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Case Study

Blytheville

Static Var Compensation of DC Arc Furnaces

A Static Var Compensator (SVC) rated at 5 Mvar inductive to 195 Mvar capacitive supplied by Hitachi Energy has been in operation since 1992 in the DC arc furnace shop of NUCOR Steel, Blytheville, Arkansas. The purpose of the compensator is to provide dynamic voltage control and reduce fast voltage variations created by the operation of two DC arc furnaces, each rated at 130 MVA. Two ladle furnaces, each rated at 21.5 MVA, are being compensated as well.

Dynamic power factor correction is also provided by the SVC, achieving an overall power factor for the plant of close to unity for all operational conditions.

DC arc furnaces in general constitute troublesome loads on industrial networks, consuming large and quickly varying amounts of reactive power as they operate through the various phases in their process, thereby giving rise to voltage depressions as well as fluctuations in the surrounding network and on the furnace bus itself. They are also large sources of harmonics.

The SVC offers an efficient means to rectify these shortcomings as it will keep up a high and stable voltage on the furnace bus, thereby contributing to productivity and economy of the process. 

Main data
System Arc Furnace SVC
Commissioning year 1992
Controlled voltage  34.5 kV
Dynamic range  5 Mvar inductive to 195 Mvar capacitive 
Harmonic filtering 30 Mvar/2nd harmonic
35 Mvar/3rd harmonic
30 Mvar/4th harmonic
20 Mvar/5th harmonic
80 Mvar/11th harmonic
Control system Feed forward reactive power control plus selectable closed loop modes for voltage control, reactive power control and power factor control
Thyristor valve  3-phase water-cooled valve with indirect light firing of thyristors

Single-line diagram, Blytheville SVC