"Uncle Peter" wrote in message
news
On Tue, 25 Feb 2014 18:48:16 -0000, wrote:

On Tuesday, February 25, 2014 6:02:45 PM UTC, Uncle Peter wrote:
On Tue, 25 Feb 2014 17:54:32 -0000, wrote:
On Tuesday, February 25, 2014 5:21:05 PM UTC, Uncle Peter wrote:
On Tue, 25 Feb 2014 17:14:55 -0000, wrote:
On Monday, February 24, 2014 6:59:34 PM UTC, Uncle Peter wrote:

Then I guess the 4 quid surge protector is protecting several 40 quid
PSUs.

they dont protect anything, other than someone's profits

At 4 quid I very much doubt there is much profit. That includes postage
and packing and packaging and Ebay fees.

Of course there is, or they wouldnt be sold. Its basic capitalism
principles. You can get them in retail quantities for 50p last time I
looked.

It's not very much profit though is it?

I've got a spike arrestor on the phoneline too.

Overhead phone services already have those built in.

Youre buying into marketing bs and wasting your time.

Then why did my dad's network card burn out when he got lightning
through his phone line, through the router, and into the ethernet
port?

Presumably because it was hit by lightning. No tiny surge arrestor can
do anything about that.

It might do enough to reduce the effect.

You've got sometimes a billion plus volts crossing over a mile of air.
You've got maybe 300,000 amps. You've got a discharge path exceeding
50,000 degrees C. Do you seriously think a 1cm disc of any material on
earth is going to make the slightest difference?

So lightning protectors are a con? And they are legally sold? I don't
think so. Otherwise I could make up any old **** and stick it in a
plastic box and sell it.


All depends on how close the strike is. If you think some bit of electronic
crap is going to divert the Megawatts of power in a near strike, you want
your head looking.
Buildings can be protected with lightning conductors, maybe 250mm squ
conductor.
Your litte fartbox is worthless in such a situation.

The only real protection is disconnection in these situations. ie pull the
plugs (all of them) if you see lightning nearby.

"Uncle Peter" wrote in message
news On Mon, 24 Feb 2014 14:57:45 -0000, Steve wrote:

Uncle Peter presented the following explanation :
On Mon, 24 Feb 2014 14:15:06 -0000, Graham. wrote:

On Mon, 24 Feb 2014 13:48:25 -0000, "Uncle Peter" wrote:

I've got a few cheap micromark surge protectors, and noticed they have
a
clamping voltage of 650V.
Anyone know where I can get a much lower one? I've heard of protectors
as
low as 270V, but I can't find any to buy.

For 230V RMS?

Yes.

650 is the peal to peak equivalent, but I think it's just the peak
voltage that's relevant here, so anything less than 325v is no good,
and you are going to need some margin above that.

Don't know what micromark offer, but if it's just a few twopenny MOVs
I shouldn't bother.

This: http://petersphotos.com/temp/surge.jpg

It's to protect computers. Looking at other surge protectors up to 100
quid
(this one was 4 quid), nothing is lower than 650V. And some of the 100
quid
ones are 750V!

Am I right in thinking 650V is rubbish? I mean the surge could double
the
peak supply voltage without the protector doing anything, and if the
surge
was more, it would clamp it down to double, which is enough to **** up a
computer. Mind you if it's just the power supply caps that go bang, I
suppose it doesn't matter. Does a PC power supply stop surges getting
past
it?

Absolutely not! I've just done a partial rebuild of a gaming machine
for someone that has cost United Utilities (their electricity supplier)
over £1,500 after it was hit by a voltage surge - same house also had
two TVs and a microwave oven blow up too. And about twelve other houses
were affected so not a happy time for UU.

Maybe it depends how long the surge was. See my other post (reply to a
reply to yours) where a room full of computers was fine when connected to
two phases by mistake. Just the bulk capacitors in the PSUs blew. I've
also accidentally connected a printer and a computer to 240V instead of 110V
when the switch was incorrectly set at the back. Also I've seen about 10
computers with the switch set wrongly on purpose by kids. Just a bang and a
new capacitor required. I would have expected the fuse or breaker to blow
before the voltage got through to the equipment in your case though - the
bulk capacitors go short circuit?

A fuse can carry four times it's rated current for an hour before it melts.
MCBs are a bit better.

They are clumsy overcurrent devices, voltage makes no difference.
In no way will they protect electronic devices.
They are not anti-surge protectors.

"Uncle Peter" writes:

On Mon, 24 Feb 2014 15:24:57 -0000, Andrew Gabriel =
n.co.uk wrote:

In article ,
Steve writes:
Uncle Peter presented the following explanation :
On Mon, 24 Feb 2014 14:15:06 -0000, Graham. wrote:

On Mon, 24 Feb 2014 13:48:25 -0000, "Uncle Peter" wro=
te:

I've got a few cheap micromark surge protectors, and noticed they =
have a
clamping voltage of 650V.
Anyone know where I can get a much lower one? I've heard of prote=
ctors as
low as 270V, but I can't find any to buy.

For 230V RMS?

Yes.

650 is the peal to peak equivalent, but I think it's just the peak
voltage that's relevant here, so anything less than 325v is no good=
,
and you are going to need some margin above that.

Don't know what micromark offer, but if it's just a few twopenny MO=
Vs
I shouldn't bother.

This: http://petersphotos.com/temp/surge.jpg

It's to protect computers. Looking at other surge protectors up to =
100 quid
(this one was 4 quid), nothing is lower than 650V. And some of the =
100 quid
ones are 750V!

Am I right in thinking 650V is rubbish? I mean the surge could doub=
le the
peak supply voltage without the protector doing anything, and if the=
surge
was more, it would clamp it down to double, which is enough to **** =
up a
computer. Mind you if it's just the power supply caps that go bang,=
I
suppose it doesn't matter. Does a PC power supply stop surges getti=
ng past
it?

