Surge protector fuse blown
Nils Holland
I'm using some cheap surge protector that I plug into an outlet in order to
protect my computer from power surges. I don't know how efficient such a
thing is. All I know is that it basically seems to consist of a 4 A fuse.
Now, I have two questions about this:
1) Three devices are connected to the ciruit protected by the surge
protector: My computer, the monitor, and a small 40 W light on my desktop.
Now, yesterday the bulb in my desktop light burned out, and at the same
time, it killed the fuse in my surge protector. Although I guess it's not
really hard to explain, I'm still not really sure in what way the burning
out light bulb blows the fuse. How can this be technically explained? Why
doesn't the fude blow when normally turning on the light bulb?
2) When the light bulb killed my fuse, my computer was turned on, and so it
of course lost power and crashed. Although the fuse in the surge protector
in the circuit is supposed to protect my computer, I still cannot stop
thinking about any negative effects this issue may have had on my computer.
Although it's working fine, I wonder if at the time the light bulb burned
out there was some kind of surge that could potentially have harmed my
computer.
Besides the obvious problem of possible data corruption when the power to
the computer fails, I'm wondering if any more serious defetcs could be
causes should the bulb in my light burn out again, and thus if it is wiser
to put the light onto a different circuit (or at least not behind the surge
protector, along with the computer).
Any comments on the above questions are welcome.
Nils
--
----------------------------------------------------------
Nils Holland - ni...@nightcastleproductions.org
NightCastle Productions - Linux in Tiddische, Germany
http://www.nightcastleproductions.org
"Give the heavens above more than just a passing glance
And when you get the choice to sit it out or dance -
I hope you dance!"
----------------------------------------------------------
Lenny
turn opened an already possible flaky fuse. If you are really concerned,
why not get yourself a better protector, perhaps one having some active
type of internal protection, or get some MOV's and install them inside
yourself? Lenny Stein.
Roger Hamlett
"Lenny" <captain...@hotmail.com> wrote in message
news:3B4077...@hotmail.com...
> Nils Holland wrote:
> >
> > Hi folks,
> >
> > I'm using some cheap surge protector that I plug into an outlet in
order to
> > protect my computer from power surges. I don't know how efficient such
a
> > thing is. All I know is that it basically seems to consist of a 4 A
fuse.
> >
> > Now, I have two questions about this:
> >
> > 1) Three devices are connected to the ciruit protected by the surge
> > protector: My computer, the monitor, and a small 40 W light on my
desktop.
> > Now, yesterday the bulb in my desktop light burned out, and at the
same
> > time, it killed the fuse in my surge protector. Although I guess it's
not
> > really hard to explain, I'm still not really sure in what way the
burning
> > out light bulb blows the fuse. How can this be technically explained?
Why
> > doesn't the fude blow when normally turning on the light bulb?
bulb blowing, to take out a fuse, if the actual support pillars are below
the filament. What happens is that the filament blows, and parts of the
blown filament then fall across the incoming wires, and blow a second
time, drawing far more current than normal when it does so. I have a
chandelier, where all the bulbs are prone to doing this, and about one in
four times a bulb fails, it will also take out the fuse. This is also why
in theatrical wiring systems, the units are individually fused at the
lighting console, rather than fusing several lights together.
> > 2) When the light bulb killed my fuse, my computer was turned on, and
so it
> > of course lost power and crashed. Although the fuse in the surge
protector
> > in the circuit is supposed to protect my computer, I still cannot stop
> > thinking about any negative effects this issue may have had on my
computer.
> > Although it's working fine, I wonder if at the time the light bulb
burned
> > out there was some kind of surge that could potentially have harmed my
> > computer.
> > Besides the obvious problem of possible data corruption when the power
to
> > the computer fails, I'm wondering if any more serious defetcs could be
> > causes should the bulb in my light burn out again, and thus if it is
wiser
> > to put the light onto a different circuit (or at least not behind the
surge
> > protector, along with the computer).
Yes. It is wiser to put it on a seperate circuit.
> > Any comments on the above questions are welcome.
