Electrical Maintenance Workshop
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Electrical Maintenance Workshop
Transformer Maintenance & Testing Thursday, November 6, 2003
Transformer Maintenance & Testing Purpose z
This presentation provides an overview of the major considerations associated with Transformer Maintenance and Testing.
z
Barker Edwards will provide the information for Transformer Maintenance & Testing.
z
Kate Brady will provide the information for Transformer Oil Testing.
2
Transformer Maintenance Things to know! Things you should know about keeping your transformer healthy!
3
Transformer Maintenance Agenda
4
z
Types of transformers
z
Yearly checks
z
Testing of transformers
z
Vacuum pressure device
z
Pressure relief device
z
Sudden pressure relay
z
Gaskets
z
Paints
Transformer Maintenance Types of transformers
z
Dry type transformers
5
Varnished coils
Transformer Maintenance Types of transformers
z
Dry type transformers
6
Cast coils
Transformer Maintenance Type of transformers
z
Oil filled transformers
7
Sealed tank
Transformer Maintenance Type of transformers
z
Oil filled transformers
8
Conservator system
Transformer Maintenance Type of transformers z
Oil filled transformers
Nitrogen blanket
Pressure regulator for Nitrogen Blanket transformer 9
Transformer Maintenance Yearly transformer checks z
Check vacuum pressure gauge for pressure reading.
z
Check oil level.
z
Check temperature maximum and minimum.
z
Check for leaks.
z
Check paint condition.
z
Check transformer top and radiators for foreign material.
z
Check radiator condition.
z
Check fans and cooling systems.
10
Transformer Maintenance Testing of transformers z
Megger test
600 megohms or better to ground is a good bench mark.
11
Transformer Maintenance Testing of transformers z
Power factor test or “Doble” test
Readings should be .5% or less on newer equipment.
Readings should be 1% or less on older equipment that has been in service for a number of years.
12
Padmount transformers will usually run .7% to 1%.
Transformer Maintenance Testing of transformers z
13
Infrared test
This equipment checks for hot connections and hot spots.
Can be used to check how the cooling is working on transformers.
Transformer Maintenance Testing of transformers z
TTR test - Transformer Turns Ratio test
3 phase TTR set
Single phase TTR set
- Readings should not deviate more than ½ of 1% from the calculated value. 14
Transformer Maintenance Vacuum pressure devices
z
Vacuum pressure devices Used to control the amount of positive and negative pressure a transformer tank has on it.
15
Transformer Maintenance Pressure relief devices z
Pressure relief devices
Used to relieve pressure build up in the transformer. 16
Transformer Maintenance Sudden pressure relay z
Sudden pressure relay
This device detects a sudden rise in pressure in the transformer. 17
Transformer Maintenance Gaskets z
Gaskets shall be 1.33 times the height of groove and .75 times the width of the groove.
z
Types of gasket material:
18
Cork / Corkprene Nitrile / Buna N Rubber Viton Rubber
Transformer Maintenance Paint z
Types
19
Acrylic enamel Epoxy base
Break
20
Transformer Oil Testing Agenda
21
z
Transformer oil
z
Oil sampling
z
Oil quality
z
Dissolved gas analysis
z
Cellulose insulation
z
Oil processing
Transformer Oil Testing Transformer oil
22
z
Silicon based oil
z
Mineral oil
z
Synthetic oils
z
Ester / vegetable oils
Transformer Oil Testing Oil sampling
A Test is Only as Good as the Sample! Start with good, clean syringes!
23
Transformer Oil Testing Proper oil sampling
z
24
Do Not use small sampling port on side of drain valve.
Transformer Oil Testing Proper oil sampling
z
25
Flush drain valve, tubing, and syringe.
Transformer Oil Testing Proper oil sampling – (continued)
z
26
Do not pull back on the syringe barrel – apply slight resistance and allow fluid pressure to fill syringe.
Transformer Oil Testing Proper oil sampling – (continued)
z
27
Filled syringe should have no bubbles, but some may form later – do not release these!
