GRID CODE MEDIUM SCALE DISTRIBUTED GENERATION (MSDG) Greater than 200kW but not exceeding 2MW. Version 2.1. December 2013

Transcription

1 GRID CODE MEDIUM SCALE DISTRIBUTED GENERATION (MSDG) Greater than 200kW but not exceeding 2MW Version 2.1 December 2013 CENTRAL ELECTRICITY BOARD Royal Road Curepipe Mauritius Tel No.: (230) Fax No.: (230) P a g e

2 Foreword The purpose of this document is to assist the public to better understand the procedure for application, the requirements of the Grid Code, the Feed-in-Tariffs and other related issues regarding Medium Scale Distributed Generation (MSDG). Any prospective applicant willing to take advantage of the Medium Scale Distributed Generation (MSDG) Scheme is informed that: I. Compliance to this Grid Code is mandatory II. III. The provisions of the Electricity Act shall be adhered to. This Grid Code will be reviewed and updated when the need arises. i P a g e

3 TABLE OF CONTENTS CHAPTER 1 Purpose of the Grid Code... 1 CHAPTER 2 Connecting Medium Scale Distributed Generation to the Grid 2 CHAPTER 3 MSDG Interconnection Requirements and Safety Aspects Interconnection Facility Characteristics kV System Parameters MSDG High Voltage Switchgear MSDG Interconnection transformer Earthing Arrangement Protection Requirements Interconnection protection scheme Anti-Islanding protection Inter-tripping protection for MSDG of capacity greater than 500kW Protection against relay malfunction Protection Study Synchronising AC generators Re-connection Uninterruptible Power Supply Indication, Alarms and Instrumentation Communication Requirements Metering Safety, Isolation and Switching Safety Procedures regarding the operation of High Voltage Switchgear Safety Concerns Electromagnetic emission/immunity Labels Documentation Information Plate Electrical Contractor/Installer Standard and Regulation. 13 CHAPTER 4 Guarantee Operating Characteristic Fault Ride Through Requirements Frequency Response Reactive Power Capability Power Quality Limitation of voltage flicker induced by the MSDG Harmonics Voltage step change ii P a g e

4 4.4.4 Surge Withstand Capability Voltage and Current Unbalance Ramp Rate Limits.. 18 CHAPTER 5 Testing and Commissioning Introduction Testing of MSDG Facility Commissioning of electrical system Power Quality. 20 Annex 1 Abbreviations and Definitions 21 Annex 2 CEB Feed-In-Tariff 23 Annex 3 CEB Fees. 24 Annex 4 Application Form.. 25 Annex 5 Certificate of Installation Annex 6 Certificate of Compliance. 33 Annex 7 22kV Switchgear Arrangement Annex 8 Interconnection Facility Description.. 35 Annex 9 Interconnection Transformer Specifications. 43 Annex 10 Mineral Insulating Oil for Transformers Annex 11 Typical Medium Voltage Switchgear Panel and Protection Arrangement. 50 Annex 12 Protection Specifications.. 51 Annex 13 Communication Requirement. 52 Annex 14 Typical 22kV Switchgear Room.. 54 iii P a g e

5 CHAPTER 1 Purpose of the Grid Code This Grid Code describes the technical criteria and requirements for the connection of distributed generation unit (s) of capacity greater than 200 kw but not exceeding 2MW to the CEB s 22 kv distribution network. The aggregate capacity of all medium-scale distributed generation (MSDG) facilities that can be interconnected to a 22kV distributed feeder is termed as the hosting capacity and is taken as 100% of the minimum load demand on that feeder. The aggregate capacity of all MSDG facilities of capacity less than 200 kw that can be interconnected to a 22kV distributed feeder is limited to 50 % of the hosting capacity of that feeder. The application for the interconnection of any MSDG facility to a 22kV distribution feeder shall be considered provided that with the proposed MSDG facility, the aggregate installed capacity of the MSDG facilities connected to the 22kV distribution feeder does not exceed the hosting capacity of that feeder. Notwithstanding the above limits, the feasibility to connect any MSDG to CEB 22 kv distribution network will need to be confirmed by a system impact study which will be conducted by the CEB on a case to case basis. In addition, the possibility of interconnecting any MSDG facility with variable power output shall be subject to the maximum amount of variable renewable energy-based power generation that can be accommodated in the CEB s power system while maintaining the system stability and security not being exceeded with the proposed MSDG facility. The Grid Code caters for the production of electricity by the following list of renewable energy technologies (RETs): 1. Photovoltaic (PV) 2. Wind Turbine Generator (WTG) 3. Hydroelectric Generator 4. Biomass-based generator 1 P a g e

6 CHAPTER 2 Connecting Medium Scale Distributed Generation to the Grid 1. START 2. Duly filled MSDG Application Form, requested technical specifications and processing fees (see Annex 4) to be deposited at CEB Head Office, Curepipe 3. Analysis of MSDG Proposal with respect to MSDG Grid Code requirements and standards 4. Applicant to settle related Engineering Review Fee upon CEB request (see Annex 3) 5. Cost estimate for any required network construction & System Impact Study Fees sent to applicant 6. Applicant agrees to proceed with the MSDG project? NO MSDG Project terminated YES END 7. CEB provides Applicant with a Public Notice, to be published in Government gazette and 2 newspapers 8. Copy of published notices forwarded to CEB 9. Is there any objection within 14 YES Applicant takes remedial action A NO 2 P a g e

7 A 10. CEB request the Ministry of Energy and Public Utilities (MEPU) for the Granting of Permit by the President to the Applicant 11. The applicant shall be given a non-transferable permit as per the terms and conditions that will be laid down in a Connection Agreement to be signed by the CEB and the Applicant after successful testing of the latter s installation 12. Applicant shall effect payment for any network construction or upgrade for safe interconnection of MSDG 13. Applicant shall complete the MSDG installation within the 12 months from date of Grant of Permit 14. Upon completion of installation, applicant/installer shall submit a duly signed Certificate of Installation as per Annex 5 to the CEB 15. CEB shall inspect and test the installation for compliance with the requirements and standards. CEB will then issue a certificate of compliance to the Applicant 16. Signature of Connection Agreement 17. CEB request the MEPU for the Proclamation by the President to the applicant 18. Upon proclamation, Applicant reaches Commercial Operation END 3 P a g e

8 CHAPTER 3 MSDG Interconnection Requirements and Safety Aspects 3.1 Interconnection Facility Characteristics The facility is described hereunder: The facility is connected to CEB s 22 kv network through a step up interconnection transformer. The CEB Interconnection Facilities which shall be the facilities required to interconnect the Generation Facility to the CEB 22kV Distribution System located on the CEB side of the Point of Common Coupling(PCC) /Point of Delivery,(A), as shown in Annex 7. The MSDG Interconnection Facilities which shall be the facilities required to interconnect the Generation Facility to the CEB System located on the Generation Facility side of the Point of Common Coupling (PCC)/ Point of Delivery (A) as shown in Annex kV System Parameters The MSDG has the following design parameters. The MSDG has to function and protect itself within the following range of the voltages, currents and frequencies existing in the CEB grid. Service Voltage : 22 kv ± 6% Emergency Voltage : 22 kv ± 10% System Earthing : Effectively earthed/non-effectively earthed Frequency : 50 Hz ± 1.5% Fault Level : 600 MVA Operating Frequency : 47 Hz 52Hz 3.3 MSDG High Voltage Switchgear The switchgears shall be arranged as illustrated in Annex 7 -, consisting of CEB interconnection facilities and MSDG interconnection facilities demarcated by a metallic barrier. The applicant shall construct, install, test and commission the complete 22kV switchboard as Annex 7 -, i.e. the CEB as well as the MSDG side. CEB will take ownership of its side after the guarantee period. The switchgear shall have the following characteristic: Insulation rated voltage : 24 kv Impulse test voltage 1, 2/50 µs : 125 kv peak Rated short circuit capacity : 16 ka rms 1 sec Electro-dynamic withstand : 40 ka peak Busbar rating : 400 A The detailed technical characteristics and responsibilities of the 22kV switchgear are given in Annex 8. The 22kV switchgear shall be approved by the CEB prior to ordering. 4 P a g e

