transformer protector

During a transformer short circuit, the TRANSFORMER PROTECTOR is activated within milliseconds by the first

dynamic pressure of the shock wave, avoiding transformer explosions before static pressure increase

TRANSFORMER PROTECTOR

The Only Solution Against Transformer Explosion

www.sergi-france.com

TRANSFORMER PROTECTOR Presentation



1/ Transformers explosions

2/ TP principle

3/ Physical explanations

4/ Technical description

5/ TP References

Ref: FtTPgaac31e 2

NFPA

The TRANSFORMER PROTECTOR is now recommended for all Power Plants and Substations in the National Fire Protection Association 2010 edition of:

• NFPA 850 (Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations),

• NFPA 851 (Recommended Practice for Fire Protection for Hydroelectric Generating Plants).

The introduction of the 2010 edition of NFPA 850 & NFPA 851 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 designed to depressurizethe transformer a few milliseconds after the occurrence of an electrical fault”

More details later in the presentation or

Just click here




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

• Why do transformers explode ? • TP strategy

• Examples of explosions • Conventional protections • The answer

• Experimental tests• Physical phenomena

• Standard configuration• The TP components

• NFPA, FM Global, IEEE…• World references

3

Overview of the presentation

2. The TP principle to prevent transformer explosion

3. Physical explanations

4. TP technical description

5. References

• Retrofitting• TP order process

• Successful activations• Examples of installations

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

• Other configurations• TP options

• Detailed TP operation

1. Transformers are very dangerous

Conclusion




2/ TP principle



5/ TP References

Ref: FtTPgaac31e






4





5. References







Conclusion

From this “overview” page, you can navigate through the complete presentation by clicking

on the item you want to see

Click here if you want to see the “detailed TP operation”

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




2/ TP principle



5/ TP References

Ref: FtTPgaac31e






5





5. References







Conclusion




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 6


• Examples of explosions

• Conventional protections

• The answer





2/ TP principle



5/ TP References

Ref: FtTPgaac31e 7

Danger :

• 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.

Power transformers are very dangerous

Transformer explosion in a power plant

• Large quantity of oil in contact with high voltage elements

• No international security norm for transformers

1. Transformers are very dangerousExamples of explosions

Videos/Gas Bubble In Brazil.avi




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 8

Ottawa Hydro, Canada, March 2009

transformer burned during hours

Other explosion examplesTransformer explosions lead to: 2

• Huge fire

• Plant outage

• Huge costs :

hundreds millions Euros

• Ruin company reputation

• Environmental pollution

• Human life risks

1. Transformers are very dangerous Examples of explosions




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 9

Other explosion examples

Krümmel Nuclear Power Plant, Germany

June 2007, still not restarted !

Cost: 1 Million Euros / day !

3Transformer explosions lead to:

• Huge fire

• Plant outage

• Huge costs :









2/ TP principle



5/ TP References

Ref: FtTPgaac31e 10

Blénod Coal Power Plant, EDF, France

May 2009

Other explosion examples 4


Transformer explosions lead to:

• Huge fire

• Plant outage

• Huge costs :








2/ TP principle



5/ TP References

Ref: FtTPgaac31e 11

1. Transformers are very dangerous Conventional protections

a) South Band, Illinois , USA, 1999

Efficiency ?Corrective Means

• Firewalls • Fire extinguishing systems

Limit fire propagation

induced by the explosion Fire propagated from one transformer to the other

1




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 12


b) Venice Plant, Illinois , USA, 2000

Efficiency ?Corrective Means

Solution : Preventing transformer explosion to avoid fire

• Firewalls • Fire extinguishing systems

Limit fire propagation

induced by the explosion

Fire propagated to the whole plant: All 9 transformers caught fire despite

fire walls and fire extinguishing systems (cost: USD 230 millions)

1




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 13


All explodedtransformers

were equippedwith these

devices

Efficiency ?Preventive Means

• Circuit breakers

• Buchholz Relay

• Sudden Pressure Relay

• Gas Monitoring

• Pressure Relieve Valve

Solution : The protection must act faster !

2




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 14

1. Transformers are very dangerous The answer

During a short circuit, the TP isactivated within milliseconds bythe first dynamic pressure peak ofthe shock wave, avoidingexplosions by preventing staticpressure increase.

