Study On The Principle Of Current Instantaneous Trip Protection In Smart Distribution Network

The power system has been developed into high-capacity centralized power generation, trans-regional, super (especially) high-voltage transmission of large-scale Internet systems. With the gradual depletion of fossil fuels and their impact on environmental pollution, increasing energy efficiency, saving energy consumption and improving energy structure have taken measures by many countries. Driven by many factors, the researching focus of the field of global energy turnes to distributed energy systems,such as the distribution of the user with the forms of new energy, the supplying of thermoelectric cooling,and microturbines,etc. Therefore, an economic, efficient and comprehensive new power technology——DG come into being, and become an important research direction of the power system in the new century.This paper first introduces the concept of distributed generation, the main form of classification, the unique advantages, as well as the research status. The works, operation and development prospects of several common power generation technologies (such as: cogeneration, solar power, wind power, micro-gas turbine power generation, biomass power, and ocean energy, geothermal power generation technology, etc.) were briefly introduced.Becaused of DG accessing to distribution network, the size and direction of the short-circuit current in the network is changed. Because of the complex and changing operating mode of the distribution network, the tuning and coordination of original stage current protection become very difficult or even impossible in accordance with the procedures required for setting.This paper theoretical analysis the impact of protection and its action on each section for DG accessing to distribution network.With simulation analysis of MATLAB software appropriate advice and countermeasures for different situations are proposed.The distributed power of the variable short-circuit capacity is simulated by controlling a voltage source in series in the form of a variable impedance.The cumulative distribution function of distributed power output,which following a normal distribution,was fitted by a hyperbolic tangent function. According to the relationship wihtrandom power output and short circuit current, the distribution of the short-circuit current was theoretical analysised. According to the cumulative distribution curve of the short circuit current,a new protection scheme of distribution network was viewed,without impaction of distributed power accessing. The scope of protection of the probability distribution was determined.The correctness of the principle was verified by simulating of PSCAD, which has a certain significance for promotion and application of distributed generation.