Analysis and Experimental Verification of Load Current Switch Based on Molded Case Circuit Breaker for MVDC System

In reference to alternating current (AC) distribution system, frequent load current switching is predictable for system reconfiguration and scheduled maintenance in medium-voltage direct current (MVDC) system. Up to now, without special consideration of the transient load current switching process, direct current circuit breaker (DCCB) is taken as the main guidance for load current switch (LCS) in MVDC system, resulting in common disadvantages of short-mechanical life and high-investment. To find a better solution, a novel LCS based on molded case circuit breaker (MCCB) is proposed in this paper. By discussing similarities and differences between DCCB and LCS, the working principle of LCS and system requirements for LCS are revealed. Then, an LCS based on MCCB (MCCB-LCS) is proposed, with its structure, operating methods, and parameter design methods also demonstrated. Simulation and experiments are carried out to validate the proposed MCCB-LCS. The load current through the line to be disconnected is transferred to other lines within 20ms in simulations, and load current exceeding 2kA is interrupted within 20ms in experiments. Compared with the traditional LCS, MCCB-LCS has the advantage of low cost and compactness.