Inspection and Testing Guidelines for Solar PV Systems PDF

CS-CSI-P3/G2 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network Pubic Page 1 of 58  Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network...

CS-CSI-P3/G2 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network Pubic Page 1 of 58  Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 Table of Contents Contents Page Title Page 1 Document Control & Issue Record Page 2 Table of Contents 3 1 Purpose 7 2 Scope 7 2.1 Notice to Users of these Guidelines 8 3 Abbreviations, Definitions of Terms & Key References 8 4 Types of Tests and Responsibilities 16 4.1 Off-line Tests and Commissioning Test 16 4.2 Responsibilities in Inspection and Testing 16 4.2.1 Inspection and Witnessing the Test arranged by the Contractor 17 5 Tests Methodology and Documentation 17 5.1 Test Methodology 17 5.2 PV System Documents Required during the Inspection 18 6 Safety issues 18 6.1 Hazards and Safety Measures 18 6.2 Information from Contractor about Specific Risks on-site and Safety Measures 21 7 Off-line Tests 21 7.1 Overview 21 Public Page 2 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 7.1.1 Basic Tests and Additional tests 21 7.1.2 Special considerations for PV systems with module-level electronics 21 7.2 Common Requirements 22 7.3 Solar PV Systems Inspection 22 7.4 DC System 22 7.4.1 DC system – General Verifications 22 7.4.2 DC system – Verification of the Protection against Electric Shock 23 7.4.3 DC system – Verification of the Protection against the Effects of Insulation Faults 23 7.4.4 DC system –Verification of the Protection against Overcurrent 23 7.4.5 DC system – Verification of Earthing and Bonding Arrangements 24 7.4.6 DC System – Verification of the Protection against the effects of Lightning and Overvoltage 24 7.4.7 DC system – Verification of the selection and erection of electrical equipment 24 7.4.8 Checklist for DC System Verification 25 7.5 Labelling and Fire Protection 25 7.5.1 Labelling and identification 25 7.5.2 Fire Protection Verification 25 7.5.3 Verification of the Special Requirements for Households 27 7.6 Basic Tests 28 7.6.1 Continuity Test of Protective Earthing and Equipotential Bonding Conductors 28 7.6.2 PV string Polarity Test 28 7.6.3 PV string Combiner Box Test 29 7.6.4 Open Circuit Voltage Measurement of PV Strings 29 7.6.5 Current measurement of PV strings 29 7.6.6 Functional Tests 30 Public Page 3 of 58  Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 7.6.7 PV Array Insulation Resistance Test 30 7.6.8 Checklist for the PV Array Tests 32 7.6.9 Earth Resistance of the PV System 32 7.6.10 Infrared Camera Inspection for Inverters and Circuit Breakers 32 7.6.11 Final Result page of the Off-line Test 33 7.7 Additional Tests 33 7.7.1 String I-V curve Measurement 34 7.7.2 PV Array Infrared Camera Inspection Procedure 35 7.7.3 Voltage to Ground – Resistive Ground Systems 36 7.7.4 Blocking Diode Test 36 7.7.5 PV Array – Wet Insulation Resistance Test 36 7.7.6 Shade Evaluation 37 8 PV System Commissioning Test (After Grid Connection) 38 8.1 Scope 38 8.2 Documentation for Commissioning Test 39 8.2.1 Basic System Information 39 8.2.2 Documentation of the PV System 39 8.2.3 Information from Contractor about Specific Risks on-site and Safety Measures 40 8.2.4 Checklists for Verifying the Available Documentation and General Data 40 8.3 Verification of the AC System 40 8.4 Interface Protection 41 8.4.1 Interface Protection Verifications 41 8.5 Performance Monitoring Functions 41 8.6 Data Acquisition, Timing and Reporting 42 8.6.1 Calibration and Inspection 42 Public Page 4 of 58  Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 8.6.2 Sampling, Recording, and Reporting 43 8.7 Measured Parameters 43 8.7.1 General Requirements 43 8.7.2 Electrical Measurements 44 8.7.3 Step and Touch Potential 45 8.7.4 External System Requirements 45 8.8 Data processing and Quality Check 45 8.8.1 Daylight hours 45 8.8.2 Removing Invalid Readings 45 8.8.3 Missing Data treatment and documentation 46 8.9 Calculated Parameters 46 8.9.1 Description of Calculated Parameters 46 8.10 Performance Ratio 48 8.10.1 Overview 48 8.10.2 Performance ratio and Annual performance ratio 48 8.10.3 Temperature-corrected performance ratios 49 8.10.4 STC performance ratio 49 8.10.5 Annual-temperature-equivalent performance ratio 50 8.10.6 Test duration 50 8.11 PV System Commissioning Test Report 51 8.11.1 Final Results of the Commissioning Test 51 8.11.2 Commissioning Test Report 51 9 Kahramaa Inspections 53 9.1 Overview 53 9.2 Site Inspection (PV ≤ 50 kWp) 53 9.3 Kahramaa Inspection and Witnessing the Site Test (PV > 50 kW) 53 Public Page 5 of 58  Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 9.4 Quality Assurance Documents 53 Annex A – Measurement of Environmental Parameters 54 A1. Irradiance 54 A1.1 In-plane irradiance 54 A1.2 Global horizontal irradiance 54 A1.3 Irradiance sensors 54 A1.4 Sensor locations 56 A2. PV module temperature 56 A3. Ambient air temperature 57 A4. Wind speed and direction 58 Public Page 6 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 1 Purpose These guidelines set out the criteria that need to be considered when performing the inspection of a solar PV System to be connected to the distribution network. In order to assess a PV System, a set of checks and verifications shall be passed before connecting it to the distribution network. These checks and verifications are performed through on-site Inspection and Testing of the REG at different stages of construction and vary according to the size of the PV System being installed. 2 Scope This document contains specific guidelines to help the Consumer and his selected Contractor prepare the technical documents required for installing a PV System. This guideline assists the Constructor During the Connection Process to deliver Kahramaa the set of documents, reports and information required during the final steps of the Connection Process. The document highlights the checks and the overall procedure envisaged to perform on-site Inspections and Tests and helps the Consumer and his Consultant/Contractor be aware of the information that Kahramaa expects to find in the various documents required, such as Drawings and Test Reports. During the Inspection, Testing and Energization stage, after the PV System construction is over, the following activities shall take place: REG off-line commissioning of the DC part → Off-line Commissioning Report Activities to be performed by the Off-line Test → Issue of REG off-line Commissioning Contractor of the Report1 Consumer Commissioning Test → Issue of Commissioning Test Report Site Inspection Voluntary Witnessing the Commissioning Test (if PV capacity Activities made ≤ 50 kW) by Kahramaa Mandatory Witnessing the Commissioning Test (if PV capacity > 50 kW) DISCLAIMER The guidelines of this document are valid for all PV Systems and thus represent a minimum set of requirements for testing. The Consultant/Contractor should consider the following guidelines and checklists as a starting point. The Consultant/Contractor may require more detailed tests and can be performed accordingly. 1 The Contractor shall prepare and submit to Kahramaa other relevant documents before applying for the Inspection, as described in the Solar PV Connection Guidelines Public Page 7 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 2.1 Notice to Users of these Guidelines This document is for use by employees of Kahramaa, Consultants, Contractors and Manufacturers. The checklists included in this document are for common use of Kahramaa and the approved Consultants/Contractors. Users of this document should consult all applicable laws, regulations and standards. Users are responsible for observing or referring to the applicable regulatory requirements. Kahramaa does not, by the publication of its standards, intend to urge action that is not in compliance with applicable laws, and these documents may not be construed as doing so. Users should be aware that this document may be superseded at any time by the issuance of new editions or may be amended from time to time through the issuance of amendments, corrigenda, or errata. All users should ensure that they have this document's latest edition uploaded on the Kahramaa website. Finally, unless otherwise specified, the User shall refer to all applicable Kahramaa Standards, Qatar Standards, or International Standards mentioned in this document. 