Clamping voltage on surge protector?



You've got your figures wrong. 2.6 times rated capacity = 33.8A, not 260A could low for 10s before the fuse blows.

Its quota of 240 Joules probably leaves it looking brand spanking new, but with the operating LED off. 5 times that might leave it brown or melted a little, but I doubt it would burst into flames.

I've stated three times before in this thread that I've seen a surge protector get L1-L2 across it. It was deformed, but did not catch fire or emit significant smoke before the 32A circuit breaker tripped.
Also, a loss of neutral would cause 415V? Explain! That is the absolute worst case scenario with completely imbalanced phases.
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On Wednesday, 26 February 2014 21:10:33 UTC, Uncle Peter wrote:
tarts to fail by dropping in resistance. If it is protected by a 13A fuse, then a current of 260A could flow for 10s before the fuse blows. At 240V it will have let through an energy of about 81000 Joules. The Micromark pr otector claims to be able to absorb up to 240Joules. So where do the other 80760 Joules go?

60A could low for 10s before the fuse blows.

Oops! Sorry about that. I mistyped the current, but the result is correct .
13 * 2.6 * 240 * 10 = 81120 Joules

worst case scenario with completely imbalanced phases.

Yes. It is perfectly possible under fault conditions.
John
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How? Neutral is only required to stabilise uneven phases, and is often a thinner conductor.
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On Thursday, 27 February 2014 00:17:24 UTC, Uncle Peter wrote:


Incoming neutral goes open circuit. If one phase happens to be heavily loaded and the other two very lightly loaded then the voltage on those approaches 415V.
Or, of course, the example you already gave of incorrect wiring.
John
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replying to Uncle Peter , westom wrote:

via a stake at the premises or the substation.
Those assumptions about how electricity works are incorrect. Electricity is never same on both ends of a wire. How different. Again, every answer must always include numbers.
To demonstrate. Connect a 200 watt transmitter to a long wire antenna. Touch one part of that antenna to feel no voltage. Touch another part to be shocked by over 100 volts. How does zero volts and 100 volts both exist at different points of the same wire? That is how electricity works.
For same reasons, safety ground wire in a receptacle is not earth ground. Another critically important number exists due to how electricity works. "Less than 10 feet". If a surge does not make a connection low impedance (ie 'no sharp wire bends') to earth, then the connection is compromised.
For effective protection, a surge is connected low impedance (ie 'less than 10 feet') to single point earth ground. That power strip protector (what should be obvious) has no earth ground. And does not even claim to protect from destructive surges. A protector is only as effective as its earth ground.
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westom wrote:

    I have seen 10KV standing waves on 415V lines. The results are very destructive.
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Sounds interesting. What was the source of the 10kV?
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Uncle Peter wrote:

    Reflections on the transmission lines which just happened to have the correct length for the results to be additive. It's a very common effect on Radar transmitter systems, fortunately rare on 50Hz systems. Took a bit of head scratching to realise what the problem was and look for it.
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I guess the wavelength of 50Hz electricity is exceedingly long (I make it about 6000km), so not likely to cause a standing wave. However a SATA3 cable I believe operates at 3GHz, which has a wavelength of 10cm if my calculations are correct. I wonder if they have to consider reflections causing interference?
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Uncle Peter wrote:

    The termination impedance is critical. Early PC 100MHz+ boards found reflections to be a problem and there was a bit of a learning curve.
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Ah, like with the old coax ethernet and SCSI systems.
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I guess the one I've got is only designed to (and it does say things like that on the packet) protect against little surges from motors, arc welders, etc on the same or a nearby circuit. Or perhaps a little spike on the power lines from a fucked up switch over by the electricity board.
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You over-estimate the conductance of protective earthing and under-estimate the strength of the current in a lightning bolt.
It's quite a 'neat trick' to get earth resistance down to a tenth of an ohm (even the pile of 'copper mongery' buried in the foundations of a large telephone exchange may not approach such a laudibly low resistance figure of merit).
The current in a ground seeking lightning bolt can easily be 50,000 amperes or more with rise times measured in nano to micro seconds. If the local exchange building recieves a direct hit by a modest strength lightning bolt of 50,000 amperes, the exchange earth potential will be raised by 5KV with an earthing resistance of just 0.1 ohms (and this ignores the effect of inductance in the earth cable runs to the exchange earth bonding point which will likely raise this by another order of magnitude or so).
Such a strike at (or even just very close to[1]) the exchange will send kilvolt pulses along every telephone line as a 'common mode' surge. This isn't normally a problem for most line powered telephones but can wreak havoc with any equipment that relies upon an external mains connected PSU.
[1] A close ground strike is anything within about a hundred metres. This will raise the local earth potential by several thousand volts varying not only according to the strength of the lightning bolt itself but also according to the nature of topsoil and underlying bedrock.
This also applies to direct/close strikes at the customer end of such galvanically connected lines (telephone and Public Supply Utilites). You can turn the whole house into a faraday cage but the benefit is easily negated by the need to have a galvanic connection to external remote services such as phone lines and mains electricity supply.
It is possible to 'filter' such external sources of destructive surges but the 'filters' tend to require well buried convoluted runs of cabling designed to short circuit any such surges to earth (and, if necessary fail destructively in a final act of sacrifice to protect the connected equipment) along with more conventional (if rather heavy duty) EMC filtering to remove the 'final sting' from the residual voltage spikes that the special sacrificial cable runs let through.
When it comes to lighting strikes, this type of wild and unruly example of electrical discharge is no respector of "Keep Off The Grass" signs (insulation) normally obeyed by mains voltage levels. It will tend to vaguely follow the path of the conductors but quite happily, so to speak, take any shortcuts it can.
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Agreed. Although the surge protector would still help to reduce the potential difference between each of the three wires going into the equipment. Depending where the appliance is situated, I guess the lightning might want to go through it - eg a washing machine sat on the ground floor.
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replying to Uncle Peter , westom wrote:

