Novel and simple scheme for Micro-Grid protection by connecting its loads neutral points: A review on Micro-Grid protection techniques

The low fault current phenomena in the standalone Micro-Grid (MG) is a result of electronic interfacing of the MG Distributed Generators (DGs). Due to low fault current phenomena on the standalone MG, there is a difficulty in differentiating between the fault disturbance and the overload conditions. This paper presents a comprehensive survey about the standalone MG protection issues and schemes. All new trends and schemes available and suggested for MG protection during both the grid connected and the standalone modes are described in details. Also, this paper presents a simple technique for solving the problems due to low fault current phenomena in the standalone MG. The proposed technique is implemented by connecting all MG loads neutral points with the MG earthing system neutral line. The proposed technique suppresses the touch voltages at all MG buses. Also, the proposed scheme results in doubling the MG fault current in the standalone mode. Consequently, the MG protection devices can easily detect and differentiate between the fault disturbances and the overload conditions. Also, the proposed technique damps and suppresses the touch voltage not only at fault location but also through all the MG network buses. The most common fault types (single phase to ground and double phase to ground) are analyzed in details. Results proved that, employing the proposed technique able to solve the low fault current and the touch voltages problems from their roots. No additional hardware is required for implementing the new scheme. The proposed technique is very simple and highly economical attractive.