Metallurgy

How a metallurgical plant draws power

Production lines in metallurgy are characterised by continuous operation: heating, rolling, fans and pumps run day and night, and a single line consumes a great deal of energy. The load combines steady auxiliary demand with impact loads that follow the process cycle, so the distribution system has to carry high current and frequent variation at the same time.

Site conditions are demanding: shops are hot and dusty, and some areas add metal swarf and oil mist. Substations are usually placed in the bays or next to the line, both to shorten the supply radius and to keep the equipment stable and easy to inspect in a hot, dusty environment.

What metallurgical plants have to cope with

Metallurgical distribution has to be optimised at both ends: as few transformation stages as possible upstream, motor circuits as easy to maintain as possible downstream.

• Continuous production and high annual running hours, which magnify every loss
• Impact loads and large motor starts causing current variation
• Heat, dust and metal swarf in the shop affecting cooling and insulation
• Multiple transformation stages adding footprint, investment and maintenance points
• Costly downtime, so a faulty circuit must be isolated and replaced quickly

Removing a transformation stage, keeping overload margin in the equipment and making drawers quick to change are the three measures that pay off most in a metallurgical retrofit.

Coreda's approach for metallurgy

We take the medium voltage directly to the load centre with 20 kV and 35 kV dry-type transformers, then handle shop-level distribution with low-loss oil-immersed transformers and withdrawable LV switchgear.

Recommended configuration:

• 20 kV and 35 kV SC(B)10 and SC(B)11 dry-type transformers: step 35 kV or 20 kV directly down to a 400 V distribution supply or to 10 kV, removing a 10 kV transformation stage; class H (180 °C) or class F insulation, 120% continuous overload without forced cooling, with low-noise fans available for forced air cooling.
• S13, S20 and S22 10 kV low-loss transformers: ratings from 30 kVA to 2500 kVA in a fully sealed tank, maintenance-free, with good resistance to moisture, dust and corrosion for demanding conditions.
• GCS withdrawable LV switchgear: rated operating voltage 380 (660) V and rated current up to 4000 A for incoming, feeder, centralised motor control and reactive-power compensation duties, with the functional compartments separated from one another.

Direct MV supply saves the footprint and the losses of an intermediate substation, while the withdrawable design confines a circuit fault to one drawer, which can be dealt with in a short shutdown window.