Foreword
This document aims to help the public better understand the application procedure, the requirements of the Grid Code and other issues relating to the Small Scale Distributed Generation (SSDG) project. Any applicant wishing to benefit from the SSDG scheme is informed that:
- ▸ Compliance with this Grid Code is mandatory.
- ▸ The provisions of the Electricity Act shall be complied with.
- ▸ This Grid Code will be revised and updated as required.
Disclaimer
The "Grid Code for Small Scale Distributed Generators (SSDG)" of the CEB constitutes the minimum technical requirements for the connection of distributed generation (DG), with or without a battery energy storage system (BESS), to the CEB low-voltage distribution network.
Injection of active power from the DG shall in no case exceed 50 kW AC at the point of delivery, as measured by the CEB Import/Export meter, or the maximum capacity of the scheme applicable at that time.
The CEB reserves the right to revise this Grid Code at any time.
Revision history
| Version | Date | Amendments |
|---|---|---|
| Version 2.3 | September 2019 | Minor revisions |
| Version 3.0 | April 2026 | Integration of requirements for SSDG with Battery Energy Storage System (BESS) |
Chapter 1 — Purpose of the Grid Code
The Grid Code describes the technical criteria and requirements for connecting Small Scale Distributed Generators (SSDG) to the CEB low-voltage network (230/400 V). It covers electricity generation and storage from inverter-based renewable energy sources such as photovoltaic.
More details on the schemes are available on the CEB website at ceb.mu/projects/energy-schemes.
Chapter 2 — Grid Code requirements and safety aspects
1. Design parameters
All DGs with an export capacity below 5 kW AC may have either single-phase or three-phase output. All DGs with an export capacity of 5 kW AC and above shall have three-phase output only. All inverters shall be of the Grid Forming type.
| Description | Plage |
|---|---|
| Voltage | 230/400 V ± 6 % |
| Short-circuit characteristics | (1 sec) 18 kA, (50 Hz) |
| Nominal frequency | 50 Hz |
| Legal frequency deviation | 50 Hz ± 1,5 % |
| Operating frequency range | 47 Hz – 52 Hz |
The CEB LV network is designed as a TT system. These values are mandatory for all DGs, with or without BESS.
2. Protection requirements
The DG shall be protected against: overload, short-circuit, earth faults, overcurrent, abnormal voltages, abnormal frequencies, lightning, and loss of mains.
2.4 Default trip settings
| Parameter | Symbol | Trip setting | Clearing time |
|---|---|---|---|
| Overvoltage (a) | U>> | 230 V + 10 % | 0,2 s |
| Overvoltage | U> | 230 V + 6 % | 1,5 s |
| Undervoltage | U< | 230 V − 6 % | 1,5 s |
| Overfrequency (b) | f> | 50 Hz + 1,5 % | 0,2 s |
| Underfrequency | f< | 50 Hz − 6 % | 0,5 s |
| Loss of mains | df/dt & Vector Shift | 2,5 Hz/s & 10° | 0,5 s |
(a) If the DG can generate a voltage higher than the U>> setting, stage 2 overvoltage is required. (b) The f> setting is lower than the maximum frequency in Table 1 to avoid the DG contributing to frequency rise.
2.5 Network islanding
DG without BESS: The DG shall not energize the CEB network during outages. It shall disconnect within 0.2 seconds of the formation of an island.
DG with BESS: A DG with BESS may operate in island mode. If it exports energy in grid-connected mode, it shall disconnect within 0.2 seconds of the formation of an island.
2.6 Reconnection
Following disconnection, the DG shall remain disconnected until the voltage and frequency have remained within nominal limits for at least 3 minutes. Automatic reconnection is only permitted when the disconnection is due to parameters outside the normal range in Table 1.
2.8 Earthing
Earthing shall comply with IEC 60364-5-55. The TT earthing system is standard on the CEB network. Neutral and earth conductors shall be separated throughout the installation.
3. Power quality
3.1 DC injection: The DG shall not inject direct current exceeding 0.25 % of the rated AC output current per phase.
3.2 Flicker: The installation shall not cause abnormal flicker beyond the limits of the "Maximum Irritation Threshold Curve" according to IEEE 519-2014.
3.3 Harmonics: Voltage THD shall not exceed 5.0 % of the fundamental at 400 V measured at the PCC.
| Odd harmonics | Max distortion |
|---|---|
| 3rd – 9th | 4,0 % |
| 11th – 15th | 2,0 % |
| 17th – 21st | 1,5 % |
| 23rd – 33rd | 0,6 % |
| Above the 33rd | 0,3 % |
3.4 Overvoltages: Resistance to oscillatory and fast transient overvoltages shall comply with IEC 62305-3 at test levels of 1.5 kV.
3.5 Unbalance: The total voltage unbalance in the network shall be less than 2 %. The contribution of an installation shall not cause an increase in unbalance of more than 1.3 %.
3.6 Step voltage variation: Variations caused by connection/disconnection shall not exceed ±3 % for planned events and ±6 % for unplanned outages.
| Connection | Inrush current |
|---|---|
| Single-phase | 19 A |
| Three-phase | 30 A |
4. Power factor
The power factor of the DG under normal conditions shall be between 0.95 leading and 0.95 lagging over the full legal nominal voltage range.
5. Network maintenance
Preventive and corrective maintenance on the feeder to which the DG is connected may interrupt production. No compensation shall be applicable for production loss due to maintenance.
6. Safety, isolation and switching
6.1 Rules for working on the LV network
- ▸ The system shall be isolated from all possible sources of supply; all switches shall be locked in visibly open positions.