3 Abbreviations, Definitions of Terms & Key References Abbreviations AC : Alternating Current AFCI : Arc Fault Circuit Interrupter ASTM : American Society for Testing BAPV : Building-Attached Photovoltaic and Materials Modules BIPV : Building-Integrated Photovoltaic cos  : Power factor modules DC : Direct Current GHI : Global horizontal irradiance IEC : International Electrotechnical IP : Interface Protection Commission IR : Infrared ISO : International Organization for Standardisation ITP : Inspection and Test Plan LOM : Loss of Mains LV : Low Voltage (namely 220/127 V LVRT : Low Voltage Ride Through or 380/220 V or 400/230 V) MV : Medium Voltage (namely 13.8kV MS : Method Statement or 33 kV) NEC : National Electrical Code NFPA : National Fire Protection Association P : Active power PELV : Protected Extra Low Voltage Pnom : Nominal active power of the POA : Plane of Array equipment PPE : Personal protective equipment PR : Performance Ratio PV : (Solar) Photovoltaic Q : Reactive Power RCD : Residual Current Device ROCOF : Rate of Change of Frequency expressed in Hz/s. S/Sn : Apparent Power SELV : Safety extra-low voltage Public Page 8 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 SPD : Surge Protection Device SR : Soiling Ratio STC : Standard Test Condition UL : Underwriters Laboratories UV : Ultraviolet Vnom : Nominal Voltage WMO : World Meteorological CS : Customer Services Dept Organization Term Description AC Module PV module with an integrated inverter in which the electrical terminals are AC only Active Power Active Power is the real component of the apparent power, expressed in watts or multiples thereof, e.g., kilowatts (kW) or megawatts (MW). In the text, this will be generically referred as P or Pnom in case of the nominal active power of equipment Apparent Power The product of voltage and current at the fundamental frequency, and the square root of three in the case of three-phase systems, usually expressed in kilovolt-amperes (kVA) or megavolt-amperes (MVA). It consists of a real component (Active Power) and the reactive component (Reactive Power). This will be generically referred to S or Sn in case of the rated apparent power of equipment Apparent power of The rated apparent power of an Inverter is the product of the rms voltage an Inverter and current and is expressed in kVA or MVA. Auxiliary Supply Electricity supply for supporting auxiliary systems and services such as Power Interface Protection or circuit breaker and contactor opening coils. Building-Attached Photovoltaic modules are considered to be building-attached if the PV Photovoltaic modules are mounted on a building envelope. The integrity of the building Modules (BAPV functionality is independent of the existence of a building-attached modules) photovoltaic module. Building Attached Photovoltaic systems are considered to be building attached if the PV Photovoltaic system modules they utilise do not fulfil the criteria for BIPV modules. (BAPV system) Building-Integrated Photovoltaic modules are considered to be building-integrated if the PV Photovoltaic modules form a construction product providing a function. Thus, the BIPV modules (BIPV module is a prerequisite for the integrity of the building’s functionality. If the modules) integrated PV module is dismounted (in the case of structurally bonded modules, dismounting includes the adjacent construction product), the PV module would have to be replaced by an appropriate construction product. The building’s functions in the context of BIPV are one or more of the following: mechanical rigidity or structural integrity primary weather impact protection: rain, snow, wind, hail energy economy, such as shading, daylighting, thermal insulation fire protection noise protection separation between indoor and outdoor environments security, shelter or safety Inherent electro-technical properties of PV, such as antenna function, power generation and electromagnetic shielding etc., alone do not qualify PV modules to be building-integrated. Public Page 9 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 Term Description Building-Integrated Photovoltaic systems are considered to be building-integrated if the used PV Photovoltaic system modules fulfil the criteria for BIPV modules. (BIPV system) Circuit Breaker (CB) As per the Kahramaa Electricity and Wiring Code definition Connection Point Also referred to as Point of Connection, is the interface point at which a PV System of the Consumer is connected. Consultant A qualified consultant for the design of grid-connected solar PV Systems. Consumer Any Person supplied with electricity services for his own consumption. In this context, this term will also be used to refer to a User owning a solar PV System. Contractor A certified contractor for the installation of grid-connected solar PV Systems. Delay time (of a Indicates the minimum duration of a fault detected by the protection relay protection relay) before the output of the protection relay is triggered. Delivery Point The interface point at which electrical energy is delivered by Kahramaa to a Demand Facility or Generating Unit or by a Demand Facility or Generating Unit to Kahramaa. Distribution System Qatar electrical infrastructure (lines, cables, substations, etc.) at 33 kV and / Distribution below, operated by Kahramaa. The Distribution network can be either a Network Medium or Low Voltage system for the scope of the present document and in accordance with international standards: A Low Voltage (LV) Distribution System is a network with a nominal voltage lower than 1 kV AC or 1.5 kV DC. The LV network in the State of Qatar is 240/415 V ± 6%, 3 Phase, 4 Wire. A Medium Voltage (MV) Distribution System is a network with nominal voltage included in the range from 1 kV AC up to 33 kV. The MV Distribution System nominal voltages in Qatar are 11, 22 and 33 kV. Electrical network voltages equal to or higher than 33 kV are not considered in this document. According to the Transmission Grid Code, the 33 kV is considered a sub-transmission network. To avoid doubt, the term Distribution Network will be preferred in this document in place of Distribution System. Electricity Qatar electrical infrastructure (lines, cables, substations, etc.) from above 33 Transmission kV up to 400 kV operated by Kahramaa. Network (ETN) Global horizontal Direct and diffuse irradiance incident on a horizontal surface expressed in irradiance (GHI) W/m2. In-plane irradiance The sum of direct, diffuse, and ground-reflected irradiance incidents upon (Gi or POA) an inclined surface parallel to the plane of the modules in the PV array, also known as plane-of-array (POA) irradiance. It is expressed in W/m2 IMOD_MAX_OCPR PV module maximum overcurrent protection rating determined by IEC 61730-2 (Note: This is often specified by module manufacturers as the maximum series fuse rating). Inspection Examination of an electrical installation in order to ascertain correct selection, design and proper erection of electrical equipment. Interface protection Electrical protection part of the solar PV System that ensures the PV System (IP) is disconnected from the network in case of an event that compromises the integrity of Kahramaa’s distribution network. Public Page 10 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 Term Description Inverter Electric energy converter that changes direct electric current to single-phase or polyphase alternating current. Irradiance (G) Incident flux of radiant power per unit area expressed in W/m2. Irradiation (H) Irradiance integrated over a given time interval and measured in energy units (e.g., kWh/m2/day). Islanding Situation where a portion of the distribution network containing generating plants becomes physically disconnected from the rest of the distribution network. One or more generating plants maintain electricity supply to such isolated parts of the distribution network. Load Flow It is a numerical analysis of the electric power flow in a transmission and/or distribution systems. A power-flow study usually uses simplified notations such as a one-line diagram and per-unit system, and focuses on various parameters, such as voltages, voltage angles, real power and reactive power. It analyses the power systems in normal steady-state operation. Loss Of Mains Represents an operating condition in which a distribution network, or part of (LOM) it, is separated from the main power system (on purpose or in case of a fault) with the final aim of de-energisation. The protection that detects this condition is known as anti-islanding protection. Main Meter It is the bidirectional smart meter installed at the Connection Point which measures the amount of electric energy actually exchanged (import or export) by the Consumer with the distribution network. Maximum Available This is the Active Power Output based on the primary resource (for example, Active Power Output sun irradiance) and the maximum steady-state efficiency of the Solar PV System for this operating point. Maximum Capacity It is the maximum continuous active power which a Generating Unit can (Pmax) produce, less any auxiliary consumption associated used to facilitate the operation of that Generating Unit. The Maximum Capacity shall not be fed into the distribution network as specified in the Connection Agreement. In this document, this term is also referred to as Maximum Connected Capacity. Micro-inverter Small inverter designed to be connected directly to one or two PV modules (Note: A micro inverter will normally connect directly to the factory fitted module leads and be fixed to the module frame or mounted immediately adjacent the module). Module Integrated Any electronic device fitted to a PV module that provides control, monitoring Electronics or power conversion functions (Note: Module integrated electronics may be factory fitted or assembled on-site). National Control Main Kahramaa’s facility used to operate and control/maintain the Electric Centre (NCC) Power System. Peak Power (Wp) The output power achieved by a Photovoltaic Module under Standard Test Conditions (STC). It is measured in Wp (W peak). The sum of the peak power of the photovoltaic modules of either a string or an array determines the peak power of the string and the array, respectively (usually measured in kWp). The peak power of a photovoltaic array at STC is conventionally assumed as the rated power of the array. Photovoltaic (PV) The most elementary device that exhibits the photovoltaic effect, i.e., the cell direct non-thermal conversion of radiant energy into electrical energy. Power Factor It is the ratio of Active Power to Apparent Power. Public Page 11 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 Term Description Power Park Module A unit or ensemble of units generating electricity, which is either non- (PPM) synchronously connected to the network or connected through power electronics, and that also has a single Connection Point to the