Transformer Protector

TRANSFORMER PROTECTOR The Only Solution Against Transformer Explosion

TRANSFORMER TRANSFORME R PROTECTOR Presentation www.sergi-france.com

D u r i n g a t r a n s f o r m e r s h o r t c i r c u i t , t h e T R A N SF SF O R M ER ER P R O T E CT CT O R i s a c t i v a t e d w i t h i n m i l l i s e c o n d s b y t h e f i r s t

1/ Transformers explosions 2/ TP principle

NFPA

3/ Physical explanations 4/ Technical description 5/ TP References

The TRANSFORMER PROTECTOR is now recommended for all Power Plants and Substations in the National Fire Protection Association 2010 edition of: • NFPA NFPA 850 (Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations), • NFPA NFPA 851 (Recommended Practice for Fire Protection for Hydroelectric Generating Plants).

The introduction of the 2010 edition of NFPA NFPA 850 & NFPA NFPA 851 85 1 stands : “Fast depressurisation systems have been recognized, and recommendations for the use of these systems are now included ” “Fast depressurisation system: a passive mechanical system system designed to depressurize the transformer a few milliseconds after the occurrence of an electrical fault” More details later in the presentation or Just click here TRANSFORMER PROTECTOR

1/ Transformers explosion explosionss 2/ TP principle

Overview of the presentation


1. Transformers are very dangerous • Examples of explosions

• Conventional Conventional protections

• The answer

2. The TP principle to prevent transformer transformer explosion • TP strategy

• Why do transformers explode ?

3.

Physical explanations • Experimental tests • Physical Physical phenomena phenomena

4.

• Simulations (model, Simulations (model, application application 200 MVA) • Real case case study (400 MVA) MVA)

TP technical description • Standard configuration • The TP components

5.

• Detailed TP operation

configurations • Other configurations • TP options

• Retrofitting • TP order order process process

References NFPA, FM Global, IEEE… • NFPA, • World references

• Successful activations • Examples Examples of installation installationss

Conclusion TRANSFORMER PROTECTOR


Just click on presentation the SERGI logo to go Overview of the back to the “overview page”



• Conventional protections

• The answer

2. The TP principle to prevent transformer explosion • TP strategy


3.

Click here if you want to see the Physical explanations • Experimental tests • Physical phenomena

4.


“detailed TP operation”

• Simulations (model, application 200 MVA) • Real case study (400 MVA)

TP technical description

From this “overview” page, you can navigate • Other configurations • Retrofitting • TP options TP order process through the complete presentation• by clicking 5. References on the item you want to see • Standard configuration • The TP components

• NFPA, FM Global, IEEE… • World references

• Successful activations • Examples of installations



Overview of the presentation



• Conventional protections

• The answer

2. The TP principle to prevent transformer explosion • TP strategy


3.

Physical explanations • Experimental tests • Physical phenomena

4.

• Simulations (model, application 200 MVA) • Real case study (400 MVA)

TP technical description • Standard configuration • The TP components

5.


• Other configurations • TP options

• Retrofitting • TP order process

References • NFPA, FM Global, IEEE… • World references

• Successful activations • Examples of installations


1/ Transformers explosions

1. Transformers are very dangerous

2/ TP principle 3/ Physical explanations 4/ Technical description 5/ TP References

1. Transformers are very dangerous •

Examples of explosions

•

Conventional protections

•

The answer

TRANSFORMER PROTECTOR



2/ TP principle 3/ Physical explanations


4/ Technical description 5/ TP References

Power transformers are very dangerous Danger : • Large quantity of oil in contact with high voltage elements

• No international security norm for transformers

Transformer explosion in a power plant • The whole power plant (1,350MW) was out of service for 4 months. • The damaged section (450 MW) was out of service for 13 months. • 2 people were badly burned. • Fire extinguishing systems did not work. • Security fire doors were too slow. TRANSFORMER PROTECTOR






Transformer explosions lead to:

Other explosion examples

2

• Huge fire • Plant outage • Huge costs :

hundreds millions Euros • Ruin company reputation • Environmental pollution Ottawa Hydro, Canada, March 2009

• Human life risks

transformer burned during hours









3


hundreds millions Euros • Ruin company reputation • Environmental pollution • Human life risks

Krümmel Nuclear Power Plant, Germany June 2007, still not restarted ! Cost: 1 Million Euros / day ! TRANSFORMER PROTECTOR








4


hundreds millions Euros • Ruin company reputation • Environmental pollution • Human life risks

Blénod Coal Power Plant, EDF, France May 2009 TRANSFORMER PROTECTOR





1


Corrective Means

• Firewalls

Efficiency ?

• Fire extinguishing systems

Limit fire propagation induced by the explosion

a) South Band, Illinois , USA, 1999

Fire propagated from one transformer to the other






1


Corrective Means

• Firewalls

Efficiency ?

• Fire extinguishing systems

Limit fire propagation induced by the explosion

b) Venice Plant, Illinois , USA, 2000

Fire propagated to the whole plant: All 9 transformers caught fire despite fire walls and fire extinguishing systems (cost: USD 230 millions)

Solution : Preventing transformer explosion to avoid fire TRANSFORMER PROTECTOR





2


Preventive Means

Efficiency ?

