Electricity is a powerful and essential source of energy, but it can cause severe injuries, fires, and even fatalities if not handled properly. Understanding the hazards posed by electricity is crucial for practicing electrical safety.
Figure1.1.2.Danger High Voltage
Here are some of the main hazards associated with electricity:
Electrical Shock.
The most immediate and dangerous hazard of electricity is electrical shock. When a person comes into contact with an electrical voltage, current can pass through their body, causing electrical shock.
Roughly speaking, the greater the current, the more severe the shock. High voltage presents more danger than lower voltages, but even normal household voltage (120 V AC) can cause severe shock or even death.
Electrical Fires.
Electrical malfunctions can generate heat and sparks, leading to electrical fires. Faulty wiring, overloaded circuits, damaged electrical cords, and short circuits are common causes of electrical fires. These fires can quickly spread and pose a significant risk to property and life. The combination of electricity and flammable materials increases the likelihood of a fire and makes it more challenging to extinguish.
Arc Flash and Arc Blast.
Arc flash refers to the release of intense heat, light, and energy that occurs during an electrical fault or short circuit. It is characterized by a sudden and violent discharge of electrical energy through the air. The arc flash generates extremely high temperatures, often exceeding 35,000 degrees Fahrenheit (19,400 degrees Celsius). The intense heat emitted during an arc flash can cause severe burns to anyone in its vicinity. Additionally, the arc flash produces a bright flash of light, which can lead to temporary or permanent vision impairment.
Arc blast, on the other hand, refers to the high-pressure shockwave produced by the rapid expansion of air during an arc flash. The rapid expansion of these vapors creates a blast wave that can cause significant physical damage. Arc blasts can result in powerful pressure waves, similar to those generated by an explosion, which can cause injuries, such as concussions, fractures, hearing loss, and even fatalities. The arc blast can propel debris, molten metal, and hot gases, further exacerbating the risk to individuals in the vicinity.
Electrical Burns.
Electrical burns occur when electric current passes through the body, generating heat. These burns can be internal or external, depending on the path the electricity takes. Electrical burns can cause extensive tissue damage and may require specialized medical treatment. The severity of electrical burns depends on the voltage, current, duration of contact, and the body’s resistance.
Electrocution.
In the most severe cases, electric shocks can lead to electrocution, resulting in death. High-voltage shocks can cause cardiac arrest, severe internal injuries, and other life-threatening conditions. Contact with overhead power lines, unauthorized access to electrical panels or equipment, and improper handling of live wires are some situations that can lead to fatal accidents.
Effects of Electrical Current on the Human Body.
Electrical shock occurs when current passes through the body. The severity of the shock depends on the current’s magnitude, the duration, the contact area, and the path taken by the current through the body.
The shock current received obeys [provisional cross-reference: ohms-law], so high voltages are always more dangerous. But your body resistance is equally important. Body resistance with dry skin may be above 100,000 ohms, However, if the skin is wet or broken, the body’s resistance decreases to a few thousand ohms.
Current
Reaction 1 Second contact
< 1 mA
Generally not perceptible.
1 mA
Threshold of feeling, tingling sensation.
3 mA
Painful shock. Average individual can let go.
5 mA
Accepted as maximum harmless current. Strong involuntary reactions may cause indirect accidents.
6–25 mA
Beginning of sustained muscular contraction. ("Can’t let go" current.)
9–30 mA
Lung paralysis, Respiratory arrest ‐ usually temporary, but death is possible.
50 mA
Possible ventricular fibrillation. (heart dysfunction, usually fatal.)
100–300 mA
Certain ventricular fibrillation, fatal.
1–4 Amps
Heart paralysis, severe burns. Muscular contraction and nerve damage occur; death is likely.
