Are mains surge protectors needed in the UK?

[Bernard Peek]

Referred to by the Shermans as "knob and tube" wiring. Though I thought
the wires were insulated.

I had a newsgroup conversation with someone who found bare wires,
apparently still permitted. It wouldn't surprise me to find that most
electricians installed insulated cables, just because something is
permitted it doesn't mean you have to do it.

Although I've seen a house previously owned by a plumber who had
installed the hot-water cylinder in front of the rising-main stopcock
and one previously owned by an electrician with a hard-wired UPS system
that blew up my PC power-supplies.

 

[Jonathan Buzzard]

Furthermore, if a component vaporizes, then the surge
protector was defective by design - grossly undersized. MOV
manufacturers even provide charts on life expectancy. The
number and size of transients determined when the MOV has
degraded. Not vaporized. There is no part on the chart for
vaporization because that is a failure beyond what MOVs are
designed for. Surge protectors shunt every surge without
human knowledge. Eventually, MOVs degrade - and do not
vaporize.

No MOV in existence can handle a direct lightning strike, for that
you need a GDT. The highest rated MOV I have seen was only good
for a 1500A spike and that was over ten times the price of a GDT
that could handle a 20,000A spike. Which is why all good surge
protectors have both. A fast acting MOV to deflect the leading
edge of the spike and a GDT to take over and deflect the bulk
of the surge to ground.

JAB.

 

[Jonathan Buzzard]

That's because a balance has to be struck between cost and
effectiveness. To quote your own words earlier, thunderstorms in the UK
are far less frequent than in the US.

Every BT line is terminated in a NTE5 master socket. This has a spark
gap arrestor device which deals with the majority of surges.

Technically a GDT, and unfortunately they are almost never connected to
earth. This is why lots of telephone equipment was damaged. Not because it
was being protected by inadequate plug in surge protectors, but because it
was not being protected by anything. In fact new NTE5's don't have a
a GDT and an earth terminal anymore.

JAB.

 

[Jonathan Buzzard]

Protection from the most lightning prone locations is
routine and well understood. Others who have been in Mike's
Canary Island situation say "no problem":
http://www.telebyteusa.com/primer/ch6.htm
See Section 6.4: WHEN SHOULD YOU WORRY ABOUT LIGHTNING?

Conceptually, lightning protection devices are switches to
ground. Once a threatening surge is detected, a lightning
protection device grounds the incoming signal connection
point of the equipment being protected. Thus, redirecting
the threatening surge on a path-of-least resistance
(impedance) to ground where it is absorbed.
Any lightning protection device must be composed of two
"subsystems," a switch which is essentially some type of
switching circuitry and a good ground connection-to allow
dissipation of the surge energy.

It defines both the single point earth ground and a
connection to that ground - surge protectors or hardwire.
Curious. They did exactly what I have demonstrated.

http://www.harvardrepeater.org/news/lightning.html

Well I assert, from personal and broadcast experience
spanning 30 years, that you can design a system that
will handle *direct lightning strikes* on a routine
basis. It takes some planning and careful layout, but
it's not hard, nor is it overly expensive. At WXIA-TV,
my other job, we take direct lightning strikes nearly
every time there's a thunderstorm. Our downtime from
such strikes is almost non-existant. The last time we
went down from a strike, it was due to a strike on the
power company's lines knocking *them* out, ...
Since my disasterous strike, I've been campaigning
vigorously to educate amateurs that you *can* avoid
damage from direct strikes. The belief that there's
no protection from direct strike damage is *myth*. ...
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. That's most generally a low *inductance* path
rather than just a low ohm DC path.
http://lists.contesting.com/_towertalk/1997-April/004413.html
The basic scenario is to install a Single Point Ground
System that is installed at the building entry. It shunts
everything to ground before it goes in the building. If
you can keep it outside, then you don't really have to do
much inside. IMO disconnecting the cables is more
psychological than preventive.
http://scott-inc.com/html/ufer.htm
The land owner warned us that this tower was frequently
struck, and equipment had been repeatedly damaged despite
increased precautions. Indeed, during July construction,
the masonry workers left the site after "a bolt sent
fireballs rolling down the [existing] tower". With a
sensitive CMOS controlled transmitter and a talking remote
control selected for the installation, I knew that any
transient overvoltage protection devices I would specify
would need a very conductive path to ground to divert
strike energy away from the equipment. ...
In sixteen months, the site has maintained twenty-four hour
per day operation with ZERO downtime except due to AC power
failure. With equipment so susceptible to transients, this
kind of performance is unusual in this region, especially
on this hill.

Mike would have us believe that an inferior US electrical
distribution system creates surge damage in the US. He
forgets that the UK has almost no lightning compared to the US
and still suffered significant damage. Especially true was
the amount of modem damage in the UK during an unusual
thunderstorm on 4 July 2004. Trivial storm by American
standards. Numerous UK modems were unnecessarily damaged due
to no properly earthed protectors.

