article-new_ehow_images_a07_5e_o0_hazards-associated-electromagnetic-field-1.1-800x800ELECTRICITY HAS been one of the greatest benefits to the mankind, it has contributed to all major developments that we enjoy today. At the same time electricity can also be one of the most dangerous risk to our health and safety. Yes as we all know electricity can kill…!! Hundreds of people die each year in Pakistan due to electrocution related accidents, the situation becomes worst during monsoon season and most of the casualties occur in this period. In US alone average 400 peoples die from electrocution and 4400 are injured each year because of domestic electrical shocks. The casualties due to fire related incidents are far beyond the above figure. According to the 17th edition of IEEE wiring regulations the accepted lethal level of shock current through a person is only 50 milli ampere (A). A common misconception is that larger voltages are more dangerous than the smaller ones, however this is not quite true. The danger to living things comes not from the voltage but rather through the current flowing between the two points, it a common observation that we see birds sitting on high voltage lines remains safe and off course they will continue to enjoy unless their wing touches another wire within the vicinity. When close loop is formed current flows due to potential difference and the bird is burnt into ashes.

The mechanism of electrocution is complex and vary distinctively between man, woman and children. The amount of current where one could not be able to let go himself is called cut-off value or “let-go current”, for women it is typically 5 to 7mA whereas for men it is 7 to 9mA, this off course dependent on the muscle mass of the individual. Generaly for limb contact the electric shocks of 1- 5mA is the level of perception, 10mA is the level where pain and burns are received and at 100mA severe muscular contraction and ventricular fibrillation occurs. Current from 100- 300mA are the limits where finally victim is posed to electrocution and will continue until the onset of rigor mortis. So how to tackle this Mr. Invisible…. or Miss Bijlli…!! Remember electricity is a good servant but bad master.

Engr Saud KhanAfter the independence of Pakistan, Electricity Rules, 1937 came into force to the whole Pakistan and remain applicable for long period, in current situation electricity matters are under the umbrella of NEPRA. According to NEPRA Regulations of generation, transmission and distribution of electric power Act 1997 read along with Licensing (Distribution) Rules, 1999 it is the responsibility of Licensee/ Distribution companies (DISCOs) to ensure safe dispatch of electricity to the consumer. The electric inspector from the distribution company should inspect the wiring not only for new connections but also conduct surveillance within the jurisdiction to identify any serious public safety related issue. Licensed distribution company must ensure that all electric supply lines and apparatus, belonging to them or under their control are maintained in a safe condition electrically and mechanically and shall take due precautions to avoid danger arising from such supply lines or apparatus. Incoming service line on consumer premises which are easily accessible should also be so insulated and protected by the distribution company as to be secure under all ordinary conditions.

The electricity consumer should also be aware of his responsibility since the outgoing service mains after the electric energy meter comes directly under the control of consumer. The consumer is responsible to monitor and implement safety and security standards within his own premises. The major hazards associated with electricity are electrical shock and fire. The safety and security objectives can be achieved by adopting the following measures.

1. Avoid touching with energized electrical circuits. Never try to rectify problem yourself in a live circuit or apparatus, always call authorized person or competent technician to look into the matter.

2. No matter how small is the electrical installation, it should be designed and installed by authorized electrical contractor. The installation must be inspected and certified by an Electrical Inspector of concern sub division.

3. Install protection devices that are designed to automatically limit or shut off the flow of electricity in the event of any fault in the wiring system. Fuses and circuit breakers are two good examples, they prevent over heating of wires and components that might otherwise create safety hazards.

4.  Remember the location and how to perform shutoff switches or circuit breaker panels. Operate these manual devices to turnoff the equipment in case of fire or electrocution.

5. Minimize the potential for chemical spills or water near electrical supplies.

6.  Fire extinguishers of type Class-E should be provided and maintained by the owner to meet with any fire related incident.

7.  Protective earthing/grounding system shall be installed by the consumer and checked by authorized representative of the distribution company.

8.  Always use three-prong plugs, the third prong provides a path to ground that helps prevent the buildup of voltages that may result in an electrical shock. Suppose that metal casing/ enclosing of electric apparatus comes with live wire then current will flow through ground wire and the main breaker will trip.

9.  It is preferable to install Residual Current Device (RCD) instead of Earth Leakage Circuit Breaker (ELCB) both are designed to protect human body against the risk of shock in the event of a current flow to the earth. In areas where earth resistance is high the risk exists because the current that flows will not be enough to trip the circuit breaker, in such situation RCD and ELCB offers additional protection. They are sensitive enough to detect even tiny amounts of current present in faulty metal electrical equipment.

10.In addition to the electrical shock hazards sparks from electrical equipment can serve as an ignition source for flammable or explosive vapors. Therefore in areas where volatile flammable materials are used, motor driven electrical equipment should be equipped with non-sparking induction motors or air motors. Lamps, switches should be of explosion proof type and other electrical apparatus must confirm standards laid down for intrinsic safety.

The writer is Electrical Engineer in the KANUPP, Karachi.


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