Loss of one redundant group – DP undesired event

Comments from the report:

A partial blackout of the centre high voltage (HV) switchboard at 11.04am caused by No. 2 generator.  This caused the loss of the 440V distribution board and thrusters No. 3 & 6.  The centre generator No. 1 started and connected onto the switchboard, there was no loss of power to the drill floor as this is fed from both port and starboard HV switchboards.  The power management system worked as expected, investigation found a poor connection to the temperature sensor of No. 2 generator causing the temperature fluctuation.

There was no loss of position.

Considerations of the IMCA Marine DP Committee from the above event:

  • With the loss of one redundant group DP amber alert should have been activated.
  • The system reacted well to the loss of the centre switchboard however it was felt worthwhile to highlight the configuration in this case. The vessel was operating with one generator on each of the three switchboards.  Therefore, it was accepted that if one generator failed then one redundant group would be lost.
  • It is important that DP personnel are fully aware of the situation and recognise that there could be a degree of risk as the switchboard is brought back on line.