Thomas Fernandes

SERGI France – Smart Grid Middle East May 4th to 6t h 2009 Sergi Holding – Hanoi Electricity Conference – 5th December 2007 1/32

TRANSFORMER PROTECTOR

Thomas Thomas FernandesFernandes, Business Development Manager, Business Development Manager

SMART Grid Middle East SMART Grid Middle East -- Dubai UAE, May 4Dubai UAE, May 4th th to 6to 6thth, 2009, 2009

SERGI France, 186 av. du SERGI France, 186 av. du GGéénnééralral De Gaulle, 78260 De Gaulle, 78260 AchAchèèresres, France, Franceweb: web: www.sergiwww.sergi--france.comfrance.com, Office: (33) 1 39 22 48 71 , Fax: (33) 1 39 22 11 Office: (33) 1 39 22 48 71 , Fax: (33) 1 39 22 11 1111

TRANSFORMER PROTECTOR AN ANSWER TO PREVENT TRANSFORMER EXPLOSION

SERGI France – Smart Grid Middle East May 4th to 6t h 2009

OIL FILLED TRANSFORMER EXPLOSIONS

Danger : Large quantity of Oil in contact with high voltage elements

low impedance fault transformer explosion and fire

GOAL : Prevent such dramatic explosions Protection of Transformers


TRANSFORMER TANK RUPTURE PREVENTION

� TRANSFORMER PROTECTOR (TP) Principle

� Physical Phenomena

� TP Operation

� Technical & Financial Benefits

� TP References

� Installation Examples

PLAN OF THE PRESENTATION

SUMMARY


The Principle :During a short circuit, the TP is activated within milliseconds by

the first dynamic pressure peak of the shock wave, avoiding transformer explosion before static pressure increa ses.

THE TRANSFORMER EXPLOSION PREVENTION THE PRINCIPLE

Avoiding transformer explosions before static pressure increases.



Tank Rupture

Pressure Wave / Structure Interaction

Dielectric Oil Insulation Rupture

Electric Arc

Oil Vaporization

Pressure Wave Propagation

Local Pressure Increase


Tank Rupture Prevented

Tank Depressurization

Pressure Wave / Structure Interaction

Dielectric Oil Insulation Rupture

Electric Arc

Oil Vaporization

Pressure Wave Propagation

Local Pressure Increase




The different components of the TP:

1. Depressurization Set

2. OLTC Depressurization Set

3. Oil-Gas Separation Tank

4. Explosive Gas Elimination Pipe

5. Cabinet

6. Explosive Gases Evacuation

7. Conservator Shutter

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

5

62

4

7

31

THE TRANSFORMER EXPLOSION PREVENTION PRESENTATION


��

��

1/ The dynamic pressure peak travels at the speed of sound inside oil

2/ Ruptureof the disk,depressurisation,evacuation of the oil-gases mixture

4/ Nitrogen injectionN2

3/ Opening of the air isolation shutter��

5/ Explosive gasesproduction is stopped after 45 min

THE TRANSFORMER EXPLOSION PREVENTION OPERATION

TP Operation


Experimental Investigations

THE TRANSFORMER EXPLOSION PREVENTION


Experiments

• 62 tests (28 with EDF, 34 with Cepel)

• Physical phenomena were highlighted

• The TP prevented the transformer explosion each time.

Simulation Tool

• Compressible 2 phase flow 3D modeling

• The model is validated against experimental data

• The TP operation is validated for large transformers.

The TP is activated within milliseconds by the firs t dynamic pressure peak avoiding transformer explosio n.

