A low voltage microgrid protection scheme using digital instrument transformers

Modern power systems have several measurement devices for reliable, safe, and improved operation and control. Due to the high infiltration of inverter-based resources, protecting modern power systems has become challenging. This paper proposes a new protection scheme based on the computation of 'discrepant impedance' using real-time protocol services for data exchange. The sampled values of voltages and currents are transmitted to a central processing unit to implement the protection scheme. With the development of digital instrument transformers (IEC 61869-9), the current and voltage samples are directly interfaced wired or wirelessly to the IEC 61850-9-2 process bus. The proposed protection scheme is validated with grid forming and grid following inverters on Consortium for Electric Reliability Technology Solutions (CERTS) microgrid network using a real-time digital simulator. The protection scheme is independent of the type of energy sources and their control philosophy, operation modes and topology of the microgrid network. The proposed scheme is a centralized protection scheme using IEC 61869-9 digital instrument transformer and uses the IEC 61850-9-2 sampled value protocol for protection. The methodology is tested on a Consortium for Electric Reliability Technology Solutions microgrid using real-time digital simulator. image