|
Posted by w_tom on June 13, 2006, 1:07 pm
Plug-in protector has no effective earth ground. No earth ground
means no effective protection. Therefore Bud's article shows a plug-in
protector putting two TVs at 8000 volts. Will those TVs at 8000 volts
not be damaged - not leak currents in destructive paths? No. Those TVs
may be damaged because they are at 8000 volts. Bud's citation even
demonstrates why plug-in protectors can contribute to damage.
Other papers he forgets to cite note how plug-in protectors can even
contribute to damage of that adjacent appliance - TVs:
Martzloff and Key in 1994 wrote in "Surging the Upside-Down House:
Looking
into Upsetting Reference Voltages" :
> 1) Quantitative measurements in the Upside-Down house clearly
> show objectionable difference in reference voltages. These occur
> even when or perhaps because, surge protective devices are
> present at the point of connection of appliances.
But then that is what the mikeholt.com paper also demonstrates on
page 33/34 in figures 8 and 9. TVs put at 8000 volts because a plug-in
protector is too far from earth ground; therefore is not properly
earthed. Earthing is essential to effective protection.
The paper on page 22 says:
> An effective, low-impedance ground path is critical for the
> successful operation of an SPD. ... Therefore, an evaluation
> of the service entrance grounding system at the time of the
> SPD installation is very important.
Of course. A protector is only as effective as its earth ground.
That protector adjacent to TVs put those TVs at 8000 volts -
ineffective protection. Effective protection must make a low impedance
connection to a good earth ground. That again means a protector
located 'less than 10 feet' from earth. Even Bud's paper demonstrates
how "objectionable ... voltages ... occur even when or perhaps because
surge protective devices are present at the point of connection of
appliances". The adjacent protector can even contribute to damage of
electronics.
.
Bud-- wrote:
> Plug-in surge suppressors for cable TV need to have a port to include
> both the power and cable TV. The multi-port surge suppressor will clamp
> all voltages on power and signal wires to the common ground at the
> suppressor. The IEEE guide at
>
http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf
> explains this quite well. It says the cable center conductor can be 4000
> volts with respect to the shield. A plug-in suppressor will clamp this,
> likely with a gas discharge tube. A bigger problem is if the cable
> entrance ground block is not near, and connected with a short wire, to
> the power service earthing conductor. That is also protected by a
> multi-port plug-in surge suppressor and is illustrated in the IEEE guide.
>
> Similarly, a plug-in suppressor for a computer with phone connection has
> to have ports for both power and phone line.
>
> bud--
| 
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap