The Phasor Combination Differential Protection for Scott and V-V Transformers

• Main Author: 劉育志
• Other Authors: Nanming Chen
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/81794834777955698425

碩士 === 國立臺灣科技大學 === 電機工程系 === 87 === The main protection for a general power transformer (over 10MVA) is normally achieved by a differential protection scheme. Due to different phase numbers in the two sides of a specially-connected transformer used in electrified railway systems, a traditional differential protection scheme for a general power transformer cannot be used. Presently, the over-current relay is used as the main protection and an over-voltage relay is the backup. The purpose of this thesis is to design a differential protective scheme for some specially-connection transformers which are the main transformers of the electric railway. Current phasor combination method is applied to it and the design procedure is the same as the differential protection of normal power transformers. The designs are applied to the Scott connection transformers used in Tokaido-Shinkansen and the V-V connection transformers used in TGV in France and ECML in Great Britain. Finally, a scaled down system is implemented in a laboratory to simulate the Scott connection and V-V connection transformers to assure that the protection function can reliably protect them against faults.