> >
> > Nils
> >
> > --
> > ----------------------------------------------------------
> > Nils Holland - ni...@nightcastleproductions.org
> > NightCastle Productions - Linux in Tiddische, Germany
> > http://www.nightcastleproductions.org
> > "Give the heavens above more than just a passing glance
> > And when you get the choice to sit it out or dance -
> > I hope you dance!"
> > ----------------------------------------------------------
> Perhaps a spike was generated by the opening of the filiment which in
> turn opened an already possible flaky fuse. If you are really concerned,
> why not get yourself a better protector, perhaps one having some active
> type of internal protection, or get some MOV's and install them inside
> yourself? Lenny Stein.
Best Wishes
John (Technoid)
Nils Holland wrote in message ...
Hi folks,
Nils:
If there's nothing other than a fuse inside that device,
it's NOT a surge protector.
If it has Metal-Oxide-Varistors (MOVs), then most
likely the device has reached the end of it's service life.
MOVs are "sacrificial" devices, they will absorb only so
many voltage "spikes" before they degrade to the point of
ineffectiveness... Perhaps that's what happened, and a final
surge is what caused the blowout of the bulb, and the fuse.
(that would be a *severe* voltage spike to do that, btw.)
I'd strongly recommend that you replace it with a UPS...
Surge protectors alone will do nothing to prevent data loss
in the event of short-duration power interruptions, and
good UPSs have better surge protection built-in.
- John (Technoid)
Nils Holland
> Nils:
>
> If there's nothing other than a fuse inside that device,
> it's NOT a surge protector.
>
> If it has Metal-Oxide-Varistors (MOVs), then most
> likely the device has reached the end of it's service life.
Thanks for the hint. According to the packaging of the unit (which I still
have around), this thing really contains not only a signle fuse, but also
MOVs. I didn't know that these things will get ineffective over time, but
since I bought my surge protector in 1996, I guess that it'S probably
really to to replace it.
As you suggestes, an UPS would probably be a good idea. However, these
things tend to be expensive. I'll have to inform myself about these things
a bit more (price, performance, etc), and then I will decide if I'll only
get myself a new surge protector, or an actual UPS...
Greetings
w_tom
surge from one wire to all others. That applies both to power strips and to
UPSes. IOW a surge seeks earth ground. Once permitted inside a building, a
surge will seek every earth ground, destructively through appliances.
If a surge protector is connected less than 10 meters to earth ground, then
it shunts a surge to earth - no electronics damage. But power strips and
UPSes are too far from earth ground. Fred of Sutton Designs notes this in his
FAQ. http://www.suttondesigns.com/doctext/zs.html
The surge protector simply provides the surge with more paths through a
computer. A surge that approaches a computer on one wire will seek earth
ground through a computer on all other wires - thanks to a plug-in surge
protector - UPS or power strip. Yes, the adjacent surge protector can
contribute to damage in a powered off computer.
Fundamentals of effective surge protection have been demonstrated and proven
since before the 1930s. But since so many are only educated by boxes on store
shelves, then we think it is effective surge protection only because it is
called a surge protector. Effective surge protection shunts a surge to earth
ground at the utility service entrance. Ineffective plug-in surge protection
can actually contribute to surge damage in a powered off computer.
A surge enters on AC line where a power strip shunts that surge to all other
wires. Now the surge enters the motherboard via the green safety ground
wire. Destructive surges are common mode; they seek earth ground. This surge
finds earth ground on the phone line - destructively through modem. That is
how modems are most often damaged. A surge enters on AC lines and leaves on a
well grounded phone line.
IOW both expensive and cheap plug-in surge protector are equivalent -
ineffective. They are too close to computer, too far from earth ground, too
expensive to only protect (ineffectively) earth ground, and too undersized for
effective protection. We should be calling it a scam.
How many joules in your plug-in surge protector? That is why plug-in surge
protectors wear out so quickly. They are undersized or grossly undersized.
That rating? It functional value is really more like 1/3rd and never more
than 2/3rd that value. Anyone with basic electrical knowledge knows that.
Visit the newsgroup alt.rec entitled "PC users...." for additional
information. And most definitely ignore recommendations for plug-in UPSes
as surge protectors. Those UPSes manufacturers don't even spec effective
surge protection from the destructive, common mode surges. Their color
glossies are simply written in such a way that the technical naive will feel
they have surge protection - the facts be damned.
