Digital differential protection technique of transmission line using instantaneous active current: theory, simulation and experiment

Abstract

Current differential protection is widely used as the main protection in UHV/EHV (Ultra/Extra High Voltage) transmission lines with advantages of simple principle, high reliability and inherent phase-selection capacity. However, as the voltage level and line length increase, the performance of the current differential protection is severely restricted by distributed capacity current. Aimed at this problem, a rapid extraction method of single-phase active current is proposed in this paper. The method first uses single PLL (phase-locked loop) to track the phase of the corresponding fundamental voltage. Then the current signal is transformed from the abc static coordinate system to the pq rotating coordinate through transformation matrix. By filtering out the high-frequency AC signal on p axis with low-pass filter, the active current component remaining being in the same direction with voltage phase can be obtained. On this basis, a novel active current differential protection method is proposed, with the advantages of high sensitivity and strong capacity of enduring transition resistance without requirement for the acquisition of line impedance parameters. Finally, the proposed method is tested by a series of dynamic simulations through PSCAD and experiment. The simulation results show that the method has merits of effectiveness, robustness and rapidity.

The Analysis and Solution of Current Differential Protection Maloperation for Transmission Line with High Series Compensation Degree

“…At the same time, it can realize fault simulation, data measurement, relay protection, and other functions. The basic operating principle of the experiment agrees with the dynamic model experiment mentioned in reference [22][23][24][25]. Photographs of some dynamic physical simulation devices are shown in Appendix A.…”

Longitudinal Differential Protection of Power Systems Transmission Lines Using Optical Waveguide

“…There are two types of algorithms for differential protection: those that use phasors [13][14][15][16] and those that use instantaneous values of electrical quantities [17,18].…”

“…A short recapitulation is performed. Of course, all solutions or algorithms are difficult to be implemented without using OPGW [12][13][14][15][16][17][18][19][20][21][22][23]. Figure 1 shows the longitudinal differential protection operating principle.…”

Impedance‐based pilot protection for ultra‐high‐voltage/extra‐high‐voltage transmission lines

“…For years, current differential protection has been demonstrated an effective and successful protection method for transmission lines [1], but the prominent capacitive charging current along the EHV/UHV transmission lines severely degrades its performance [2]. To solve this problem, many methods of compensating capacitive charging current have been presented.…”