Study Of500kv Transformer Neutral Point Of Adding Small Reactance

In recent years, with the rapid development of Guangdong power grid installed capacityand voltage levels network construction,500kV network structure is greatly enhanced, thePearl River Delta region has basically formed a structure of double loop outside the ringnetwork. The strengthening of power network structure to meet the load growth ofGuangdong power grid reliable supply and demand, but also brought the problem of powersystem short circuit capacity. Due to the power grid structure to strengthen,500kVtransformer autotransformer and other reasons, part of the500kV substation appearsingle-phase short-circuit current is higher than the three-phase short-circuit currentphenomenon, become one of the dominant factors restrict the operation and development ofpower grid, to control the short-circuit current level of the growth phase. At present,Guangdong power grid mainly through500kV substation power supply way reducesingle-phase short circuit current, but the power supply will reduce the overall power systemstability and reliability, improves the safety of power grid operation risk.This paper first introduces the structure characteristics of Guangdong power grid,pointed out that the Guangdong grid load concentration, grid structure is increasingly huge,220kV single-phase short-circuit current500kV substation is generally higher than the levelof short-circuit current of three-phase, and increased year by year, severely restrict theoperation and development of power system stability. The way of grounding via small reactorof transformer neutral point can effectively reduce the short-circuit current, can improve theoperation reliability of power grid security500kV substation using network power supplymode, and can promote the industrial frequency transformer neutral point overvoltage,operation overvoltage also declined substantially, from and reduce its insulation level, reducethe cost of equipment. Introduce the domestic provincial power grid in500kV maintransformer neutral point of adding small reactance of successful application cases.Analyzes the necessity of adding small reactance transformer neutral point, short circuitcurrent in the connection and power supply mode of Guangdong power grid were calculated,and compared the single-phase and three-phase short circuit current, the suitability evaluationand classification of Guangdong power grid500kV substation with low reactance grounding,calculation of short circuit current and500kV substation of each category of adding smallreactance. According to the analysis of short circuit current of Guangdong, existing500kVstation transmission capacity, power flow and N-1results, combined with analysis of thevision of grid development, Guangdong power grid500kV main transformer neutral point to add small reactance is Hengli station, Guancheng station, in station, Baoan station, the stationa total of5substations, and analysis of Hengli station and Xiangshan station main transformerwith small reactance limit single-phase short-circuit current effect is the most obvious.This paper introduces the500kV main transformer neutral point of adding smallreactance setting mode is divided into two kinds, one is full of main transformer station areinstalled, is part of the two main drag. Through calculation and analysis, restriction and in4main drag a small reactance limits the effect of single-phase short-circuit current is better thanthat of only a small part of the main drag of reactance at. Therefore, by reducing theshort-circuit current effect and economic benefit into consideration, suggested in station maintransformer neutral point, Baoan station main transformer, Guancheng station maintransformer and Xiangshan station three sets of main transformer neutral point are equippedwith small reactance.Then, the Hengli station, station, in station, station of Baoan City, Xiangshan station wasanalyzed and calculated5substations with small reactance capacity calculation of differentsizes, the reactance value of single-phase, two-phase and three-phase short circuit current canbe reduced, through economic and technical considerations, recommend Hengli station ofsmall reactance main drag. All15Ω, Guancheng station of small reactance are taken15Ω,Xiangshan station of small reactance are taken10Ω, city station of small reactance are taken10Ω, Baoan station of small reactance are taking.A comprehensive analysis of the500kV main transformer neutral point of adding smallreactance scheme, the prediction of small reactance recommended value added5substations,operation mode of Guangdong power grid than before installation has been optimized, theshort circuit current decreases obviously. In addition, according to the comprehensive analysisand the adaptability of the reactor installation scheme of analysis result, propose5500kVsubstation installation of small reactance of the ideal time, the Fragrance Hill Station install inthe summer of2010, Hengli station, in station and Baoan station recommends installationbefore the end of2010, Guancheng station install in the summer of2011before.The short-circuit current of5500kV substations based on different operation mode,analysis and calculation of neutral point grounding current and contact potential differenceand step potential difference, and chooses the transformer neutral point and the groundmounted in series without isolating switch between small reactor, only installed wiring way ofgrounding switch. According to the equipment insulation level and the specific localconditions, selected the66kV reactor,66kV grounding switch,66kV Zinc Oxide arrester models and parameters.Finally, make a, two and civil implementation scheme of5500kV transformersubstations with small reactance of the neutral point, and further demonstrates the feasibilityand suitability of adding small reactance.