Absolutely not! I've just done a partial rebuild of a gaming machine
for someone that has cost United Utilities (their electricity supplie=
r)
over =A31,500 after it was hit by a voltage surge - same house also h=
ad
two TVs and a microwave oven blow up too. And about twelve other hous=
es
were affected so not a happy time for UU.

This sounds like a loss of neutral fault, and a MOV is useless for
protecting against such a sustained fault - it will just burst into
flames if the fault goes over the clamping voltage (and they have
been known to start fires).

I've seen that. At my 2nd last place of work, an electrician mixed up t=
he wiring as they had some old colours and some new, causing L1 and L2 t=
o be connected to a ring of 13A sockets instead of L1 and neutral. A su=
rge protected plug on a digital projector melted, and the bulk capacitor=
s in all 20 computers in the room burst (they had no surge protectors), =
giving off some stinky smoke. All this tripped the circuit breaker for =
the room, which presumably stopped any further damage or a fire. After =
I replaced all the capacitors, the computers were fine.

Consequently, the MOV must have a clamping voltage above the 3-phase
peak of 570V.

Why? If I get a momentary spike or surge between single phase peak and =
three phase peak, I want it removed. Also one above the 3-phase peak I =
want clamped down to the 1-phase peak, not the 3-phase peak!

Secondly, each time it takes a significant spike, its
clamping voltage drops a bit, and it must still remain over 570V after=

this.

The device is used up a bit by each spike (unless the spike is tiny).

Finally, a MOV (or any surge supression) just across live and neutral
is remarkably ineffective for protecting against lightning, where the
spike tends to be between different services, such as the phone line
and mains, or mains and ground, etc. and not between live and neutral.=


This one claims to be across any pair of pins. I thought they all were.=


It won't generally protect against broken neutral (which sees the main=
s
voltage rise to up to 400V).

Why does it rise? If there was no neutral, and the load on all three ph=
ases was equal, nobody would notice. You'd get a rise (or fall) if your=
phase was not the same as the other two.

Just what is it you are trying to protect against?

A spike or surge. I don't want it just trimmed to 650V! The spike is s=
till there!!

These MOVs are not as low in impedance as for example a zener diode.
They're more of a voltage-variable resistor; the resistance goes down
as the voltage increases.

Zeners clip more sharply, but they too just have a (sharply) lower
resistance as the voltage increases, and they're usually more fragile
than MOVs for just that reason; the current can quickly rise to very
high levels.

The spike will always still be there, no matter what you do.

You could get better clipping by using a lower voltage MOV, but that
would mean that it would be drawing some current even when there was no
spike, and it would be likely to overheat and to either catch fire or
become useless.

One could conceive of an active clipping device whose clipping voltage
tracked the instantaneous voltage of the mains supply and reduced any
spikes to just a few volts above the voltage at that point in the sine
wave, but it would be expensive, failure-prone and pointless for most
purposes.

If you want to reduce spikes of only a few microseconds in duration
(which is the width of many spikes) a low pass filter will do that, and
because such a filter is just inductors and capacitors it is a
robust device. More expensive than an MOV though.

In the years before MOVs, filters of that type were standard on early
DEC10 mainframes and DEC minicomputers - but when the power line was
very long and there were typical Canadian lightning storms in the area,
equipment still died.

--
Windmill, Use t m i l l
J.R.R. Tolkien:- @ S c o t s h o m e . c o m
All that is gold does not glister / Not all who wander are lost

"Uncle Peter" writes:

On Mon, 24 Feb 2014 15:58:18 -0000, Capitol wrote:

Uncle Peter wrote:
On Mon, 24 Feb 2014 14:15:06 -0000, Graham. wrote:

On Mon, 24 Feb 2014 13:48:25 -0000, "Uncle Peter" wrote:

I've got a few cheap micromark surge protectors, and noticed they
have a clamping voltage of 650V.
Anyone know where I can get a much lower one? I've heard of
protectors as low as 270V, but I can't find any to buy.

For 230V RMS?

Yes.

650 is the peal to peak equivalent, but I think it's just the peak
voltage that's relevant here, so anything less than 325v is no good,
and you are going to need some margin above that.

Don't know what micromark offer, but if it's just a few twopenny MOVs
I shouldn't bother.

This: http://petersphotos.com/temp/surge.jpg

It's to protect computers. Looking at other surge protectors up to 100
quid (this one was 4 quid), nothing is lower than 650V. And some of the
100 quid ones are 750V!

Am I right in thinking 650V is rubbish? I mean the surge could double
the peak supply voltage without the protector doing anything, and if the
surge was more, it would clamp it down to double, which is enough to
**** up a computer. Mind you if it's just the power supply caps that go
bang, I suppose it doesn't matter. Does a PC power supply stop surges
getting past it?

Or.... does 650V mean peak to peak as opposed to zero to peak?

Computers are designed to withstand about 2.5KV spikes and survive
minor lightning strikes. A 650V surge protector is quite adeaquate, but
might not last long as my local supply frquently gets 1500V fast
transients (microseconds), zero to peak. The surge protector is
bidirectional, ie it doesn't care which way round the volts are. The
current flowing is purely determined by the source impedance, which for
lightning strikes is close to zero if local.

No, the current flowing depends also and usually mainly on the V/I
curve of the surge protector, which for an MOV shows a fairly gradual
increase in current at first but increasing more or less exponentially
as the voltage rises.
Current through the zener diode type of surge limiter rises faster, but
they're still not a zero resistance.

For interference spikes,
surge protectors work OK, but if your supply is cables in the air, then
they may well fail quite soon.

They're cheap, I don't care, and they have an LED to indicate they're still running.