Transformer Oil Testing Proper oil sampling – (continued) z
Excellent Sampling Guidelines available on Doble Engineering website
www.Doble.com Click on “Laboratory Services” Sampling Guides: Dielectric
Liquids Dissolved Gas Analysis
28
©2002 Doble Engineering Company All Rights Reserved
Transformer Oil Testing Oil quality z
Interfacial tension
z
Acidity
z
Moisture
z
Dielectric
z
Power factor
z
Color
29
Transformer Oil Testing Interfacial Tension - IFT z
Measure of contamination
z
Decreasing IFT = Increasing Contamination
z
Can be corrected
30
Transformer Oil Testing Acidity z
Measure of oxidation
z
Creates acidic compounds
z
Build-up of compounds forms sludge
z
Affects dielectric and cooling
z
Can be corrected
31
Transformer Oil Testing Moisture z
Decreases dielectric
z
Decreases IFT
z
Degrades cellulose
z
Failure risk
z
Can be corrected
32
Transformer Oil Testing Dielectric breakdown z
Voltage at which the oil begins to conduct
z
Is reduced by moisture and contaminants
z
Two ASTM test methods:
z
33
D-877
D-1816
Can be corrected
Transformer Oil Testing Power factor
z
Indication of contamination and/or deterioration
34
moisture carbon varnish soaps other conducting matter
Transformer Oil Testing Color z z z
35
Higher Number à Darker Oil Darker Oil à More Contamination, Deterioration Oil with Number of 5 is almost black
Transformer Oil Testing Dissolved gas analysis
z
36
DGA is the “blood test” for a transformer
Transformer Oil Testing Dissolved gas analysis z
Partial discharge (Corona - “electrical rust”)
z
High temperature heating
z
Acetylene C2H2
Cellulose involved
37
Methane CH4, Ethane C2H4, Ethylene C2H6
Arcing
z
Hydrogen H2
Carbon monoxide C0, and Carbon Dioxide CO2
Transformer Oil Testing Cellulose insulation z
38
The Life of the Transformer is directly related to the condition of the cellulose
Paper – windings, leads, shields
Pressboard – spacers, blocks, oil flows, tubes
Particle boards – supports
Laminates – structures, supports
Wood - structure
Transformer Oil Testing Paper z
39
Many layers of paper on this flux shield
Transformer Oil Testing Pressboard z
40
Pressboard Sheets for directing oil flow
Transformer Oil Testing Paper and pressboard
41
z
Paper wrapped windings
z
Pressboard spacers
Transformer Oil Testing Particle board
z
42
Particle Board Lead Support that flashed over
Transformer Oil Testing Laminates
43
z
Laminate Nuts
z
Laminate lead support structure members
Transformer Oil Testing Wood
z
44
Birch Structure Support Members
Transformer Oil Testing The Cellulose Polymer Chain The life of a transformer is directly related to the condition of this polymer chain.
45
Transformer Oil Testing Degree of polymerization z
Measure of mechanical strength
z
New paper = 1000 – 1400
z
Age increases
z
Industry accepted “End of Life” of cellulose
Ç
DP decreases
insulation is about 200 z 46
Estimated DP from Furan test
Transformer Oil Testing What degrades the cellulose? z
Primary sources
z
Secondary sources
47
Heat Moisture Oxygen
Acids from oil oxidation
Transformer Oil Testing Why is this important? z
Reduced dielectric strength
z
Reduced mechanical strength
48
Unable to withstand voltage stress from system transients
Unable to withstand mechanical stress from system faults
Transformer Oil Testing What can we do about it? z
z
49
Keep the Transformer Healthy!
Do not overheat
Keep moisture and oxygen out
If the Transformer is Sick, Get Help!
Investigate abnormal DGA results
Process or replace the oil
De-hydrate
Hot oil flush
Transformer Oil Testing Transformer oil processing
50
Transformer Oil Testing What processes?
51
z
De-gas
z
Dehydrate
z
Hot oil flush
z
Reclaim oil
Transformer Oil Testing Other maintenance options z
z
52
Upgrades to oil preservation system
Bladders
De-hydrating breathers
N2 blanket
On-line monitoring systems
Gas and moisture
Bushing monitors
Avoid Premature Failure!