ETN. PV Array Assembly of electrically interconnected PV modules, PV strings or PV sub- arrays. For the purposes of this document, a PV Array comprises all components up to the DC input terminals of the Inverter. PV Module PV modules are electrically connected PV cells packaged to protect them from the environment and protect the users from electrical shock. PV String A set of series-connected PV modules. PV String Combiner A box where PV strings are connected, which may also include circuit Box breaker, monitoring equipment, and electrical protection devices. Rated Active Power Represents the sum of the nominal active power of all the Solar PV Units which compose the Solar PV System; it is generally referred to as Pnom of the Solar PV System. Reactive Power Represents a component of the apparent power at the fundamental frequency, usually expressed in kilovar (kVAr) or Megavar (MVAr). Reactive Power Defines the reserves of inductive/capacitive reactive power which can be Capability provided by a generating system/unit. The reactive power capability usually varies with the active power and the voltage of the generating system/unit. Residual Current A sensitive switch that disconnects a circuit when the residual current Device (RCD) exceeds the operating value of the circuit, referred as RCD in this document. Soiling ratio (SR) A ratio of the actual power output of the PV array under given soiling conditions to the power that would be expected if the PV array were clean and free of soiling. Solar PV System This term also has the same meaning as Power Plant or User’s System or Grid User, defined in the Transmission Grid Code. It is a solar PV installation of not more than 25 MW and not less than 1 kW capacity installed in one Premise and connected in parallel to Kahramaa’s Distribution Network. This document aims to be considered a power plant with one or more Solar PV Units. Besides, circuits and auxiliary services are also part of a solar PV System. To avoid doubt, in this document, the generic term Solar PV System is considered equivalent to solar PV System. This PV System includes the PV array, controllers, inverters, batteries (if used), wiring, junction boxes, circuit breakers, and electrical safety equipment. Solar PV System It is the smart metering installed at the output point of the solar PV System Meter and measures the total energy produced from the Solar PV Units. Solar PV Unit A group of devices that collects the sun’s irradiance in a Solar PV System, together with all plant and apparatus and any step-up transformer which relates exclusively to the operation of that part of the same Solar PV System. Only units that are Inverter based (i.e., Asynchronously connected to the Distribution Network through power electronics devices) are considered in this document. This definition will be equivalent to that of the Power Park Module as given in the Transmission Code. For the avoidance of doubt, in this document, the generic term Solar PV Unit will be considered equivalent to a solar PV Unit. Standard test Reference values of in-plane irradiance (1 000 W/m2), PV cell junction conditions (STC) temperature (25 °C), and the reference spectral irradiance defined in IEC 60904-3. Switch As per the Kahramaa Electricity and Wiring Code definition. Public Page 12 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 Term Description Testing Implementing measures in an electrical installation to prove its effectiveness (Note: It includes ascertaining values using appropriate measuring instruments, said values not being detectable by inspection). Time Current Curve The time current curve plots the interrupting time of an overcurrent device (TCC) based on a given current level. These curves are used for the protection coordination and are provided by the manufacturers of electrical overcurrent interrupting devices such as fuses and circuit breakers. THD (Total Concerning an alternating quantity, it represents the ratio of the r.m.s. value Harmonic Distortion) of the harmonic content to the r.m.s. value of the fundamental component or the reference fundamental component. Key References The Qatar Transmission Grid Code – Issue ES-M4 – Revision 0.0 – March 2020 and amendments in force until 02/2022 (in this document referred to as “Transmission Code”) CS-CSI-P1/C1 Kahramaa’s Low Voltage Electricity Wiring Code 2016 Safety Rules for the Control, Operation and Maintenance of Electricity Transmission & Distribution System of Qatar General Electricity & Water Corporation. System Operation Memorandum (SOM). Kahramaa interlocking document, (Qatar Power Transmission System Expansion – Latest phase – Substations). Qatar Construction Specifications, Latest edition ET-P26-G1 Guidelines for Protection Requirements. ES–EST-P1-G1 Guidelines for System Control Requirements for Power Supply to Bulk Consumers. ET-P20-S1 Transmission Protection Standards for TA and ET Projects. ES-M2 Qatar Power System Restoration Plan; and ES-M3 System Emergency, Categorization, Communication & Restoration Responsibility. QCDD (Qatar Civil Defence Department) regulations CS-CSI-P2 E_W – Infrastructure Preparation for Service Connection Purpose CS-CSI-P3 E_W – Services Inspection CS-CSI-P4 – Low Voltage Electrical Contractor Licensing CS-CSI-P5 – Handling of Contractors Violations Procedure CS-CSI-P6 – Illegal Connections Reconnections CS-CSM-P2 E_W – Supply Connection and Disconnection CS-MAS-P1 – Operation and Maintenance of AMI CS-MAS-P2 E_W – Meter Installation CS-MAS-P3 – Maintenance of Electricity and Water Meter CS-MAS-P5 – Materials Submittal Review _ Approval Procedure Energy and Water Conservation Code 2016 EPD-P1 – Electricity Supply Approval EPD-P4 – Processing Service Notes EPD-P6 11kV – Load Flow Study EPP-C1 – Electricity Planning Regulations for Supply EPP-P3 – Early Arrangement for Supply Connection EPP-P5 – Electricity Supply Application EPT-P2 – Basic Concept Report-Direct Connection Notification EPT-P3 – Peak Demand Forecast Public Page 13 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 EPT-P4 – Power System Studies and Five Years Development Plan ES-ESN-P3 – Dispatching Procedure ES-ESN-P4 – Bulk Industrial Consumers Energy Meter Readings Collection ES-ESP-P1 – Creating Operational Load Forecast ES-ESP-P2 – Long Term Operation Planning ES-ESP-P3 – Develop Monitor Energy Purchase Schedules and Allocation Plans ES-ESP-P4 – Operation Studies ES-ESP-P7 – Develop Surplus Available Capacity Plan for Marketing ES-M4 – Qatar Transmission Grid Code 2020 ET-P26 ETD – Responsibilities for Bulk Consumer’s Request for Supply of Electricity PW-PWK-P1 – Bulk Supply of Electricity and Water PW-PWP-P1 E_W – Demand Forecasting PW-PWP-P2 – Additional Capacity Planning PW-PWP-PL1 – Planning _ Procurement Policy PW-PWR-P2 – Renewable Energy Standards Development IEC 60364-6 – Low voltage electrical installations. Part 6: Verifications IEC 61010 – Safety requirements for electrical equipment for measurement, control and laboratory use IEC 61557 – Electrical safety in low voltage distribution systems up to 1000 V AC and 1500 V DC IEC 61724-1 – Photovoltaic system performance. Part 1: Monitoring IEC 61724-2 – Photovoltaic system performance. Part 2: Capacity evaluation method IEC 61724-3 – Photovoltaic system performance. Part 3: Energy evaluation method IEC 61730-2 – Photovoltaic (PV module safety qualification. Part 2: Requirements for testing IEC 62446-1 – Photovoltaic (PV) systems. Requirements for testing, documentation and maintenance. Part 1: Grid connection systems. Documentation, commissioning, tests and inspection IEC TS 62446-3:2017- Photovoltaic (PV) systems - Requirements for testing, documentation and maintenance - Part 3: Photovoltaic modules and plants - Outdoor infrared thermography IEC 61829:2015 Photovoltaic (PV) array - On-site measurement of current- voltage characteristics IEC 62548 – Photovoltaic (PV) arrays. Design requirements NEC / NFPA 70 – Section 690.11 Arc-Fault Circuit Protection (Direct Current) UL 1699B – Photovoltaic (PV) DC Arc-Fault Circuit Protection EARTHING IEC 60364-5-54 for all LV installations. IEC 60364-7-712 and IEC 62548 specifically for PV Systems. IEEE 80 Guide for Safety in AC Substation Grounding LIGHTNING IEC 62305 - Lightning Protection standard. Public Page 14 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 Companion Documents The documents listed hereinafter have to be considered a compendium of the current document. Therefore, they should be carefully read in addition to this. a) EP-EPP-P7-S1Technical Specifications for the Connection of PV Systems to the Network b) EP-EPP-P7-G2 Guidelines for Information in Basic and Final Design, last revision c) EP-EPM-G2 Guidelines for the Eligibility of Manufacturers' Equipment, last revision d) PW-PWR/G2 - Safety related to the installation of Solar PV Systems, last revision Public Page 15 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 4 Types of Tests and Responsibilities 4.1 Off-line Tests and Commissioning Test The Off-line Tests and the Commissioning Test described in these Guidelines are specific of small-scale PV Systems. The Off-line Test and the Commissioning Tests are arranged by the Contractor and undertaken by a qualified Test Engineer under his responsibility. 