Did This Part FAIL Cause MV Dali Key Bridge Collapse? (2024)

From my reading it isn’t that an undervoltage condition existed; rather that the circuitry to detect an undervoltage condition had a fault that caused the breaker to trip when it should not have, e.g. no undervoltage condition existed.

Control voltage has nothing to the 6600 or 480. Low voltage typically is 24v that used to control the high voltage devices. That terminal block looks like a low voltage or control voltage terminal block. Usually less than 30amps at 24 dc volts

"Low Voltage Release" is a common feature of power circuits that will automatically disconnect the loads from a bus when the bus is lost. The idea is if the HV bus is lost, you want to trip all the loads off the bus so when you re-energize the bus you're not overwhelmed by all the loads still connected.
But if the control circuitry 'senses' a low voltage (due to faulty connection) even when the bus is operating normally, would 'trick' the breaker into thinking there was a voltage problem and trip the HR1/ LR1 breakers.
I remember an incident at work where we had an emergency diesel start unexpectedly. It was caused by a blown fuse in the voltage-sensing circuit so the engine controls 'thought' there was a loss of bus and started. Fortunately it didn't try to energize the bus (which was still energized from main power) because the breaker controls used a different voltage sensing circuit.

I’m so glad you enjoy making these videos…
*…because we (the viewers) really appreciate watching them so much!* 🙂
You really dug deep… even using an AI image search to find the part!!! 🤯
Who else would even *think* to do that???
And who else would explain this thing so well to us laymen?
Nobody. 😒
I’m really thankful I’m subscribed to your channel so I can keep up with whatever’s next.
🙏

14 years of mechanic working on cars full time, I've seen some stuff. The thing with connectors is much the same from old to new or a terminal block on a ship. They rely on clamping force and making good conducting contact with the male and female part. Corrosion and oxidation can hamper conducting contact. But vibration/movement will cause friction erosion, removing material and lowering the clamping force. Metal can bend and you have a loss of clamping. With a loose male part in a female part you can still lean to one side and make good contact but it can also move away and not have contact. And thus you can not notis a 1ms non contact moment but sense circuitry is going to trigger of the non contact moment is long enough. Sadly the 1 wire at the wrong time can cause Dali to collide with the key bridge by opening the breaker contactor.

As a non-engineer medical equipment mechanic (retired) I enjoy your depth of knowledge and your attention to detail. Thanks.

Hi Jeff thanks for the great video. I work in the railway signalling field and we use WAGO terminals extensively, even the exact same 2.5mm2 terminal that the NTSB has shown. WAGOs are one of the best terminals one can use and the main reason is that they are vibration proof. Since WAGOs were introduced in the railways, we seldom get any faults as a result of vibration which is a significant factor adjacent to a railway line. HOWEVER, there is an achilles heel and this is down to competence and training.
If your video, the WAGO film clip shows one type of terminal where the cable core is pushed into the cage clamp. The other type of terminal (aka the NTSB photo) is where the cage clamp has to be pre-opened and the wire inserted. This is where the the achilles heel comes in. WAGO provide an insertion tool which is made specifically to open the cage clamp to insert the wire. You are also trained to ensure that the wire is stripped to the correct length so that when it is inserted, it fully engages with the clamp.
The problems start when a person does not have the correct tool and decides to use a flat screwdriver. The problem gets worse, when a person decides to use an electrically insulated screwdriver. This is where the shaft is insulated and only the tip of the screwdriver is exposed. So what happens is that the screwdriver is inserted into the WAGO and the uninsulated part goes into the clamp but butts up against the insulated part of the screwdriver. This prevents the cage from opening fully.
So when a mult-stranded cable is inserted, especially a small 2.5mm2 type, it does not fully engage at all and nominally a couple of stands may be lucky enough to be clamped, but the rest contribute to a loose terminal connection.
When we first stated using WAGO's, loose wire terminations was a major problem and only through on-going training and ensuring the right tools were used was this problem eliminated. As I have already said, once correctly terminated, you never need to check it again - maintenance free.
Certainly going to be interesting reading the final report, but I will put a wager on that this was the root cause. Keep up the great work.