Peter Duck
w_tom <w_t...@usa.net> wrote:
> Now for the dirty little secret about surge protectors ...
There's no secret about surge-protectors, merely some misunderstanding
to which you're doing your best to contribute: for one apparently
obsessed with the subject in general, and the significance of a 'good'
short earth/ground-connection in particular, you seem to know remarkably
little.
> ... Once permitted inside a building, a surge will seek every earth
> ground, destructively through appliances.
> ... If a surge protector is connected less than 10 meters to earth
> ground, then it shunts a surge to earth - no electronics damage.
> ... Effective surge protection shunts a surge to earth
> ground at the utility service entrance. ... A surge enters on AC line
> ... Destructive surges are common mode; they seek earth ground. This
> surge finds earth ground on the phone line - destructively through
> modem. That is how modems are most often damaged. A surge enters on
> AC lines and leaves on a well grounded phone line.
'Common mode' surges, as from lightning strikes, don't in general simply
'enter on the AC lines', nor would any practicable diversion to 'local
earth' afford much protection to connected equipment if they did.
The actual effect is that the <earth and line> potentials at the power
substation, locally, and/or at the phone-exchange/'central office' are
briefly very different: any one of them can be 'the odd man out', and a
'good' connection to 'local earth' would be as likely to contribute to
any destruction as to prevent it.
Local 'earthing' (as distinct from connection of equipment casings to
the power-company's earth-wire) has rather gone out of fashion over the
last century: in the UK, at least, there are nowadays no spark-gap-like
devices from either phone-lines or AC supply-lines to any local
earth-connection.
> ... both expensive and cheap plug-in surge protector are equivalent -
> ineffective. ... We should be calling it a scam.
They simply aren't intended as protection against
common-mode/lightning-induced surges, nor AFAIK do any claim to be:
their purpose is solely to absorb the (low-energy) transients produced
by the switching of inductive loads on the same supply, principally the
motors in fridges/washing-machines/air-conditioners, etc.
This they probably do quite well (without significant wear-out, in
domestic situations), but as PC PSUs, TVs, etc., are necessarily quite
tolerant of such transients anyway it may be rather difficult to tell
...
--
Peter Duck <pd...@zetnet.co.uk>
w_tom
successfully since the 1930s, what is commonly known (see hyperlinks below),
and what is being discussed currently even the newsgroup
rec.radio.amateur.antenna in a discussion "GROUNDS". R.P.Haviland
begins the discussion by accurately noting,
> There are three types of grounds needed when dealing with RF equipment:
> - A path to the earth (ground) for RF
> - A path to ground for a lightning stroke
> - A path to ensure that the powerline is connected to earth.
Other testimony only proves what has been known for decades:
http://www.harvardrepeater.org/news/lightning.html
http://scott-inc.com/html/ufer.htm
http://lists.contesting.com/_towertalk/199909/0143.html
http://www.telematic.com/index.htm
http://www.polyphaser.com/ppc_technical.asp
I guess all these real world professionals as well as papers in the many
IEEE Transactions (including the entire 4 Nov 1998 issue of IEEE
Transactions on Electromagnetic Compatibility) talk about obsolete and 'out
of fashion' ideas? Or maybe I have accurate summarized what is more
commonly known. Curious that good earthing is done less in the UK which
appears to have more lightning damage in a country with less lightning
strikes per square kilometer. Sounds more like earthing is becoming less
fashionalbel where cost controlling MBA mentalities don't want to spend the
money - its the other guys problem.
Correctly noted is that computers, TV, etc are quite tolerant of surges.
A computer power supply must withstand 1000 volts differential mode; 2000
volts common mode. So why do so many suffer computer surge damage when
surges are not shunted to earth ground at the service entrance? Same
conditions are observed where surge damage has occurred - no or poor
earthing of incoming lines - either direct or via a surge protector. That
is in direct agreement with the first lines in www.telmatic.com's
application notes on earthing.
> Even the best surge protection device is of no use if
> incorrectly installed. Installation, and more specifically
> earthing, is a critical aspect of surge protection.
