🚀 go-pugleaf

In article <1827@jato.Jpl.Nasa.Gov> morris@jade.Jpl.Nasa.Gov (Mike Morris) writes:
>
>Anyway, due to his experience, I compared the guts of a Tripp-Lite Isobar,
>and the common "surge supressed" outlet strip.  There are several heavy-duty
>toroidal chokes and capacitors in an Isobar, vs 3 metal-oxide-varistors in the
>cheapies.  in fact, I recently found a bunch of 140v MOVs in surplus and added
>them to the standard strips I already had.  The Isobar is also built with 
>good components, and put together like the proverbial tank - no snap-together
>plastic here - it's all metal and screws.
>

These surge supressors are intended for "surges" and will not provide the
type of protection needed in "near" thunderstorms.  The best protection from
induced high voltage is the liberal use of gas-discharge supressors.  The gas-
discharge supressor consists of a gas-filled glass tube with a ground, anode, 
and a cathode.  These three leads are connected across the source, virtual
ground and real ground as shown below:

  ........            ..............           ........
  |      |            |            |           |      |
  |120vac|------------|---      ---|-----------|120vac|
  | main |  Cathode   |      |     |   Anode   |Return|
  |......|  (anode)   |......|.....| (cathode) |......|
                             |
                             |
                             | Ground
                           ----
                          / / / 

       The connection order, other than ground, does not matter.

When a high voltage spike is induced on the your power grid so that the 
potential between the Cathode and Anode reaches the rated trigger potential
of the device the gas ionizes and shorts the spike to real ground.  The device
dumps the voltage surge extremely fast.  Be sure that you have provided an
adequate ground path.  I worked for a SCADA company in New Orleans and had a
system with environmental sensors mounted on top of a 280 feet stack.
During the storm season (July-Oct) the stack averaged two to three direct 
hits a month.  The only device I found that prevented the data input cards from
getting fried was the gas-discharge supressor.  You should be able to find
them in any electronics or electrical supply house that services the tele-
phone industry.

NOTE:  We used a 3 inch diameter, 10 feet long, solid copper rod as our real
       ground for a number of gas-discharge tubes. 

-- 
Philip E. Johnson                    UUCP:  usenet!ingr!b3!sys_7a!phil
MY words,                           VOICE:  (205) 772-2497
MY opinion!