Hidden Hazards: A Call to Action for Healthy, Livable Communities
Awareness of Hidden High-Voltage Electrical Hazards For ...
Transcript of Awareness of Hidden High-Voltage Electrical Hazards For ...
Awareness of Hidden High-Voltage Electrical Hazards
For Disaster Service Volunteers
February 6, 2016
Diana Feinberg, AI6DF
Staff 60
Downed power lines usually are obvious in a disaster setting…
As Disaster Volunteers:
DCS is concerned for
your safety
Assume all downed
lines still energized
Stay at least 30 feet
from any downed wire
Keep others away
…but sometimes you can’t see downed wires, as two Good
Samaritans fatally encountered in 2012 after a vehicle accident
Cable might fall behind
fence or bushes next to
you
Wire falls onto metal
fence, possibly
energizing it
Unseen energized
electric lines could be
underground
Street lighting
High voltage
distribution
Hidden Electrical Dangers
Photo: Irfan Khan,
The Los Angeles Times,
August 23, 2012
Be aware: electric utilities often leave a temporary cable on the
ground until digging completed for damaged underground line
Example:
During three-week
period to replace
damaged 16000-
volt underground
cable, SCE laid
temporary high-
voltage line on
ground next to fire
hydrants and
irrigation
sprinklers
Hidden Electrical Dangers of Temporary Electric Lines
Photos: Diana Feinberg, AI6DF
This electrical vault was energized and fed the damaged next vault
Vehicles had to repeatedly drive over temporary cable
Be aware: electric utilities often leave a temporary cable on the
ground until digging completed for damaged underground line
SCE temporary line directed through garden areas to damaged vault
Be aware: electric utilities often leave a temporary cable on the
ground until digging completed for damaged underground line
SCE temporary line along sidewalk leading to damaged vault
Be aware: electric utilities often leave a temporary cable on the
ground until digging completed for damaged underground line
SCE temporary line to damaged vault had minimal cautions
Be aware: electric utilities often leave a temporary cable on the
ground until digging completed for damaged underground line
SCE pole transformer temporarily on ground feeding power to damaged vault
Be aware: electric utilities often leave a temporary cable on the
ground until digging completed for damaged underground line
What’s On That Utility Pole?
Poles on Pacific Coast Hwy. near Crenshaw in Torrance
Know what wires are on utility poles: It varies, but SoCal
Edison has fairly consistent layouts with 3 wires to a circuit
Words of high-voltage electrical safety wisdom:
“Three’s Company”, “Heads Up”, and “Dry Below”
“Three’s Company”:
All AC utility circuits have three wires (some have four)
Service drop to homes and many businesses “looks” like one
cable
If less than three wires seen on circuit, potential problem nearby
“Heads Up”: Look up to inspect utility poles at your location
Any insulator on pole missing a wire?
Use flashlight at night
“Dry Below”: If ground damp or under water, look for all electrical
sources before approaching
Utility poles nearby?
Street lights (mostly 230-480 volts) and traffic signals—still on?
If one street/traffic light downed, others still on, downed light
might be energized
Electrical Safety Warnings for Disaster Volunteers
What’s On That Utility Pole?
Poles on Pacific Coast Hwy. near Crenshaw in Torrance
Sub-Transmission
50,000 – 200,000 volts
Two Primary
4,000 – 30,000 volts
Secondary
115/230/480 volts
Transformer
steps down
primary to
secondary
voltage
Know what wires are on a utility pole: Look up to see if three
cables are affixed in each circuit
What’s On That Utility Pole?
Poles at Hawthorne Blvd. and Indian Peak Road, Rolling Hills Estates
Below all electric cables are those for cable TV and telephone
Below all electric cables are those for cable TV and telephone
What’s On That Utility Pole?
Poles seen at Hawthorne Blvd. and Indian Peak Road, Rolling Hills Estates
Cable TV
Phone Co.
Two Primary
Two Sub-Transmission Circuits
Secondary
Guy Wires
Underground electric lines are aesthetically nicer and higher
cost, but have their own hidden risks
All underground utilities
might be in same trench
Older real estate
developments did not use
conduit to protect
underground electric cables
Underground electric cable
break starts with small
arcing, then arc lengthens--
punctures adjacent utility
lines
Things to Know About Underground Lines
Arc between two electrified metal pieces separating is short at first, becomes longer as
gap widens
Pre-1986 construction only required
12” vertical and 12” horizontal
separation of buried gas and
electric lines; now it’s 18”
Testing inside electricity and AC-devices can be safety done
with a Voltage Tester—but specialized tools needed outside
$15-$25 Non-Contact Voltage Testers
widely available
Get one rated for Cat IV, 1000V
Only detect AC voltage
Test both sides of any wire;
wearing gloves can give false
reading
More expensive Voltage Testers
needed for high voltages
You Can Safely Check for Presence of Indoor AC Power
Be safe when serving as a disaster volunteer near electric
lines…and thanks for watching this information
“Three’s Company” — AC circuits should have three cables
“Heads Up”—Look up for any missing cables
“Dry Below” —Think carefully if ground is wet: don’t step
into water if any indication of electricity malfunction
Stay at least 30 feet from any downed line or pole
Be aware of underground electrical lines
Watch for any temporary high-voltage lines on ground, stay
away if wet or raining
Concepts to Remember