In its investigation of an explosion and loss of propulsion aboard the RMS Queen Mary 2 Britain’s Marine Accident Investigation Branch warns that protection systems for critical equipment must ‘fail safe’, and should be thoroughly tested at regular intervals to prove that all sub-components are functioning correctly. In particular, harmonic filters with current imbalance protection systems should be thoroughly checked by a competent person at the earliest opportunity.
Investigation of the catastrophic failure of a capacitor and explosion in the aft harmonic filter room showed that the protection system for the harmonic filter did not work. As a result the vessel blacked out and was without steering or propulsion for 30 minutes. There were 3823 people on board.
Says MAIB: “there is a need to improve the awareness of the potential risks of high voltage harmonic distortion and arc flash… Awareness of the damaging effects of harmonic distortion needs to improve throughout the marine industry as the risks to equipment caused by harmonic distortion are likely to increase significantly as variable speed AC electric motors become more widely used in ships”.