Thanks for your continued analysis of the Dali disaster. I have worked on alot of power systems with DIN track stuff, and in this case I am guessing the breakers are shunt-trip types that are activated by the control system, of which the WAGO DIN terminals are a part of. Personally I much prefer screw-down terminal strips, as the pressure contact ones can be damaged by improper insertions and especially removals of wires. For instance, to remove a wire, you insert typically a small flat-blase screwdriver in the release slot, and then gently pull the wire out. Maybe someone didnt have the release pushed all the way back and just yanked hard on the wire, deforming the spring contact. Or maybe stranded wires were partially bunched up and not fully inserted. Assume this might be what NTSB is looking at. As for alminum wiring, theres no way that could be present in a ship. We dont even use it in data centers due to the corrosion potential.

A loose connection in the control circuit would be my guess. I’ve seen loose connections cause I2R power losses. This causes a voltage drop across the terminal and sometimes lots of heat that will melt the terminals.
It looks like the blocks are rated for 600vac. Could have been used on the LV side of XFMR or in the control circuit. If in the LV side the I2R issues would cause the voltage to trip depending on the LV connection location.

Keep in mind that the electrical diagram used to illustrate the first NTSB report is neither a wiring diagram nor a schematic. What is shown as a high voltage breaker is actually a set of detection circuits operating a contactor. Each of low voltage, high voltage, no current, or excessive current could cause the control circuitry to open the contactor. In fact, there could easily be separate low voltage detection for each side of the contactor and also for the other side of the transformer. Most of these kinds of control circuits are designed to fail safely. And for that reason any fault should open the contactor separate the load from the power source.
A home breaker panel doesn't do any voltage monitoring for the ordinary thermal breakers. Those only protect against over current.

I've repaired many plugs in houses near the beach where the connection to the plug were through the push in connectors in the back of the plug. Even if copper wires were used in these connections, corrosion could occur in sufficient quantity to make the connection fail especially in a salt water environment

Sounds like an intermittent loss of power to the UV relay caused a protective action to protect the transformer. Could be as simple as a loose connection.

x navy, 40 yrs. as IBEW wireman, used many of this type blocks, nice pc.. My question is what idiot would spec AL wire on a water craft of any type and most of all on a ship used in salt water? One other point is you have redundant systems, in situations like this why wouldn't you have both systems up and running, you run into problems your tie breakers could dump the problem and you would be backed up with NO interruption. The mode they were in takes minutes to spool gen sets and sync up, time they didn't have. The whole thing stinks!

OK, An undervoltage release coil is designed to be powered at all times. If it loses power, it will release it's plunger to operate a lever. This lever will release a spring which causes the breaker to trip. A momentary loss of voltage will cause the breaker to trip and unless there is a method of recording what the particular control voltage is doing, there is no way to tell what caused the trip.
As to what caused the momentary drop out of the control voltage, there are any number of things. With the Terminal alone, I can think of three or four alone. The cages could have failed due to age or metal fatigue (they are only about 1mm thick). There could have been corrosion due to the sea air reacting with the copper wire or cage. I have yet to see a control panel wired with aluminium wire but for runs between different boards it may have been used. There could have been a hot joint which heated the cage or even started to burn out the terminal.
I noticed that the photo in the NTSB report is taken from the a catalogue showing dimensions. The terminal in question is also designed to have a small screwdriver insert to lever open the spring cage before inserting the wire and then releasing the cage to hold the wire against the clamp body however if someone was to really put pressure on the screwdriver while opening the cage it could bend the cage itself which would cause less force when holding the wire.
That said, the terminal may only be the first component in the control line when tracing back from the breaker. There could be an old fuse further back, a faulty control power breaker or any number of other components...
The downstream breaker most likely tripped due to the upstream breaker tripping. For HV/LV setups like this, it is recommended that the HV breakers do not CLOSE onto a load. so the control circuit would have most likely opened the downstream automatically.
Why the crew did not close HR2 & LR2 instead in case of problems with TR1 will also need to be looked at as a failure in operation. Doing this MAY have prevented the second blackout.
Regards

Was just thinking about Dali today. Thanks for sharing the report Jeff.

Interesting that they isolated this one part and sounds like associated wiring with it. Thanks for the video.