4.2 Responsibilities in Inspection and Testing Figure 1 summarizes the timeline of the verification process, the inspection and other related activities according to the different roles: The Contractor is in charge of carrying out the tests. Kahramaa is in charge of carrying out Inspections, the meter installation and the connection to the Distribution Network. The diagram in Figure 1 does not consider the information flow, the documents produced in the process and the checks between actions. Figure 1 – Inspections to verify and test a PV System As can be seen in Figure 1, the assessment of a PV System for its connection to the distribution network requires witnesses of the Commissioning Test (and inspection) that depend on the maximum capacity of the PV System: PV Systems below or equal to 50 kWp. PV Systems above 50 kWp. After the Tests and Inspection has been carried out, everything is assembled correctly, and the PV System works properly, the authorization to start the production is given by Kahramaa. The goal of the overall assessment is to verify the PV System and its compliance with the document “EP-EPP-P7-S1 Technical Specifications for the Connection of PV Systems to the Network". Public Page 16 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 The Contractor of the Consumer shall carry out the following actions: Off-line Tests Commissioning Tests Any additional tests required by Kahramaa After the Inspections and tests were successfully conducted with satisfactory results, Kahramaa issues the REG Commissioning Test Report and the Connection Agreement, which certifies that the installation is compliant with Kahramaa rules and regulations, and that the electricity production can start. The requirements of the above-described Inspection follow the requirements of the standard IEC 62446 “Grid-connected photovoltaic systems – Minimum requirements for system documentation, commissioning tests and inspection”. 4.2.1 Inspection and Witnessing the Test arranged by the Contractor The aim of Kahramaa Witnessing the Commissioning Test arranged by the Contractor is to verify the PV System, at least in those parts that are relevant to Kahramaa Distribution Network. Before witnessing tests, the Kahramaa inspector shall initially inspect the site and after witnessing the tests. The witnessing of Kahramaa is mandatory for PV Systems that exceed 50 kW. It could be the case that either some or all the tests are undertaken by the Contractor have to be repeated in Kahramaa inspector's presence. 5 Tests Methodology and Documentation 5.1 Test Methodology The methodology of the Test is outlined below: 1. The installation to be evaluated follows the tests and checklists of this document. 2. The Contractor will be responsible for calibrate the equipment required for all checks and verifications. They have to be available for the tests. 3. All checks and technical verifications must be performed by the Test Engineer delegated by the Contractor for this activity. The Test Engineer is to ensure the availability of the necessary test equipment at site. 4. A check or test yielding a negative result can be repeated in case an adequate correction measure can be applied (e.g., retest a PV string that was found not properly connected) and the result of the test repetition acknowledged; in case a negative result cannot be corrected, the check or test shall be considered failed. 5. In case of a negative result, the Contractor shall apply corrective measures before the checks and verifications that end with a negative result are repeated in the frame of the next site inspection. A revision of the inspection report shall be issued. 6. In case of positive results, the installation will be approved, and the PV System will be allowed to start the production. 7. MS and ITP approved by Kahramaa prior to start of any work. Public Page 17 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 5.2 PV System Documents Required during the Inspection In case Kahramaa witnesses the Commissioning Test, the design documents relevant to the inspection and Inspection Test Plan (ITP) with acceptance criteria shall be made available by the Contractor on-site for consultation by Kahramaa inspectors visiting the site where the PV system is installed. Also, the contractor shall provide the undertaking letter for the safety and stability of civil structures. Details of the minimum information required are contained in section 8.2. 6 Safety issues This chapter does not substitute the safety laws and rules in force in Qatar regarding the works on electric, mechanical and civil installations2. The purpose is to integrate the existing rules with some indications which focus on particular safety aspects related to PV systems. 6.1 Hazards and Safety Measures The on-site test, particularly on electrical installations, is the Test Engineer's task and responsibility. As he must be aware of the main details of such electrical tests and the associated hazards, according to the laws and rules in force in Qatar, his experience and the description of his activities are provided below. All that is located upstream of a circuit-breaker on the DC section of a PV system (PV modules and their connections) remains under voltage (during the day) even after opening this device. All combiner boxes of the PV system on the DC side shall expose a warning sign, which indicates the presence of live parts even after the opening of DC circuit- breaker devices. Figure 2 shows a warning sign to indicate the presence of a PV system with possible danger. Figure 2 – Example of a warning, which indicates the presence of PV system with possible hazardous voltage 2 It is not the responsibility of Kahramaa to check the compliance of the design of the Small-scale Solar PV systems with the Building Code Public Page 18 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 All interventions on the live parts of PV strings are therefore to be considered works under voltage. This difference is unusual for an installer who is accustomed to thinking that the PV System is off-voltage when the general circuit breaker is switched off. Only a qualified person, i.e., a professional with sufficient knowledge and experience, can work safely on live parts and successfully carry out electric interventions under voltage. The protection provisions and the proper PPE are specified in relevant international and local standards. However, it is worth mentioning that when working under voltage, the operator must wear the following (see Figure 3): A safety helmet made of insulating material with a face shield (mainly to protect him against electric arcing). Arc related PPE and flame-retardant clothing that does not leave uncovered parts of the trunk or limbs. Insulating gloves (of appropriate voltage class). Figure 3 – Main safety measures for works under voltage Insulated tools for electrical work are also to be used. An alternative to insulated tools is an insulating mat for electrical purposes, placed beneath the operator. After the electric shock, arcing represents the main danger in electric interventions under voltage. The energy released by electric arcs may cause burns and damage to the eyes and skin, and this energy increases with the arcing current and the duration of the intervention. In the case of short-circuit, the arcing current in PV systems is lower than that in other electric plants supplied by the grid, but the duration is greater because it is more difficult to quench a DC arc. Works under-voltage carried out in open-air spaces shall be avoided in case of: Fog, rain, snow or dust storms, mainly because of the scarce visibility. Public Page 19 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 Very low temperatures or strong wind because of the difficulty to grip and hold tools. Thunderstorms because of the possible overvoltage on circuits. Construction works of an ordinary electric plant do not present any risk of electrical nature until the plant has been completed and connected to the grid. However, this is not valid for installing a PV System because the exposure of a PV module to sunlight produces a voltage between the poles of the module itself. To avoid this, it is possible to short-circuit both connectors of a PV module or of a series of modules (the short circuit current does not damage the PV modules because it is only slightly greater than the rated current). Another possible expedient is shown in Figure 4 and consists of keeping the connectors of a module and the string circuit-breaker open during installation. In Figure 4, it is illustrated that a person with access to the positive (+) and negative (- ) poles upstream or downstream of the circuit-breaker is safe (case A). Alternatively, a person who touches two poles on the same branch is not safe (cases B and C). In all cases, the work and interventions during construction and inspection and maintenance of a PV array shall be considered works/ interventions under voltage. Figure 4 – The interruption of a string makes the worker A safe but keeps the workers B and C unsafe Interventions on PV systems also involve non-electric risks, as follows: Burning when touching PV modules. If modules are exposed to sunrays, they may reach temperatures of almost 100 °C at the front and 80 °C at the rear. Operators must wear work gloves resistant to up to 100 °C and proper clothing. Risk of falling. When the PV system is installed on a roof, operators shall adopt the safety measures prescribed for the given circumstance, for instance, a safety harness anchored with a carabineer to a stable element of the roof (hooks, safety ropes, pillars, etc.). Insect stings. Bees, hornets and other insects can nest behind a PV module or in another sheltered place. Public Page 20 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 6.2 Information from Contractor about Specific Risks on-site and Safety Measures The form CS- CSI-P3-G2/F4 shall be filled and delivered by the Contractor of the Consumer to Kahramaa identifying specific risks and on-site safety measures before the Inspectors perform an on-site visit to the PV system. 