Study of Upgrading Distribution Feeders from Radial to Normally Closed-Loop Arrangement

• Main Authors: WEI-TZER HUANG, 黃維澤
• Other Authors: TSAI-HSIANG CHEN
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/86671272964445144431

博士 === 國立臺灣科技大學 === 電機工程系 === 93 === This dissertation examines the issues of upgrading distribution feeders from radial to nominally closed loop arrangements. Four types of normally closed loop arrangement will possibly be formed by tying two existing radial feeders at their ends normally. First, two radial feeders fed by a substation transformer to form a typical normally closed loop named as Type I; second, two radial feeders fed by two different substation transformers located at the same distribution substation to form a cross-transformer-type normally closed loop. The latter type is further divided into two subtypes based on whether the tie breaker of the secondary buses of the two transformers is normally closed or open, the tie breaker is normally open named as Type II.1, and the tie breaker is normally closed named as Type II.2; third, two radial feeders are fed by two different transformers located in different substations to form an interconnection-type normally closed loop name as Type III. Because of the difference in these four types of feeder arrangements, the factors affected the upgrading of distribution feeder and the required supporting measures are quite different. Besides, the operating characteristics, the mode of operations, the feasibility, and the reliability are divergent naturally. Accordingly, it is worthy of further study. First of all, four possible feeder arrangements for forming a normally closed loop upgrading from existing radial feeders are proposed, and then the factors that may predominately affect the distribution feeder upgrading are discussed theoretically. Next, the variations of short-circuit capacities along a feeder before and after the distribution feeder upgraded under different parameters and types were evaluated via the derivation of the short-circuit capacities formulas. And the power flows, voltage drops, and loading variations of the substation transformers and the feeders were also discussed before and after the distribution feeder upgraded, as well as the abnormal operations after the distribution feeder upgraded. Additionally, the resistive line loss formulas were derived to analyze the impacts on line loss due to the changing of the structure of distribution feeders; and further, the feasible closed loop feeder arrangements with load transfer, the corresponding operating modes, and the maximum loadings as well as utilization factors of the substation transformers and feeders under normal operation condition were explored here. Finally, to sum up the impacts of distribution feeders upgrading, the required supporting measures have been drawn up. The outcomes are of value to the distribution engineers while planning to upgrade the distribution feeder, and operating and maintaining the closed loop type of feeder arrangement.