Research Of Single-Ended Transient Current Protection Algorithms For EHV Transmission Lines

Modern power system develops the trend of large capacity, long distance, high voltage and interconnected grid, which demands higher transient stability for power system. Clearing the faults rapidly is an effective method to ensure stable operation. Transient Based Protection utilize high-frequency components of fault transient to carry out discrimination, achieve their protective function, with fast response, high accuracy advantages, but also is insensitive to the transition resistance, the system oscillation, TA saturation and other factors. Therefore. Transient Based Protection can improve the performance of protective relaying devices, to solve the inherent defects of the frequency protection, become one of the development directions of power system protective relaying.Transmission line fault-generated high frequency components through the line boundary can suffer a large number of attenuation and reflection, so the detection internal and external fault component are differences, this difference can be realized the fault identification. On the basis of the frequency characteristics of line boundary, this paper was proposed two protection algorithms for EHV transmission lines based on fault transient components. The first is based on improved recursive wavelet transform (IRWT) phase information of the transient protection algorithms:IRWT is used to extract desirable frequency components of fault-induced transient current signals, according the difference of the average frequency of the extracted signals which measured by their phase information, an internal or external fault can be distinguished. The second is a transient protection algorithm based Hilbert's-Huang Transform:Hilbert-Huang Transform method process fault current signal to achieve Hilbert spectrum of the high-frequency components, according to compare the size of instantaneous frequency at the fault-occurred time to determine the internal and external fault.A simulation model of 500 kV extremely high voltage transmission systems are established on the platform of PSCAD/EMTDC. A lot of simulations about different fault conditions such as fault location, fault resistance, fault type, fault inception angle and different...