On Mar 10, 5:29 am, westom wrote:
On Mar 9, 9:20 am, wrote:
Maybe because the central office doesn't consist of equipment that is
plugged into AC outlets like you'd find in a home? And actually
the telcos do use a tiered approach to protection and do not just rely
on a single point of supression.
COs use layers of protection. But not as you have described. Each
layer is defined by the only thing that makes each layer effective -
the single point ground. COs layer protection by grounding.
Once again, you're out in left field, in your own little world. I
spent 16 years working for a giant in the semiconductor industry and
calling on what originally was Bell Labs/AT&T. Later it became
Lucent. Along the way, I was involved with the sales and support of
tens of millions of CODECS. Those are the components that do the
analog to digital conversion. They sit on the line cards in the
central office switch, SLC, etc where the telephone lines from your
home or office terminate. I've held the line cards in my hands that
went into 5ESS switches, SLCs, etc. And I can tell you, they have
surge protection on the line card and that surge protection is not
connected to an earth ground with your 10ft wire.
But, you don't have to believe me. As usual, it's easy to refute
your claims with some simple links. Let's take a look at a datasheet
from National Semiconductor for their Subscriber Line Interface
Module:
http://www.national.com/ms/SB/SB-100.pdf
KEY FEATURES OF THE TP3210, TP3211, TP3212 SLIM
SUBSCRIBER LINE INTERFACE MODULE
# Complete CODEC/Filter and SLIC functions plus protection
# Requires only simple protection network and 4 resistors
externally
# Very small 1× by 2× package supports high density line
card and system
# Superb power surge and lightning protection
# Withstands 500V Return to Ground surge
# Power Denial mode
# Thermal overload protection
# Automatic Ring Trip
# Four Selectable Balance Networks
# Three positive relay drivers
# TP3210 SLIM meets all Bellcore and REA specifications
for USA Central Office
# TP3211 SLIM meets all CCITT requirements for 600X
Central Office applications
# TP3212 meets TR-TSY-00057 specification for DLC
POTS lines
Pay attention to the part where it says it provides surge protection
and meets the Bellcore specs for central offices. Now, are you going
to claim that all these line cards in a CO switch with 10,000 lines
are connected to an earth ground by a 10 ft wire?
Curious. Homeowners also layer protection. Above only discussed the
secondary protection system - a 'whole house' protector and the
building's single point earthing. Primary protection layer also
should be inspected:
http://www.tvtower.com/fpl.html
What do telco COs do for layered protection? Careful earthing - and
no plug-in protectors.
Bud claims power strip protectors clamp to nothing.
Sounds like you don't understand the definition of clamping.
He did not yet
say it. But he has repeated it incestuously. As a sales promoter, he
must. Power strip protectors have no earth ground. Do not define
surge protection (see manufacturer spec numbers that Bud always
forgets to post). And can only protect by magically stopping and
absorbing surge energy. Protection made irrelevant by protection
already inside every appliance.
And here we go again. Bringing up the protection inside appliances,
which is one of the best arguments AGAINST your claims. That's
because they typically use MOVs, similar to the MOVs used in plug-in
protectors and they work exactly the same way. Unless these
appliances come with a mythical earth ground inside, then they operate
and protect under the same limitations that a plug-in protector has.
You again misrepresent what I said. I did not say power strips do
not work. You would know that if comprehending provided facts and
numbers. You *assumed* based upon what you understood. I said they
are not effective.
Everyone that has been following your rants for years knows what
you've said. So, let's not start Clintonesque word games, OK? I
can take you back to posts where you not only said they don't work,
but that they CAUSE damage.
What you deny (subjectively and without facts) from SouthWest Bell:
I provided you with the link where SB actually sells plug-in surge
protectors. Enough said.
Many electricians are trained only in human safety; as defined by
code. Concepts essential to transistor safety (ie low impedance) are
unknown. Many electricians naively assume impedance means a thicker
wire. Low impedance means a shorter wire, no sharp bends, etc.
Insufficient knowledge explains why some electricians *assume* all
surges are same.
Last time I checked impedance of a wire is a function of both length
and thickness. So, who's naive?
Since you know better, then list those different types of surges.
Define how each is protected from. Instead, you have *assumed* all
surges are same type. Either *assumed* a power strip somehow stops
and absorbs surges, or makes surges magically disappear. Show us how
a protector stops what three miles of sky could not. Why do you never
do that?
Why repeat same subjective attacks? Show us how Southwest Bell did
not say, "Grounding is required to provide the surge protector with a
path to dump the excess energy to earth." Some electricians have
learned concepts beyond code; know that each layer of surge protection
is defined by its ground – not by protectors.
Take it up with Southwest Bell. Ask them how it is that they sell
plug-in surge protectors. Also take it up with the IEEE and NIST, as
they both talk about and show using plug-in surge protectors.
As the IEEE notes, proper earthing is not 100% effective. I said
same. Now apply some numbers from an IEEE standard:
... providing only 99.5-99.9% protection. ... a 99.5% protection
level will reduce the incidence of direct strokes from one stroke
per 30 years ... to one stroke per 6000 years ...
Install one 'whole house' protector for only 99.5% protection - for
about $1 per protected appliance. Then install maybe 100 power strip
protectors for another 0.2% protection at somewhere between $10 and
$150 per appliance. Show me how those power strips are effective -
especially at those prices? Nothing subjective. These are numbers
from IEEE and retail stores. Show me your numbers.
We showed you the IEEE and NIST positions. Both show plug-ins being
used as part of a surge protection plan. They clearly don't say just
put in a whole house protector and forget about it.
Obvious is your zero design experience. All appliances contain
surge protection as defined by industry standards. Without basic
design knowledge, you have automatically *assumed* that protection
always means MOVs.
