\r\nThe 15-MVAr modules are designed to provide power compensation, improve voltage quality and increase the stability of the network. The first two units will be based near the southern portal of the Simplon tunnel and will be commissioned in 2015, while a third will be supplied for use around Neuhausen-am-Rheinfall in northeast Switzerland.\r\nThe compensators will be installed in 40ft high-cube containers, which can be linked to the network control system through a telecontrol interface. The unit will be linked to the overhead contact wire via a plug-in connection.\r\nSiemens says auxiliary services can be powered using either the 15kV 16.7Hz ac traction supply or through the 400V 50Hz mains supply. Each unit is fitted with gas-insulated medium-volage switchgear, as well as power converters, a cooling unit, and protection and control technology.\r\nThe Sitras SVC Plus reactive-power compensation system is based on voltage-sourced converter technology, and is built around a modular multilevel direct converter. The power converter consists of a large number of series-connected power transistor modules (IGBT) and capacitors. These series-connected modules act as a controllable voltage source, which builds up sine-wave voltage.\r\nAccording to Siemens, this allows low-frequency harmonic filters to be eliminated, which reduced the size of the overall system and allows it to be housed in a standard container.\r\nThe contract includes an option worth SFr 10m for four additional units.