The TP key of success

The TRANSFORMER PROTECTOR (TP)

The TP depressurizes transformers within milliseconds avoiding explosion and subsequent fire.




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 15

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




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 16

Why do transformers explode ?

Dielectric oil insulation rupture

Electrical arc

Oil vaporization

Local dynamic pressure increase

First dynamic pressure peak propagates

Dynamic pressure peak reflects off walls

Static pressure increases

Tank rupture & Fire

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




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 17

How to break that sequence?


Electrical arc

Oil vaporization




Static pressure increases

Tank rupture & Fire

2. Preventing transformer explosion: the TP principle Prevention strategy




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 18

Activation within milliseconds by the first dynamic pressure peak

Quick Oil Evacuation

Tank depressurization

Prevents the explosion

How to break that sequence?


Electrical arc

Oil vaporization




2. Preventing transformer explosion: the TP principle Prevention strategy




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 19

2. Preventing transformer explosion: the TP principle TP operation




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 20


• Electrical arc

• Pressurized gas bubble

• Dynamic pressure peak propagation




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 21


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

TP Activation1

• Electrical arc






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 22


• Explosive gases remain

• Melting parts of the windings arestill emitting gases


TP Activation1

• Electrical arc






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 23


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

Injection of Inert Gas2


TP Activation1



• Electrical arc






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 24


Transformer safe and ready for repair


TP Activation1





• Electrical arc






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 25

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

Standard TRANSFORMER PROTECTOR (TP)

6

2

14

1. Vertical Depressurization Set (VDS)

2. OLTC Depressurization Set (OLTC DS)

3. Slice Oil-Gas Separation Tank (SOGST)

4. Explosive Gases Evacuation Pipe (EGEP)

5. Air Isolation Shutter

6. TP Cabinet

7. Inert Gas Injection Pipe (IGIP)

The ComponentsTP Components

7

3

5




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 26

• 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

3. Physical Explanations





2/ TP principle



5/ TP References

Ref: FtTPgaac31e 27

3. Physical Explanations Experimental tests: general overview

• 2002: 28 tests by EDF (Electricitéde France) on small transformers

Two main test campaigns




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 28



• 2004: 34 tests by CEPEL (HVindependent lab.) on largetransformers (8.4m – 26ft)





2/ TP principle



5/ TP References

Ref: FtTPgaac31e 29



Conclusion

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


• 2004: 34 tests by CEPEL (HVindependent lab.) on largetransformers (8.4m – 26ft)

• Principle: electrical arcs wereignited inside transformers tanksequipped with a TP

Click on pictures to watch videos

Videos/StTPgae011 - 28_T1A_140_83_VAC_Cep.avi

Videos/StTPgae010 - 14_T3C_75_83_ATM.m1v




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 30



Oil vaporization & gas creation




TP reaction to the physical phenomena

• Simulations:




• Tank reinforcements influence using ASME standards






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 31

3. Physical Explanations Vaporization saturation process

SKIP

1st key phenomena: oil vaporization & arc creation – video1

Arc movie during the EDF testsHigh speed camera 3000 fps

Chronology

0 ms : Start of applied current

3.66 ms : Bubble generation

4 ms : Bubble volume = 9 cm3, 0.5 in.3

4.33 ms : Bubble volume = 60 cm3, 3.7 in.3






6.33 ms : Electrical arc fully developed - plasma




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 32

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

SKIP

1st key phenomena: oil vaporization & arc creation – video1

Electrical Arc Produced Gas

Plasma Mineral Oil




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 33


1

VaporizationHeat transfer to the oil

(Joule effect)

Gas bubble – oil vapor

Cracking oil vapor into smaller molecules

Electrical arc fully developed – Plasma

Gas bubble gases with low resistivity

Short circuit Electrical current between 2 points

of the transformer

Less resistivity = more current

Transformer Oil

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




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 34


SKIP

1

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!