might want to go through it - eg a washing machine sat on the ground floor.

A protector adjacent to appliances would not even claim to protect from them. A completely different device (that unfortunately shares a same name) is for such anomalies. And would be necessary to protect an expensive power strip and UPS from that anomaly.
People have undersized protectors behind TVs and under desks only because advertising says so. Most also do not know of a fire threat these create due to being undersized and located where fire risk is greatest. Why does advertising forget to discuss this fire hazard and relocating protectors in safer locations? Are they being honest or simply manipulating the naive for higher profits? The so called 'high quality' protectors are little different from $10 ones. They operate similar. And only from anomalies that typically cause no damage.
Monster also sells them. Monster has a long history of identifying scams. Then selling an equivlent product at even higher prices. Because so many know a higher price and more expensive paint means it must be better quality. Those who know without learning numbers are so easily manipulated as to even recommend these ineffective devices.
Voltage spikes between wires are rarely destructive due to how appliances are designed. That transient is easy to avert. Destructive surges seek earth ground. For over 100 years, the solution has always been earthing at the service entrance of every incoming wire.
How often does your telco not provide phone service for four days while they replacen that $multi-million computer? Never? Exactly. Because telcos use this same and proven protection solution - with an even better earth ground. Their CO, connected to wires all over town, suffers about 100 surges per storm ... without damage.
Homeonwers need to worry about one surge maybe every seven years. A number that also says why so many do not even know if their surge protector did anything.
Suppose a nearby strike raises voltage beneath the house by 10,000 volts. No proboem. Everything at 10,000 volts means zero volts across any appliance. This well understood concept is even described by a Faraday cage. Unfortunately those myths about ground resitance and high earth voltage live on when a simple physics concept - Faraday cage - is not understood.
Lightning strikes a church steeple because wood is an electrical conductor. That maybe 20,000 amps through a poor electrical conductor to earth means a high voltage across the church steeple. 20,000 amps times a high voltage means high energy and damaged church steeple.
Franklin mounted a lightning rod. Do lighting rods do protection? Of course not. A lightning rod is effective when connected to earth on a separate wire. 20,000 amps on a conductive wire means near zero voltage. 20,000 amps times near zero voltage is near zero energy. No steeple damage.
Same applies here. Lightning permitted inside a building means a high current to earth via appliances and conductive house materials (ie wood). A high voltage is created. A high current times a high voltage is high energy. Appliances damaged.
For over 100 years, the informed earthed incoming wires directly or via a 'whole house' protector. Do protectors do protection? Of course not. A protector means a near zero voltage when connected low impoedance (ie 'less than 10 feet') to earth on a dedicated earthing electrode. High current times a near zero voltage is near zero energy. Protection already inside every appliance is not overwhelmed. And all appliances are also protected from lesser anomalies. This is the well proven solution used even 100 years ago.
Protection is always about where hundreds of thousands of joules dissipate. Anyone who does not discuss energy and relevant numbers is probably reciting advertising myths and other forms of propaganda. Many denials here are devoid of basic electrical concepts. And half truths promoted by hearsay.
Best solution, without doubt, that costs less money is earthing a 'whole house' protector. Otherwise next best protection is that already inside all appliances. Fewer who did this stuff as engineers would know that. A majority only informed by advertising would not. And forget to include numbers in their recommendations. Forget to answer this - "Where do hundreds of thousands of joules dissipate?"
A protector is only as effective as its earth ground. Numbers are provided to show why. And to show why other 'so called' high quality protectors (better called profit centers) do not even claim that protection.
Of course, soundbytes dispute this. Reality always takes longer.
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replying to westom, westom wrote:

--
I should probably also add something rarely known. Other incoming utility wires
(ie cable TV, telephone) already have this 'whole house' solution. As required
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Someone once told me that lightning rods actually do not conduct lightning, they conduct the charge previous to lightning, discouraging the main bolt from taking that path.
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replying to Uncle Peter , westom wrote:

they conduct the charge previous to lightning, discouraging the main bolt from taking that path.
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On 26/02/2014 23:49, Uncle Peter wrote:

Someone was wrong.
Andy
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He designed computer power supplies.
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