Simulation Analysis And Comprehensive Evaluation Of Voltage Sag In Distribution Network With Protection Devices

With the rapid development of society,the application of new technology and new process in high-tech industry,especially the access of more sensitive devices,puts forward higher requirements for power quality.These new electrical devices are very sensitive to voltage sags.How to effectively prevent the voltage sag problem has also become the focus of current research.It is very important to evaluate the severity of voltage sag reasonably.This paper evaluates the voltage sag and calculates the sag index by modeling the system and adding the protection device to the conventional distribution network system.In terms of system modeling,this paper uses the PSCAD/EMTP(Electromagnetic Transients Program)program combined with the voltage sag performance of the distribution network to analyze the voltage sag simulation process.: Fuse,circuit breaker and recloser)system modeling.It is hoped that the simulation model is as close to the real component as possible,so that the most accurate voltage sag characteristic analysis can be obtained.Finally,the performance of the established simulation model was tested.In terms of voltage sag evaluation,the voltage sag performance of the distribution network is predicted by random estimation of the voltage sag.Based on the Monte Carlo program implemented in the time domain simulation tool MATLAB/Simulink,and taking into account the impact of the protection devices installed in the power grid,this part mainly discusses the characteristics of the voltage sag caused by the line fault of the distribution network.Finally,the coordination between several different protection devices is analyzed.As expected,proper coordination between protection devices can reduce the impact of voltage sags on end-user equipment.In the calculation of voltage sag index,PQs can be used to evaluate the performance of individual nodes or entire systems.In this paper,two types of power quality indicators(SARFI index,energy index)are obtained and analyzed from random estimation by using time domain simulation tools,they give,respectively,the average number of events and the average interruption duration of each kilovolt ampere served at the low-voltage level over the assessment period.The methods to obtain these indexes are discussed and the influence of protective devices is analyzed.Based on the model established in this paper on the distribution network system with protection devices,and the conclusions obtained from experiments with time-domain simulation tools,the power supply department improves its distribution network,equipment manufacturers improve equipment tolerance and low-voltage users There is a certain guiding significance in reducing economic losses.