Systematic Approach to HVDC Circuit Breaker Sizing

High-voltage direct current (HVDC) grids can be protected by HVDC circuit breakers (DCCB) to selectively clear DC side faults and assure continuous operation of the healthy parts in the grid. Line inductors in series with DCCBs are essential to reduce the rate of rise of the fault current and to slow down the voltage decline in the healthy parts of the grid. The line inductor value and DCCB requirements, i.e., operating time, current interruption capability, and absorbed energy, are dependent on the expected functional requirements of the grid. In this paper, three different categories of functional requirements, termed as HVDC grid fault-ride-through scenarios, have been defined. Based on these definitions, DCCB and line inductor parameters are determined in a systematic manner. Furthermore, a visual approach to DCCB operational characteristics, represented by DCCB operational graphs, is proposed to determine the suitable line inductor value, DCCB operating time, and interruption capability requirements given grid limitations, i.e., maximum current and energy, and/or required fault-ride-through scenario. The proposed method illustrates graphically the interdependence between the DCCB parameters and the line inductor value, and shows high dependence of the main DCCB parameters and the line inductor value on the fault-ride-through requirements of the converters during DC faults.