ELECTRICAL SAFETY MEASURES

As a source of power, electricity is used in all aspects of life. In the home and at work, electricity provides the power for everything from domestic appliances to industrial machines, from office equipment to electric tools. When compared to the potential dangers of machinery and chemical substances, electrical hazards can be easily overlooked. Unfortunately, this neglect often causes serious accidents and loss of property. Many of these accidents can be prevented as they are mainly caused by electricity users who lack basic safety awareness.

This table reviews the industrial accident statistics involving electricity in the past decade.

Sources of electricity

The electricity we used is mainly supplied by local electricity companies, and is connected homes, working places, and other areas, through distribution systems.

Frequency: 50 Hz Voltage: 

Single-phase: 220 Volts (V) alternating current

3-phase: 380 Volts (V) alternating current

The electricity used in our homes and offices is single-phase alternating current, and 3-phase alternating current normally serves the industry.

Electricity principles

Ohm’s Law

A complete electrical circuit is composed of 3 elements: Current, Voltage and Resistance.

Their correlative relationship can be shown by the following formula:

The above formula applies to the human body during an electric shock, provided that the voltage remains constant and there is Resistance (R) in the human body. A reduction in resistance in

the human body will lead to higher electrical currents passing through it, and any injury will be more serious.

Electrical hazards

 Electric shock

Electric shock refers to the electricity passing through the human body, affecting the normal function of the heart, lungs and nervous system. Ventricular fibrillation caused by electricity is the main reason

for death from electric shocks. Electric shocks may indirectly lead to accidents, e.g. falling from heights and bruising due to body trauma etc.

Ventricular fibrillation involves a series of disordered contractions of the heart’s ventricular muscle

fibers, which prevents regular heartbeat. Under normal conditions, the human heart rate is from

around 60 to 100 times per minute. During an electric shock, the heartbeat may increase up to several

hundred times per minute. When the heart cannot sustain such rapid contraction and relaxation, it

may stop beating and cause death.

Burns

During an electric shock, the current passing through the body may lead to burns on the skin,

muscles or internal organs. As electric shocks and burns are closely related, preventative measures

should be considered together.

Fires and explosions

High temperatures caused by currents under abnormal conditions, may result in accidental fires

and explosions. The common causes leading to high temperatures include:

• Overloading of electricity

• Insulator breakdowns or short circuits

• Improper contact of electrical circuit

• Improper maintenance of

electrical appliances or wiring

• Poor ventilation, etc.

If flames, sparks or metallic solutions due to electric arc welding are not controlled, hazardous fires or explosions can occur.

Special process (electric arc welding)

Electric arc welding is commonly used for metallic welding and cutting. The various hazards from

welding or cutting include the following:

Hazards

• Burns

Sparks or hot metal fragments from arc welding or cutting may result in serious burns. Proper

protection is essential.

• Radiation

If proper eye protectors are not used while welding or cutting, radiation or other objects may hurt the

welder.

Safety measures:

Wear proper personal protective equipment, e.g. approved eye protectors, hand shields, leather aprons, leather gloves and safety shoes, etc.

Electric shock

It is dangerous to conduct the arc welding in a wet environment or on rainy days.

Safety measures:

• Avoid electric welding in such conditions.

• Earth the tools and equipment properly.

• Adjust the current required for welding to the minimum amount.

• Add an automatic voltage regulator to reduce the open-circuit

no-load voltage of the transformer output, reducing the chance of getting an electric shock.

• Poisonous fumes and gases Inhalation of poisonous fumes and gases during welding

or cutting may cause serious health problems.

Safety measures:

• Provide adequate ventilation.

• Use exhaust systems to remove poisonous fumes and gases.

Protective measures for prevention of direct electrical contact

The following procedures will prevent the human body from contact with electrical conductors, wiring, electrical sources, etc.

Protective measures

• Insulation

Shield the electrical conductor with an insulator to prevent direct contact

• Obstacles

Place obstacles to prevent any accidental contact with the electrical conductor

• Barriers or enclosures

Create barriers or enclosures that prevent any direct contact with the electrical conductor

• Placing out of reach

This prevents accidental contact with the electrical conductor