Inline Electric Timer Switch

Respect for the designers of those mountaintop radio relays that get hit by lightning all the time and keep working nevertheless.

Jeroen Belleman

Indeed! I used to live within sight of such a tall mast for atmospheric research in Tsukuba. One day it took a direct hit from a major summer thunderstorm while I was watching. It was just like the firing of the Death Star in Starwars with three bolts from clouds above it joining to one and crashing down onto the top. It was still OK afterwards.

Knocked out for just a couple of seconds but otherwise OK.

I narrowly missed seeing ball lightning once - it had the temerity to appear in a university physics department and attacked the photocopier.

Shareable direct link to short article in Nature "Ball of Fire?":

Sorry, I'm not familiar with lightning rod "systems". I do know that lightning rods won't do diddly in this case because they reduce damage to structures from a direct lightning strike, while the typical damage to electronics is from the magnetic field of a strike inducing very large currents in exterior conductors connected to equipment. Are you referring to something to prevent the surge from an external line from getting into the house? They exist, but are very, very expensive. They also don't protect equipment inside the house from a very close lightning strike (such as to the lightning rod) from inducing currents directly in the house.

There are no guarantees in life, or even in death, except that it will happen someday. There's no guarantees at all for birth, most of which never happen.

The $10 surge protectors come with warranties, including coverage of the connected equipment. Need I say more?

Any lightning rod installation, except a barn, will be a "system". In the US the relevant standard is NFPA 780. The system will include a service panel surge suppressor (the IEEE guide says the minimum rating is 40kA). Also includes features like metal within 6 ft. of rod wiring and down conductors may need to be bonded to the conductors. That is because of the high voltage drop at earthing electrodes and in the inductance of the conductors may result in voltages that will flash across 6 ft.

Most damaging after a direct strike is surges coming in on power and signal wires.

The NIST surge expert investigated how much energy can enter a residence from a near strike. The strike was 200kA to the distribution wire at the top of a utility pole adjacent to a house with typical urban overhead distribution. This is a very near strike. And only 5% of strikes are stronger. For practical purposes this is a worst case. The current was

A near strike can induce high voltages between power and signal wires with the loop formed by the wires acting as a loop antenna. It is a case where service entrance suppressors are not complete protection. But plug-in suppressors, with all wires going through the suppressor, provide protection.

I have never seen a suppressor with warranty for $10.

UL listed plug-in suppressors are reliable (and probably not $10 without a warranty).

Surge protection is not rocket science. Businesses, for instance in Florida, do not shut down for thunderstorms. Highly unlikely residents of Florida haven't figured out how to protect their equipment. Read the IEEE guide

Is not what I have read anywhere.

And not true of suppressors with a UL listing. They are tested as plug-strips. And have at least a specified minimum (also tested) surge rating. And much higher ratings are readily available. And, as explained yesterday, the amount of energy that can make it to a suppressor is surprisingly small.

As I wrote yesterday, a UL listed suppressor is likely to not work as a plug strip if the MOVs fail (IEEE guide pg. 38).

The two suppressors I use are from reputable companies, with high ratings, protected equipment warranties and ports for relevant signal wires. I do not have to worry about whether they will fail.

The building I was in had proper external lightning protection but it didn't make that much difference. Afterwards the conductor was the funny colour that copper goes after being at red heat but the strike still managed to enter the building and vapourise (parts of) the internal phone wiring.

I suspect it was ground currents and magnetic coupling loops of cable between terminals and mains wiring that took out the line drivers. Whatever it was the expensive surge protection kit saved itself by letting the more expensive IO driver boards in the terminal concentrator get fried.

UK has spark gaps on the local mains down transformers so that anything much over 150kV on a nominally 33kV line will arc over on the HT side. The arc looks like a dead short and takes out the breakers.

Nothing can help you if lightning strikes an overhead local mains line the injection of current has to go somewhere and fast.

The thing about the suppressor protection is that it needs to be connected to a very good earth with a chunky conductor and that condition isn't always met. Particularly in summer after a long dry spell.

That's the point. It's like the scene in Tommy Boy, where Tommy is trying to sell his line of brake pads to the retailer who wants to see a guarantee on the box as a sign of quality. Tommy says he can take a crap in the box and put a guarantee on the side. The guarantees are as much BS as the surge suppression on the cheap units. I'm sure they will stand behind their product if you can meet every single part of the requirements. How are you going to do that?

They took a crap in the box and slapped a guarantee on it.

There is no 100% protection. They protect against some level of surge, period. More than that surge and your equipment goes "poof". You are left with a worthless warranty as they don't warrant your equipment will not be damaged by surges over their threshold.

