Surge Protector

**Feel free to list all the known examples of where a standard, off the shelf surge protector has protected equipment. If you want snake oil products (over-priced surge protectors) then you'll need to shop elsewhere.

Learn about 'top-posting' and try to refrain from doing so. It is poor netiquette. Let Google be your friend.

--
Trevor Wilson
www.rageaudio.com.au

On Thu, 5 Jul 2007 08:12:50 +1000, "Tim" put finger to keyboard and composed:

I think the term "surge" is a misnomer in this case. "Surge protectors" (aka metal oxide varistors) will soak up spikes, but not sustained overvoltages, which is how I perceive the term.

While I have no faith in these devices, I do agree that it may be more economical to purchase a Belkin surgeboard (ie, a lifetime insurance policy bundled with a power board) than to upgrade an existing household contents policy, especially when amortised over several years.

- Franc Zabkar

--
Please remove one 'i' from my address when replying by email.

I owe you an apology dmm! You were in error but I could have corrected it more politely. I fell into the usual trap of ng posters in demolishing a point with a steam roller instead of gently righting the wrong. Please accept my apology.

On the point I corrected, fusion (in Australia and UK anyway) is defined as I described it (burning out of the windings of an electric motor) and is not the same as lighting damage. Most policies cover lightning damage (some require visible evidence, which IMO is silly, because with masonry there is often no visible sign). Most also cover fusion which is usually invoked in the case of a fridge compressor tripping due to a power event and then restarting (or trying to) under load. In another thread (can't remember which one now) the poster spoke of extending the normal household cover. In most cases it will not need extending. Lightning is a traditional cover usually offered because back in times gone by it was perceived as a particularly frightening event and yet the individual (or catastrophe, for that matter) risk was in fact statistically very low. That was before the days of solid state electronics, or course. Them there slowing bottles were very transient resistant owing to their thermal inertia.

...and one more thing, in view of the thread topic. The notorious "power surge" (not lighting) often claimed by "repairers" who are just computer salesmen, when there is not the slightest reason to suspect it and when random breakdown is probably the cause of loss, *is* excluded from many household policies precisely because it has been abused by the greedy and/or ignorant so much in the past.

We have a "protector" fitted to the 60 telly " with a close ground strike recently it tripped and I assume helped save things as the same boards also serves the sounc system and I was delighted to see the survival even though the rooms incadecant was blown , I expect the induction from a strike only 4 metres away was severe ? ( it was LOUD)

Apology accepted. I should probably point out too that I'd had about 3 glasses of red wine when I wrote my reply. I shouldn't have mentioned fusion, but lightning damage as pointed out instead. :)

Incandescent bulbs will not be destroyed by lightning strikes. However a massively higher energy source can cause that problem. Lightning may construct electrically conductive paths where none must exist. That path constructed by same process that starts a fluorescent lamp. That surge finished in microseconds. But the plasma path remains.

For example, lightning formed a circuit from utility transformer primary to secondary. Now AC utility 13,000 or 33,000 volt primary is connected directly into your building. That high voltage applies high energy. What might explode? Well which items completed that electrical path? Not necessarily everything.

Demonstrated is why utility earth ground is critical to surge protection. Surges that may overwhelm protection inside all electronics should not be permitted inside the building. Then electronics internal protector circuits are not overwhelmed.

How might a ground strike be a direct lightning strike to telephone equipment? Yes, I said direct strike. Strikes to earth or a nearby tree can also be direct strikes to a human, cow, or building that does not have effective protection. An application note from Polyphaser discusses a failure and what provides protection:

Polyphaser app notes are considered industry benchmarks for understanding the principles:

Did surge enter on earth ground? Then building's surge protection 'system' is defective. Destructive surges enter via ground when an earthing system - what provided protection - is improperly installed. Begin with some of those Polyphaser app notes.

Every electronic device - powered on or off - in home or business - is connected to the equivalent of a radio antenna system. Principles pioneered by Franklin in 1752 on churches and by early 20th Century Ham radio operators are also installed by Telstra so that their switching computer (connected to overhead wires all over town) is not destroyed (for four days due to surge damage). Direct lightning strikes (via overhead or ground strikes) without damage are that typical.

