Wildly off topic. Or is it?
I've just finished reading the complete NTSB report on the container ship collision with the Key Bridge in Baltimore.
Don't bother — it's long. But…
Turns out the root cause was that a signal wire was not fully inserted into a connector, creating an occasional loose connection which looked fine but wasn't.
Moral of the story for all and sundry. If you have unexplained intermittent failures in an electrical circuit — check all your connections! They may look fine, but… pull on them. Wiggle them. Look again.
Before you fire the parts cannon (or knock down a bridge?)
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
Comments
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it would seem that the system should be designed to keep operating if a single connection failed…
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The deaths and destruction came down to a single, loose wire? A pin/socket in a connector plug? That is a shame. It would have cost $10 bucks and thirty minutes to fix.
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So it should have been — or rather, so it had been. But there were several other problems which meant that this one stupid failure caused a cascade of other problems. Some were design related, but most of the remaining problems were operational — operating shortcuts which had accumulated of the years with not harm.
Not even that. A wire wasn't stripped correctly, so it couldn't enter the connector fully and eventually wiggled loose.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England1 -
I am a draftsman/designer by trade. I did a 7 year stint with BG&E which is the power supplier in Baltimore. My first month they showed us a video taken by a homeowner. A tree trimmer dropped a branch into a power line and put a high voltage line into a lower voltage line feeding transformers supplying house current. Nothing tripped. So the houses all had extremely high voltage feeding them, blew meters off houses, electrified aluminum siding, it was epic.
The high voltage lines were sparking at an alarming level and you could hear the tree trimmer screaming for his life the entire time “help me, help me”. He came out of it with zero injuries and no one else got hurt, thankfully. The power company did buy a few houses though.
It didn’t trip because a single wire connection in the substation was missed on a drawing. A single wire connection….
It does not take much to make things go very bad.0 -
I have seen bumper stickers that say "Electrical Work is Not a Hobby"
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"Not even that. A wire wasn't stripped correctly, so it couldn't enter the connector fully and eventually wiggled loose."
I have founds connections like that, the wire not striped correctly so the conductor was not inserted onto the crimp connector correctly, so not crimped correctly, THEN the manufacture (probably unintentionally) hid the blunder with heat shrink tubing. This caused very intermittent operation. When I finally discovered the actual issue many other units were inspected over time or were repaired quickly if the symptom presented itself.
Many bad connections (of all types), happens all the time, much more than I think the public realizes. Sadly it takes a huge disaster to bring them to light.
"It didn’t trip because a single wire connection in the substation was missed on a drawing. A single wire connection…."
Also sounds like a primary fuse was missing or sized seriously wrong.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
I've seen this bumper sticker "It's not off until it's grounded".
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
here it usually happens because dte is 10 years behind in their 4 year tree trimming cycle and the branch growing near one of the primary wires gets wet in the first good rain of the spring or an ice or snow storm and shorts the primary wires. that burns clear and one of the primary wires falls and energizes one of the secondary wires. it doesn't trip the breaker at the substation not because of a wiring error but because the primary circuits are isolated from ground so all of those grounded things it is burning through don't produce a fault current
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I've never found an intermittent crimp, but I have found several pins not fullyn inserted into the housing, those would get more & more intermittent until they were pushed out past the point of making any contact. Also came across a few pins crimped onto insulation, but they didn't work at all. Took a while to find it the first time, it looked good from the back side.
Re primaries, I had one drop onto my phone line, while I was on the phone with 911 to tell them about the sparks coming off the pole pig every time the branch banged in to it. I was pretty shook up once I realized what had happened.
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I still remember the fear I had as a teenager presenting my connections for inspection before I could move on to the next connection. Later in life I understood why all the fuss.
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Aren’t these overhead wires insulated?
Edit: I just looked up. They are not!
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab
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in most other countries they are
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some crimp die designs tend to mash the barbs that are supposed to lock them in the housing so they don't lock in right
people sticking probes in to the connector end of the housing tens to bend the terminal so it doesn't make a good connection with the mating terminal
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No they aren't — in any country I know of. If only because the thickness of insulation to protect against direct contact would be prohibitive, even at the lowest primary voltages (around 7,000 volts). Most distribution lines in the US and Canada are at 23,000 volts, more or less, and the big primary grid lines can be as much as 500,000 volts.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
Decades ago, I made a half dozen 8" jumbers with a variety of pins and sockets on both ends to insert and use meter probes on other ends just to avoid this kind of damage. That must have been some investigation. I would hate to be the electrician responsible for that wire.
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When you're stringing overhead wires the weight of the wire directly impacts the spacing of poles which is the major driver of cost. With wires at that voltage the amount of insulation needed would significantly increase the weight of the conductors, which would make everything more expensive.
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Around here in the finger lakes
The 3 phase 60 cycle power is moved around here with
A back up only tie in interconnect with 115,000 3 phase to
34,500 volt AC 3 conductor to
4,000 volt 3 phase three conductor to
4,000 volt single conductor and neutral
480 3 phase in places
and 220 single phase AC conductor and neutral to home and business service.
They being nyseg made nothing but money when they back fed 34,500 to the second set of feeder lines along route 13 using one turbine from the local power plant before they stopped using the local power plant because of the less expensive natural gas fed power from out of the area.
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I believe NYSEG some years ago had to sell off their generation, a government thing.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Quite true. Also the New England states. The idea was so that consumers could choose which generating company (and energy source) they wanted separately. The hope was it would enhance competition and thus lower prices.
To no one's suprise, except a few dreamers, it actually raised prices to the consumers…
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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Nyseg wanted to get rid of all their generating stations because they could by 3 phase power on the open market for much less money. Nyseg also had to pay to keep the power plant running while they were waiting to kiss it off.
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