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Archives for Power Quality

Steel Mill in the Neighborhood: Part 2 (In Your Backyard)

The steel industry is just giddy on new and upgrades to steel mills.  Google the subject and you’ll find — the Minnesota Steel & Iron project in Itasca County, MN, the upgrade of the Pacific Steel Casting mills in Berkeley, CA, and Brazilian steel company CSN’s plans to build a steel-rolling mill in Kentucky, among others, in recent news.  For whatever the reason, mill developers see an increased demand for their product providing impetus for increased capacity.  A key economic factor for additional milling capacity is the availability of steady, low-cost power supplies for their mills.

This bodes well for the power industry in at least one respect — mills represent a high load factor customer, not a lot of MW installed required for the annual energy consumption.  However, they do pose new challenges to maintaining reliability and power quality.

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Steel Mill in the Neighborhood

As a type of electrical load, steel mills are the equivalent of jackhammers early in the morning. If you’re not prepared for them, they can cause headaches. Steel mills, with arc furnaces, have a randomly varying demand that can swing as much as 200 MW for a 300 MW steel plant every 30-90 minutes or so. The effects of this load change may be noticed in lights, PC’s, and TV’s. When a mill’s furnace comes on, the voltage dips and rises when it is switched off.  Voltage and the frequency will change and result in a change of light intensity.  In addition, the arcs in each furnace of the mill can result in an imbalanced load that is loaded with harmonics that varies cycle to cycle creating what one may call “dirty” power. This load connected to the grid can affect other customers connected to the grid.

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