9 3.4 MSDG Interconnection transformer The MSDG interconnection transformer shall be of vector group Dyn11 (Delta on High Voltage Side and Star on MSDG Side). The delta winding on the CEB side ensures that: (i) The performance and sensitivity of the earth fault protection scheme at CEB substation are not affected; (ii) Triplen harmonics from the MSDG do no reach CEB s network (iii) The MSDG is provided some isolation from voltage sags due to single-line-to- ground faults, allowing it to better ride through voltage sags. The detailed specifications of the interconnection transformer are given in Annex 9. The transformer shall be approved by the CEB prior to ordering. 3.5 Earthing Arrangement The earthing arrangement of the generating plant must be designed to ensure compatibility with Earthing system of the CEB distribution network. The actual earthing arrangements will also be dependent on the number of generating units in use and the generators system configuration and method of operation. The system earth connection shall have adequate electrical and mechanical capability for the duty. In the event that the Applicant wishes to operate independently and isolated from the CEB s system, the Applicant shall ensure that the electrical and protection systems of the facility are designed to support such mode of operation. Safety of personnel and integrity of equipment shall be guaranteed at all times during both parallel and isolated modes of operation. Earthing systems shall be designed, installed, tested and maintained according to BS 7354 (Code of Practice for Design of high voltage open terminal stations) and BS 7430 (Code of Practice for Protective Earthing of electrical installations). Steps must be taken to prevent the appearance of hazardous step and touch potential when earth faults occur on the 22 kv network. The 22 kv earth electrodes and low voltage earth electrodes shall be adequately separated to prevent dangerous earth potentials being transferred to the low voltage network. 3.6 Protection Requirements The protection system, made up of two schemes, shall provide protection against fault occurring on both the CEB s network and the MSDG facility. The first protection scheme is to provide protection against short circuit, earth faults and overloading conditions while the second scheme is to prevent islanding operation of the CEB distribution feeder whereby the MSDG is connected. Both schemes shall incorporate a watchdog function that monitors relay status. Note that the relays used shall be of modern numerical type and of utility grade. The two schemes are detailed in the subsections and as interconnection protection scheme and antiislanding protection scheme respectively. A typical protection diagram for any MSDG is illustrated in Annex P a g e

10 In addition, the applicant must provide any additional protection functions necessary to adequately protect all equipment and personnel. The settings of the additional protection systems must be appropriately graded to prevent unnecessary trips during disturbances that affect voltage and frequency on the CEB system Interconnection protection scheme The Interconnection Protection Scheme must provide protection against short circuit, earth fault and overloading conditions. This scheme shall consist of the following protection functions: (i) instantaneous/time delayed overcurrent (50/51) (ii) instantaneous/time delayed earth fault (50/51N) (iii) Neutral Voltage Displacement (59N). The characteristics for these protection functions are detailed in Annex 12. The protection shall act on the line circuit breaker of the CEB Interconnection facilities(circuit Breaker 1 (CB1) as shown in Annex 7). The settings for the protection functions 50/51 and 50/51N shall be determined by the applicant, through a proper protection study, and submitted to CEB for approval. The setting for the neutral voltage displacement is to be calculated as follows: Table 1 Short circuit protection trip settings Parameter Symbol Trip setting Clearance Neutral Voltage Displacement (59N) NVD 1270V t0*+ 0.5s *t0 is the maximum time delay for the CEB interconnecting feeder earth fault protection Note: The protection requirement for the step-up transformer shall be determined by the applicant Anti-islanding protection The MSDG shall not supply power to the CEB s network during any outages of the system. The MSDG may only be operated during such outages to supply the applicant s own load (isolated generation) with a visibly open tie to the CEB s network. The MSDG shall cease to energise the CEB s network within 0.5 seconds of the formation of an island. The following protection functions and settings are required. Over and under frequency (functions 81O and 81U) Three-phase under-voltage and overvoltage (functions 27 and 59) Rate of Change Of Frequency (ROCOF) Voltage vector shift (VVS) 6 P a g e

11 Table 2 Anti-islanding protection trip settings Parameter Symbol Trip setting* Clearance Overvoltage (27) U>> Vφ-φ + 7% 0.2s Overvoltage (27) U> Vφ-φ + 5% 1.5s Undervoltage (59) U< Vφ-φ 6% 1.5s Overfrequency (81O) f> 51.5 Hz 0.5 s Underfrequency (81U) f< 47 Hz 0.5s Loss of mains LoM 2.5 Hz/s 10 degrees 0.5s 0.5s * The above trip settings are indicative and may be subject to change upon request of the CEB for safe interconnection to the network. The anti-islanding protection shall act on CB4 (LV interconnection circuit breaker) as shown in the typical switchgear and protection arrangement in Annex 7. For MSDG facilities of capacity equal to or greater than 500 kw, inter-tripping facility using fibre optic cables will be required. This is detailed further in section Inter-tripping protection for MSDG of capacity equal to or greater than 500 kw The inter-tripping scheme shall be designed such that tripping of the interconnecting feeder circuit breaker in the CEB 22 kv substation results in the tripping of CB1 (see Annex 7). The tripping of CEB s 22 kv circuit breaker shall be a tripping due to protective relay action at CEB 22 kv substation level. Manual tripping of CB1 shall not cause tripping of corresponding circuit breaker at CEB 22 kv substation Protection against relay malfunction The watchdog function of the protection relay protection must issue an alarm and trip the circuit breaker on which the protection relay normally acts in case the there is a malfunction. For MSDG of capacity equal to or greater than 500 kw, this alarm signal shall be transmitted to the interconnecting CEB substation via the fibre optic channel Protection study For MSDG of capacity above 200 kw, the Applicant shall submit to CEB a complete protection study report showing the following: All protection calculations complete with graphs Grading of the interconnection protection with CEB substation protection Grading of the interconnection protection with MSDG protection scheme. 3.7 Synchronising AC generators The MSDG shall provide and install automatic synchronizing. Check Synchronizing shall be provided on all generator circuit breakers and any other circuit breakers, unless interlocked, that are capable of connecting the MSDG plant to the CEB s network. Check Synchronising Interlocks shall include a feature such that circuit breaker closure via the Check Synchronising 7 P a g e

12 Interlock is not possible if the permissive closing contact is closed prior to the circuit breaker close signal being generated. 3.8 Re-connection Following a protection initiated disconnection, the MSDG is to remain disconnected from the network until the voltage and frequency at the supply terminals has remained within the nominal limits for at least 3 minutes. Automatic reconnection is only allowed when disconnection was due to operating parameters being outside the normal operating range stated in Table 2, not if disconnection was caused by malfunctioning of any devices within the MSDG installation. 3.9 Uninterruptible Power Supply An uninterruptible power supply is required and it shall have adequate capacity to ensure that the protection, measurement, control and communication systems operate without interruption for a minimum duration of at least 30 minutes after loss of CEB power supply Indication, Alarms and Instrumentation The alarm and trip facilities shall have local indication and, for MSDG equal to or greater than 500 kw, an additional set of potential-free contacts for onward transmission of the alarm/trip signals to the CEB Substation. The following panel instrumentation and other fittings are required in addition to other standard equipment required or implied for the type of panel and scheme functionality: a. Transducer fed voltmeter, ammeter, MW, MVAr, indicating import and export, and appropriate test blocks for current and voltage circuits. b. Suitable test facilities shall be provided for the secondary injection of current/relay testing and for any other tests as reasonably required by CEB. External indicator lamps shall be installed to indicate parallel operation of the MSDG facility with CEB distribution network Communication Requirements MSDG, of capacity equal to or greater than 500 kw, shall install communication equipment for secured transfer of operating data and protection and control signals via fibre optics cables as per Annex 13. The connection of the fibre optics to the RTU of the CEB s substation shall be solely the responsibility of the CEB. Note that the Applicant shall bear the cost for the installation of fibre optic cables from the MSDG plant to the corresponding substation. Relevant information for the operation of the electrical system will be transmitted in real time to the System Control through the RTU (remote terminal unit) available at the substation. i. One-Way communication from the CEB Substation to the Generation Facility via the fibre-optic link of: - 22kV Circuit breaker status at the CEB substation(open/close); 8 P a g e