53
Transformer Maintenance & Testing Thursday, November 6, 2003
Transformer Maintenance & Testing Purpose z
This presentation provides an overview of the major considerations associated with Transformer Maintenance and Testing.
z
Barker Edwards will provide the information for Transformer Maintenance & Testing.
z
Kate Brady will provide the information for Transformer Oil Testing.
2
Transformer Maintenance Things to know! Things you should know about keeping your transformer healthy!
3
Transformer Maintenance Agenda
4
z
Types of transformers
z
Yearly checks
z
Testing of transformers
z
Vacuum pressure device
z
Pressure relief device
z
Sudden pressure relay
z
Gaskets
z
Paints
Transformer Maintenance Types of transformers
z
Dry type transformers
5
Varnished coils
Transformer Maintenance Types of transformers
z
Dry type transformers
6
Cast coils
Transformer Maintenance Type of transformers
z
Oil filled transformers
7
Sealed tank
Transformer Maintenance Type of transformers
z
Oil filled transformers
8
Conservator system
Transformer Maintenance Type of transformers z
Oil filled transformers
Nitrogen blanket
Pressure regulator for Nitrogen Blanket transformer 9
Transformer Maintenance Yearly transformer checks z
Check vacuum pressure gauge for pressure reading.
z
Check oil level.
z
Check temperature maximum and minimum.
z
Check for leaks.
z
Check paint condition.
z
Check transformer top and radiators for foreign material.
z
Check radiator condition.
z
Check fans and cooling systems.
10
Transformer Maintenance Testing of transformers z
Megger test
600 megohms or better to ground is a good bench mark.
11
Transformer Maintenance Testing of transformers z
Power factor test or “Doble” test
Readings should be .5% or less on newer equipment.
Readings should be 1% or less on older equipment that has been in service for a number of years.
12
Padmount transformers will usually run .7% to 1%.
Transformer Maintenance Testing of transformers z
13
Infrared test
This equipment checks for hot connections and hot spots.
Can be used to check how the cooling is working on transformers.
Transformer Maintenance Testing of transformers z
TTR test - Transformer Turns Ratio test
3 phase TTR set
Single phase TTR set
- Readings should not deviate more than ½ of 1% from the calculated value. 14
Transformer Maintenance Vacuum pressure devices
z
Vacuum pressure devices Used to control the amount of positive and negative pressure a transformer tank has on it.
15
Transformer Maintenance Pressure relief devices z
Pressure relief devices
Used to relieve pressure build up in the transformer. 16
Transformer Maintenance Sudden pressure relay z
Sudden pressure relay
This device detects a sudden rise in pressure in the transformer. 17
Transformer Maintenance Gaskets z
Gaskets shall be 1.33 times the height of groove and .75 times the width of the groove.
z
Types of gasket material:
18
Cork / Corkprene Nitrile / Buna N Rubber Viton Rubber
Transformer Maintenance Paint z
Types
19
Acrylic enamel Epoxy base
Break
20
Transformer Oil Testing Agenda
21
z
Transformer oil
z
Oil sampling
z
Oil quality
z
Dissolved gas analysis
z
Cellulose insulation
z
Oil processing
Transformer Oil Testing Transformer oil
22
z
Silicon based oil
z
Mineral oil
z
Synthetic oils
z
Ester / vegetable oils
Transformer Oil Testing Oil sampling
A Test is Only as Good as the Sample! Start with good, clean syringes!
23
Transformer Oil Testing Proper oil sampling
z
24
Do Not use small sampling port on side of drain valve.
Transformer Oil Testing Proper oil sampling
z
25
Flush drain valve, tubing, and syringe.
Transformer Oil Testing Proper oil sampling – (continued)
z
26
Do not pull back on the syringe barrel – apply slight resistance and allow fluid pressure to fill syringe.
Transformer Oil Testing Proper oil sampling – (continued)
z
27
Filled syringe should have no bubbles, but some may form later – do not release these!
