grounding compliance to avoid step potential hazards potential awarenes… · in touch potential,...

Northwest Hydro Tech Session_2017

STEP POTENTIAL FROM AN

OPERATORS VIEWPresented by Fred

WAC 296-45-005 ELECTRICAL WORKERS SAFETY RULES-FOREWORD.

This chapter is not intended to be a complete

job description nor is it expected that the

chapter covers every hazard that an employee

may encounter. When a hazard exists that is not

covered by this chapter, the leadworker and

employees are expected, in good faith, to

mutually discuss the hazard and agree how to

perform the work with the greatest degree of

safety.


WAC 296-45-005 ELECTRICAL WORKERS SAFETY RULES

Experience has proven that the majority of injuries and

deaths are preventable. Most injuries and deaths are

not due to defective equipment but are due to failure

on the part of the employees and those in authority to

observe safety rules and failure to use safety devices.

In the last analysis, this chapter is a compilation of

experience and common sense. Electrical safety

requires that the work be properly planned, executed

by the use of good judgment and under the direction

of intelligent supervision.


WAC 296-45-015 SCOPE AND

APPLICATION.

(1) This chapter covers the operation,

maintenance, and construction of

electric power generation, control,

transformation, transmission, and

distribution lines and equipment.

These provisions apply to:


WAC 296-45-015 SCOPE AND APPLICATION.

(a) Power generation, transmission, and

distribution installations, including related

equipment for the purpose of

communication or metering, which are

accessible only to qualified electrical

employees;


THIS SECTION APPLIES TO WORK ON EXPOSED LIVE PARTS, OR

NEAR ENOUGH TO THEM, TO EXPOSE THE EMPLOYEE TO ANY

HAZARD THEY PRESENT.

(1) GENERAL. ONLY QUALIFIED ELECTRICAL EMPLOYEES MAY

WORK ON OR WITH EXPOSED ENERGIZED LINES OR PARTS OF

EQUIPMENT. ONLY QUALIFIED ELECTRICAL EMPLOYEES MAY

WORK IN AREAS CONTAINING UNGUARDED, UNINSULATED

ENERGIZED LINES OR PARTS OF EQUIPMENT OPERATING AT 50

VOLTS OR MORE. ELECTRIC LINES AND EQUIPMENT SHALL BE

CONSIDERED AND TREATED AS ENERGIZED UNLESS THE

PROVISIONS OF WAC 296-45-175 THROUGH 296-45-17565 OR

296-45-335 HAVE BEEN FOLLOWED.

WAC 296-45-325 Working on or near exposed energized parts.

(3) EQUIPOTENTIAL ZONE. TEMPORARY PROTECTIVE

GROUNDS AND BONDING JUMPERS SHALL BE PLACED

AT SUCH LOCATIONS AND ARRANGED IN SUCH A

MANNER AS TO PREVENT EACH EMPLOYEE FROM

BEING EXPOSED TO HAZARDOUS DIFFERENCES IN

ELECTRICAL POTENTIAL.

WAC 296-45-345: Grounding for

the Protection of employees


Hazard Avoidance Practices

The employer must assure that each employee has been

trained to recognize and is appropriately qualified to work

near any electrical hazard that might be encountered at a

worksite.

Tree workers using ladders, platforms, and aerial devices,

including insulated aerial devices, are subject to the same

minimum approach distances as other tree workers.


In touch potential, if someone touches what is in

contact with the powerline, electricity will travel

through that person’s body to get to the ground.


TOUCH OR STEP POTENTIAL?



Potential Hazard Situations

Lightning

Downed wires

Energized vehicles or tools

Energized, grounded trees or tree

limbs


In step potential, electricity spreads like

ripples or rings over the surface of the

ground away from the point of the contact.

Each ring carries a different voltage as it

travels into the ground. If they step on one

ring while their foot is on the other ring

electricity will make up to difference in

voltage through the body.


In August of 2013 Madras mourns a

local farmer killed by lightning beneath a tree.

OSLO (AFP) - MORE THAN 300 WILD REINDEER HAVE BEEN KILLED BY LIGHTNING IN SOUTHERN NORWAY,

OFFICIALS SAID MONDAY, IN THE LARGEST SUCH INCIDENT KNOWN TO DATE.

THE 323 REINDEER, INCLUDING 70 YOUNG, WERE FOUND ON FRIDAY BY A GAMEKEEPER ON THE

HARDANGERVIDDA PLATEAU, A NATIONAL PARK WHERE EUROPE'S LARGEST HERD OF SOME 10,000 WILD

REINDEER ROAM FREENorthwest Hydro Tech Session_2017

Researchers suspect what happened to

the caribou was: a single bolt of

lightning hit the ground and the electric

current spread horizontally along the

moist top soil. As it hit the front legs of the

caribou, a "potential difference

developed between the animals' front

and back hooves." That causes a jolt,

which stopped their hearts, and that's

how you kill 53 caribous in a split second.



This is a very strong reminder of what Lightning can do. This was

somewhere in McCook County. There is 21 head of cattle that were

around this metal bale feeder when it was hit with one bolt of

lightening and it killed them all. That is about $45,000 worth of loss.


All the cows facing the lightning strike would have their fore

hooves closer to the strike point than their rear hooves. This

would result in a difference of potential between their fore and

rear legs, causing current to flow through their bodies, including

the heart area, and killing the cow.

On the other hand, those cows with their flanks turned towards

the lighting strike would have a greater chance of surviving, as

the distance between their fore legs and therefore the voltage

applied between them, would be relatively small, resulting in a

lesser current flow.

Probably the most commonly noted Ground

Potential Rise or Earth Potential Rise event involves

the death of cows in a field during a lightning strike.

Imagine lightning striking the center of an open

field where cows are standing. The current injected

into the earth flows radially away from the strike

point, in all directions, creating voltage gradients

on the surface of the earth, also in a radial

direction.


According to the NOAA, there were

five people killed in the U.S. last year

by lightning strikes: two in Florida,

two in Louisiana and one in

Mississippi. There were 27 deaths in

2015.


http://www.lightningsafety.noaa.gov/fatalities.shtml

As the severe weather starts to roll in

this summer please keep this in

mind. If you start to see lightning

and hear thunder you need to get

out of the open. Off of the Lakes, off

of the Golf Course etc so that you

are safe.


Aerial devices brought into contact with

energized electrical conductors shall be

considered energized.

Contact with the vehicle and/or any

attached equipment such as brush

chippers must be avoided


Workers must never assume that a

conductor lying on the ground is de-

energized unless a utility

representative on-site has

confirmed that it is so.


Escaping Step Potential Hazards Use very short, shuffling steps, or move

away from the electrical fault keeping both

feet close together.

Avoid taking large steps.

Avoid direct or indirect contact with any

objects as you exit the hazard area.



FRED L. NAUGHT, C.U.S.P.

High Voltage Consultant

Department of Labor and Industries

Division of Occupational Safety and Health

Cell #(509)979-1506

FAX #(509)324-2618

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