Appreciate why each telephone switching center can suffer hundreds of surges during each thunderstorm - and no damage. First they earth each surge before it can enter the building. Then protection already inside electronics is not overwhelmed.

A tree stopped existing

BTW, ISBN 0-442-01338-8

transformer go

There is absolutely no way that a normal surge protector can protect against such things as a transformer going "arse-up". By this I assume you mean that a higher than normal voltage will be connected towards your premises.

One day several years back I was sitting in the family room about 20 feet away from my old Panasonic Genius microwave oven, which has a small printed board in it which is fitted with the usual surge protection components as found in your everyday anti-surge powerboard. Suddenly I heard this enormous bang and smoke issued forth from the oven.

Upon investigation I discovered the anti-surge varistors had been blown to smithereens and some copper track acting as a fuse had vaporised from the board. I asked the power authority what had caused it and they informed me a tree-lopper had managed to bring a high voltage power line into contact with the normal domestic power lines feeding my area. This produced a similar situation to that of a transformer going "arse-up".

Antisurge power boards will protect only from relatively minor over voltage situations where low currents are a by-product. Anything which is capable of producing high current along with over voltage sufficient to activate the anti-surge devices will simply overwhelm them and blow them to the shit-house. In my case the real protection was offered by the copper track on the pcb which acted as a fuse, although I suppose the varistors may have provided a microsecond of delay before they vaporised.

On Tue, 10 Jul 2007 18:34:01 +1000, a t e c 7 7 put finger to keyboard and composed:

Maybe I'm being unfair.

For example, Belkin's 4-way Surgeboard (the cheapest) boasts the following specs:

Part # F9A402au2M Protection: Level 1 Joules: 714J Maximum Spike Current: 19,500A

Assuming that a 100W incandescent lamp experiences a cold current of

10 times its operating current for 2 mains cycles, then its energy dissipation would be only 100W x 10 x 20ms x 2 = 40 Joules.

Comparing the two figures (714J vs 40J), is it any wonder that your lamp failed while your MOV survived?

- Franc Zabkar

--
Please remove one 'i' from my address when replying by email.

Yes, it's a matter of degree. But a good surge board, properly earthed, is certainly better that nothing.

Your post is based in some assumptions. For example, a lamp filament absorbs nearer to zero energy when cold. Bulbs fail after filament gets too hot - vaporizes. Typical surges are microseconds. Filament never gets hot enough fast enough to increase resistance, then vaporize.

For example, a 'whole house' protector rated for 50,000 amps will have wires how large? 2 or 2.5 mm diameter copper. A wire rated for

20 amps constant current is also sufficient to shunt 50,000 amps surge current because that surge is not constant; typically in microseconds. Same reason why short transients surges would dissipate so little energy in a light bulb.

To have sufficient energy to blow a bulb, that current must conduct longer. Source of higher energy and source of current long enough may be utility supplied electricity.

Confused is how light bulbs dissipate energy verses what joules measure for an MOV. Same units measure different parameters.

Joules for MOVs is a measure of how conductive the MOV may be and a ballpark measurement of its life expectancy (size, pulse width, and number of transients). Joules for MOVs is equivalent to measuring gauge of a wire from Ben Franklin lightning rod to earth. If that wire is too thin, then it will vaporize. If MOV has too few joules, then it will degrade. MOV vaporizes only when current massively exceeds what manufacturer intended - well beyond Maximum Permissible parameters.

More joules in an MOV mean MOV absorbs even less energy. More joules for a light bulb means a bulb dissipates more energy. For a constant current, higher joules in an MOV means more conductive; high joules for a light bulb means less conductive.

Conductivity of a wire is measured in amperes. Conductivity of MOVs is measured in joules. The difference between wire and MOV: wire does not degrade with use. MOVs degrade with use. Wires are for continuous current. MOVs are for rare and short current transients that are typically measured in microseconds. Whereas necessary wire size is measured by wire gauge; MOV size is measured by joules and lamp energy dissipation is measured in joules. Joules for a lamp and joules for an MOV are measuring two different parameters.

What happens when an MOV is better - more joules? Then it absorbs even less energy. MOV function is not to absorb energy. It's function is to shunt (connect, divert, clamp, bond) that electricity elsewhere.