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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.
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