Single-Terminal Quantity Based Line Protection for Ring Flexible DC Distribution Grids

Ultra-fast current differential protection with high-sensitivity for HVDC transmission lines

“…In In fact, with f-point distributed randomly and xkf not known in advance, it is impossible to calculate i0diff_r_cal(t+τ0_rf)/i1diff_r_cal(t+τ1_rf ) online. For the convenience of calculation, i0diff_r_cal(t)/i1diff_r_cal(t) is used to approximate i0_f (t)/i1_f (t), and the faulty pole selection method based on mode quantities at r-point is constructed in (13).…”

“…12(c). Since i0diff_r_cal is almost zero before and after the fault occurrence, and i1diff_r_cal rises once the fault occurs, the faulty pole could be easily and reliably selected in 4.70ms based on (13).…”

“…To achieve a short response time under large-current faults, travelling-wave protection and voltage derivative protection are used as dual primary protections [10][11][12]. But these two protection methods are sensitive to transition impedance at fault point and might fail to respond to small-current faults, such as high-resistance faults [13].…”

Single‐pole fault line selection method for MVDC distribution grid based on 0‐mode power

“…In order to the superiority of the method proposed in this paper, the methods [8,14], [19] are selected to compare with the method proposed in this paper.…”

“…According to this characteristic, transient energy is used as the criterion to identify the internal and external faults, and the forward and backward faults are distinguished by the voltage drop positive and negative of the inductor. In [19], the fault characteristics are analysed by using 1-mode and 0-mode network for the ring DC distribution grid with modular multilevel converter (MMC) and voltage source converter (VSC), and a single-ended protection method is proposed by using the difference in initial voltage value of line boundary inductor, which can effectively solve the problem of communication delay caused by the use of double-ended. The protection designed based on the line boundary has a narrow applicability, so it is no longer applicable when there are no obvious boundary conditions in the DC distribution grid.…”