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Cringley speculates like hell:
Delta Airlines last night suffered a major power outage at its data center in Atlanta that led to a systemwide shutdown of its computer network, stranding airliners and canceling flights all over the world. You already know that. What you may not know, however, is the likely role in the crisis of IT outsourcing and offshoring.
Do any Soylentils have inside/better information?
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What Happened When Delta Went Down Yesterday?
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(Score: 0) by Anonymous Coward on Tuesday August 09 2016, @05:35PM
Just how sensitive is a ground fault interrupter? Hard to believe that a decent voltmeter (with high input impedance, >10meg ohms) would draw enough current to cause a ground fault?? Or do electricians normally use a low impedance VOM??
(Score: 2) by Scruffy Beard 2 on Tuesday August 09 2016, @05:56PM
According to this page (PDF) [nema.org] the standard trip current is about 6mA.
120V/6mA=20kOhms.
But a whole-building supply may be a 600V, raising that to 100kOhms (within an order of magnitude of 1MOhm).
Now why a whole-building should trip on 6mA, I don't know.
(Score: 3, Informative) by Scruffy Beard 2 on Tuesday August 09 2016, @06:08PM
Whole-building devices may be more likely to trip at 500mA.
Residual-current device [wikipedia.org]
(Score: 0) by Anonymous Coward on Tuesday August 09 2016, @08:34PM
Those sorts of devices can indicate phantom voltages.
For a Go/No-Go test, an electrician will tend to use a device that pulls a bit of current. [google.com]
-- OriginalOwner_ [soylentnews.org]
(Score: 1) by jrmcferren on Tuesday August 09 2016, @10:42PM
The ground fault relay is probably factory set to 50 amps or so. These aren't your standard GFCI circuits, these are designed to trip to prevent a nasty arcing fault from occurring. When installed correctly the relay is set to take in account the tripping curve of the largest downstream breaker (both time and current) with the idea that a fault in a branch circuit will trip ONLY it's circuit breaker and the ground fault relay only trips IF there is a fault in the switchgear itself. In this case there was likely either the incorrect product installed (a low threshold device that operates more like a GFCI) or there was an accident and the relay was not coordinated with the downstream breakers. Remember, a ground fault should only ever activate one overcurrent (fuse or breaker) device if everything is coordinated correctly.