• Circuit breakers • Buchholz Relay • Sudden Pressure Relay

All exploded transformers were equipped with these devices

• Gas Monitoring • Pressure Relieve Valve

Solution : The protection must act faster ! TRANSFORMER PROTECTOR


1. Transformers are very dangerous The answer


The TRANSFORMER PROTECTOR (TP) The TP depressurizes transformers within milliseconds avoiding explosion and subsequent fire. The TP key of success

During a short circuit, the TP is activated within milliseconds by the first dynamic pressure peak of the shock wave, avoiding explosions by preventing static pressure increase. TRANSFORMER PROTECTOR


2. Preventing transformer explosion: the TP Principle


2. Preventing Transformer Explosion:

The TP Principle •

Transformer explosion process

•

TP strategy to prevent explosion

•

TP operation

•

TP standard configuration

•

TP operation movie



2. Preventing transformer explosion: the TP principle Transformer explosion process

Dielectric oil insulation rupture Electrical arc


Why do transformers explode ?

Oil vaporization Local dynamic pressure increase First dynamic pressure peak propagates Dynamic pressure peak reflects off walls Static pressure increases

Tank rupture & Fire TRANSFORMER PROTECTOR


2. Preventing transformer explosion: the TP principle Prevention strategy



How to break that sequence?

Oil vaporization Local dynamic pressure increase First dynamic pressure peak propagates Dynamic pressure peak reflects off walls Static pressure increases

Tank rupture & Fire TRANSFORMER PROTECTOR


2. Preventing transformer explosion: the TP principle


Prevention strategy



How to break that sequence?

Oil vaporization Local dynamic pressure increase First dynamic pressure peak propagates Dynamic pressure peak reflects off walls

Activation within milliseconds by the first dynamic pressure peak

Tank depressurization

Prevents the explosion TRANSFORMER PROTECTOR

Quick Oil Evacuation


2. Preventing transformer explosion: the TP principle TP operation






• Electrical arc • Pressurized gas bubble • Dynamic pressure peak propagation






1

2/ TP principle

TP Activation

Quick oil evacuation generating fast depressurization of the tank (within milliseconds)






1

2/ TP principle

TP Activation

Quick oil evacuation generating fast depressurization of the tank (within milliseconds) • Explosive gases remain • Melting parts of the windings are still emitting gases




5/ TP References

• Pressurized gas bubble • Dynamic pressure peak propagation

TP Activation

Quick oil evacuation generating fast depressurization of the tank (within milliseconds) • Explos Explosive ive gases gases remain remain • Melt Meltin ing g part partss of the the wind windin ings gs are are stil stilll emit emitti ting ng gase gasess

2

3/ Physical explanations 4/ Technical description

• Electrical arc

1

2/ TP principle

Injection of Inert Gas

Evacuation of the explosive gases until the melted parts are cooled down (~ 45 mn)



2. Preventing transformer explosion: the TP principle TP operation • Electrical arc • Pressurized gas bubble • Dynamic pressure peak propagation

1

TP Activation


2



Transformer safe and ready for repair TRANSFORMER PROTECTOR



2. Preventing transformer explosion: the TP principle TP standard configuration


Standard TRA TRANSF NSFOR ORME MER R PR PRO OTE TECT CTOR OR (TP (TP)) The Components TP Components

3 1 2

4 5

1. Vertical Depressurization Set (VDS) 2. OLTC Depressurization Set (OLTC DS) 3. Slice Oil-Gas Separation Tank Tank (SOGST) 4. Explosive Gases Evacuation Pipe (EGEP) 6

5. Air Isolation Shutter 6. TP Cabinet

7

7. Inert Gas Injection Pipe (IGIP) TRANSFORMER PROTECTOR


3. Physical Explanations


3.

Physical Explanations • General overview of the experimental tests • Exhibited physical phenomena: 

Oil vaporization



Dynamic pressure peak propagation



Tank can withstand high dynamic pressure peak



Tank rupture because of static pressure increase



TP reaction to the phenomena

• Simulations: 

Quick presentation of the simulation tool



Comparison with / without TP



Real case study – 400 MVA explosion prevention

• Tank design using ASME standards TRANSFORMER PROTECTOR




Experimental tests: general overview

Two main test campaigns • 2002: 28 tests by EDF (Electricité de France) on small transformers







Two main test campaigns • 2002: 28 tests by EDF (Electricité de France) on small transformers • 2004: 34 tests by CEPEL (HV independent lab.) on large transformers (8.4m – 26ft)








Two main test campaigns • 2002: 28 tests by EDF (Electricité de France) on small transformers • 2004: 34 tests by CEPEL (HV independent lab.) on large transformers (8.4m – 26ft) • Principle: electrical arcs were ignited inside transformers tanks equipped with a TP Click on pictures to watch videos

Conclusion During the 62 tests, the TP always saved transformers from explosion without permanent tank deformation TRANSFORMER PROTECTOR




3.


