From: trevor@rageaudio.com.au   
      
   On 30/03/2019 5:32 am, Peter Wieck wrote:   
   > As an aside, I toured the Veolia Steam Plant in Philadelphia, yesterday.   
   This plant has been in continuous operation since it opened in 1909, and is   
   quite a remarkable place. I got to be up-close-and-personal with the   
   equipment, including the steam and    
   gas turbines, the boilers, pumps, controls, switchgear, powerhouse and uplink.   
   >   
   > Standing under the main step-up transformer (2,300 VAC to 23,000 VAC) is a   
   truly visceral experience. Once one feels that level of "HUM", one will never   
   mistake 60 for 120 ever again.   
   >   
   > Relevance:   
   >   
   > 60 HZ hum suggests a bad or failing rectifier.   
   > 120 HZ hum suggests bad or failing filter caps.   
   > 50 & 100 for our Euro and Asian friends.   
   >   
   > Amazing amount of mechanical-feedback devices in use in these plants - it   
   seems that VFDs and  great many "modern" grid-tie devices are simply not   
   sufficiently rugged or reliable at this scale.   
   >   
   > Peter Wieck   
   > Melrose Park, PA   
   >   
      
   **Interesting. Back in 1971-ish, when I was in training, I was posted to   
   a SW radio transmission facility. A big sucker. Anyway, since it was a   
   partly gummint operation, they had multiple backups for mains power.   
   There were two, large Diesel generator units (maybe 2.5Metres high, as I   
   recall). Cooling water was routed through the fountain in the front of   
   the facility for some reason. If the fountain was operating, then you   
   knew that the Diesels were running. Each week, the Diesels would be   
   fired up for 30 minutes or so for testing. There was a big meter mounted   
   between the Diesels. Apparently, the needle had to be centred, when the   
   Diesels had reached an in-phase operation. Then they could be switched   
   in. I asked what would happen if they were switched when not in phase.   
   Apparently all the trainees asked that question. No one knew for sure   
   and they didn't want to find out. Probably a lot of structurual damage   
   would occur. At another facility, there was a huge battery room,   
   consisting of many (100+) Pyrex™ lead acid batteries, enabling the   
   facility to operate for several days without power. We were given a   
   warning that, if the 2 Tonne fire door closed and we were trapped   
   inside, that we should climb on top of the Diesel generator, so we could   
   hopefully escape suffocation, when the room filled with CO2. Fun days.   
      
   And, to bring this back on-topic the organisation was the main   
   communication hub from Australia to the rest of the world (Satellite,   
   submarine cable, SW radio, etc). As such they employed a 2.5kV power   
   supply to power the vacuum tube repeaters between here an New Zealand.   
   Even better, there was a system on the first floor that comprised about   
   a dozen or so racks full of vacuum tubes. The system was known as TASI   
   (Time Alignment Speech Interpolation). It was a mind-bendingly   
   complicated system, that detected silent spots in voice comms and   
   inserted another section of voice comms into the silent bits. It   
   effectively doubled the bandwidth of the cable. ALL with valves. Even   
   the CROs used to service the gear were tube Tektronix units (yet the   
   rest of the facility used all SS CROs). Fascinating stuff. The computer   
   on the top floor (it occupied the whole floor) had a 2 Metre long drum   
   drive. Hundreds of heads, very fast access time. Lots of cool stuff. My   
   cell phone probably has ten times the power.   
      
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