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

Videos/Gas Bubble In Brazil.avi




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

1st step:

Arc in contact with oil

Enormous Vaporization

b) Measurements

Transformer Oil

• When the arc occurs, direct contact between arc and liquid oil

• High energy exchange to liquid oil

Fast & huge vaporization

35

HEAT EXCHANGEARC TO OIL




1

c) Physical explanation: 1st step

Arc Energy (in MJ)

1st step: the 1st Mega Joule produces 2.3 m3 – 81 ft3 of explosive gas

Gen

erat

ed G

as V

olu

me

(in

m3)

Gas





2/ TP principle



5/ TP References

Ref: FtTPgaac31e

b) Measurements

• 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

36


1

c) Physical explanation: 2nd step

1st step: the 1st Mega Joule produces 2.3 m3 – 81 ft3 of explosive gas

Arc Energy (in MJ)

2nd step: the following 19 MJ produce only 1.2 m3 – 42 ft3 of gas

3) CREATION OF PLASMA

1) HEATING THE

GAS

Transformer OilGen

erat

ed G

as V

olu

me

(in

m3)

Gas

2) IONISATION





2/ TP principle



5/ TP References

Ref: FtTPgaac31e

b) Measurements

37


1

Arc Energy (in MJ)Gen

erat

ed G

as V

olu

me

(in

m3)

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

Vaporisation Saturation

Transformer Oil

Gas

c) Physical explanation: 2nd step

3) CREATION OF PLASMA

1) HEATING THE

GAS

2) IONISATION





2/ TP principle



5/ TP References

Ref: FtTPgaac31e 38

3. Physical Explanations Pressure increase in the gas bubble

2nd key phenomena: quick pressure increase in gas bubble

1

2

Transformer Oil

Gas density is ~1000 times less than liquid density

The gas bubble wants to expend

But liquid oil inertia avoids the bubble expansion

Fast pressure increase in the gas bubble

(up to 5000 bar/s – 75000 psi/s)

1st key phenomena: oil vaporization & arc creation




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Maximum pressure peak amplitude recorded for each test (gauge pressure):

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

39


1st key phenomena: oil vaporization & arc creation1

2

+9 bar (130 psi)

1 MJ

+3 bar (40 psi)

1 MJ

+13 bar (190 psi)

2.5 MJ

+10.5 bar (150 psi)

125 kJ





2/ TP principle



5/ TP References

Ref: FtTPgaac31e 40



2

• 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!





2/ TP principle



5/ TP References

Ref: FtTPgaac31e 41

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


3rd key phenomena: the dynamic pressure peak propagates3

2

Transformer

Oil

3. Physical Explanations Dynamic pressure propagation




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 42

3. Physical Explanations Dynamic pressure propagation

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

Dynamic

Pressure

Close to the arc (C)

At the tank cover (B)

Close to the TP (A)

A

B

C

TP


arc




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 43

3. Physical Explanations Tank withstand to dynamic pressure




2

4th key phenomena: tank can withstand high dynamic pressure peaks4




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 44


Maximum dynamic pressure peak amplitude recorded for each test (gauge pressure):

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


+13 bar (190 psi)

+10.5 bar (150 psi)

+11 bar (160 psi)

No Rupture !




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Dynamic Pressure

• Very localized and moving in the tank

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

45



Physical explanation:

No rupture induced by dynamic pressure!

Tank withstand capabilities

• Tank welding and bolts have a longinertia to break

• Dynamic pressure peak is travelingvery fast: welding and bolts haveno time to integrate the pressure.




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 46

3. Physical Explanations Tank ruptures due to static pressure




2


5th key phenomena: tanks rupture because of static pressure5




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 47

3. Physical Explanations Tank ruptures due to static pressure

Tanks rupture because of static pressure

5th key phenomena: tanks rupture because of static pressure5

• 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).

pressure gradients less than 25 bar/s – 350 psi/s




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 48

3. Physical ExplanationsDynamic / static pressure

• Spatially uniform all over the tank

• Progressive, slow increase

• Oil behaves as an incompressible media

• Max withstand ~1 bar – 15 psi (gauge)

• Very localized and moving in the tank

• Propagates quickly within the tank

• Oil behaves as a compressible media

• Tank can resist 13 bar – 190 psi (gauge)

The tank does not explode The tank explodes

Dynamic PressurePressure gradients over 25 bar/s – 360 psi/s

Static PressurePressure gradients under 25 bar/s – 360 psi/s

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

Propagation speed: 1200 m/s – 4000 ft/s




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 49

3. Physical Explanations Dynamic / static pressure

How does Dynamic Pressure become Static Pressure ?

