Catastrophic failure of capacitor in aft harmonic filter room on passenger cruise ship RMS Queen Mary 2

Location: Approaching Barcelona, Spain.

Accident Investigation Report 28/2011

Read our marine accident investigation report, which includes what happened, actions taken, and recommendations:

QM2Report.pdf (4,491.12 kb)

Annexes (5,366.76 kb)


At 0425 on 23 September 2010, as RMS Queen Mary 2 (QM2) was approaching Barcelona, an explosion occurred in the vessel’s aft main switchboard room. Within a few seconds, all four propulsion motors shut down, and the vessel blacked out shortly afterwards. Fortunately, the vessel was clear of navigational hazards and drifted in open sea.

Safety issues

  • it is likely that the initial degradation of the capacitor was due to one or both of two anomalies: being subjected to voltages in excess of their design rating, or being exposed to frequent voltage transients due to increased number of switching cycles. Instances of failure initiation due to minor manufacturing anomalies, though less likely, cannot be completely ruled out

  • certain engineering systems could be pressurised under abnormal operating conditions. The inherent hazard of internal pressurisation of harmonic filter capacitors, and the sudden and uncontrolled release of pressure energy from them was not considered

  • the capacitor explosion could have been prevented if the current imbalance-based protection system was functional. The protection system was not designed to fail safely; it is possible that the failure of its transformer remained undetected for several years. There is no evidence of the protection system being tested during the service life of the vessel


Lloyd’s Register (Europe, Middle East and Asia) (LR) has been recommended to take forward proposals to the International Association of Classification Societies to:

  • establish a requirement for all new vessels fitted with harmonic mitigation equipment to model the effect of its loss and provide data to crew so that appropriate corrective action can be taken in such circumstances

  • require on-line or periodic monitoring of harmonic distortion of voltage on all vessels with high voltage power systems to give early warning against potential problems

  • develop requirements to detect and mitigate against the failure of high-energy storage devices and to ensure that protection devices of critical items are fail safe

LR has also been recommended to review its rules on the use of water-based fire-fighting systems in areas containing high voltage equipment and to work with the International Association of Classification Societies to propose appropriate guidelines to the International Maritime Organization for inclusion in the International Code for Fire Safety Systems.

The Maritime and Coastguard Agency has been recommended to produce specific guidance regarding the harmful effects of excessive harmonic distortion in electrical networks and to update the Code of Safe Working Practices for Merchant Seamen to raise awareness about the hazards of arc-flash in high voltage equipment.

QM2’s manager, Carnival UK have also been recommended to: improve the standards of protection against the effect of harmonic distortion and component failure; and, to review the machinery alarm systems fitted to QM2 in order to identify and prioritise those alarms which indicate failure conditions that could significantly affect the safety of the vessel.

This report was published in 22 December 2011.

Published 23 January 2015