Solar PV Connection Guidelines for Customers PDF

# Solar PV Connection Guidelines for Customers ## PW-PWR/G1 ### Table of Contents | Contents | Page | | :-------------------------------------------------------------------- | :---- | | Title Page...

# Solar PV Connection Guidelines for Customers ## PW-PWR/G1 ### Table of Contents | Contents | Page | | :-------------------------------------------------------------------- | :---- | | Title Page | 1 | | Table of Contents | 2 | | Table of Contents | 2 | | Title Page | 2 | | Table of Contents | 2 | | 1 Purpose | 4 | | 2 Scope | 4 | | 2.1 Notice to Users of this Guideline. | 4 | | 3 Abbreviations, Definitions of Terms & Key References | 5 | | 4 What are the Benefits of Solar PV Systems, Technology and Environment? | 8 | | 4.1 How much Sun is there in Qatar? | 8 | | 4.2 What are the principles of solar PV Technology? | 10 | | 4.3 How is the Design of a PV System? | 11 | | How are the PV modules grouped? | 11 | | How is the PV Design performed? | 12 | | What is a Utility-Scale PV System? | 14 | | Do I need a Civil and Mechanical Design? | 17 | | Can my PV System follow the sun's path? | 18 | | What are the Concentrating PV arrays? | 20 | | Is there a PV System for Desert Environment? | 21 | | 5 Who can Install a PV System? | 22 | | 5.1 Eligible Customers | 22 | | 5.2 Incentive Tariff Scheme Adopted in Qatar | 22 | | 5.3 Solar PV Systems fit Everyone | 23 | | 6 How can I Connect a Solar PV System to Kahramaa Network? | 23 | | 6.1 Overview | 23 | | 6.2 Connection Process Stages | 23 | | Stage 1: Preliminary Connection Approval (Grid Impact Assessment) | 24 | | Stage 2: Final Connection Approval | 24 | | Stage 3: Connect your PV to the Grid and Generate Electricity | 25 | | Key Steps in the Connection Process | 26 | | 7 Can I buy any Equipment in the market for my PV System? | 26 | | 8 Should I pay to connect my Solar PV System? | 26 | | 9 Which are the Responsibilities? | 27 | | 9.1 Which are my Responsibilities as an eligible customer? | 27 | | 9.2 Which are the Responsibilities of the Consultants? | 27 | | 9.3 Which are the Responsibilities of the Contractors? | 28 | | 10 Do I have to Maintain my PV System? | 28 | ### 1 Purpose These Connection Guidelines provide information for Kahramaa Customers, Consultants, and Contractors on the essential aspects which should be taken into consideration to connect a Solar PV System to the Low Voltage or Medium Voltage Distribution Network of Kahramaa. ### 2 Scope These Guidelines apply to the planning, design, implementation, modification, operation, and maintenance of Solar PV Systems. This document contains the basic principles of solar PV Systems and illustrates the connection process as per Kahramaa's specific conditions. Thus, this guide shall serve as a basis for Customers and their selected Consultant/Contractor in the design and decision-making process at all applicable stages. The technical aspects are not treated here but separately in the document “EP-EPP-P7/S1 Technical Specifications for the Connection of PV Systems to the Network", which represents the main reference document for the definition of the requirements that these generating facilities have to comply with in order to be connected to the Distribution Network. ### 2.1 Notice to Users of this Guideline. This document is for the use of employees of Customers, Consultants, and Contractors. Users of this guideline should consult all applicable laws and regulations. The 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. The document “EP-EPP-P7/S1Technical Specifications for the Connection of PV Systems to the Network” at any point in time consist of the current edition together with any amendments, corrigenda, or errata then in effect. All users should ensure that they have this document's latest edition uploaded on Kahramaa website. Finally, the user shall refer to Qatar's local rules and regulations, as well as to applicable International Standards mentioned in these Kahramaa's documents, unless differently indicated in other Kahramaa documents related to Solar PV Systems Regulations. ### 3 Abbreviations, Definitions of Terms & Key References | Abbreviations | Description | | :------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | AC | Alternating Current | | CBM | Condition base Maintenance | | CISG | Copper Indium Gallium Selenide | | CSP | Concentrated Solar Power | | DC | Direct Current | | GHI | Global horizontal irradiance | | IEC | International Electrotechnical Commission | | KVA | Kilo Volt-Ampere | | LV | Low Voltage (namely 220/127 V or 380/220 V or 400/230 V) | | MV | Medium Voltage (namely 13.8kV or 33 kV) | | MVA | Mega Volt-Ampere | | O&M | Operation and Maintenance | | PV | (Solar) Photovoltaic | | PW | Planning & Development Production Water Resource Dept | | QEERI | Qatar Environment and Energy Research Institute | | BIPV | Building-Integrated Photovoltaic modules | | BIPV | Building-Integrated Photovoltaic system | | Connection Point | Photovoltaic system is connected | | Consultant | A qualified consultant for the design of grid-connected solar PV Systems. | | Customer | The owner or tenant contracting with the competent department to supply the place, building or facility with electricity or water or both, whether a natural or legal person. 