Monitoring discontinuities in the 25 kV overhead

The sliding contact between pantograph and 25 kV overhead contact system (OCS) contact wire is a critical interface between train and infrastructure in an electrified railway. As well as requiring correct tensioning and geometry, it is necessary that the contact wire be free of imperfections and obstructions. Such discontinuities can develop for a variety of reasons and can lead to catastrophic failure. Examples of discontinuities include severely restricted wire uplift, contact wire kinks, and detached or badly adjusted fittings hanging foul of the contact wire. All of these problems can potentially damage the relatively fragile pantograph carbons or lead to failure of OCS components. A system has therefore been developed to detect such faults. Known as OLIVE (Overhead Line Investigation by Vehicular Equipment), the system is designed to be fitted to selected revenue earning service vehicles so that the OCS can be monitored on a day to day basis. The system can be used as a tool to plan maintenance activities and, in extreme cases, to rapidly track down faults requiring emergency action.