Amendment A1 IS10101:2020 was published by NSAI in September 2024. The amended standard is now referred to as IS10101:2020+A1:2024. The main changes in IS10101:2020+A1:2024 are listed below:
- Part 718: 'Communal Facilities and Workplaces' – This a new section in Chapter 7;
- Part 722: 'Supply of Electric Vehicle' – several changes;
- Annex 8: 'Energy Efficiency' has been changed to 'Chapter 8 Energy Efficiency' with a new section on Prosumers Electrical installations.
Other changes include minor modification to a number of clauses which are listed on the NSAI website: https://www.nsai.ie
This article, the second of three, deals with Chapter 8 energy efficiency including prosumers' electrical installations. Changes to Parts 718 and 722 were covered in the July/August issue.
Amendment A1 has seen the replacement of 'Annex 8 Energy Efficiency' with a new 'Chapter 8 – Energy Efficiency'. The new Chapter 8 comprises two main parts: 8.1 – Energy efficiency and 8.82 – Prosumer's Electrical Installations. Each of these two main parts has associated Annexes which account for more than 40% of Chapter 8.
Figure1: Consumer versus Prosumer Installation
Figure 1 above shows the fundamental difference between a 'consumer' shown as the dwelling on the left and a 'prosumer' on the right. Both installations are supplied at LV from the grid via underground services (1) terminating in the DSO (Distribution System Operator i.e. ESB) meter cabinet and feeding onto the customer’s consumer unit (2). The dwelling on the right also has solar PV Panels (3) and is therefore both a producer and a consumer ie, a prosumer.
8.1 – Functional aspects – energy efficiency
Part 8.1 outlines requirements and recommendation in relation to designing for energy efficiency in electrical installations in a similar way to how chapters 3 to 7 covered other aspects such as safety, capacity and resilience. The requirements of Chapter 8 must not conflict with the requirements of those earlier chapters. It is applicable for both new and existing facilities and should be implemented throughout the life cycle of the facility.
Part 8.1 is effectively an updated and expanded version of what was originally in Annex 8. It is broken up into 9 sections including topics such as sectors of activities; design requirements and recommendations; determination of the zones, usages and meshes; energy efficiency and load management system; maintenance and enhancement of the performance of the installation and parameters for implementation of efficiency measures.
The primary objective is to optimise the use of electrical energy by minimising energy losses, using electricity at the right time and at the lowest cost and maintaining the performance throughout the lifetime of the installation. The standard defines six classes of electrical installation energy efficiency from EE0 to EE5 as shown in Figure 2 below.
Figure 2: Electrical Installation Energy Efficiency Classes EE0 to EE5.
Part 8.1 also has two associated annexes 8.1A and 8.1B. Annex 8.1A – 'Determination of Transformer & MDB Location using the Barycentre Method' is similar to the previous version. Annex 8.1B 'Method to Assess the Energy Efficiency of an Electric Installation' provides multiple formulae throughout for this purpose.
The objective of some of the calculations and the criteria given in the tables is in some cases vague or open to interpretation. It is worth noting that this Annex is classified as 'normative' meaning it effectively forms part of the standard and must be complied with.
Carrying out an assessment of the energy efficiency of an electric installation using the prescribed methodology will, in my view, necessitate the development of dedicated software.
PEI Concept (8.82.5)
A prosumer's electrical Installation (PEI) is a set of electrical equipment having the following functions:
- Supply – typically a connection to the DSOs LV system,
- Local generators eg, PV system, wind turbines and engine powered generator
- Electrical energy storage system e.g. a battery
- Distribution system e.g. distribution board and wiring systems
- Consumption i.e. loads such as e.g. lighting, power and heating
- Electrical Energy Management System (EEMS)
Figure 3 below shows an example of a prosumer's electrical installation with a.c. electrical distribution within the PEI. This is based on Figure 8.82.1.in the standard. The ac wiring is shown as black lines, dc as blue lines and EEMS wiring as red dashed lines.
Figure 3: Example of a Prosumer's Electrical Installation (ac only).