Oil vaporization & gas creation












TP reaction to the physical phenomena









• Tank reinforcements influence using ASME standards TRANSFORMER PROTECTOR




Vaporization saturation process 1

4/ Technical description

SKIP

5/ TP References

1st key phenomena: oil vaporization & arc creation – video

Arc movie during the EDF tests High speed camera 3000 fps

Chronology 0 ms

: Start of applied current

3.66 ms : Bubble generation 4 ms

: Bubble volume = 9 cm 3, 0.5 in. 3

4.33 ms : Bubble volume = 60 cm3, 3.7 in. 3 4.66 ms : Bubble volume = 97 cm3, 5.9 in. 3 5 ms


5.33 ms : Bubble volume = 299 cm3, 18.2 in. 3

6.33 ms

5.66 ms

: Bubble volume = 399 cm3, 24.3 in. 3

6 ms


: Electrical arc fully developed - plasma TRANSFORMER PROTECTOR


3. Physical Explanations and Testing of the TP Vaporization saturation process 1

2/ TP principle 3/ Physical explanations 4/ Technical description

SKIP

5/ TP References

1st key phenomena: oil vaporization & arc creation – video

Electrical Arc

Produced Gas

Plasma

Mineral Oil







1st key phenomena: oil vaporization & arc creation – description Short circuit Transformer Oil

Electrical current between 2 points of the transformer Heat transfer to the oil Vaporization (Joule effect)

Gas bubble – oil vapor Cracking oil vapor into smaller molecules

Gas bubble gases with low resistivity Less resistivity

= more current

Electrical arc fully developed – Plasma







SKIP

5/ TP References

1st key phenomena: oil vaporization & arc creation – analyse

a) Flammable and explosive gases are created: •

Acetylene (C2H2), Ethylene (C2H4), Methane (CH4), Hydrogen….

•

These gases ignite when exposed to Oxygen

•

Example:

• An 0.8 Mega Joule electrical arc occurred in one transformer. • 1.8 m3 (62.4ft 3) of gas was created, exploded the tank, escaped & ignited

• The fire ball propagates in the whole section looking for oxygen and destroys everything on its path. • The section (450 MVA) was out of service for 13 months! TRANSFORMER PROTECTOR




Vaporization saturation process

5/ TP References


1

c) Physical explanation: 1st step

b) Measurements ) 3

m n i ( e m u l o V s a G d e t a r e n e G

1st


HEAT EXCHANGE ARC TO OIL

Gas

1st step:

HEAT EXCHANGE Arc in contact with ARC TO OILoil HEAT EXCHANGE ARC TO OIL

Enormous Vaporization Transformer Oil

Arc Energy (in MJ)

1st

step: the Mega Joule produces 3 2.3 m – 81 ft3 of explosive gas

• When the arc occurs, direct contact between arc and liquid oil • High energy exchange to liquid oil Fast & huge vaporization








1

c) Physical explanation: 2nd step

b) Measurements ) 3


Gas 1) HEATING THE GAS 2) IONISATION 3) CREATION OF PLASMA

Transformer Oil

Arc Energy (in MJ)

1st step: the 1st Mega Joule produces 2.3 m3 – 81 ft3 of explosive gas 2nd step: the following 19 MJ produce only 1.2 m3 – 42 ft3 of gas

• Arc surrounded by gas • Gas heated by the arc (~2000 C) and then ionized, creating plasma • Less energy transfer to liquid oil


Much slower vaporization







1

c) Physical explanation: 2nd step

b) Measurements ) 3


Gas 1) HEATING THE GAS 2) IONISATION 3) CREATION OF PLASMA

Transformer Oil

Arc Energy (in MJ)

Vaporisation Saturation The oil vaporization occurs in the first milliseconds and stabilizes when the electrical arc is surrounded by gas TRANSFORMER PROTECTOR




Pressure increase in the gas bubble


1

1st key phenomena: oil vaporization & arc creation

2

2nd key phenomena: quick pressure increase in gas bubble Gas density is ~1000 times less than liquid density The gas bubble wants to expend But liquid oil inertia avoids the bubble expansion

Transformer Oil

Fast pressure increase in the gas bubble (up to 5000 bar/s – 75000 psi/s)





Pressure increase in the gas bubble


1


2

2nd key phenomena: quick pressure increase in gas bubble Maximum pressure peak amplitude recorded for each test (gauge pressure): +10.5 bar (150 psi) 125 kJ

+9 bar (130 psi) 1 MJ

+13 bar (190 psi) 2.5 MJ

+3 bar (40 psi) 1 MJ

Only a moderate influence of the arc energy to the bubble pressure TRANSFORMER PROTECTOR




Pressure increase in the gas bubble 1


2

2nd key phenomena: quick pressure increase in gas bubble


• Vaporization saturation process • Only a moderate influence of the arc energy to the pressure peak amplitude

Arc energy and transformer power rating are not the critical factors for transformer explosion! TRANSFORMER PROTECTOR




Dynamic pressure propagation


1


2

2nd key phenomena: quick pressure increase in the gas bubble

3

3rd key phenomena: the dynamic pressure peak propagates Transformer Oil





Dynamic pressure propagation 3


3rd key phenomena: the dynamic pressure peak propagates

Close to the arc (C) At the tank cover (B) Close to the TP (A)

TP A B

arc

C

Gauge pressure evolution measured at different locations

• Overpressure generated by the arc is not uniform in the tank • The pressure peak propagates at the speed of sound in the oil

•

1200 m/s ie 4000 ft/s Secondary peaks are due to reflections of the first peak off the walls TRANSFORMER PROTECTOR

Dynamic Pressure




Tank withstand to dynamic pressure


1


2


3


4

4th key phenomena: tank can withstand high dynamic pressure peaks





Tank withstand to dynamic pressure 4


4th key phenomena: tank can withstand high dynamic pressure peaks Maximum dynamic pressure peak amplitude recorded for each test (gauge pressure):

+11 bar (160 psi)

+13 bar (190 psi) +10.5 bar (150 psi)

No Rupture !

