14.0 Electricity Safety

7/23/2019 14.0 Electricity Safety

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OBJECTIVE

By the end of this presentation, participants should

be able to:-

1.To know how electricity is being generated,transmitted and distributed for use at consumer

level.

2.To appreciate that electricity is good but can bedangerous if safety is not observed.

.To know how electricity accident can be prevented.


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!"T#$%&'T!$" By its nature, (lectricity in its generation, Transmission,

%istribution and even its use at home, inherently constitute

very serious ha)ards. *or this reason and its high risk tendencies

electricity is guided by certain universally accepted safely rules.

(lectricity safety has been a recogni)ed sub+ect since the turn of

the century but the lessons are still being learned the hard way.

This is mainly because there has been no proper learning in the

rst place by those who have assumed the title of (ngineers,

electricians or technicians and their likes.


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POWER SYSTEM Power System: ower /ystem is made up of various voltages at

the generation, transmission, switching and distribution0load centre.

Supply System:The supply system consists of network of conductors

and associated euipment over which energy is transmitted from the

transmission system and the distribution system. Transmission can

further be divided into primary and secondary.

%istribution may be divided into primary, secondary and tertiary.

enerally for lternating 'urrent 3'4 system, there will be a change

in voltage at each point where a sub-division takes place.


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The change is attached by transformation, usually at a sub-

station. This implies that there may be several operating

voltages in one system. !t is classied in this form.

#!5#6 T#"/5!//!$" - 17089

/('$"%#6 - 80129

#!5#6 %!/T#!B&T!$" - 1209

/('$"%#6 %!/T#!B&T!$" - 0119

T(#T!#6 %!/T#!B&T!$" - 1108.;1


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(=('T#!'!T6 ''!%("T/ (lectricity is a safe and also an e>cient form of energy and itsbenets to man cannot be over emphasi)ed. !t becomes

dangerous when it is misused

TYPES OF ELECTRICITY ACCIDETS

- (lectric shock

- (lectric burns

- *ire and (?plosion

- (ye *lash

- #adiation

- *alls from height


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S!OC"

n electric shock is caused by the passage of an electric

current through the body causing a paralysis of the muscles

particularly the heart muscles.

- !t is usually painful but is not necessarily associated with

actual damage to the tissues of the body.

- s a result of a moderately severe shock a man may grip

and unable to release a conductor or a tool.

- !f he has touched a live conductor without grasping it thepowerful muscle of his back and legs may contract violently

so that he involuntarily springs backwards and falls.


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But in direct current this involving grip phenomenon is not

there and generally the shock produced is not dangerous as

that of ' current.

VETRIC#LAR FIBRILLATIO $ITERFERACE WIT! !EART%

- !t is generally believed that the great ma+ority of fatalelectrical accidents are caused by ventricular brillation of

heart, which prevents its acting as an e@ective pump, and

death follows uickly as a result of lack of o?ygen supply to

the brain.

- heavy current passing through the body can kill by causing

severe tissue damage.


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ELECTRICAL VAL#ES ASSOCIATED WIT! !#MA IJ#RYThere are four main concerned:-

- alue of electrical voltage.

- alue of electric current passing through the body.

- (lectrical freuency.

- !mpedance of human body.

T&e Se'er(t(es o) * s&o+, -epe.- upo. t&e )ollow(./

)*+tors

- Becomes more severe with increase in voltage applied.

- !ncreases due to the amount of moisture on contact surface.

- !ncreases with an increase in pressure of contact.


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- !ncrease with the increase in area of body contact.

- #esistance of body portion.

- %ecrease in freuency.

B#RS AD SIDE EFFECT

person who has received an electric shock and survive usually

su@ers no in+ury unless they have had a severe fall or burned.

Burns are in fact the most serious after-e@ect of electrical

accidents.

. COTACT B#RS

Ahere the patient has touched a live conductor

B0 RADIATIO B#RS FROM S!ORT1CIRC#IT ARCI2

Though this is in e@ect a severe form of sunburn.


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!ntense electromagnetic elds can cause current ow in or

near the human body.

This can result in:- - Burns caused by the raising of the temperature of the whole

body.

- =ocali)ed in+ury e.g. cataract formation in the eye 3T..

viewers should not seat close to the screen.

FIRE AD E3PLOSIO

The great ma+ority of res are associated with appliances and

number occurring each year is fairly proportional to the

increase in power consumption.

The two ma+or causes of (lectrical res in "igeria are

associated with wrong installations and overloading.


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The rst few times, it will probably be a fuse 3if it has not been

replaced with a wire.