Telmatic is in agreement with IEEE professional papers and with me. What
sources support your contention that I "seem to know remarkably little" or
that "Local 'earthing' has rather gone out of fashion over the last
century". On the contrary. Local earthing has been improved
significantly by American phone and CATV companies who now install better
surge protection closer -less than 3 meters - to a central earth ground.
Even CATV companies are teaching installers to connect properly to central
earth ground. The more responsible satellite dish installers refuse to
install systems where a good earth ground cannot be obtained - because earth
grounds are so critical to reliable satellite dish installations exposed to
lightning. Even power companies now sell surge protection behind the meter
because surge protection to earth ground is slowly becoming common in
residences as it was common in telco and other high reliability facilitates.
Clearly we all don't know what you know. Are we all wasting time and
money - or do you simply not appreciate the critical nature of a single
point earth ground in surge protection.
A surge protector is only as good as its earth ground. No earth ground
means no effective surge protection. Earth ground is critical for
protection from common mode transients. But some still question this well
proven and widely published knowledge.
Peter Duck wrote:
> There's no secret about surge-protectors, merely some misunderstanding
> to which you're doing your best to contribute: for one apparently
> obsessed with the subject in general, and the significance of a 'good'
> short earth/ground-connection in particular, you seem to know remarkably
> little.
>
> > ...
> 'Common mode' surges, as from lightning strikes, don't in general simply
Peter Duck
w_tom <w_t...@usa.net> wrote:
[A 'good local earth' is as likely to contribute to 'common-mode'
surge-problems as protect against them]
> Your comments are in direct contradiction to what has been
> accomplished successfully since the 1930s, ... and what is being
> discussed currently even the newsgroup rec.radio.amateur.antenna ...
>| There are three types of grounds needed when dealing with RF equipment:
> > - A path to the earth (ground) for RF
> > - A path to ground for a lightning stroke
> > - A path to ensure that the powerline is connected to earth.
> ... The more responsible satellite dish installers refuse to install
> systems where a good earth ground cannot be obtained - because earth
> grounds are so critical to reliable satellite dish installations
> exposed to lightning.
You're now putting your beliefs about earthing into a much narrower (and
more appropriate) context than the previous sweeping generalisations.
Sure, anyone erecting what's in effect a 'lightning conductor' needs a
'local earth' to which to connect it (the ground-plane may also play a
key part in RF propagation-characteristics).
If mains-powered equipment is hung on the 'lightning conductor' ('cos
it's intended as an aerial) there's no alternative but to grapple with
the problems arising when/if electrical storms (or even power-system
faults) create large potential differences between 'local earth' and
'power-line earth'.
In the more usual case, however, a PC and modem is at risk only from
transient potential-differences between phone-line earth and power-line
earth: what benefit is there in (more or less
expensively/inconveniently) introducing a further contender, local
earth?
Even if (unusually) there is there is real, intended-as-such,
lightning-conductor on the building, or e.g. a flagpole, would you think
it A Good Idea to also use the earthing-point provided for it as the
earthing-point for any electrical/electronic equipment, and/or tie it to
power-line earth?
> A surge protector is only as good as its earth ground. No earth
> ground means no effective surge protection. Earth ground is critical
> for protection from common mode transients.
The last sentence puts the preceding two in context: protection against
line-to-line surges doesn't depend on earthing, and cheap/easy solutions
are effective, if seldom necessary, against transients likely to be
encountered domestically-.
> But some still question this well proven and widely published knowledge.
Probably not, but what's certainly questionable is the
cost-effectiveness for 'domestic' users of attempting to suppress/divert
power-line common-mode surges: the high power/low impedances make it a
non-trivial task, with little prospect of pay-off.
Phone-line surges are much easier, and for those the power-line earth
(to which the equipment is anyway connected) is a more appropriate as
well as simpler reference-point: that, after all, is what the modem
'cares about'.
--
Peter Duck <pd...@zetnet.co.uk>
w_tom
rags, books involving Maxwell's equations, AND still don't have a clue what
has been posted. For example I think differential or normal mode transients
are introduced. But I am not sure and don't know why. Normal mode
transients are irrelevant to common surge damage. The industry is loaded
with standard terms and definitions for all these electrical flows - and yet
I find none in the post.
