TRANSFORMER PROTECTOR Quit 4 th UPDEA SCIENTIFIC COMMITTEE March 12, 2008 Transformer Operations & Failure Avoidance Rui Da Silva , SERGI FRANCE

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Quit TRANSFORMER PROTECTOR Introduced Power Factor Testing 1929

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Quit TRANSFORMER PROTECTOR What We Are Trying To Avoid

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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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Quit 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 7

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Aging Forecast

latest forecast model …..

f (t) = 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

Age

A + a e b t 1 + µ e b t 8

TRANSFORMER PROTECTOR Insurer’s Exposure to Losses

32% 10% Rise  SYSTEMS & COMPONENTS START 10% 18% 15%

Civil

<2%

Erection

4% 18%

Mechanical Completion Testing

63%

Performance

8% 5%

Operational

= 15 Year History = 2002/2006

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Quit TRANSFORMER PROTECTOR Forced Outage (Unplanned Maintenance/Repair Times) Time-to-Repair Distributions for Minor, Major and Catastrophic Events

0.01

0.00

1

0.08

0.07

0.10

0.09

0.03

0.02

0.06

0.05

0.04

MINOR (5 hr/ event) Catastrophic MAJOR (55 hr / event) (230 hr/event) 10 100 Time to Repair, Hours 1,000

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Quit TRANSFORMER PROTECTOR US Power Plant Fatalities 14 12 10 8 6 4 2

Total: 35 people

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 Quit



Thermally induced



Electrically Induced



Mechanically Induced

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Quit 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 Quit

Conductor Tipping Conductor Telescoping Hoop Buckling 15

Quit 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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Quit TRANSFORMER PROTECTOR Cause of Failures Moisture 7% Loose Connection 13% Overload 2% Other 2% Electrical Disturbances 29% Maintenance issues 13% Lightning 16% Insulation issues 18% 20 years of claims

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Quit 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 19

Quit 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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Quit 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

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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 21

Quit 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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Quit TRANSFORMER PROTECTOR Core Form vs Shell Form Transformers



Core 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 

Shell Form

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!) 24

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Basic Construction

SHELL FORM CORE FORM

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Core Form Construction

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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.

2.

3.

Depressurization Set OLTC Depressurization Set Oil-Gas Separation Tank 4. Explosive Gas Elimination Pipe 5.

6.

7.

Cabinet Explosive Gases Evacuation Conservator Shutter

To create an evacuation opening before the dynamic pressure becomes uniform static pressure Quit

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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

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Pressure Wave Propagation

TRANSFORMER PROTECTOR COMPUTATIONAL INVESTIGATIONS

Gas and Oil Behaviours Complex Geometry Compressible Two-Phase Flow Model EM, thermal, viscosity, gravity Numerical Tool Finite Volume Method on Unstructured mesh 2002 and 2004 Tests on Transformers High Fault Currents Numerical Tool Validation Extrapolation to Transformers >100MVA Protection Validation

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TRANSFORMER PROTECTOR

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Quit Hydro Effect Modelling Gravity Effect Modelling Energy Transfer Modelling Viscous Effect Modelling

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Any Questions?

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