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