Transformer Oil Testing Proper oil sampling – (continued) z
Excellent Sampling Guidelines available on Doble Engineering website
www.Doble.com Click on “Laboratory Services” Sampling Guides: Dielectric
Liquids Dissolved Gas Analysis
28
©2002 Doble Engineering Company All Rights Reserved
Transformer Oil Testing Oil quality z
Interfacial tension
z
Acidity
z
Moisture
z
Dielectric
z
Power factor
z
Color
29
Transformer Oil Testing Interfacial Tension - IFT z
Measure of contamination
z
Decreasing IFT = Increasing Contamination
z
Can be corrected
30
Transformer Oil Testing Acidity z
Measure of oxidation
z
Creates acidic compounds
z
Build-up of compounds forms sludge
z
Affects dielectric and cooling
z
Can be corrected
31
Transformer Oil Testing Moisture z
Decreases dielectric
z
Decreases IFT
z
Degrades cellulose
z
Failure risk
z
Can be corrected
32
Transformer Oil Testing Dielectric breakdown z
Voltage at which the oil begins to conduct
z
Is reduced by moisture and contaminants
z
Two ASTM test methods:
z
33
D-877
D-1816
Can be corrected
Transformer Oil Testing Power factor
z
Indication of contamination and/or deterioration
34
moisture carbon varnish soaps other conducting matter
Transformer Oil Testing Color z z z
35
Higher Number à Darker Oil Darker Oil à More Contamination, Deterioration Oil with Number of 5 is almost black
Transformer Oil Testing Dissolved gas analysis
z
36
DGA is the “blood test” for a transformer
Transformer Oil Testing Dissolved gas analysis z
Partial discharge (Corona - “electrical rust”)
z
High temperature heating
z
Acetylene C2H2
Cellulose involved
37
Methane CH4, Ethane C2H4, Ethylene C2H6
Arcing
z
Hydrogen H2
Carbon monoxide C0, and Carbon Dioxide CO2
Transformer Oil Testing Cellulose insulation z
38
The Life of the Transformer is directly related to the condition of the cellulose
Paper – windings, leads, shields
Pressboard – spacers, blocks, oil flows, tubes
Particle boards – supports
Laminates – structures, supports
Wood - structure
Transformer Oil Testing Paper z
39
Many layers of paper on this flux shield
Transformer Oil Testing Pressboard z
40
Pressboard Sheets for directing oil flow
Transformer Oil Testing Paper and pressboard
41
z
Paper wrapped windings
z
Pressboard spacers
Transformer Oil Testing Particle board
z
42
Particle Board Lead Support that flashed over
Transformer Oil Testing Laminates
43
z
Laminate Nuts
z
Laminate lead support structure members
Transformer Oil Testing Wood
z
44
Birch Structure Support Members
Transformer Oil Testing The Cellulose Polymer Chain The life of a transformer is directly related to the condition of this polymer chain.
45
Transformer Oil Testing Degree of polymerization z
Measure of mechanical strength
z
New paper = 1000 – 1400
z
Age increases
z
Industry accepted “End of Life” of cellulose
Ç
DP decreases
insulation is about 200 z 46
Estimated DP from Furan test
Transformer Oil Testing What degrades the cellulose? z
Primary sources
z
Secondary sources
47
Heat Moisture Oxygen
Acids from oil oxidation
Transformer Oil Testing Why is this important? z
Reduced dielectric strength
z
Reduced mechanical strength
48
Unable to withstand voltage stress from system transients
Unable to withstand mechanical stress from system faults
Transformer Oil Testing What can we do about it? z
z
49
Keep the Transformer Healthy!
Do not overheat
Keep moisture and oxygen out
If the Transformer is Sick, Get Help!
Investigate abnormal DGA results
Process or replace the oil
De-hydrate
Hot oil flush
Transformer Oil Testing Transformer oil processing
50
Transformer Oil Testing What processes?
51
z
De-gas
z
Dehydrate
z
Hot oil flush
z
Reclaim oil
Transformer Oil Testing Other maintenance options z
z
52
Upgrades to oil preservation system
Bladders
De-hydrating breathers
N2 blanket
On-line monitoring systems
Gas and moisture
Bushing monitors
Avoid Premature Failure!
53
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