My worst experiences have been "brown
outs", where the supply suddenly reverses phase or skips cycles, which
causes transformer saturation and doubles the peak supply volts(up to
700V zero to peak) for a cycle, which then takes a few cycles to settle
down. This also buggers up switched mode PSUs, which don't like having
their dc supply briefly doubled. If this happens, no surge protector
will operate correctly and survive.

Explain how the phase can get reversed?

And why not have a surge protector that absorbs anything over 340V? Yes it wouldn't protect an extended double voltage, but it would remove more of the spikes.

IME, unless you have a transformer
fed supply with a good UPS you are going to lose a few PSUs with the
current state of our electricity supply. I lost a couple last year. Just
be thankful you are not in the US, where lightning strikes are common
and the supply is frequently crap as well.

I've got a good UPS on the only computer with data on it, but that was mainly to stop it going off if there was a short powercut for a second or two, which I get a lot of in bad weather. I've never known a power supply break here.

--
Windmill, Use t m i l l
J.R.R. Tolkien:- @ S c o t s h o m e . c o m
All that is gold does not glister / Not all who wander are lost

Fredxxx writes:

On 24/02/2014 13:48, Uncle Peter wrote:
I've got a few cheap micromark surge protectors, and noticed they have a
clamping voltage of 650V.
Anyone know where I can get a much lower one? I've heard of protectors
as low as 270V, but I can't find any to buy.

I feel you are on a loser here. Most power supplies can withstand modest
surges in their own right.

Surge protectors offer minimal protection, though I guess any is better
than none.

The voltages you quote are way of the mark. 650V is chosen for perfectly
good reasons.

If you want true protections then you should be looking at an Online UPS.

Of course the UPS may fail because of a spike|

--
Windmill, Use t m i l l
J.R.R. Tolkien:- @ S c o t s h o m e . c o m
All that is gold does not glister / Not all who wander are lost

In article , harryagain
wrote:

"Uncle Peter" wrote in message
news
On Tue, 25 Feb 2014 18:48:16 -0000, wrote:

On Tuesday, February 25, 2014 6:02:45 PM UTC, Uncle Peter wrote:
On Tue, 25 Feb 2014 17:54:32 -0000, wrote:
On Tuesday, February 25, 2014 5:21:05 PM UTC, Uncle Peter wrote:
On Tue, 25 Feb 2014 17:14:55 -0000, wrote:
On Monday, February 24, 2014 6:59:34 PM UTC, Uncle Peter wrote:

Then I guess the 4 quid surge protector is protecting several 40
quid PSUs.

they dont protect anything, other than someone's profits

At 4 quid I very much doubt there is much profit. That includes
postage and packing and packaging and Ebay fees.

Of course there is, or they wouldnt be sold. Its basic capitalism
principles. You can get them in retail quantities for 50p last time I
looked.

It's not very much profit though is it?

I've got a spike arrestor on the phoneline too.

Overhead phone services already have those built in.

Youre buying into marketing bs and wasting your time.

Then why did my dad's network card burn out when he got lightning
through his phone line, through the router, and into the ethernet
port?

Presumably because it was hit by lightning. No tiny surge arrestor
can do anything about that.

It might do enough to reduce the effect.

You've got sometimes a billion plus volts crossing over a mile of air.
You've got maybe 300,000 amps. You've got a discharge path exceeding
50,000 degrees C. Do you seriously think a 1cm disc of any material on
earth is going to make the slightest difference?

So lightning protectors are a con? And they are legally sold? I don't
think so. Otherwise I could make up any old **** and stick it in a
plastic box and sell it.


All depends on how close the strike is. If you think some bit of
electronic crap is going to divert the Megawatts of power in a near
strike, you want your head looking. Buildings can be protected with
lightning conductors, maybe 250mm squ conductor. Your litte fartbox is
worthless in such a situation.

The only real protection is disconnection in these situations. ie pull
the plugs (all of them) if you see lightning nearby.

and - if it strikes your house when you are in the act of pulling them?

--
From KT24

Using a RISC OS computer running v5.18

"Uncle Peter" writes:

On Mon, 24 Feb 2014 16:59:24 -0000, Fredxxx wrote:

On 24/02/2014 13:48, Uncle Peter wrote:
I've got a few cheap micromark surge protectors, and noticed they have a
clamping voltage of 650V.
Anyone know where I can get a much lower one? I've heard of protectors
as low as 270V, but I can't find any to buy.

I feel you are on a loser here. Most power supplies can withstand modest
surges in their own right.

Surge protectors offer minimal protection, though I guess any is better
than none.

The voltages you quote are way of the mark. 650V is chosen for perfectly
good reasons.

What are the reasons? I can't find any details about clamping voltage
online, just a brief description of what it is.

The varistors a.k.a. MOVs I'm familiar with have manufacturers'
designations like V130LA20 (rated for 120 volt AC use) and V275LA20
(rated for 240v. AC use).

You should be able to find voltage/current curves on the manufacturer's
spec sheet which will show you what current flows at a given voltage.

ISTR that they also give a 'clamping voltage' which doesn't really mean
what it says; it's just defined as that voltage at which a certain
current will flow (maybe 100 amps? I don't have the data at hand.)

I think the '20' part of the number means it can handle 20 joules. (Once?)
Which isn't a lot.
But it's a long time since I looked at the figures.

--
Windmill, Use t m i l l
J.R.R. Tolkien:- @ S c o t s h o m e . c o m
All that is gold does not glister / Not all who wander are lost

replying to Peter Crosland , westom wrote:
johnwilliamson wrote:
That's as may be, but they tend to have rather better quality protection
on all their connections than a cheapie "surge protected" 13A strip with
a tuppenny MOV in it.


Described was a simple and well proven solution used in radio stations,
telco switching centers, and even munitions dumps so that surges
(including direct lightning strikes) do not cause damage. Quite a few
here are posting denials based in feelings; not justified by any
professional source, personal experience, or basic electrical concepts.

