[RE-wrenches] Hazards of underground feeders

[William Miller]

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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