"an interruption in the control circuit for HR1’s undervoltage release." surely suggests an intermittent circuit in the CONTROL circuitry of that system. In other words, they've taken away that connector block with the connected wires to flex them, shake them etc to see if that was the cause of the "interruptioon"

Per usual, great explanation that even a layman like myself can understand.

Very early on, from either the news or RUclips, it was mentioned that refrigerated containers were connected to the power system and there may have been in-port power issues. Would it be possible that the overall connected load (ship systems + auxiliary loads for refrigerated containers) caused the upstream breaker to trip? Great spot on the WAGO connectors. One would assume that all electrical components would be approved for marine use (you mentioned vibration). The control wiring would likely be insulated, stranded, 12-16 AWG THHN-like wire. One would hope the WAGO push-in connectors were approved for stranded copper wire if that was used.

I use those Wago terminal blocks every day. They are the best in the world if used correctly.

That's pretty bad if this is the culprit. What do those terminal blocks cost, $5 if you order a box of 100? So $10 worth of some wire and a terminal block caused many deaths and billions of dollars of damage

In my system engineering work I've used Wago parts extensively including similar din rail modules like the one pictured. They are well made and reliable. They are potentially useless if you do not properly tighten the screws. It is possible to tighten the screws down without being on the conductor(s) you want to secure. If the control circuitry for the buss breakers was intermittent it could be perceived by the system PLC as a low or no voltage and drop the buss connection. 😮

Jeff! I'm surprised. You should know that shipboard engine rooms are constantly hosting low level vibrations do to the running machinery.

Apparently they had power problems whilst loading reefer containers that drain a lot on load on the generators. I wonder if engineers onboard when fixing the problem of losing power ashore did something wrong or did a quick fix by bypassing certain electrical components to prevent power tripping. Not an Engineer just speculating.
As a previous person commented I still would like to know reason for a lot of smoke coming out of funnel from ship when power regained. I still feel that if ship had power problems whilst loading a proper investigation of root cause should of been made before departure. Maybe it was then I am incorrect. As an ex Captain on big ships there is a lot of commercial pressure placed on Captain of ship to sail on time to keep to sailing schedule. This is the dangerous part of shipping nowadays because often commercial pressures overrides safety concerns. Another assumption I am making is that maybe Chief Engineer and Captain were aware they had small problem onboard but thought it had been sufficiently fixed without having time to find out what caused problem.

I am an electrical engineer with 30 years of electric utility work experience. The 6.6 KV bus was energized and the two generators were tied together before the power failure. First, Synchronization and voltage considerations were not a factor before the event that caused the trip. In utility systems, we have electromechanical devices that leave a target indicating the tripping current path by a sensor. IE. low voltage, high voltage, over current, under current, change in frequency, bus fault, transformer fault to name a few that come to mind. When a breaker trips there is a lock out relay that has to be reset before the tripped breaker can be closed. Forcing insight and investigation as to the cause of the trip.
I would think on a large commercial ship that the protection scheme would mimic a utility system. From what you are saying a bad electrical connection on sensor wiring sounds reasonable.
Also, from what you read, I believe the 6.6 KV bus was never tripped or lost. Which begs another scenario, the opposite breakers and transformer should have energized after the initial trip. ????????????
Again, it is never a good idea to reset a lock out relay and close a breaker without investigating the cause.

I am a retired ME so I am not as familiar with the ship’s electrical system. Another RUclips that is authored by a chief engineer on another ship provided a more complete electrical diagram (not from the Dali), which helped me understand a bit more about the ship’s electrical design. The majority of the ship’s mechanical equipment are powered off of the 480 VAC circuit. The notable exception is the bow thruster and the main ship propulsion. The bow thruster was not in use as it is only used when leaving a dock. Of course, the NTSB has the actual ship’s as built drawings and the maintenance records that they will be used to zero in on the failure. I’m wonder if the main generators may be the cause. Time will tell.

Great explanations... thanks for sharing.

