An SVC Light‚ rated at 33 kV, 0-164 Mvar has been installed in the melt shop of Outokumpu Stainless Oy in northern Finland, based on a very large Electric Arc Furnace (EAF), rated at 140 MVA, +20% short-time overload capability. The EAF takes its power from a 110 kV grid. Due to a modest short-circuit level at the Point of Common Coupling, the EAF would become a formidable source of disturbances, which, if not properly
remedied, would spread through the grid to other consumers of electric power. The EAF is also a heavy consumer of reactive power. The task of the SVC Light is to remedy these disturbances in order to maintain proper power quality in the feeding grid as well as in the plant itself. In fact, the SVC Light is a prerequisite for operation of the EAF at full power.
With the SVC Light in operation, a flicker reduction factor > 4.5
The European Union has firm regulations on power quality issues such as flicker: acceptance levels, methods for measurement, and flicker meters. As a consequence, the Finnish Transmission System Operator and grid owner, Fingrid, imposes strict requirements on power subscribers connected to its grid system, in order that proper power quality in the grid is maintained at all times. This fact, in the case of the steel plant, gave rise to a need for measures to neutralize the gridpolluting effects from the EAF. As an extra benefit, increased power into the EAF was achieved, enabling an improvement of process economy for the plant.
EAF: a demanding load
The EAF is a generator of several kinds of disturbances, which, unless remedied, add up to more or less severe deterioration of power quality. Large and stochastic variations in reactive power consumption give rise to large and rapid grid voltage fluctuations, which show up as illumination flicker, a particularly annoying sensation for people exposed to it.
Furthermore, the EAF is an asymmetrical load on the threephase feeding grid, giving rise to current and voltage unbalance in the grid. Normally, only very limited levels of asymmetry can be allowed without causing deterioration of power quality for other consumers connected to the same grid.
And last but not least, the EAF is a generator of harmonics, odd and even, as well as interharmonics.