Electrical Safety
L&T SWITCHGEAR
SAFE & SURE
ELECTRICAL SAFETY
E S P SERVICE MANUAL
GENERAL
Electricity is good servant but bad master. It can prove to be very dangerous if circuits are not properly protected. The major fault that appears in electrical network or equipment is termed as short circuit. In short circuit, the supply phase and neutral or earth is short circuited accidentally due to foreign metallic substance coming in contact with phase & neutral or earth or due to overload thereby damaging the insulation resulting in short circuit i.e. directly connected resulting in heavy current flow called "short circuit current". This high current heats up the terminations, switches, plugs & cable due to which temperature rises to such a high degree that it is sufficient to generate sparking which further leads to fire.
PROTECTION OF CIRCUITS : In order to restrict the short circuit currents and also to.cut off or isolate the faulty circuit from electric supply so that high short circuit current is interrupted before fire starts, appropriate protective devices need to be used as given below : Rewirable Fuses : It is strongly recommended that fuse wires of correct current rating should be used. DO NOT INCREASE THE FUSE CAPACITY FOR PREVENTING OR ELIMINATING FREQUENT FUSE BLOW-UPS. It is essential to locate the causes and eliminate the same. Replacing fuse wires of higher capacity may invite troubles in the form of fire & damage to supply system and surroundings. HRC Fuses : High Rupturing Capacity (HRC) fuses are capable of clearing short circuit & arcs. However, they are much more costlier and hence, application is mostly restricted to commercial & industrial wiring or higher capacity loads. MCBs : Miniature Circuit Breakers are gaining increasing prominence in household and distribution wiring in shops & commercial establishments as it effectively forms combination of switch & fuse with specified level of fault clearing capacity. It can be used to protect
SAFE & SURE
ELECTRICAL SAFETY
E S P SERVICE MANUAL
GENERAL
Electricity is good servant but bad master. It can prove to be very dangerous if circuits are not properly protected. The major fault that appears in electrical network or equipment is termed as short circuit. In short circuit, the supply phase and neutral or earth is short circuited accidentally due to foreign metallic substance coming in contact with phase & neutral or earth or due to overload thereby damaging the insulation resulting in short circuit i.e. directly connected resulting in heavy current flow called "short circuit current". This high current heats up the terminations, switches, plugs & cable due to which temperature rises to such a high degree that it is sufficient to generate sparking which further leads to fire.
PROTECTION OF CIRCUITS : In order to restrict the short circuit currents and also to.cut off or isolate the faulty circuit from electric supply so that high short circuit current is interrupted before fire starts, appropriate protective devices need to be used as given below : Rewirable Fuses : It is strongly recommended that fuse wires of correct current rating should be used. DO NOT INCREASE THE FUSE CAPACITY FOR PREVENTING OR ELIMINATING FREQUENT FUSE BLOW-UPS. It is essential to locate the causes and eliminate the same. Replacing fuse wires of higher capacity may invite troubles in the form of fire & damage to supply system and surroundings. HRC Fuses : High Rupturing Capacity (HRC) fuses are capable of clearing short circuit & arcs. However, they are much more costlier and hence, application is mostly restricted to commercial & industrial wiring or higher capacity loads. MCBs : Miniature Circuit Breakers are gaining increasing prominence in household and distribution wiring in shops & commercial establishments as it effectively forms combination of switch & fuse with specified level of fault clearing capacity. It can be used to protect