13 ii. iii. iv. One Way communication from the Generation Facility to the CEB Substation via the fibre optics - Cubicle 1 Circuit Breaker Status (open/close) - Cubicle 4 Circuit Breaker Status (open/close) - Alarms - MW, MVAr - Voltage level of the Generation Facility 22kV Busbar Remote control facilities shall be provided: - Cubicle 1 circuit breaker open; - Cubicle 1 circuit breaker close. Optical Fibre 3.12 Metering The Optical fibre shall connect the generation facility and the 22kV feeder s Substation on which the MSDG is interconnected. The applicant shall bear the cost of the procurement, installation and commissioning of the fibre optic link. CEB Meters will have an accuracy class of 0.2 and shall measure the electrical energy delivered to CEB by the MSDG as well as Import Energy imported by the MSDG from the CEB System. A cubicle shall be ordered by CEB to house the CEB Meters. The CEB metering circuits shall be totally separate from the MSDG metering circuits. This is to be achieved through cabling directly from the metering current transformers (CTS) and voltage transformers (VTs). CEB shall be fully responsible for the commissioning of the metering circuits associated with CEB Meters, i.e. all pre-commissioning and final commissioning involving cabling and other circuit verification, CT and VT checks and certification, functional testing, as well as meter calibration, secondary injection and final documentation. In addition the panel shall also provide for the accommodation of a digital 3-phase power recorder/monitor with the remote communication capabilities, for power quality analysis, energy management, data transfer and supervisory control needs. The applicant may install at his own cost a backup meter capable of recording both the export of electrical energy from Facility to the CEB Interconnection Facilities and the import of electrical energy by the Facility from the CEB Interconnection Facilities. In this respect, an optional cubicle housing the CTs and VTs will be required in the MSDG Interconnection Facilities (see Annex 7) Safety, Isolation and Switching Safety Procedures regarding the operation of High Voltage Switchgear In order to ensure the safety of personnel while operating or working on High Voltage Switchgear installed for the purpose of supplying electricity to your premises, the following requirements and procedures shall be adhered to:- 9 P a g e

14 (a) To comply with Section 7(a) of the Occupational Safety, Health and Welfare Act of 2005 which states Where the total power used or generated by the machinery installed at any place of work exceeds 750 kilowatts, the employer shall employ a Registered Professional Engineer to be in general charge of all such machinery. (b) (c) (d) (e) The Applicant shall appoint and train competent person/s who shall be responsible for the operation of the High Voltage Switchgear. He/they shall be fully conversant with the electrical set-up, including that of the Switchgear belonging to CEB. An up-to-date schematic diagram of the switchgear set-up shall be displayed in the switchgear room (See Annex 7). All switchgear panels shall be clearly numbered and labelled. Before any work can be performed on either side of the switchgear panel appropriate switching operations shall be carried out by the respective competent person in the presence of his respective counterpart. The competent person performing the operations shall certify the operations carried out on the approved form and shall remit the original to his counterpart, who may then proceed with the work in accordance with the Safety Rules. Note: The person receiving the above information shall ensure that the switchgear involved shall not be inadvertently operated by securing them by means of personal padlocks and by affixing proper warning signs. (f) In case of private generation, the client shall ensure that his system is completely isolated from CEB system Safety Concerns The applicant shall observe the following safety concerns which include: (a) (b) (c) Persons must be warned that the installation includes an MSDG so that precautions can be taken to avoid the risk of electric shock. Both the mains supply and the electric generator must be securely isolated before electrical work is performed on any part of the installation. Adequate labelling must be available to warn that the installation includes another source of energy. Photovoltaic (PV) cells will produce an output whenever they are exposed to light, and wind turbines are likely to produce an output whenever they are turning. Additional precautions such as covering the PV cells or restraining the turbine from turning will be necessary when working on those parts of the circuit close to the source of energy and upstream of the means of isolation. The manufacturer or supplier of the MSDG is required to certify compliance with the Electrical Equipment Safety Regulations and the Electromagnetic Compatibility Regulations. The MSDG will be CE marked or tested by equivalent accredited testing 10 P a g e

15 agencies to confirm this. This should ensure that the MSDG is satisfactory in a domestic installation in terms of the power factor, generation of harmonics and voltage disturbances arising from starting current and synchronisation. (d) CEB personnel must be warned of the safety procedures pertaining to switching operation applicable to the MSDG. These procedures must clearly be displayed and visible at the MSDG site Electromagnetic emission/immunity The MSDG shall comply with the requirements of the EMC Directive and in particular the product family emission standards Labels Figure 0-1 MSDG warning sign To indicate the presence of the MSDG within the premises, a label as per Figure 3.1 will be fixed by the CEB at: (a) (b) (c) (d) (e) (f) (g) (h) The nearest 22 kv pole on which the switch fuses are installed (or the Ring Main Unit in case of underground networks) Switchgear Room the transformer cabin door and fence the metering cabin and box the CEB incoming feeder cubicle the voltage transformer cubicle the interconnection circuit breaker cubicle any other locations found necessary. The installation operating instructions must contain the manufacturer s contact details e.g. name, telephone number and web address. 11 P a g e

16 3.14 Documentation Up-to-date information must be displayed at the MSDG as follows: (a) A circuit diagram showing the relationship between the MSDG and the CEB s incoming feeder as shown in Annex 7 -. This diagram is also required to show by whom the generator is owned and maintained. (b) A summary of the interconnection and anti-islanding protection settings. The Annex 11 - is an example of the type of circuit diagram that needs to be displayed. (c) Switching operation at the MSDG facility (d) In addition the maintenance requirements and maintenance services available shall be documented. (e) The applicant shall keep a certificate signed by the maintenance contractor containing at least the following: A statement confirming that the solar PV system/wind turbine/hydro, switchgear and interconnection transformer meets the requirements of this standard. Client s name and address. Site address (if different). Contractors name, address etc. List of key components installed. Estimation of system performance 3.15 Information plate The following information shall appear on the information plate: (a) manufacturer s name or trade mark; (b) type designation or identification number, or any other means of identification making it possible to obtain relevant information from the manufacturer; (c) rated power; (d) nominal voltage; (e) nominal frequency, (f) phases; (g) power factor Electrical contractor / Installer The MSDG shall be installed in accordance with the instructions issued by the manufacturer. In designing a connection for any MSDG, the electrical contractor /installer must consider all the issues that would need to be covered for a conventional final circuit, including: the maximum demand (and the generator output); the type of earthing arrangement; the nature of the supply; external influences; 12 P a g e

17 compatibility, maintainability and accessibility; protection against electric shock; protection against thermal effects; protection against overcurrent; isolation and switching; selection and installation issues. The installer must affix a label clearly indicating the next scheduled maintenance of the installations and inform the CEB, who will add the information to the MSDG-register. The installer must be skilled in the field of MSDG installations and possess an approved certificate Standard and Regulations All electrical apparatus, materials and wiring supplied shall comply with the Electricity Act, the Central Electricity Board Act, Electricity Regulations, this code and the following standards: EN EN EN EN IEC IEC IEC IEC IEC Datasheet and nameplate information of photovoltaic module. Requirements for the connection of micro-generators in parallel with public low-voltage distribution networks Connectors for photovoltaic systems - Safety. Data sheet and name plate for photovoltaic inverters Environmental testing of specimen to withstand specific severities of repetitive and non- repetitive nature Conductors of Insulated Cables Electrical installations of buildings - Part 1: Scope, object and fundamental principles Electrical installations of buildings. Part 5: Selection and erection of electrical equipment. Chapter 54: Earthing arrangements and protective conductors Electrical installations of buildings IEC IEC IEC IEC IEC IEC IEC Power Cables with extruded insulation and their accessories for rated voltages from 1 kv (Um 1.2 kv) up to 30 kv (Um = 36 kv) Part 1 - Cables for rated voltages for 1 kv (Um=1.2 kv) and 3 Insulation coordination for equipment within low-voltage systems Part 1: Principles, requirements and tests Photovoltaic devices: Part 1 Measurement of Photovoltaic current-voltage characteristics Short circuit calculation in three-phase ac systems. Connectors for photovoltaic systems - Safety. Limits Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment with rated current 16 A per phase and not subject to conditional connection Assessment of emission limits for the connection of the connection of fluctuating installations to MV, HV and EHV power systems. 13 P a g e

18 IEC IEC IEC IEC IEC IEC IEC IEC IEC IEC IEC IEC IEC IEC IEC IEEE ISO 9060/1990 IEEE P1547 IEEE IEEE C37.90 BS 7354 BS 7430 ER G59/2 Generic standard -EMC - Susceptibility - Residential, Commercial and Light industry Generic standard - EMC - Emissions - Residential, Commercial and Light industry Crystalline silicon terrestrial photovoltaic (PV) modules - Design qualification and type approval Wind Turbine Generator Systems Part 21: Measurement and assessment of power quality characteristics of grid connected wind turbines. Photovoltaic systems - Power conditioners - Procedure for Measuring Efficiency Photovoltaic (PV) systems - Characteristics of the utility interface Photovoltaic (PV) module safety qualification Solar photovoltaic energy systems - Terms, definitions and symbols Photovoltaic (PV) module performance testing and energy testing Part 1: Irradiance and temperature performance measurements and power rating Balance-of-system components for photovoltaic systems Safety of power converters for use in photovoltaic power systems Test procedure of islanding prevention measures for utility-interconnected photovoltaic inverters. General requirements for empty enclosures for low voltage switchgear and control gear assemblies Protection against lightning, part 3 physical damage and life hazards in structures Grid connected photovoltaic systems - Minimum requirements for system documentation, commissioning tests and inspection Recommended practices and requirements for harmonic control in electric power systems Solar energy -- Specification and classification of instruments for measuring hemispherical solar and direct solar radiation Series of Standards for Interconnection, May, 2003, NREL/CP IEEE Recommended practice and requirements for harmonic control of electric power systems, Institute of Electrical and Electronic Engineers, Piscataway, NJ. April 1992 IEEE Standard for Relays and Relay Systems Associated with Electric Power Apparatus Code of Practice for Design of high voltage open terminal stations Code of Practice for Protective Earthing of electrical installations Recommendations for the Connection of Generating Plant to the Distribution Systems of Licensed Distribution Network Operators 14 P a g e