For example, an average lightning strike is about 20,000 amps. And is
routinely made irrelevant by a properly connection to earth. Lightning can
be as high as 100,000 amps. So rare that most here have probably never
seen one. Meanwhile an IEEE paper in the late 1970s says what happens
when a rare 100,000 amp lightning strike hits incoming AC wires. 40,000
typically goes to earth via the 'primary' protection system (including the
earth ground for each transformer). Another 20,000 amps may go off to
other connections. And 40,000 amps may be incoming to the nearby
building. Why do professionals recommend at least 50,000 amps protector
for 'secondary' protection? Numbers published by professionals define the
problem.

tony wrote:
No, they do sometimes dissipate a charge before it builds up to form a
much bigger discharge...


Good luck finding even one responsible source (ie IEEE, NFPA, FAA, BS,
ISO, etc) that makes that claim. ESE devices have long been cited by
professional sources as, at best, unproven.

Nothing stops lightning. And yet that is what adjacent protectors or ESE
devices must do.

In any facility that cannot have damage, protection has always been about
connecting surges (such as lightning) harmlessly to earth. Lightning rods
do that to protect structures. Dedicated ground wires or 'whole house'
protector to utility wires does that to protect interio appliances. In
every case, protection is always about making a more conductive and lower
impedance connection to earth. Earth is where hundreds of thousands of
joules harmlessly dissipate.

Devices that claim to block, absorb, or avert surges such as lightning
(ie series mode filter, plug-in protectors, ESE devices, magic boxes that
claim to convert tiny surges into useful energy) are bogus. As indicated
by claims even contradicted or not supported by manufacturer
specifications. Voting is useless. since an only useful recommendation
says why with numbers. As found in professional papers and manufacturer
specifications.

Telco switching centers all over the world use properly earthed 'whole
house' protectors. Since that less expensive and superior solution is
also proven by over 100 years os science and experience. Similar solutions
also implemented in muntions dumps since explosions are unacceptable. No
other device (not even ESE) have that credibility. Protection is and has
been always about the quality of and connection to earth.

Should you want more, well, ask and be buried in professional citations
and case studies. But then only a fewest here actually did this stuff.
And have describes in siginifcant detail and numbers how and why those
proven solutoins work.

The protector at 650 volts means it starts doing protection at 650
volts. If a surge current is larger, voltage on that protector increases
to over 1000 volts (current, not voltage, is the relevant parameter).
Eventually that voltage becomes so high that a protector fails
catastrophically. How high might voltage go? That is why the 'whole
house' protector starts at 50,000 amps. Another example of how to
separate hearsay from experience. Experiences describes concepts with
well proven numbers traceable to responsible sources.


--

replying to Peter Crosland , westom wrote:
g6jns wrote:
The reality is that these surge protectors offer very little, if any,
protection against lightning strikes. A lightning strike close by can
kill your electronic equipment regardless of what protection you have.


--
And then an engineer who did this stuff cites experience tempered by
knowledge. A lightning strike (maybe 20,000 amps) stuck the building's
lightning rod That wire to earth was only four feet away from an IBM PC.
The PC did not even blink. Nothing inside was interrupted or damaged by
20,000 amps on a nearby wire. If nearby strikes are destructive, that PC
should have been damaged or at least only crashed. It was not for one
simple reason. Only wild speculation says nearby strikes create massive
fields that do damage.

Another example. Lightning must connect a cloud to earthborne charges
maybe 5 kilometers distant. A shortest electrical path is three km down
to a tree. And 4 km through earth to those charges. Only 10 meters from
that tree was a dead cow. Did the nearby bolt create fields that killed
the cow? Those who know from speculation assumed so. Science says
something completely different.

A shortest 4 km path from tree to distant charges was up the cow's hind
legs and down its fore legs. What others assumed was a nearby strike was
actually a direct strike to a tree and cow.

Nearby strikes are only destructive when wild speculation creates a
conclusion. Knowledge comes from first learning 100 years of well proven
science - and demanding numbers.

Any golfers? What happened to that cow should also have your attention.


--

On Fri, 28 Feb 2014 22:45:02 +0000, westom
wrote:

replying to Peter Crosland , westom wrote:
g6jns wrote:
The reality is that these surge protectors offer very little, if any,
protection against lightning strikes. A lightning strike close by can
kill your electronic equipment regardless of what protection you have.


--
And then an engineer who did this stuff cites experience tempered by
knowledge. A lightning strike (maybe 20,000 amps) stuck the building's
lightning rod That wire to earth was only four feet away from an IBM PC.
The PC did not even blink. Nothing inside was interrupted or damaged by
20,000 amps on a nearby wire. If nearby strikes are destructive, that PC
should have been damaged or at least only crashed. It was not for one
simple reason. Only wild speculation says nearby strikes create massive
fields that do damage.

Another example. Lightning must connect a cloud to earthborne charges
maybe 5 kilometers distant. A shortest electrical path is three km down
to a tree. And 4 km through earth to those charges. Only 10 meters from
that tree was a dead cow. Did the nearby bolt create fields that killed
the cow? Those who know from speculation assumed so. Science says
something completely different.

A shortest 4 km path from tree to distant charges was up the cow's hind
legs and down its fore legs. What others assumed was a nearby strike was
actually a direct strike to a tree and cow.

Nearby strikes are only destructive when wild speculation creates a
conclusion. Knowledge comes from first learning 100 years of well proven
science - and demanding numbers.

Any golfers? What happened to that cow should also have your attention.

W_Tom, I'm not quite sure what you're trying to put across with the
tree and cow example. From the details you gave, cow showing post
mortem signs that the electrocuting charge had passed between the fore
and hindlegs whilst a mere 33 feet away from the ground strike point
(the hapless tree), suggest the cow was either facing towards or away
from the tree at the time and was killed by the potential gradient
created by the lightning strike in the ground it was standing on[1].