Pictured is a 3-pole or 1-to-2 wire expansion IEC terminal block. It clips into a rail, called a DIN rail, with other IEC terminals or any number of other components - it is a universal mounting system.
Over the years, I have used many thousands of IEC terminals of various sizes and configurations in the construction of industrial machine controls panels.
These terminals are typically rated at 300 to 800 Volts depending upon size and design. What is not shown on the drawing is the current rating in Amps, which determines the current rating in Amps.
The wires are attached to the terminals by one of two ways: A convoluted flat spring which is opened with a tool resembling a flat-blade screwdriver inserted into a hole at the top of the terminal for wire insertion/removal - or a screw & clamp terminal.
The drawing shows a spring-type terminal. The idea behind the spring terminal is rapid connection - push down on the insertion tool through the hole in the top, insert the wire through a corresponding hole, then remove the tool. You may imagine that the screw terminal takes more time and effort to make a connection.
But I prefer it as you can get a tighter more reliable connection with more contact area, particularly when ferrules are used on the wires (to avoid split strands or breaking strands) which is always best practice.
So what could have happened? This block would be in a low-current control-related circuit - with this block likely being rated at 8 Amps - but we don't know for sure (a width dimension is not shown in the drawing). If corrosion occurred between the spring or contact pocket, high resistance would develop creating heat in the joint. This could anneal the spring, making it lose pressure on the wire, causing an intermittent connection.
Only The Shadow knows for sure.

Jeff, you are wrong to call them "breakers." They are really CONTACTORS, relays, in other words,(not thermally operated circuit breakers) that are controlled by electronic circuits that monitor voltage and current conditions. It's the electronics that may have been at fault.

I have always figured that most of these old ships have gremlins in their electrical system. As these ships live in salt water conditions, I bet they have some wear and tear in those systems. Great job Jeff.

Thanks Jeff

A number of comments here have speculated that the harsh salt water environment may have caused corrosion of the electrical connections. If that is a hazard, one would think that an environmental management system would have been in place in the electrical control room.

breakers open because something is wrong

Long time ISM was implemented in the shipping industry to avoid accidents. Whatever technical failure happens onboard ISM must following to avoid major accident.The purpose of investigation is to find out if the ISM had been followed but not the electrical terminal

A difficult problem to troubleshoot quickly in the dark.

30 years as a marine engineer, 10 of them as a chief engineer. NO ONE would ever use aluminum wire on a ship. Not even silly Naval architects with PhDs. The ship was 20 or so years old with constant vibration, heat, and salt air environments progressing something called entropy. Everything decays and goes back to nature. Given enough time (another 60 years), the bridge would have fallen on it's own. What I am getting at is that "man" cannot control everything all of the time. I would bet that the low voltage trip was because of a computer or microprocessor error.

Good work Jeff, many thanks.

Ships were designed to survive individual part failures. That one was operated incorrectly.

The (dis)advantage of uncontrolled automation. They saved one sailors wage and lost a ship, a bridge and some cargo.

I guess no one was recording any power quality during this event. It would be nice to see if there were any major events. I would run the generators for 24 hours, while recording the output data. It feels like the human factor is greater than mechanical failure.

These power clamps are intended for rigid cables.
But I don't think it's right to have rigid cables in a ship.
Think about the vibrations on the ship. These do not appear in the house.
However, flexible cables can be used with core sleeves.

I'd be surprised if a spring type connector is used for anything more then 1 amp. They do make constant contact & don't loosen up from heat cycles, but don't ever make good contact on stranded and/or large wire.

How does it knock out the entire system? Is the electrical system not redundant? It sounds like there is more to this story.

Failure to use a ten dollar tube of Alu-Plus Contact Paste resulted in the loss of a billion dollar bridge. That's what I call leverage!

Love how you just have a circuit box hanging around

The cage clamp design IEC terminal block should have never been approved in favor of the NEMA screw terminal. Wake up DNV... German engineering!

As the voltage drops the amperage increases.
Watch a car with a bad battery as it turns over and you can hear the starter slow because of the battery the cables will start to overheat, the slower the starter turns the engine over the higher amperage demand on the battery.
A 20-amp breaker trips when there is a short or when the amperage exceeds 20 amps.

Equipment can do crazy stuff. This has nothing to do with this case but I worked on a reefer ship where its DC generators would reverse their polarity.
To cool the two hatches we ran three generators, Two MANs and a Detroit diesel. The MANs would reverse their polarity and turn the Detroit diesel into an electric motor by stopping it and turning it in reverse. An older engineer told me that he had seen connecting rods burst through the sides of an engine when this happened. Luckily that never happened to us.

