updea

Report
TRANSFORMER PROTECTOR
4th UPDEA SCIENTIFIC COMMITTEE
March 12, 2008
Transformer Operations & Failure
Avoidance
Rui Da Silva,
SERGI FRANCE
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TRANSFORMER PROTECTOR
Introduced Power Factor Testing 1929
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TRANSFORMER PROTECTOR
What We Are Trying To Avoid
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TRANSFORMER PROTECTOR
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TRANSFORMER PROTECTOR
Number of Transformer Events/Yr
20
15
10
5
0
'91
'92
'93
'94
'95
'96
'97
'98
'99
'00
'01
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TRANSFORMER PROTECTOR
Data Sources (1)
Insurance - Carrier & Industry Sources
Allianz
Munich Re
Swiss Re
Lloyds Syndicates
Factory Mutual Research & Engineering
FM Global, previously
Allendale Mutual
Arkwright Mutual
Protection Mutual
AIG / Hartford Steam Boiler Inspection and Insurance
Royal Insurance
Industrial Risk Insurers
American Insurance Association
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TRANSFORMER PROTECTOR
Data Sources (2)
Power Industry Sources
 Edison Electric Institute
 McCoy Power Reports
 INPO Operational Reliability Program
 IEEE RAM Comm (Reliability Availability & Maintainability
 Utility Data Institute
 Electric Power Reserch Institute
 American Power Conference, extracts 1990 to 2001
 Intl. Joint Power Conference, extracts 1989 to 2001
 MFR’s : GE, Alstom, ABB, Siemens, Westinghouse
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TRANSFORMER PROTECTOR
Aging Forecast
latest forecast model …..
A + a e bt
1 + µe bt
f(t) =
100%
90%
H az ar d Function
80%
70%
60%
50%
40%
30%
20%
10%
74
68
62
56
50
44
38
32
26
20
14
8
2
0%
Age
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TRANSFORMER PROTECTOR
Insurer’s Exposure to Losses
32%
SYSTEMS &
COMPONENTS
START
10% Rise

18%
15%
10%
<2%
Civil
Erection
4%
18%
Mechanical
Completion
63%
Testing
8%
Performance
5%
Operational
= 15 Year History
= 2002/2006
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TRANSFORMER PROTECTOR
Forced Outage
(Unplanned Maintenance/Repair Times)
Time-to-Repair Distributions for Minor, Major
and Catastrophic Events
0.10
0.09
Catastrophic
(230 hr/event)
0.08
Probability
0.07
0.06
MINOR
(5 hr/ event)
MAJOR
(55 hr / event)
10
100
0.05
0.04
0.03
0.02
0.01
0.00
1
1,000
Time to Repair, Hours
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TRANSFORMER PROTECTOR
US Power Plant Fatalities
14
12
Total: 35 people
10
8
6
4
2
0
1971 1976 1977 1989 1992 1993 1994 1995 1999 2000
Fatalities due to
Explosions and Fires
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TRANSFORMER PROTECTOR
Transformer Failure Modes
Thermally induced
Electrically Induced
Mechanically Induced
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TRANSFORMER PROTECTOR
Transformer Failure Modes
Electrically
Induced
• Over Voltage
• Surges
• Partial
Discharge
• Static
Electrification
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TRANSFORMER PROTECTOR
Transformer Failure Modes
Mechanically Induced
Conductor
Tipping
Conductor
Telescoping
Hoop Buckling
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TRANSFORMER PROTECTOR
Mechanical Failure
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TRANSFORMER PROTECTOR
Transformer Failure Modes
Thermally Induced