The dynamic pressure peak travels and reflects off

the walls, creates secondary peaks building slowly

static pressure.




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 50



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.




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 51



Evolution of the pressure at different sensors in the tank:

TP Strategy

To prevent Dynamic Pressure from becoming Static Pressure

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




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 52

3. Physical Explanations Influence of the TP




2


5th key phenomena: tank ruptures because of static pressure5

6th key phenomena: the TP depressurizes tanks preventing explosion6




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 53



Depressurization SetTraveling distance : 8,5 m – 26 ft

Electrical Arc at the opposite side of the TP

Windings

Dynamic pressure sensor located close to the TP

Videos/1 .avi




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 54


The TP is activated in 8 ms,

time for the dynamic

pressure peak generated by

the arc to reach the sensor:

8.5 m at 1200 m/s

(26 ft at 4000 ft/s)

Dynamic pressure recorded close to the depressurization set

8 ms

The TP depressurizes the tank in milliseconds, even if the arc is

fed for a longer period


58000 psi/s




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 55

The TP depressurizes the tank in milliseconds, even if the arc is

fed for a longer period


No static pressure

No tank rupture

Dynamic pressure recorded close to the depressurization set


58000 psi/s




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 56


a) No static pressure

The quick oil evacuation generates

rarefaction waves that

depressurizes the tank

before static pressure builds up. 0 ~10 ms

Arc occurrence

TP is activated

Tank is depressurized

~80 ms

Dyn. pressure travelling

Oil evacuation


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




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 57

Recapitulation of the main physical 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 peakpropagation

(up to 13 bar – 190 psi)

3. Physical Explanations TP key of success





2/ TP principle



5/ TP References

Ref: FtTPgaac31e 58

3. Physical Explanations TP key of success

During a short circuit, the TP is activated withinmilliseconds by the first dynamic pressure peakof the shock wave, avoiding explosions bypreventing static pressure increase.

TRANSFORMER PROTECTOR key of success


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





2/ TP principle



5/ TP References

Ref: FtTPgaac31e 59



Oil vaporization




TP reaction to the physical phenomena

• Simulations:




• Tank reinforcements influence using ASME standards






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 60

3. Physical Explanations 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 ? Explosion: too dangerous to test

What would happen in other configurations ? 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…)




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 61

0 mst =

11 MJ electrical arc

3. Physical Explanations Simulation tool – 200 MVA transformer – no protection

SKIP

Application 1: 200 MVA Transformer

(5.75m x 3.25m x 2.5m) – (19ft x 11ft x 8ft)

Pressure (gauge)

(psi) (bar)

without TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

1 ms

62

1 mst =Gas bubble under pressure



Pressure (gauge)

(psi) (bar)

without TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

4 ms

1 ms

63

3 ms2 ms4 mst =Gas bubble under pressure

The first dynamic pressure peak

propagates

3. Physical ExplanationsSimulation tool – 200 MVA transformer – no protection


Pressure (gauge)

(psi) (bar)

without TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

10 ms

4 ms

1 ms

64

5 ms6 ms7 ms8 ms9 mst =

Reflects off the walls and creates

complex pressure waves

Gas bubble under pressure


propagates

10 ms



Pressure (gauge)

(psi) (bar)

without TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

30 ms

10 ms

4 ms

1 ms

65

11 ms12 ms13 ms15 ms14 ms16 ms17 ms19 ms18 ms22 ms24 ms20 ms25 mst =

Dynamic pressure reach more than

9 bar – 130 psi (gauge) in a bushing





propagates

30 ms



Pressure (gauge)

(psi) (bar)

without TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

50 ms

30 ms

10 ms

4 ms

1 ms

66

38 ms35 ms40 ms45 mst =

Static pressure builds up








propagates

50 ms


without TP

Pressure (gauge)

(psi) (bar)




