Harmonic measurements on ships and cold-ironing

Abstract

Electrical power distribution on ships is similar to land based systems. Harmonic distortion is prevalent in both systems and equally detrimental in the modern era. It is important to understand and investigate the effect of harmonics on a ship’s Power Distribution System, when at sea, especially if the ship uses modern electronic variable speed drive (VSD) technology to control its electrical propulsion in conjunction with other electronic switching devices, such as, uninterruptible power supplies (UPSs) and switch mode power supplies (SMPSs) as they are responsible for voltage and current waveform distortion. Further, in the modern era, over 90% of the world’s global trade goods are transported on cargo ships and environmentalists are expressing great concern at the volume of greenhouse gas being released into the atmosphere by ships. A need has thus also arisen to investigate emissions when ships are “coldironing”. This is the process of providing electrical shore supply to a ship that has docked or berthed in a harbour while its main and auxiliary engines are turned off to decrease emissions. This paper thus investigates and analyses the harmonic distortion levels on a ship using a measurement based case study research approach taking before and after an upgrade to a mining ship’s power system into account. The paper also looks at the need for coldironing by considering the emissions produced by docking ships. Recommendations are made.