There is video evidence[2] of this effect exemplified by half the
players on a sodden football pitch being stunned by a direct hit to
the metalwork of the grandstand creating perhaps a kilovolt or more
per metre voltage gradient on the pitch.

Any players who happened to have both feet in contact with the ground
would have suffered an electric shock varying in intensity which
depended not only how far they were from the (effective) entry point
of the lightning strike but also their orientation and the seperation
distance of their feet.

Those lucky enough to have both feet out of contact at the critical
moment would have felt nothing, others who happened to have just one
foot in ground contact would have experienced a lesser electric shock
through that foot which would have also varied according to
orientation and distance from the strike point.

[1] Possibly a 'ground leader' but most likely due to Ground Current
or "Step Potential" as quoted from the wiki article here (second
paragraph):

http://en.wikipedia.org/wiki/Lightning_strike

[2] Surprisingly, I can't track this video down. It seems to have been
'pulled' despite there being no fatalities in this case. My memory of
the video suggests it was the second non-fatal incident reported he

http://news.bbc.co.uk/1/hi/world/africa/203137.stm

--
Regards, J B Good

replying to Johny B Good , westom wrote:
johnny-b-good wrote:
I'm not quite sure what you're trying to put across with the
tree and cow example. From the details you gave, cow showing post
mortem signs that the electrocuting charge had passed between the fore
and hindlegs whilst a mere 33 feet away from the ground strike point
(the hapless tree), suggest the cow was either facing towards or away
from the tree at the time and was killed by the potential gradient
created by the lightning strike in the ground


No harmful gradient from a field existed as many assume with a term
'induced surge'. Had a cow been on the other side of that tree, then
current would not have flowed up its hind legs and down its fore legs.

Destructive current had to be incoming on one path and outgoing on
another. Induced transients (E-M gradients) do not cause damage or death.
Actual current from a lightning strike must pass through (with an
incoming and outgoing path) to cause damage. Damage is defijned by where
current flows.

Another example. A nearby lightning strike hit l0 meters from a long
wire antenna. Thousands of volts appear on that antenna's lead. Connect
a NE-2 glow lamp (a milliamp lamp) to that antenna lead. The resulting
current is so tiny as to barely cause that light to glow. And voltage
drops from thousands to tens of volts.

Many see thousands of volts to assume a nearby surge is destrutive.
Conduct a millimap or less to make that induced surge completely
irrelevant. Induces surges are that easily eliminated. Simplest
protection in all electronics means no damage from nearby strikes. To
have damage means the item is part of that surge current path. That
defines both an incoming and outgoing current path.

Farmers encircle barns with a buried ground loop. So that current from
a lightning strike passes around the barn; not destructively through
animals inside. Protection is always about where current flows; or does
not flow.

Your wikipedia citation is discussing a lightning bolt - the plasma
'wire'. We are discussing what actually does damage - an electrical
current. Simultaneous current is same in the 'direct' lightning bolt and
'indirect' bolt. Relevent here is that actual electrical current. Either
current is created by a nearby, induced or indirect surge (generated by
electromagnetic fields). Or a current is what flows directly from cloud
to distant charnges. Latter is the current that causes hardware damage.

Earth a protector so that the current does not flow incoming and outgoing
through any appliance. Then nearby strikes (with massive E-M fields)
cause no damage.


--

On Sat, 01 Mar 2014 01:52:41 +0000, Johny B Good wrote:

W_Tom, I'm not quite sure what you're trying to put across with the
tree and cow example. From the details you gave, cow showing post
mortem signs that the electrocuting charge had passed between the fore
and hindlegs whilst a mere 33 feet away from the ground strike point
(the hapless tree), suggest the cow was either facing towards or away
from the tree at the time and was killed by the potential gradient
created by the lightning strike in the ground it was standing on

I wonder if cattle are as susceptible as horses. Quite recently there was a
case of a racehorse killed by a mains leak underground. That would have been
a much lower voltage gradient than a lightning strike, but apparently horses
are far more sensitive to this than are human beings.
--
Peter.
The gods will stay away
whilst religions hold sway

Farmers encircle barns with a buried ground loop. So that current from
a lightning strike passes around the barn; not destructively through
animals inside. Protection is always about where current flows; or does
not flow.


We _must_ have W_Tom back again as no farmer in England would do
anything to protect their cows like that!..

All in its just a very simple shunt job to shunt the lightning discharge
around what it is you need to protect. Use a low resistance and as low
INDUCTANCE a path as possible and thats more or less that..

That bit re lightning charge dissipation came from a handbook provided
by Messers Furse of Nottingham who have been making lightning protection
systems for use world-wide for some 120 odd years now!..


--
Tony Sayer

That would be a low *impeadence* path then.

On Fri, 28 Feb 2014 10:06:23 -0000, harryagain wrote:


"Uncle Peter" wrote in message
news
On Mon, 24 Feb 2014 14:15:06 -0000, Graham. wrote:

On Mon, 24 Feb 2014 13:48:25 -0000, "Uncle Peter" wrote:

I've got a few cheap micromark surge protectors, and noticed they have a
clamping voltage of 650V.
Anyone know where I can get a much lower one? I've heard of protectors
as low as 270V, but I can't find any to buy.

For 230V RMS?

Yes.

650 is the peal to peak equivalent, but I think it's just the peak
voltage that's relevant here, so anything less than 325v is no good,
and you are going to need some margin above that.

Don't know what micromark offer, but if it's just a few twopenny MOVs
I shouldn't bother.

This: http://petersphotos.com/temp/surge.jpg

It's to protect computers. Looking at other surge protectors up to 100
quid (this one was 4 quid), nothing is lower than 650V. And some of the
100 quid ones are 750V!

Am I right in thinking 650V is rubbish? I mean the surge could double the
peak supply voltage without the protector doing anything, and if the surge
was more, it would clamp it down to double, which is enough to **** up a
computer. Mind you if it's just the power supply caps that go bang, I
suppose it doesn't matter. Does a PC power supply stop surges getting
past it?