According to the VesselFinder App, Dali has been moved again to the next port. Maybe now the ship's repair work start.

Nobody in their right mind would use aluminum wire in this situation. That said, if the insulation of the copper wire was stripped to less than the spec (.31"-.35"), it is possible that the insulation could interfere with the conductor to terminal connection and cause an intermittent connection especially under vibration. (BSEE '67)

Jeff,
You need to think of LR1 and HR1 in terms of their being relays and not so much as circuit breakers. The relays act more like switches linking parts of the buss bars.
I believe the components you were showing were from a low voltage breaker. M/V Dali was running a 4500ĶW and a 4000KW generator. These are 6.6 kV machines. The current ratings are about 618 and 600 amps. Bus ties will consist of multiple large copper ɓars, similar to 6 - 3" high by 1/2" thick. Special tools and protective clothing are required for 6.6KV work. I would be very surprised to see aluminum wiring used. IEEE 45 code, in 1997, even banned the use of aluminum for protective weave on cable in the shipyards. I have never seen "click" connections on ships. Considering size and the use of multistrand wire, I don't believe "click" connections will work.
There are two distinct, but highly integrated being discussed. The Power Distribution System (PDS) is known to most as a one-line diagram. The Power Mananagement System (PMS) is the computer system that integrates all the machinery and electrical equipment making it possible for the ship to run. You could have a faulty PC card in a relay causing it to trip. Or, you might have a glitch in the line code of the PMS sending an incorrect value causing the relay to trip.
In 1997 USCG rules required that you parallel generators using three lights. When the patterns matched you could close the breaker. We found it to be close to impossible using the lights. Too many variables, far more complicated systems. The lights remained, but we didn't have to use them.
Bob

The most likely thing that would involve a terminal block is a loose connection. Loose connections are a lot more common with those than design flaws in the terminal block itself. The protection circuit is probably wired to be fail-safe where any break in the connection (normally interrupted by logic operating a relay, maybe logic directly, or a red mushroom button) - and a loose connection can also break the connection. Loose connection is also more likely to be intermittent. A protection loop shouldn't normally see very much current, so it shouldn't be seeing a lot of thermal cycling. But a ship is a big vibrating environment that would have a tendency to cause connections to loosen up. On connections with current going through them - you can get an early indication of the failure with thermography as the interface heats up due to increased contact resistance as it loosens up. (conversely - if there is not current, or not very much current going through it then it won't be generating enough heat to show up that way). It is difficult to scope and manage a maintenance plan to "go tighten ALL electrical connections" - but there are maybe a few ones that are important enough to have regular effort to check on them. Hard to say if this system would have been included in something like that - easier to deprioritize it because there is a redundant path.

Thanx for this information ... the details make me dizzy ... does any of this explain all the black smoke ... that comes from poor air/fuel mixture ... how does that effect voltage? ...

I'd be curious to see schematics and a functional analysis of how Dali sync'd generators. With 4 to use in different combinations, that has to be more complex than just a single pair master-slave design with reduced capacity fallback to either one.
I'm a fan of Amp PIDG spade lugs, with MIL-39012 oxygen free crimps and insulation retention. Not as easy to wire as those Wago blocks.....
Aluminum in a marine environment? Hydrogen replaces Aluminum in an electrovoltaic series, whereas copper replaces Hydrogen. IOW, even without a salt environment water over time can make Al wire turn to mush of Hydroxide flakes and powder. Why risk No-Alox or other brand equivalents?

I installed water heaters for 20 years and one sub division I worked in every house had aluminum wiring and I used that paste religiously 👍🇺🇸

Ouch, so faulty control wire connection caused a remote trip of HR1? Insane how such a small piece caused such a large disaster. This could have been a sense wire.

The bridge collapse was entirely caused by the failure of a requirement to have protective 'dolphins' that prevent contact between ships and bridges, which are legally needed on all bridges in Europe where large ships traverse channels with major bridges.

Go back to your NTSB report video. The ship had the same problem at port resulting in power loss, low voltage causing the breaker to trip. There was either a problem with the generator or the breaker.

