Study On Ground Protection For Resistance Grounding Power System

It is a comprehensive technical and economic problem to neutral groundin g mode of the electric power system. It associates with voltage level, network structure, insulation level, reliability of power supply, protective relaying, electr omagnetic interference and personal safety and has the characteristics of combi ning theoretical research and practical experience. With the increase of power c able in the power grid, small resistance grounding method has been gradually adopted in urban distribution network and became the new development directiThere is a very close relationship between neutral grounding mode and fre quent single-phase earth fault in the power system. To improve the operation o f the system and improve the economic benefit with minimizing the adverse co nsequences, correct understanding and proper handling of such fault is very im portant. When the single-phase grounding fault occurs, no grounding system wi11continue to run; Arc suppression coil grounding system can compensate the capacitive current, inhibits various over-voltage; Small resistance grounding syst em can determine the fault point quickly, circuit breaker tripping immediately.When the single-phase grounding fault occurs, there will be lots of fault c urrent in small resistance grounding system, the protection can act quickly, but zero sequence current protection can be affected by long lines and transition re sistance and so on, it can cause false action, it is necessary to analyze the infl uencing factors of protection and improve the corresponding algorithm. So it h as important meaning and research value to study the ground protection of low resistance grounding system.Today, Offshore wind power is developing rapidly at home and abroad. Th is paper studies single-phase earth fault protection based on the resistance grou nding system of35kV offshore wind. Firstly, the paper analyzes the characteris tics of neutral non-grounding method, resistance grounding method and arc sup pression coil grounding method and evaluates the pros and cons of grounding methods for the characteristics of large-scale cable in35kV offshore wind pow er system, the rationality of the neutral resistance grounding is put forward. Th e paper simulates the characteristics of the short circuit current and zero seque nce current distribution and introduces properties, capacity and access ways of the grounding transformer. Emphatically analyzes grounding protection problem of the35kV system. Zero sequence current protection scheme is improved by analyzing the zero sequence current and zero sequence voltage. Finally, Based on improved zero sequence protection algorithm, reasonable range of resistance value is got by calculating the parameters of the system.