Chief MAKOi | NTSB Update on Dali: Undervoltage Release?
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- Опубліковано 28 чер 2024
- 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
A straightforward explanation, along with a demonstration. Well done, Chief Makoi.
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.
re: "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."
Add to the mix: We are talking 3-phase systems here WHERE loss or low voltage on ONE PHASE is a condition where all 3 phases should trip, as a 3-phase motor will draw a lot more current on the remaining two phases and is subject to burn-out at that point. Have seen it happen, to the point small copper balls (melted copper windings) were coming out of the motor.
Thank you for this. I was hoping he would explain this in the video because I didn't understand the why behind having a low voltage trip in the first place.
They are also used for safety reasons, i.e with machine tools - You don't want, say, a table saw spinning up automatically if the power is reconnected after an outage, some unsuspecting person may well be in harms way.
@@pinkmouse4863 This is a big deal. A lot of large power systems need to be started up in a particular sequence as well. You want everything open when the power comes back on.
@@alexcrouse Indeed, but I tried to give the simplest example I could. ;-)
Thanks Chief for your insights! Cheers.
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.
I have seen completely unstripped wire inserted into terminals - that’s something you learn to expect and check as a commissioning engineer (really bad workmanship (particularly on “spare” cores)).
Spring loaded connections do sometimes make connections by cutting through the insulation.
A thermal camera might help. *Might* (also might not)
So it's possible we lost a bridge and billions in damages because somebody didn't use enough anti corrosion?
JFC.
@@dsracoon On higher current circuit a TI (with a good Thermographer) would probably locate a delta T but the coil requires a very low current and I would not expect a delta T. I think the NTSB are barking up the wrong tree with the Wago DIN connection strip however the cable management and terminations may have been poor. I would like to see the Data from the Isolator/Disconnect unit as they would record V/A and trip data. I agree with the Chief's final statement.
Fretting damage due to vibration is also a potential issue. Excellent post. Cheers.
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
Oh boy what a day at work. Life's good, about to grab lunch, and bam! hell breaks loose "for no good reason". How long does it take to work through the alarms and checklists to get a tripped power plant back online?
If I had a nickel for the number of times it is some 50 cent part which brings a multi million Dollar operation to a grinding halt. The Apollo 13 Moon rocket disaster was something like that. My understanding is a relatively inexpensive thermal switch in an oxygen tank had been stress tested prior to installation. That brief test above specification was enough to cause a latent failure where the switch stuck on in flight, causing the tank to burst from over pressure. Suddenly all the DC and AC busses in the spacecraft started going down, leaving very little running. The situation says a lot about the meticulous training which allowed the astronauts to stay calm and methodical in trouble shooting as well as properly designed backup which kept communication with the ground running. Probably the importance of training to react to the emergency appropriately can not be under estimated.
Thanks Chief for your straightforward analysis!
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.
You are the man, love your channel.
Thanks for the update Chief.
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.
I am as well, in a paper mill. We actually have removed the undervoltage trips intentionally on a few of our main circuit breakers (Square D 800A) in order to restore essential services like lighting and control room power following a blackout. They get tested annually as well. Not always an option with a ship at sea.
Thank you Chief for your explanation
Thanks Chief!
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
I've been doing industrial electrics for the past few years and have had the misfortune of using these blocks more than once. One needs to push a screwdriver into a hole to open the spring grip, then push the cable in. Sounds great in theory but they're always a PITA and the spring mechanism can fail quite easily (I've experienced this)
I personally like the wago lever connectors, but I'm not at all surprised to learn that this style of connector may be the weak link which caused a trip...
The FIRST robotics competition uses a distribution block that uses wago-style connections. The kids never get the screwdriver in far enough to open the spring fully. So when they push the wire in, the strands always get smashed. It's quite the mess straightening out the strands. And they are surprised when you show them how much force it really takes to open the spring fully.
Thanks chief , you are one of the best , I like all of your videos and how you explain all about ships and shipping
thank you Chief, love your channel....cheers from Florida, Paul
Good explanation Chief. Several things could cause low voltage at this #1 Transformer besides the UV relaying tripping.
