Study On The Relay Protection Scheme Of Combined CO-Phase Power Supply System

A new cophase power supply system of substation is proposed in the thesis-The combined cophase power supply. It replaces the complex balance transformer, however bases on the single-phase transformer, and collocates the right amount of compensation device to realize the cophase power supply technology. At the same time, the original relay protection scheme has changed by reason that changes of main wiring, the occurring of TMT and compensation bus, the different standby mode of ADA. Therefore, it is necessary to study the combined cophase power supply protection scheme.First, the thesis analyzes the structure, the working principle, and the excellent feature of the combined cophase power supply, the thesis introduces the basic structure, the compensation current detection, and the control mode of the compensation phase device (CPD).The cophase power supply is modeled and simulated under PSCAD/EMTDC, and it is proved to be true and feasible.Secondly, for the traction transformer, the inrush current is simulated under the PSCAD/EMTDC. Then the thesis introduces the method of distinguishing the magnetizing inrush and internal fault current, and sets a protection scheme for the transformer. For the CPD, this thesis considers the allocation of the power differential protection and the inverse time over-current protection from the whole CPD part; Then, separately sets a protection scheme for the HMT,TMT, compensation bus, and the ADA; In order to improve the reliability of power supply, this thesis studys on a backup scheme of the cophase power supply, and brings a image of the intelligent substation of the cophase power supply up, moreover, analyzes the feeder protection of the cophase power supply up.Finally, The transformer fault, the influence of variational load to the CPD and the power differential protection are simulated under PSCAD/EMTDC. Then they are proved to be true and feasible.