Tank can withstand dynamic pressure peaks up to +13 bar – 190 psi (gauge) TRANSFORMER PROTECTOR




Tank withstand to dynamic pressure 4


4th key phenomena: tank can withstand high dynamic pressure peaks Physical explanation:

Dynamic Pressure • Very localized and moving in the tank

Tank withstand capabilities • Tank welding and bolts have a long inertia to break

• Propagates very quickly within the tank (1200 m/s – 4000 ft/s)

• Dynamic pressure peak is traveling very fast: welding and bolts have no time to integrate the pressure.

No rupture induced by dynamic pressure! TRANSFORMER PROTECTOR




Tank ruptures due to static pressure


1


2


3


4


5

5th key phenomena: tanks rupture because of static pressure





Tank ruptures due to static pressure 5


5th key phenomena: tanks rupture because of static pressure pressure gradients less than 25 bar/s – 350 psi/s

• Static Pressure: uniform and progressive pressure increase all over the tank • Slow phenomena for which oil reacts like incompressible media • Tank maximum static withstand limit: between 0.7 and 1.2 bar (gauge).

Tanks rupture because of static pressure TRANSFORMER PROTECTOR




Dynamic / static pressure


Dynamic Pressure

Static Pressure

Pressure gradients over 25 bar/s – 360 psi/s

Pressure gradients under 25 bar/s – 360 psi/s

• Very localized and moving in the tank

• Spatially uniform all over the tank

• Propagates quickly within the tank

• Progressive, slow increase

• Oil behaves as a compressible media

• Oil behaves as an incompressible media

• Tank can resist 13 bar – 190 psi (gauge) • Max withstand ~1 bar – 15 psi (gauge) Propagation speed: 1200 m/s – 4000 ft/s

Pressure gradients up to 5000 bar/s – 72000 psi/s

The tank does not explode TRANSFORMER PROTECTOR

The tank explodes






How does Dynamic Pressure become Static Pressure ? The dynamic pressure peak travels and reflects off the walls, creates secondary peaks building slowly static pressure.







How does Dynamic Pressure become Static Pressure ? Evolution of the pressure at different sensors in the tank:

Simulation parameters • • • •

No TP installed on the transformer Supposing the tank does not explode 5.6 m – 19 ft long transformer 0.5 MJ fault generating 1.5 m3 – 50 ft 3 of gas.







How does Dynamic Pressure become Static Pressure ? Evolution of the pressure at different sensors in the tank: 1. The arc generates one high pressure peak 2. This dynamic pressure peak propagates in the tank 3. Reflects off the wall and creates secondary peaks 4. Static pressure is built up after only 100 ms TP Strategy To prevent Dynamic Pressure from becoming Static Pressure TRANSFORMER PROTECTOR




Influence of the TP


1


2


3


4


5

5th key phenomena: tank ruptures because of static pressure

6

6th key phenomena: the TP depressurizes tanks preventing explosion





Influence of the TP 6



Dynamic pressure sensor located close to the TP Traveling distance : 8,5 m – 26 ft

Depressurization Set

Windings TRANSFORMER PROTECTOR

Electrical Arc at the opposite side of the TP







Dynamic pressure recorded close to the depressurization set

The TP is activated in 8 ms, time for the dynamic 58000 psi/s

pressure peak generated by the arc to reach the sensor:

8.5 m at 1200 m/s (26 ft at 4000 ft/s)

8 ms The TP depressurizes the tank in milliseconds, even if the arc is fed for a longer period TRANSFORMER PROTECTOR







Dynamic pressure recorded close to the depressurization set

No static pressure 58000 psi/s

No tank rupture

The TP depressurizes the tank in milliseconds, even if the arc is fed for a longer period TRANSFORMER PROTECTOR







a) No static pressure The quick oil evacuation generates

Oil Dyn. pressure travelling Arc TP is evacuation Tank is

rarefaction waves that

occurrence

depressurizes the tank before static pressure builds up.

0

activated

depressurized

~10 ms

~80 ms

b) No explosive gases ignition The gases created by the arc are:

•

cooled down

•

diluted with inert gases

•

evacuated to a remote area

The TP prevents transformer explosions & fires





TP key of success


Recapitulation of the main Recapitulation of the mainphysical physicalphenomena phenomena 1. The vaporization saturation 2. The dynamic pressure propagates 3. Tank can withstand high dynamic pressure peaks 4. Tanks rupture because of static pressure 5. The TP induces a fast depressurization preventing the tank explosion Dynamic pressure peak propagation (up to 13 bar – 190 psi)





TP key of success


Recapitulation of the main Recapitulation of the mainphysical physicalphenomena phenomena 1. The vaporization saturation 2. The dynamic pressure propagates 3. Tank can withstand high dynamic pressure peaks 4. Tanks rupture because of static pressure 5. The TP induces a fast depressurization preventing the tank explosion

TRANSFORMER PROTECTOR key of success During a short circuit, the TP is activated within milliseconds by the first dynamic pressure peak of the shock wave, avoiding explosions by preventing static pressure increase. TRANSFORMER PROTECTOR




3.


Oil vaporization












TP reaction to the physical phenomena









• Tank reinforcements influence using ASME standards TRANSFORMER PROTECTOR




Simulation tool – Presentation 


During the 62 tests, electrical arcs were always ignited inside closed transformers tanks equipped with TP The TP always saved transformers without permanent tank deformation



What would happen without TP ?