You are the only one on UA-cam 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.
A motorizing generator could cause that….but so could dirty connects on terminal boards in the wiring going to the UV coil. Sadly, I’ve seen both. Based on what the NTSC reportedly took from the ship, my thoughts are siding with dirty (therefore high resistance) terminal board connections. We will see what the final report bears out!
While sad that a low cost component caused an expensive and deadly tragedy, finding something mechanically wrong or faulty that is outside of the routine inspection and maintenance provides vindication for the crew. The fact that they have been treated like criminals and a municipal agency is trying to thrust itself into federal admiralty jurisdiction by detaining crew without the vessel being justly detained by an admiralty judge is criminal itself.
Jon Interesting case. Preliminary evidence strongly points to a load share problem We all know that voltage and frequency set points are on the switchboard for synchronizing purposes. What we do not know is where the micro adjustments to voltage and frequency based on individual generator load are. It is not uncommon to hide these micro adjustments off of the main switchboad ( in the voltage regulator itself and the governot itself.) This makes it impossible to manage load share short of the crew constantly tweeking the set points on the switch board. I have seen this poor design on many ships. Load share ratios will drift over time if not adjusted.
@@parkerholden7140 very true. What’s sad is that the crew has been criminalized from day one. Their own wellbeing was not even considered. We all know that all seafaring nations do not produce mariners at an equal level, and flag of convenience ships are normally run down and decrepit where you would more likely expect long term maintenance issues. At the end of the day I hope they are vindicated and the media has to eat crow, I would hate to end up in a foreign port and experience what they did myself.
Thank you for putting this in layman's terms. Keep up the good work Chief.
Thanks for your straight forward explaining
due to vibrations loose contacts may arc and metal will erode, best practice is to have strong spring loaded contacts , so that the contact will not be loose, to avoid arc and sparks
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.
And for all of this being part in a failing cascade sequence.
A fault (or series of faults) in any dynamic system will always find it before you do.
Thanks for the quick update.
Ty Chief always a pleasure on a Saturday morning. I love how you make it so we can understand what is going on 👍🇨🇦
this is a scenario, a land based person doesn't think about. since undervoltage is extremely rare in a grid system. but in a system fed entirely by local generators, I can see its importance, especially with the number of three phase motor loads. sustained undervoltage, or worse, trying to run with a missing phase, will let the smoke out of a motor.
now I'm curious, since it is a Wago component that is being examined, because Wago is getting a toehold in US electrical work, whether it was a failure on the part of the termination, or on the part of the conductor, or something else entirely.
Chief - Good explanation. As a retired engineer who worked in aerospace applications a question. I"m ignorant of ship board standards. Do ships use standard industrial controls or are they 'ruggedized' (for lack of a better term) in any manner? I believe most people realize parts used in aircraft are built and installed differently than lets say automobile ones. Just curious. Thanks and keep up the good work.
Thanks Chief! To the point and understandable.👍
Interesting they are using the UVR on the breaker itself on such a new ship and not microprocessor based relays. Microprocessor based relays have been the standard for a long time in the electrical utilities for many years. That's what I do, protective relaying for substations. Unless this is just one of the relays, since I would assume there is redundancy. But, intermittent faults can be hard to find! I have found intermittent faults that went on for 10 years in some smaller generating plants. Best part of the job is finding these issues.
'Trip' coils can be used for other purposes at the same time. EPO, Over or Under Voltage / Speed (the sensor causes the EPO rather than using that big red button) Our Data Center PDU had a large capacitor that was always charged, that provided the Trip current (the coil was not normally powered / cooking)
@@steveurbach3093 I prefer safety features that need power to keep the circuit closed.
One wire fault on that circuit and every single safety feature tripping that coil will be disabled.
But I guess it makes more sense in a low voltage setting like a data center?
@@steveurbach3093 The device he showed is a separate tripping device, just for under voltage. The trip coil is another coil and may even have two for redundancy / back up protection based on application. Capacitors for stored energy are usually used on smaller switchgear systems. Larger systems have battery banks to provide the tripping, protective relaying power, control systems etc...
