Analysis of the cable length impact on the performance of differential and directional protections in multi-terminal VSC-HVDC systems

摘要

VSC-HVDC (Voltage Source Converter - High Voltage Direct Current) transmission systems are highly sensitive to fault occurrences at the DC side. This is because of the high sensitivity of voltage source converters to fault currents. The advent of DC circuit breakers allows the isolation of faults at the DC side of the system, which enables selective protection for multi-terminal systems without turning off of the entire system. However, this type of device has limits as the maximum interruption current. In this way, it is necessary to correctly identify the fault before the fault current exceeds the DC breaker maximum interruption capacity. This paper investigates the time response of the differential and directional current protections, in order to evaluate the maximum current through the circuit breakers at the time the fault is identified. For this purpose, several DC faults considering different cable lengths were simulated using a multi-terminal VSC-HVDC system modeled in EMTDC/PSCAD software.