What would happen in other configurations ?

Explosion: too dangerous to test Too costly to test

Using computer simulations is an alternative 

SERGI has developed its own simulation tool: 

Simulate gas and liquid



Pressure propagation



Complex 3D geometries



Leads to various scientific publications (2008 PowerGen Conference Best Paper Award, IEEE, Cigre and ASME Conferences…) TRANSFORMER PROTECTOR




Simulation tool – 200 MVA transformer – no protection

Application 1: 200 MVA Transformer (5.75m x 3.25m x 2.5m) – (19ft x 11ft x 8ft) t = 0 ms

without TP Pressure (gauge) (psi)

(bar)



SKIP

5/ TP References

11 MJ electrical arc






11 MJ electrical arc t = 1 ms

1 ms


(bar)


Gas bubble under pressure






11 MJ electrical arc t= 2 3 ms 4

1 ms


4 ms

The first dynamic pressure peak propagates


(bar)







11 MJ electrical arc t = 10 8 7 6 5 ms 9 ms

1 ms


4 ms


10 ms

Reflects off the walls and creates complex pressure waves


(bar)







11 MJ electrical arc t = 25 15 17 22 13 16 18 20 11 ms 12 14 19 24 30

1 ms


4 ms


10 ms


30 ms

Dynamic pressure reach more than 9 bar – 130 psi (gauge) in a bushing


(bar)







11 MJ electrical arc t = 40 35 38 ms 45 50

1 ms


4 ms


10 ms


30 ms


50 ms

Static pressure builds up


(bar)







11 MJ electrical arc t = 70 60 50 ms 80 100 ms

1 ms


4 ms


10 ms


30 ms


50 ms

Static pressure builds up

100 ms

Static pressure stabilizes at 5.5 bar – 80 psi (gauge)


Max. static withstand limit pressure of transformer tanks : 1.2 bar – 17 psi (gauge)

(bar)

Transformer explodes





Simulation tool – 200 MVA transformer – with TP t = 0 ms

without without TPTP


SKIP

5/ TP References

11 MJ electrical arc Pressure (gauge) (psi)

(bar)

with TP with TP





Simulation tool – 200 MVA transformer – with TP t = 1 ms




(bar)

1 ms

with TP with TP






Simulation tool – 200 MVA transformer – with TP t= 2 3 ms 4




(bar)

1 ms


4 ms The first dynamic pressure peak propagates

with TP with TP





Simulation tool – 200 MVA transformer – with TP t =10 8 7 6 5 ms 9 ms




(bar)

1 ms



with TP with TP

10 ms The dynamic pressure peak activates the TP





Simulation tool – 200 MVA transformer – with TP t =15 13 14 ms 11 12




(bar)

1 ms



with TP with TP


15 ms

Rarefaction waves are spread in the tank





Simulation tool – 200 MVA transformer – with TP t =20 19 24 17 22 16 ms 18 25 30




(bar)

1 ms



with TP with TP


15 ms


30 ms

The tank depressurizes





Simulation tool – 200 MVA transformer – with TP t =60 45 40 35 ms 50




(bar)

1 ms



with TP with TP


15 ms


30 ms


60 ms

The tank is fully depressurized





Simulation tool – 200 MVA transformer – with TP t = 80 70 ms 100 150 ms




(bar)

1 ms



with TP with TP


15 ms


30 ms


60 ms

The tank is fully depressurized

After 60 ms

• without TP, static press. = 5.5 bar – 80 psi • with TP, static pressure = atm. pressure





Simulation tool – Real case study – 400 MVA transformer


SKIP

Application 2: Real case study – 400 MVA Transformer Explosion Dimensions: 7.8 m x 3.2 m x 4 m 26 ft x 10 ft x 13 ft

Electrical Fault : 80kA, 110ms, 11 MJ

Two plates on bushing turrets exploded

The first one was ejected 30 meters – 100 feet away !

What is the result of the simulations ? TRANSFORMER PROTECTOR

5/ TP References




Simulation tool – Real case study – 400 MVA transformer

without TP


with TP

after 120 ms Pressure (gauge) (psi)

(bar)

after 120 ms

after 120 ms

• Without TP, the max. pressure is 14 bar – 200 psi and the static pressure builds up at around 7 bar – 100 psi.

• With TP, the first dynamic pressure peak activated the TP within milliseconds before static pressure is built up.

the tank is safe

the tank explodes TRANSFORMER PROTECTOR




Tank reinforcement


Computation of the tank thickness using ASME standards (Extract from “Prevention of transformer tank explosion, Part 3: Design of efficient protections using simulations ”, ASME PVP Conference Proceedings, 2009, available on request)

• ASME (American Society of Mechanical Engineers) establishes tank design rules. • On the previous examples, simulations show static overpressure stabilizes around 7 bar – 100 psi gauge (10 times more than usual static overpressure limit).

