ArcelorMittal Bremen, Germany is a flat steel manufacturer, producing high quality steel, mainly for automotive, engineering and construction industries. A 45 MVA, 300 tonnes electric twin ladle furnace (TLF) is in operation at the plant for liquid steel heating and treatment. It operates at a power factor less than 0.8, causing considerable, fluctuating consumption of reactive power. To maintain power quality in the grid feeding the plant, an SVC Light supplied and installed by Hitachi Energy was energized in 2013 on the 30 kV TLF bus. The SVC Light is rated at 28 Mvar inductive to 52 Mvar capacitive (-28 / +52 Mvar) at 30 kV.
The 30 kV switchgear was also supplied by Hitachi Energy, enabling the optimum selection of a space-saving disconnecting circuit breaker, as well as control and protection for the SVC.
When fully operative, the twin ladle furnace is utilized to heat some 3.5 million tonnes of crude steel per annum. In conjunction with the substantial rated power of the twin LF, operation of the LF, where power is switched periodically between the two ladles, causes voltage dips and fluctuations on the LF bus as well as at the 110 kV point of common connection (PCC). At the same time, the Grid Code permits only a very low level of flicker emission into the grid. Powerful flicker mitigation is required, calling for SVC Light, a STATCOM type of device.
The LF is also a source of harmonics and phase imbalance, also reduced to acceptable levels by means of the SVC Light.
|Feeding grid voltage||110 kV, 50 Hz|
|Furnace bus voltage||30 kV|
|Rated LF power||45 MVA|
|SVC Light rating||30 kV, -28 / +52 Mvar|
|VSC||- 40 MVA; Three-level, neutral point clamped converter;
- IGBT based, pulse-width modulated
|Control system||- Open-loop, phase-wise dynamic var control;
- Closed-loop power factor control