Plug-in protectors in the US are three wire. Makes no
difference. A distance of much more than 3 meters (10 feet)
to earth ground means the plug-in protector is not earthed -
as demonstrated by previously posted numbers that remain
unchallenged. Excessive wire impedance from wall receptacle
to earth ground explains why plug-in protectors are so
ineffective, why the manufacturer does not even claim to
protect from the destructive type of surge, and why Mike
Tomlinson assumes a certain amount of surge damage is
acceptable. To maintain a myth about plug-in protection, he
must ignore the numbers. How then does he deal with testimony
from industry professionals who have learned concepts of
effective protection and don't suffer damage.

How does he
explain 25 direct strikes per year to electronics atop the
Empire State Building without damage? A surge protector is
only as effective as its earth ground.

You tell me w_tom, because according to your previous statements, you can
only get effective earthing if you have a ground earth that is less than
three metres in length. Last time I checked the top of the Empire States
Building was considerably more than three metres from the ground.
Therefore going by what you say there is no way on earth to get effective
surge protection.

As effective surge protection can be achieved on top of the ESB then you
are clearly talking rubbish. However we already knew this.

JAB.

 

[Jonathan Buzzard]

Well, you posted this link yourself, showing typical American
installations: http://www.tvtower.com/fpl.html

Power distribution to domestic properties in the UK is almost all
underground, fed from local substations. Not overhead lines and pole-
mounted transformers with dodgy connections to earth and broken surge
protectors/lightning arrestors.

Thank you for proving my point.

Goodness me, I knew the power distribution systems in the USA where bad,
but not this bad. If it where like this in the UK, the electric companies
would be in deep trouble.

As you say the UK power distribution is orders of magnitude better than
this. Also as the damage from lightning strikes comes when the lightning
surge breaks down the insulation in the step down transformers connecting
the nation grid directly to your house, and rather than lots of dodgy pole
mounted transformers for every few houses we have substations serving
hundreds of houses that have impressive grounding and surge protection,
we don't have problems.

JAB.

 

[VWWall]

If it's not wired according to code I suppose they could. But code has
separate runs back to the entry panel.

Since you don't understand that both sides of a 230/115 V branch circuit
are on the same phase, you may not understand how such circuits are
wired. They are completely in accord with any current electrical codes.
A "multiwire branch circuit" is defined in the codes. It can supply two
115V circuits with two "hot" wires and a common neutral wire. Any U.S.
home with 230 V entry service has at least one.

For a good summary on present electric wiring see:

http://www.faqs.org/faqs/electrical-wiring/part1/

It's fairly long but gives a lot of good information in simple terms.
It has information on grounding (earthing) and even a note on K&T wiring.

Toward the end there are some notes on surge suppressors.

Read your local electrical code!

Virg Wall

 

[Jonathan Buzzard]

On Fri, 09 Jul 2004 18:29:54 -0400, w_tom wrote:

[SNIP]

I have posted as professional papers and technical
application notes are posted. New information up front.
Background information and references at the end. I am not so
intolerant as to bring up the silly top post / bottom post
nonsense that only the emotional would do.

Yet w_tom you have repeatedly denied that events that really did take
place could have taken place. If you tell me that there is no way the
shorted out kettle flex caused the HD15 input to the 21" monitor to fail
then anything else you say is going to be seen as the ramblings of an
idiot. The monitor was working fine, the kettle flex shorted tripping the
RCD and MCD, causing everything to turn off. On reconnecting the power the
monitor was not working. Yet you persistently deny that it happened or
that it is even possible.

You reputation would be enhanced if you could even challenge
the post demonstrating wire impedance. You cannot. So
instead you again start this silly top post / bottom post
nonsense. Do you like it when someone attacks you as you
attack others - by questioning your character?

It is not nonsense.

JAB.

 

[Jonathan Buzzard]

Except that responsible 'whole house' protector manufacturers recommend
'plug in' protectors for sensitive equipment in addition to their protector.

In fact the British Standard has whole sections on this.

Given that 99% of all damage done by surges in the U.K. is down the
telephone wire and plug in surge protectors will provide
adequate protection in this instance, whole house protection is an
unnecessary expense to retro fit to a house. Something that w_tom fails to
understand, but fitting whole house protection to most U.K. properties
would cost in excess of 500GBP and more likely to be in the region of
1000GBP.

JAB.

 

[Jonathan Buzzard]

On Sat, 10 Jul 2004 02:32:52 -0500, David Maynard wrote:
[SNIP]

Won't be 'the same money'.

I think we can figure on whole house protection starting at a minimum of
500GBP fitted and a plug in surge protector at under 20GBP.