$ne cannot stop the passage of time, but it should be reali)ed

that as installations increase in age, they decrease in terms of

safety. !t is necessary, therefore, for installation to be

periodically inspected and tested. The period may vary

according to the type and nature of the installation, but onceevery year would not be too often.

!f there is a short circuit, it also results to e?cess current with a

resultant re accident.

Ahen a base wire arc is against a system at a di@erent

potential, the considerable head of the arc causes a re.

!f more of e?cess current ow in a conductor above its rating, it

may become e?cessively hot.


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F(re *.- E4plos(o.

The ma+ority of res occurring each year are fairly proportional to the

increase in power consumption.

!t has been discovered that the incidence of re outbreaks in all types

of premises in uite a high proportion are caused due mainly to

electricity.

T&e m*5or +*uses o) ele+tr(+*l 6re *re:1

C %efective appliance

C Arong installation

C $verloading 3$verheating of installation cables i.e tendency to keep

adding electrical appliance to an installation until something fails.

C The use of substandard or wrong type of materials.

C !nstallation not properly maintained and tested .


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C*uses Co.t(.ue

C !f there is a short circuit, it can also result to e?cess current

with a resultant re accident.

C Ahen a base wire arc against a system at a di@erent potential,

the considerable heat of the arc causes a re.

E4plos(o.

(?plosion had occurred inside the feeder pillar due to twisted

aluminum conductor on top of the pole or leakage from the

feeder pillars itself.

CArong switching from the #5&.

C =ack of regular inspection and maintenance of transformer.

C $verloading and fault causes overheating of transformer

windings and cause cumulative damage to the insulation.


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C 5ost insulating materials are to some degrees ammable eg

ceramics

Pre'e.t(o.:

$ne cannot stop the passage of time, installation increase in age, they

decrease in terms of safety.

C !nstallation should be inspected and tested periodically i.e. varyaccordingly to the type and nature of the installation.

C The engineer or technician designing must specify the correct

euipment and material e.g ame proof euipment in e?plosion areas.

C !nstallation contractor must read the specication and comply with it.

C The use of substandard or wrong types of materials nust be avoided.


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EYE FLAS! $ARC EYE ORCOJ#CTIVITIS

The category of very temporary discomfort orincapacity which is not serious but very painfulcondition resembling pepper, sand or grit in theeyes and develops some hours after e?posure to

an intense source of arc violet light. This result inthe person su@ering from empirical blindness. !tmay occur when a person is e?posed to a severeshort circuit but it is primarily conrmed to workwith electric welding and potentially to arc furnace

worker. *ortunately are eye pose no permanentin+ury.


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RADIATIOThe magnitude of modern high tension andlow installation has associated short circuitenergies which are so great that the arcs caninict radiation burns and blindness somedistance away.


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FALLS FROM !I2! OVER!EADLIES

ccident happens on overhead lines when

person falls from pole, crane or ladder, due to a

bad ladder or rusted wooden pole. !t could be

from electric shock, some may occur due to

back feeding of supply from unknown source to

a person working on lines. nother may occur

during lightening due to a bad weather inrainny seasons which will make one to fall. !t

appears that electric shock causes the body

and muscles to recoil with violence.


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SOME OF T!E CA#SES OF

ELECTRICAL ACCIDETS"eglect to safety code of practice.

!mpatience of the workman.

!llegality.!gnorance i.e. member of the public.

*ailure to use (.

%efective tools, euipment.

&nsafe methods, process and procedure.

5aking contact ignorantly on naked live wires.


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DEFECTIVE APPLIACE%o cause accidents but it could be stressed

that is largely a maintenance problem and

most of the onus lies with the owner of the

appliance. !t is a fault among many people

that appliances are allowed to function

unattended with no maintenance, until either

they fail to work or an accident occurs.


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SOME CA#SES OF ELECTRICAL

ACCIDETS 7 PREVETIOeople will not receive serious electric chocks orcontact burns unless they touch live conductors.

The obvious remedies are to make liveconductors inaccessible.

$thers preventive measures as follows- &sing low voltage- !nsulating and0or enclosing live parts- reventing conducting parts from becoming

live.- By earthling and automatic disconnection ofthe supply


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- By double insulation- &sing euipment as dened in the

makerDs instruction.- (nsuring that electrical euipment isadeuately maintained.- inspection or risk assessment.- avoiding the use of electricityaltogether where its use would bedangerous.

- "ever work on a live circuit, if you canpossibly avoid it.- "ever rely on insulated tools forprotection i.e. insulation easily cracks.


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Test to be sure that the circuit is deadbefore working on it.

