Non-telecommunication based DC line fault detection methodology for meshed HVDC grids

One of the most challenging aspects regarding realisation of meshed high-voltage direct current (HVDC) systems is the handling of DC line faults. Due to the specific DC fault current phenomena, AC fault detection and clearance methods are not applicable in meshed HVDC grids. New fault clearing algorithms and equipment need to be developed. Therefore it is necessary to be aware of the DC fault current characteristics. Starting from a travelling wave approach simplifications for fault currents in low - and high impedance earthed DC grids are derived. On this basis, a non-telecommunication based DC fault detection algorithm is designed. Due to its decentralised implementation, it is very fast acting, reliable and economic in comparison with centralised approaches which are characterised by a parallel telecommunication system. Furthermore it is able to detect pole to pole as well as pole to earth faults in low- and high-impedance earthed DC grid. Finally this fault detection algorithm is validated by numerical case studies.