The Transformer Protection was designed to prevent transformer explosion

EXPERIMENTAL INVESTIGATIONS EXPERIMENTS


34 Live Tests

• In the CEPEL Laboratory (Brazil)

• 3 transformer sizes :Max distance between arc and TP:– T1: 8.5 m– T2: 6.0 m– T3: 6.2 m


T2 TRANSFORMER

T1 TRANSFORMER T3 TRANSFORMER

OGST

DEPRESSURIZATION SET


• 3 arc positions : A – B – C

34 Live Tests





• Current range : 5 – 15 kA

• Time : 83 ms

• Arc Energy : up to 2.5 MJ

• 3 arc positions : A – B – C

34 Live Tests





EXPERIMENTAL INVESTIGATIONS TEST MOVIE

Movies of the TP Operation

Test number: 30Reference: 30_T1C_140_83_ATMArc: 14000 A during 83 msArc Location: Opposite the TP close to the bottom (pos. C)Transformer weight: 72 tonsCamera Speed: 25 frames/sec

Acceleration: 400 g

Test number: 28Reference: 28_T1A_140_83_ATMArc: 14800 A during 83 msArc Location: At the cover, in the TP vicinity (pos. A)Transformer weight: 72 tonsCamera Speed: 25 frames/sec

Acceleration: 400 g


TRANSFORMER EXPLOSION PREVENTION

Physical Phenomena Creation of an electrical arc


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 : The electrical arc ignites and creates t he first dynamic pressure peak of the shock wave

TRANSFORMER EXPLOSION PREVENTIONEXPERIMENTAL INVESTIGATIONS GAS GENERATION

ARC IGNITION, 2500 A, FILMED WITH A HIGH-SPEED CAME RA(3000 FPS)


EXPERIMENTAL INVESTIGATIONS GAS GENERATION

Test Number: 3

Test Reference: 2002

Arc Current: 2500 A

Arc Duration: 79 ms

Camera Speed: 3000 frames/second

• Gas bubbles appear on the arc path (1 to 2.3 m3 i.e. 35 to 80 ft3).

• Gas gets under pressure (from 100 bar/sec to 5,000 bar/sec i.e.14,500 psi/sec to 72,500 psi/sec)

• The dynamic pressure rises up to 14 bars (200 psi).

• Movie (EDF Tests):

The electrical arc creates a very violent physical phenomena with tank acceleration up to 800g, where g=9.81 m/sec² i. e. 30 ft/sec².



Progressively, vaporization is increasingly difficu lt because the arcis mostly surrounded by gas ⇒⇒⇒⇒ a logarithmic extrapolation

Geração de Gás X Energia do Arco

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0

0 10 20 30 40 50 60 70 80 90 100

Energia do Arco (MJ)

Vol

ume

de G

ás (

m3)

V - Gas Volume (m3)

E - Arc Energy (J)

Gas Generation versus Energy

Arc Energy (MJ)

Vol

ume

of G

as (

m3 )


TRANSFORMER EXPLOSION PREVENTION

Comparison Between Dynamic and Static Pressure


SIMULATION OF PRESSURE WAVE PROPAGATION

EXPERIMENTAL INVESTIGATIONS PRESSURE


HOW THE STATIC PRESSURE IS BUILT UP

Simulation of Test n.º 31 of CEPEL:

� Maximum Current, 34,5kA

� Maximum Voltage, 1034V

� Arc Energy, 460 kJoule

� Arc Duration, 83 milliseconds

� The tank withstands a maximum static pressure of 17 psi (1.2 bar) under atmospheric pressure

� For this test, pressure would stabilize at 88 psi (6 bar) above atmospheric pressure if not equipped with TP

The figure shows evolution of internal dynamic pressure inside of transformer tank if not protected by the TP



Test Number: 32

Arc Current: 14,000 A

Arc Duration: 83 ms

Arc Location: at the tank cover in the TP vicinity (A)

Under Atmospheric Pressure

Pressure Peak

109 psi (7.5 bar)

Pressure Gradient

56,550 psi/s

3,900 bar/s

PRESSURE VARIATION DURING TP OPERATION



Simulations without TPExperiments with TP

Test 31

D

Initial conditions: 450 kJ arc generating 1.9 m3 of gas

• Pressure reaches a static value higher than the static withstand limit

• Pressure remains at these levels for a long time.

The tank explodes when it is not equipped with a TP.



