Didn't mean to mislead -- my comment about "feeling the electricity in the air" is just that, a subjective feeling.... Maybe ozone played a part; I was too young and inexperianced to recognize it if that were the case. More of a sensation -- I do remember the 60Hz hum coming from all directions as soon as you entered the sub-station......
Mike Hopkins > -----Original Message----- > From: [email protected] [SMTP:[email protected]] > Sent: Wednesday, March 31, 1999 5:36 PM > To: [email protected] > Subject: ESD in Power Station > > Hi, > > Please allow me to pose two questions. > > (1) What did Mike Hopkins and Scott Douglas really feel and smell about > "electricity in the air" when these two boys went to electricity stations > with their fathers? My guess -- that's air ions and ozone, which are > easily > produced in a strong AC EM field. If this is true, can we say: "The more > ions in the air, the easier ESD would happen"? > (2) The eddy current on moving conductors in a strong H-field would > produce > eddy resistance in moving direction. That's a good explanation for slow > watch on the spot. But my question: "How come an AC (not DC) H-field left > the moving iron with residue magnetization which causes the watch > continuing slow after leaving the station?" > > Barry Ma > ---------------------------- > From: "Robert Macy" <[email protected]>, on 3/31/99 12:33 PM: > > IMHO the magnetic fields go right through the watchcase and either disrupt > > what's going on or can even magnetize the parts. Either way, the parts > are > like "stuck" together and the watch won't run well. > > Also, my father could never wear a watch, a great gift watch always would > stop. The same watch given to my brother, lost ten minutes a day. So when > > I got the watch I was happy when it gained a few seconds a month and > lasted > for over ten years. Go figure. > > --------------------------- > From: "Mike Hopkins" <[email protected]>, on 3/30/99 9:48 PM: > > Very interesting -- my father also worked for what was then New England > Power and was a substation operator in Tewksbury, MA -- he also went to > other smaller sub-stations to switch lines in or out for maintenance or to > > clear trouble problems and I have similar recollections about the > electricity "in the air" -- you really could feel it! An interesting side > note - he could never wear a watch of any kind -- they would either run in > > their own time zones or not work for long at all -- he attributed this to > the surrounding electric fields, but I've never figured out how that would > > affect a mechanical watch! > > As for ESD (human ESD) as opposed to AC electric or magnetic fields, the > levels of 8kV and 15kV (contact/air) are on the high side. Discharges of a > > few kV happen all the time without us even knowing it; discharges that we > feel on a dry day are typically in the 5 to 10kV range, but a 15kV > discharge from the end of your finger is something you'd remember! Even > 10kV is pretty uncomfortable...... > > Hope this is helpful, but I doubt it would influence the people who wrote > the standard... > > ------------------------------- > From: "Scott Douglas" <[email protected]>, on 3/30/99 9:43 AM: > > My father worked for the electric utility for many years. There were > times > he could take me with him to check on how a substation was working after > some maintenance or upgrade was performed. From direct experience I can > tell you that when you enter the substation building, you can quite often > feel and smell the electricity in the air. The electrostatic fields that > build up in these environments can be substantial. Yes, everything inside > is well grounded, but when you have thousands of volts running around big > copper bus bars, switching systems, transformers, etc. you hear the hum > and > feel the electricity in the air. Back then, I thought it was really neat > as > I did not have the healthy respect that I have since acquired the hard > way. > > One other thought here, would you want your TV going blink just at the > end > of the local cricket match or the last quarter of the World Cup "football" > > game? That could happen if some protective device or overcurrent sensor > got > zapped and caused a shutdown when there was really no system problem > requiring a shutdown. > > --------------------------- > From: " Peter Poulos" <[email protected]>, on 3/30/1999 5:54 AM > > I've recently been shown a standard published by a European group called > UNIPEDE titled "Automation and Control Apparatus for Generating Stations > and Substations - Electromagnetic Compatibility Immunity Requirements" - > Ref# 23005Ren9523. > > This standard generally adheres to the same requirements for immunity as > the CE-mark standards, however for ESD it requires 8kV contact and 15kV > air > for HV substation environments. As is usually the case, there's no > rationale provided as to why these level where chosen (something that > really annoys me about most standards). > > Does anyone have suggestions as to why the authors of the standard would > expect worse ESD conditions in a substation than they seem to expect in an > > air conditioned, carpeted office? (equipment in environments other than HV > > substations only need meet 6kV contact, 8kV air according to this > standard) > > > > Thank you. > Best Regards, > Barry Ma > x4465 > > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