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

50 ms

30 ms

10 ms

4 ms

1 ms

100 ms

67

50 ms60 ms70 ms80 mst =

Static pressure builds up







propagates

Static pressure stabilizes at

5.5 bar – 80 psi (gauge)

100 ms

Transformer explodes



Max. static withstand limit pressure of

transformer tanks :

1.2 bar – 17 psi (gauge)

Pressure (gauge)

(psi) (bar)

without TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Pressure (gauge)

(psi) (bar)

68

0 mst =

without TP

SKIP

3. Physical Explanations Simulation tool – 200 MVA transformer – with TP

with TP

without TP

with TP





2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Pressure (gauge)

(psi) (bar)

69

1 mst =



1 ms Gas bubble under pressure

without TP

with TP

without TP

with TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Pressure (gauge)

(psi) (bar)

70

3 ms2 mst = 4 ms



1 ms

4 ms The first dynamic pressure peak propagates


without TP

with TP

without TP

with TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Pressure (gauge)

(psi) (bar)

71

5 ms6 ms7 ms8 ms9 mst =10 ms



1 ms

4 ms

10 ms The dynamic pressure peak activates the TP


The first dynamic pressure peak propagates

without TP

with TP

without TP

with TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Pressure (gauge)

(psi) (bar)

72

14 ms11 ms12 ms13 mst =15 ms



1 ms

4 ms

10 ms

15 ms Rarefaction waves are spread in the tank

The dynamic pressure peak activates the TP



without TP

with TP

without TP

with TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Pressure (gauge)

(psi) (bar)

73

16 ms17 ms19 ms18 ms22 ms24 mst =20 ms25 ms30 ms



1 ms

4 ms

10 ms

15 ms

30 ms The tank depressurizes

Rarefaction waves are spread in the tank




without TP

with TP

without TP

with TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Pressure (gauge)

(psi) (bar)

74

35 ms40 ms45 ms50 mst =60 ms

3. Physical ExplanationsSimulation tool – 200 MVA transformer – with TP


1 ms

4 ms

10 ms

15 ms

30 ms

60 ms The tank is fully depressurized

The tank depressurizes





without TP

with TP

without TP

with TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

1 ms

75

70 ms80 ms100 mst =

After 60 ms



150 ms

3. Physical ExplanationsSimulation tool – 200 MVA transformer – with TP

4 ms

10 ms The dynamic pressure peak activates the TP


15 ms

30 ms

60 ms

The tank depressurizes


The tank is fully depressurized

without TP

with TP

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

Pressure (gauge)

(psi) (bar)

• with TP, static pressure = atm. pressure

without TP

with TP




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 76

Application 2: Real case study – 400 MVA Transformer Explosion

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 ?

Dimensions: 7.8 m x 3.2 m x 4 m

26 ft x 10 ft x 13 ft

SKIP

3. Physical Explanations Simulation tool – Real case study – 400 MVA transformer




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

after 120 ms

77

3. Physical Explanations Simulation tool – Real case study – 400 MVA transformer

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

the tank explodes

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

the tank is safe

with TPwithout TP

Pressure (gauge)(psi) (bar)

after 120 ms after 120 ms




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 78

3. Physical Explanations Tank reinforcement

• 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 Pi :

ij

i

PSE

RPt

2.02

S : Maximum allowable stress value

R : radius of the shell

Ej : Efficiency of the jointsNegligible for transformer structures

Linear relation between the min. thickness and the internal overpressure

= k Pi

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)

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




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 79

3. Physical Explanations Tank reinforcement

• 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 Pi :

ij

i

PSE

RPt

2.02

S : Maximum allowable stress value

R : radius of the shell

Ej : Efficiency of the jointsNegligible for transformer structures

Linear relation between the min. thickness and the internal overpressure

= k Pi

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)

