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Restricting Voltage Fluctuation

02/26/2010 9:50 AM

In Steel melting or making shop, high current electric electrodes insert into the liquid steel to create arcing to produce special quality steel. Due to this, total system voltage of steel melting furnace is being fluctuated heavily. Many motors or other equipments get burnt or damaged due to this fluctuation. How does this fluctuation can be eliminated or reduced to improve power quality, to increase production and minimise the breakdown time, to save other electrical equipments?

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Guru

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#1

Re: To restrict Voltage Fluctuation

02/26/2010 10:13 AM

Did you have dedicated transformer (Captive Transformer) for electrode loads? If not, then use dedicated transformer for this load.

Do complete voltage drop study of your system to find the voltage drop of each section and then replace the cable with higher size where voltage drop seems high. For the calculation of the voltage drop, the electrode load must be considered.

- MS

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#4
In reply to #1

Re: To restrict Voltage Fluctuation

02/26/2010 7:53 PM

Yes, we already have a high current converter transformer for it. But fluctuation problem is still there.

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Commentator

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#2

Re: Restricting Voltage Fluctuation

02/26/2010 3:03 PM

A separate medium transformer (depending on the load) with high secondary current rating is required, do you have already?

Try to keep separate bus with motor protection for other loads.

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Guru
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#3

Re: Restricting Voltage Fluctuation

02/26/2010 4:03 PM

You also need to verify the capacity of the utility primary system. If the utility has a weak system, you will continue to have these voltage variations regardless of what you do.

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Guru
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#5

Re: Restricting Voltage Fluctuation

02/26/2010 9:35 PM

Get a huge inductor. US Navy minesweepers had a twenty ton flywheel on the magnetic shock generator. A dedicated diesel would spin up the flywheel, and then the switch would be thrown. Alone the generator could not deliver the pulse desired, but with the aid of the oversized flywheel, a huge steady pulse was delivered.

For your furnace, have a motor-generator set with a huge flywheel. Under normal conditions the loss will be minimal, less than burned up motors. When your furnace starts acting up, the flywheel will smooth out the bumps.

And you could have a nice strong diesel on the other end of the generator to help things along, clutch it in when needed.

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#6
In reply to #5

Re: Restricting Voltage Fluctuation

02/26/2010 11:27 PM

Our power houses are connected to grid. So you may consider our system as infinite bus bar. Other plants are working normally. But during heavy arcing, the voltage of that particular s/s(which is dedicated to steel melting shop) is fluctuating. Other plants remain normal during arcing.

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#7
In reply to #6

Re: Restricting Voltage Fluctuation

02/26/2010 11:53 PM

As long as you are not generating your own power you can do nothing but to increase the capacity of your s/s transformer. when arc initiates a high overload occurs on your transformer with a big voltage drop making the arc to exctinguish and voltage rise again to re-initiate the arc the only solution is to have a biger transformer from your grid operator b/r

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#8

Re: Restricting Voltage Fluctuation

02/27/2010 2:07 AM

If you have already provided for an independent well sized transformer and cables, this is probably due to the source impedance. What is the type of grid connection you have, (voltage level, distance from substation, other loads on the line etc.) ? Depending on the system constraints you face and the criticality of the problems due to this issue, a power electronics based dynamic voltage support solution may be of help in this case. Let me know if this is of interest.

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#11
In reply to #8

Re: Restricting Voltage Fluctuation

02/27/2010 11:31 PM

We have in house generation around 150MW. Our system is connected to eastern grid in 132KV level. At evening hours, we also sell power to grid. Pls explain me the term "dynamic voltage solution". Can SVC or reactor reduce the voltage fluctuations?

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#12
In reply to #11

Re: Restricting Voltage Fluctuation

02/28/2010 3:28 AM

why not list the different subject under new discussion. As far as role of reactor between two power system, it helps in getting disturbances from the other system in parallel operation. higher the impedance, less will be impact of disturbance from other. It is analogous to partial quarantine approach.

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#9

Re: Restricting Voltage Fluctuation

02/27/2010 7:20 AM

I have no direct experience in steel industry but I relate the phenomenon with the welding. As arcing takes place the heavy current flows, which affects the system voltage. Normally changes in electric circuit is minimized using inductance and capacitance. Capacitance may not help much in this situation you may think of having series inductor or if there are many such electrodes, these loads may be isolated by providing a 2 winding isolating transformer. I expect smoothing in voltage fluctuation. if you implement and find result, publish the solution at this site.

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#10
In reply to #9

Re: Restricting Voltage Fluctuation

02/27/2010 7:25 AM

FURTHER I read other answers. I know the solution moves towards providing the isolation transformer. For this application, isolation transformer with very high impedance may be necessary.

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#13

Re: Restricting Voltage Fluctuation

12/02/2010 7:06 AM

1) Power electronics can help! Like SVC

2)change to higher voltage or DC for the feeder

Maybe we can also use DSTATCOM or APF to solve you problem in the future based on the development of the such technologies.

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#14
In reply to #13

Re: Restricting Voltage Fluctuation

12/02/2010 8:26 AM

DSTATCOMs have proven capabilities in giving relief for steel industry voltage flicker / regulation problems. If this is of interest, we can help.

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Guru
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#15

Re: Restricting Voltage Fluctuation

01/20/2025 11:40 AM

Increase the incoming supply capacity to the point where these <...motors or other equipments get burnt or damaged...> no longer happen; the other option is to turn them off while <...high current electric electrodes insert into the liquid steel...>.

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