Impacts Of Transitent Characteristics Of Transformer On Power System Protection

Instrument Transformer is a vital equipment which is the connection between the power system primary side and secondary side, it helps to acquire the grid voltage and current signals in real-time for system measurement and monitoring, also it play a very important role to the correct operation of relay protection which provides input signals for power system protection devices. In this paper, issues of the voltage transformer transient errors and solutions, current transformer saturation and ways to prevent, the structure and principle of electronic current transformers and other aspects are discussed.Firstly the impact of the short-circuit voltage drop on voltage transformers is analyzed, research was done on the voltage phasor error resulting from the transient characteristics of capacitive voltage transformer and impact on the protection of mainstream algorithms in view of quantitative analysis. Then mathematical model of current transformers is established using the state equation or the transfer function to investigate the principle error and transient response of voltage transformers. Analysis of voltage errors caused by voltage sags and quantitative analysis of its impact on the protection of mainstream algorithms is made in basic principle and MATLAB simulation. In addition, method to the elimination of transformers for transient performance measures was made in this paper. Then current transformer saturation characteristic simulation is analyzed through a system model based on MATLAB simulation primarily including transformer saturation characteristic curve with effect of non-periodic component current and secondary open circuit current. Finally, An introduction of electronic current transformer general structure and detailed analysis of structure and principle of the optical and Hollow coil transformer is made, which respectively discuss the effect of two kinds of electronic current transformers on differential protection and distance protection based on sampled values and vectors; the practical impact factors of two kinds of electronic current transformer performance is analyzed in the end.