Trying to reinforce the tank structure is therefore irrelevant

TRANSFORMER PROTECTORThe Only Solution Against Transformer Explosion


2/ TP principle



5/ TP References

Ref: FtTPgaac31e 80


• Detailed TP components description

• Other TP configurations

• Retrofitting

• TP options

• TP order process

4. TP Technical Description




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 81

4. TP Technical Description TP standard configuration




2/ TP principle



5/ TP References

Ref: FtTPgaac31e 82

Reminder of the TP Principle

4. TP Technical Description TP Principle

SKIP



2/ TP principle



5/ TP References

Ref: FtTPgaac31e 83

• Electrical arc






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 84


TP Activation1

• Electrical arc






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 85




TP Activation1

• Electrical arc






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 86




TP Activation1



• Electrical arc






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 87

Transformer safe and ready for repair


TP Activation1





• Electrical arc






2/ TP principle



5/ TP References

Ref: FtTPgaac31e 88

4. TP Technical Description TP standard configuration


6

2

14





5. Air Isolation Shutter

6. TP Cabinet

7. Inert Gas Injection Pipe (IGIP)


7

3

5



2/ TP principle



5/ TP References

Ref: FtTPgaac31e

TP Components

89

4. TP Technical Description Standard TP components: Vertical Depressurization Set (VDS)

SKIP





2/ TP principle



5/ TP References

Ref: FtTPgaac31e 90


Vertical Depressurization Set (VDS)

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)

Principle



2/ TP principle



5/ TP References

Ref: FtTPgaac31e 91


Vertical Depressurization Set (VDS)

Elements

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

Elements

1

2

3

4

5

6

7

8



2/ TP principle



5/ TP References

Ref: FtTPgaac31e 92

4. TP Technical Description Standard TP components: OLTC Depressurization Set (OLTC DS)







2/ TP principle



5/ TP References

Ref: FtTPgaac31e 93

4. TP Technical Description Standard TP components: OLTC Depressurization Set (OLTC DS)

OLTC Depressurization Set (OLTC DS)

1

23

1. Rupture Disk with integrated Burst Indicator (RD BI)


3. Explosive Gas Elimination Pipe (EGEP)

Elements



2/ TP principle



5/ TP References

Ref: FtTPgaac31e 94

4. TP Technical Description Standard TP components: Slice Oil-Gas Separation Tank (SOGST)








2/ TP principle



5/ TP References

Ref: FtTPgaac31e 95


Slice Oil-Gas Separation Tank (SOGST)

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

Principle



2/ TP principle



5/ TP References

Ref: FtTPgaac31e 96

Slice Oil-Gas Separation Tank (SOGST)

14

6

253


Elements

1. Main Conservator Compartment connected to Transformer Tank

2. Conservator Pipe to BuchholtzRelay and Transformer Tank

3. Partition Barrier

4. Slice OGST (SOGST)5. Oil Drain Pipe (ODP) connection

flange from 6 inch to 12 inch6. Explosive Gas Evacuation Pipe

(EGEP) connections 2 inch

Elements



2/ TP principle



5/ TP References

Ref: FtTPgaac31e 97

4. TP Technical Description Standard TP components: Explosive Gas Elimination Set (EGES)



1. Vertical Depressurization Set

2. OLTC Depressurization Set

3. Slice Oil - Gas Separation Tank


5. TP Cabinet

6. Inert Gas Injection Pipes (IGIP)



2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Explosive Gas Elimination Set: the TP Cabinet

98

Elements

1. Inert Gas Cylinder (IGC)2. Manometer3. Pressure Reducer (PR)4. Pipe to transformer main

tank5. Pipe to OLTC6. Cabinet Heater (CH)7. In / out of service and

maintenance lights

2

4. TP Technical Description Standard TP components: Explosive Gas Elimination Set (EGES)

SERGI

1

3

7

Elements

4 5

6



2/ TP principle



5/ TP References

Ref: FtTPgaac31e 99

Conventional Control Box (CCB)

4. TP Technical Description Standard TP components: Control Box (CB)

• 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

Principle



2/ TP principle



5/ TP References

Ref: FtTPgaac31e 100




• Retrofitting

• TP options

• TP chain value





2/ TP principle



5/ TP References


4. TP Technical Description Other TP configurations: Horizontal Depressurization Set (HDS)

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

1

HDS Elements

1. Isolation Valve Flange (IVF)

2. Isolation Valve (IV)

3. Shock Absorber (SA)

4. Rupture Disk (RD)


6. Support Plate (SP)

7. Vibration Absorber (VA)

1

2

43

76

5



2/ TP principle



5/ TP References


4. TP Technical Description Other TP configurations: Wall & Elevated OGST

2When the conservator cannot be shared, the followingOGST configurations are proposed