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. | | Distribution System | Qatar electrical infrastructure (lines, cables, substations, etc.) at 33 kV and below, operated by Kahramaa. The Distribution network can be either a 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 240/415V ± 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. | | GHI | Direct and diffuse irradiance incident on a horizontal surface expressed in W/m². | | In-plane irradiance | The sum of direct, diffuse, and ground-reflected irradiance incidents upon 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 | | Interface protection | Electrical protection part of the solar PV System that ensures the PV System is disconnected from the network in case of an event that compromises the integrity of Kahramaa's distribution network. | | Inverter | Electric energy converter that changes direct electric current to single-phase or polyphase alternating current. | | Irradiance | Incident flux of radiant power per unit area expressed in W/m². | | Irradiation | Irradiance integrated over a given time interval and measured in energy units (e.g., kWh/m²/day). | | Main Electricity Meter for Billing | It is the meter installed by KAHRAMAA for customers, which will utilize the feature of measuring the electric current in both directions to measure the amount of electrical energy exchanged (imported and exported) between the eligible customer and KAHRAMAA distribution network | | Maximum Available Active Power Output | This is the Active Power Output based on the primary resource (for example, sun irradiance) and the maximum steady-state efficiency of the Solar PV System for this operating point. | | 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) cell | The most elementary device that exhibits the photovoltaic effect, i.e., the direct non-thermal conversion of radiant energy into electrical energy. | | 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. | | Prosumer | A Kahramaa Customer with Solar PV system installed to Produce electricity and connected to Network | | 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 Meter | It is the smart metering installed at the output point of the solar PV System and measures the total energy produced from the Solar PV Units. | | Standard Test Conditions (STC) | Reference values of in-plane irradiance (1000 W/m2), PV cell junction temperature (25 °C), and the reference spectral irradiance defined in IEC 60904-3. | ### Key References 1. ES-M4 Qatar Transmission Grid Code 2. EP-EPP-P7/S1 Technical Specifications for the Connection of PV Systems to the Network 3. PW-PWR/G2 Safety related to the installation of Solar PV Systems, latest revision 4. QEERI Solar Atlas, [https://www.hbku.edu.qa/sites/default/files/qeeri solar atlas.pdf](https://www.hbku.edu.qa/sites/default/files/qeeri solar atlas.pdf) 5. PQ-PQQ-P1/G1- Guideline on the Documentation of the KM Management System ### 4 What are the Benefits of Solar PV Systems, Technology and Environment? #### 4.1 How much Sun is there in Qatar? Every day we receive thousands of times the energy we consume from the Sun, but solar energy is distributed on the Earth's surface, and thus large collection surfaces are required to exploit it. The sun's energy is variable and discontinuous in a certain area mainly for the following reasons: * Variability during the day from sunrise to sunset * Absence in the night periods * Seasonal variations * Meteorological conditions (clouds, fog, sandstorms, etc.) Outside the Earth's atmosphere, solar irradiation has an average value of 1367 W/m² ±3%, called Solar constant. The variation of ±3% is due to the seasonal variation of the Earth's distance from the Sun. From Figure 1, we can understand the effect of the Earth's atmosphere on incoming solar radiation: * A portion of the solar energy arrives directly to the ground (Beam or Direct radiation) * A portion is diffused due to cloud and water molecules present in the atmosphere (Diffused radiation) * The remaining portion is lost by reflection and absorption by various constituents of the atmosphere. Consequently, the trend of the solar radiation received at the ground level is partially unpredictable because it depends on the local weather conditions. However, if we consider historical data collected by meteorological stations, it is possible to have time-averaged data on an hourly interval, daily, monthly or yearly basis. The radiation in Qatar is high: the global horizontal irradiation exceeds 2117 kWh/m² on average. The global horizontal irradiation recommended for a PV installation should exceed 1460 kWh/m² on average. Figure 2 shows the average annual solar radiation received in Qatar referred from QEERI Solar Atlas. Several databases on solar radiation and climate data cover the world or specific regions. In Qatar, it is possible to refer to the Qatar Environment and Energy Research Institute (QEERI), part of Hamad Bin Khalifa University and the Qatar Foundation. The solar databases contain the Global horizontal, Direct solar radiation and Diffuse solar radiation on a horizontal surface expressed in kWh/m²-day. These data are normally available on hourly intervals, daily, monthly, and yearly basis or as a long-term average. #### 4.2 What are the principles of solar PV Technology? Solar photovoltaic (PV) technology is undoubtedly the easiest way to produce electricity from sunlight. It can be used for many purposes in households and all sectors that need power, such as commercial activities, factories, office buildings, and many