Fast Fault Detection and Protection

Abstract

Low voltage direct current (LVDC) networks used as electricity distribution systems for a community have the potential of operating at higher efficiencies and can integrate various distributed renewable energy sources and storage elements. However, their emergence is being hindered due to the lack of reliable fault protection techniques. DC faults exhibit extremely fast current rise rates as compared to faults in AC grids. Therefore, this research focuses on developing a fast fault detection and isolation technique applicable especially in LVDC networks. Fault isolation was achieved via solid state circuit breakers (SSCB) due to their fast functioning capability and high controllability levels. For quick fault detection two distinct techniques were selected. The first measured the distribution line’s rate of change of current while the second technique determined the current magnitude by measuring the on-state voltage across the SSCB’s semiconductor device. The complete design of the fault detection circuits leading to isolation has been presented in this research work. The performance of both the designed detection circuits and fault isolation via the SSCB have been validated through practical experiments. The results demonstrated that isolation of the fault subsequent to its occurrence is achievable in just a few microseconds. Hence, this implies that the fast rising DC fault currents can be detected and interrupted in adequate time prior to resulting in any hazardous consequences.