Or.... does 650V mean peak to peak as opposed to zero to peak?


RMS=Root of the Mean Squared.
It gives the equivalent of the DC for the purpose of calculating power usage
etc.

It is the peak voltage x 0.707 = RMS voltage (but only for sine waves).

So if you have 650Vpeak, the RMS value will be 460V

Mains power 230 volts (RMS) peak value is 325 volts.

So the cable insulation has to stand 325 volts.

For square waves the factor is 0.5

Yes, so I'm only preventing something that's more than double the standard voltage getting through.

--
Prostration - the act of exposing your genitalia to your god.

On Fri, 28 Feb 2014 10:13:49 -0000, harryagain wrote:


"Uncle Peter" wrote in message
news
On Tue, 25 Feb 2014 17:14:55 -0000, wrote:

On Monday, February 24, 2014 6:59:34 PM UTC, Uncle Peter wrote:


Ok, I'll assume I've protected the computers well enough then.

The designer & manufacturer of the PC PSU has done that.

Then I guess the 4 quid surge protector is protecting several 40 quid
PSUs.

I've got a spike arrestor on the phoneline too.

Overhead phone services already have those built in.

Youre buying into marketing bs and wasting your time.

Then why did my dad's network card burn out when he got lightning through
his phone line, through the router, and into the ethernet port?

No little bit of electronic bollix will resist a nearby lighning strike.

It must have been a very small part of the strike, as only the network card died. Now if the network card can save the motherboard, why can't a surge protector?

--
Gary's weather forecasting stone:
Stone is wet Rain
Stone is dry Not raining
Shadow on ground Sunny
White on top Snowing
Can't see stone Foggy
Swinging stone Windy
Stone jumping up and down Earthquake
Stone gone Tornado

On Fri, 28 Feb 2014 10:30:01 -0000, harryagain wrote:


"Uncle Peter" wrote in message
news On Mon, 24 Feb 2014 14:57:45 -0000, Steve wrote:

Uncle Peter presented the following explanation :
On Mon, 24 Feb 2014 14:15:06 -0000, Graham. wrote:

On Mon, 24 Feb 2014 13:48:25 -0000, "Uncle Peter" wrote:

I've got a few cheap micromark surge protectors, and noticed they have
a
clamping voltage of 650V.
Anyone know where I can get a much lower one? I've heard of protectors
as
low as 270V, but I can't find any to buy.

For 230V RMS?

Yes.

650 is the peal to peak equivalent, but I think it's just the peak
voltage that's relevant here, so anything less than 325v is no good,
and you are going to need some margin above that.

Don't know what micromark offer, but if it's just a few twopenny MOVs
I shouldn't bother.

This: http://petersphotos.com/temp/surge.jpg

It's to protect computers. Looking at other surge protectors up to 100
quid
(this one was 4 quid), nothing is lower than 650V. And some of the 100
quid
ones are 750V!

Am I right in thinking 650V is rubbish? I mean the surge could double
the
peak supply voltage without the protector doing anything, and if the
surge
was more, it would clamp it down to double, which is enough to **** up a
computer. Mind you if it's just the power supply caps that go bang, I
suppose it doesn't matter. Does a PC power supply stop surges getting
past
it?

Absolutely not! I've just done a partial rebuild of a gaming machine
for someone that has cost United Utilities (their electricity supplier)
over £1,500 after it was hit by a voltage surge - same house also had
two TVs and a microwave oven blow up too. And about twelve other houses
were affected so not a happy time for UU.

Maybe it depends how long the surge was. See my other post (reply to a
reply to yours) where a room full of computers was fine when connected to
two phases by mistake. Just the bulk capacitors in the PSUs blew. I've
also accidentally connected a printer and a computer to 240V instead of 110V
when the switch was incorrectly set at the back. Also I've seen about 10
computers with the switch set wrongly on purpose by kids. Just a bang and a
new capacitor required. I would have expected the fuse or breaker to blow
before the voltage got through to the equipment in your case though - the
bulk capacitors go short circuit?

A fuse can carry four times it's rated current for an hour before it melts.
MCBs are a bit better.

They are clumsy overcurrent devices, voltage makes no difference.
In no way will they protect electronic devices.
They are not anti-surge protectors.

Well every single time I've seen a PSU's bulk caps explode because of double voltage input, the 5A fuse in the IEC lead has blown.

--
Everybody is ignorant, only on different subjects.

On Fri, 28 Feb 2014 11:01:35 -0000, charles wrote:

In article , harryagain
wrote:

"Uncle Peter" wrote in message
news
On Tue, 25 Feb 2014 18:48:16 -0000, wrote:

On Tuesday, February 25, 2014 6:02:45 PM UTC, Uncle Peter wrote:
On Tue, 25 Feb 2014 17:54:32 -0000, wrote:
On Tuesday, February 25, 2014 5:21:05 PM UTC, Uncle Peter wrote:
On Tue, 25 Feb 2014 17:14:55 -0000, wrote:
On Monday, February 24, 2014 6:59:34 PM UTC, Uncle Peter wrote:

Then I guess the 4 quid surge protector is protecting several 40
quid PSUs.

they dont protect anything, other than someone's profits

At 4 quid I very much doubt there is much profit. That includes
postage and packing and packaging and Ebay fees.

Of course there is, or they wouldnt be sold. Its basic capitalism
principles. You can get them in retail quantities for 50p last time I
looked.

It's not very much profit though is it?

I've got a spike arrestor on the phoneline too.

Overhead phone services already have those built in.

Youre buying into marketing bs and wasting your time.

Then why did my dad's network card burn out when he got lightning
through his phone line, through the router, and into the ethernet
port?

Presumably because it was hit by lightning. No tiny surge arrestor
can do anything about that.