. Not sure what this ship has, but would assume there is a DC supply used for the breakers, control and relaying.
The breaker in this video isn't the actual Dali breaker.
@@christopherg2347HV systems are almost always energise to trip.
They use high voltage batteries to drive the controls (usually 120 or 240V DC).
They generally prefer them to fail ON not off.
Interesting! My background as a marine generation and distribution system electrician has helped me understand some of this. Each connection point in a control circuit provides a potential failure point. While rare, it doesn’t take much for connection points or relay and switch contacts to become dirty, and end up behaving like a resistor. Something of this nature could have reduced the amount of voltage going to the low voltage release relay, causing it to trip its circuit breaker. I can count the number of dirty connection and relay contacts I’ve cleaned up, both shipboard, at home, or in my vehicles. Thank you for staying on top of this!
Thank you Chief.
👍👍👍as ever chief a brilliant understandable explanation.
A very clear and succinct explanation of the operation of a circuit breaker undervoltage release. I would never specify a circuit breaker with an integral undervoltage release. The problem with them (certainly the older type) is that you never know precisely what level of undervoltage has triggered the circuit breaker trip. When undervoltage protection is required I always use a separate, high accuracy undervoltage relay wired to the circuit breaker trip coil. In general, the more protection devices you employ to protect a diesel generator or its load the more likely you will have a spurious trip.
If the photo of the terminal shown in the video is the actual one from the circuit breaker that tripped then as others have poined out it is not a screwed terminal but a spring loaded one and although they can be durable and reliable they are also prone to failure by making bad contact if the cable is not inserted correctly or not prepared correctly.
I was a passenger on a Container Ship 10 years ago I was escorting special cargo from the US Govt and the cargo was locked up in a sealed area like a vault. The Ship lost all power and I mean everything. Day 4 of drifting and there was rescue on the way and it was a very hot summer I finally went into the Engine Room just curious about what was going on and they were using Portable generators for lighting and guess what I found by accident after a hour. There was a Tube that held wiring from the Battery Room and the Tube was discolored and not one idiot saw the color difference in this one spot. It had overheated. Engine room was clean but I saw that spot and I went topside and went to the Captain who was a total frustrated AH. I told him I knew how to fix the ship ad get it running and he ran me out with security. There was a storm brewing and tings did not look well so I went to the Chief and I told him to come with me. After 10 minutes it took to get there I pointed out to him to cut the Pipe, split it and find out the problem. He did it and what he found was a mess of burnt hot and ground wire cable that were not supposed to be there and they were melted. This was the main Cable to run the ship. The Electrician was dumb founded and they repaired this very thick burnt cable that has melted to the tube and wall of the ship. After repairs he went topside told the Captain to start the Ship and let's get going. It fired up but it was a manufacture defect in installation. He told the Captain I found out what happened and showed him. This could have caught the Ship on Fire and boy did I get a Done Good. I made the Captain apologize to me in front of the crew because he berated me so bad. The chief said if you did not see the discoloration of the pipe which was slight they would have never found it. We were 150 miles off course and in a dangerous situation. I got a Check from the Ship Company for 45,000 USD for my advice and the A$$H ole Captain got his butt chewed out for not listening to a common man. Little did they know I studied Container Ships when I was younger. My cargo was classified, and the US Navy had already diverted a Destroyer for escort to our location. I accepted the money.
Nice story. I saved the world once too, which is why we're all still here.
@@einfelder8262 glad you did
Thanks again for your great job 👍. Informative as always.
Thanks Chief, good succinct presentation. The report seems to be focusing on what might be a mechanical issue of failed connection at the terminal block, not the under voltage trip itself. It will be good to know the root cause so the condition may be prevented or corrected in other installations. The problem could affect many stationary and marine installations.
Thanks for this detailed and clear explanation.
Thanks Chief.
Thank for your assessment of what may have happened.
Very well explained. Maintenance history will be telling.
