Steel Mills and Power Quality 1

[dcdtn]

I am interested in information about the latest equipment available to minimize power quality problems (flicker, etc.) associated with arc furnaces at steel mills. Is there equipment available that could correct all PQ problems for a 500MW steel mill connected at 161-kV? And if so, at what cost?

Thanks

 

[jlazucena]

I am interested in information about the latest equipment available to minimize power quality problems (flicker, etc.) associated with arc furnaces at steel mills.
A/We are too
Is there equipment available that could correct all PQ problems for a 500MW steel mill connected at 161-kV?
A/One option: apply static var compensators for the flickers (And harmonic filters)
the other option is another reactor in parallel with the furnace current limiting reactor. The second reactor has a static switch and used to optimize the arc (And harmonic filters), you can find this product at

http://www.inverpower.com/products/splc/splc.html

 

[busbar]

A root task may be an RFQ with sufficient detail circulated among larger electrical-equipment manufacturers. I don’t think you’ll find any sort of off-the-shelf fix. It’s likely a cost-effective approach would have to be applied at a lower voltage.

 

[gordonl]

Another thing to consider is the option of DC furnaces. I don't have personal experience, but apparently they are supposed to be "cleaner".

 

[kevd]

500MW is a big complex, even for a complete steel production plant. Is it a USX site?

Mind you a large Hot strip mills may have 120MW of connected plant.

Compensation is available and is usually applied at various levels close to the offending plant, because the distribution system is complex and users have feeders at various levels. A simple single all encompassing compensation is rarely the answer.

Arc furnaces almost invariable need VAR compensation and static compensators are common place. In the USA there are numerous vendors in this market, so a quick search and you find them easy enough.

Very large reversing mills often get overlooked. The main drive technology will influence the type of compensator.
The MVARs on each pass are a function of the speed as the piece gets rolled. (unless it is a VSI, but this unlikely in USA, normally DC)
Cycloconvertors are notorious for producing flicker from interharmonics and sub-harmonics. These are difficult to filter. Very fast static compensators are available from some manufacturers. The clever ones even have a fibre optic link from the torque control output of the drive straight into the phase control of the static compensator. The response is incredible and gives good compensation.

Some large, high prodcution, cold mills also need compensation as the VARs drawn at threading speeds is large compared to normal rolling speeds.

Process lines can be easier as the power flows are usually more continuous. However, depending on the type of process these may also need compensation, perhaps switched VAR compensation.

I suggest that a total study of the system is carried out and each plant is assessed with measurements.

The big vendors of steel rolling/production equipment such as SIEMENS, ABB, GE or ALSTOM all will have offerering that can help you.

 

[dcdtn]

hevd,

Thanks for the detailed response. I must admit that I know very little about steel production, other than that steel plants, even small ones (10-50MW), have caused a lot of power quality problems on our system when connected at 161-kV.

The 500MW plant I mentioned has not been built. One of the potential locations for it is not near a 500-kV tranmission line, so I was wondering about the feasibility of serving it at 161-kV so that I can come up with a rough estimate as to connection costs. I would like to add to the 161-kV connection cost an estimated amount for equipment required to provide acceptable power quality. Then I can have an idea about whether it is cheaper to serve at 161-kV or 500-kV.

I realize it is difficult to estimate without knowing further details, but a ballpark, worst case figure is fine.

Thanks.

 

[cuky2000]

There is advantage to connect large load to at 500 kV rather than 161 kV.

The option to connect at lower voltage is not very attractive considering the potential problems associated with system stability degradation, sub synchronous resonance in power generating plants, overload power lines, etc. that will make difficult any approval process with the local utility specially if this will be connected to TVA.

Even thought cost of some of the hardware rated for 500 kV class may be higher, the overall cost of the project will be recover in short term considering the saving on energy cost, reduction on liability and other indirect cost such as upgrading lines, substation, studies, etc.

Birmingham Steel, AL, which presently operates connected from a substation at 500 kV has also an SVC and filter to minimize the flicker. Initially this project was designed at lower voltage.