Foreword
This document aims to help the public better understand the application procedure, the requirements of the MSDG Grid Code and other issues relating to the Medium Scale Distributed Generation project. Compliance with this Grid Code is mandatory for any prospective applicant. The provisions of the Electricity Act 2005 and the Environment Protection Act 2002 shall also be complied with.
Disclaimer
The MSDG Grid Code constitutes the minimum technical requirements for the connection of medium-scale distributed generation to the CEB distribution network.
The applicable capacity is above 50 kW and not exceeding 500 kW at the point of delivery, unless otherwise revised by the CEB.
The DC/AC ratio shall not exceed 1.2. The CEB reserves the right to revise this Grid Code at any time.
Revision history
| Version | Date | Amendments |
|---|---|---|
| Version 1.0 | May 2016 | Initial version |
| Version 2.0 | December 2017 | Updates to protection settings and standards |
| Version 2.1 | October 2019 | Updates to interconnection and metering requirements |
| Version 3.0 | September 2024 | Applicable capacity, DC/AC ratio and Installation Certificate |
Chapter 1 — Purpose of the Grid Code
This Grid Code describes the technical criteria and requirements for connecting distributed generation units with a capacity above 50 kW but not exceeding 500 kW to the CEB 22 kV distribution network. It covers PV, wind, hydro and biomass technologies.
More details on the schemes are available on the CEB website at ceb.mu/projects/energy-schemes.
Chapter 2 — Connection process
- 1 Submission of the MSDG application form and technical specifications to the CEB MSDG Unit, Curepipe.
- 2 Assessment of the proposal against Grid Code requirements. A system impact study may be required.
- 3 Issue of a Letter of Intent with the allocated capacity and applicable fees.
- 4 Acceptance of the conditions and payment of the fees by the applicant.
- 5 Signing of the Connection Agreement during a joint site meeting.
- 6 Completion of the interconnection works during a planned supply outage.
- 7 Completion of the MSDG installation within 12 months. Submission of the Installation Certificate.
- 8 Testing and commissioning by the CEB.
Chapter 3 — Technical requirements of the Grid Code
1. Design parameters
All MSDG installations shall have a three-phase output only. All inverters shall be of the Grid Forming type. The DC/AC ratio shall not exceed 1.2.
| Description | Range |
|---|---|
| Statutory voltage range | 230/400 V ± 6 % |
| Short-circuit level (excluding MSDG contribution) | 18 kA (50 Hz, 1 sec) |
| Nominal frequency | 50 Hz |
| Statutory frequency deviation | 50 Hz ± 1.5 % |
| Operating frequency range | 47 Hz – 52 Hz |
2. Protection requirements
The DG shall be protected against: overload, short-circuit, earth faults, overcurrent, abnormal voltages, abnormal frequencies, lightning, and loss of mains.
| 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 |
Islanding: The DG shall disconnect within 0.2 seconds of the formation of an island. Following disconnection, the DG shall remain disconnected until the voltage and frequency have remained within nominal limits for at least 3 minutes.
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 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 % |
3.5 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 |
|---|---|
| LV three-phase | 30 A |
| MV (via transformer) | As per CEB study |
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 statutory nominal voltage range.
5. Network maintenance
Preventive and corrective maintenance of the feeder to which the DG is connected may interrupt production. No compensation shall be applicable for loss of production due to planned or emergency maintenance.
6. Safety, isolation and switching
6.1 Isolation: The system shall be isolated from all possible sources of supply. A switch with visible contact that can be locked in the open position shall be installed.
6.2 Installer: The installer shall hold an MQA-approved or equivalent qualification in electrical installation and renewable energy systems acceptable to the CEB.
6.3 Registered Professional Engineer: A Registered Professional Engineer shall sign the Installation Certificate and supervise the interconnection works.
7. Metering
A bidirectional Import/Export meter of class 0.5 or better shall be installed at the Supply Terminal. A second meter measuring the gross production of the MSDG shall also be installed.
The MSDG promoter shall obtain CEB approval before ordering CTs and VTs, and shall send them to the CEB Metering Laboratory Section for testing prior to installation.
8. Standards and regulations
All equipment shall comply with the following standards (latest applicable editions):
PV modules
| Standard | Description |
|---|---|
| IEC 61215 | 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 62109-1/2 | Safety of power converters for use in photovoltaic power systems |
| IEC 62116 | Anti-islanding prevention for utility-interconnected PV inverters |
| IEC 61683 | Procedure for measuring efficiency |
Grid connection
| Standard | Description |
|---|---|
| IEC 61727 | Photovoltaic (PV) systems — Characteristics of the utility interface |
| IEC 62271 | High-voltage switchgear and controlgear |
| IEC 60076 | Power transformers |
General standards
| Standard | Description |
|---|---|
| IEC 60364-5-54 | Earthing arrangements and protective conductors |
| IEC 62305-3 | Protection against lightning |
| IEEE 519 | Control of harmonics in electrical power systems |
Chapter 4 — Amendments to the Grid Code
- ▸ Some values need to be revised owing to system evolution.
- ▸ The quantity of generation in one or more segments requires stricter control.
- ▸ Better alignment with operating conditions is required.
- ▸ Additional amendments to the Grid Code shall be prepared as an addendum.
Chapter 5 — Non-compliance with the Grid Code
In case of non-compliance, the CEB will inform the owner in writing of the deviations found. The owner shall have 30 days to rectify the deviations.
Failing that, the CEB shall be entitled to disconnect the DG. Reconnection will require certification of compliance by the CEB.
The CEB shall be entitled to disconnect the DG without prior notice if the installation conditions are dangerous.
Annex 1 — Abbreviations and definitions
Annex 2 — Installation certificate
The applicant/installer shall submit a duly signed certificate on company letterhead with company stamp to the CEB. The Installation Certificate shall confirm:
- ▸ Installed capacity [kW] and site address
- ▸ Equipment details: PV modules and inverters (brand, model, rating, quantity, serial numbers)
- ▸ DC/AC ratio of the installation
- ▸ Inverter protection parameters: voltages, frequencies, loss of mains and reconnection time
- ▸ Name and signature of the Registered Professional Engineer with registration number
- ▸ Stamp of the installing company and date
Annex 3 — Commercial commissioning
Commercial commissioning of the MSDG shall be subject to the signature of the Connection Agreement by all parties and verification of the installation's compliance with this Grid Code by CEB representatives.
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