Didn't say it always used MOVs. But that is typically what is used.
Looked in any appliances or electronic gear lately?
Instead, learn from industry standards including
the now obsolete CBEMA charts. Or Intel ATX spec that defined what
all computer power supplies must withstand without damage. If
appliances did not have protection, then you are trooping daily to
stores replacing dimmer switches, clock radios, and TVs. All
appliances contain surge protection integrated in its design. It is
required. Only the naive would look for protection in terms of MOVs
(or GDTs, etc). But again, your attack was subjective – ignored
generations of electrical standards and practice.
I guess then Appliance Design magazine must be naive. Here, from a
recent issue:
"Power: Combined Protection (March 2008)
by Philippe Di Fulvio
March 1, 2008
ARTICLE TOOLSEmailPrintReprintsShare
New device helps guard against over-current, over-voltage, and over-
temperature events.
Metal Oxide Varistors (MOVs) are typically used for transient over-
voltage suppression in AC line voltage applications. Lightning,
inductive load switching, or capacitor bank switching may cause
transient over-voltage conditions. In these applications, there also
exists the potential for a sustained abnormal over-voltage/limited-
current condition that may cause the MOV to go into thermal runaway,
resulting in overheating, out-gassing and possibly fire.
New thermally enhanced MOVs help protect a wide variety of low-power
systems against damage caused by over-current, over-temperature and
over-voltage faults, including lightning strikes, electrostatic
discharge (ESD) surges, loss of neutral, incorrect input voltage and
power induction.
These devices help provide protection in a wide range of AC line
applications, including AC mains LED lighting systems, PLC network
adapters, cell-phone chargers, AC/DC power supplies (up to 30 VA as
input power for 230 VAC input voltage), modem power supplies, AC panel
protection modules, AC power meters, and home appliances.
The thermally enhanced MOV is suitable for over-current and over-
voltage protection in a wide range of telephony and VoIP equipment
applications. These include cordless phones, VoIP gateways, data
modems, set-top boxes, security systems, MDF (Main Distribution Frame)
modules, analog linecards and ISDN (Integrated Services Digital
Network) linecards.
The widespread adaptation of VoIP gateways in homes and enterprise
environments has resulted in increasingly stringent safety
requirements for Customer Premise Equipment. The 2Pro device helps
equipment manufacturers comply with UL 60950 and remain operational
after specified lightning tests. It also helps equipment comply with
surge tests per TIA-968-A, IEC 60950, and ITU-T K.20/K.21. The UL 497A
listed protector also helps provide ESD protection. "
Or since you dragged PC power supplies into the discussion again,
let's look at a schematic for a typical ATX 200W unit:
http://www.pavouk.org/hw/en_atxps.html
Right there on the incoming AC line is component Z1:
"Varistors Z1 and Z2 have overvoltage protect function on the line
input."
That's right, varistor, as in Metal Oxide Varistor, MOV
So, who's naive and wrong now?
And the issue of what specifically is used in an appliance or PC power
supply is a moot point. Because what you can't avoid is that whatever
is used to provide protection, it operates without a direct 10ft
connection to earth ground. In other words, it operates with the
same limitations as a plug-in would have, yet you say it is effective,
but plug-ins are not. An inescapable contradiction.
Effective surge protection means a typically destructive type of
surge is earthed so that protection inside all appliances is not
overwhelmed. What does the power strip protector claim to protection
from? A type of surge that typically does not overwhelm internal
appliance protection (for tens or 100 times more money). You
misrepresent me probably because protection concepts are not taught to
or required for electricians
Probably because you never understood
the underlying technology - so you *assumed*.
Talk about assuming. You've assumed that I'm an electrician, which is
incorrect
Even GE contradicts your assumptions in their white paper:
In conclusion, ... This was accomplished because the TVSS is connected
in parallel to the load, thus provided a low impedance path to ground for
the transient surge. Applying Ohm’s Law, the lower the impedance to
ground during a transient surge, the lower the resultant transient voltage
developed over the total circuit impedance and earth ground.
Or a ham radio operator (K9KJM):
Those old wives tales of damage are for the most part over 50 year
old tales of woe from improperly grounded/ protected stations.
Electrical Engineering Times published two front page articles
entitled "Protecting Electrical Devices from Lightning
Transients". Where were power strip protectors discussed?
Nowhere. Instead, the articles discussed protection: ie single point
grounding, wire impedance, and "Providing a flow path for the
lightning current is central to effective lightning protection."
How does a power strip that would stop and absorb lightning somehow
provide a flow path? Show me the numbers. Explain these impedances?
A TV station engineer who made surges irrelevant in Florida:
The keys to effective lightning protection are surprisingly simple,
and surprisingly less than obvious. Of course you *must* have a
single point ground system that eliminates all ground loops. And
you must present a low *impedance* path for the energy to go.
Or Keison in a discussion of the British standard for surge
protection BS6551:
When the voltage rises above a certain level components inside
the protector divert the excess energy to earth and limit the
voltage to a safe level.
It appears only one of us is posting with extensive experience and
knowledge from numerous professionals.
I guess in your world, the IEEE and NIST, both of which show plug-ins
being used, don't count as having experience or being professional.
Regarding all your excerpts above, which cover some aspects of surge
protection, kindly provide the reference that says plug-in surge
protectors do not work and cause damage. How is it that in all the
internet you can't come up with a single reference that just directly
says what you claim?
The basic problem here is that you are stuck on one aspect of surge
protection and can't or won't realize that there are different ways to
deal with surge protection, especially in a tiered approach. I
think that was very nicely demonstrated a few posts back by the fellow
who asked you if you realize there is surge protection in aircraft.
Have you seen any airplanes tethered by a 10 ft wire to earth
ground? Yet, obviously they are protected from surges due to
lightning strikes.