Despite signiﬁcant improvements in product safety, electrical injury is still the cause of many fatalities and of considerable morbidity. Electrical injuries (excluding lightning) are responsible for⬎500 deaths per year in the United States. A little more than half of them occur in the workplace and constitute the fourth leading cause of work-related traumatic death.
Electrical injuries can be caused by several factors such as:
1. Touching a live conductor
Faulted electrical equipment constitutes a danger to personnel when they come in contact with such devices. The contributing factor to all these dangers is the aging of the equipment’s insulation, missing ground wire, and/or improper installation. Copper thieves are seriously injured when they try, for commercial reasons, to remove live copper wires.
2. Open neutral
When the neutral of a 240/120 V, single-phase, the 3-wire power distribution system is accidentally open (at the utility’s transformer or at a home’s electrical entrance), under voltages and overvoltages develop that can damage property and injure personnel.
3. Arc flash
When a solid short circuit takes place between electrical conductors, it breaks down the dielectric of the air space between them, and an “Arc flash” develops. The resulting high currents produce extremely high pressures and temperatures and can seriously injure unprotected personnel.
4. Energy stored in magnetic and electric fields
On current interruption, the inductors (magnetic fields) release the energy stored while the capacitors (electric fields) withhold the energy stored. These energies, when not properly harnessed, can cause equipment damage and injury to personnel.
5. Stray voltages
Leakage ground currents are occasionally the cause of serious injuries to swimmers in lakes and pools. They can also adversely affect the behavior of agricultural animals and the operation of field sensors.
6. Lightning strikes
Anyone who is outdoors in the midst of thunder and lightning has no protection. Taking shelter under a tree can perhaps mitigate the catastrophic effects if simple precautions are taken.
7. Improper earthing
Many of the shock cases are reported due to improper earthing such as a metallic part that accidentally becomes energized by contact with an electrical conductor whose insulation has deteriorated. For any electrical installation, proper earthing is a must. The earthing completes the electrical circuit and arranges to trip the faulty circuit by operation of protective equipment such as fuse, MCB, leakage current detector, Earth fault relay, Zero sequence detectors, etc.