Confusing are sentences such as:
> You're now putting your beliefs about earthing into a much narrower context
When did standard engineering concepts proven since the 1930s and routinely
published in IEEE papers suddenly become 'my' belief. I did not make this
up. It is well published throughout the world. One issue alone of the IEEE
Transactions on Electromagnetic Compatibility (4 Nov 1998) is devote to
nothing but surge protection, lightning, and the critical aspects of earth
ground connections.
However Peter is in the UK where, for some reason, the UK stopped earth
grounding telephone and electric utilities. This is considered totally
unacceptable and outrightly dangerous in the US. But then again, in the early
days of satellite launches in French Giunea, numerous American computers had
destructive power problems when lightning storms created ground loops
transients. The French also seemed to have no concept of earth grounding
principals meaning that thunderstorms routinely damaged America satellite
support electronics. Maybe I wrongly assume earth ground is appreciated
thoughout the world.
Then again, for a small country, I am amazed at reading whole neighborhoods
with widespread electronics damage from the recent t-storms. The US, with
electric and phone wires overhead and with greater frequency CG lightning in
many places does not suffer that kind of disaster. Is Europe much more prone
to thunderstorm damage because Europe does not have the American requirements
of earth grounding?
In the US, all utlities are required to have a building connection to earth
ground. Any voltage difference between a utilities and earth is considered a
threat to human life. Now that same earth grounding must be enhanced for
surge protection (transistor safety). IOW homes need common mode surge
protection similar to what was once installed only on commercial electronic
facilities because the transistor is now ubiquitous in the home.
A rather confusing sentence:
> If mains-powered equipment is hung on the 'lightning conductor'
> there's no alternative but to grapple with the problems arising
> when/if electrical storms (or even power-system faults) create
> large potential differences between 'local earth' and
> 'power-line earth'.
I have no clue as to what was posted no matter how many times I read this.
When did we suddenly start connecting air terminals (lightning rods) onto
electronic equipment. When did 'power line earth' not become earth ground
which somehow is different from some new term called 'local ground'?
"When/if electrical storms create large potential differences" - is simplified
by the term 'common mode surge'. It can be created by a lightniing strike -
the simple electric current impulse from a cloud to ground that appears on
electronic equipment as the most typically destructive of surges - the common
mode surge.
Then there is this paragraph:
> The last sentence puts the preceding two in context: protection against
> line-to-line surges doesn't depend on earthing, and cheap/easy solutions
> are effective, if seldom necessary, against transients likely to be
> encountered domestically-.
What line-to-line surge? Where did a normal mode transients suddenly
appear from? Typically destructive surges are common mode transients. As for
normal mode transients, they are so small as to be called noise.
I believe Peter does not understand that all utilities are required by code
to be commonly grounded for human safety and that incoming power and phone
lines must connect to earth. However these codes are sometimes violated -
especially in older homes. Also these earth connections installed for human
safety can be too long for transistor safety.
Peter Duck
w_tom <w_t...@usa.net> wrote:
> Confusing are sentences such as:
>| You're now putting your beliefs about earthing into a much narrower
>| context
> When did standard engineering concepts proven since the 1930s and
> routinely published in IEEE papers suddenly become 'my' belief?
Most (all?) the references you cited looked as though they concerned
antenna (a.k.a 'aerial') installations: some considerations that apply
to those aren't relevant to 'normal' indoor equipment on domestic
power-supplies, but you seem to believe that all the same 'concepts', to
use your word, apply to both.
> ... In the US, all utlities are required to have a building
> connection to earth ground. Any voltage difference between a
> utilities and earth is considered a threat to human life.
I don't see why: danger only arises when it's possible for the human to
find him/herself connected across the points at different potential.
Being inside an airplane when it's struck by lightning is no big deal,
for example, and 'hot wire working' on high-voltage transmission-lines
has become quite usual.
We do have the requirement that metal pipework, etc., for water/central
heating, and exposed structural metalwork, are bonded to power-line
earth, but whether that's at the same potential as a nearby buried plate
might be if one existed is a matter of indifference.
