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2007 Annual Meeting; February 25-March 1, 2007 — Orlando, FL, USA

BALCO FUSE TECHNOLOGY

J.RamaswamyBharat Aluminium Company Limited

(A member of VEDANTA Resources plc.)India


Contents

• Introduction

• Present Technology

• Innovation

• Principle

• Design

• Observation

• Further Modification

• Result


Introduction <

VISION

“To achieve global standards of excellence in

productivity and customer satisfaction”

TECHNOLOGY

• GP 320 Potline - GAMI Technology,China

• 288 pots – Single pot line ( Two rooms )

• 2,45,000 tons Al / annum

• 540 MW Captive Power Plant


Present Technology <

• No provision for online power on of pots.

• As per the GAMI design, power outage was

required every time a pot is put on preheat.

• The shorted riser joint bolts are loosened and a

gap is made at the joint to insert the insulation

plates at 0 kA to put the pot on power. (fig.)

• This procedure of putting pots on power involves

6-10 minutes at 0 kA along with 30-35 minutes of

power reduction (320 kA – 0 kA and 0 kA to

320kA)


Innovation >

• Two fuses per riser were designed to by pass the

line current, till the pot was cut into the circuit.

After a calculated safe period of time, the fuses

melt resulting in the pot coming into potline

circuit.

• Fuse assembly - Two fuse blocks, a Fuse and

three types of fuse clamps (fig.)

• Fuse block is designed to maintain proper

contact with the riser and as a platform to clamp

the fuse.


Innovation (contd..) <

• Clamp 1 is used to clamp the fuse block with the

riser.

• Clamp 2 is used to clamp the fuse block with the

shorted joint bus bar (fig.)

• Clamp 3 is used to clamp the fuse with the fuse

blocks.


Principle >

• Prior to the power on of the pot, fuse assembly is

fitted on lower part of all riser with clamps.

• When the shorted riser joint is opened for the

insertion of insulation plates, the circuit is

temporarily completed through the fuses.

• These fuses by pass the line current for a

calculated period of 10 minutes, till the pot is cut

into the circuit.


Principle (contd..) <

• During the increase of current to 320 kA in steps,

the fuses melt and the pot is put on power.

• With the fuse technology, power on takes 20-25

minutes with around 6-10 minutes at 240 kA.


Design >

The dimensions for the fuse were calculated –

• Based on Resistivity.

• Based on the thermal stress due to short circuit

current.

• Electrical fusing time principle.


Design (contd..) >

Based on Resistivity

R = V / I and R = ℓ l / A

Where R = resistance in Ω

V = Voltage drop in Volts

I = Current in Amps

ℓ = resistivity of Al at 20 0c

l = Current in Amps


Design (contd..) >

Based on the thermal stress due to short circuit current.

Ik * 1000 * √ t

A = —————————————————————

√ [4.184 (c* ℓd)/ (ℓr * α) ln 1 + α (Vmax – V1)]

Where, A = cross sectional area of the fuse

Ik = current in kA t = time in seconds

c = specific heat of Aluminium

ℓd = density of Aluminium

ℓr = resistivity of Aluminium at ambient temperature

α = 0.004 Vmax = Maximum temperature

V1 = initial temperature


Design (contd..) <

Electrical fusing time principle.

I * √ 33 * S

Am = ————————————————————

√ log10 [(Tm – Ta) / (234 + Ta) + 1]

where I = current in amps

Am = conductor area in circular mills

1 circular mill = 0.7854 mil2

1 mil = 1/1000 inch

S = time in seconds

Tm = melting point of aluminium

Ta = ambient temperature


Observation <

• With the fuse technology, power on takes 20-25

minutes with around 6-10 minutes at 240 kA as

compared with 30-35 minutes with around 6-10

minutes at 0 kA without fuse (fig.)

• The results have shown that 100% of the fuses

have melted (fig.)


Further Modification <

• Although pots could be powered on at full line

current of 320 kA but to be on safe side, the line

current is reduced to 240 kA.

• The numbers of preheat shunts were increased to

bypass a higher percentage of current, as the line

current is brought up to 320 kA.


Result >

• The saving is $ 1.4 million for starting up of the

pot line of 288 pots.

• Disturbances to the operating pots due to

frequent power outages are eliminated.

• No negative impact on the power plant operation

as well as on its equipment.


Result (contd..) >

• Comparatively negligible production losses due

to only nominal decrease in line amperage during

power on of pots.

• GP 320 technology is enhanced by this

innovation and becomes more competitive in the

world market.


Thank You


Shorted Joint <


Fuse Assembly <


Fuse Assembly fitted on riser <


Current vs. Time Graph <

0

80

160

240

320

1 6 11 16 21 26 31 36Time (min.)

Cu

rren

t (k

A)

with out fuse with fuse


Status of Fuse <

POT NO 622 POT NO 314

TAP END FUSE Blown completely Partial melting at the clamp joint

DUCT END FUSE Blown completely Melting at the clamp joint

TAP END FUSE Partial melting at the clamp joint Melting at the clamp joint

DUCT END FUSE Blown completely Melting at the both clamp joint

TAP END FUSE Blown completely Melting at the both clamp joint

DUCT END FUSE Partial melting at the clamp joint Melting at the both clamp joint

TAP END FUSE Melting at the both clamp joint Melting at the clamp joint

DUCT END FUSE Partial melting at the clamp joint Partial melting at the clamp joint

TAP END FUSE Melting at the clamp joint Melting at the clamp jointDUCT END FUSE Melting at the clamp joint Partial melting at the clamp joint

DATE 05.02.06

RISER 1

RISER 2

RISER 3

RISER 4

RISER 5


Savings OLD PRACTICEPots Considered 286 No.Voltage drop across each pot 4.2 VCurrent thrown off 320000 AVoltage leak 20 VTotal input Voltage 1221.2 VAC to DC efficiency 99%Power consumed 394.73131 MVAPower factor 0.95Active power consumed 374.99475Auxiliary power 16 MWTotal active power 390.99475 MWTotal power thrown off 390.99475 MW

NEW PRACTICECurrent thrown off 140000 APower consumed 172.69495 MVAPower factor 0.95Active power consumed 164.0602Auxiliary power 16 MWTotal active power 180.0602 MWTotal power thrown off 180.0602 MW

Saving of 210.93455 MW

Period over which throw off occurred 80 minutes

Total units saved 0.2812461 MUFinancial savings 320620.51 Rs. per pot addition


Line current increase in steps

• 0-80-160-240-280-320

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