Kent et al, Regarding different earth ground potentials, the local electric utility company recently participated in the annual spring home show, this year's effort by that utility continued the green hype labeled Pure Power, but the new event was a high voltage safety demo aimed at adults as well as kids. What the enterprising independent contractor (a former utility lineman) presenting from the well equipped three booth wide demo pointed out (among other things) was, in the event of a down high voltage transmission wire coming into contact with your car, the safest place was (to remain) in your car. Only when the car was energized _and_ on fire should you try to exit. Here is the key if you survived this far and a big surprise to me: If you expected to survive exiting the car and "walking" away, you should remember to "bunny hop" (keep your feet together) while you hopped your way from out of the car to a good distance away. He pointed out that the distance between your steps, should you choose to "walk" away, would be between different earth potentials high enough to kill you. Sobering stuff.
How far to hop he did not define and I did not ask. My take away-don't loose your balance while hopping or receive the same unwelcome results as walking. Bill Loesch Solar 1 - Saint Louis Solar ----- Original Message ----- From: Kent Osterberg To: [email protected] ; RE-wrenches Sent: Saturday, March 19, 2011 7:25 PM Subject: Re: [RE-wrenches] Electromagnetic Pulse (EMP) Allan, It isn't easy to find the rational info about this topic amongst the mountain of irrational scare and hype. Consider reading about solar disturbances on National Geograpic News and Geomagnetic storms on Wikipedia. Then read a little about nuclear blast EMP on Wikipedia or many other places. Shake this together and you start to reach the scare and hype that shows up on survivalist blogs. Yes, it is possible for there to be problems. Power and communication systems have been disrupted by geomagnetic storms before. Power and communication systems will have trouble again. Homeowner inverter systems probably won't have any trouble at least not any serious trouble. Yet you can't rule out the possibility that some of them will experience some sort of damage. Communication systems depending on radio wave propagation will certainly experience interference. Some frequencies will be worse than others. Since intense radio interference can cause electronic devices to misoperate, inverters are potentially at risk too. Since the corneal mass ejection, CME, arrives a couple days after the visible solar flare, there is time to prepare and it would be wise to shut things down for the arrival of the CME. IMHO, the risk to solar or battery based inverter from a solar burst is not very great. Wire based communication systems, pipe line systems, and electric power systems are exposed to telluric or earth currents, see telluric current on Wikipedia. To understand why these are a problem, a couple popular misconceptions about earth must be corrected: 1) the earth isn't zero resistance 2) the earth potential isn't the same everywhere. Even copper which is a much better conductor than the earth has resistance! The earth is more akin to large piece of inhomogenous resistive material that we make connections to by poking electrodes into it; much like the doctor sticks electrodes on your chest and back for an EKG. And current flows through this huge resistor system: telluric current, galvanic current, current from cathodic protection systems, current from some electric power systems. So the earth can't possibly all be the same potential. Now take two grounding electrodes that are many miles apart: they certainly are a different potential. If connected by a conductor, current will flow through it - usually just a small current. In an EMP event, the telluric current can suddenly and dramatically change. Possibly change to damaging quantities but more often in a manner that causes power system protection relays to trip lines off unnecessarily. Consider two grounding electrodes a few hundred feet apart - the telluric current isn't likely to be large enough to cause any problem. No electronic communication means no banking, no commerce, no police or fire protection, no internet. By gosh it could be the end of society as we know it. Sell the survivalist a spare inverter and charge controller (all sales final - no returns allowed - because they will probably want to return it after the solar maximum). Kent Osterberg Blue Moutain Solar, Inc Allan Sindelar wrote: For those of us less aware of solar flare issues and what we might expect that relates to PV, could someone provide a good link to educate us? Thanks, Allan Allan Sindelar [email protected] NABCEP Certified Photovoltaic Installer NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Positive Energy, Inc. 3201 Calle Marie Santa Fe, New Mexico 87507 505 424-1112 www.positiveenergysolar.com On 3/19/2011 11:48 AM, R Ray Walters wrote: Hi Drake; No, I don't have answers, just more of your same concerns. I had a high altitude (12,500 ft) installation damaged recently, possibly by a solar flare in Feb; we lost a C40 charge controller. At this point, I don't know if the flare was the cause or not, but I would expect more problems at higher altitudes. So far, my internet research says that the panels and batteries would be ok, but we might expect damage to electronics similar to the induced high voltages caused by lightning. Would grounding help? (I, too, also considered the Faraday cage....) NASA is predicting the solar storm of a generation for 2012-2013, and I read of a similar EMP incident in the 1800s that set telegraph equipment on fire. I think very long utility lines and transformers at the ends of those lines are the most vulnerable, so this could be more of GridTie issue? R. Walters [email protected] Solar Engineer On Mar 19, 2011, at 8:53 AM, Drake wrote: Hello Wrenches, I had an inquiry concerning the effect of EMP on photovoltaic systems. We are heading for a period of solar activity that likely will produce this effect. According to a local AEP (American Electric Power) representative, the utility is spending a lot of money to counter this anticipated problem. Additionally, nuclear related issues are moving back to the front burner. It is clear that the pulse would damage an inverter, but possibly it could be put in a Faraday cage. But a number of questions arise. a.. Would the pulse damage the modules? b.. Could the large currents and voltages induced by EMP damage the conductors in the cells? c.. Even if the inverters were surrounded by a Faraday cage, would induced currents & voltages from the modules harm the inverters? a.. Would series fuses and surge protectors be adequate protection. Has any research been done in this area? Does anyone know answers to any of these questions? Thanks, Drake Drake Chamberlin Athens Electric OH License 44810 CO license 3773 NABCEP Certified PV ------------------------------------------------------------------------------ _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
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