Chief MAKOi | NTSB Update on Dali: Undervoltage Release?

The NTSB has given an update on it's ongoing investigation into the Dali incident in Baltimore which caused the Francis Scott Key Bridge to collapse.

Chief MAKOi
Seaman Vlog

[greyjay]

A straightforward explanation, along with a demonstration. Well done, Chief Makoi.

[brucetheloon]

That the NTSB has pulled the terminal block and the wiring suggests that the undervoltage sensor is fine, but corrosion or a loose contact led to an artificially low voltage causing the sensor to open up. The Wago terminal block mentioned in the report and pictured above is a sprung contact block and not a screw block. The wire is bared to a specified length, secured with a bootlace ferrule if it is multiple stranded wire instead of solid and then shoved into the terminal block so that the spring grips it tightly.

Failures modes on sprung contacts include weakened springs, incorrect wire thickness for the block, insufficient length of bared wire pushed into the contact and using aluminum wire without the corrosion inhibitor paste required. It's normally hard to pull the wires back out once properly inserted, needing a tool inserted to open the spring a bit, but if the spring was weakened, it may happen.

It is difficult to spot problems on terminal blocks like this, the contact point is covered by plastic and a wire that wasn't bared sufficiently still looks like a properly inserted wire. Regular measurement checks with a multimeter while under load at all junction points on the detection circuit is probably the best way to ensure these circuits are good. And a pain in the butt.

[steveurbach]

What is not made clear to the public is Why you want a LV (AKA brownout) trip. Motors and other equipment are designed to run at a voltage range. to low and a motor may stall and burn up (or fail to supply the reason it was there: Lube Oil, Cooling...), Modern Lighting has electronics that stop working below a certain point. OTOH the old Incandescent bulb just dropped to a ruddy glow with no damage.
But the most important reason for a trip is to prevent the good LV voltage bus (if they had been paralleled) being dragged down by one going bad.

[jeffdayman]

Thanks Chief for your insights! Cheers.

[Tenright]

Thx Chief, Nicely Done. Hopefully the NTSB will come out with a furtive service letter
that will avoid another incident, and Loss of Lives.
Certainly the insurance entities will want a solid answer due to their coverage losses.

[stevecunningham]

Thanks Chief for your straightforward analysis!

[benjurqunov]

Thank you Chief !
Being an industrial electrician, I understand it can be a simple trivial thing that shuts down critical machinery.
Plus a dilligent inspection program finds small defects early to correct before a major failure.

[parkerholden]

Good explanation Chief. Several things could cause low voltage at this #1 Transformer besides the UV relaying tripping.
You are the only one on YouTube who actually knows what you are talking about.
At this time the evidence points to a load share problem that resulted in one generator motorizing.

[Ruthhql]

Thank you! Trying to understand all of this with limited electronic knowledge! I just find it interesting and I like to learn!

Thank you Chief Makio for posting this interesting informative update on this accident

[rosshammond]

Thanks chief, you are one of the best, I like all of your videos and how you explain all about ships and shipping

[GavinY]

Had this happen in our power plant, generating 720MW to grid and whole plant trips, about 10, 000 alarms and event list, all controllers went down without reason.

Turns out a terminal block was loose for power supply to controllers, they were spring type. Eventually with a thermal camera, more were found when they were hotter than the rest

[matthewheide]

Thank you Chief Makoi for the root cause analysis that will help us prevent this in the future.

[ypaulbrown]

thank you Chief, love your channel....cheers from Florida, Paul

[chuckyc]

Thanks for your straight forward explaining

[WilliamYoung-jv]

I always enjoy the Chiefs explanation of the ship’s systems. A am amazed how many and how complicated the systems on a large ship are.

[nvragn]

Ty Chief always a pleasure on a Saturday morning. I love how you make it so we can understand what is going on 👍🇨🇦

[paullandreville]

Thank you for putting this in layman's terms. Keep up the good work Chief.

[walsakaluk]

Thanks for the update Chief!
Some primary power control design changes may be coming to critical plant near you (us) soon.

[blocka]

I was in the Electrical Trade industry for forty odd years (Marine and Shore based) and I can tell you that this type of connector is not really suitable in high vibration areas (just my opinion). Old school, but I much prefer to screw down on a conductor. Also found in many locations that the installer using ferrules to terminate the cable neglected to actually crimp the ferrule, relying on the connector to do that job. Thank you Chief for your report, you bring back many memories.