An electrical system comprising: a circuit comprising: one or more rotating power delivery assemblies (18, 18A, 18B) comprising a plurality of sliding surfaces (34, 36) that deliver power to a rotating load; a plurality of radio frequency current transformers (RFCTs) (46A, 46B, 46C, 46D) that measure radio frequency signals corresponding to arcing events in the one or more rotating power delivery assemblies, the plurality of radio frequency current transformers (RFCTs) (46A, 46B, 46C, 46D) being disposed at a number of different predetermined locations within the circuit; and a processor configured to: receive the RF measurements from the plurality of RFCTs (46A, 46B, 46C, 46D) at the plurality of different locations within the circuit; characterised in that the processor is further configured to: isolate and subtract background RF noise from the received RF measurements based on the different location of the plurality of RFCTs within the circuit; and determine a value indicative of the amount of arcing occurring within the circuit based, at least in part, on the received measurements. a circuit comprising: one or more rotating power delivery assemblies (18, 18A, 18B) comprising a plurality of sliding surfaces (34, 36) that deliver power to a rotating load; a plurality of radio frequency current transformers (RFCTs) (46A, 46B, 46C, 46D) that measure radio frequency signals corresponding to arcing events in the one or more rotating power delivery assemblies, the plurality of radio frequency current transformers (RFCTs) (46A, 46B, 46C, 46D) being disposed at a number of different predetermined locations within the circuit; and a processor configured to: receive the RF measurements from the plurality of RFCTs (46A, 46B, 46C, 46D) at the plurality of different locations within the circuit; one or more rotating power delivery assemblies (18, 18A, 18B) comprising a plurality of sliding surfaces (34, 36) that deliver power to a rotating load; a plurality of radio frequency current transformers (RFCTs) (46A, 46B, 46C, 46D) that measure radio frequency signals corresponding to arcing events in the one or more rotating power delivery assemblies, the plurality of radio frequency current transformers (RFCTs) (46A, 46B, 46C, 46D) being disposed at a number of different predetermined locations within the circuit; and a processor configured to: receive the RF measurements from the plurality of RFCTs (46A, 46B, 46C, 46D) at the plurality of different locations within the circuit; receive the RF measurements from the plurality of RFCTs (46A, 46B, 46C, 46D) at the plurality of different locations within the circuit; characterised in that the processor is further configured to: isolate and subtract background RF noise from the received RF measurements based on the different location of the plurality of RFCTs within the circuit; and determine a value indicative of the amount of arcing occurring within the circuit based, at least in part, on the received measurements. isolate and subtract background RF noise from the received RF measurements based on the different location of the plurality of RFCTs within the circuit; and determine a value indicative of the amount of arcing occurring within the circuit based, at least in part, on the received measurements.