3 ms·

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

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.
vermilingua 7y ago
This is why (at least in my country) there are very clear codes about delineating power and data equipment. When we run data, it’s always at least a meter from any power cables or equipment.
- ChuckMcM 7y ago
  That is an excellent policy, do you have any companies in your country where the company believes itself to be really really smart and also believes rules like this are just bureaucracies trying protect their own jobs?

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.

vermilingua 7y ago

This is why (at least in my country) there are very clear codes about delineating power and data equipment. When we run data, it’s always at least a meter from any power cables or equipment.

ChuckMcM 7y ago
That is an excellent policy, do you have any companies in your country where the company believes itself to be really really smart and also believes rules like this are just bureaucracies trying protect their own jobs?