JAB.

 

[Jonathan Buzzard]

OTOH I've heard several reports of hardware losses in the US caused by
brownouts and spikes. The power distribution systems aren't as well
protected as in the UK, possibly because of the greater average distance
from substation to home, and poor earthing policies.

The problem in the USA is that they don't have substations. Every house
(or couple of houses) has a transformer up a pole that drops from around
5000~7000V to 110V. Most are poorly earthed and surge protected which is
where the problem lies.

In the UK we have substations providing 240V directly to hundreds of
houses. The transformers in these are very expensive bits of equipment and
are therefore well protected from surges and have comprehensive earth
grounding. Hence you rarely get damage from power surges in the U.K. and
when you do it is likely to be from some faulty equipment or wiring inside
the house.


JAB.

 

[Mike Tomlinson]

My sister in \Cornwall (nr Helston) had a brownout) voltages of several
hundred volts over 230V apparently

um, a brownout is when the voltage falls below the permitted minimum.

Surge protectors would have almost certainly saved her the hassle..

I think she needed a UPS, not a surge protector

 

[Mike Tomlinson]

This 'light' feature is so old in America that it was even
on surge protectors tested in PC Magazine in the 1980s. So
now you insult the US for importing Chinese 'junk'. Where in
that insult is a technical fact? How does that light work?

I've posted this before in another thread, but given that you have the
attention span of a mentally retarded goldfish, am not surprised that
you've already forgotten.

I assume you have basic understanding of electronics (though I'm not
counting on it, given your performance to date.) Here's the circuit
diagram and description of the plug-in surge protector I use:
http://jasper.org.uk/w_tom_is_a_wanker/cct.jpg

Quote:
"The protection VDRs in this circuit have a thermal disconnect which
breaks link LK1 when either VDR has reached the end of its life. Link
LK1 under normal operation is a short circuit but when opened due to the
thermal disconnect device, allows current to flow via the lamp LP1 and
the resistors R1 and R2, thus illuminating LP1."

See! This surge protector fails in a controlled manner and illuminates
a lamp, instead of exploding messily like the examples you cited in:
http://www.zerosurge.com/HTML/movs.html

Tell me, do you get circuit diagrams with /your/ protective devices?

So now Mike. Please enlighten us. How does that "warning
lamp to indicate when the protective devices have degraded"
work?

See above. If you can understand it, that is.

Feel free to top post or bottom post.

I'll do neither, thanks. I'll do it properly, quoting context and
posting in-line and snipping all unnecessary quoting. Something you'd
do well to emulate if you want to be taken seriously.

You seem to have so many personal insults that I think I
will keep the so many you have given me.

Feel free; you deserve them. Here's another: You're a gormless ****wit.

After all, you are
going to show us how smart you are. You are going to show us
how that light reports that MOVs have degraded.

Quite right. I've done that above. Thanks.

 

[half_pint]

"Johannes H Andersen" <[email protected]>
wrote in message

you.

I am sorry you're wrong flap_paint. Semi conductor devices are blown by
excess Voltage. A fuse only senses the current.

And current=voltage/resiatance. Ohm's law. more voltage more current.

Rubbish half_faint!

Nonsense Joanna.

As said before, voltages also kills semiconductor devices. Why do you
think there are such things as electrostatic bags?

To protect semiconductors from static electricity as opposed to
mains electricity.

You will notice semiconductors are not shipped connected to
a surge protector. (unless you are the ultra cautious type).

 

[half_pint]

Another GUESS, eh?

Did you forget to consider that all computer power supplies have
a fuse, yet they can (are) still damaged? Suppose you 'd now
claim the engineers designing them don't know as well as you how
to select a fuse?

Probably. Its as good as a surge protector anyway, and GUESS what you
find in many (probably all?) surge protectors? You've guess it, a
30p fuse!!! (60c). [Prices correct at time of going to press].

A fuse is a failsafe for damaged or otherwise compromised
equipment, not a preventative measure.

Surge protectors are no better. they won't protect you from a
lightening strike anyway.
Also your power supply will protect you from minor power
surges.

 

[half_pint]

you.

If the current is enough to melt a wire (the fuse) do you really think
it that same current can't have done any damage to your equipment?
Your electronics will be dead before the fuse is even warm.

No the fuse will have melted before your electronics even begin to
warm up, that is how they are designed.

A fuse might stop your house burning down after an electrical fault,
but it won't protect your PC from a surge.

Yes it will, it is as good or better then a SP which surprise probably
contains a fuse. However this fuse is probably "protecting"
4 different plugs (and hence rated 13 amps or more so not
much use). You can fine tune the fuse you use to protect your computer.

I would imagine the fuse in my computer is one amp or less. Sure to
blow before may lovely computer is damaged :O)

Tim

No progress made on that front either.

