The capital investment involved in a power system for the generation,transmission and distribution of electrical power is so great that proper precautions must be taken to ensure that the equipment not only operates as nearly as possible to peak efficiencies ,but also that is protected from accidents.The protective Relaying system is to operate the correct circuit breakers so as to disconnect only the faulty equipment from the system as quickly as possible , thus minimising the trouble and damage caused by faults when they do occur.
The Modern power system is very complex and even though protective equipment's from 4 to 5% of the total cost involved in the system , they play a very important role in the system design for good quality of reliable supply.
The most severe electrical failures in a power system are shut faults which are characterised by increase in system current,reduction in voltage, power factor and frequency.The protective relays do not eliminate the possibility of faults on the system, rather their action starts only after the fault has occurred on the system.it would be ideal if protection could anticipate and prevent faults but this is impossible except where the original cause of a fault creates some effects which can operate a protective relay.So far only one type of relay falls within this category,this is the gas detector relay ( Buchholz relay) used to protect transformers which operates when the oil level in the conservator pipe of transformer is lowered by the accumulation of gas caused by a poor connection or by an incipient breakdown of insulation(Slowly developing fault).
The Modern power system is very complex and even though protective equipment's from 4 to 5% of the total cost involved in the system , they play a very important role in the system design for good quality of reliable supply.
The most severe electrical failures in a power system are shut faults which are characterised by increase in system current,reduction in voltage, power factor and frequency.The protective relays do not eliminate the possibility of faults on the system, rather their action starts only after the fault has occurred on the system.it would be ideal if protection could anticipate and prevent faults but this is impossible except where the original cause of a fault creates some effects which can operate a protective relay.So far only one type of relay falls within this category,this is the gas detector relay ( Buchholz relay) used to protect transformers which operates when the oil level in the conservator pipe of transformer is lowered by the accumulation of gas caused by a poor connection or by an incipient breakdown of insulation(Slowly developing fault).
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