7 Off-line Tests 7.1 Overview This test is part of Stage 2 of the connection Process of Kahramaa, and it is connected with the activities named 5.2.12 of the General Connection Process. 5.2.12 REG off-line Commissioning Figure 5 – Connection Process steps related to Off-line Test The “REG Off-line Commissioning” (5.2.12) is the Contractor’s responsibility and shall be performed on all PV systems, regardless of their power capacity. The Off-line Test applies to all PV systems regardless of their nominal power and voltage connection. The Off-line Test is composed of an inspection and a set of tests made by a Test Engineer appointed by the Contractor. As a rule, this test begins after completing the PV system, particularly the DC circuits (i.e., PV strings and arrays). However, for large PV systems, for safety reasons, the Test Engineer may initiate the tests on strings during installation to prevent parallel strings with a different number of PV modules or reversed polarity. In this case, the results of these tests shall be duly reported and completed with date and time. In all the cases where tests are initiated and completed in a single day, it is sufficient to add the date of the day and the time of test initiation and completion. 7.1.1 Basic Tests and Additional tests The test procedure applied to a small-scale PV System needs to be appropriate to the scale, type, location and complexity of the system in question. These guidelines define a Basic Test procedure and some additional tests that can also be performed once the standard sequence is completed. Basic tests – The minimum requirement – A standard set of tests that shall be applied to all Small-scale PV systems. Additional tests – Further tests assuming that all Basic tests have already been undertaken. They also contain tests that may be performed in some circumstances. Unless differently agreed, these tests are optional. 7.1.2 Special considerations for PV systems with module-level electronics Table 1 shall be used to determine a suitable test procedure for systems constructed using AC modules, power optimisers, or any other form of module-level electronics. Public Page 21 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 Table 1 – Modifications to the test procedure for Small-scale PV systems with module-level electronics Type of equipment Modifications to test procedure PV Module − No DC test or inspection works required Micro inverter where no site − Testing of DC circuits is not required constructed wiring is used − Inspection of DC works is required (all connections using module and inverter leads) Micro inverter where site − Testing of DC circuits is required constructed wiring is used − Inspection of DC works is required Module integrated − Where possible, the Basic tests are to be followed electronics − Manufacturer to be consulted to determine any restrictions to tests (e.g., insulation resistance test) − Manufacturer to be consulted on pass / fail criteria for tests (e.g., expected Voc) Due to the diverse nature of the different module-level electronics equipment available, it is impossible to specify what tests can be performed or to detail the expected results. In all cases of PV Systems with any form of module-level electronics (such as power optimizers), the manufacturer should be consulted prior to commissioning. 7.2 Common Requirements Testing of the electrical installation shall be done according to IEC 60364-6 and IEC 62446-1. Measuring instruments and monitoring equipment and methods shall be chosen following the applicable relevant parts of IEC 61557 and IEC 61010. If other measuring equipment is used, they shall provide an equivalent level of performance and safety. All tests shall be carried out where relevant and should be made in the sequence listed. In the event of a test indicating a fault, once that fault has been cleared, all previous tests shall be repeated if the fault influenced the result of these tests. 7.3 Solar PV Systems Inspection The inspection shall precede testing and normally be done before energizing the installation. If the wiring of the DC section will not be readily accessible after the installation, wiring may need to be inspected before or during installation works. The following items, specific to grid-connected PV systems, shall be included in the inspection. 7.4 DC System 7.4.1 DC system – General Verifications Inspection of the DC installation shall include at least verification that: Public Page 22 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 a) The DC system has been designed and installed according to the requirements of IEC 60364 and IEC 62548. b) The maximum PV array voltage is suitable for the chosen array location, , except residential (1000 Vdc on buildings, 1500 Vdc otherwise). c) The maximum PV array voltage suitable for residential location should not exceed 600V. d) Where necessary, roof fixings and cable entries are weatherproof. 7.4.2 DC system – Verification of the Protection against Electric Shock In the DC installation, at least one of the following measures in place for protection against electric shock shall be adopted: a) Protective measure provided by extra-low voltage (SELV / PELV). b) Protection by using class II or equivalent insulation adopted on the DC side. Furthermore, PV string and array cables have been selected and erected to minimize the risk of earth faults and short-circuits. This is typically achieved using cables with protective and reinforced insulation (often termed “double insulated”). 7.4.3 DC system – Verification of the Protection against the Effects of Insulation Faults Inspection of the DC installation shall include at least verification of the measures in place for protection against the effects of insulation faults, including the following: a) That a PV Array Earth Insulation Resistance detection and alarm system is installed – to the requirements of IEC 62548 (this is typically provided within the inverter). b) That a PV Array Earth Residual Current Monitoring detection and alarm system is installed – to the requirements of IEC 62548 (this is typically provided within the inverter). 7.4.4 DC system –Verification of the Protection against Overcurrent The inspection of the DC installation shall include at least verification of the measures in place for protection against overcurrent in the DC circuits: a) For systems without a string overcurrent protective device, verify that: − IMOD_MAX_OCPR (the module maximum series fuse rating) is not greater than the maximum reverse current; and − string cables are sized to accommodate the maximum combined fault current from parallel strings according to IEC 62548. b) For systems with string overcurrent protective device, verify that: − the string overcurrent protective devices are fitted and correctly specified according to the requirements of IEC 62548. c) For systems with array / sub-array overcurrent protective devices, verify that: − the overcurrent protective devices are fitted and correctly specified according to the requirements of IEC 62548. The potential for the system inverter(s) to produce a DC back-feed into the PV array circuits shall also be verified. Public Page 23 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 7.4.5 DC system – Verification of Earthing and Bonding Arrangements The inspection shall include the followings points: a) PV System that includes functional earthing of one of the DC conductors, verify if the functional earth connection has been specified and installed following the requirements of IEC 62548. b) Verify if the PV System directly connects to earth on the DC side, and a functional earth fault interrupter is provided according to IEC 62548 requirements. c) Verify if the array frame bonding arrangements have been specified and installed according to IEC 62548 requirements (functional earthing is normally required by the PV Array Earth Insulation Resistance detection and alarm system). d) If protective earthing and/or equipotential bonding conductors are installed, verify if they are parallel to, and bundled with, the DC cables. 7.4.6 DC System – Verification of the Protection against the effects of Lightning and Overvoltage The inspection shall include the followings points: a) Verify the area of all wiring loops has been kept as small as possible to minimize voltages induced by lightning. b) Verify if measures are in place to protect long cables (e.g., cables with screening or the use of surge protective devices, SPDs). c) In case SPDs are fitted, verify if the installation has been made according to the requirements of IEC 62548. 7.4.7 DC system – Verification of the selection and erection of electrical equipment The inspection shall include the followings points: a) Verify if the PV modules are rated for the maximum possible DC system voltage. b) Verify if all DC components are rated for continuous operation at DC and the maximum possible DC system voltage and current, as defined in IEC 62548. c) Verify if cables are certified according to EN 50618 or another equivalent standard. d) Verify if the wiring systems have been selected and erected to withstand the expected external influences such as wind, ice formation, temperature, UV and solar radiation. e) Verify if suitable means of isolation and disconnection have been provided for the PV array strings and PV sub-arrays following the requirements of IEC 62548. f) Verify if a DC switch disconnector is fitted to the DC side of the inverter according to IEC 62548 requirements. g) Verify if blocking diodes are fitted, the reverse voltage rating is at least 2 × Voc (STC) of the PV string in which they are installed. h) Verify if the plug and socket connectors, including multiple connectors (if any), mated together are of the same type, same specifications and comply with the requirements of IEC 62548. i) Verify the IP rating of the junction boxes. j) Verify the DC Disconnector rating, wiring drawing, fuse rating, SPD rating, voltage rating and IP rating of combiner boxes. Public Page 24 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 7.4.8 Checklist for DC System Verification A checklist for the verification of the DC part is in the Table 1 of the Form CS- CSI- P3-G2/F1. 