!f you must work on a live wire or supplyuse good uality isolated tools i.e. ood(

%o not match on any E'"

conductor0cable whether energi)ed or not.void as much as possible building under

electric lines.

void tempering with E'" facilities.

/hould not attempt erecting antenna nearelectric wires.


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!f you witness an accident due to shock resulting

to unconsciousness or you nd an unconscious,

colleague, remember the followingF1.(nsure that the victim is not still in contact with

the electrical system. !f you touch him while he is

still in contact, you will eually receive shock.

/witch of the circuit, where not possible, drag himout with dry cloth or dry wood.

2.%o not waste time trying to nd out if he is alive.

6ou can start respiration at once.

.'all for assistance i.e. doctor, ambulance at once.!f you are on your own shout for help periodically.


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OCC#PATIOAL !EALT!

PROPBLEMS D#E TOELECTRICITY #adiation ha)ards due to long

transmission lines.

$ccupational health problems withelectricity are usually di>cult tomanage than safety problems becausethe causes are usually very obscure.

!t takes time to manifests while thevictim may have change +ob or retired,before the e@ect start to show.


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CA#SES"o measures in place to monitor work related

health problem!gnorance or nonchalant attitude

RADIATIO D#E TO LO2 TRASMISSIO LIE (lectric power transmission lines produces

electronmagnietic elds 3(mf4. The strengths of both electric and magnetic elds

decrease with distance. The higher the voltage the stronger the (mf. (?posure to it has wide variety of e@ects.

ERVO#S SYSTEM


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8 ERVO#S SYSTEM

@ecting the brain function and behavior pattern of

small children.

8 CARDIOVOCAS#LAR SYSTEM0

'hanges the electrical activities of the heart.

8 BLOOD

'auses changes in the balance between red and

white blood cells. =owering the immune system.

T!E REPROD#CTIVE SYSTEM

In males sperm cell production is lowered and in

females estrous cycles is disrupted and

conseuently fertility is lowered which causes

chromosomal changes.


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OTE:

people that temporarily stay under or close to Eigh

tension lines are not e?posed to electrical ha)ards.

Eowever long e?posures could lead to health risks.

8 POLYC!LORIATED BIP!EYLES PCBS

Because of the high risks associated with oilsolychlorinated Biphenyls 3'Bs4 were introduced

in place of mineral oil.

'Bs are chemical organic compounds which are inuse as electric uids in electrical euipment, heat

transfer uids in mechanical operations,

plastici)ers, lines, surface coatings etc.


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POLYC!LORIATED BIP!EYLES PCB

'Bs have e?cellent (lectrical properties i.e. is

non-o?idi)ing, high resistant to thermal break

down, insoluble in water, resistant to acids,

alkalis and corrosive chemicals, e?tremelystable thermally, non ammable. Eigh

dielectric constant, high resistivity, high

dielectric strength and very low power loss

factor enabled transformers and other electric

euipment to function e@ectively.


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ITS EFFECTS!t dissolves easily in fatty tissues and other

organic hydrocarbons

!t accumulates in the fatty tissues of man, and

animals when e?posed to it.

!EALT! !A9ARDS

!mpotence, memory loss, eye irritation,

depression and respiratory problems. =ong term e@ect i.e. increase in the incidence

of cancer of the liver and rectum.


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/kin diseases, "ervous disorders and respiratory tract

irritation.

astro-intestinal system and reduction in lung capacity.

/ome auatic organisms, i.e. sh are killed at very low

levels of 'B/ and end up in the human food chain.

Aater polluted by 'B/ causes very serious healthe@ect.

'B can be recycled during operation in the transfer of

oil from contaminated transformers, capacitors and

reactors. lot of spillages occur during maintenance.

/pills could contaminate the environment and pose

serious health and safety risks.


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STAT#TORY RE#IREMETS

There are three main sets of regulations to which

we must conform in order that an installation

shall be safe from e?cess current shock, re,

corrosion, mechanical damage and leakage.1.(lectricity 3factories ct4 special regulations,

1G8H and 1G;;.

2.The electricity supply regulation 31GI4.

.#egulation for the electrical euipment of

buildings.


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COCL#SIO

C Ae must urge all users of electrical euipment

to ensure that the euipment are properly

maintained and serviced.

C Training on rst aid should be a must for all

users of electricity.

Aith regard to misuse of electricity by public is

an educational and publicity problem this is an

area of social responsibility in which electricity

company and safety professionals should

collaborate.


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*inally there is actually very little which is

completely new in the eld of electrical safety

most of the lessons have been discovered

many years, the problem is that each

generation of engineers needs to learn them

and older engineers may need to refresh their

memories from time to time.

14.0 Electricity Safety

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