Dear William, I like all of your ideas, but they have one thing in common, they are all passive. All the placards/labels/signs in the world won't prevent someone from not reading or acting or miss understanding them. So I totally agree with the NEC that we need automatic disconnects that prevent such events in the future.
I think this kind of sad event is the reason for the NEC to require array/string level disconnect. >From what I've heard and I'm sure others are well more versed than I, but we will see module level shutdown required in 2017 NEC, and I for one welcome that. jay peltz power sent: 11.35am 9/6/15 On Fri, Sep 4, 2015 at 2:21 PM, William Miller <[email protected]> wrote: > Dear Friends: > > > > Last week a local well technician was electrocuted. I had just met him in > conjunction with a job we are about to do and realized right away he was a > very nice person. He left behind a wife and two teenagers. Most tragic, > his wife was working with him when it happened. > > > > The scenario is still not fully understood but here is what we do know: > > > > 1. The fellow was digging with a mini-excavator. > > 2. He knew buried lines were present and had turned off all circuits > he thought were included. > > 3. He struck a power feeder. We don’t know if it was direct bury or > in a conduit or if it was AC or DC. > > 4. Based on his impression the conductors were all dead, he jumped > into the ditch with uninsulated dikes to cut the wire. > > 5. He had one hand on a t-post and the other on his pliers. > > 6. His wife grabbed his clothing but could not get him to release his > grip. > > 7. An AT&T tech was nearby and donned hot gloves to pull him off the > circuit. It was too late. > > > > This is an important issue for all of us. We work with high voltage > regularly. We need to think about how to avoid this. > > > > I have connected with high voltage AC many times. My body always reacts > to retract from contact. I got across high voltage DC once. I could not > let go. I had to will myself to throw my arms down to break contact. The > experience was frightening. > > > > On our crew we are integrating what we hope will be reflexive responses to > given procedures. > > > > One is this: Every time you turn off a breaker to work on a circuit, the > next thing you touch is a meter to check that the circuit is de-energized. > > Two: Don’t trust your inductive tester. It will not detect DC. It will > not always indicated voltage present. > > > > This accident was at a local winery. Many wineries in this region have > ground-mounted PV systems, many remote from the main service, therefore > they have underground feeders. Most are string configured systems meaning > the feeders are high voltage. > > > > It occurs to me that the uninformed worker might assume that turning off > all the circuit breakers at the meter will de-energize a circuit, should it > be compromised. Turning of the AC breakers would not de-energize a DC PV > feeder. This is a problem. > > > > I spoke with another well technician about this . He was not aware of the > safety issues associated with PV feeders. > > > > What to do? Here are a few suggestions: > > > > 1. Mark all conduits with bury tape 12” above the conduit. This does > require extra work, you have to make two runs backfilling. > > 2. Sign the meter panel with an indication that opening all the > circuit breakers will not de-energize all circuits on the property > > 3. Include your contact number so you can easily be contacted to > reinforce the steps needed to be taken to excavate safely. > > 4. Always include disconnecting means at a ground-mount array. > > > > This issue is specific to excavation operations, but this reminds me of > why I am so picky about wire shielding on ground mount arrays. This > tragedy could easily happen to a child climbing on a ground-mount rack. > > > > Please add your thoughts on how to best manage the safety issues presented. > > > > William > > > > [image: Gradient Cap_mini] > Lic 773985 > millersolar.com <http://www.millersolar.com/> > 805-438-5600 > > > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/[email protected]/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > > -- Jay Peltz Peltz Power [email protected]
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