Electricity in a marine environment needs also particular attention, with the humidity and salinity. This can corrode stuff big time. Some equipment might be suitable on-shore, but not on ship.

Ships of that size don't "bounce around". Too much mass. There'd be some vibration worth consideration around and above the engines and possibly the prop shaft. Could be a concern depending on how and where the electrical cabinets are installed.

next question....Wago connector or chineese wago look connecter?????

This point is tiny, minutiae, a fly. Almost nobody has mentioned the utter absense in either of the two original night time videos of big waves following the big collapse and big splashdown. The second video has audio but not a single sound is heard from the massive, heavy bridge collapse. It's eerie. Linked from the 90-part series on the many anomalies of the BKB event -- it's on the ORGanization (not the COMpany or NETwork) site called "CON" followed by "S" then "P" and with an "IRA" on the end.

Exactly, fault detection control interlock circuits. Wire terminations are made by WAGO among others. The protection circuits just perhaps thought something was wrong...

I am still laughing at Lara Logan claiming the GPS was spoofed. And her claim that she learned that from undisclosed sources. OY!!!

Under voltage protective relays are normal in any power distribution system to protect equipment from damage. Wago push type terminals are notorious with working loose or over heating from current. Poor craftsmanship like not stripping wires right length, broken conductor strands and how far the wires are inserted all play a roll. Sometimes, it's takes years to show up. I've seen first hand how hard problems like that can be to track down as the connections cool off and read good on the ohm checks but under load can go open circuit... Other factors like mech stressing the wires as a bundle on a movable door can lead to looses connection problems.

There were reports that the electrical system was overloaded by the number of cooling containers. Might this be a reason why the voltage broke down repeatedly?

I work with similar equipment on shore. Under voltage relays are all electronic.

A faulty 2 inch long component brings down a bridge? Who to blame? The US legal system will try to find somebody.

Push in connectors generally are not very solid, although people are speaking highly of Wago. The connecting wire could have been undersized. The voltage is actually very high. I think the diagram said 6,000 volts.

A bad WAGO spring loaded terminal block... Who'da thunk it? ;) The WAGO blocks are a breeze for building/assembly, but my experience is that in severe duty (heat/cold/moisture/vibration) they are notorious for intermittent glitches. I've chased a LOT of problems on industrial gas turbines that use these things. And they can be a double barrel bitch to find the intermittent connection!
Interestingly - The equipment I used to work on was equipped with WAGO Screw-on terminal strips. The same thing as you posted, but they had screw connections instead of spring loaded connections and ferrules.
The other possible problem with WAGOS of this type is when assemblers or technicians install wiring directly into the spring loaded connector. Using the wire directly on the spring loaded contact surface can reduce the contact surface area, and heat does what it does. After a while you have a nice flakey connection. That happens much less frequently with the ferrules.
Good report, Jeff!

There are multiple verified known failures in varied industries caused by "engineers" doing exactly what you cited not adhering to the published usage for electrical connectors,plugs,contactors ,and terminal blocks. many times the form factors are the same but the ratings vary within a series if parts. The Aluminum corrosion issue is well known in the electrical industrial arena. Will be interested to see what the final report says and will we reallyk now what failed?

It sounds like the low voltage detector was connected via that terminal block, and acted as an N/C switch, opening when a fault happens. That's considered to be a "fall-safe" design, since a false trip is considered to be less dangerous than failing to trip on a hazard condition.
Ironic. *_Very_* ironic.
Oh, and i wonder if whoever wired that panel read the fine print about it taking stranded wire. You have to use a ferrule on the wire or hold the leaf spring open with a small screwdriver while inserting the wire. (There's a slot on the connector for that purpose.) If you jam a stranded wire in there blindly without a ferrule, it will just bunch up in the hole.

Those parts have contacts which and if the wire is loose or the contact is worn can cause arcing and lead to the breaker dropping out.

Yea, it is going to come out that it is just some sort of fault in some part and nobody is to blame.
The real problem is that ships nowadays shut down the main engine and the controls when there is a power fault. That was not the case on older ships.

What's the differnce between required condition 1 and condition 3?

Ahh Wago I've used a few of them instead of wire nuts. Halo high hats had similar quick connect push in connectors. Much faster good for hot attics.