- DSO network / Transformer
- Electrical Vehicle – V2G
- Electric Heater
- Domestic Appliances
- Lighting
- PC & other devices
- EEM System
- Battery and Rectifier
- Solar PV & inverter
- Wind turbine & inverter
- Diesel generator & Grid PD
- DSO POC / Cut out
- Prosumer electrical installation
- Local consumption
- Local generation
- EEM System signals
Types of PEI (8.82.6)
Section 8.82.6 is titled 'Types of PEI' but mainly focusses on island mode operation. It opens up by saying there are different types of PEI including: Grid Connected PEI; Islandable PEI – Systems connected to the grid and Stand-alone PEI – Systems not connected to the grid.
In grid-connected mode the PEI operates while connected to the utility grid. Energy can flow bi-directionally i.e. it will import when the PEI's energy demand exceeds local generation capacity and will export when it generates surplus energy.
The use of locally generated energy is maximised so as to reduce reliance on the grid during peak demand periods when tariffs are typically higher. This generally necessitates the use batteries to balance supply and demand. It prioritises on-site consumption over exporting energy to the grid.
In Island Mode the PEI operates independently of the utility grid during planned or unplanned disconnections. The PEI must have sufficient local energy generation and/or storage to meet the installation's demand or have load shedding facilities in place to reduce demand to match supply capacity.
Island mode can also be used for back-up power supply during grid outages. It necessitates the use of battery storage and usually standby generators. Provisions must be in place for safe transition to and from island mode. This is discussed throughout Section 8.82.6.
Islandable PEI – Earthing (8.82.6)
This section introduces the concept of islandable PEIs and states that these must have a (i) 'switching device for islanding' (SDFI) and (ii) a 'system referencing conductor switching device'.
There is no acronym suggested for the latter. If there were to be one it would be RCSD. It is basically a neutral earthing switch for the PEI when in island mode. Effectively you cannot have one without the other so, it is easier to refer to the combined unit as 'an island mode switch'. This can be manual or automatic and operated locally or remotely.
The SDFI and RCSD elements must be electrically and / or mechanically interlocked so that the two switches cannot be simultaneously closed. In its simplest form an island mode switch could be a normal I-O-II three position manual load transfer switch using double pole for single phase installations and four pole for three phase installations. The live conductors would be wired through the position 'I' side while the neutral and earth of the PEI would be wired through the position 'II' side.
So in position 'I' the utility supply switch is closed and the neutral earth contact is open ie, the systems is in 'Grid Connected' mode. In position 'II' the utility supply is open and the neutral earth contact is closed ie, the system is in 'island' mode. Similar arrangements can be achieved using contactors or motorised circuit breakers with appropriate mechanical and electrical interlocks
Unfortunately, the diagrams in the Standard are quite confusing. For example, Figure 8.82.4 provides an example of an islandable PEI architecture showing the interlock between SDFI and RCSD/neutral earth switch. However it is a single line diagram and does not show how the neutral of the utility supply is connected to earth.
Numerous other examples of Island mode switching are provided in the diagrams in Section 8.82.6. While these are multi-line drawings the switchgear devices are represented as boxes which again lack clarity. Annex 8.82D also provides diagrams for Island mode switching for dwellings. Unfortunately these are also single line diagrams and do not explain the requirements very well.
Figure 4 below is a simplified multi-line diagram showing a single phase PEI with the island mode switch as described above. It is loosely based on figures 8.82.5 and 8.82D.5 in the Standard where the PEI operates in TN-C-S in grid-connected mode and becomes TN-S in island mode.
Figure 4: Typical Island Mode Earthing Arrangement PEI.
The following is the legend to the diagram.
- DSO network/transformer
- DSO POC/Cut out with neutral earth terminal
- DSO Meter
- Main protective conductor
- Earth conductor
- Earth electrode
- Solar PV
- Solar PCE/inverter with neutral earth terminal
- Battery
- Customers main distribution board with items 11-14
- Main breaker – double pole
- Island mode switch including two-pole SDFI and one-pole RCSD
- Solar input RCBO 100mA type B
- Load protective devices
- Load shed contactor for non-essential load
- Essential load fed from RCBO
- Essential load fed from MCB
- Non-essential load fed from RCBO
Author: Brendan Dervan is the author of 'The Wiring Rules in Ireland, An Illustrated Guide to IS1010'. This guidebook can be purchased directly from his website: www.besttraining.ie