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Webinar 03 electrical installation of pv system


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Dr. Jeffery Lee Johnson's #SolarMOOC slide set on the electrical installation of a typical pv system

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Webinar 03 electrical installation of pv system

  1. 1. Electrical Installation of a PV System Making the Right Connections… Dr. Jeffery Lee Johnson CTO Todo-Solar Coahuila, MexicoEmail: Tele: (+52) 871 722 9522
  2. 2. Agenda• Resources• Assumptions and Background• The DC side of things – Choosing and Connecting the Panels in Series – Proper grounding – String combiners• Meeting in the Middle – DC connection to the Inverter – DC Disconnects, fusing and loading• The AC side of things – AC Connection to the Inverter – AC Disconnects, fusing and safety – Connecting to the grid• Summary and questions
  3. 3. Resources Doc Solstice’s Seasoned Sentiments Facts about Global PV installationsGlobal PV installations reached 27.7GW in 2011 That comes to 0.87 KW per second or 3 to 4 panels every second of the year PV Installations to Grow by up to 21 Percent in2012 Predicts IMS ResearchFor comparison , the entire grid capacityof the country of Mexico is 53 GW
  5. 5. Key Concepts and Assumptions• Follow the typical systematic Installation Procedures – Assemble and place racks – Mount and connect panels (DC) – Install combiner box (DC) – Connect DC disconnect (may be integrated) (DC) – Connect DC to inverter (DC) – Mount and configure inverter (AC/DC) – Install AC Disconnect (AC) – Connect inverter to grid via electrical center (AC) – Commission and test (AC/DC – Install or activate Monitoring system• You have an approved wiring diagram meeting specifications and needs of Locations – Routing, cable lengths, junction locations, fusing etc a• You have a complete parts list with prepared components
  6. 6. Electrical diagram: Generic SystemGeneral SchematicOne-line diagram
  7. 7. Sample SMA Wiring Diagram with external DC DisconnectCombiner Box
  8. 8. Sample SMA Wiring Diagram with integrated DC DisconnectCombiner Box
  9. 9. Sample System 3 strings of 10 panels 250W Siliken SMA sunny Boy SB7000US
  11. 11. Always use components rate for UL 1703 and IEC standards
  12. 12. Panel CharacteristicsMust know VOC, ISC, Vmp Imp Pmp, tolerances under STC and NOTC (preferably)
  13. 13. Characteristics of Panels in SeriesString is a series of panels with predetermined current and voltage output V = V1 + V2 + …Vn = ∑ Vi I = I1 = I2 = …In
  14. 14. Choosing Panels for Series layoutIssue Voltages for Panels in Series add linearly Ideally, every series has the same voltage output – butgenerally not true When combining series into Parallel Arrays at acombination node (such as a combiner box or Inverterinput), the voltage at that node is the weighted average ofthe series voltages favoring the lowest voltage presentImportant to balance your strings by equalizing thestring voltages as best as possible !
  15. 15. Balancing String VoltageLayout your panels in a similar environment of illumination & temperatureMeasure and Record VOC for each panel – assign a numbering system WHY measure VOC? Safer and varies WHEN? Measure during peak hours little with changes in illumination near solar noon when solar radiation is changing slowly With knowledge of panel characteristics, group them as best you can so each series will have equal or similar voltage – mix and match high /low performers
  16. 16. Installing panels – measure as you go! RETURN LINE Using return line measure VOC as you connect panelsWhy? To ensure each connection is secure and voltage sums as yougo! Panel interconnect issues are difficult to find after the factMake Sure panel connectors and cables are secured to rack
  17. 17. Physical GroundAll panels must have common physical ground and be grounded to racksAluminum frames are anodized (resistive)Most panels provide a ground connection holeOther technique is to use WEEBs or lugs – electrically connectpanel frames to rack and then ground rack
  18. 18. Combiner boxes – adding the current of stringsPV COMBINER BOXES ARE CURRENT ADDERS FOR STRINGS IN PARALLELCommon buss bar Each DC positive input Recommendation:• DC positive inputs (string) is fused before Pre-wire the box with• DC Negative inputs common output negative/ positive cables• Ground with mated connectors Fuse: 600 VDC with amp•Single outputs for rating > 1.45 operating amps Positive, Negative &ground Acts as string switch
  19. 19. DC routing• Have a DC cable routing plan – DC is on the roof or remote from inverter• Best solar cables do not need conduit but bundle them nicely using UV resistant cable ties• For esthetics and some codes, use metal conduit to distribute DC cables
  21. 21. DC DisconnectsStand-alone DC Disconnect Switch Integrated DC Disconnect Switch (Typically fused inside the inverter) • Fuse: 600 VDC with Amp rating > 1.45 x operating amps for each positive lead
  22. 22. Connecting DC to Inverter  Disconnect all DC power  Follow Inverter manual to connect positive, negative and ground cables* *Note: some panels are positively grounded … so pay attention  Turn on DC and measure voltage at all outputs and inputs  Turn off DC
  24. 24. Know your Grid Know which type of grid you are connecting to Most inverters are reconfigurable by dip switches or programming Line voltages vary so choose the operating output range that fits your grid conditions Inverter must be equipped with anti-islanding and must shutdown upon loss of grid power (grid connected systems)
  25. 25. The AC connection AC Disconnect Main Panel connection AC Outputs
  26. 26. AC DisconnectFused style • Locate AC disconnect near the inverter -- must be accessible • Fuses or Breakers must be compatible with grid voltage (240 VAC) • Amp repeating should be 1.45 x the output current under operating conditionsBreaker Style
  27. 27. Connecting to the GridTypical 240 VAC Connection Phase 1 Outputs from Inverter are: L1, L2 are positive feed lines Phase 2 Neutral Physical Ground Shut off AC power at main switch Shut off all DC inputs to inverter L1 L2 Connect Neutral and Physical Ground Connect L1 to Phase 1 using breaker Connect L2 to Phase 2 using breaker or use two pole breakers ** Phase numbering is for convenience
  28. 28. Commissioning• Check all connections• Follow manual for startup• Usual procedure is – For Startup: Turn on AC First then DC – For Shutdown: Turn off DC first then AC• After shutdown, ALWAYS wait 5 to 10 minutes before opening or working on inverter !!!• Capacitive load needs to discharge
  30. 30. Monitoreo de Bluetooth para Internet o iPhone, iPad 30
  31. 31. (Solar Energy made available to Everyone) Twitter: @TodoSolar Twitter: @TodoSolarKids