Fault analysis and protection of the RFX toroidal field winding

The RFX Toroidal Field (TF) Winding consists of 48 coils (8 copper turns each) fed, during the first phase of the pulse, by a 4.8 MJ, 7kV capacitor bank and thereafter by controlled thyristor converters. The present analysis takes into account a variety of fault conditions. The current waveforms resulting from the fault analysis are used to identify the most severe fault conditions and to design the protection system of the machine. In case of fault, the rapid growth of the current requires a fast detection to assure an effective protection to prevent the electrodynamic forces from growing beyond a tolerable level. The action undertaken depends on the severity of the fault and generally involves different machines components; the required coordination is performed by a Global Fast Protection System which is outlined in this paper