Elevated Oil Gas Separation Tank – EOGSTWall Oil Gas Separation Tank – WOGST

a) with Vertical Depressurization Set (VDS)



2/ TP principle



5/ TP References


4. TP Technical Description Other TP configurations: Wall & Elevated OGST

2When the conservator cannot be shared, the followingOGST configurations are proposed

Elevated Oil Gas Separation Tank – EOGSTWall Oil Gas Separation Tank – WOGST

b) with Horizontal Depressurization Set (HDS)



2/ TP principle



5/ TP References


4. TP Technical Description Standard Configuration

3Reminder: Standard Configuration

when no specific constraints

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



2/ TP principle



5/ TP References





• Retrofitting

• TP options

• TP chain value





2/ TP principle



5/ TP References


4. TP Technical Description 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

Retrofitting on existing transformers



2/ TP principle



5/ TP References





SKIP


Examples:



2/ TP principle



5/ TP References

Ref: FtTPgaac31e


108




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



2/ TP principle



5/ TP References

Ref: FtTPgaac31e


109




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

Example:



2/ TP principle



5/ TP References




• Other TP configuration

• Retrofitting

• TP options

• TP chain value





2/ TP principle



5/ TP References


• Option A: OLTC protection

• Option B: OCB protection

TP Options




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Option A : On Load Tap Changers Protection

112

4. TP Technical Description TP Options: OLTC protection

1. Rupture Disk with integrated Burst Indicator (RDBI)


3. Explosive Gas Elimination Pipe (EGEP)

Elements

1

23

Example

SKIP



2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Option A : On Load Tap Changers Protection

113

4. TP Technical Description TP Options: OLTC protection SKIP

The OLTC protection can be proposed with an Isolation Valve (IV) as well:

Rupture Disk with integrated Burst Indicator (RDBI)

Isolation Valve (IV)

IV Limit Switches

Decompression Chamber (DC)



2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Option B : Oil Cable Boxes Protection

114

4. TP Technical Description TP Options: OCB protection

Rupture Disk with integrated Burst Indicator (RDBI)

Isolation Valve (IV)

Inert Gas Injection Pipe (IGIP)

Oil Collecting Pipe

Example :



2/ TP principle



5/ TP References




• Other TP configuration

• Retrofitting

• TP options

• TP order process





2/ TP principle



5/ TP References


4. TP Technical Description TP order process

TP Project

TP Installation

TP Guarantee and Maintenance

TP Project

TP Installation

TP Guarantee and

Maintenance Guarantee Maintenance

Supervised

Erection

Supervised

TestsCommissioning

Research &

Development

Project

DefinitionProduction Tests

Packaging

Transport



2/ TP principle



5/ TP References


4. TP Technical Description TP Project

Research &

Development

Project

DefinitionProduction Tests

Packaging

Transport

TP Components Selection

Engineering Drawings

Quantity Certificates

Customization

Numerical Simulation

Validation

Manufacturing

Assemblies

Methods

Factory Tests

Components Preliminary Tests

TP Logic

TP Project

Specific Packaging

Site Delivery



2/ TP principle



5/ TP References


4. TP Technical Description TP Installation

Supervised

Installation

& Tests

Accredited Supervisor

or

SERGI Project Engineer

TP Installation

SERGI Project Engineer

included in the TP price

On-Site Test Certificate (OTC) signed by SERGI

Installation

AcceptationCommissioning

End of Installation Certificate (EIC) signed by SERGI



2/ TP principle



5/ TP References


4. TP Technical Description Guarantee & Maintenance

When the End of Installation 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

TP Guarantee and Maintenance

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




2/ TP principle



5/ TP References


• Financial benefit

• World reference / sold TP

• Valorization & certification organisms

• Successful activations

• Installation examples

5. References

5. References




2/ TP principle



5/ TP References


5. References Financial benefit

The TP Financial Benefit is very high

The Protection Financial Benefit (PFB) is calculated as :

PFB = CTC / (MLEB – LEA)

For corporate risk managers and insurance, if:

• 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 investment

• CTC (Cost To Complete) : complete price of the protection (including erection and tests)

