ELECTRICAL SAFETY

~Every year, thousands of workers are electrocuted or suffer serious electrical shock on the job.
~Only 1.0 amp of electricity flowing through the human body two second can cause death.
~Electric fault has been the major cause of industrial fire & explosion for over a century.
~Electrical hazards have become a particular concern to both factories and households.

COMMON ELECTRICAL HAZARDS-
~Exposed Wiring / Damaged Live Cables
~No Earthing
~Overloading
~Without overcurrent protection
~Improper use of flexible cords
~Inadequate insulation

COMMON ADVERSE FEATURES FROM FACTORIES IN ASIA-

~Connections between cables are not soldered or mechanically fastened (Overheating Potential)
~Incorrect size fuses fitted.
~No earth conductors to power outlets.
~Cables with borderline power rating.
~Insufficient use of circuit breakers rather than fuses
~Some local electrical equipment is not reliable
~Exposure to vermin (eg. Rat) can be a problem.
~Mounting board made of combustible material (eg wood)
~Stacking against electrical panels/equipment
~Exposed wiring
~Abuse on usage of flexible cords
~Lacking or regular inspection & maintenance
~Unauthorised tampering wiring.

ELECTRICAL HAZARDS PREVENTION-

~Proper Wiring & Overcurrent Protection
~Earthing & Bonding
~Insulation
~Isolation
~Annual Thermographic Surveys
~Safe Work Practices

PROPER WIRING-

CABLES
~Should be protected by conduit, metal sheaths or trunking
~Connections between cables must be soldered or fastened
~Should be sized at least 120% of the sum of full load currents
~All electrical installations should be made in compliance with local requirements and recognition of international standards such as AS 3000, National Electrical Code (NEC) of NFPA or OSHA standards
~Protection measures against direct contact
~Power distribution systems must be equipped with overcurrent protection

OVERCURRENT PROTECTION COMMON MEANS-

~Fuses
~Circuit Breakers
~Ground-Fault Interrupter (GFI)

FUSES-

~Melt at a predetermined value of current & open the circuit
~Should be placed in the live conductor and never in the neutral conductor
~Overfusing should be avoided
~Not fast response and less reliable
~Simple wire fuses should never be replaced with copper wire -
DANGEROUS

CIRCUIT BREAKER-

~ Principle
-excess current detected electromagnetically
- automatically trips and cut off electricity supply
~Faster response and more reliable
~Difficult to tamper.

GROUND-FAULT INTERRUPTER (GFI) -

~Principle
[A differential transformer (torodial)]
Detects any current passing to ground through any path other than the proper conductor and trips and opens the circuit within 2.65 milliseconds
~Provides a good protection, as the majority of electric shock injuries occur when the body acts as conductor between line & earth
~Very fast response and sensitive device
~Commonly installed for socket outlet circuit & overhead line system

EARTHING AND BONDING-
~Eliminate a difference in electrical potential between a conductive object and the ground by connecting them
~Provide a path with lover resistance to the current than a person
(less than 2 ohms)
~All exposed metalwork which could become alive MUST be earthed

Bonding :
~Bonds all surfaces at the same grounded electrical potential
~Provides a ground-fault current path back to the source and the current will rise to a level high enough to blow the fuse or breaker
~Regular and frequent inspections / tests by competent person

INSULATION -

~Exposed live parts should be adequately insulated if at all possible
~Make use of insulating mats or gloves to protect against electric shock when working on a high voltage equipment
~Periodic examination of all insulating covers and devices

ISOLATION-

~All electrical equipment or apparatus that may require frequent attention must be capable of being completely isolated electrically
~Enclose & lock all power supplies to avoid accidental bodily contact