7.5 Labelling and Fire Protection 7.5.1 Labelling and identification Inspection of the PV system shall at least verify that: a) all circuits, protective devices, switches and terminals are suitably labelled to the requirements of IEC 60364 and IEC 62548; b) all PV string combiner boxes carry a warning label indicating that active parts inside the boxes are fed from a PV array and may still be energized after isolation from the PV inverter and public supply; c) means of isolation on the AC side is clearly labelled; d) dual supply warning labels are fitted at the interconnection point; e) a single line wiring diagram is displayed on site; f) Inverter protection settings are displayed at the site [IEC 62446] g) installer details are displayed on site; h) shutdown procedures are displayed on site; i) emergency procedures are displayed on-site (where relevant); and j) all signs and labels are suitably affixed and durable. A checklist for labelling verification is in the Table 2 of the Form CS- CSI-P3-G2/F1. 7.5.2 Fire Protection Verification – (in coordination with Civil Defence as necessary) 7.5.2.1 Verifications common to all PV systems Inspection of the PV system as regards the fire protection shall include the following verifications applicable to all PV systems (BAPV, BIPV, ground-mounted, etc.): a) A manual emergency system for the disconnection of the PV modules from the internal electric PV System of the building is present and operates in one of the following ways: − Outside the building on the DC side. − When the inverter is placed outside the building, on the AC and DC side outside the building. − In a proper fire-compartmented area. b) When there is a passage of cables from PV modules inside the building before the disconnector, cables inside the building are placed in trunking with fire-rated protection of at least one-and half-hour c) Except for One-and-Two-Family Dwelling, electrical disconnection is operated using a manual call point with all the following characteristics: − Installed at the height of 1.1 – 1.4 m above floor level and in a plain, accessible, well-lit and free-hindrance place. − It is located close to external access to be easily operated by personnel or firefighters. Public Page 25 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 − Follows the NFPA 72 and a proper label indicating it actuates the disconnection of the PV planting. d) PV array is equipped with an earth fault detector that preferably shuts down the array in case of failure. e) A simplified site plan with the position of PV modules, cables and disconnectors is exposed close to the main energy meter. If a manual call point is present in the building, a further copy of the simplified site plan is exposed on the side. f) The area where PV modules, cables and other equipment are located, if accessible, is marked by proper signs. They are also placed in correspondence with each PV System access door. The same signs indicate cables before disconnectors and are placed every 5 meters along the cable. These signs are UV resistant and indicate the DC voltage as the Open Circuit Voltage at STC of the PV array. Their minimum size is 200  200 mm (w  h) A checklist for the verification the fire protection in all the PV Systems is in the Table 3 of the Form CS- CSI-P3-G2/F1. 7.5.2.2 Verifications for BAPV Inspection of the BAPV system shall include the following verifications: a) Adoption of one of the following measures when the PV system is installed on a rooftop: − PV modules and their interconnections are placed on a roof made of non- combustible material according to ASTM E 136 or EN 13501-3 (class A1) − Interposition of a non-combustible layer between PV modules with their interconnections and the roof. The non-combustible layer is at least one- half-hour fire-rated. − A new risk assessment to be prepared which takes into account the presence of the PV system to be approved by a competent body in Qatar. b) PV modules, wirings, switchboard assemblies and other equipment do not cover any possible ventilation systems on the roof, e.g., skylights, smoke extraction systems or chimneys. c) PV components and wirings are placed at a minimum distance of 1 m (top view) from the perimeter of the ventilation systems. In any case, their position and installation are following the manufacturer’s prescriptions. d) PV components and wirings are placed at a minimum distance of 0.5 m (top view) from the perimeter of skylights, chimneys or other openings. e) Components and equipment installed internally or externally do not obstruct in any way the existing means of egress. f) Minimum elevation of the PV modules above the roof is 50 mm. A checklist for the verification the fire protection in the BAPV Systems is in the Table 4 of the Form CS- CSI-P3-G2/F1. 7.5.2.3 Verifications for BIPV Inspection of the BIPV system shall include the following verifications: a) In case of BIPV is not installed in compartmented fire areas, at least one of the following further measures is adopted: Public Page 26 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 − The manual call point also disconnects or short-circuits separately each PV module or groups of PV modules, each of them having an open-circuit voltage at STC not greater than 120 VDC. − An Arc Fault Circuit Interrupter (AFCI) to protect the DC side from series arcs following NEC Section 690.11 and UL 1699B is installed. When AFCI detects a failure, it disconnects the DC side of the PV System and generates an audible signal. b) Where applicable, PV modules, wirings, switchboard assemblies and other equipment do not cover any possible ventilation systems on the roof, e.g., skylights, smoke extraction systems or chimneys. c) Where applicable, PV components and wirings are placed at a minimum distance of 1 m (top view) from the perimeter of the ventilation systems. In any case, their position and installation are following the manufacturer’s prescriptions. d) Where applicable, PV components and wirings are placed at a minimum distance of 0.5 m (top view) from the perimeter of skylights, chimneys or other openings. e) Where applicable, components and equipment installed internally or externally do not obstruct the existing means of egress. A checklist for the verification the fire protection in the BIPV Systems is in the Table 5 of the Form CS- CSI-P3-G2/F1. 7.5.3 Verification of the Special Requirements for Households Inspection of the PV systems in households shall include the following verifications: a) The back sheet, the junction box and the wiring of each PV module are compliant with at least one of the following conditions: − Not reachable without a proper provisional tool (stair, scaffold, etc.). − Protected with at least IP67A degree, that means against access with the back of the hand according to IEC 60529. − Outside arm’s reach is a vertical distance of up to 2.5 m from the floor. b) The supporting structures placed in rows on the floor are compliant with all the following prescriptions: − When the spacing between rows exceeds 0.5 m, the connections are placed on the floor, not higher than 50 mm, without sharp edges and clearly visible. They withstand the weight of a person (100 kg). − Module mounting structure (MMS)/ Ballasts and their arrangements are clearly visible and without sharp edges. − Electrical connections between the PV array and combiner boxes or inverters preferably do not interfere with existing passages for people. In the case of passage crossing, the connections are placed on the floor, not higher than 50 mm, without sharp edges and clearly visible. Furthermore, the top of the trunking and the floor surface is matched with sloped surfaces to avoid the step. This trunking withstands the weight of a person (100 kg). A checklist for the verification the fire protection in in households is in the Table 6 of the Form CS-G2/F1. Public Page 27 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 7.6 Basic Tests The procedures established in the IEC 62446-1 standard shall be followed for the basic tests presented in the following sections. The Basic Tests represent the expected minimum test sequence and shall be applied to all small-scale PV Systems. In some circumstances, the AC side testing may only be practical at a later stage in a project and may need to be scheduled after the DC testing phase. Where this is necessary, some DC functional tests (e.g., ensuring correct inverter operation) will need to be postponed until after the AC testing is complete. The following test regime shall be performed on all systems: AC Side Insulation resistance test of the AC circuit to be performed according to IEC 60364-6 requirements. DC Side The following tests shall be carried out on the PV array's DC circuit(s). a) Continuity of earthing and/or equipotential bonding conductors, where fitted b) Polarity test c) PV string combiner box test d) String open circuit voltage test e) String circuit current test (short circuit or operational) f) Functional tests g) Insulation resistance of the DC circuits. For safety reasons and the prevention of damage to the connected equipment, the polarity test and combiner box test must be performed before any strings are interconnected. An I-V curve test is an acceptable alternative method to derive the string open-circuit voltage (to minimize voltages induced by lightning) and short circuit current (Isc). Where an I-V test is performed, separate Voc and Isc tests are not required. 