• ASME Standard gives the minimum thickness of a tank t to withstand an internal overpressure P i : P i R t 2 SE j 0.2 P i

= k P i

Negligible for transformer structures

S : Maximum allowable stress value R : radius of the shell E j : Efficiency of the joints

Linear relation between the min. thickness and the internal overpressure

To withstand overpressures generated by an electrical arc, tanks should be 10 times thicker than usual ! TRANSFORMER PROTECTOR




Tank reinforcement


Computation of the tank thickness using ASME standards (Extract from “Prevention of transformer tank explosion, Part 3: Design of efficient protections using simulations ”, ASME PVP Conference Proceedings, 2009, available on request)

• ASME (American Society of Mechanical Engineers) establishes tank design rules. • On the previous examples, simulations show static overpressure stabilizes around 7 bar – 100 psi gauge (10 times more than usual static overpressure limit).

• ASME Standard gives the minimum thickness of a tank t to withstand an internal overpressure P i : P i R t 2 SE j 0.2 P i

= k P i

Negligible for transformer structures

S : Maximum allowable stress value R : radius of the shell E j : Efficiency of the joints

Linear relation between the min. thickness and the internal overpressure

Trying to reinforce the tank structure is therefore irrelevant TRANSFORMER PROTECTOR


4. TP Technical Description


4.

TP Technical Description

•


•

Detailed TP components description

•

Other TP configurations

•

Retrofitting

•

TP options

•

TP order process


4. TP Technical Description TP standard configuration

Standard TRANSFORMER PROTECTOR (TP)



4. TP Technical Description TP Principle

Reminder of the TP Principle

2/ TP principle 3/ Physical explanations 4/ Technical description

SKIP

5/ TP References


4. TP Technical Description TP Principle • Electrical arc • Pressurized gas bubble • Dynamic pressure peak propagation




1

TP Activation

Quick oil evacuation generating fast depressurization of the tank (within milliseconds)




1

TP Activation





1

TP Activation


2





4. TP Techni Technical cal Descriptio Description n TP Principle • Electrical arc • Pressurized gas bubble • Dynamic pressure peak propagation

1

TP Activation


2



Transformer safe and ready for repair



4. TP Techni Technical cal Descriptio Description n




Standard TRA TRANSF NSFOR ORME MER R PR PRO OTE TECT CTOR OR (TP (TP)) The Components TP Components

3 1 2

4 5

1. Vertical Depressurization Set (VDS) 2. OLTC Depressurization Set (OLTC DS) 3. Slice Oil-Gas Separation Tank Tank (SOGST) 4. Explosive Gases Evacuation Pipe (EGEP) 6

5. Air Isolation Shutter 6. TP Cabinet

7

7. Inert Gas Injection Pipe (IGIP)




Standard TP components: Vertical Depressurization Set (VDS)


SKIP

5/ TP References

Standard TRA TRANSF NSFOR ORME MER R PR PRO OTE TECT CTOR OR (TP (TP)) TP Components 1. Vertical Depressurization Set (VDS)






Vertical Depressurization Set (VDS) Principle Principle • to relieve overpressure and to favor high-speed depressurization

• diameter is calculated individually for each transformer types

• includes an Isolation Valve (IV), a Shock Absorber (SA) and a Vibration Absorber (VA)






Vertical Depressurization Set (VDS) Elements Elements 8

1.

Transformer Interface (TI)

2.

Isolation Valve (IV)

3.

Shock Absorber (SA)

4.

Rupture Disk (RD)

5.

Vibration Absorber (VA)

6.

Decompression Chamber (DC)

7.

Oil Outlet

8.

Gases Outlet

6

5

7

4 3 2 1




Standard TP components: OLTC Depressurization Set (OLTC DS)



TheComponents Components TP 1.

Vertical Depressurization Set (VDS)

2.

OLTC Depressurization Set (OLTC DS)




Standard TP components: OLTC Depressurization Set (OLTC DS)


OLTC Depressurization Set (OLTC DS) 3

2

Elements

1

1.

Rupture Disk with integrated Burst Indicator (RD BI)

2.


3.

Explosive Gas Elimination Pipe (EGEP)




Standard TP components: Slice Oil-Gas Separation Tank (SOGST)



The Components TP Components 1.

Vertical Depressurization Set (VDS)

2.

OLTC Depressurization Set (OLTC DS)

3.

Slice Oil-Gas Separation Tank (SOGST)






Slice Oil-Gas Separation Tank (SOGST)

Principle Principle • The OGST collects the depressurized oil and flammable gas mixture

• Then, the OGST separates gases from oil and the gases are channeled away to a remote area






Slice Oil-Gas Separation Tank (SOGST) 6

1

4

2

5 3

Elements Elements 1. 2. 3.

Main Conservator Compartment connected to Transformer Tank Conservator Pipe to Buchholtz Relay and Transformer Tank Partition Barrier

4. 5. 6.

Slice OGST (SOGST) Oil Drain Pipe (ODP) connection flange from 6 inch to 12 inch Explosive Gas Evacuation Pipe (EGEP) connections 2 inch




Standard TP components: Explosive Gas Elimination Set (EGES)



TheComponents Components TP 1.

Vertical Depressurization Set

2.

OLTC Depressurization Set

3.

Slice Oil - Gas Separation Tank

4.

Explosive Gases Evacuation Pipe (EGEP)

5.

TP Cabinet

6.

Inert Gas Injection Pipes (IGIP)




Standard TP components: Explosive Gas Elimination Set (EGES)


Explosive Gas Elimination Set: the TP Cabinet 4

5

Elements Elements

SERGI

2

3 7

1. 2. 3. 4.