19 Voltage at Point of Delivery (pu) CHAPTER 4: Guarantee Operating Characteristic 4.1 Fault Ride through Requirements The MSDG shall remain connected to the distribution system for system voltage dips on any or all phases, where the distribution system voltage measured at the PCC to the grid remains above the heavy red line in the voltage duration profile of the figure below pu Fault Incidence pu MSDG May Trip Time (seconds) Figure: Low voltage Ride through Capability for MSDG In addition to remain connected to the distribution System, the MSDG shall have the technical capability to provide the following: During the distribution System Voltage dip the MSDG shall provide active power in proportion to retained voltage and maximise reactive current to the distribution system without exceeding the MSDG Limit. The maximisation of reactive current shall continue for at least T second or until the distribution System Voltage recovers to within the normal operational range of the distribution System whichever is the sooner. Due to the dynamic nature of the distribution network higher or lower fault clearance time for the MSDG may be required, which shall then be discussed with the CEB. 4.2 Frequency Response In case of frequency deviations in the CEB network, the MSDG shall be designed to be capable to provide power-frequency response in order to contribute to the stabilisation of the grid frequency. 15 P a g e

20 Active Power Output (as a % of Available Active Power) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Frequency (Hz) MSDG of capacity greater and equal to 1MW shall be able to provide frequency response as displayed in the above figure. Under normal system frequency ranges, the MSDG should operate with an active power output as set in the above figure. The MSDG shall have to reduce the power output about a system frequency above 50.5Hz. The power has to be reduced with a gradient of 40% per Hz of the instantaneously available power. The output power is only allowed to increase again as soon as the frequency is only 50.05Hz. Above 52Hz and below 47Hz the plant has to disconnect from the grid. 4.3 Reactive Power Capability The MSDG shall be equipped with reactive power control functions capable of controlling the reactive power supplied by the MSDG at the PCC as well as voltage control function capable of controlling the voltage at the PCC via orders using set points and gradients The reactive power and voltage control functions shall be mutually exclusive, which means that only one of the three functions mentioned below can be activated at a time: a) Voltage Control b) Power Factor Control c) Reactive Power Control The actual operating modes, as listed above, as well as the operating point shall be determined by the CEB. The functional mode and set-point of the MSDG shall not be changed unless instructed by CEB. The MSDG shall be designed with the capability to supply rated power (MW) for power factors ranging between 0.95 lagging and 0.95 leading, available from 20% of rated power measured at the PCC. 16 P a g e

21 4.4 Power Quality The MSDG facilities and equipment shall not cause excessive voltage excursions nor cause the voltage to drop below or rise above the range maintained by CEB. The MSDG facility and equipment shall not introduce excessive distortion to the sinusoidal voltage or current waves Limitation of voltage flicker induced by the MSDG The MSDG installation shall not cause abnormal flicker beyond the limits defined by the Maximum Borderline of Irritation Curve specified in the IEEE Harmonics The total harmonic distortion will depend on the injected harmonic current and the system impedance seen from the PCC. The MSDG system output should have low current-distortion levels to ensure that no adverse effects are caused to other equipment connected to the utility system. The MSDG system electrical output at the PCC should comply with Clause 10 of IEEE Std and should be used to define the acceptable distortion levels for PV systems connected to a utility. The key requirements of this clause are summarized in the following: (a) Total harmonic current distortion (Total demand distortion, TDD) shall be less than 5% of the fundamental frequency current at rated current output. (b) Each individual harmonic shall be limited to the percentages listed in Table 3. The limits in Table 3 are a percentage of the fundamental frequency current at rated current output. (c) Even harmonics in these ranges shall be <25% of the odd harmonic limits listed. Table 3 Distortion limits as recommended in IEEE Std Odd Harmonics Maximum Harmonic Current Distortion 3rd -9 th 4.0% 11th -15 th 2.0% 17th -21 st 1.5% 23rd -33 rd 0.6% Above the 33 rd 0.3% Voltage step change The process of starting a medium scale distributed generation (MSDG) can sometimes cause step changes in voltage levels in the distribution network. These step changes are caused by inrush currents, which may occur when transformers or induction generators are energised 17 P a g e

22 from the network. Step voltage changes will also occur whenever a loaded generator is suddenly disconnected from the network due to faults or other occurrences. Step voltage changes caused by the connection and disconnection of generating plants at the distribution level should not exceed +/- 3% for infrequent planned switching events or outages and +/-6% of the nominal voltage of 22kV for unplanned outages such as faults Surge Withstand Capability The interconnection system shall have a surge withstand capability, both oscillatory and fast transient, in accordance with IEC The design of control systems shall meet or exceed the surge withstand capability requirements of IEEE C Voltage and Current Unbalance The contribution to the level of unbalance of the voltage at the point of common coupling of any installation with generation should be less than or equal to 1%. 4.5 Ramp Rate Limits MSDG greater than and equal to 1MW shall have ramp up/down capability for all ranges of operation including positive ramp rate during start up, positive ramp rate only during normal operation and negative ramp rate during shut down of the MSDG facility. The MSDG shall have two ramp rates a) 10 minute maximum ramp rate (Installed Capacity divided by 1.5) b) 1 minute maximum ramp rate (Installed Capacity divided by 5) The ramp rate averaged over one minute should not exceed 3 times the average ramp rate over 10 minutes. The ramp rate settings shall be approved by CEB prior to testing and commissioning of the system on the network. For any subsequent change, a minimum of two weeks notice shall be given. Implementation by the Promoter shall be done within two weeks of formal request. 18 P a g e

23 CHAPTER 5: Testing and Commissioning 5.0 Introduction The Applicant shall notify the CEB in advance of the testing and commissioning as per IEC norms. The Applicant shall keep written records of test results and protection settings. The Applicant shall regularly maintain the protection systems in accordance with good electrical industry practice. The interconnection protection of the MSDG shall be regularly tested by the owner. In addition, it may be necessary to perform tests on ad-hoc basis for purposes such as ascertaining level of harmonic emissions, voltage rise, protection operation in the context of system changes, fault investigation and protection changes etc. 5.1 Testing and Commissioning The Applicant shall submit appropriate testing and commissioning procedures and plans as per IEC norms for the MSDG Facility to CEB for approval at least 3 (three) months prior to the Schedule Commercial Operation Date of the MSDG Facility Testing Phase A number of typical tests among others for PV and WTG MSDG Facility have been identified by the CEB in this Grid Code. However it is the responsibility of the MSDG owner to ensure that all required tests are performed to ensure compliance with this grid code. The tests identified are as follows: a) Photovoltaic facility Earthing continuity of array frame to earth and connection to main earthing terminal Polarity of each module string PV string Open-Circuit Voltage (Voc) Test; PV Short Circuit current (Isc) Test; PV array insulation Test; Operational Test PV string current; Functional Test; Irradiance Test; Insulation resistance Testing; and Performance verifications; b) Wind TG Facility 6 hour test run with the generator connected to the grid Demonstration of WTG vibration level below acceptable level. Test of trip function when WTG is generation and grid loss occurs Test of over speed trip of each WTG Test of yaw drives Functional test 19 P a g e

24 Performance verification Commissioning Phase The Commissioning tests shall be performed in the presence of the CEB. CEB reserve the right to request the applicant to perform additional tests which CEB may find necessary to ensure integrity of its network. The commissioning of the electrical system shall include at least the followings: a) Demonstration of satisfactory operation of power measurement equipment b) Functional tests of the relay protection and verification of settings c) Demonstration of satisfactory operation of internal reticulation d) Demonstration of satisfactory operation of the transformer cooling equipment in pooling substation. e) Pressure tests on 22kV switchgear f) Reactive Power Capability. g) Power Quality Test as per IEC h) Anti-islanding i) Test of the facility to withstand step load change 5.3 Power Quality CEB will perform tests to ensure that the facility is compliant with Section 4.4 of this Grid Code. 20 P a g e