Exactly! How may reimbursements are they going to afford selling $15 outlet strips with a $10k warranty? None! They are never going to pay out because they will find some reason you don't qualify. The warranty on the box does give you a warm, fuzzy feeling inside though, doesn't it? So I guess it *is* the same, eh?

Not having seen how the building was protected....

You can get over 100,000A in a strike, but the duration is microseconds. Hard to imagine in the US, with at least 2 large gauge downconductors to earthing systems the wires would get hot enough to discolor.

Sound like fun to watch. But lightning arresters on the primary protect transformers. They don't provide much protection to buildings.

"Nothing can help you"? I just explained what can help you. A recognized expert in a published paper found that a 200,000A strike to the primary wire on a utility pole adjacent to a building with typical overhead urban distribution results in 10kA surges on the power service wires to the building. Service panel suppressors, with far higher ratings, limit the voltage from the service wires to the service "ground". The "ground" in the US is connected to earthing electrode(s), which is where most of the energy to the building goes.

Plug-in suppressors do not protect primarily by earthing a surge. They can't - the impedance of the wires is too high. The ground potential at the suppressor can rise thousands of volts above the ground potential at the service entrance "ground", described in the IEEE guide pg 30-35. The guide explains, starting pg 35, that plug-in suppressors work primarily by limiting the voltage on all wires, power and signal, to the ground at the suppressor. The voltage between wires going to the protected equipment is safe for the protected equipment (as I wrote above).

The guide, on pg 28, looks at the ground potential rise of the "ground" at the service (specifically signal, but it the same for power). The building "ground" can rise, in this example 250,000V, above earth potential distant from the building (that would cause arcing across the earth from the ground rod away). Much of the protection, again, is that service panel suppressors and signal entry protectors limit the voltage to the ground at the panel. The voltage between wires inside the building is generally safe for the connected equipment (as I wrote above). (One exception is pg 33, another - induced pick up from a near strike to wire loop in a previous post.)

Protection likely does not primarily involve earthing the surge.

Read the IEEE surge guide - written for technical people

I haven't looked at Belkin for a long time.

I looked at one suppressor (at Belkin site) with the same 3 year language. It also said "and a lifetime $75,000 Connected Equipment Warranty." IMHO if sued (could be small claims court here) Belkin would have trouble denying coverage. One problem with a surge warranty is people think any damage with an unknown cause, like to a microwave, is from a surge.

I couldn't find warranties at Belkin, or user manuals. UL wording I saw did not clearly say suppressors were UL LISTED - tested BY UL to UL1449. Belkin seems to have branched out into other products.

From a previous post, from published research, with up to 10kA surge on power wires, and no suppressor a the service, the maximum energy absorbed by a MOV on a branch circuit was 35J. In 13 of 15 cases it was

Companies in high lightning areas of Florida do not move to Nevada because of thunderstorm damage. Principles of protection are well understood. Five engineers experienced in surge protection wrote the IEEE surge guide, which details the base principles. The guide says plug-in suppressors are effective and says how to use them. Also lots of information on other protection elements.

Read the IEEE surge guide

Glad somebody brought up ferroresonant power supplies.

Simple, reliable, but terribly expensive and inefficient. I need to move a

Isolation transformers work pretty good too, but don't help during a brown-out or with regulation issues if that's an key issue.

Yeah; they claim 85% efficient, BUT that means the 400VA unit wasted 60W even when lightly loaded.

You'll want a cart; that's gonna be circa 100 pounds of steel and copper.

Yeah. Mass does good that way.

That number is only at full load. Since they run at saturation in one leg at all times, the amount of heat they generate is impressive, even at no usable load. I've never tossed a scope on the resonant section with the high voltage capacitors, but there has to be square waves in there somewhere, yet the output is a perfect sine wave. Fascinating stuff, up there with magnetic amplifiers and saturable chokes for controlling lighting or heating loads.

Never thought of it that way, but they sure store some energy in the magnetics, sort of like synchronous AC flyweel.

lol, I'd love to see the details of a $25k damage claim against a $10 power strip, with photo of the payout check.

There's a reason they cost $10 and real surge/transient protection costs way more.

In the continental US, you can get surge arrestors to install at a home service entrance, even at home depot now. Stuff like this used to be hard to get, even at a supply house, with a special order. If you have electronics damaged, it's a good $100 buy. Strings of power strips, even without surges are dangerous anyways. I've seen dozens of them with burned or melted receptables, even from moderate loads.

tripp-lite mostly produces garbage these days, but the Isobar grey power strip devices are still OK. I have never seen on fail past the neon light on the power switch dying after many years. They're about the safest bet for permanent use for a temporary power strip.