Device to estimate overhead line fault location in 2x25 kV electric traction: prototype overview

Aurizon's Blackwater and Goonyella coal rail systems use 2x25 kV electrification. The overhead line can have small electrical clearances and the railway usually runs through bushland, paddocks and uninhabited areas. These factors contribute towards a significant number of faults occurring on the overhead lines. If the circuit does not hold after one reclosing attempt, intervention is required on site to remove the foreign object causing the short circuit. However, by relying solely on the knowledge of which circuit breaker has tripped, it is only possible to pinpoint the fault down to a whole electrical section, which is the track comprised between a feeder station and a track sectioning cabin. An electrical section can be tens of km long. In this case locating and rectifying the fault can be time-consuming and difficult. For these reasons, QR introduced almost three decades ago fault locator devices named QRFLs, which provide the Electric Control Officer (ECO) with an estimate of the location along the track within the section where the fault occurred. Currently, the technology used in the existing devices is ageing and the componentry is becoming obsolete: therefore, a new system is being designed and deployed. This paper firstly presents an overview of the fault location system. It then introduces the theory of fault location based on return current measurement, followed by a description of the currently installed fault locator system and of its characteristics and technical challenges. The technical challenges encountered with the system are outlined, and improvements introduced with the new design are described.