5 ms·

I hate big power. When I was an IBM engineer, power into the computer room was a big deal. Big diesel generators feeding into the main switchboard along with re

by abraae 7y ago

I hate big power. When I was an IBM engineer, power into the computer room was a big deal. Big diesel generators feeding into the main switchboard along with redundant mains connections. One incident I remember is when an electrician was working on one of the power feeds while it was live. Foolish, but the kind of thing people did when getting approval to shut off power was a bureaucratic nightmare. The sparky was tightening down a bolt on one of the phases with a big crescent spanner when he inadvertantly made contact with another phase. There was a flash that lit up the room and a loud bang. His crescent spanner literally melted in the middle. Incredibly he was uninjured, although he did take the whole room down, which was an extremely serious matter. Modern computers that plug into the wall socket are much more pleasant to work on.

C1sc0cat 7y ago
Proper computing , I have heard similar war stories about telecoms accidents with large dc power systems and shorting the busbars. Real Datacentres have diverse routing for every thing
- cr0sh 7y ago
  My senior year physics teacher in high school was a PhD student at Princeton who was doing teaching waiting to get back to his doctoral thesis research. Apparently, his work was with the Plasma Lab, primarily the Tokamak they had. Someone at some point had dropped a wrench or something on the bus bars of the capacitor bank used to power it - and, well, that was that. So he couldn't continue his studies until it was repaired. In the meantime, he taught us. Strange guy, but insanely intelligent, and fun to talk with. He always stressed the importance of "doing the experiment" - so we were always doing a practical experiments as a group to show how what we were shown and learned in class actually worked (within margins of error of course). I learned a ton in that class. After I graduated, I think he taught there one more year, then a few years later I looked him up, and he was back at Princeton, but was now working on something having to do with Materials science; I'm not sure what he's up to today, though - that was a couple decades ago. He wasn't much older than us at the time; late 20s or so.
derefr 7y ago
Good thing tools are made of such resistive metals. I can only imagine how that would have gone if the metal with the best tensile strength for a wrench was copper.
- skykooler 7y ago
  Some wrenches are in fact made of copper with about 1% beryllium; it's used because it does not create sparks when hit, useful in places where sparks are dangerous like a natural gas plant for example. More info: https://en.wikipedia.org/wiki/Beryllium_copper https://en.wikipedia.org/wiki/Beryllium_copper
dsfyu404ed 7y ago
Electricians work on live stuff all the time. They just rarely do so in residential settings which is why most people don't realize that. He was just sloppy. There procedures you're supposed to be following (like using insulated tools) to prevent stuff like that. Also relevant: https://i.imgur.com/HjqfZZh.jpg https://i.imgur.com/HjqfZZh.jpg
- Gracana 7y ago
  Not wanting to do paperwork generally isn't a good enough reason to do live work, though.
- protomyth 7y ago
  Plus, some have to work in really unusual and dangerous situations http://www.graybaresp.com/helicopter-lineman/ http://www.graybaresp.com/helicopter-lineman/
  - ethbro 7y ago
    My ex-Navy middle school science teacher apparently used to work on submarine DC systems. Per him, you worked with your right hand only and your right foot bare. Better to crisp your right side than send current through your left.
    - cr0sh 7y ago
      Probably the idea was to keep the current from crossing the heart/chest area, the right side being further away (to some extent in most people). There's a similar rule for HV work (and when working with vacuum tube-based equipment) - "one hand in pocket"; again, the idea being that if you're working on a live system, you aren't touching things with both hands leading to a shock across the heart area. Another rule for live systems (this applies both for higher voltages and for low voltage systems - it's mainly to protect the circuit and components): If you have to test/measure a live system, it's best to hook up the test equipment in the "dead" state, then power up the system, then shut down before removal or changing the position of the test leads, etc. But if this isn't possible, the next best thing to do is to hook one lead (if say using a multimeter) to a common reference point (that depends on the circuit and what you're measuring and where - but usually it's a shared ground point), and probe with the other using only one hand. Try to never probe with both hands/probes - because it can lead to inadvertent shorts and other problems. As always, there are exceptions to this rule, but they should only be considered after very careful thought and planning.
cr0sh 7y ago
> Incredibly he was uninjured Usually people who make that mistake don't get away any where close to that cleanly. One of the more horrific ways to accidentally die...
ChuckMcM 7y ago
Nice, my favorite big power story was a technician who was bringing up the next set of "rows" in a very large web scale data center. One component of that task was running thousands of feet of CAT-6e cable. Of course you want to be sure your spool of CAT-6e cable has no wire breaks in it before you start using it[1] to wire up racks so there was a step that involved putting a connector on the stub of cable that was inside the reel, and a connector on the end of the cable that came off the reel, and then hooking up an instrument between them to measure the resistance/propagation/etc. It is convenient to work at waist height for this, so our hapless technician had the cable spool put on a convenient big square brick like metal structure outside the building. He added the connectors, hooked up the tester, and the tester exploded. (well not completely but it did experience some rapid unplanned disassembly due to a large number of capacitors suddenly not existing. The "brick like structure" that the technician was using as a table top happened to be one of the transformers that was converting high voltage down to 440V 3-phase for the data center. When he effectively shorted the cable loop with his tester he air coupled into the field around the transformer and put > 400V into the tester. Whoops! [1] tracking down a bad network cable is not a lot of fun.
- emeraldd 7y ago
  With that much power floating around, I would have expected the transformer to have better shielding/warnings. Or is that not practical?
  - ethbro 7y ago
    I'd guess the tech was probably already in a power shed / access limited area. And given the distance scaling, it wouldn't have been a problem with a few more inches. He essentially lucked into the worst possible setup.
  - ChuckMcM 7y ago
    It had the required shielding and warnings about opening the box. That said, the spool of cable was likely 2500' of CAT-6e cable. In the root cause analysis it was estimated the voltage potential on the cable was between 210 and 280V and the current levels could have reached 500mA (a bit more than 100W of 'leakage'). That was well outside the what the test gear was "expecting" from a cable that it was testing.