25 Annex 1 - Abbreviations and Definitions AC means Alternating Current; Applicant means a producer of electricity through an MSDG installation; CEB means the Central Electricity Board; Circuit breaker means a switching device capable of making, carrying, and breaking currents under normal circuit conditions and also making, carrying for a specified time, and breaking currents under specified abnormal conditions such as those of short circuit; DC means Direct Current; DG means Distributed Generation Distributed generation means electric generation facilities connected to the Utility network at the PCC; Flicker means a variation of input voltage sufficient in duration to allow visual observation of a change in electric light source intensity; Fault means a physical condition that causes a device, a component, or an element to fail to perform in a required manner, for example a short-circuit, a broken wire, an intermittent connection; Frequency means the number of complete cycles of sinusoidal variations per unit time; Grid means CEB s network that brings electricity from power stations to consumers THD means Total Harmonic Distortion Harmonic distortion means continuous distortion of the normal sine wave; typically caused by nonlinear loads or by inverters, measured in Total Harmonic Distortion (THD); Islanding means a condition in which a portion of the CEB s network is energised by one or more MSDGs through their PCC(s) while electrically separated from the rest of the system; Isolated Generation means a condition where the electrical path at the PCC is open and the MSDG continues to energise local loads; kv means kilovolt; kva means Kilovolt Ampere kw means Kilo Watt (1,000 W = 1,000 J/s); kwh means Kilowatt hour (1,000 watt hours); 21 P a g e

26 LV means Low Voltage (refers to systems normally operating at a voltage not exceeding 1000 volts A.C. or 1500 volt D.C.); HT means High Tension (refers to systems normally operating at a voltage exceeding 1000 volts A.C. or 1500 volt D.C.) HV means High Voltage (see HT ) MW means megawatt (1,000,000 W = 1,000,000 J/s); Parallel operation means a condition where the MSDG is operating while connected to CEB s network; PCC means point of common coupling; Point of Common Coupling (PCC) means the point at which an MSDG is connected to the CEB s network Power factor means ratio of real to total apparent power (kw/kva) expressed as a decimal or percentage; Producer means a producer of electricity through any MSDG installation or the owner thereof; PV means photovoltaic; RE means renewable energy; MSDG means Medium Scale Distributed Generation greater than 200 kw up to 2000 kw SWC means Surge Withstand Capability, the immunity of this equipment to fast and repetitive electrical transients; 22 P a g e

27 Annex 2 - CEB Feed-In-Tariff Tariff, if applicable, will be determined subject to discussion with the CEB. However for MSDG projects designed to meet their own local consumption, a charge may be applicable. 23 P a g e

28 Annex 3 - CEB Fees Interconnection facility and cost The MSDG will be connected to CEB 22kV network through a Medium Voltage switchgear and metered on the medium-voltage side. In addition, the applicant shall bear fees for processing applications and preparation of cost estimate for network construction or modification as shown below. Fees for processing of application: Processing of the Application Rs 375 Connection Fees: Connection for Three Phase Rs 3,000 Engineering Review/ Distribution Study Preparation of estimate for network modification Rs 25,000 Revision of Estimate Rs 3,000 System Impact Study Fee Rs ** Network construction / modification The cost for network construction or modification will be determined after carrying out the engineering review. ** A system impact study will be performed for all MSDG projects to ensure safe integration on the network. The applicable fee will be determined on a case-to-case basis. 24 P a g e

29 Annex 4 - Application Form CENTRAL ELECTRICITY BOARD Serial No. (For office use only) Application Form to be filled and forwarded together with processing fee to the MSDG Unit, Corporate Planning & Research Department, CEB Head Office, Royal Road, Curepipe before 15.15Hrs, the closing time of CEB s cash offices. Tel: Fax: Note: No parts of this application form shall be modified upon submission. Incomplete submission of information will entail delays in processing your application Medium Scale Distributed Generation (above 200 kw up to 2000 kw) Application Form 1.0 Applicant Information Name of Applicant / Company Name & Title of Contact Person (if applicable) For office use only 1.3 Postal address 1.4 Contact telephone number Office:. Mobile: 1.5 Fax number 1.6 Tax Account Number VAT Registration Number (if applicable) Business Registration Number (if applicable) 1.9 address 25 P a g e

30 2.0 Installer details Name of Installer 2.2 Accreditation/qualification 2.3 Postal address For office use only 2.4 Contact person 2.5 Telephone number 2.6 Fax number 1 At the start of this project until further notice, the CEB shall accept a Certificate from the supplier of the equipment certifying that the installer is well-versed with the installation of the equipment. Furthermore, the topics covered and the duration of the training shall be mentioned on the Certificate. 3.0 Project details For office use only 3.1 Site/project address Telephone number (project site) Business Partner Number (please refer to your electricity bill or alternatively attach a recent electricity bill) 2 Contract Account Number (please refer to your electricity bill or alternatively attach a recent electricity bill) 2 Expected installation commencement date Expected commissioning date 2 If not available, to submit the following together with the application form a) Copy of the Business Registration Card b) Copy of Certificate of incorporation c) Copy of Identification Card d) A letter of Power Attorney (if applicable) 26 P a g e

31 4.0 MSDG details For office use only 4.1 MSDG location within the installation To submit site and location plan Type of RE technology (photovoltaic/ hydro/ wind/biomass) Type of generator (synchronous/induction/ inverterbased) Total number of MSDG units to be installed under this project, to include MSDG installation capacity in kw and kva To submit manufacturer data sheet To submit manufacturer data sheet No. of Units:..of kw each Total kw: Total kva:. 4.5 Expected annual generation (kwh) 4.6 Any other SSDG/MSDG on installation site (Yes/No) If yes, to specify Total kw : Total kva : 5.0 Other information to be submitted 5.1 Type test certificate of RE technology (photovoltaic/ hydro/ wind/biomass) thereon including the following information: Manufacturer and model type For office use only Country of origin 5.2 Standard of compliance 3 Contact details of Certifying Laboratory telephone number, web address etc Type test certificate of generator (synchronous/induction/ inverter-based) thereon including the following information: Manufacturer and model type Country of origin MSDG current rating (A), voltage rating (V), rated power factor and frequency (Hz) Maximum peak short circuit current (A) Standard of compliance 3 Contact details of Certifying Laboratory telephone number, web address etc 27 P a g e

32 Other information to be submitted (Cont.) For office use only Copy of system circuit diagram (single line diagram) within the installation including the proposed grid connection and the associated metering points/ supply points Single Line Diagram illustrating the protection schemes of the MSDG (including relay positioning, protection functions and related circuit breaker) 5.5 Earthing arrangements (Single Line Diagram) 5.6 Site layout plan showing location of MSDGs and other major electrical equipment installed including the Joint Use Facility 5.7 Procedures for the isolation of MSDG installation Complete sequence of operations: (a) In normal mode (b) Upon loss of mains (operation of MSDG protections; changeover sequence; starting of standby sets; interlocking between changeover & MSDG; where is decoupling performed) (c) On restoration of grid power Complete set of specifications of the equipment to be used in the Joint Use Facility (busbar, isolators, circuit breakers, enclosure, etc ) 3 All MSDGs to submit certificate of compliance with the Electrical Equipment Safety Regulations and the Electromagnetic Compatibility Regulations (CE Marked). PV installations to submit certificates that the panels are to IEC for crystalline silicon and IEC for thin film silicon. Wind installations to submit certificates that the wind turbine is as per IEC P a g e

33 MSDG Guaranteed Particulars (All information given hereunder should be substantiated by documents from the Manufacturer) 6.0 MSDG Guaranteed Particulars Required settings Item. Protection Parameters Settings Clearance No. Trip Setting Time 6.1 Over Voltage (22kV + 10 %) 24.2 kv 0,2 s 6.2 Over Voltage (22kV + 6 %) 23.3k V 1,5 s 6.3 Under Voltage (22kV 6 %) 20.7 V 1,5 s 6.4 Over Frequency (50 Hz + 2 %) 51 Hz 0,5 s 6.5 Under Frequency (50 Hz - 6 %) 47 Hz 0,5 s 6.6 Loss of Mains(df/dt - Vector 2.5 Hz / s shift) 10 degrees 0,5 s To specify System settings Trip Trip Clearance Indication Setting Time Provided 6.7 Islanding Detection Yes 6.8 Isolated Generation possible Yes / No 6.9 Reconnection Time 3 minutes 6.10 Rated AC output Current per phase To specify 6.11 Total Harmonics Distortion (Voltage) at PCC To specify 6.12 Total Harmonics Distortion (Current) at PCC To specify 6.13 Surge Withstand Capability (kv) To specify 6.14 Power Factor (leading & lagging) Will Production Meter be installed? Yes / No 6.16 Will a Backup Meter be installed? Yes / No Will Battery Storage be Installed? If yes, to specify purpose. Fault-ride through capability (in case of inverter-based) Documentation on relays to be used on lowvoltage side Yes / No Yes / No To submit 6.20 Likely load profile and generation profile To submit 6.21 Is inverter equipped with Maximum Power Point Tracking (MPPT) (in case of inverter) Yes / No 6.22 Will a technical staff be available on a round the clock basis with whom CEB can communicate whenever required? Yes / No 29 P a g e

