This seems to make the most sense - the construction you describe sounds like you potentially have several separate conductors with the potential (pun unintended) to become charged. Someone else had a figure for capacitance betwixt wires in a pair - a figure of around 70nF/mile for multi-pair telecommunications cable (way back then, we're metric now) rings a bell. That is between conductors in one pair. Lots of pairs will have lots of separate capacitors. Someone else can work out the energy stored (1/2CV^2) - its late here in tomorrow so I'm off to bed. -----Original Message----- From: richard skinner To: PICLIST@MITVMA.MIT.EDU Date: Thursday, 12 March 1998 00:13 Subject: Re: [OT] Cable retained energy, was Super Caps >The cable he used was clx, I think. It is built almost like coax. It can >have any number of pairs in it. >Each individual wire inside consists of a core, insulator, Wrapped with a >thin layer of foil. Some of this >wire has anywhere from a single conductor to say 12 conductors in side. The >very outside has a dielectric >type of grease before the final sheath or insulation. Nice wire, used >offshore on platforms all the time, however, >it is a pain to work with. When it gets old, it is tough to peel the foil of >the outside of each strand, then ofcourse, >the grease sure doesn't help matters any trying to tape it or grip it. > >Static Electricity? I don't know, can it be created by salt water waves >sloshing against the legs of the platform? >Could it be parasitic charges from the generators on board? Geez, I have no >idea. I know that it should definetly >have a good ground since its sitting on the ocean flooring with a ton of dirt >or mud holding it in place. > >The cable was intentionally charged and then discharged to prove to me it >would hold a charge, and to prove to >me it must be discharged before handling. It had to be proved as I though my >leg was being pulled. > >I have seen formulas here saying that it is not possible, and I've seen >people saying yes it was possible for these >spools to hold a charge, All I know, and I have NO reason to make up short >stories on spools of wire, is he proved >it to me by doing it. > >It did seem like an interesting debate, > >Richard Skinner >rwskinner@worldnet.att.net >http://home.att.net/~rwskinner > >---------- >> From: Mike Keitz >> To: PICLIST@MITVMA.MIT.EDU >> Subject: Re: [OT] Cable retained energy, was Super Caps >> Date: Tuesday, March 10, 1998 10:18 PM >> >> On Tue, 10 Mar 1998 21:38:31 -0500 Sean Breheny >> writes: >> > Jorge has mentioned that this phenomenon is >> >observable when dealing with power transmission line. Power >> >transmission >> >line is not coaxial, is it? >> >> The stuff that is buried underground and used from about 2 KV up to maybe >> 50 KV (e.g. for distribution to transformers in neighborhoods) is. It >> has a copper or aluminum conductor at the core, thick polyethylene >> insulation, then a shield made out of metal braid and conductive plastic, >> and finally a black plastic outer covering. The shield is likely not >> intended to normally carry current. It is connected to ground at both >> ends for safety reasons. Maybe some single-phase circuits use it as the >> return conductor. In any case, the coaxial construction makes it >> difficult for high voltage to appear on the outside of the cable if there >> is a leakage, cut or hole in the insulation. Such a circumstance will >> cause the cable to arc and the fuse or circuit breaker to open. This >> line is of course routinely "hipot" tested before installation by >> connecting a high voltage between the center and the shield and measuring >> any leakage. A big spool of it charged to many KV would indeed be >> dangerous. The polyethylene insulation would prevent the charge from >> leaking off for a long time as well as maybe causing a phantom "recharge" >> from dielectric absorption. >> >> Of course such cable is intended for use at 60 Hz and is not designed for >> any particular impedance. >> >> >I have always been told that it is single >> >conductor woven cable, >> >> The wire strung overhead between poles is laid up of strands of aluminum >> on the outside, and steel on the inside. The steel is to make it >> stronger. Even at 60 Hz, there is enough of a "skin effect" to reduce >> the effectiveness of the conductors in the center, so the aluminum is >> outside. Except in special cases, it is bare. Please do not climb >> power poles and touch the wires. You will get hurt. Really high power >> lines have several cables in parallel. They are held apart in a triangle >> or square arrangment to make the apparent diameter of the conductor as >> large as possible. This improves the impedance and current distribution >> along the line. When dealing with hundreds of km of cable, AC effects >> such as phase shifts are very real at 60 Hz. >> >> sometimes with a hollow core with a coolent run >> >through it. >> >> In power "substations" the conductors are sometimes placed inside much >> larger outer pipes. The pipes are filled with sulfur hexafluoride gas. >> SF6 is a much better insulator than air, as well as being certain to be >> clean and dry, so the conductors can be in closer proximity than if they >> were strung out in the open. This is rather expensive so it is done only >> for extremely high voltages or where the real estate to lay out the >> station with larger seperations would be even more expensive. >> >> I don't think the conductors in transmission systems are hollow or >> actively cooled in any way. Hollow cooled wire is used to wind >> generators and big motors. Hydrogen (H2) gas was used as the coolant in >> one example I saw. It's both very "thin" and light (i.e. easy to move at >> high velocity through small hollow passages) and absorbs heat well. It >> doesn't seem that H2 gas and big electrical machines should be used near >> each other. >> >> This is what I remember from several years ago; current practices may be >> different. >> >> ____________________________________________________________ _________ >> You don't need to buy Internet access to use free Internet e-mail. >> Get completely free e-mail from Juno at http://www.juno.com >> Or call Juno at (800) 654-JUNO [654-5866] >