I had experienced a faulty electronics devices in the control console which give an alarm and hindered the main engine operation of a Capesize ship. I had reported the matters to our Japanese SI and he answered that my shop is New, yet I responded that your ship is New but this is the problem. When the ship reached in Rotterdam,a Technician came onboard to fix the problem, then the ship sailed to Japan. Later, when we reached Japan another Technician came onboard to replaced the IC components that was replaced in Rotterdam.
A nice update from someone who knows the subject matter.
Than you for the update, Chief!
Greetings,
Anthony
Great video brother from the imperial county California 👍🇺🇲
I don't like those wago connections. They get used the FIRST robotics competitions, and the kids always struggle to get the spring fully open and smash the wire strands. I personally prefer ring terminals. But you have to torque the screws down appropriately on those.
I don't like ring terminals. My 3 months old baby always struggles to handle the screwdriver
A spot of carbon between contact points can cause low voltage down stream circuit,
I liked that grin Chief when you said faulty wiring. Reminds me when fire marshals say it was caused by an electrical fire when the newer home burned . 😆😆😆👍🇺🇸😎🙏🏽✌🏻WISHING YOU FAIR SEAS CHIEF.
In my system engineering work I've used Wago DIN rail terminal blocks on numerous occasions. They are well made and robust. Unfortunately, you can tighten the screw clamps down without clamping the conductor(s) if not diligent thinking you were. If, as has been suspected, an intermittent connection might be considered by an automated switchboard PLC as an under/no voltage condition and open a buss circuit breaker to protect up and down stream equipment.
$0.02. 😮😊
Might be some weird corrosion too. Had the contacts on the bulb of an old car's tail-lights corrode off. The remaining contact looked "normal." You could not get any continuity if you only touched the end of the contacts, but the light bulb tested fine if you touched the sides of the contact.
The NTSB would be wise to hire you as a consultant expert in this matter.
Thanks
Clear and precise explanation thank you
Appreciate the information 👍
As a marine chief engineer I had experience with faulty UVR in a strange way, one of my generator ACB's was tripping while any voltage dip happened( like staring a heavy load like a compressor), after 1 week of testing and investigation we figured out that due to faulty UVR coil the breaker tripping way to early and causing that ACB to trip!
Fortunately that didn't cause our vessel to any accident, anyhow I'm suspecting the same here with DALI.
Thanks for the explanation and educating us.
THank you. Another great description.
I wonder how this ties into the electical problems before the ship departed, and the pressure on the crew to depart anyway.
Retired FPSO control systems commissioning, operations & maintenance technician here. Loose connections are invariably poor workmanship. ( And we've all done it.) The final check when working on any control systems wiring, and especially fail-safe circuits on critical equipment, is to give each wire a firm pull at the terminal. If you cant pull it out it's not going to fall out.
Can't argue against your comment.
Somehow, there was an "open" in the circuit.
But the open could have been within the coil (doubtful.)
Yep, your mechanical bonds must be confirmed good. I'm not even a technician and I know that much. What I would like to know is how often are mechanical bonds confirmed to be in good working order. It seems like this should be at least once a year.
@@user-dh6bj2me5p they removed the terminal and the associated wiring so we should assume they found an obvious fault in the terminal strip. That would have been something like a loose terminal screw, a weak spring terminal, a defective wire- crimp termination.
Another visual clue is the insulation is just a bit darker near the poor connection (We have all seen those that totally failed: charred or melted).
@@steveurbach3093 This is why one of the first industrial markets for Thermal Cameras is in maintenance. Parts almost always get too hot/cold before they fail which gives you a chance of fixing it next scheduled down-time.
As a retired USN Submariner the total loss of electrical power of a ship underway is unfathomable to me.
We have so many layers of electrical power and redundancy that it was simply impossible to lose all electrical power, especially to propulsion and navigation.
This casualty opened my eyes to the ongoing danger that commercial vessels operating around shore infrastructure present.
Yes. My question too. Why no redundancy?
On another channel, jeffostroff, he went over the original ntsb report. In it I recall hearing that the power failure in port was due to a low voltage issue as well. If my memory serves me correctly it was on the same number 3 generator.