I didn't see any specs on those terminal blocks, but I certainly hope they were used on low voltage low current applications. Any type of electrical connection that is made with spring loaded contacts and not from clamping force from a bolt or screw is questionable at best. Personally I'm shocked this is even allowed on any ship, especially in US waters.

That is a passive terminal block, control wiring should have been copper. Wago has 40 years in the design of ghat block and i work with them a lot in new equipment. Most failures I see are installation induced, IE wrong wire size, no ferule, improper tools used in install or exceeding current spec of part.

Very interesting.

While getting to the exact source of he problem is important, what is more important to regulators and insurance people is did similar failures occur when the ship was in an open area and such a failure would have very little consequence. IF there were previous situations and the cause was not identified, that speaks to neglect. If this was the first time, it was at a most unfortunate time.

WAGO connector???
There is a big push to use those things on line voltage wiring in your home....everything from light switches to outlets use those silly things...I am now replacing 10 year old outlets due to overheating from these connectors....

WHARE are Dali's Anchors. The stearboard side anchor was dropped before the collision and ws no doubt cut loose so that the Dali could be removed from Key bridge. The port anchor appears to have been removed at some point. The Dali will need these anchors to put to sea, whrer are they?

I don't trust any terminal without a lug. Those spring clamps can heat up if the wire is too loose. That is why I refuse to use the quick holes, and I will put the wire under the screw because I believe that more surfaces are touching each other.

Low voltage protection - likely part of a check to make sure ALL 3 phases are 'up'. This isn't single phase gear here ...

Is this terminal block type approved for marine usage (corrosive environment) ?
Or could a wrong part have been used here ?

*WOW a Bridge destroyed by lack of paste? Or is it a bit of motion? Awesome video!!*

I did not know you were an electrical egineer too. Wow.

Everyone’s trying to keep this event on the front page, it’s done and dusted, the media have lost interest!

Undervolgae release its just a Coil (elektromagnet) inside breaker which trips(opens) breaker if the coil voltage is lover than 30-35% of nominal voltage. This coil is not responsible for monitoring bus voltage. To close and keep closed breaker this coil must be energised all time. So if there was loose wire in wago terminal which was supplying UV (undevlotage coil) then breaker will trip. Opening primary breaker will csause to trip a scondary breaker (also via UV) - UV coils are used very often in marine switchboards, simple way to ensure that power goes only from source 6600VAC to consumers 440VAC. Spring terminals are way better than screw terminals do not need of retaightenning after the time - but they have to be used properly. Most common mistake which i see is trying to insert 2 wires into single hole without proper double ferrule.

This is 'life safety' so you could ask the question 'why have an under voltage coil at all?' Usually anything that prevent the function, is omitted. If the volts go down the current will go up and trip on over current, eventually. Synchronised Alternators, also look doggy to me. A bit Heath Robinson!

a one line diagram is just the beginning, where is the control schematic and all the protective devices, CT's, PT's used?

In my opinion the contact area of the wire and the terminal contact is not sufficent to conduct the amps needed for the circuits.

im not a fan of wago style connectors there is such a small point of contact even when correctly installed

Please tell me they don't use aluminum wire on ships. (except for major high voltage lines) That combined with push-in connectors is a really bad combination. There is a reason they stopped using aluminum wire in homes.

The part is largely irrelevant. The underlying cause was a lack of well-engineered, no-fail, simultaneous, dual power supply to all critical systems that switches automatically or manually as needed. In other words, the same standards that have been applied to commercial aircraft for many decades.

That method of fastening a power wire to the block is crap! You need a proper terminal for power , like a screw down lug not the edge of a clip. Failure!

pretty sure that tiny DIn rail terminal/fuse isnt the part......should be some pretty big switch gear and breakers involved.

Hi Jeff on the day of the accident we had an big influx of plasma from our sun so the ground currents were elevated,so I am thinking that this might of tripped the safety switches on the boat . Just a thought. Things we cannot see are sometimes to blame.

You mention 3 things to sync the generators. 1. Voltage, 2. Phase, and then you again say Voltage for #3?

Phase sync on the two generators is certainly a requirement but voltage being exactly the same( is not required?)