Computational Investigations

COMPUTATIONAL INVESTIGATIONS 400 MVA TRANSFORMER


10 INCHES RUPTURE DISK

150,000 ELEMENTS

Approximately 1 Liter / Element

TP CONFIGURATION



WITHOUT TRANFORMER PROTECTION

ELECTRICAL ARC, 80kA 110ms, 11MJ

GAS BUBBLE 3.3M3

P (bar) v (m/s)

Dimensions: 7.8m x 4m x 3.2m , Arc: 11 MJ



WITHOUT TRANFORMER PROTECTION

The max pressure is about 15 bars near a bushingThe static pressure stabilizes at around 8 bars after 500 ms

the transformer explodes.

P (bar) v (m/s)

T=2.5ms T=20ms T=50ms

T=120ms T=200ms



P (bar) v (m/s)

WITH TRANFORMER PROTECTION

Dimensions: 7.8m x 4m x 3.2m , Arc: 11 MJ, TP diame ter: 0.25m (10”)


DEPRESSURISATION SET

ELECTRICAL ARC, 80kA 110ms, 11MJ


WITH TRANFORMER PROTECTION

The TP depressurizes the transformer in 130 ms

P (bar) v (m/s)T=2.5ms T=20ms T=50ms

T=120ms T=200ms



With TP, far from the arcWith TP, close to the arc

COMPUTATIONAL INVESTIGATIONS COMPARISON

Comparison of the pressure distribution after 120 ms with and without TP

Without TP

P (bar)

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

the transformer is safe .

• Without TP , the max pressure is 15 bars and the static pressure builds up at around 8 bars the tank explodes.


Comparison between the TRANSFORMER PROTECTOR and the Pressure Relief Valve

EXPERIMENTAL INVESTIGATIONS PRESSU RE RELIEF VALVE


PRV AND TP COMPARISON TO STATIC AND DYNAMIC PRESSUR E

TRANSFORMER TANKS UNDER INTERNAL PRESSURE

� The TRANSFORMER PROTECTOR (TP) operates before tank wall inertia is overcome by the dynamic pressure and prevents tank rupture

� The PRV cannot respond to dynamic pressure because of:

- Spring inertia: 5 milliseconds

- The very small evacuation section

at the beginning of the opening:

15% when PRV 50% opened

- U turn for oil evacuation



Very transient phenomenon, rate of rise from 360 psi/s to 72,500 psi/s, 25 bar/s to

5,000 bar/s

Very strong moving forces that tank can withstand because of inertia to break

Dynamic Behavior


Pressure spatially non-uniform

Very high local dynamic overpressure < 200 psi, 14 bar

Local and moving mechanical stresses

PRV AND TP HAVE DIFFERENT OPERATING CHARACTERISTICS TO RESPOND TO DIFFERENT PHENOMENA

Uniform mechanical stresses

Static Behavior

PRESSURE RELIEF VALVE

Very slow phenomenon, rate of rise below 360 psi/s, 25 bar/s

Pressure spatially uniform

Low global static overpressure, < 14.5 psi, 1 bar

Strong forces applied on all walls leading to tank rupture



Video of Gas Bubble Escaping from the Transformer after Tank Rupture



� The gas bubble travels through the plant, up 2 sets of stairs , looking for oxygen and finds the door.

� There is so much energy that the door is blown off and is found 100 m away.

� The diameter of the gas bubble is approx. 4.9 ft (1.5 m) across. This translates to 62.4 ft3 (1.8 m3) of gas.

� According the energy vs. volume curve, this volume corresponds to an electrical arc energy of 0.8 MJ.

� This is a very small short circuit.


VIDEO OF GAS BUBBLE AFTER TANK RUPTURE

� The following video shows the gas bubble that is created when there is an electrical arc in the transformer .

� Because the transformer was not protected by a TRANSFORMER PROTECTOR, the tank ruptured and the gas escapes.

� Around the edge of the gas bubble, the gas comes into contact with the oxygen and catches fire.


•The temperature of the fireball is approximately 27 00o F (1500o C ). The bubble has burned all of the plant equipment that was in it’s path, the light was quickly shut off.

•The conventional protections did not work:

•The security door, supposed to contain the fire in the bunker, closed well after the bubble escaped

•The fire protection equipment, including the water spray system, was not activated.

