Research On The New Line Distance Protection Based On Time Domain Full Waveform

Distance protetaion is widely used in high-voltage systems,increasing the distance protection performance is of great significance to ensure the safe and stable operation of the power system.Traditional distance protection has two major problems: low reliability of the protection scheme caused by the electromagnetic saturation of electromagnetic current transducer and low-speed action performance caused by the amount of power frequency protection.With the development of the power system,many problems that traditional distance protection cannot solve have been exposed.Therefore,it is necessary to develop a fast and reliable protection scheme that can adapt to development.However,due to the transmission characteristics of the electromagnetic current transformers and the protection algorithm based on the power frequency,it is impossible to fundamentally solve the problem.In response to the above problems,this topic puts forward a new distance protection scheme based on the use of optical voltage transformer and optical current transformer,making use of the fault full-waveform information based on the instantaneous sampling values of the voltage and current.First of all,this paper analyses the differential influence of electromagnetic current transformer and optical current transformer on traditional distance protection.The results show that:the saturation of the iron core of the electromagnetic current transformer can easily cause failure protection in the protected area and reduce the reliability;after the optical current transformer replaces the electromagnetic current transformer,the optical current transformer has no magnetic saturation,which improves the reliability of the protection and lays the foundation for new distance protection.Then,This topic puts forward a kind of differential protection algorithm based on the time domain full waveform proposed to improve the reliability and quickness of protection.The protection algorithm makes full use of the full waveform information of the fault voltage and current,and uses instantaneous sampling values to achieve fast operation.Aiming at the existing problems of the algorithm of differential equation,a corresponding optimization method was proposed to improve the reliability of protection.Under the premise of ensuring that the out-of-zone fault does not operate,adjusting the value of the time window can effectively improve the speed of action of the protection.Finally,the factors that affect the time domain full waveform distance protection are studied and the reliability of the protection scheme is further improved.This paper analyzes the influence of the three factors on the protection scheme including distributed capacitance,grounding resistance and assist current,and proposes corresponding solutions.The simulation results show that: when the failure occurred out of the area,the protection has good selectivity,and there is no transient overreach;when the failure occurred in the area,the protection has high sensitivity,strong resistance to transition resistance,and good quick motion.The correctness and superiority of the time-domain full-waveform distance protection are proved.Time-domain full-waveform distance protection is a new type of reliable and rapid distance protection scheme,which can effectively improve the reliability and quickness of line distance protection.It can adapt to the development of modern smart grids,and meet the new requirements for distance protection of smart grids.It plays a positive role in ensuring the safe and stable operation of high-voltage,high-capacity smart grids.