*Article* **An Adaptive Protection for Radial AC Microgrid Using IEC 61850 Communication Standard: Algorithm Proposal Using O** ffl**ine Simulations**

## **Aushiq Ali Memon \* and Kimmo Kauhaniemi**

School of Technology and Innovations, University of Vaasa, Wol ffintie 34, FI-65200 Vaasa, Finland; Kimmo.Kauhaniemi@univaasa.fi

**\*** Correspondence: aushiq.memon@univaasa.fi or aushiq\_37@yahoo.com; Tel.: +358-414-744-093

Received: 23 August 2020; Accepted: 9 October 2020; Published: 13 October 2020

**Abstract:** The IEC 61850 communication standard is getting popular for application in electric power substation automation. This paper focuses on the potential application of the IEC 61850 generic object-oriented substation event (GOOSE) protocol in the AC microgrid for adaptive protection. The focus of the paper is to utilize the existing low-voltage ride through characteristic of distributed generators (DGs) with a reactive power supply during faults and communication between intelligent electronic devices (IEDs) at di fferent locations for adaptive overcurrent protection. The adaptive overcurrent IEDs detect the faults with two di fferent preplanned settings groups: lower settings for the islanded mode and higher settings for the grid-connected mode considering limited fault contributions from the converter-based DGs. Setting groups are changed to lower values quickly using the circuit breaker status signal (XCBR) after loss-of-mains, loss-of-DG or islanding is detected. The methods of fault detection and isolation for two di fferent kinds of communication-based IEDs (adaptive/nonadaptive) are explained for three-phase faults at two di fferent locations. The communication-based IEDs take decisions in a decentralized manner, using information about the circuit breaker status, fault detection and current magnitude comparison signals obtained from other IEDs. However, the developed algorithm can also be implemented with the centralized system. An adaptive overcurrent protection algorithm was evaluated with PSCAD (Power Systems Computer Aided Design) simulations, and results were found to be e ffective for the considered fault cases.

**Keywords:** AC microgrid; adaptive protection; IEC 61850 GOOSE protocol; substation automation