others. Solar systems are based on devices that transform sunlight into electricity, the PV cells, which perform photovoltaic conversion. PV cells are composed of semiconductors designed to be exposed to sunlight and collect as much energy as possible. Not surprisingly, their shape is thin and wide. The most widely used PV cells are crystalline silicon (mono or poly-crystalline), whose shape is normally square or a pseudo square with edges trimmed, as shown in Figure 3, and whose thickness is usually more than 0.2 mm. Therefore, solar cells are very fragile and must be purposely protected in a rigid structure, namely a PV module. Several PV cells are assembled and connected in a single body with transparent front glass. The structure of a PV module resembles a sandwich because many layers tightly packed are necessary to protect the PV cells and give the necessary mechanical and electrical characteristics (see Figure 4). Presently, the crystalline silicon PV modules available in the market have a nominal power typically in the range of 300Wp to 400Wp or more, measured at specific irradiance and temperature called Standard Test Conditions or STC. Although crystalline PV technology is the most widely used, other technologies are based on depositing a thin layer of semiconductor on the front glass. The resulting thickness of this deposit is a few µm, and for this reason, the resulting products are called thin-film PV modules. Commercially available thin-film PV modules technologies use CdTe (Cadmium Telluride), CIS (Copper Indium Selenide) or CIGS modules (Copper Indium Gallium Selenide), or Amorphous silicon can be used. The higher costs of these expensive materials are largely compensated by the much lower quantities needed to obtain the photovoltaic conversion. Conversely, the efficiency of thin-film technology modules is normally lower than their silicon wafer-based crystalline counterparts (except for CdTe technologies, which have a similar efficiency level as that of Crystalline Silicon). Recent technology developments have led to bi-facial PV modules. These convert light captured on both the front and backside of the module into electrical power. It can, therefore (substantially) increase the electric yield of PV Systems depending on the specifics of the installation. The additional yield for bi-facial PV Systems depends on the tilt, height, and spacing of the modules, as well as the reflectivity of the ground: e.g. white foil, different soils or vegetation (further details available in “Best practice for designing a PV System" document). #### 4.3 How is the Design of a PV System? ##### How are the PV modules grouped? The PV modules have to be grouped and interconnected efficiently to deliver the energy required and permitted by Qatari regulations. They can be grouped in strings and then in arrays, as depicted in Figure 5. The grouping depends on the power and energy required and the voltage levels that can handle your inverter. ##### How is the PV Design performed? Initially, it is important to know your roof space available and your ground space (if decided) to install a solar PV System. The capacity of your PV System is limited to the values of the Qatari regulation and your space available. The tilt of your PV modules is important to capture as much irradiation as possible. In general, the fixed tilt arrays use the structures to orient the PV modules at a tilt angle that is fixed year-round. The PV modules are typically fixed at the site latitude angle +/- up to 20° to optimise annual generation but may be tilted at other angles to achieve specific performance and cost objectives. For example, lower tilt angles in the 5° to 20° range are sometimes used to reduce wind loading and mounting structure cost, to allow a higher power density of the plant, or to increase summer energy production if there are tariff incentives to do so. The design should consider the impact of module shading using suitable engineering analysis, and the shading must be avoided. On flat ground, the distance between PV modules having a given inclination can be calculated. The PV modules can be connected in series and parallel to form a PV array. The PV array provides energy that cannot be directly used since it generates DC electricity which is not compatible with electric appliances and the electric grid as these are based on AC electricity. The DC power coming from the PV array is thus converted to AC power to be fully compatible with the public distribution networks. This function is operated using specific electronic equipment called an inverter. The inverter performs several functions: mainly, it optimises the electrical operation of the PV array and transforms the DC power into AC power that can be used by the electric appliances or injected into the distribution network when necessary. According to many experts, in the category of distributed systems, PV Systems may be broadly classified into two types: * Small-scale * Utility-scale Figure 6 shows the general configuration of a Small-Scale or Medium-Scale Solar PV System. Besides the inverter, there is other equipment aimed to safeguard the distribution network (Interface Protection – IP), measure the energy produced and exchanged with the distribution network (Meters) and sort the power (AC switchgear). Such PV Systems are called Grid-connected PV Systems or Grid-tied PV Systems. The environmental benefits of a grid-connected