7.6.1 Continuity Test of Protective Earthing and Equipotential Bonding Conductors Where protective earthing and/or equipotential bonding conductors are fitted on the DC side, such as bonding of the array frame, an electrical continuity test shall be made on all such conductors. The connection to the main earthing terminal should also be verified. 7.6.2 PV string Polarity Test The polarity of all PV string cables shall be verified using suitable test apparatus. Once polarity is confirmed, cables shall be checked to ensure they are correctly identified and correctly connected to system devices such as switching devices or inverters. Note: For safety reasons and to prevent damage to the connected equipment, it is extremely important to perform the polarity check before other tests and before switches are closed or string overcurrent protective devices are inserted. If a check is made on a previously connected system and the reverse polarity of one string is found, it is then important to check modules and bypass diodes for any damage caused by this error. Public Page 28 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 7.6.3 PV string Combiner Box Test The consequence of a reversed string, particularly on larger systems with multiple often interconnected combiner boxes, can be significant. The combiner box test aims to ensure all strings interconnected at the combiner box are connected correctly. This shall be physically verified against the approved DC SLD also. SPD connection, fuse rating, and earthing can also be checked. 7.6.4 Open Circuit Voltage Measurement of PV Strings The purpose of the open-circuit voltage (Voc) measurement within the Basic Test procedure is to check that module strings are correctly wired. Specifically, the expected number of modules are connected in series within the string. Voltages significantly less than the expected value may indicate one or more modules connected with the wrong polarity, one or more shorted bypass diodes or faults due to poor insulation, subsequent damage and/or water accumulation in conduits or junction boxes. Conversely, high voltage readings are usually the result of wiring errors. The open-circuit voltage of each PV string should be measured using suitable measuring apparatus. Before closing any switches or installing string overcurrent protective devices (where fitted), this should be done. The resulting string open circuit voltage reading shall then be assessed to ensure it matches the expected value following ways: a) Compare with the expected value derived from the module datasheet or from a detailed PV model that considers the type and number of modules and the module cell temperature. b) For systems with multiple identical strings and where there are stable irradiance conditions, voltages between strings can be compared and shall be within 5% variation. 7.6.5 Current measurement of PV strings 7.6.5.1 General The purpose of a PV string current measurement test is to ensure the system's correct operational characteristics and verify that there are no major faults within the PV array wiring. These tests are not to be taken to measure module / array performance. Two test methods are possible (short circuit test or operational test), and both will provide information on the correct functioning of the PV string. The short circuit test is preferred as it will exclude any influence from the inverters. An I-V curve test is also independent of the inverter and provides a good alternative means to perform this test. 7.6.5.2 PV string – Short Circuit Test The short circuit current of each PV string should be measured using suitable test apparatus. The making / interruption of string short circuit current is potentially hazardous, and a suitable test procedure, such as that described below, should be followed. Measured values should be compared with the expected value. For systems with multiple identical strings and where there are stable irradiance conditions, Public Page 29 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 measurements of currents in individual strings shall be compared. These values should be the same (typically within 5 % of the average string current for stable irradiance conditions). For non-stable irradiance conditions, an irradiance meter reading or visual appraisal of the sunlight conditions may be used to consider the validity of the current readings. Further possibilities are listed in IEC 62446-1. To safely perform the test, it is necessary to introduce a temporary short-circuit by using one of the following methods: a) a test instrument with a short circuit current measurement function (e.g., a specialized PV tester); b) a short circuit cable temporarily connected to a load break switching device already present in the string circuit; c) a “short circuit switch test box” – a load break rated device that can be temporarily introduced into the circuit to create a switched short circuit The breaking device used (test instrument or circuit breaker) shall have a rating greater than the potential short circuit current and open-circuit voltage. Further possibilities are listed in IEC 62446-1. 7.6.5.3 PV string – Operational Test With the system switched on and in normal operation mode (inverters maximum power point tracking), the current from each PV string should be measured using a suitable clip-on ammeter placed around the string cable. Measured values should be compared with the expected value. For systems with multiple identical strings and where there are stable irradiance conditions, measurements of currents in individual strings shall be compared. These values should be the same (typically within 5 % of the average string current for stable irradiance conditions). For non-stable irradiance conditions, an irradiance meter reading may be used to adjust the current readings. 7.6.6 Functional Tests The following functional tests shall be performed: a) Switchgear and other control apparatus shall be tested to ensure correct operation and properly mounted and connected. b) All inverters forming part of the PV system shall be tested to ensure correct operation. The test procedure should be as defined by the inverter manufacturer. Functional tests that require the AC supply to be present (e.g., inverter tests) shall only be performed once the AC side of the system has been tested (Commissioning test). 7.6.7 PV Array Insulation Resistance Test 7.6.7.1 General PV array DC circuits are live during daylight and, unlike a conventional AC circuit, cannot be isolated from the voltage source before performing this test. Public Page 30 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 Performing this test presents a potential electric shock hazard; therefore, it is important to understand the procedure before starting any work. The following basic safety measures should be followed: Limit access to the working area. Do not touch and take measures to prevent any other persons from touching any metallic surface when performing the insulation test. Do not touch and take measures to prevent other persons from touching the back of the module/laminate or the module/laminate terminals with any part of your body when performing the insulation test. Whenever the insulation test device is energized, there is a voltage in the testing area. The equipment is to have the automatic-discharge capability. Appropriate personal protective clothing/equipment should be worn for the test duration. A wet array insulation test may be appropriate if the test results are questionable or if insulation faults are suspected due to installation or manufacturing defects. It may help locate the location of a fault – see Paragraph 7.7.5 for a suitable test procedure. Where SPDs or other equipment are likely to influence the verification test or be damaged, such equipment shall be temporarily disconnected before carrying out the insulation resistance test. 7.6.7.2 PV Array Insulation Resistance Test – Test method The test should be repeated, as a minimum, for each PV array or sub-array (as applicable). It is also possible to test individual strings if required. TEST METHOD 1 – Test between array negative and earth followed by a test between array positive and earth. TEST METHOD 2 – Test between earth and short-circuited array positive and negative. Where the structure/frame is bonded to earth, the earth connection may be to any suitable earth connection or to the array frame (where the array frame is used, ensure good contact, and have continuity over the whole metallic frame). For systems where the array frame is not bonded to earth (e.g., where there is a class II installation without a functional earthing), a commissioning engineer may choose to do two tests: a) between array cables and earth, and b) an additional test between array cables and frame. For arrays with no accessible conductive parts (e.g., PV roof tiles), the test shall be between array cables and the building earth. Where test method 2 is adopted, to minimize the risk from electrical arcs, the positive and negative cables of the array should be short-circuited safely. Typically, this would be achieved by an appropriate short-circuit switch box. Such a device incorporates a load break rated DC switch that can safely make and break the short circuit connection – after array cables have been safely connected to the device. The test procedure should ensure that the peak voltage does not exceed module, switch, surge arrestor or other system component ratings. Public Page 31 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 7.6.7.3 PV Array Insulation Resistance – Test procedure 7.6.7.3.1 Insulation resistance – PV arrays up to 10 kWp For PV arrays of up to 10 kWp, the insulation resistance shall be measured with the test voltage indicated in Table 2. The result is satisfactory if each circuit has an insulation resistance not less than the appropriate value given in Table 2. Table 2 – Minimum values of insulation resistance (IEC 62446-1) – PV arrays up to 10 kWp System voltage Test voltage Minimum insulation (Voc (STC) ´ 1.25) resistance (IEC 62446-1) [V] [V] [MW] < 120 250 0.5 120 to 500 500 1 500 to 1000 1 000 1 > 1000 1500 1 7.6.7.3.2 Insulation resistance – PV arrays above 10 kWp Perform the insulation resistance test on: individual strings; or combined strings, where the total combined capacity is no more than 10 kWp. The insulation resistance shall be measured with the test voltage indicated in Table 2. The result is satisfactory when the insulation resistance is not less than the appropriate value given in Table 2. 