The Fault Detection System of the Windings of RFX

The protection of the Magnet System of RFX requires that electromagnetic faults of the windings and their circuits are detected within one millisecond. At this aim a specific system has been designed and implemented. The system, named RGM, can quickly detect electric faults as short circuits, earth faults, toroidal shell short circuit, plasma faults and operation failures. It sends logic signals to the central fast protection system of RFX, in order to initiate protective actions for the whole plant. RGM includes 97 probes and a central processing unit. The probes are located on the machine windings and feeding bus-bars and are mainly based on Rogowski coils. Their analog lectric signals are processed by the central unit. This is a cabled logic analog/digital unit able to performs signal analyses and fault detections within some tens of microseconds. The major features of the system are high fault sensitivity, high reliability, immunity to electromagnetic interferences and electric insulation from the power circuits. Whenever possible, couples of probes provide differential detection on pairs of quantities which in normal operation are equal. Most probes perform differentiating operation, but for some integrating operation has been preferred. The central processing unit is provided with self-testing features of line continuity and intervention capability. Design manufacturing process and testing procedures are aimed to guarantee the required quality and reliability.