An under voltage condition can manifest in several different ways. 1/ A momentary sudden dip in the generators RPM. 2/ A sudden surge of power being demanded such as in if several large motors start up at the same time (a number of refrigeration sea cans starting at the exact same time, bunch of large ventilation systems starting.). 3/ Loose wire or connector not making a good connection, intermittent. ]
There may be a resistance somewhere in the circuit between the source and the undervoltage relay, causing the under voltage condition.
My bet is on a broken soldering point which broke due to vibration.
The real issue is still, that there's no redundancies. With this amount of odds stacked on top of each other it's a miracle that this isn't happening more often.
Appreciate your logical insights.
Great explanation!
Great vlog as always Cheif! I hope you Enjoy your summer. Regards from Norway!
Assuming it’s the HV under volt that opened, then the LV under volt is going to (correctly) open also as there will be no voltage on the transformer secondary. All over bar the shouting. Nice vid.
Speaking as an electrical engineer... needle in a haystack time. Every circuit and component connection in the ship that is connected to the same power that activates the drop out solenoid is suspect. Possibly hundreds or thousands of feet of wire and one of a few, dozens or even hundreds of electrical components could be suspect.
And it gets worse. The major headache and problem child of all electrical engineers, a one off problem. A contactor that failed to pull in correctly, a system control unit blip and so on. A problem that only occurs once and returns to normal service.
The old 'you can't troubleshoot a fault when the fault doesn't exist.
To avoid these momentary faults commercial and residential power supplies have what is called reclosers. Unstable, too low or too high voltage or excessive current draw, the recloser opens, waits a few seconds then reconnects the power. But reclosers are very expensive and each sub system must have one or several. And of course, if there is a real fault the recloser will hand off, essentially not reclose again.
Then the question gets asked, can this be made 100% fail safe? Yes. BUT 100% fail safe means that entire control system must have a duplicate system and a watchdog circuit. One fails, the watchdog hands off to the duplicate system. If the fault is real, the individual faulty circuit's breaker should trip, removing the problem from the system. But duplicating an entire circuit and it's sub systems can be an immense additional expense or even impossible without redesigning a large portion of the physical electrical system of the ship. -Just for a circuit that may never get used.
In hospitals we have a 100% fail safe system. The emergency circuitry all critical medical equipment it's plugged into. It's controls are always on standby and it has it's own emergency generator dedicated to only that fail safe system, entirely separated from the regular power system of the facility. The generator must start, stabilize, and output power usually within 10 seconds. Very similar systems are found elsewhere such as nuclear power generation plants.
Here is my question, thinking that this is probably not the only ship that has this type of electrical system that could lead to shut downs, and delays in getting the generation systems, or even the propulsion system back up quickly! Should this have been a recognized issue when designing safety features and tug assisted restrictions around sensitive ports areas when ships are coming into or out of ports!? I mean there is probably some federal agency that oversees ships and regulates them! Shouldn't they have recognized the potential for something like this happening in an area where an unpowered ship could cause damage? Shouldn't they have had safeguards in place (like tug assistance) to guide ships through these areas? If a ship's power supply or propulsion system went down in open water, there would be time to deal with the problem or get assistance to the ship, but the same is not true in some ports or even canals or river systems, where an unpowered ship could cause a lot of damage before help was able to get to it!
A tug (or multiple tugs) is not going to stop a ship that size in the short amount of time between the blackout and accident.
@@briansomething5987 wouldn't have to stop it, just direct it away from hitting something!
Hi Chief I've been a viewer for a while now. Live very close to Saint John New Brunswick , have you ever called on the port here?
A little bit of generic information for people not familiar with control electrical systems and components like these Wago terminal blocks.
As others have mentioned, these blocks are almost universally used in industry for things like the control cabinets for CNC machines,
manufacturing equipment , pretty much everything. generally the control cabinets operate at 24VDC and not very high amperage,
These terminal blocks are mounted on DIN rail ,either extruded aluminum or pressed steel .
each block generally handles one circuit leading into and away from.
