NEPTUNE Power System: Detection and Location of Switch Malfunctions and High Impedance Faults

NEPTUNE (North-East Pacific Time-series Undersea Networked Experiments) is an underwater power and communications network for scientific experiments. It is proposed for the ocean floor of the Juan de Fuca tectonic plate in the Northeast Pacific Ocean. The backbone of NEPTUNE network is composed of fiber optic/power cable sections connected by switches in branching units (BUs). Spur cables extend from BUs to science nodes, powering and communicating with various scientific instruments and underwater vehicles. The focus of this paper is the detection and location of possible switch malfunctions in the BUs or high impedance faults on the backbone cables. The challenges are the fact that the voltage and current measurements are not available in the BUs, therefore the current differential algorithm normally adopted in a terrestrial power system for solving similar problems is not applicable. In this paper, the configuration of the NEPTUNE power system is first introduced and the challenges to system design resulting from its location on the seafloor are addressed. The proposed algorithm, which is based on the voltage and current measurements collected at the science nodes, is then explained and analyzed. Since all measurements in reality contain errors, the impact of random errors on the fault detection and location is discussed. It is shown through computer simulations on a simplified NEPTUNE network model that the proposed algorithm is effective and accurate