Brain Teaser (Spikes, Ringing, Impedance on your Powerlines)

----------- a)spikes do occur with any switching of an inductive circuit. Capacitances modify this by lowering the frequency of the ringing. b)Adding capacitors will NOT cause your meter to run faster.. It will give somewhat higher voltages at your location and may help you with the spikes- most of which may be due to the motors on your feeder.

You might try a SOLA constant voltage transformer (power conditioner) for your more sensitive equipment

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Unfortunately, your switching power supply analogy does not work.

No, your meter will not run faster.

Use a true double conversion UPS if you want to help with transients. A standbye unit allows everything to pass to the load until it switches to battery.

BTW, what makes you think the utility pulled the fuse? If the fuse blew for a fault, then the fault could be the cause of an overvoltage event. If a fault occurs on one phase of a three-phase (grounded wye) system, the voltage on the faulted phase drops (sags) while the voltage on one (or both) of the unfaulted phases increases (swells). This swell can last for seconds and is much more likely to damage equipment than a switching transient.

Charles Perry P.E.

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Your concept should help, at least I stopped loosing electronics when I installed a surge arrestor at the service and another one at each piece of equipment. I have not had to go to the UPS level thankfully. You might want to check your grounding system. I have found in the last three homes I have had that the "ufer" ground, a bare conductor in the footing test well, some

Hi C, I was trying to be brief... Utility added some new poles and new

12 kv primary wire on my acrage. They pulled the fuse at the source to my street so they wouldn't fry. I was watching tivo at the time, the video passes from the tivo thru the vhs deck onto a modulator where I watch it on ch 66. The 200amp meter box on the pole has 3 bare (#8?) copper wires going to 8 foot ground rods spaced 12 feet apart, plus there is a seperate copper wire that runs 100 feet under 2 feet of dirt, I installed them myself and inspected by the county, 11 years ago. With the electric furnice running (about 30a @ 240vac), there is a 0.5 volt drop across the neutral line from the breaker box in the house to the meter box. I think the power source (utility) has a high internal resistance (impedence).

I can sometimes hear clicks in my stereo speakers (stereo on) when a switch turns off an inductive load. So what size capacitor do I need? Johnstone Supply has Motor Run oil filled Caps 440 vac in sizes from

2.0 mfd to 60 mfd. I don't want to raise my voltage, it is already 124 vac.

So, are you using surge reference equalization hardware? If not, there is your problem. You need to make sure that the voltage between the "grounds" of the various systems is minimized. You can do all you want trying to protect your equipment from the power system, but if you do nothing on the communications side, you will have failures. You need surge protectors that have connections for power, cable, and telephone in the same package.

Where does this 100 foot ground wire connect to your grounding system? Inspection means little as I have seen things passed by inspectors that would keep you awake at night.

A 240V load runs on the two hot conductors, not the neutral, so you would expect no voltage drop. Of course the furnace has a motor that is likely

120V and that is the source of the voltage drop. I am not sure why you gave this information, since it does not provide anything useful to solving your problem.

Why would you make that (likely incorrect) assumption? Also, what do you mean by internal resistance? Their ground impedence is most certainly lower than the resistance of your grounding system since they run a multigrounded system. Think of a massively parallel grounding system. The parallel combination of all of those ground connections makes for a low impedence.

I doubt installing a capacitor will fix this.

Charles Perry P.E.

This I know to be true, if your load is connected immediately to the source, without wires, there will not be any voltage drop or ringing and minimal spikes. I know this cause I helped invent a 2kw switching power supply for the Navy at ITT Gilfillan in 1984. These were then paralleled to combine into 80KW supplies. We were blowing up switching transistors all the time, until I mounted the storage caps and snubbers directly on the transistors, instead of 3 inches away, as had previously been done. Those 3" wires caused huge spikes on the collectors. I did not design the circuits, I was the Senior Tech in R&D Radar Transmitters, responsible for building prototypes from schematics and electro-mechanical packaging. At first, the engineer had me build it his way.....Later I did it my way.... If you have a car battery, 30 miles of wire and a starter for your engine, the voltage drop of that wire will likely prevent the starter from operating under the engine compression. The distance from the load to the source directly effects the internal resistance not only from the wire ohms (in DC) but also the impedance from the ac component , combined. That total resistance contributes to the ringing because the source NOW has some "internal resistance" ( wire length) that can't swamp the ringing. I can't think of a great example, but if you tied two long ropes ten feet off the ground, one tied to a 30 yr old tree and the other a 1.5" metal pole. Then spin each rope with the same intensity as though kids were going to skip rope, the pole would warble and the tree would not. The pole would introduce (or fail to prevent) ringing ( defined as a parasitic unwanted waveform onto the rope) . Whereas the tree would remain steadfast do to it's mass or what I call low internal resistance. It is the point I was eluding to with a calcified cell in the car battery. Multiple ground rods distributed over the utilities network of wires plays no part in internal resistance, cause that can't compensate for the primary hot wire. I'm guessing however, that distributed capacitors over the network of wires would act as small power sources, neutralizing some of the ringing. Those caps would be the ones presently clumped together in one yard, 30 miles from me. I see your point about the 240 v furnace not using the neutral... The

100 ft copper wire connects to the meter box with it's 200 Amp mains, the other end goes straight away to nowhere, think of it as merely another ground rod, only horizontal 2ft down. When I worked at EAFB for CSC, they did things like this as well as connect every stick of rebar to the future box prior to pouring a concrete floor for new buildings. It simply lowers the earth ground by creating a huge groundplane. The tivo has a phone connection (a potential for dissimilar grounds), However the tivo was not injured. Both decks shared a common outlet. I don't claim to know the answers which is why I'm writing this. I found an interesting site, check out the o-scope pictures and all links at