The Study Of General Control On Var And Voltage For The Longnan Power Grid In Gansu

The Longnan network is one of the important parts in the Gansu grid,. As a national major project, the 330kV power transmission project will be constructed and brought into service in 2004. Through the 330kV transmission line between Tianshui and Chengxian and the new 330/220kV interconnecting transformer, the 220kV Longnan network will realize the tight connection with the large Gansu power grid. This paper studies the 330KV power transmission project associated with the features that the interior power flow changes greatly in the different planning year level and change with summer and winter operating modes .This paper carry the study on the reactive power & voltage coordinated control of the 330kV, 220kV and 110kV network with the 330kV Chengxian S/S as the center. This study set the coordinated control rules to make the reactive power flow distributed reasonably, and thus maintain the bus-bar operating voltage of all substation at the ideal level, and improve the power factor of the transmission lines. Furthermore, the active power loss will be reduced to the least so that the network operating will be optimized.The study bases on the four operating conditions of which the Longnan network will be implemented in the year of 2005 and 2010. First, this paper calculates the power flow distribution that including the line charging reactive power and input of the low-voltage shunt reactor in Chengxian S/S. Assumed that the bus voltage of Tianshui S/S and Bikou power plant to be constant, the study count the voltage level of the 330kV and 220kV bus-bar when the 330/220kV transformer in standard tap changer position .In order to set control rules. First the paper use the different four network operating condition as the primary given conditions and set the 330/220kV transformer tap changer position in the standard position, adding the paralleled capacitor bank sets one by one into the network to change the amount of the input reactive power, thus obtained four sets of the 330kV and 220kV bus voltage and the active and reactive power losses changing curves.Then the paper uses the same typical four network operating conditions as the primary given conditions and when adding one set of the parallel capacitor bank, changing the 330/220kV transformer tap changer position step by step to change the transformer ration, through this study methods this paper found out all the optimized combination of the tap changer position and the amount of input reactive power, also obtained four sets of the 330kV, 220kV and HOkV S/S bus voltage and the active and reactive power losses changingcurves.Through analyzing the optimized combination control curve and the network power flow, the paper generalizes the rules as following:The chief measure of coordinative control is inputting shunt reactor in Chengxian S/S in winter time both in the planning year of 2010 & 2005; In summer time in planning year of 2010 the chief measure is to input proper shunt capacitor. At the same time both supplementary with proper tap changer position of the main transformer.