Control and protection system ABB has its own powerful, flexible and reliable control and protection system which uses state-of-the-art computers microcontrollers and digital signal pro cessors connected by high-performance industrial standard buses and fiber-optic communication links. The system is called MACH (Modular Advanced Con trol for HVDC and SVC) and is designed specifically for converters in power appli- cations. All critical parts of the system have inherent parallel redundancy and use the same switch over principles that have been used by ABB for HVDC app cations since the 1980s.