prEN IEC 63552:2025

This International Standard applies to switching device for islanding, hereafter referred to as SDFI, for household and similar uses, primarily intended to be used for energy efficiency (EE) purposes with local production and/or storage of energy.
SDFI are intended to be installed in low voltage prosumer electrical installations (PEI) able to operate in island mode as defined in IEC 60364-8-82, so called islandable PEI.
SDFI are used to disconnect the PEI from the grid to allow operating the PEI in island mode and further reconnect the PEI to the grid.
They are intended to be used in islandable PEI which operate:
– in direct feeding mode and island mode (delivering the electrical energy to current-using equipment of the PEI);
– and in reverse feeding mode to the grid (delivering the electrical energy to the grid).
NOTE 1 Switching of a PEI to island mode can be subject to local regulations (grid codes) or to specific agreement with system operators.
SDFI are part of the electrical installation.
This document applies to SDFI for operation in AC single or multiphase main circuits with rated voltages not exceeding 440 V AC, frequencies of 50 Hz, 60 Hz or 50/60 Hz. They are intended to be used in installations with prospective short circuit currents not exceeding 25 000 A.
NOTE 2 DC operations are not covered by this edition and are kept under consideration for a future revision of this document.
The SDFI is composed at least of one switching unit (SU) and a control unit (CU) to monitor its switching operations from grid connected to island mode and reverse wise.
The SDFI can be provided with a communication interface for exchange with external systems such as the CEM (Customer Energy Manager).
NOTE 3 See IEC 63402 series for CEM standards, under development.
According to the intended use, the SDFI can be interlocked with a system referencing conductor switching device (SRCSD) or it can be integrated with a SRCSD in a single unit.
NOTE 4 See IEC 63445 for SRCSD standard.
NOTE 5 According to its intended use, the SDFI can also be used as an interface switch with the interface protection (integrated or not). See 3.20 and 3.21.
SDFI are intended for use in circuits where protection against electrical shock and overcurrent is provided according to installation rules for low voltage electrical installations , unless the SDFI already contains such protective function. SDFI are not requested to provide isolation function and overcurrent protection according to IEC 60364-8-82. However, the isolation function can be provided by a SDFI fulfilling the requirements of the relevant product standards.
SDFI are normally installed by instructed persons (IEC 60050-195:2021, 195-04-02) or skilled persons (IEC 60050-195:2021, 195-04-01). They are normally used by ordinary persons (IEC 60005-195:2021, 195-04-03) and do not require maintenance.
It is important to note that the main overcurrent protective device of installations cannot be used as a SDFI in single dwellings or similar islandable PEI (see Annex D.5 of IEC 60364-8-82:2022)