It might do enough to reduce the effect.

You've got sometimes a billion plus volts crossing over a mile of air.
You've got maybe 300,000 amps. You've got a discharge path exceeding
50,000 degrees C. Do you seriously think a 1cm disc of any material on
earth is going to make the slightest difference?

So lightning protectors are a con? And they are legally sold? I don't
think so. Otherwise I could make up any old **** and stick it in a
plastic box and sell it.


All depends on how close the strike is. If you think some bit of
electronic crap is going to divert the Megawatts of power in a near
strike, you want your head looking. Buildings can be protected with
lightning conductors, maybe 250mm squ conductor. Your litte fartbox is
worthless in such a situation.

The only real protection is disconnection in these situations. ie pull
the plugs (all of them) if you see lightning nearby.

and - if it strikes your house when you are in the act of pulling them?

Do a rave dance.

--
An expert is someone who takes a subject you understand and makes it sound confusing.

On Fri, 28 Feb 2014 10:23:17 -0000, harryagain wrote:


"Uncle Peter" wrote in message
news
On Tue, 25 Feb 2014 18:48:16 -0000, wrote:

On Tuesday, February 25, 2014 6:02:45 PM UTC, Uncle Peter wrote:
On Tue, 25 Feb 2014 17:54:32 -0000, wrote:
On Tuesday, February 25, 2014 5:21:05 PM UTC, Uncle Peter wrote:
On Tue, 25 Feb 2014 17:14:55 -0000, wrote:
On Monday, February 24, 2014 6:59:34 PM UTC, Uncle Peter wrote:

Then I guess the 4 quid surge protector is protecting several 40 quid
PSUs.

they dont protect anything, other than someone's profits

At 4 quid I very much doubt there is much profit. That includes postage
and packing and packaging and Ebay fees.

Of course there is, or they wouldnt be sold. Its basic capitalism
principles. You can get them in retail quantities for 50p last time I
looked.

It's not very much profit though is it?

I've got a spike arrestor on the phoneline too.

Overhead phone services already have those built in.

Youre buying into marketing bs and wasting your time.

Then why did my dad's network card burn out when he got lightning
through his phone line, through the router, and into the ethernet
port?

Presumably because it was hit by lightning. No tiny surge arrestor can
do anything about that.

It might do enough to reduce the effect.

You've got sometimes a billion plus volts crossing over a mile of air.
You've got maybe 300,000 amps. You've got a discharge path exceeding
50,000 degrees C. Do you seriously think a 1cm disc of any material on
earth is going to make the slightest difference?

So lightning protectors are a con? And they are legally sold? I don't
think so. Otherwise I could make up any old **** and stick it in a
plastic box and sell it.


All depends on how close the strike is. If you think some bit of electronic
crap is going to divert the Megawatts of power in a near strike, you want
your head looking.
Buildings can be protected with lightning conductors, maybe 250mm squ
conductor.
Your litte fartbox is worthless in such a situation.

The only real protection is disconnection in these situations. ie pull the
plugs (all of them) if you see lightning nearby.

It'll protect the smaller ones. You might as well say why wear a seatbelt? I mean it won't protect you when you slam at 70mph into an oncoming lorry.

--
An expert is someone who takes a subject you understand and makes it sound confusing.

On Saturday, March 1, 2014 5:37:39 PM UTC, Uncle Peter wrote:
On Fri, 28 Feb 2014 10:23:17 -0000, harryagain wrote:
"Uncle Peter" wrote in message
news
On Tue, 25 Feb 2014 18:48:16 -0000, wrote:


You've got sometimes a billion plus volts crossing over a mile of air.
You've got maybe 300,000 amps. You've got a discharge path exceeding
50,000 degrees C. Do you seriously think a 1cm disc of any material on
earth is going to make the slightest difference?

So lightning protectors are a con? And they are legally sold? I don't
think so. Otherwise I could make up any old **** and stick it in a
plastic box and sell it.

All depends on how close the strike is. If you think some bit of electronic
crap is going to divert the Megawatts of power in a near strike, you want
your head looking.
Buildings can be protected with lightning conductors, maybe 250mm squ
conductor.
Your litte fartbox is worthless in such a situation.

The only real protection is disconnection in these situations. ie pull the
plugs (all of them) if you see lightning nearby.

It'll protect the smaller ones.

funny


NT

In article ,
Graham. scribeth thus
That would be a low *impeadence* path then.

To be sure soir!! it would indeed...
--
Tony Sayer

On Sat, 01 Mar 2014 18:24:34 -0000, wrote:

On Saturday, March 1, 2014 5:37:39 PM UTC, Uncle Peter wrote:
On Fri, 28 Feb 2014 10:23:17 -0000, harryagain wrote:
"Uncle Peter" wrote in message
news On Tue, 25 Feb 2014 18:48:16 -0000, wrote:


You've got sometimes a billion plus volts crossing over a mile of air.
You've got maybe 300,000 amps. You've got a discharge path exceeding
50,000 degrees C. Do you seriously think a 1cm disc of any material on
earth is going to make the slightest difference?

So lightning protectors are a con? And they are legally sold? I don't
think so. Otherwise I could make up any old **** and stick it in a
plastic box and sell it.

All depends on how close the strike is. If you think some bit of electronic
crap is going to divert the Megawatts of power in a near strike, you want
your head looking.
Buildings can be protected with lightning conductors, maybe 250mm squ
conductor.
Your litte fartbox is worthless in such a situation.

The only real protection is disconnection in these situations. ie pull the
plugs (all of them) if you see lightning nearby.

It'll protect the smaller ones.

funny

Well my dad's network card protected his computer from a smaller one. You do understand that there isn't just one main lightning bolt don't you?

--
What's soft and warm when you go to bed, but hard and stiff when you wake up?
Vomit.