 

[Tim Auton]

Did you forget to consider that all computer power supplies have
a fuse, yet they can (are) still damaged? Suppose you 'd now
claim the engineers designing them don't know as well as you how
to select a fuse?

Probably. Its as good as a surge protector anyway, and GUESS what you
find in many (probably all?) surge protectors? You've guess it, a
30p fuse!!! (60c). [Prices correct at time of going to press].

You're wrong. Surge protectors contain MOVs between various lines.
MOVs don't conduct at normal operating voltages, but do conduct with
higher voltages. This is how they dump surges to the ground/neutral
lines.

Fuses are, in the timescales we're dealing with, simply too slow to
react.


Tim

 

[half_pint]

For a robust motor, or a heating element, or other devices of that type (if
it's not actually the device itself that's at fault, as in a stalled
motor), yes. Generally because they are simple, robust, electro-mechanical
devices whose 'failure mode', that's being protected, is usually a result
of over heating and they have thermal response times slower than a fuse.
They are also relatively immune from surge remnants left over from the
entry point lightning supressors as their electrical response times are too
slow to be affected, as long as the surge does not exceed the insulation
resistance.

For electronic devices, no.

But electronic devices are not connected directly to the mains they
are connected to a power supply which is *designed* to copy
with large cueernts.

OK if you connect one leg of your 3GHz pentuim to the
mains live connection and the other leg to earth you will probably damage it
but I am not recommending that.

And it's inherent to the nature of electronics.
By the time an electronic device is pulling excessive current whatever is
at fault inside has long since gone to the happy hunting grounds, or else
it would not be pulling excessive current. And there's nothing you can do

about it by 'sizing' the external fuse as the failed device could be a
100mw component inside a 200 watt computer where the normal operating power
fluctuations are hundreds of times larger.

I dount there are many 100mw components in a PS and even if there
were and they did blow they would protect your computer.
However before it did blow it would probably required a
several fold increase in current for a substained period which
would obviously blow the fuse first.

And if you are saying that semi conductor devices are inherently
sensitive to current then obviously we would make fuses out of them.
However semiconductors are make out of silicone which has
an extremly high melting point. (we are basically talking about
sand) indeed silicone has replaced asbestos as a safer heat
resistant material.
http://www.candochefs.com/silbakmat1.html

" Use in up to 900 degrees F! "

Obvioulsy fuses are *designed* to melt quickly
at low temperatures.

Semiconductors materials are probably never damaged
by heat, at least not untill long after the metalic contacts have
vapourised.

And even if you did have a
'constant power consumption' electronic device, for which you could
'tightly' size a fuse, electronic components can, and do, go into
catastrophic failure hundreds of times faster than a fuse can blow.

Surge --> component failure --> excessive current --> fuse blows


That is certainly the myth. It is not, however, reality.

You don't have a huge backlog of expensive surge protectors to shift
by any chance?

 

[Johannes H Andersen]

"Johannes H Andersen" <[email protected]>
wrote in message


And current=voltage/resiatance. Ohm's law. more voltage more current.

To make it simple for you lard_tins:

burn = energy

energi = small voltage drop across fuse * current * time

IT TAKES TIME TO BURN A FUSE!

Semiconductor devices, on the other hand respond, extremely rapidly
to anything knocking their front door, hence we have quick processors.
3 Gigahetz = 0.00000000033 seconds!

In that time the fuse has hardly woken up from sleep, has it?
OK, so PSU and other devices might be a little bit slower, but still
the same idea.

 

[Tim Auton]

And if you are saying that semi conductor devices are inherently
sensitive to current then obviously we would make fuses out of them.
However semiconductors are make out of silicone which has
an extremly high melting point. (we are basically talking about
sand) indeed silicone has replaced asbestos as a safer heat
resistant material.
http://www.candochefs.com/silbakmat1.html

Ha! You don't have to melt silicon to fry a chip.


Tim

 

[Bob Eager]

But electronic devices are not connected directly to the mains they
are connected to a power supply which is *designed* to copy
with large cueernts.

But not *that* large...and they too contain semiconductor devices.

I dount there are many 100mw components in a PS and even if there
were and they did blow they would protect your computer.
However before it did blow it would probably required a
several fold increase in current for a substained period which
would obviously blow the fuse first.

For semiconductor devices, the sustained period is a lot shorter than
for a fuse.

And if you are saying that semi conductor devices are inherently
sensitive to current then obviously we would make fuses out of them.
However semiconductors are make out of silicone which has

No, silicon. Not the same. How many semiconductor-packed breasts do you
know of?

Semiconductors materials are probably never damaged
by heat, at least not untill long after the metalic contacts have
vapourised.

Perhaps not the base material, but semiconductor materials are a bit
more complex than that (hint: look up 'doping').