nanog mailing list archives
Re: Reminder: Never connect a generator to home wiring without transfer switch
From: Haudy Kazemi via NANOG <nanog () nanog org>
Date: Wed, 25 Aug 2021 15:47:26 -0500
It's the specific combination of current and voltage that is hazardous. Too much current, through/across the heart, is the main, potentially fatal, hazard. This is why 120v GFCIs trip near 5 milliamps (mA). (20-30 mA in the wrong place is too much.) A voltage pushes a current through a resistance, be that insulation or skin or soil. A 12 volt car battery can produce several hundred amps current, enough to weld, if the terminals are shorted together, but a 12 volt battery doesn't have a high enough voltage to push that current through dry skin. It isn't dangerous to touch a single battery with dry hands. Static electricity can be thousands of volts, but at extremely low current. We feel it as the voltage is high enough, but it isn't actually dangerous (to people; electronic equipment is another matter). Holding the current constant at the danger threshold (20 mA), we can also look at the power levels for various voltages. 20mA at 120v = 2.4 watts. On the other side of the transformer, 20 mA at 7200v = 144 watts. Conclusion: a single small 150 watt inverter is powerful enough to be create a hazard for linemen working on an islanded section of 7200v powerline. There are several categories of electrical hazards, as delineated by voltage. Under 50v is generally considered to not be a shock hazard. More details on voltage categories: https://eecoonline.com/determining-safe-distances-from-electrical-hazards/ More details on GFCIs: https://en.wikipedia.org/wiki/Residual-current_device On Wed, Aug 25, 2021, 13:16 Lady Benjamin Cannon of Glencoe, ASCE < lb () 6by7 net> wrote:
So the issue here is even a small 120vac current becomes a very fatal event at 7.2 or 11 or 14.4kV. It’s a safety issue for linepersons doing emergency restoration work. Ms. Lady Benjamin PD Cannon of Glencoe, ASCE 6x7 Networks & 6x7 Telecom, LLC CEO lb () 6by7 net "The only fully end-to-end encrypted global telecommunications company in the world.” FCC License KJ6FJJ Sent from my iPhone via RFC1149.On Aug 25, 2021, at 7:24 AM, Ethan O'Toole <telmnstr () 757 org> wrote: How would this not load the generator or inverter into oblivion?Not sure I understand your question. Say again, please.If you hook 100KW of neighbors up to your 5KW/20% THD garden generatorit would probably trip the breaker, or stall.I suppose it could be an issue if it was a single house on a branchwhere the break being serviced was just that branch (rural customers.)Was just curious why it wouldn't overload the generator trying to powerall the neighbors houses if connected to the grid.- Ethan
Current thread:
- Re: Reminder: Never connect a generator to home wiring without transfer switch, (continued)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Mark Tinka (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Ethan O'Toole (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Mark Tinka (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch bzs (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Mel Beckman (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Warren Kumari (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Mark Tinka (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Chris Boyd (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Mark Tinka (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Lady Benjamin Cannon of Glencoe, ASCE (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Haudy Kazemi via NANOG (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Mark Tinka (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Jared Mauch (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Mark Tinka (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Dave (Aug 25)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Lamar Owen (Aug 30)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Mark Tinka (Aug 30)
- RE: Reminder: Never connect a generator to home wiring without transfer switch John van Oppen (Aug 30)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Mark Tinka (Aug 30)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Forrest Christian (List Account) (Aug 31)
- Re: Reminder: Never connect a generator to home wiring without transfer switch Mark Tinka (Aug 31)