The Wago (or equivalent) are part of a system
The terminal block,
a tubular ferrule, that is crimped onto the wire before insertion into the block
a stripping tool, that strips off the insulation at the right lenght for the ferrule.
a crimping tool, that correctly crimps the the ferrule onto the wire .
and finally a operating tool that deflects the spring to inset or remove the wire. (the operating tool looks exactly like a small flat blade screw driver. but with
a 45 degree bend in the shank to give better finger clearance)
There are various diameters of ferrules that match each wire size ensuring a sound crimp.
Thanks!
Thank you! 😊
Did a simple series terminal cause a blackout? Is that what you ask?
That's what they are suspecting.
Remember that they allegedly had similar power issues while still in port. An intermittent issue can be very difficult to diagnose.
@@gordonrichardson2972 yes, but that was attributed to a crewmember inadvertently closing the exhaust flue damper of the only running generator.
Of course that would cause a blackout.... but it's likely to turn out unrelated.
The one in the image is a push fit type. Is that approved for marine use, or are screw terminals specified?
Thank you very much for sharing take care bless you
Based on the info you provided, this exam was only for the undervoltage circuits. Don't know if they have investigated an actual undervoltage condition on the bus that may have tripped the breaker? It looks like an instantaneous undervoltage condition could open the breaker, no time delay on that device? Don't know if they have data on a historian that looks at the generators performance and the bus voltage and frequencies? Lots still to investigate. If its an inherent issue with any component it needs to be identified and fixed. Otherwise the regs may have to be modified to ensure redundant power at certain times when operating. DC powered backup for vital loads may need to be added, like the engines LOP.
Sounds like everything was all right - just the cable keeping a safety feature closed was faulty, resulting in it tripping.
I think that whole transformer/half of the bus hadn't been used for a month, before they switched to it in port. Maybe they should avoid such switchovers in port or do a load test after switching over?
Very good
.
👍 MARK 👍
Some sources are suggesting that the generators may not have been in "sync" with their voltages and amperage causing the low volt breaker to trip?
Switchgear gearhead my whole life. Great explanation.
Since the tripping of the breaker can create such a large incident, why not not have an under voltage alarm instead of a release?
Perhaps not to faulty wiring, but to a defect in HR1 circuit breaker. Apparently, HR1 incorrectly sensed voltage below safe operational level and tripped cutting off power to TR1. For me, this information leaves me unsatisfied and I am skeptical that a malfunction of a under voltage sensor could lead to what actually happened. I know this will probably go nowhere and you do not really have the time to do so, but I would like to ask a series of questions:
Does circuit breaker LR1 (on the 'downstream' side of transformer TR1) also have a under voltage solenoid? (If it did, then LR1 would be expected to trip (as it did) when TR1 was deenergized.)
If LR1 does not have a under voltage solenoid, has anyone speculated or explained what caused LR1 to trip?
Another question I have:
Is it power from the 6.6 KVAC bus that runs the main engine blowers and pumps or is it the 440VAC bus that runs them?
As I understand it, the EGR (emergency 440 VAC generator) almost immediately started with the first blackout and the EGR circuit breaker closed returning 440VAC to the 440 bus. Is this correct?
Would the LVR circuit breaker (connecting the two sides of the 440 bus) be expected to open to isolate transformer TR2 and its associated breakers from the 440VAC supplied from the EGR so that HR2 and LR2 could be closed and supply at least the left side of the 440VAC bus?
I understand that HR2 and LR2 were subsequently closed to have transformer TR2 supply 440VAC to at least part of the 440 bus. At this time, was the EGR breaker opened and the LVR closed so that both sides of the 440 bus could be energized from TR2 or was the LVR breaker kept open so that only the left side of the 440 bus was supplied from TR2?
It is my understanding that breakers HR2 and LR2 also opened, isolating TR2 (TR1 already off line) and again killing the 440 bus. Is that correct?
If correct, is there any hypothesis on why these breakers opened too?
Again, it is my understanding that at some point breakers DGR3 and DGR4 opened (or were opened) and Diesel Generator 2 (already running) was connected to the 6.6KV bus by breaker DGR2 closing and that the bus was able to be maintained by Diesel Generator 2 for the remainder of the incident. Is this correct?
