Fault Analysis And Relay Coordination Research For Power Network Including Unsymmetrical Railway Power Supply System

Electricity has become the main traction power in railway systems. Constructing electrified railway is the major task of Chinese railway development according to The Middle and Long Term Plan of Chinese Railway Network. Railway electrification system is a three-phase unbalance system. The unbalance of the 220kV transmission network caused by two-phase power supply system is notable serious, and makes it difficulty to apply symmetrical component method, which is widely used in transmission network analysis software nowadays, in fault calculation. It is quite necessary and important to build a fault analysis method, and develop the software package of fault calculation and relay coordination for the complex transmission network including unsymmetrical railway power supply component. The purpose of this paper is to study the fault calculation and coordination problems in the complex network mentioned above, and to fulfill the software package for automation of calculation and relay coordination of the network. The following are the main contributions of this paper:The structure of electrified railway power supply systems is analyzed, and the general fault calculation method of the power supply system which utilizes three-phase transforms as traction transformers is introduced. The fault calculation of the two-phase power supply system is studied in phase domain and sequence domain separately. A method which takes advantage of both phase component method and symmetrical component method to calculate the fault current of the complex transmission network when faults occur in traction system is presented. The method of parameters calculation and measurement of two-phase line and single-phase transformer is also presented.Two models of two-phase power supply system are proposed to analyze the fault using symmetrical component method, and a conclusion is accomplished. The conclusion can be used to simplify the fault calculation method when faults occur on two-phase transmission line.The requirements and the coordination principles of the two-phase transmission lines relay protection are studied. The coordination principles of two typical protection devices applied in JiangXi power grid are presented. The structure, functions and features of the intelligent fault calculation and relay coordination software which is widely used in power network are described. This paper presents the way to develop the special software module to calculate fault current and coordinate relays for the unsymmetrical railway power supply system. This module finally integrated into the software.