[RE-wrenches] Hazards of underground feeders

[jay peltz]

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 <william at millersolar.com>
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
>
>
>
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-- 
Jay Peltz
Peltz Power
jay.peltz at gmail.com
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