• MLEB (Maximum Loss Expectancy 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

Extract from “Transformer Explosion and Fire Incidents, Guideline for

Damage Cost Evaluation, Transformer Protector Financial Benefit”

Available on request




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Generation Transmission Distribution

122

5. References Sold TP

More than 1.400 TP sold since 2000

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




2/ TP principle



5/ TP References


5. References End users

More than 106 companies in 53 countries:




2/ TP principle



5/ TP References


5. References NFPA

• 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)

The NFPA recommends the TP

In the introduction of NFPA 850 and 851:




2/ TP principle



5/ TP References


5. References NFPA

Definition of “fast depressurization system” by the NFPA:







2/ TP principle



5/ TP References


5. References NFPA

Explanation of the operation by the NFPA:




Documents available on

request




2/ TP principle



5/ TP References


5. References NFPA

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





2/ TP principle



5/ TP References


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

5. References Valorization or certification organisms

ISO 9001 Certification




2/ TP principle



5/ TP References


5. References Successful activations

• Romania (TransElectrica),

• Philippines (Transco),

• Botswana (Botswana Power Corporation),

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

The TP saved transformers, successful activation certificates from:




2/ TP principle



5/ TP References

Ref: FtTPgaac31e

France, Randens Hydro Power Plant, Electricité de France

Namibia, Van Eck Substation, NamPower

130

5. References Installation examples

Qatar, Al Jumaliah, Al Waab, Alkor Jonction…, transmission substations

Brazil, Assis Substation, São Paulo

Australia, Mount Piper, Coal Power Plant, Delta Electricity

SKIP

Installation on new transformers





2/ TP principle



5/ TP References


Installation:


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




2/ TP principle



5/ TP References

Ref: FtTPgaac31e


132

Main tank Depressurization Set:





2/ TP principle



5/ TP References

Ref: FtTPgaac31e


133

On Load Tap Changers Protection:





2/ TP principle



5/ TP References

Ref: FtTPgaac31e


134

Oil Cable Boxes Protection:





2/ TP principle



5/ TP References

Ref: FtTPgaac31e


135

Inert gas injection:





2/ TP principle



5/ TP References

Ref: FtTPgaac31e


136

TP Cabinet:





2/ TP principle



5/ TP References

Ref: FtTPgaac31e


137

Control Boxes in the control room (for 11 transformers)





2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Brazil – Assis Substation – São Paulo

138

Overview





2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Brazil – Assis Substation – São Paulo

139

DS for the main tank OLTC Protection TP Cabinet





2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Australia – New South Wales Coal Power Plant – Delta Electricity

140

Overview of the power plant





2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Australia – New South Wales Coal Power Plant – Delta Electricity

141

Installation of the TRANSFORMER PROTECTOR





2/ TP principle



5/ TP References

Ref: FtTPgaac31e

France – Randens Hydro Power Plant – Electricité de France

142

Complex situation in a tiny cave





2/ TP principle



5/ TP References

Ref: FtTPgaac31e


143

Technical proposal





2/ TP principle



5/ TP References

Ref: FtTPgaac31e


144

Installation





2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Namibia – Van Eck Substation – NamPower

145

Vertical DS for the main tank and 3 OLTC protection





2/ TP principle



5/ TP References

Ref: FtTPgaac31e

Namibia – Van Eck Substation – NamPower

146

Vertical DS for the main tank 3 OLTC protections





2/ TP principle



5/ TP References


Conclusion

• The NFPA recommends the TP• Several successful activations• More than thousand TP sold all over the world (USA, Europe, Middle East…)

3. The TP is a recommended solution

• 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

2. The TRANSFORMER PROTECTOR prevents the explosion

• 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...)

1. Power transformers are very dangerous

During a transformer short circuit, the TRANSFORMER PROTECTOR is activated within milliseconds by the first

dynamic pressure of the shock wave, avoiding transformer explosions before static pressure increase



www.sergi-france.com

SERGI186 av. du Général de Gaulle – PO Box 90

78260 Achères – France

: 33 1 39 22 48 00

: 33 1 39 22 11 11

@ : [email protected]

web site : www.sergi-france.com