It's a matter of indifference to electronic equipment also: as I've
pointed out, modems, for example, only know/care about
potential-differences between phone-line earth and power-line earth.
> ... A rather confusing sentence:
> > If mains-powered equipment is hung on the 'lightning conductor'
> > there's no alternative but to grapple with the problems arising
> > when/if electrical storms (or even power-system faults) create
> > large potential differences between 'local earth' and
> > 'power-line earth'.
> I have no clue as to what was posted no matter how many times I
> readthis.
> When did we suddenly start connecting air terminals (lightning rods)
> onto electronic equipment?
When we first stuck aerial/antenna wires, masts, etc up towards the sky:
to a charged cloud 'if it looks like a lightning-conductor and acts like
a lightning-conductor it *is* a lightning-conductor', whatever the human
intentions.
> When did 'power line earth' not become earth ground
> which somehow is different from some new term called 'local ground'?
You may attach some particular meaning to 'earth ground', but I don't
recognise the term: AFAIK electrical 'ground' is just N. American for
what is 'earth' in English.
By 'Local earth' I meant a connection to, or the potential at, the real,
physical bit of the earth's surface on which the
equipment/building/person is standing: there may or may not be a buried
plate or rod to provide a more-or-less good connection, better on a
salt-water swamp than in sand or on rock, but the potential is a fact
either way.
By 'power line earth' I meant the wire (or sheathing/armour) provided by
the power-company along with those for phase(s) and neutral: it's
connected to the 'local earth' at the power-company's sub-station, which
is never exactly at the potential of the customer's local earth, and
during thunderstorms can (briefly) be very different.
'Phone-line earth' is similar, in that it's connected to the 'local
earth' at a phone-company location, not the customer's.
If there is a 'local earth' connection it's in the UK bonded to
power-line earth, but there's no requirement that one should exist, and
now that incoming water-supply pipes are mostly plastic they don't
incidentally act as such a connection.
> "When/if electrical storms create large potential differences" - is
> simplified by the term 'common mode surge'.
Like all jargon, it 'simplifies' only for the minority who understand
the far-from-self-evident meaning (and even then any two 'professionals'
are likely to give three contradictory translations into plain English).
> Then there is this paragraph:
> > The last sentence puts the preceding two in context: protection
> > against line-to-line surges doesn't depend on earthing, and
> > cheap/easy solutions are effective, if seldom necessary, against
> > transients likely to be encountered domestically-.
> What line-to-line surge? Where did a normal mode transients
> suddenly appear from?
A better question would IMO be 'Where did common-mode transients
suddenly appear from?'
This thread was about the blowing of a fuse when the failure of a
lamp-filament drew an arc between the support-wires: nothing 'common
mode' about that, and line-to-line transient-suppression (which you
dismiss as 'no protection') is all that could have been relevant.
Nevertheless, it again triggered the homily on the need for a good short
earth/ground connection that I'd taken issue with in the 'Modem faulty -
but what's faulty ?' thread, where it may have seemed more plausible.
> Typically destructive surges are common mode transients.
... which result in potential-differences between 'earth' at different
points: damage can only result to anything connected between two such
points, not to only one.
A modem inevitably sits between two different 'earths', power-line and
phone-line, and any transient-suppression must deal with voltages that
appear between them.
No 'improvement' to either earth-connection can help, and the addition
of a third, e.g. to 'local earth', will introduce surges of its own when
lightning strikes nearby.
> ... As for normal mode transients, they are so small as to be
> called noise.
Call them what you will, and they're IMO seldom of serious concern in
residential settings: when of 'industrial strength', however, they can
be quite nasty, e.g. when the circuit-breakers on heavy machinery are
tripped by overload.
--
Peter Duck <pd...@zetnet.co.uk>
w_tom
based installations, upon telephone switching stations (Central Office or
CO), and upon electric company power problems. In each case, all have
the equivalent of aerials covering wide areas just waiting to bring a surge
into the building. That destructive surge is a common mode transient. IOW
a surge seeks earth ground - what the 'local ground' connects into. It was
proven in the 1930s that if a surge was shunted to earth ground before it
got anywhere near electronic equipment, then surge damage did not occur.
