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Customer Success Story
Dunkerque SOLLAC

SVC for voltage stabilization and harmonic suppression in rolling mill

Since 1985, G.T.S Industries – site SOLLAC Dunkerque, France is operating a Static Var Compensator (SVC) delivered by Hitachi Energy. The SVC, which has a dynamic (thyristor controlled) range of 66 Mvar capacitive is connected to a 90 kV rolling mill bus. Its purpose is to stabilize the bus voltage under varying load conditions which occur during the running of the mill.

This SVC also comprises harmonic filters tuned to the 5th and 7th harmonics in order to suppress harmonic generated by the thyristor converters in the rolling mill, thereby preventing these harmonics from entering into the surrounding parts of the network.

Furthermore, it achieves power factor correction of the rolling mill, thereby relieving the network of reactive power burden and contributing to a considerable decrease of the running costs of the mill.

(A saving of about 3 million francs a year on the power billing in 1986 currency).

Besides being a source of harmonics, a rolling mill as a load on the network is generally characterized by high and fluctuating consumption of reactive as well as active power. As a consequence, the rolling mill will give rise to voltage fluctuations in the feeding network, the severity of which being dependent on the relationship between the size of the rolling mill and the strength of the network.

Main data
System SVC
Commissioning year 1985
Controlled voltage 90 kV 
Dynamic range 0-66 Mvar (capacitive)
Harmonic filters 33 Mvar/5th
16,5 Mvar/5th
16,5 Mvar/7th 
Control system 3-phase symmetrical closed-loop reactive power control
Thyristor valves Air cooled thyristor valves with magnetic triggering