PV System are evident: * The energy produced is 100% renewable and comes from the Sun. * The PV System does not produce any pollutants. * The energy produced can fully replace energy generated through fossil fuels, thus reducing emissions of pollutants and, in particular, greenhouse gasses in the atmosphere. Recent technology developments have led to bi-facial PV modules. These convert light captured on both the front and backside of the module into electrical power. It can, therefore (substantially) increase the electric yield of PV Systems depending on the specifics of the installation. The additional yield for bi-facial PV Systems depends on the tilt, height, and spacing of the modules, as well as the reflectivity of the ground: e.g., white foil, different soils or vegetation. Figure 7 shows a few examples of Small-Scale PV Systems on buildings. ##### What is a Utility-Scale PV System? Large-Scale PV Systems are also called Utility-scale PV Systems because their power contribution is comparable to that of the traditional power stations operated by electric utilities. The typical layout of a Utility-Scale PV-based System requires several transformers, inverters and PV arrays (Figure 8). The connection among these elements depends on the topology (configuration) used by the PV inverter. Generally, two topologies are used to connect the PV Systems to the internal grid of the PV System: central Inverter and multi-string Inverter. In the first structure, only one inverter is used to connect a PV array with the transformer. Commonly, this has a single stage of conversion (DC-AC). Meanwhile, the multi-string inverter has two conversion stages (DC-DC and DC-AC). The last configuration interconnects one string of PV modules to the internal grid AC grid of the PV System. The central inverter is the most used topology in large-scale PV Systems. The main advantages of this topology over the second one are: * competitive costs * robustness * low maintenance * reduced number of inverters in the field However, the multi-string inverter is used to enhance the control of the maximum power point. This could be necessary when the PV System is located on irregular surfaces. Moreover, this topology is used for each PV string, so the number of inverters increases compared to a PV System that uses only a central Inverter. ##### What is a Central Inverter Configuration? PV Systems designed with large centralised or inverters are common, particularly with multi-megawatt-sized systems. A typical centralised inverter design approach includes one or more inverters totalling, e.g., 500 kW to 4 MW installed together at an inverter station (in a housing container or on an equipment pad) with a medium voltage transformer. Most inverters have an output AC voltage in the range of 200 V to 1 000 V. The transformer steps the low AC voltage up to a standard medium voltage or high voltage level, such as 20 kV. Figure 10 shows an example of 1 MW centralised inverter layout using an N-S single-axis tracker. The inverters are centralised within the array (see the centre of the figure) to minimise the total lengths of DC cable. The figure shows the cables from the inverter station to PV string (or harness) combiner boxes distributed throughout the PV arrays. The MV or HV output cables exiting the transformer are routed underground to a substation shown north of the array. ##### What is a String or module inverter configuration? PV Systems may also utilise string or module-level inverters. Figure 11 illustrates one approach with a similar N-S axis tracking array system. String inverters are mounted in every third row of modules. Typical configurations range from 300 V to 1 500 V maximum DC voltage and single-phase or three-phase outputs in the 240 V to 480 V AC range. The output circuits are combined in protected harnesses, modules, or fused disconnectors and then connected to the LV side of an MV/HV transformer, as indicated in the figure. This configuration generally warrants using a higher quantity of MV transformers with lower kVA ratings than in the centralised inverter approach because the array power is distributed at lower AC voltages. ### Do I need a Civil and Mechanical Design? Unfortunately, you need to consider civil and mechanical design in your PV System, especially if they are Large-scale. Some of the main aspects to consider are described below: ##### Mechanical Loads on PV Structures The solar PV array support structures may be designed according to measured and documented site-specific conditions instead of loading requirements for PV modules. Other deviations may be permitted under engineering supervision and approved by the applicable manufacturers and local authorities. ##### Wind Local code governing buildings' wind-load calculations may be unsuitable or inadequate for PV arrays. PV array structures may be designed and rated to measure site-specific conditions and application-specific structural engineering calculations in lieu of local codes, where documented and approved by local authorities. ##### Thermal Expansion To account for thermal expansion and contraction, particular attention should be given to mounting rack length, module frame separation, cable management, and rigid mechanical connections of long linear spans. This may include the provision of expansion gaps for structures or expansion fittings for conduits and cable trays. ##### Flooding Where project