The purpose of this document is to provide guidelines for operation of microgrids. Microgrids considered in this document are alternating current (AC) electrical systems with loads and distributed energy resources (DER) at low or medium voltage level. This document does not cover direct current (DC) microgrids.

Microgrids are classified into isolated microgrids and non-isolated microgrids.

Isolated microgrids have no electrical connection to a larger electric power system and operate in island mode only.

Non-isolated microgrids may act as controllable units to the electric power system and can operate in the following two modes:

• grid-connected mode;

• island mode.

The 62898 series is intended to provide guidelines and the basic technical requirements to ensure the security, reliability and stability of microgrids.

IEC TS 62898-2 applies to operation and control of microgrids, including:

• operation modes and mode transfer;

• energy management system (EMS) and control of microgrids;

• communication and monitoring procedures;

• electrical energy storage;

• protection principle covering: principle for non-isolated microgrid, isolated microgrid, anti- islanding, synchronization and reclosing, power quality;

• commissioning, maintenance and test.

NOTE 1 Safety for personnel is outside the scope of this document, and such information is referred to in IEC TC 64 and TC 99 publications.

NOTE 2 Local laws and regulations can overrule the requirements of this document.

NOTE 3 The principles for main types of protections in microgrid, fault analysis for converter type and rotating machines type, protection type selection, general technical requirements, setting value principles and so forth are intended to be developed in IEC TS 62898-3-1 ¹ .