•Two people tried to escape. They were fortunate in that they were only badly burned and were not killed in the fire.

•The whole power plant (1,350 MW) was out of service for 4 months. The damaged section (450 MW) was out of service for more 13 months.


VIDEO OF GAS BUBBLE AFTER TANK RUPTURE


Technical and Financial Benefits

FINANCIAL BENEFIT


☛ The TRANSFORMER PROTECTOR is a passive mechanical sy stem , which can only be activated by the level of the transformer tank inte rnal pressure reached during short-circuits.

☛ The TRANSFORMER PROTECTOR has therefore a very high reliability,as false activation is impossible.

☛ On request, nitrogen can be injected manually to eliminate all actuators.

Financial Benefits – RELIABILITY

FINANCIAL BENEFIT


MAJOR TRANSFORMER POLLUTION CASES

INCIDENT POLLUTION CONSEQUENCES

COST INFORMATION

(MUSD)

Binghamton, NY

1981

PCB contamination of an 18-story state office building

Clean-up 53

Lawsuit 100

Warren County, VA

1985

PCB contamination of the Shenandoah River

Clean-up 40

Environmental penalty

6.5

New Paltz, NY

1991

PCB Contamination of the SUNY New Paltz campus

Clean-up 50

Lawsuit 73

TRANSFORMER PROTECTIONFINANCIAL BENEFIT

Financial Benefits – Cost of LITIGATION


•The cost of the TRANSFORMER PROTECTOR is a fraction of the cost of an explosion.

•During an internet search for 1 year, SERGI found more than 730 transformer explosions in the US alone.

FINANCIAL BENEFIT

Financial Benefits – Cost of the TRANSFORMER PROTECT OR


� The TRANSFORMER PROTECTOR acts before any damage is done.

TRANSFORMER PROTECTOR TECHNOLOGY :

� In terms of damage cost reduction, the TRANSFORMER PROTECTOR offers three main advantages:

• It saves all surrounding equipment and buildings from

explosion and fire;

• It leaves the environment unharmed;

• It enables the quick internal repair of the transformer .

FINANCIAL BENEFIT

Financial Benefits – SUMMARY


As of December, 2008: (ref FfTPk)

- 1293 TRANSFORMER PROTECTORS have been sold

- in the world, 87 companies from 46 different count ries have included the TRANSFORMER PROTECTOR in their Technic al Specifications

NFPA Handbook – Processes and Facilities, Section 9, Chapter 14, Electric Generating Plant

The first TRANSFORMER PROTECTOR was sold in 2000 in Italy

TRANSFORMER PROTECTION

REFERENCES


TRANSFORMER PROTECTIONTRANSFORMER PROTECTION

Installation Examples


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

DEPRESSURIZATION PIPING

RETROFITTING ON EXISTING TRANSFORMERS

The TRANSFORMER PROTECTOR is easily retrofitted with out tank machining by using the existing interfaces



OVERVIEW



DEPRESSURIZATION SET



OLTC EQUIPPED WITH OIL FILTRATION UNIT



RETROFITTING ON EXISTING TRANSFORMERS

The TRANSFORMER PROTECTOR can be retrofitted on the Transformer cover by using a vertical Depressurization Set

� The TRANSFORMER PROTECTOR can be retrofitted on transformer cover by replacing the Pressure Relief Valve by a T-piece and installing a Vertical Depressurization Set

� Any manhole available on the transformer can be used as a base for retrofitting of a Vertical or Horizontal Depressurization Set



DEPRESSURIZATION SET - TRANSFORMER



THANK YOU FOR YOUR THANK YOU FOR YOUR THANK YOU FOR YOUR THANK YOU FOR YOUR

KIND ATTENTIONKIND ATTENTIONKIND ATTENTIONKIND ATTENTION



SERGI FRANCE186, Avenue du Général de Gaulle – P.O. Box 90

78260 Achères, France�� : (33) 1 39 22 48 67

�� : (33) 1 39 22 11 11

@ : [email protected]

web site : www.sergi-france.com

Our Sales Area Manager : Mr. FERNANDES


Documents

Thomas Fernandes