sites are at risk of flooding, the height above the ground of modules, combiner boxes, tracker motors, and other electrical components should be considered. The mounting structures' type and construction should also consider the impacts of flooding, submersion, and site drainage. ##### Seismic Activity Where project sites are at risk of seismic activity, seismic loads on structures should meet the requirements of the International Building Codes or locally adopted codes. Where applicable, equipment standards with seismic qualification testing should be applied. Typical seismic considerations for PV Systems include pier loading variations based on soil classification, lateral loads on fixed or tracking array structures, strengthened concrete equipment pads, greater requirements for bolting of enclosures to pads, use of flexible conduit (particularly for transformers), and retainer screws for tracking support structures. ##### Corrosion Components in PV Systems are susceptible to corrosion from salt content in water, corrosive chemicals in the local atmosphere such as ammonia in agricultural areas, and numerous chemicals such as sulphates found in soils. Local corrosive sources must be considered, and appropriately protected components. This applies to PV modules, structures (both sub-surface and above-ground), cabling, enclosures, field-deployed inverters, and their housings. Protecting sensitive internal components from extreme humidity may be better protected with air-tight enclosures or space heaters. The corrosion design of steel piles may be based on an analysis of local site conditions, including a geotechnical evaluation of resistivity, pH, and levels of chemicals such as sulphates and chlorates. When cathodic protection systems are utilised, particular attention should be paid to the location of the cathodic protection system vents, as the emanating gasses can cause corrosion of nearby components. Polymeric materials used in plastic wire ties are also subject to corrosion and shall be chosen appropriately per the site and application conditions. ##### Access Rows of modules, particularly in very large and with fixed-tilt systems, can be long (e.g., greater than 500 m) with little spacing in between. With low-mounted structures, safe access from row to row may only be possible by travelling to the end of a row and around the adjacent corridor. Narrow row-to-row spacing may prevent safe access with a motorised vehicle, thereby limiting internal array access to personnel who must hand-carry the required tools and materials. These factors can be overlooked when there is a design objective to create a high-density array due to site limitations, but they should not be ignored. Where pads or housings contain large equipment such as central inverters and medium voltage transformers, roads must be maintained for appropriate vehicle access (trucks or cranes) and turn-around capability. This also applies to emergency vehicles and local fire codes, which may dictate the maximum length of contiguous arrays and the minimum width of vehicle corridors in each direction. ### Can my PV System follow the sun's path? If you would like to improve the energy yield and that your solar PV System follows the sun, there are some possibilities. More sophisticated and more costly. The options begin with a fixed tilt, normally for rooftops, followed by adjustable tilts (which can be done manually every season) and automatic single-axis and double-axis tracking systems for following the sun. These options are briefly described below. #### Fixed Tilt Arrays Fixed tilt arrays use structures that orient PV modules at an azimuth and tilt angle fixed year-round. Arrays are typically fixed at the site latitude angle +/- up to 20° to optimise annual generation but may be tilted at other angles to achieve specific performance and cost objectives. For example, lower tilt angles in the 5° to 20° range are sometimes used to reduce wind loading and mounting structure cost, allow a higher power density of the PV System or increase summer energy production if there are tariff incentives. Lower tilt angles may result in higher soiling losses depending on site conditions and, therefore, should be considered. Time of Use tariff incentives may also warrant orienting the arrays at an azimuth angle other than south (or north in the southern hemisphere). Designs should consider the impact of module shading using suitable engineering analysis. #### Adjustable tilt Arrays Adjustable tilt arrays are fixed-tilt arrays that can be manually adjusted once or more per year. The most typical adjustable tilt array uses a higher angle tilt setting for winter and a lower angle tilt setting for summer months. The use of adjustable tilt arrays has historically been uncommon in PV Systems, but more recently, there has been an increase in their use in markets and regions with low labour costs. #### Single-axis Tracking Arrays Single-axis tracking arrays employ structures that rotate PV modules along a single axis to follow the Sun's path. Figure 13 shows the rotation option on a single axis. Frequently, in large PV Systems, the structures rotate along the horizontal N-S axis, with horizontal E-W tracking. The distance between two different rows of PV modules is particularly important because, especially in the early morning and before sunset, reciprocal shadings may occur. A backtracking technology is used to