1

6

Inert Gas Cylinder (IGC) Manometer Pressure Reducer (PR) Pipe to transformer main tank 5. Pipe to OLTC 6. Cabinet Heater (CH) 7. In / out of service and maintenance lights




Standard TP components: Control Box (CB)


Conventional Control Box (CCB) Principle • located in the Control Room • ensures the logic of the system • connected to Linear Heat Detectors (LHD), Isolation Valve (IV), Rupture Disk Burst Indicators (RD BI) and to TP Cabinet

• other Control Box (CB) designs are available on request




4.


•


•


•


•

Retrofitting

•

TP options

•

TP chain value



3/ Physical explanations

Other TP configurations: Horizontal Depressurization Set (HDS)


When the Vertical Depressurization Set (VDS) can not be installed, for example because of electrical HV clearances, the Horizontal Depressurization Set (HDS) is proposed

1

3

4

HDS Elements 1 5

1.

Isolation Valve Flange (IVF)

2.

Isolation Valve (IV)

3.

Shock Absorber (SA)

4.

Rupture Disk (RD)

5.


6.

Support Plate (SP)

7.

Vibration Absorber (VA)

2

6

7




Other TP configurations: Wall & Elevated OGST

2


When the conservator cannot be shared, the following OGST configurations are proposed

a) with Vertical Depressurization Set (VDS) Wall Oil Gas Separation Tank – WOGST

Elevated Oil Gas Separation Tank – EOGST




Other TP configurations: Wall & Elevated OGST

2


When the conservator cannot be shared, the following OGST configurations are proposed

b) with Horizontal Depressurization Set (HDS) Wall Oil Gas Separation Tank – WOGST

Elevated Oil Gas Separation Tank – EOGST


4. TP Technical Description Standard Configuration


Reminder: Standard Configuration

3

when no specific constraints

Vertical Depressurization Set (VDS) & Slice OGST (SOGST)




4.


•


•


•


•

Retrofitting

•

TP options

•

TP chain value


4. TP Technical Description Retrofitting on existing transformers


SKIP

5/ TP References

Retrofitting on existing transformers The TRANSFORMER PROTECTOR is easily retrofitted without tank machining by using the existing interfaces

1. Depressurization Set: Cover and Side Manholes, Pressure Relief Valves and Existing Valves can be used for the adaptation




SKIP

5/ TP References


1. Depressurization Set: Cover and Side Manholes, Pressure Relief Valves and Existing Valves can be used for the adaptation Examples:






2. Inert Gas Injection: Existing Valves for oil sampling and draining can be used to retrofit the inert gas injection






2. Inert Gas Injection: Existing Valves for oil sampling and draining can be used to retrofit the inert gas injection Example:




4.


•


•


•

Other TP configuration

•

Retrofitting

•

TP options

•

TP chain value




TP Options •

Option A: OLTC protection

•

Option B: OCB protection




TP Options: OLTC protection

SKIP

5/ TP References

Option A : On Load Tap Changers Protection Elements 3

2

1.

Rupture Disk with integrated Burst Indicator (RDBI)

2.


3.

Explosive Gas Elimination Pipe (EGEP)

Example 1


4. TP Technical Description TP Options: OLTC protection


SKIP

5/ TP References

Option A : On Load Tap Changers Protection The OLTC protection can be proposed with an Isolation Valve (IV) as well:

Decompression Chamber (DC) IV Limit Switches

Rupture Disk with integrated Burst Indicator (RDBI) Isolation Valve (IV)




TP Options: OCB protection

5/ TP References

Option B : Oil Cable Boxes Protection Example :

Isolation Valve (IV) Oil Collecting Pipe

Rupture Disk with integrated Burst Indicator (RDBI) Inert Gas Injection Pipe (IGIP)




4.


•


•


•

Other TP configuration

•

Retrofitting

•

TP options

•

TP order process




TP order process

5/ TP References

TP Pro ject Research & TP Project Project Development Definition

Production

Tests

TP In s tallatio n TP Supervised Inst allation Erection

Supervised Tests

Commissioning

TP Guarantee and Maintenanc e TP Guaran tee and Guarantee Maintenance

Maintenance

Packaging Transport




TP Project

5/ TP References

TP Projec t 

TP Components Selection



Factory Tests



Engineering Drawings



Components Preliminary Tests



Quantity Certificates



TP Logic

Research & Development

Project Definition

Production



Customization





Numerical Simulation Validation

 Assemblies 

Manufacturing Methods

Tests

Packaging Transport



Specific Packaging



Site Delivery




TP Installation

5/ TP References

TP In st allatio n End of Installation Certificate (EIC) signed by SERGI

Supervised Installation & Tests

 Accredited

Supervisor

or 

SERGI Project Engineer

Installation Acceptation



On-Site Test Certificate (OTC) signed by SERGI

Commissioning

SERGI Project Engineer

included in the TP price




Guarantee & Maintenance

5/ TP References

TP Guarantee and Maint enanc e When the End of Installation Installation Certificates Certificates and the On Site Test Certificate are signed by the SERGI Project Engineer:  12 months guarantee  Liability insurance for TP life  up to 3 Millions Euros per event

Guarantee

Maintenance

 The TP is a passive mechanical system

(no electric actuator)  Limited and low cost maintenance  SERGI has dedicated team for maintenance follow up


5. Refe Refere rence ncess


5.

