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SantoshKumar2997
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During the last decade there has been a steep growht in the demand of electric power in India and a phenomenal increase in the number of consumers of all categoreis, particularly in the agricultural and industrial sectors. The generation and transmission capacities have not kept pace, In general, with the load-demand necessitating the generators to be loaded to their maximum capacity most of the time. Due to insufficient spinning reserves, any emergency outage of major generating unit of the tripping of a tie-line on fault leads to frequency sinking, over-loading and cascade tripping of generators. The low frequency condition is generally accompanied by low voltage unless elaborate arrangements like field forcing, etc. are provided in the generators. This is the further aggravated due to the lowering of transient stability limits particularly where long transmission lines are involved. The system is likely to separate out at an undesirable, into two segments in the generation and load-demand. Frequent operation of the system at low frequency also results in cumulative damage to the generating units, particularly to the low pressure-stage blades of steam turbines and in their ultimate mechanical breakdown.
The possibility of inter-connection breakdown, the dangers of under-frequency operation indicate that properly co-ordinate load-shedding scheme in essential for adequate system protection. Although load shedding involves a deliberate service interruption, something which one would always like to avoid, it is invaluable to system security since it would become effective only when there is no other remedy available to save the system.
The frequency of AC voltage of power supply network is normally maintained constant at the declared level within statutory limits of variation. In conditions of emergency plant outage, excessive overload on the the network, short-circuit in the system etc., a large variation in frequency may occur. Excessive or rapid variation of frequency may cause a variety of damage to generating plant, damage to industrial machinery, burn-out of domestic appliances and dislocation in traffic signalling system, etc.