Protection method for pole-to-pole short-circuit faults in DC distribution networks based on differential current correlation

When a pole-to-pole short-circuit fault occurs in DC distribution networks, the fault current rises to several times or even tens of times the rated current within milliseconds. This rapid increase results in instantaneous converter lockouts and may lead to system shutdowns. To ensure the continuous operation of DC distribution networks, a fault protection method based on differential current correlation is proposed. The transient characteristics of fault currents are investigated. For internal faults, the differential current is mainly formed by capacitor discharge currents from modular multilevel converters and DC transformers. For external faults, the differential current is primarily composed of discharge currents from line-distributed capacitors. Based on these characteristics, the Pearson correlation coefficient is applied to identify faulted lines by analyzing the correlation between line differential currents and their accumulated difference currents.Simulation results demonstrate that the proposed method can quickly and reliably identify faulted lines. Transient currents from line-distributed capacitors during external faults do not cause misoperation. The method is resistant to noise (30 dB) and synchronization errors (0.3 ms). It also accurately identifies high-resistance faults (100 Ω).