On Fri, 28 Feb 2014 11:00:29 -0000, Windmill wrote:

Fredxxx writes:

On 24/02/2014 13:48, Uncle Peter wrote:
I've got a few cheap micromark surge protectors, and noticed they have a
clamping voltage of 650V.
Anyone know where I can get a much lower one? I've heard of protectors
as low as 270V, but I can't find any to buy.

I feel you are on a loser here. Most power supplies can withstand modest
surges in their own right.

Surge protectors offer minimal protection, though I guess any is better
than none.

The voltages you quote are way of the mark. 650V is chosen for perfectly
good reasons.

If you want true protections then you should be looking at an Online UPS.

Of course the UPS may fail because of a spike|

As long as only the UPS fails.

--
404 error - signature not found.

replying to PeterC , westom wrote:
giraffenos.pam wrote:
I wonder if cattle are as susceptible as horses. Quite recently there was
a
case of a racehorse killed by a mains leak underground.


In one venue, milk production was serous down. Eventually, the problem
was traced to bad grounding in the barn. Currents through aarth, that a
human with shoes would not feel, was so harming clows as to cause (if I
remember) a 20% reduction in milk.

Had humans been walking bare foot, I suspect they too may have felt it.


--

"Uncle Peter" wrote in message
news
On Fri, 28 Feb 2014 10:13:49 -0000, harryagain
wrote:


"Uncle Peter" wrote in message
news
On Tue, 25 Feb 2014 17:14:55 -0000, wrote:

On Monday, February 24, 2014 6:59:34 PM UTC, Uncle Peter wrote:


Ok, I'll assume I've protected the computers well enough then.

The designer & manufacturer of the PC PSU has done that.

Then I guess the 4 quid surge protector is protecting several 40 quid
PSUs.

I've got a spike arrestor on the phoneline too.

Overhead phone services already have those built in.

Youre buying into marketing bs and wasting your time.

Then why did my dad's network card burn out when he got lightning
through
his phone line, through the router, and into the ethernet port?

No little bit of electronic bollix will resist a nearby lighning strike.

It must have been a very small part of the strike, as only the network
card died. Now if the network card can save the motherboard, why can't a
surge protector?

You get a nearby strike and everthing is blown to bits.
I had one where the phone line was reduced to a black mark on the wall. the
local pole transformer was buggered . Incoming mains cable had the
insulation melted.
Fortunately I saw the storm approaching and turned the mains off and
unplugged phones.
I still have pix somewhere of it approaching, I'll see if I can find them.

On Sun, 02 Mar 2014 16:55:27 -0000, harryagain wrote:


"Uncle Peter" wrote in message
news
On Fri, 28 Feb 2014 10:13:49 -0000, harryagain
wrote:


"Uncle Peter" wrote in message
news On Tue, 25 Feb 2014 17:14:55 -0000, wrote:

On Monday, February 24, 2014 6:59:34 PM UTC, Uncle Peter wrote:




The designer & manufacturer of the PC PSU has done that.

Then I guess the 4 quid surge protector is protecting several 40 quid
PSUs.



Overhead phone services already have those built in.

Youre buying into marketing bs and wasting your time.

Then why did my dad's network card burn out when he got lightning
through
his phone line, through the router, and into the ethernet port?

No little bit of electronic bollix will resist a nearby lighning strike.

It must have been a very small part of the strike, as only the network
card died. Now if the network card can save the motherboard, why can't a
surge protector?

You get a nearby strike and everthing is blown to bits.
I had one where the phone line was reduced to a black mark on the wall. the
local pole transformer was buggered . Incoming mains cable had the
insulation melted.
Fortunately I saw the storm approaching and turned the mains off and
unplugged phones.
I still have pix somewhere of it approaching, I'll see if I can find them.

There is a point on the edge of the strike where there is very little damage done. A surge protector could remove that.

I've never unplugged anything when a storm approaches, as the chances of it affecting me and not the other several thousand nearby houses is very remote In fact during the last storm, I continued digging my pond (using a metal spade aswell). Perhaps if I was the only house on top of a hill I'd unplug things, but then I'd get myself some bloody big lightning rods anyway.

--
I called a company and asked to speak to Bob. The person
who answered said, "Bob is on vacation. Would you like to
hold?"

On 27/02/2014 22:57, Uncle Peter wrote:
Can we have a vote on this, or even better a link to the correct answer?

http://www.physicsclassroom.com/class/estatics/Lesson-4/Lightning

Apparently Ben Franklin had it wrong.

Andy

On 01/03/2014 09:48, PeterC wrote:
I wonder if cattle are as susceptible as horses. Quite recently there was a
case of a racehorse killed by a mains leak underground. That would have been
a much lower voltage gradient than a lightning strike, but apparently horses
are far more sensitive to this than are human beings.


Probably they are.

The front and rear hooves of a horse tend to be further apart than a
human's feet. Just to add to it we tend to wear non-conductive shoes,
and put metal ones on the horse.

Andy

On Mon, 03 Mar 2014 21:48:14 -0000, Vir Campestris wrote:

On 27/02/2014 22:57, Uncle Peter wrote:
Can we have a vote on this, or even better a link to the correct answer?

http://www.physicsclassroom.com/class/estatics/Lesson-4/Lightning

Apparently Ben Franklin had it wrong.

I see. Very helpful article.

--
Flanders and Swann on MOT tests:
Our car is getting a bit old, it'll have to be tested soon.
You know they started these tests for 10-year-old cars, they brought it down to six, now five, they'll bring it down to three.
There's even been some talk of having them tested before they leave the factories."

replying to Vir Campestris , westom wrote:
vir.campestris wrote:
The front and rear hooves of a horse tend to be further apart than a
human's feet. Just to add to it we tend to wear non-conductive shoes,
and put metal ones on the horse.


One significant principle applies here. Best protection is to be a priest
having your best golf game. We all saw proof in Caddy Shack. Then
lightning only highlights the event.



--