
Copyright 2011 M&I Materials Ltd. Products of M&I Materials Ltd.
Copyright 2011 M&I Materials Ltd. www.midel.com
Transformer Fluids Introduction
Mineral OilSynthetic
EsterSilicone Liquid
Source Crude OilSynthetic Product
Synthetic Product
Typical Fire point
170°C 316°C >350°C
Fully Biodegradable
No Yes No
Moisture Tolerance
Poor Excellent Poor
Copyright 2011 M&I Materials Ltd. www.midel.com
Transformer Fluids Introduction• Mineral oil fires are common
occurrence • Risk to human life • Extremely costly in terms of
damage and clean up (£m’s)• Knock on effects – e.g.
Blackouts • Down-time cost • Transformer replacement • Increased insurance
premiums • Damage to reputation
Copyright 2011 M&I Materials Ltd. www.midel.com
Typical Flash and Fire PointFlash Point• Defined as temperature at which vapour ignites, but will not sustain burning
when flame is removed
Fire Point• Defined as temperature at which vapour ignites and sustains burning for at
least 5 seconds when source of ignition is removed
Fluid Flash Point (ISO 2719 - Pensky)
Fire Point (ISO 2592 - COC)
MIDEL 7131 260°C 316°C
Mineral Oil 150°C 170°C
Silicone Liquid 260°C >350°C
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Ignition Resistance
Mineral Oil 3 mins
MIDEL 7131 3 mins
Mineral Oil 4 mins
MIDEL 7131 70 mins
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Insurance Advice
• FM Global® loss prevention datasheet 5-4 transformers
• Spacing between transformers
TransformerMin. Spacing
2,000litres 40,000litres
Mineral Oil 7.6m 15.2m
Approved Less Flammable Fluid
1.5m7.6m
Approved Transformer or Equivalent
0.9m 0.9m
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Comparative Biodegradation Rates
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30
Time (Days)
Bio
de
gra
da
tio
n (
%)
MIDEL 7131
Mineral Oil
Silicone Liquid
Copyright 2011 M&I Materials Ltd. www.midel.com
Containment Requirements
• FM Global® guidance
• Much larger amount of fluid permitted before containment is required
Fluid ClassificationVolume Requiring Containment
(litres)
Mineral Oil >1,900
Approved less flammable fluid >5,000
Approved biodegradable fluid >10,000
Copyright 2011 M&I Materials Ltd. www.midel.com
Moisture Saturation Comparison
FluidSaturation Limit
@ 20°C
MIDEL 7131 2700ppm
Mineral Oil 55ppm
Silicone Liquid 220ppm
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Breakdown Voltage vs. Relative Moisture
0
10
20
30
40
50
60
70
80
90
100
110
0 10 20 30 40 50 60 70 80 90 100
Relative Moisture Content (%)
Bre
akd
ow
n V
olt
age
(kV
) MIDEL 7131
Mineral Oil
Silicone Liquid
IEC Breakdown Voltage Limit
Ref: Prof. S. Tenbohlen Stuttgart
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Moisture Uptake Comparison 90% Humidity
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30
Time (Days)
Rel
ativ
e M
ois
ture
Co
nte
nt
MIDEL 7131
Mineral Oil
Critical Moisture Level
Ref: I. Fofana University of Quebec
Copyright 2011 M&I Materials Ltd. www.midel.com
Condensation in Wet Transformers
Temp. 90°C
Saturation Limit
Transformer Running High LoadMIDEL 7131
Moisture 700ppm
<12% saturated
OK
Mineral Oil
Moisture 65ppm
<15% saturated
OK
Temp. 20°C
Saturation Limit
Transformer Shutdown Mineral Oil
Moisture 65ppm
118% saturated
CONDENSATION
MIDEL 7131
Moisture 700ppm
26% saturated
OK
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Mineral Oil Low Temperature Breakdown
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60 70 80 90 100
Temperature (°C)
Bre
akd
ow
n V
olt
age
(kV
)
10ppm
20ppm
40ppm
Ref: H. Borsi Schering Institute
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Synthetic Ester Low Temperature Breakdown
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50 60 70 80 90 100
Temperature (°C)
Bre
akd
ow
n V
olt
age
(kV
)
20ppm
80ppm
200ppm
500ppm
Ref: H. Borsi Schering Institute
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Corrosive Sulphur• MIDEL 7131 does not contain corrosive sulphur
• Mineral oil source of corrosive sulphur compounds
• Causes copper sulphide deposit on paper and copper windings
• Identified as cause of failure of power transformers
• MIDEL 7131 independently tested to ASTM D 1275 B and IEC 62535
• MIDEL 7131 was found to be non-corrosive in both tests
• MIDEL 7131 tested for DBDS, none found
Copyright 2011 M&I Materials Ltd. www.midel.com
Why Retrofill with MIDEL 7131?• Retrofilling is the replacement of the fluid in the transformer
• Increased Fire Safety
• Significantly improves fluid fire point
• High Performance
• Provides moisture tolerance
• Reduces maintenance
• MIDEL 7131 is very oxidation stable, suitable for breathing transformers
• Greater environmental protection
• Accelerates biodegradation rate
Copyright 2011 M&I Materials Ltd. www.midel.com
Retrofilling Case Study – SEWA 2009• Sharjah Water and Electricity
Authority chose MIDEL 7131 for a retrofilling pilot study
• Sharjah Gold Souk (tourist attraction), UAE
• Mineral oil transformer, 1500kva, 11/0.433kV, 2001
• Densely populated area, running at high temperatures – deemed high risk
• Initial test results excellent & analysis to take place over next few years to assess progress
Copyright 2011 M&I Materials Ltd. www.midel.com
Retrofilling Experience - Vattenfall• Large utility with operations throughout Europe• In Berlin: Started retrofilling 1992 in high risk areas• 500 transformers retrofilled with ester between 1992 -1994• From 1994, on average 10 transformers per year retrofilled• All new distribution transformers in risk areas are ester filled• 1,900 transformers in total with ester
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Vattenfall Results – Pilot Phase
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Vattenfall Results – Long Term
Copyright 2011 M&I Materials Ltd. www.midel.com
Retrofilling Field Trial - Devonport• Shipyard in South of England
• Ex Ministry of Defence
• 800 kVA, 30 year old transformer
• Joint retrofilling trial in 2004
• Wet transformer, out of service
Copyright 2011 M&I Materials Ltd. www.midel.com
Retrofilling Field Trial - Devonport• Transformer was out of service due to low insulation resistance
• Retrofilled with MIDEL 7131
• Insulation resistance increased and transformer back in service
Before
(Mineral oil)
After
(MIDEL 7131)
Breakdown Voltage 22kV >65kV
Moisture Content 51.4ppm 400ppm
Core Insulation Reading
<20M 80M
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Devonport Breakdown Voltage Results
0
10
20
30
40
50
60
70
80
90
100
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Time (Years)
Bre
akd
ow
n V
olt
age
(kV
)
IEC 61203 Minimum Limit for Synthetic Esters
Copyright 2011 M&I Materials Ltd. Products of M&I Materials Ltd.
Thank-you for listeningHussam Al-Amin – Business Development Manager Tel: +44 161 864 5495 Email: [email protected]
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