IOW that meant a short path to earth ground and a longer separation between
that shunt and the electronics.
Homes are now connected to wires located everywhere - that collect surges
just like a BBC antenna (height has little relationship to this effect).
This incoming surge problem was not noticed 30 years ago but is now a
serious problem because transistors exist.
Differential mode surge protection - a line to line surge protector - is
useless for common mode surge protection. Even worse, differential mode
surge protection located adjacent to an appliance can even increase the
possibility of common mode surge damage - as explained earlier.
Local ground is also known as the earth ground. Effective surge
protection is so well understood that earth ground is described by this
British company (www.telematic.com) :
> Even the best surge protection device is of no use if
> incorrectly installed. Installation, and more specifically
> earthing, is a critical aspect of surge protection.
In the US, power line ground must connect to local earth, as noted by
R.P. Haviland, for human safety. Central earth ground, also known as the
single point ground window, or the MGB are a unique form of 'local ground'
that makes that ground also effective for surge protection - transistor
safety. As R.P. Haviland noted, we earth ground for three reasons (the last
two reasons especially apply to residences):
> - A path to the earth (ground) for RF
> - A path to ground for a lightning stroke
> - A path to ensure that the powerline is connected to earth.
This 'local ground' or 'earthing' has protected many homes from fire and
explosion in the US (local power company just explained a new house fire
that was caught by their emergency response team - a fire that was about to
begin on a cable TV wire because critical power line earth ground was
missing). A ground considered essential for both human safety and
transistor safety is not mandatory in the UK.
That 'local ground', once only installed for human safety, is also
effective for lightning protection IFF every incoming utility connects to a
single point 'local ground' less than 3 meters either direct or through a
surge protector AND this local ground is a best connection to earth.
Bonding equipment to a power line ground (where neutral meets green wire
safety ground in the circuit breaker box) only would be the reason for a gas
meter explosion below.
That ground connection wire can be long for human safety - a 'power line
ground' to 'local ground' (earth ground) connection. But to provide
lightning protection, the local ground connection must be less than 3
meters. Without that 'less than three meter' connection, then surge
protection cannot be effective - in the US or UK. Again, these lessons
learned from broadcast stations, COs, and power distribution systems since
the 1930s now applies even to residences - since the transistor is
ubiquitous even in homes.
Yes, a modem can be damaged when a voltage difference exists between power
line and telephone line. That is just what happens when either of two wires
is not connected short to 'local ground' and lightning strikes. If any one
incoming wire does not connect short to 'local ground' at the service
entrance, then a voltage difference, sufficient to damage telco appliances,
exists between power line and telephone line.
Of course we know this from fundamentals of surge protection proven since
the 1930s. No earth ground means no effective surge protection. The
world's best surge protection is useless without that critical earth ground
connection. These same principals also apply to air terminals (lightning
rods) which do the same function - shunt a common mode (lightning) surge to
earth ground before it can take a more destructive path into earth ground.
A surge protector is only one component of a surge protection 'system'.
Earth ground is another critical 'system' component. A plug-in surge
protector is simply one 'system' component with the rest of the 'system'
missing. Maybe the surge protector can protect from a differential mode
surge. But destructive surges, as so proven on 4 July in the UK, are common
mode. A surge protector is only as good as its earth ground. Why? Common
mode surges are so destructive. As repeatedly noted, that common mode surge
is not grounded if a connection 15+ meters away. With a ground connection
so long, then the surge will simply find other, destructive paths into
ground - often through electronic appliances. Wire is not a conductor - it
is an electronic component. Appreciate the technicals of this last sentence
to understand why the expression 'less than 3 meters' is important.
Most don't understand the difference between resistance and impedance.
Most think of wires as perfect conductors because they don't have sufficient
electrical background. But to surges, wire is not a conductor; it is an
electronic component. That characteristic for wire is why the connection to
earth ground must be 3 meters AND why even shorter distances make the entire
'system' more effective.
Local ground just for human safety as absolutely necessary, as will be
demonstrated again. One house, whose earth ground was disconnected,
exploded when a utility transformer neutral wire failure caused the home's
gas meter to explode. Fortunately no one was home during the explosion -
that occurred because critical 'local ground' was disconnected. Earth
ground was obtained through the gas pipeline until gas meter gaskets finally
failed. For surge protection, that earth ground must be upgraded. However
in the UK where 'local ground' is not mandatory, then how can any surge
protector work? It cannot.