34 7.0 Interconnection Transformer Details Item. No. Parameter Value 7.1 Rated voltage (HV/LV) 7.2 Rated Power (MVA rating) 7.3 Positive sequence impedance in % 7.4 Zero sequence impedance in % 7.5 Positive sequence losses in kw 7.6 No load losses in kw 7.7 No load current in % 8.0 Inverter details ( The table must be filled in for each type of inverter) Item. No. Parameter Value 8.1 Make 8.2 Model 8.3 Rated Apparent Power /kva 8.4 Number of inverters 8.5 Rated output voltage (V) 8.6 Power factor range of operation 8.7 Inverter efficiency at full load (%) 8.8 Total Harmonic Distortion (THD) (%) 9.0 Synchronous Generator Details Item. No. Parameter Value 9.1 Nominal apparent power (MVA) 9.2 Nominal voltage (kv) 9.3 Power factor 9.4 Connection (Star or delta) 9.5 Direct axis synchronous reactance, xd (p.u) 9.6 Quadrature axis synchronous reactance, xq (p.u) 9.7 Zero sequence reactance, x0 (p.u) 9.8 Zero sequence resistance, r0 (p.u) 9.9 Negative sequence reactance, x2 (p.u) 9.10 Negative sequence resistance, r2 (p.u) 9.11 Transient reactance, xd (p.u) 9.12 Sub transient reactance (saturated value), xd sat (p.u) 9.13 Stator resistance, ratio X/R 9.14 Inertia constant, H 9.15 Time constant, T d 9.16 Time constant, T d 30 P a g e

35 10 Induction Generator Details Item. No Parameter Value 10.1 Nominal apparent power (MVA) 10.2 Nominal voltage (kv) 10.3 Rated apparent power (kva) 10.4 Nominal frequency (Hz) 10.5 No. of pole pairs 10.6 Connection (Star or delta) 10.7 Rotor (single or double cage) 10.8 Stator resistance, Rs (p.u.) 10.9 Stator reactance, Xs (p.u.) Magnetising reactance, Xm (p.u.) Rotor leakage reactance, Xl (p.u.) Operating Rotor resistance, RrA (p.u.) Operating Rotor reactance, XrA (p.u.) Starting cage rotor resistance, RrB (p.u.) Starting cage rotor reactance, XrB (p.u.) 11.0 Declaration to be completed by applicant* Comments (use separate sheet if necessary) (a) I declare that this installation will be designed to comply with the requirements of CEB. (b) I declare that I shall adhere to the Grant of Permit and Proclamation procedures for MSDG installation as shown in Chapter 2 (c) I declare that I have been informed by the CEB that 1) The tariff, if applicable, for the energy sold to the CEB by the proposed MSDG installation will be determined subject to discussion with the CEB. 2) A charge may be applicable if the MSDG project has been designed to meet my own local consumption. Name (BLOCK LETTERS): Signature: Date: * This field is mandatory to complete before submission. 31 P a g e

36 Annex 5 - Certificate of Installation Applicant/installer to submit duly signed certificate (as shown below) to the CEB. CERTIFICATE OF INSTALLATION I hereby certify that the installation of the MSDG of capacity.kw, situated at (address) for (name of Applicant) has been done as per the requirements of the GRID CODE FOR MEDIUM SCALE DISTRIBUTED GENERATION (MSDG) Greater than 200kW but not exceeding 2MW and as per attached detailed schematic diagram. Name (BLOCK LETTERS) of Qualified Installer:..... Signature of Installer:.... Date:.... Name (BLOCK LETTERS) of Applicant:..... Signature of Applicant:... Date:. 32 P a g e

37 Annex 6 - Certificate of Compliance Prior to commissioning, the CEB will issue a Certificate of Compliance to the applicant. Certificate of Compliance This is to certify that on [date] the MSDG installation with an installed capacity of.kw, situated at [address] in the name of [Applicant name]bearing Serial No. [ ]has been found compliant with the requirements of the MSDG Grid Code by the Representatives of the CEB Sections found hereunder and it has been found to be fit for the connection to the Grid. The installation shall be commissioned after the signature of the Connection Agreement and the Publication of the Proclamation. Representative of Distribution Network Name (Block Letters):. Signature:.. Representative of Meter Installation Name (Block Letters)::. Signature:. Representative of MSDG Unit Name (Block Letters)::... Signature:.. Representative of Health and Safety Officer Name(Block Letters)::.. Signature:.. Date: P a g e

38 Annex 7-22KV Switchgear Arrangement CEB Incoming Feeder (1) VT for Metering & Protection (2) Circuit Breaker with double Sectionaliser and CTs for protection and metering (3) CT and PT for Seller Back Up metre (Optional) (4) Circuit breaker (5) A CB1 CB2 CEB MSDG Owner CEB Incoming Demarcating wall or fence CB3 Circuit breakers CB1 MV Interconnection circuit breaker CB2 MV Transformer circuit breaker CB3 LV Main circuit breaker CB4 LV Interconnection circuit breaker CB5 Generator circuit breaker GS CB4 CB5 Synchronous generator/ induction gen./inverter Essential load Non-essential load 34 P a g e

39 Annex 8 - Interconnection Facility Description A.1 Responsibility and Cost of Installation of Interconnection Facilities: (1) CEB shall be responsible for the construction, installation and commissioning of the 22kV network forming part of the CEB Interconnection Facilities. CEB shall own and be responsible for the operation, maintenance and repair of the CEB Interconnection Facilities. (2) For installation of 1MW and above the applicant shall be responsible for the acquisition of the right of way for CEB with regard to the interconnection 22kV line with CEB 22 kv existing network. (3) The Applicant shall be responsible for the construction, installation, testing and commissioning of the complete 22kV switchboard as per Annex 7, i.e. the CEB as well as the MSDG side. CEB will take ownership of its side after the guarantee period. (4) The Applicant shall bear the cost of the procurement, installation, testing and commissioning of both CEB and MSDG s Interconnection Facilities. (5) The Applicant shall be responsible for all civil works inclusive of cable trench, drawpits, laying of PVC pipes and construction of switchgear room as per CEB specifications (see Annex 14). All Civil Works shall be approved by the CEB prior to implementation. (6) The Applicant shall own and be responsible for the operation, maintenance and repair of MSDG s Interconnection Facilities. A.2 CEB Interconnection Facilities A2.1 Scope of CEB Interconnection Facilities The CEB Interconnection Facilities shall include the following: A Arrangement of Cubicles under CEB s responsibility The cubicles under Central Electricity Board s responsibility and those under the Applicant s responsibility shall form one single switchboard. However, Central Electricity Board s liability shall stop at the point of delivery found at the incoming terminals, denoted (A) in Cubicle 3 referred as both the Point of Delivery and the Circuit Breaker 1 (See to Annex 7 - ). The switchgear room shall be equipped with air conditioner (A/C) units. The Applicant shall install a metallic demarcation barrier between CEB Circuit Breaker panel and client incoming panel. These demarcation barriers shall be installed at the front and back of the switchgear panels. The height of the demarcation barrier shall be from floor to roof level. The fixation points shall only be accessible from the CEB side of the building. In addition the switchgear room and the meter cabin shall be equipped with fool-proof padlocking facilities (see Annex 14). 35 P a g e

40 The Applicant shall submit all relevant data as illustrated in schedules A.3 A.6 in Annex 8 for approval prior to ordering. CEB shall require all test certificates/ documents before commissioning the HV switchgear panels. a) CEB Interconnection Cubicles 1 The 22kV Incoming Feeder Cubicle shall comprise the following basic equipment:- 1- Three-phase 400A busbar 1- Load-break switch disconnector of rating 400A and housed in SF6 filled enclosure having padlocking facilities. 1- Manual spring charged operating mechanism for quick closing and opening independent of the operator 1- Earthing switch located in such a position to allow its contacts to be seen easily through the cubicle window 1- Mechanical interlocking system between disconnector and earthing switch 1- Neon lamp for live cable indication 1- Cable compartment with cable terminations for the reception of 3-core aluminium 240mm² or copper 300 mm² XLPE cable to IEC Thecable entry is to be at the front of the panel 1- Bottom plate with cable gland 1- Built-in padlocking device of the cubicle door The front facia should be equipped with appropriate padlocking facilities that will allow the operator to lock the disconnectors witch and earth-switch in close/open position independently. b) Voltage Transformer Cubicle 2 The 22 kv Voltage Transformer Cubicle shall comprise the following basic equipment:- 1- Three-phase 400 A busbar 1- Triple pole isolator 1- Manual operating mechanism 3- HRC fuses to DIN specifications rated to suit VT s rating 1- Auxiliary switch connected to the VT secondaries and opening with the 22 kv isolator to prevent feedback from the LV side 3- Single phase voltage transformers:- Metering core Ratio: : Rated burden : 50 VA Accuracy Class : CL P a g e