- ▸ The DG shall have a local means of isolation that disconnects all live conductors, including the neutral.
- ▸ A switch with a visible break that can be locked in the open position shall be installed to disable automatic or manual closing of the interconnection switch.
- ▸ CEB shall maintain an updated register of all DG units, including precise addresses, connection points and the associated transformers.
6.2 Safety concerns
- ▸ People shall be warned that the installation includes a DG so that safety precautions are taken to avoid the risk of electric shock.
- ▸ PV cells generate energy when exposed to light. Additional precautions such as covering the PV cells are required before any intervention.
- ▸ The DG manufacturer or supplier shall certify compliance with the Electrical Equipment Safety Regulations and the Electromagnetic Compatibility Regulations.
6.3 Electrical installer
The installer shall affix a label indicating the next scheduled maintenance and inform CEB so that the SSDG register can be updated. The installer shall be qualified in the field of SSDG installations and hold an MQA-approved qualification or equivalent in electrical installation and renewable energy installations acceptable to CEB.
7. Metering
A bidirectional Import/Export meter measuring both imported and exported energy shall be installed at the Supply Terminal. A second meter measuring the gross production of the SSDG shall also be installed.
The SSDG promoter shall obtain CEB approval before ordering CTs and VTs, and shall send them to the CEB Metering Laboratory Section for testing before installation.
8. Standards and regulations
All electrical apparatus, materials and wiring shall comply with the Electricity Act, the CEB Act, the Electricity Regulations, this Code and the following standards in their latest applicable editions:
Modules PV
| Standard | Description |
|---|---|
| IEC TS 62804-1/-2 | Test methods for the detection of voltage-induced degradation |
| IEC 61215 | Crystalline silicon terrestrial PV modules — Design qualification and type approval |
| IEC 61701 | Salt mist corrosion testing of PV modules |
| IEC 61730 | PV module safety qualification |
PV inverters
| Standard | Description |
|---|---|
| IEC 61683 | Power conditioners — Procedure for measuring efficiency |
| IEC 62109-1/2 | Safety of power converters for use in PV power systems |
| IEC 62116 | Test procedure for prevention of islanding for grid-connected PV inverters |
Grid-connected PV systems
| Standard | Description |
|---|---|
| IEC 61727 | PV systems — Characteristics of the utility interface |
| EN 50438 | Requirements for the connection of micro-generators in parallel with public low-voltage distribution networks |
| IEC 62446-1 | PV systems — Requirements for testing, documentation and maintenance |
| IEC 61724 | PV system performance monitoring |
General engineering standards
| Standard | Description |
|---|---|
| IEC 60364-5-55 | Electrical installations of buildings |
| IEC 62305-3 | Protection against lightning — Physical damage and danger to life |
| IEC 60364-5-54 | Earthing arrangements and protective conductors |
| IEEE C37.90 | IEEE standard for relays and relay systems |
Power quality
| Standard | Description |
|---|---|
| IEC 61000-3-2 | Limits for harmonic current emissions |
| IEC 61000-3-3 | Limitation of voltage changes, voltage fluctuations and flicker |
| IEEE 519 | Recommended practice for harmonic control in electric power systems |
Battery Energy Storage System (BESS)
| Standard | Description |
|---|---|
| IEC 62933 | Series of standards for electrical energy storage systems (ESS) |
| IEC 62619 | Safety requirements for secondary lithium cells and batteries for industrial applications |
| IEC 63056 | Safety requirements for secondary lithium cells and batteries for use in electrical energy storage systems |
| UL 1973 / UL 9540 | Certification standards for battery safety testing |
| IEC 61000 series | Electromagnetic compatibility (EMC) |
Chapter 3 — Grid Code amendments
CEB shall propose a new version of this Grid Code in the following cases:
- ▸ Certain values need to be revised due to system evolution.
- ▸ The amount of generation in one or more segments requires stricter control.
- ▸ Better alignment with operating conditions is required.
- ▸ Additional amendments to the Grid Code must be prepared as an addendum.
Chapter 4 — Non-compliance with the Grid Code
In the event of non-compliance with any technical provision of this Grid Code, CEB shall notify the owner in writing of the deviations observed. The DG owner shall have 30 days to rectify the deviations.
Failing this, CEB shall be entitled to disconnect the DG.
CEB shall be entitled to disconnect the DG without prior notice if the installation conditions are dangerous or create unavoidable safety risks.
Reconnection shall require CEB to certify that the installation complies with this Grid Code. Applicable fees shall be the same as standard reconnection fees.
Annex 1 — Abbreviations and definitions
Annex 2 — Installation Certificate
The applicant/installer shall submit a duly signed certificate on company letterhead bearing the company stamp to CEB. The Installation Certificate shall confirm:
- ▸ Installed capacity [kW] and site address
- ▸ Details of installed equipment: PV Modules and Inverter (make, model, rated power, quantity, serial numbers)
- ▸ Inverter protection settings: Overvoltage ×2, Undervoltage, Overfrequency, Underfrequency, Loss of mains df/dt & Vector shift, Reconnection time, Active power limit
- ▸ Line impedance (ohm)
- ▸ Name and signature of the installing company and the Registered Professional Engineer / Installer (with RPEM number where applicable)
- ▸ Name and signature of the Applicant
- ▸ Company stamp and date
Annex 3 — Commercial commissioning
Commercial commissioning of the SSDG is subject to the Connection Agreement being signed by all parties and to verification by CEB representatives that the installation complies with this Grid Code. The installation shall be commissioned after signature of the Connection Agreement.
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