Many employees are exposed to electricity daily in their work environments. It can be very safe as long as employees understand the basic principles of electricity and the safety precautions that must be taken when working around energized lines and equipment. According to NIOSH an average of 411 deaths occurs each year in the workplace due to contact with electrical energy. Electrocutions are the fifth leading cause of death, accounting for 7% of all workplace fatalities. The number of people who believe that normal household current is not lethal or that overhead power lines are insulated and do not pose a hazard is alarming. This presentation discusses the basic principles of electricity and gives specific details on safety precautions that must be taken around high voltage electric equipment and lines.
Understanding the basic principles of electricity deals with these basic definitions.
Voltage - Voltage is the fundamental force of pressure that causes electricity to flow through a conductor. The effective potential difference between any two conductors or between a conductor and ground. Voltages are expressed in nominal values unless otherwise indicated. The nominal voltage of a system or circuit is the value assigned to a system or circuit of a given voltage class for the purpose of convenient designation. Voltage is measured in Volts
Current - Current is the flow of electrons from a source of voltage through a conductor. Current is measured in Amps.
Ground - A ground is a conducting connection, intentional or not, between an electrical circuit or equipment and the earth ground, or to some conducting body that serves in place of a ground.
Conductor - A material, usually in a form of a wire, cable, or bus bar, suitable for carrying an electric current. A conductor does allow electricity to flow readily through it. Examples copper, aluminum, water, human body, etc.
Insulator - Insulating material in a form designed to support a conductor physically and electrically separate it from another conductor or objects. An insulator does not allow electricity to flow readily through it.
Electricity is always looking to travel to the ground and it is constantly seeking the shortest path to ground. It will take the path of least resistance and it may take multiple least resistant paths to ground. Electric shock occurs when the path of least resistance is through the human body. The human body is composed of approximately 80% water and water is a great conductor of electricity.
Electricity travels at the speed of light (186,000 miles per second) and is three to four times hotter than a burning building. (6,000 to 8,000 degrees). Electric arc temperatures can melt steel. When a short circuit occurs or current flow is interrupted, an arc is often created. If the current involved is great enough, these arcs can cause injury or can start a fire. Fires can also be caused by overheating equipment or by conductors carrying too much current.