41 Protection core Ratio: : 110 or 110 depending on star/delta Rated burden : 30 VA Accuracy Class : 3P Burden Range : Rated burden at 0.8 p.f Primary voltage range : Vf rated primary voltage Rated voltage factor Vf: : 1.9 Time rating (for Vf) : 30 s 1- LV fuse box containing 3 LV fuses + 3 neutral links 1- Built-in padlocking facility on the cubicle door c) Circuit breaker Cubicle No.3 The circuit breaker shall be of double isolation and comprise the following basic equipment 1- Three-phase 400 A busbar 2- Triple pole isolator 1- SF6 Gas Circuit Breaker 1- Motor operated spring charging mechanism for quick closing and opening both locally by push button and remotely. 1- Closing coil voltage to harmonise with auxiliary supply of MSDG installation. 1- Spring charging motor voltage to harmonise with auxiliary supply of MSDG installation. 1- Tripping coil voltage to harmonise with auxiliary supply of MSDG installation. 1- Trip release device to work in conjunction with the relay mentioned below 2- Current transformers with dual primaries of 50/100 rated amp with secondaries of 5A, Class 5P10, 15 VA burden for protection and two separate cores of 5A Class 0.2, 15 VA burden for main and back up metering 1- Voltage test terminal box 1- Mechanical interlocking between earthing switch and triple pole isolator 1- Earthing switch located in a position to allow its contacts or position to be seen easily preferably through the cubicle window 1- Bottom plate with cable gland 1- Neon lamp for live cable indication 1- Built-in padlocking device for the cubicle door The front facia shall be equipped with appropriate padlocking facilities that will allow the operator to lock the disconnector switch and earth switch in close/open position independently. A key interlocking system shall be provided for the safe operation of the 22kV switchgears. Note: The current and voltage transformers have to be removed and sent to CEB Meter Laboratory for necessary tests before commissioning. Toroidal CTs WILL NOT BE ACCEPTED for metering purpose 37 P a g e

42 d) Degree of Protection IP 3X. e) Safety equipment for switching operations Client should provide the following safety equipment:- i) 22 kv insulating mat ii) One pair of 22 kv insulating gloves. Specification of the equipment shall be approved by the CEB prior to ordering f) Spares The client shall provide the following spares for the cubicles that shall be under Central Electricity Board s responsibility:- 1 set Voltage Transformer as specified in item (b). 1 set Current Transformer as specified in item (c). 1 set HRC fuses as specified in item (b) g) Standards The switchboard shall conform to the following standards or the relevant parts thereof: - (i) IEC 129 : AC Disconnectors (Isolators) and Earthing Switches (ii) IEC 265 : HV Switches (iii) IEC : HV Metal-Enclosed Switchgear and Control Gear (iv) IEC 282 : High Voltage Fuses (v) IEC 420 : HV AC Fuse Switch combination and Fuse Circuit Breaker combinations 38 P a g e

43 SCHEDULE A.3 INCOMING FEEDER PANEL Item No. Description Units Value 1. Rated Voltage kv 2. Rated Current A 3. Rated short time current, IS ka(rms) 4. Making Capacity kapeak 5. Arc quenching medium e.g.sf6 To specify 6. Is double or single break? To specify 7. Type of operating mechanism(manual spring charged; manual) 8. Minimum clearance: (a) Between phases (b) Live part to earth 9. Type of design contacts: (a) Movable contacts (b) Fixed contacts 10. Type of metal used for contacts: (a) Movable contacts (b) Fixed contacts 11. Padlocking facility to allow locking of disconnector and earth switch in close/open positions independently To specify mm mm To specify To specify Yes/No Name of Supplier(s): Contact Person: Phone No:.... Signature of authorised signatory:. Position of authorised signatory:... Name of authorised signatory:.... Date: Company Seal(Mandatory) 39 P a g e

44 SCHEDULE A.4 VOLTAGE TRANSFORMER PANEL Item No. Description Units Value 1. Rated Voltage kv 2. Rated Current A 3. Type of Disconnector To specify 4. Type of operating mechanism of Disconnector To specify 5. Standard of HRC fuselinks To specify Voltage Transformer:- (a) Number of units installed (b) Type (c) Model/Make (d) Burden (e) Rated primary voltage (f) Rated secondary voltage (g) Accuracy class (h) Transformation ratio (i) Rated thermal output Padlocking facility to allow locking of disconnector and earth switch in close/open positions independently VA kv V VA Yes/No Name of Supplier(s): Contact Person: Phone No:.... Signature of authorised signatory: Position of authorised signatory :... Name of authorised signatory:.... Date: Company Seal(Mandatory) 40 P a g e

45 SCHEDULE A.5 OUTGOING FEEDER/METERING PANEL Item No. Description Units Value 1. Rated Voltage kv 2. Rated Current A 3. Rated short time current, IS ka(rms) 4. Making Capacity kapeak 5. Arc quenching medium e.g. SF6 To specify 6. Is double or single break? To specify Type of operating mechanism(manual spring charged; Minimum clearance:- (a) Between phases To specify mm mm Type of design contacts:- (a) Movable contacts Type of metal used for contacts:- (a) Movable contacts To specify (b) Fixed contacts Padlocking facility to allow locking of disconnector and earth switch in Yes/No Current Transformer:- (a) No. of CT provided (b) Type (c) Model/Make (d) Burden for protection (e) Burden for metering (f) Accuracy class for protection (g) Accuracy class for metering (h) Rated primary current (i) Rated secondary current VA VA A A Name of Supplier(s): Contact Person: Phone No:.... Signature of authorised signatory: Position of authorised signatory:... Name of authorised signatory :.... Date: Company Seal(Mandatory) 41 P a g e

46 SCHEDULE A.6 COMPLETE SWITCHBOARD Item No. Description Units Value 1. Rated Voltage k 2. Impulse test voltage 1,2/50µs A 3. Rated short time current-is ka1sec 4. Electrodynamic withstand kapeak 5. Type of busbars(copper/aluminium) 6. Are busbars insulated? Yes/No 7. Busbar Rating A 8. Degree of Protection I 9. Colour of switchboard Dimensions of assembled:- (i) Length (ii) Depth (iii) Height switchboard when Reference of IEC standards to which switchboard complies with m m m m To specify Name of Supplier(s) : Contact Person: Phone No:.... Signature of authorised signatory : Position of authorised signatory :... Name of authorised signatory: :.... Date: Company Seal(Mandatory) 42 P a g e

47 Annex 9 - Interconnection Transformer Specifications (a) Characteristics of the Interconnection Transformer No. of phases 3 High voltage side Low voltage side Frequency Type Cooling Construction 22 kv As per MSDG low voltage 50 Hz Oil immersed, hermetically sealed, nongas cushion * Natural Core type double wound or shell type Vector Group Dyn 11 Winding Enamelled Copper Wire Standard IEC * Customers wishing to purchase cast resin transformers (for indoor use), should submit all detailed characteristics of the proposed units including Type Test Report from an independent and recognised institution. (b) Other Requirements The transformer shall be:- 1. Supplied with oil as per specifications contained in Schedule B.2 Mineral Insulating Oil for Transformers and Switchgear. 2. Fitted with:- (a) Oil level indicator (b) Oil filling hole with plug (c) Lifting lugs (d) Earthing terminal for tank (e) Drain plug with sampler cock (f) Diagram and rating plate (g) Terminal marking plate (h) Off-circuit tap changer with ± 2 ½% and ± 5% taps (as per the above mentioned standard) 3. Supplied with detachable top yoke to allow removal of windings for repairs. 4. Externally hot dip galvanised to BS EN ISO Designed for ground mounting with rollers. 6. Designed with a bolted cover. 7. Designed with the following terminations:- 43 P a g e

