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825 Electrical energy management systems (EEMS)
The functions which an EEMS may handle are:
- power sources and loads management
- multi source connection management
- propose load control (load shedding and load shifting)
- bidirectional exchange of information with the DSO
- backup system management by means of electrical energy storage units and power sources
- control the electrical energy flow from and to electrical energy storage units
- monitor the voltage quality
- provide an interface for the end user.
825.2 ARCHITECTURE OF EEMS
In an individual, collective or shared PEI, one or several EEMSs shall monitor and control the operation of loads, all power supplies and storage units.
For collective or shared PEI, this EEMS can be either a central system or the association of the different EEMSs sharing together all the relevant information.
Consumption of each electrical installation forming part of the individual, collective or shared PEI shall be monitored, as well as all local electricity production.
To do so, energy meters, performance measuring and monitoring devices (PMD) or other measuring equipment shall be installed in appropriate/required locations.
826 TECHNICAL ISSUES
826.1.1 – Protection against electric shock
The PEI shall be able to operate in any intended operating mode as defined in Regulation 824.2. According to needs, a PEI can change the operating mode at any time and may come back to the initial operating mode also at any time (for instance, from direct feeding mode to island mode and then back to direct feeding mode).
Protection of persons and properties shall be provided in all operating mode
This is particularly the case for the protection of persons against electric shock when the automatic disconnection of supply is used as a protective measure for all intended operating modes. In this case, the system earthing used for all intended operating modes may differ and may depend on the operating mode.
- In connected mode, without galvanic separation, the PEI remains connected to the public distribution network. Therefore, the system earthing of the PEI shall be the same as that of the public distribution network.
- In island mode, the PEI is disconnected from the public distribution network. Therefore, the system earthing of the PEI may differ from the one used within the public distribution network.
In island mode, where ADS is the protective measure, the PEI shall meet the requirements of Regulation 522.214.171.124.1.
A switching device suitable for isolation according to Chapter 53 shall disconnect all live conductors from the public distribution network.
8126.96.36.199.1 – Earthing arrangement
The earthing arrangement needed for operating the PEI in island mode shall be connected to a suitable earth electrode complying with Regulation 542.2.2. Any connection to the means of earthing derived from the public distribution network need not be disconnected.
Any change of type of system earthing for island mode shall be reversible as operation in this mode can be temporary, and the PEI can then be operated again in connected mode.
When the installation is connected to different sources in parallel, simultaneously accessible exposed-conductive-parts and/or extraneous-conductive-parts shall be connected to the same earthing arrangement individually, in groups or collectively.
8188.8.131.52 – Selection of protective device
Operation of the protective device shall be in accordance with the maximum disconnection times as required by Chapter 41 and the requirements of Regulation 551.2. The selection of protective devices against electric shock shall consider the minimum earth fault current value (between one of the line conductors and PE conductor). The minimum earth fault current value may depend on the operating mode refer to BS7671 A2:2022 Fig 82.9
826.1.3 OUTAGE OF THE PUBLIC NETWORK
When the public network is not energized, prosumers shall operate their private individual PEI in island mode or automatically disconnect all local power supplies. As control devices and protective devices may be operated more frequently than in non PEI, selection of components is recommended to be made according to the increased duty requirements (in terms of electrical and mechanical operations).
826.5 ELECTRIC VEHICLE CHARGING
An electric vehicle (EV) capable of operating as a prosumer represents a particular case of a load and local storage unit. Such a vehicle will not be permanently connected to the PEI.
Electric vehicle charging equipment (see Section 722) for a vehicle operating as a prosumer should be managed by the EEMS as defined in Regulation 825.1.
826.7 TESTING AND VERIFICATION
The validity of test readings taken with a fault loop impedance test instrument may be adversely affected by power converting equipment (such as inverters) within the prosumer’s installation. In such cases an alternative method of determining prospective fault current and earth fault loop impedance shall be used. See Note 1 of Regulation 6184.108.40.206.