Overloading
Failure of cooling system
Blockage of axial spaces
Over-excitation (over-voltage or
under-frequency)
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TRANSFORMER PROTECTOR
Cause of Failures
Moisture
7%
Overload
2%
Other
2%
Electrical
Disturbances
29%
Loose
Connection
13%
Maintenance
issues
13%
Lightning
16%
Insulation
issues
18%
20 years of claims
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TRANSFORMER PROTECTOR
Types of Transformers
Distribution, for residential service
Generator Step-up Transformers
Autotransformers
Multi-winding transformers(> 2 windings)
Rectifier Transformers--Smelters
Furnace Transformers--Steel Mills
Inverter Transformers-DC
Converter Transformers-DC
Regulating Transformers--Voltage, Current Phase, Angle
Instrument Transformers--Voltage/Current
Other
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TRANSFORMER PROTECTOR
Generator Step-Up Transformers
(GSU’S)
Usually (90%+) two-winding transformers
Large KVA (50000kVA and higher, up to 1,300,000 kVA)
Used at Power Plants
Fossil-Coal/Oil/Gas
Nuclear
Hydro
Raises the voltage from the generator voltage (12-26 kV)
to the Transmission System Voltage (69-765kV)
to allow efficient transmission of power from the
energy source to the load.
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TRANSFORMER PROTECTOR
Autotransformers
•Primary use is to connect two transmission systems of different voltages
•The two systems must by Y-connected and of the same phasing and polarity
•“Short-ended” autos (re 200/190 kV) or “long-ended” (200/20 kV) are not
practical.
•Autotransformers can step voltage up or down.
Typical voltage ratings of Autotransformers in NA
138/69 kV
230/115 kV
345/138 kV
345/230kV
500/230kV
500/345kV
765/345 kV
765/500 kV
765/138 kV
500/161 kV
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TRANSFORMER PROTECTOR
►How to protect your investment?
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TRANSFORMER PROTECTOR
Transformer Specification
 Evaluate system requirements
 Evaluate transformer requirements
 Evaluate client standards
 Review or create entire specification
 Design Review – At Factory
 Drawing & Materials Review
 Scheduling Coordination
 Core & Coil – Pretank Inspection
 Factory Test
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TRANSFORMER PROTECTOR
Core Form vs Shell Form Transformers
 Core Form
 Shell Form
Round Coils( Cylinder)
Coils Wrapped on a tube then
loaded on core
Core stacked in legs and then
windings are placed over
them
Vertical Core Legs
Windings Concentric around
each other
Majority of Transformers in the
world
Flat Coils in rectangular shape
Coils stacked into groups
Interleaved windings
Core stacked around the coils
Core is Horizontal
Stronger under short circuit
Generally more expensive
Major advantages in GSU’s
ABB (Cordoba), IEM (Mexico),
Schneider (France), Mitsubishi
(Japan), Hyosung (Korea),
GE (UNITED STATES!)
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TRANSFORMER PROTECTOR
Basic Construction
SHELL FORM
CORE FORM
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TRANSFORMER PROTECTOR
Core Form Construction
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TRANSFORMER PROTECTOR
Shell Form Construction
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TRANSFORMER PROTECTOR
Single Phase vs Three Phase Units
 Three Phase




Most Economical
Smallest footprint
Simplifies station design
Most Common
 Single Phase
-
Min of 3 units
Easier to spare (4th Tx)
Greater
Reliability/Availability
3-Phase too large to ship
Larger footprint
More Expensive
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TRANSFORMER PROTECTOR
Field Testing - Oil Diagnostics
 OIL










Dissolved Gas Analysis (DGA) Profile (Main Tank, OLTC)
Furan Analysis
Moisture Content
Dielectric Strength
Oil Condition
Inhibitor Content
Metals
Corrosive Sulfur
Acidity
Degree of Polymerization
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TRANSFORMER PROTECTOR
The different components of the protection
7
2
6
1
3
5
4
1.
Depressurization Set
4.
Explosive Gas Elimination Pipe
2.
OLTC Depressurization Set
5.
Cabinet
3.
Oil-Gas Separation Tank
6.
Explosive Gases Evacuation
7.
Conservator Shutter
To create an evacuation opening before the dynamic pressure
becomes uniform static pressure
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TRANSFORMER PROTECTOR
THE TRANSFORMER PROTECTION :
OPERATION


1/ The dynamic pressure peak travels at the speed of sound inside oil
2/ Rupture
of the disk,
depressurisation,
evacuation of the
oil-gases mixture



3/ Opening of the air
isolation shutter
4/ Nitrogen injection
5/ Explosive gases
production is
stopped after 45 min
N2
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TRANSFORMER PROTECTOR
COMPUTATIONAL INVESTIGATIONS
Pressure Wave
Propagation
Gas and Oil
Behaviours
Compressible
Two-Phase Flow Model
EM, thermal, viscosity, gravity
Complex
Geometry
Numerical Tool
Finite
Volume Method on
Unstructured mesh
2002 and 2004 Tests on
Transformers
Numerical Tool
Validation
High Fault Currents
Extrapolation to
Transformers
>100MVA
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Protection
Validation
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TRANSFORMER PROTECTOR
 a
 
 0
 u . a

t

 a g


 0
 div a g u 
 t
  1  a  

l
 l u   Modeling
0
 div 1  aPhysical

t






 u
  g  div  
 div   u  u    P
 t

 


E

  g .u  div   .u
 div  E  P u 
 t
 
 
Equation of state :
Hydro
Effect
Modelling
Gravity
Effect
Modelling
Energy
Transfer
Modelling
 E
Viscous
Effect
Modelling
P    1   e   P
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TRANSFORMER PROTECTOR
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TRANSFORMER PROTECTOR
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TRANSFORMER PROTECTOR
Any Questions?
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