Or course, once the main engine was shut down and with all the electrical switching going on, it was impossible for the main engine to be restarted before hitting the bridge even if full electrical power to all buses was present and stable. I again assume this is correct?
As an electrical engineer (retired), these are questions I ask to gain some understanding of this incident.
Have seen new, very well made switchgear have termination issues in the control wiring. This was unique to the last 10-20 years, would pass all acceptance tests & occur down the road. Things happen, but a total loss after the over-engineering in these platforms is unimaginable.
Hello from Newcastle Australia
Hello from the other Newcastle
Actually it explains a lot of things.😊
So they have dual pairs of massive generators.. two completely independent systems for redudancy.. dual breaker systems.. plus an emergency backup generator.. and yet it can all go down with one bad solenoid? That's crazy to me. And I guess the other systems did come back online. It just went down at the perfect timing
Obviously the timing was terrible but with disfunctional load sharing resulting in motorization of one generator will be a massive load on the working generator and the large refrigeration load will backfeed into the motorized generator.
Grid connected generators use reverse power relays to protect against this. This backfeed likely tripped these breakers or dropped the voltage enough to get a UV trip. A very bad design
To paraphrase a decent movie "American components...Russian components...all made in china"
Like everyone else is saying Thanks Chief for the info from your point of view/knowledge.
*Taiwan
@@omgsrsly that is why I said paraphrase
I made the change for reasons
👍🏻👍🏻👍🏻
Those terminals are so simple to destroy. I used a 1/8" flat head screwdriver, that prevents stripping these terminals due to simple hand torque limitations. Some use a Tiny 1/16" driver cause they don't have the correct one and when Tyewraping the harness the wires pull out. My favorite was stripping the cable too short causing the insulation preventing permanent contact. General rule of Thumb: Strip the wire so at least the insulation is 1 bare Wire thickness away from the terminal edges prior to screwing in place. Also NO MORE THAN 2 WIRES PER TERMINAL and DO NOT TWIST THEM TOGETHER prior to insertion.
When out on the open ocean how long would it take for news of the accident take to review everyone
hay thanks for your info. Are you back on ship yet, or still in a teaching job?
Hej czyli na początku słusznie podejrzewałem rozłączniki separacyjne bo to wydawało się logiczne dlatego też NTSB otrzymało wskazówki czego szukać podczas śledztwa jak widać bingo ! Jednak nie tłumaczy to zatrzymania agregatów ani rozłączenia zasilania oświetlenia awaryjnego i zasilania pokładowego ja nadal podejrzewam że to sabotaż wewnętrzny lub zewnętrzny
It could be defective or wrong specification part that could be the issue.
Anyone know where the first diagram (the one that shows the 6600 volt circuits and generators @1:01) comes from?
I'm not buying that it was a mechanical coil trusted to maintain a threshold. That aside, WAGO is a trusted brand. We use them every day. Springs on a ferrule are very reliable. The ferrule material that is then between the conductor and the spring is engineered to withstand corrosion. I would not dunk it in saltwater, but with non-condensating humidity it's fine. And considering how little air current could possibly reach inside any of this, condensation is not a worry for me.
Faulty or poor terminations. Terminations are the weak link in a circuit.....it makes sense the NTSB is interrogating the modular terminal .....
The more I follow this, the more I suspect this will lead to some big changes in many aspects of ship and industrial electrical engineering.
So many of these failures are either "should never happen" or "should have failed safe" types. Although everything failed "safe" in the narrow sense (not causing electrical fires, etc), they didn't fail safe in the big sense (leaving a ship without steering after a minor fault).
Scary that one faulty connection could cause such a disaster.
A fault like this is why you should always run a split electrical bus during critical times. They were already running 2 generators. Running generators in parallel always entails risks with proper load sharing. Especially if voltage regulator or generator rpm problems come up.
Right on Greg. This appears to be a classic load share problem. A subject frequently not understood,
👍👍
For the want of a nail... 😢