by abraae 7y ago

C1sc0cat 7y ago

Proper computing , I have heard similar war stories about telecoms accidents with large dc power systems and shorting the busbars. Real Datacentres have diverse routing for every thing

cr0sh 7y ago
My senior year physics teacher in high school was a PhD student at Princeton who was doing teaching waiting to get back to his doctoral thesis research. Apparently, his work was with the Plasma Lab, primarily the Tokamak they had. Someone at some point had dropped a wrench or something on the bus bars of the capacitor bank used to power it - and, well, that was that. So he couldn't continue his studies until it was repaired. In the meantime, he taught us. Strange guy, but insanely intelligent, and fun to talk with. He always stressed the importance of "doing the experiment" - so we were always doing a practical experiments as a group to show how what we were shown and learned in class actually worked (within margins of error of course). I learned a ton in that class. After I graduated, I think he taught there one more year, then a few years later I looked him up, and he was back at Princeton, but was now working on something having to do with Materials science; I'm not sure what he's up to today, though - that was a couple decades ago. He wasn't much older than us at the time; late 20s or so.

derefr 7y ago

Good thing tools are made of such resistive metals. I can only imagine how that would have gone if the metal with the best tensile strength for a wrench was copper.

skykooler 7y ago
Some wrenches are in fact made of copper with about 1% beryllium; it's used because it does not create sparks when hit, useful in places where sparks are dangerous like a natural gas plant for example. More info: https://en.wikipedia.org/wiki/Beryllium_copper https://en.wikipedia.org/wiki/Beryllium_copper

dsfyu404ed 7y ago

Electricians work on live stuff all the time. They just rarely do so in residential settings which is why most people don't realize that. He was just sloppy. There procedures you're supposed to be following (like using insulated tools) to prevent stuff like that. Also relevant: https://i.imgur.com/HjqfZZh.jpg https://i.imgur.com/HjqfZZh.jpg

Gracana 7y ago
Not wanting to do paperwork generally isn't a good enough reason to do live work, though.
protomyth 7y ago
Plus, some have to work in really unusual and dangerous situations http://www.graybaresp.com/helicopter-lineman/ http://www.graybaresp.com/helicopter-lineman/
- ethbro 7y ago
  My ex-Navy middle school science teacher apparently used to work on submarine DC systems. Per him, you worked with your right hand only and your right foot bare. Better to crisp your right side than send current through your left.
  - cr0sh 7y ago
    Probably the idea was to keep the current from crossing the heart/chest area, the right side being further away (to some extent in most people). There's a similar rule for HV work (and when working with vacuum tube-based equipment) - "one hand in pocket"; again, the idea being that if you're working on a live system, you aren't touching things with both hands leading to a shock across the heart area. Another rule for live systems (this applies both for higher voltages and for low voltage systems - it's mainly to protect the circuit and components): If you have to test/measure a live system, it's best to hook up the test equipment in the "dead" state, then power up the system, then shut down before removal or changing the position of the test leads, etc. But if this isn't possible, the next best thing to do is to hook one lead (if say using a multimeter) to a common reference point (that depends on the circuit and what you're measuring and where - but usually it's a shared ground point), and probe with the other using only one hand. Try to never probe with both hands/probes - because it can lead to inadvertent shorts and other problems. As always, there are exceptions to this rule, but they should only be considered after very careful thought and planning.

cr0sh 7y ago

> Incredibly he was uninjured Usually people who make that mistake don't get away any where close to that cleanly. One of the more horrific ways to accidentally die...

ChuckMcM 7y ago

Nice, my favorite big power story was a technician who was bringing up the next set of "rows" in a very large web scale data center. One component of that task was running thousands of feet of CAT-6e cable. Of course you want to be sure your spool of CAT-6e cable has no wire breaks in it before you start using it[1] to wire up racks so there was a step that involved putting a connector on the stub of cable that was inside the reel, and a connector on the end of the cable that came off the reel, and then hooking up an instrument between them to measure the resistance/propagation/etc. It is convenient to work at waist height for this, so our hapless technician had the cable spool put on a convenient big square brick like metal structure outside the building. He added the connectors, hooked up the tester, and the tester exploded. (well not completely but it did experience some rapid unplanned disassembly due to a large number of capacitors suddenly not existing. The "brick like structure" that the technician was using as a table top happened to be one of the transformers that was converting high voltage down to 440V 3-phase for the data center. When he effectively shorted the cable loop with his tester he air coupled into the field around the transformer and put > 400V into the tester. Whoops! [1] tracking down a bad network cable is not a lot of fun.

emeraldd 7y ago
With that much power floating around, I would have expected the transformer to have better shielding/warnings. Or is that not practical?
- ethbro 7y ago
  I'd guess the tech was probably already in a power shed / access limited area. And given the distance scaling, it wouldn't have been a problem with a few more inches. He essentially lucked into the worst possible setup.
- ChuckMcM 7y ago
  It had the required shielding and warnings about opening the box. That said, the spool of cable was likely 2500' of CAT-6e cable. In the root cause analysis it was estimated the voltage potential on the cable was between 210 and 280V and the current levels could have reached 500mA (a bit more than 100W of 'leakage'). That was well outside the what the test gear was "expecting" from a cable that it was testing.