高电压技术2008，Vol.34Issue(5)：966-972,7.
Winding Capacitance Dividing Method for Powerformer
Winding Capacitance Dividing Method for Powerformer
摘要
Abstract
It presents a method which can equivalently arrange the capacitance distribution along with the winding ofthe generator on the terminal and neutral respectively in a reasonable partition, particularly for a type of high-voltagegraded insulated cable wound generator, Powerformer. The winding of the Powerformer adopts graded insulation,which leads to the various cable thicknesses in different portion of the winding, and thus, the uneven capacitancedistribution. The large capacitive currents and large transient outrush currents resulting from the cable consisting ofthe stator winding of Powerformer may cause problems to the generator differential protection. Most of literatures a-vailable in the field of compensated differential protection focus on the charging current compensation for long trans-mission line, instead of for generator. The authors give a method which can be used to compensate the capacitivecurrent wholly to improve the reliability of the differential protection of Powerformer. It is proved that the distribu-ted capacitance can be equivalent as the lump circuit with a capacitance partition coefficient p, and p is proved as aconstant no matter whether the generator experiences the normal operation, external phase(s) fault or internal phase(s) fault. The formula of the partition coefficient is provided and the corresponding equivalent circuit of the Power-former cable to calculate capacitance currents is given. An analysis programming resolving the minimum value of thecoefficient p is written in MATLAB 7. 0/m according to this formula, using the function fmincon() which can workin any type of constraint condition. The program always gets the same global minimum points under the different in-itial values condition which proves our point by mathematical test. With this new approach to winding capacitancedividing method, the protection scheme used for Powerformer can be validated and improved accordingly.关键词
Powerformer/graded insulation/cable capacitance/charging current/differential protection/MATLABKey words
Powerformer/graded insulation/cable capacitance/charging current/differential protection/MATLAB分类
信息技术与安全科学引用本文复制引用
TIAN Qing,LIN Xiang-ning,LI Jian-jian,TAO Yong-hong..Winding Capacitance Dividing Method for Powerformer[J].高电压技术,2008,34(5):966-972,7.基金项目
Project Supported by National Natural Science Foundation of China(50407010). （50407010）
