A new report from the National Transportation Safety Board (NTSB) suggests that a loose wire aboard the container ship Dali may have caused the blackout that led to the ship crashing into the Francis Scott Key Bridge on March 26.
According to the report, HD Hyundai Heavy Industries (HHI) engineers discovered that a loose cable connection at node 381 in the control line led to the accident. This loose connection could cause a power interruption to the HR1 UVT coil, resulting in an undervoltage trip and a blackout of the 440V switchboard.
When HHI simulated the disconnection of the cable, the HR1 relay opened, causing a blackout of equipment powered by the switchboard. The power was restored after 10 seconds through an automatic transfer, confirming the issue. The results aligned with the engineers’ expectations, leading to extended monitoring.
To remind, according to the NTSB preliminary report, electrical breakers HR1 and LR1 unexpectedly opened when the vessel was three ship lengths from the Francis Scott Key Bridge, causing the first blackout to all shipboard lighting and most equipment.
Regarding the cause of why the breakers DGR3 and DGR4 tripped (opened), leading to the second blackout as reported in the previous NTSB report, do the NTSB and Hyundai have any findings on this?
The fact that both the low side and high side breakes tripped is significant..Other significant factors include the previous trip outs prior to the accident. Another significant factor is that very few ships crews understand or even know about the load share scheme between multiple generators. ( if there is any) This is often hidden from the crew Another significant factor is that the electric load was many refrigeration compressors capable of back feeding the two tripped breakers. This all adds up to a case involving a motorized generator.
My comments are based on 40 years experienc with shipboard electrical systems as a field service engineer for a major manufacturorer
(Parker Holden) I was wondering the same thing as there seems to be a information blackout. The control circuitry schematic would be of benefit for transparency. It maybe complicated/technical enough to confuse the investigators and does Hyundai claim that kind of disclosure would be proprietary information? The investigation needs serious oversight.