A surge protector is only as good as its earth ground. No earth ground
means no effective surge protection. To understand fundamentals posted
above, one must have knowledge of common mode vs differential (normal) mode
transients, resistance vs impedance for wire, and that destructive surges
are common mode transients that destroy appliances (such as modems) by
creating voltage differences to complete a circuit connection into earth.
These terms are ubiquitous among engineers everywhere.
BTW, circuit breakers, fuses, etc do not trip to protect from surges.
They only trip because a surge has already performed the damage. Over 500
consecutive surges could occur before a circuit breaker or fuse even
considered tripping. Fused don't protect electronic equipment from damage.
They only protect from a fire or other hazards that would occur after the
electronics had been damaged.
Roy
MOVs are sacrificial devices, in that they absorb spikes and get damaged, with the
result that they
ultimately go short circuit through the metal oxide within getting burned. If the MOV
in your surge protector is not roasted (case burned), it will work.
Light bulbs sometimes strike up an arc between the electrodes, triggered by the high
temperature that results at the moment of blowing. The low gas pressure in the lamp
assists with the arc formation. Some lamps even include a fuse within the base of the
lamp. I recommend that you connect the lamp before your surge protector. The failure
of a lamp in the fashion you describe could cause a spike, and of course Windoze does not
like the power interruption.
Take care, Roy
To Reply, please remove the numeral before the @
"Nils Holland" <ni...@nightcastleproductions.org> wrote in message
> Hi folks,
>
> I'm using some cheap surge protector that I plug into an outlet in order to
> protect my computer from power surges. I don't know how efficient such a
> thing is. All I know is that it basically seems to consist of a 4 A fuse.
>
> Now, I have two questions about this:
>
> 1) Three devices are connected to the ciruit protected by the surge
> protector: My computer, the monitor, and a small 40 W light on my desktop.
> Now, yesterday the bulb in my desktop light burned out, and at the same
> time, it killed the fuse in my surge protector. Although I guess it's not
> really hard to explain, I'm still not really sure in what way the burning
> out light bulb blows the fuse. How can this be technically explained? Why
> doesn't the fude blow when normally turning on the light bulb?
>
> 2) When the light bulb killed my fuse, my computer was turned on, and so it
> of course lost power and crashed. Although the fuse in the surge protector
> in the circuit is supposed to protect my computer, I still cannot stop
> thinking about any negative effects this issue may have had on my computer.
> Although it's working fine, I wonder if at the time the light bulb burned
> out there was some kind of surge that could potentially have harmed my
> computer.
> Besides the obvious problem of possible data corruption when the power to
> the computer fails, I'm wondering if any more serious defetcs could be
> causes should the bulb in my light burn out again, and thus if it is wiser
> to put the light onto a different circuit (or at least not behind the surge
> protector, along with the computer).
> Nils
w_tom
before threshold voltage changes 10%. Properly installed MOVs never sacrifice- never burn or
vaporize. They just slowly fade away - but only if properly sized. That directly indicated
on MOV data sheets.
Grossly undersized surge protection is equipment is available with big brand names and big
digit warranties. The grossly undersized MOVs explode or vaporize. What do the many assume?
That MOVs are sacrificial devices. They 'feel' a conclusion rather than first do or read the
numbers. Reality: some surge protectors are so grossly undersized that MOVs vaporize when
confronted by surges too small to even damage a computer. What kind of protection is that?
Just enough to make the owner 'feel' that MOVs are sacrificial protection.
Joules is a ball park measurement of MOV life expectancy. Doubling the joules can increase
the 'number of surges' live expectancy by almost 10 times. This made obvious on MOV
manufacture data sheets. But most knowledge of surge protection comes only from observation
without knowledge of electrical basics. 'Feeling' is why most surge protection
recommendations are based on urban legends - not science. MOVs are not sacrificial components
- except in devices that are more than undersized - grossly undersized - and also grossly
overpriced in retail stores.