Line current differential (87L) protection schemes face extra challenges compared with other forms of differential protection, in addition to the traditional requirements of sensitivity, speed, and immunity to current transformer saturation. Some of these challenges include data communication, alignment, and security; line charging current; and limited communications bandwidth. To address these...

With the rapid development of wind energy, relay protection for large-scale wind farms has been attracting some researchers, due to the absence of standards. Based on the large-scale doubly fed induction generator (DFIG)-based wind farms located in Gansu Province, China, this paper studies the differential protection for the outgoing power transformer of large-scale DFIG-based wind farms. Accor...

This paper proposes three probability models to assess the impact of communication delays and bit errors on differential protection. First, the mechanism of relay protection malfunction caused by communication delays and bit errors is introduced. In general, a channel’s consistent delay or bit error results in refuse-operations, while a channel’s inconsistent delay normally causes false trips. ...

This paper presents an improvement of digital differential relay reliability for protecting a large power transfer is discussed. First, the Fourier sine and cosine coefficients required for fundamental, second third and fifth harmonies determination have been calculated using rectangular transfer technique. Then, these harmonics have been used in harmonics restrain and blocking techniques used ...

This paper describes the application of the p-q power theory to the differential protection of power transformers. The information provided by the harmonic content of the differential active and reactive power components is used to detect winding insulation failures and to distinguish them from magnetizing inrush current transients. A variety of test cases is presented in the paper, demonstrati...

Energization of a transformer results in sudden flow of current which is an effect of core magnetization. This current will be dominated by the presence of second harmonic, which in turn is used to segregate fault and inrush current, thus guaranteeing proper operation of the relay. This additional security in the relay sometimes obstructs or delays differential protection in a specific scenario...

Original scientific paper In this paper, the necessity of the protective relay of the micro-grid is described as the anti-islanding protection and Low Voltage Ride Through (LVRT), and the fault characteristics of the renewable energy sources are analysed. The applicability of over-current protection, distance protection, differential protection, pilot protection, voltage protection and frequenc...

In this work, a new approach applied to digital differential protection relay for a large power transformer is presented. First, the Fourier sine and cosine coefficients required for fundamental, second, third and fifth harmonic extraction have been determined using rectangular transfer technique. Then, these harmonics have been used in harmonics restrain and blocking techniques applied to diff...