Cement, Energy and Environment

network by disconnecting it from the disruptive situations. For this purpose, relays, circuit breakers etc are employed. Various types of protective relays are used for automatic protection in response to load changes. The purpose of operating a relay is to trip the circuit breaker; it isolates the network and saves from the risk of damage. One relay cannot protect against all types of hazards. Some of the equipment protected against the risk of damage is described as follows Motor protection against the following risks o Thermal overload, short– circuit current, earth fault etc. o Single phasing/unbalancing o Starting problem/ locked rotor Transformer protection against following risks o Differential protection for multi-phase faults o Restricted earth fault o Over-fluxing protection o Over-current and earth leakage Circuit Breakers The oldest device was a manually operated knife-switch, which isolates the circuit. Then, came the switch fuse unit. It blows off upon the incidence of a fault, but requires replacement. Now, various types of circuit breakers are in use to meet the requirements of a particular situation. , given as follows. Low Voltage (LV) Circuit Breakers o Miniature Circuit Breaker - MCB o Earth Leakage Circuit Breaker - ELCB Description Activity Flow Application Constant speed drive peed Reduction Current trends Power Generation & Utilization Large Consumers of in speed reduction L__________ _, o Molded Case Circuit Breaker - MCCB o Air Circuit Breaker - ACB Medium and High Voltage Circuit Breaker o Oil Circuit Breaker- OCB o Air Blast Circuit Breaker ABCB o Vacuum Circuit Breaker VCB o Gas Circuit Breaker - GCB Currently, modern microprocessor based relays are available for providing total protection against generators, motors, transformers etc. Power System Activity Diagram Following exhibit marks the route of energy flow, starting from power generation to the point of energy utilization. At each of these stages, measures are suggested for improving the conservation of power and achievement of energy efficiency. Improvement -Maintain power quality - Reduce transmission loss -Provide protective switchgear - Reduce distribution loss -Improve motor cfticicncy -Reduce energy loss -Improve motor life '---------'---' 31