Purpose of POWER System protection
The purpose of any power system is to generate, transmit, and distribute electricity to the consumer in a manner that is safe, reliable, and economical; both in the short and long term. Under normal operating conditions, the currents, voltages, power, and energy associated with such systems are all matched to meet the system’s design requirements with respect to reliability, quality, safety, and economy. To ensure maximum returns on the large or expensive investments in the components which go to make up the power system and to keep the customers satisfied with reliable (i.e., adequate and secure) service, the power system must be kept in operation continuously without major breakdowns and consequently without violating the design limits (because of abnormal currents, voltages, or power). This can be achieved in two ways: (i) Implement a system adopting/using components, which should not fail (i.e., failure-free components) and requires the least or nil maintenance to maintain the adequacy and security of supply. By common sense, implementing such a system is neither economical nor feasible, except for small systems. (ii) Foresee or anticipate any possible/credible effects or failure events that may cause long term shutdown of a system, which in turn may take longer time to bring back the system to its normal course. The main idea is to restrict or minimise the disturbances during such failures or events to a limited area and continue power supply in the balance/unaffected areas. The second approach is the one commonly used in practical power systems. To realise it, special equipment is normally installed to continuously monitor the power system to detect undesired conditions that present a threat to system reliability (adequacy and security) and take (initiate) action to remove the threat from the system with minimal adverse effects (i.e., detect abnormalities that can possibly happen in various sections of a power...
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