48 (a) HT side - 3 plug-in type bushings rated 200A, 24 kv suitable for the reception of elbow plug-in connector (not to be supplied) (b) LT side - 4 bushings and associated copper cable terminals having the following characteristics:- (c) Standards i. be of vertical type. ii. bottom part to be threaded onto the bushing rod and tightened by two side bolts. iii. have a top palm, undrilled The transformer shall conform to the following standards:- i) IEC Power Transformers ii) BS EN ISO Hot dip galvanised coatings on fabricated iron and steel articles (specifications and test methods) Note: All specifications shall be according to the latest edition of the standards mentioned above. (d) Guaranteed Particulars The Applicant shall submit all relevant data as illustrated in schedules B.1 in Annex 9 prior to ordering. CEB shall require all test certificates/ documents before commissioning the interconnection transformer. 44 P a g e

49 SCHEDULE B.1 INTERCONNECTION TRANSFORMER Item No. Description Units Value 1. Continuous maximum rating (CMR) At rated voltage with ONAN cooling kva 2. Is transformer totally oil-filled with no gas cushion? Yes/No 3. Current rating Amps H.V L.V A 4. Winding connection Vector Group Symbol 5. Impedance Voltage % 6. Normal ratio of transformation at no load 7. Total range of variation of transformation ratio ±% 8. Size of steps % 9. Tappings on H.V. winding Yes/No 10. Regulation at75 C and at full load as percentage of normal voltage (a) At unity p.f. (b) At 0.8p.f.lagging 11. Fixed losses at normal ratio and 75 C kw 12. Load losses at normal ratio and 75 C At full rated power 13. Ratio on Inrush Current to Primary Current at 0.3 sec after energising transformer % % kw 14. Efficiencyatnormalratioand75 Cat: (a) Rated power at unity powerfactor (b) Rated power at 0.8 powerfactor (c) Natural circulation rating 15. Winding temperature:- Hottest spot temperature at full rated power(assuming an air temperature at 32 C approx.) % % % C 45 P a g e

50 Item No. Description Units Value 16. Maximum observable top oil temperature at:- (a) Full rated power (assuming an air temperature at 32 C approx. ) (b) Natural circulation rating (assuming an air temperature 32 C approx. ) 17. Calculated ONAN thermal time constant 18. Type of transformer shell or core 19. Type of core joint-butt or mitred 20. Type of core sheet-cold rolled or hot rolled 21. Maximum current density in windings:- H.V. L.V. 22. Whether special surge protection is provided in conjunction with modified endturn reinforcement ºC ºC Hrs kasq.m kasq.m Yes/No 23. Type of axial coil supports:- (a) H.V. winding (b) L.V. winding 24. Type of radial coil supports:- (a) H.V. winding (b) L.V. winding 25. Can winding be removed for repairs? 26. Total quantity of oil required to fill complete transformer 27. Standard specifications of oil used for filling transformer 28. Is transformer externally hot dip galvanised? 29. Required for each transformer:- (a) Weight of copper(w) (b) Weight of cores heets (c) Weight of all other ferrous parts 30. Approximate weight of core and winding assembly Yes/No kg kg kg kg 46 P a g e

51 Item No. Description Units Value 31. Total weight of transformer complete as in service 32. Approximate dimensions of transformer incl. all fittings:- (a) Length (b) Breadth (c) Height 33. Windings:- (a) Type of winding - H.V. L.V (b) Wire size - H.V. L.V. kg mm mm mm (c) Type of wire insulation (d) Number of coils per winding (e) Number of turns per coil (f) Number of layers per coil (g) Number of turns per layer mm (h) Type of insulation between layers (i) Thickness of insulation between layers (j) Turn numbers in tapping coils (k) Total length of winding (l) Winding & clearances from yokes (m) Inter phase winding clearance (n) Total weight of copper per phase (o) Limb diameter Limb length Limb centre distance mm mm mm kg mm mm mm mm Name of Supplier(s): Contact Person:.Phone No:.... Signature of authorised signatory : Position of authorised signatory :... Name of authorised signatory :.... Date: Company Seal(Mandatory) 47 P a g e

52 Annex 10 - Mineral Insulating Oil For Transformers The insulating oil shall be for use in transformers and shall comply to IEC and or equivalent. The oil shall be free of PCB and be of such quality that it shall not require any user precautionary labelling as defined by the EEC Dangerous Substances Directive 67/548/EEC. The polycyclic aromatic content by IP 346 shall be maintained below 3%. GUARANTEED PARTICULARS The Applicant shall submit all relevant data as illustrated in schedules B.2 in Annex 10 prior to ordering. CEB shall require all test certificates/ documents before commissioning the interconnection transformer. 48 P a g e

53 SCHEDULE B.2 MINERAL INSULATING OIL FOR TRANSFORMER SWITCHGEAR Item No. Description Units Value 1. Sludge Value (max.) % 2. Acidity after oxidization (max.) mgkoh/g 3. Flashpoint(closed) min. ºC 4. Viscosity:- (a) At 15ºC(max.) (b) At 20ºC (max.) mm²/s mm²/s 5. Pour point (max.) ºC 6. Electric strength(breakdown)min. for oil received in Mauritius in drums KV/mm 7. Acidity (neutralization value) max. mgkoh/g 8. Corrosive sulphur 9. Water content (max.)for oil received in Mauritius in drums p.p.m. 10. Densityat20ºC(max.0 G/ml 11. Losstangentat90ºC (max.) 12. Resistivity 13. Polycyclic aromatic content(ip346) % 14. Polychlorinated Biphenyls (mg/kg) 15. Reference of standard specifications 16. Are any precautions to be taken incompliance with the EEC Dangerous Substance Directive 67/548/EEC? Yes/No Name of Supplier(s): Contact Person: Phone No:.... Signature of authorised signatory: Position of authorised signatory :... Name of authorised signatory:.... Date: Company Seal(Mandatory) 49 P a g e

54 Annex 11 - Typical Medium Voltage Switchgear Panel and Protection Arrangement Inter-trip signal from CEB CEB MSDG Owner CB2 Trip CB1 A CB Aux. Contact Interconnection transformer CEB Incoming 59N 50/ 51 50N/ 51N 50N/ 51N 50/ 51 CB3 Customer s LV busbar Interconnection Protection (Short-circuit protection) LoM CB4 kwh Meter 81 O/U Trip Close Customer s Non-essential load Protection functions 81 O/U Over and Under Frequency 27 Under Voltage 59 Over voltage 59N Neutral Voltage Displacement 50/51 Instantaneous Over current and earth fault 50N/51N Instantaneous Over current and earth fault 25 Synchronism Check LoM Loss of Mains: RoCoF and Vector Shift Circuit breakers CB1 MV Interconnection circuit breaker CB2 LV Main circuit breaker CB3 LV Interconnection circuit breaker CB4 Generator circuit breaker Interconnection Protection (Anti-islanding) CB5 Generator Protection and synchronisation GS Synchronous generator/ induction gen./inverter Customer s Essential load 50 P a g e

55 Interconnection protection Annex 12 - Protection Specifications The short circuit protection relay shall have the following characteristics i. The relay shall comprise an earth fault (EF) protection, at least two over current (OC) protection and neutral voltage displacement (NVD) protection. ii. For the EF and OC functions, the relay should comprise the following functions: - Inverse Definite Minimum Time Normal Inverse (NI), Very Inverse (VI), Extremely Inverse (EI) - Definite Time (DT) - High Set Instantaneous elements iii. The setting ranges should be as follows: a. Start current (overcurrent) - At definite time: x In and high set x In & - At Inverse time: x In with time multiplier Operating time at Definite Time: s b. Start current (earth fault) - At Definite time: x In and high set x In & - At inverse time: x In with time multiplier Operating time at Definite time: s iv. The NVD protection function is activated if the residual voltage V0 is greater than a threshold voltage Vr and incorporates a definite time delay T. The residual voltage is either obtained by calculation from the three phase voltages or measured using an external voltage transformer. Note that the voltage transformers used for the purpose of NVD protection need to be of single phase type connected in star on the primary side and star or delta on secondary. a. Threshold voltage, Vr Range: From 2 % of Unp to 80 % Unp Precision: ±2 % or ±0.005Unp Resolution: 1 % Where, is the line voltage of 22 kv b. Clearance time Range: 0 s to 300 s Precision: ±2 % or ±25ms Resolution: 10 ms or 1 digit These shall operate without auxiliary supply, with independent time settings for each type of protection as detailed hereunder. 51 P a g e

56 Patch panels Patch panels Annex 13 - Communication Requirement Transducer MW analog inputs analog outputs Mvar kv 4-20mA signals 4-20mA signals CB positions digital inputs digital outputs & alarms Optical Optical potential free contacts Converter Converter for CB positions and alarms Existing substation RTU optical fibres single mode ST connectors CB open digital outputs digital inputs CB closed commands power supply power supply customer premises CEB substation Figure A - 1 Communication channel setup 52 P a g e