7.6.8 Checklist for the PV Array Tests This section aims to report the tests made on all the strings of the PV array. Each copy of the document may contain tests on up to five strings. In case of more than five stings in parallel on the same PV array, a progressive Sheet number and the same PV array number for each PV array shall be indicated in the heading. In case of more than one independent PV array being present, several documents equal to the number of independent PV arrays, or to a multiple of them if more than five strings per each independent PV array are present, will be used. A different progressive PV Array number shall be indicated for each PV array. A checklist for the verification the results of the PV Array Tests is in the Table 7 of the Form CS- CSI-P3-G2/F1. 7.6.9 Earth Resistance of the PV System The test should be performed following the Kahramaa Electricity and Wiring Code. 7.6.10 Infrared Camera Inspection for Inverters and Circuit Breakers The purpose of an infrared (IR) camera inspection is to detect unusual temperatures in the inverter and circuit breaker. Such temperature may indicate problems within the equipment. Public Page 32 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 This test is primarily looking for anomalous temperature; overheating equipment and possible overloaded equipment; overheating connections of the equipment that means loose or weak connections; defective electrical component and load imbalances. For an IR camera inspection, scan the equipment in question and their electrical connections, or any specifically identified problem that exhibits a discernible temperature difference from its immediate surroundings. When scanning from the front of equipment, the camera and operator shall not cast shadows on the area under investigation. IEC TS 62446-3:2017 standard may also be referred for the requirement of the inspection equipment, inspection procedure, evaluation, minimum environmental conditions and reporting required for performing the outdoor thermography. 7.6.11 Final Result page of the Off-line Test The final result of the verification of the off-lines tests is in the Table 8 of the Form CS- G2/F1. 7.7 Additional Tests Additional tests are normally intended for larger or more complex systems. All Basic tests shall have been undertaken and passed before commencing on the Additional tests. In addition to the Basic tests, the following additional tests as per IEC 62446-1 may be applied: a) String I-V curve test b) Infra-Red (IR) inspection c) Voltage to ground – resistive ground systems – This test is used to evaluate systems that use a high impedance (resistive) connection to ground d) Blocking diode test – Blocking diodes can fail in both open and short circuit states. This test is important for installations where blocking diodes are fitted e) Wet insulation test – A wet insulation test is primarily used as part of a fault-finding exercise: where the results of a standard (nominally dry) insulation test are questionable or where insulation faults due to installation or manufacturing defects are suspected f) Shade evaluation – When inspecting a new PV system, verifying the as-built shade conditions can be a useful record. Like the electrical measurements described in this standard, the shading evaluation provides a baseline for future comparisons as the shading environment changes. A shade record can also verify that the shading assumptions used for system design are reflected in the as-built system. Shade records are of particular use where a project is subject to a performance guarantee or other similar performance contract. As noted in the Basic test description, where an I-V curve test is being performed, it provides an acceptable means to derive Isc and Voc. In some circumstances, just one element or part of the Additional test regime may be chosen to be implemented. An example of this is when a client requires the performance evaluation provided by the I-V curve test to be added to the standard Basic test sequence. Public Page 33 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 In some circumstances, the additional tests may only be implemented on a sample portion of the system. An example is when a client requires I-V curve tests and/or IR inspection on a fixed proportion of the strings. It is relatively common, particularly for large systems, that some of the additional tests are performed on a selected system sample (a fixed percentage of the strings / modules). The client shall agree upon such a selective approach and the percentage of the system to be tested before commissioning. 7.7.1 String I-V curve Measurement A string I-V curve test can provide the following information: Measurements of string open-circuit voltage (Voc) and short circuit current (Isc). Measurements of max power voltage (Vmpp), current (Impp), and max power (Pmax). Measurement of string performance. Measurement of module / string fill factor. Identification of module / string defects or shading issues. Before undertaking an I-V curve test, the I-V curve test device shall be checked to ensure it is suitably rated for the voltage and current of the circuit under test. An I-V curve test is an acceptable alternative method to derive the string open-circuit voltage (Voc) and short circuit current (Isc). Where an I-V curve test is performed, separate Voc and Isc tests are not required – provided the I-V curve test is performed at the appropriate stage in the Category 1 test sequence. The string under test should be isolated and connected to the I-V curve test device. If the purpose of the I-V curve test is solely to derive values for Voc and Isc, then there is no requirement to measure irradiance (or cell temperature). Given suitable irradiance conditions, an I-V curve test provides a means to assess that the performance of a PV string / module is meeting the rated (nameplate) performance. PV string and array performance measurements shall be performed at stable irradiance conditions of at least 400 W/m2 as measured in the plane of the array. If the measurements are intended for reference to STC (the purpose is to calculate the nameplate rated power of the modules/array), the irradiance shall be at least 800 W/m 2 as per IEC 60904-1 IEC 61829 standard shall be followed (in addition to the points noted above) for the requirement of the inspection equipment, inspection procedure, evaluation, minimum environmental conditions and reporting required for performing the outdoor IV curve testing. Note 1: Poor results may be expected where measurements are taken in low irradiance or where the angle of incidence is too oblique. Note 2: The maximum power current and voltage of a PV string are directly affected by irradiance and temperature and are indirectly affected by any changes in the shape of the I-V curve. In general, I-V curve shape varies slightly with irradiance, and below a critical level of irradiance, the curve shape changes dramatically. The details of the variation depending on the PV technology and the extent to which module performance has been degraded over time. Changes in the shape of the curve can cause errors in evaluating array performance, regardless of the method used to characterize string performance (I-V curve tracing or separate current and voltage measurements). Public Page 34 of 58 Inspection and Testing Guidelines for Solar PV Systems connected to the LV and MV Distribution Network CS-G2 7.7.2 PV Array Infrared Camera Inspection Procedure 7.7.2.1 General The purpose of an infrared (IR) camera inspection is to detect unusual temperature variations in operating PV modules in the field. Such temperature variations may indicate problems within the modules and/or array, such as reverse-bias cells, bypass diode failure, solder bond failure, poor connections, open strings, PID issues and other conditions that lead to localized high-temperature operation. Note: As well as forming part of an initial or periodic verification process, an IR test may also be used to troubleshoot suspected problems in a module, string or array. 7.7.2.2 IR Test Procedure For an IR camera inspection, the array should be in the normal operating mode (inverters maximum power point tracking. Ideally, irradiance should be relatively constant and more than 600 W/m2 in the plane of the array to ensure that there will be sufficient current to cause discernible temperature differences. Depending on the module construction and mounting configuration, determine which side of the module produces the most discernible thermal image (the procedure