References

•

Financial benefit

•

World reference / sold TP

•

Valorization & certification organisms

•

Successful activations

•

Installation examples



5. References


Financial benefit


The TP Financial Benefit is very high  The Protection Financial Benefit (PFB) is calculated as :

PFB = CTC / (MLEB – LEA)

Extract from “ Transformer Explosion and Fire Incidents, Guideline for Damage Cost Evaluation, Transformer Protector Financial Benefit” Available on request

To Complete) : complete price of the protection (including erection and tests) • CTC (Cost To • MLEB (Maximum Loss Expectancy Ex pectancy Before): Before): cost of the worst recorded incident before installing a protection

• LEA (Loss Expectancy After): evaluation of the damage cost of the worst recorded incident with the chose protection after installation

corporate risk managers and insurance, if:  For corporate • PFB < 1 %, the protective technology is highly recommended • 1% < PFB < 4%, insurance companies adjust their rates and premiums  Analyses showed that the TP Financial Benefit varies from 0.015 % to 0.06 % !

When an incident occurs, the TP compensates several thousand times the inves investment tment TRANSFORMER PROTECTOR


5. References


Sold TP


More than 1.400 TP sold since 2000

Every kind of oil-filled transformers (above 1 MVA) Generation

Transmission


Distribution


5. References


End users


More than 106 companies in 53 countries:



5. References


NFPA


The NFPA recommends the TP • Standard NFPA 850 (Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations) • Standard NFPA 851 (Recommended Practice for Fire Protection for Hydroelectric Generating Plants)

In the introduction of NFPA 850 and 851:



5. References


NFPA



Definition of “fast depressurization system” by the NFPA:



5. References


NFPA



Explanation of the operation by the NFPA:


Documents available on request


5. References


NFPA


The NFPA recommends the TP • The TP is also mentioned in the NFPA Fire Handbook 2002 & 2008



5. References


Valorization or certification organisms


 ISO 9001 Certification

 FM Global : Certification under progress

 EDF (Electricité de France) and CEPEL (Brazil)

laboratories TP tests validation  Active participation in the Power Transformer

Subcommittee (tank rupture mitigation taskforce)  Various IEEE Conferences  Active participation in the A2 Study Committee –

Transformers (transformer fire safety practices WG)  Various Cigré Conferences TRANSFORMER PROTECTOR


5. References


Successful activations


The TP saved transformers, successful activation certificates from: •

Romania (TransElectrica),

•

Philippines (Transco),

•

Botswana (Botswana Power Corporation),

• Activation in Pakistan, Mexico (3) and Romania under process



5. References




SKIP

5/ TP References

Installation on new transformers  Qatar, Al Jumaliah, Al Waab, Alkor Jonction…, transmission substations  Brazil, Assis Substation, São Paulo  Australia, Mount Piper, Coal Power Plant, Delta Electricity

Retrofitting on existing transformers  France, Randens Hydro Power Plant, Electricité de France  Namibia, Van Eck Substation, NamPower



5. References




Qatar, transmission substation, ~ 80 transformers (20 to 315 MVA) Installation:



5. References




Qatar, transmission substation, ~ 80 transformers (20 to 315 MVA) Main tank Depressurization Set:



5. References




Qatar, transmission substation, ~ 80 transformers (20 to 315 MVA) On Load Tap Changers Protection:



5. References




Qatar, transmission substation, ~ 80 transformers (20 to 315 MVA) Oil Cable Boxes Protection:



5. References




Qatar, transmission substation, ~ 80 transformers (20 to 315 MVA) Inert gas injection:



5. References




Qatar, transmission substation, ~ 80 transformers (20 to 315 MVA) TP Cabinet:



5. References




Qatar, transmission substation, ~ 80 transformers (20 to 315 MVA) Control Boxes in the control room (for 11 transformers)



5. References




Brazil – Assis Substation – São Paulo Overview



5. References




Brazil – Assis Substation – São Paulo DS for the main tank

OLTC Protection


TP Cabinet


5. References




Australia – New South Wales Coal Power Plant – Delta Electricity Overview of the power plant



5. References




Australia – New South Wales Coal Power Plant – Delta Electricity

Installation of the TRANSFORMER PROTECTOR



5. References




France – Randens Hydro Power Plant – Electricité de France  Complex

situation in a tiny cave



5. References




France – Randens Hydro Power Plant – Electricité de France  Technical

proposal



5. References




France – Randens Hydro Power Plant – Electricité de France  Installation



5. References




Namibia – Van Eck Substation – NamPower Vertical DS for the main tank and 3 OLTC protection



5. References




Namibia – Van Eck Substation – NamPower Vertical DS for the main tank


3 OLTC protections


Conclusion


1. Power transformers are very dangerous • Explosions are more and more frequent • Dangerous, expensive, polluting, hurt reputation… • Conventional corrective means do not prevent explosion (fire extinguishing systems, firewalls) • Conventional preventive means are not efficient (circuit breakers, buchholz, PRV...)

2. The TRANSFORMER PROTECTOR prevents the explosion • Principle: No Actuator ! The TP is activated by the first dynamic pressure peak generated by the arc, avoiding the explosion by preventing static pressure increase • Efficiency demonstrated by experimental tests & numerical simulations

3. The TP is a recommended solution • The NFPA recommends the TP • Several successful activations • More than thousand TP sold all over the world (USA, Europe, Middle East…) TRANSFORMER PROTECTOR

Transformer Protector

Recommend Documents