Quality assurance and safety aspects. Dipl.Ing. Udo Siegfriedt DGS-Berlin Brandenburg

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1 for small PV installations Dipl.Ing. Udo Siegfriedt DGS-Berlin Brandenburg

2 Introduction DGS Germanys first non profit association aiming a renewable and environmental friendly energy supply. Founded in1975 (DGS Berlin: 1982) Aims: to foster the usage of renewable energies and energy efficiency to establish a sustainable energy supply by means of information, education and political influence mediation between research, industry, installation and building trades, consumers and politics Approx members incl. 350 companies National agency of International Solar Energy Society (ISES) Magazine SONNENENERGIE, six times per year The DGS is representing renewable energies in the German Federation of Technical and Scientific organisations (DVT). other DVT-Members: DIN, VDI, VDE, VBI... for small PV installations Page 2

Technical consulting Expert opinions for courts and insurances Yield studies Review of operation data /

3 DGS-Berlin: Expert services and Solar School Technical Due Diligence Plant acceptances in cooperation with TÜV - Rheinland e.v. Technical consulting Expert opinions for courts and insurances Yield studies Review of operation data / re-simulation Short term Performance Ratio acceptance tests Reflection and shading analysis DGS Solar School worldwide DGS Manual Planning and Installing Photovoltaic Systems for small PV installations Page 3

4 PV-Installations Grid-tied systems Off-grid systems connection to public grid via domestic grid with storage without storage small devices DC system DC-AC system Hybrid installations with wind turbine with cogeneration engine with diesel generator for small PV installations Page 4

5 Large scale stand alone systems for small PV installations Page 5

6 Battery systems: DC and AC coupling Use of batteries demands additional safety measures (e.g. ventilation, fusing ) DC and AC coupled systems are connected different to the feed in point for small PV installations Page 6

7 (1) PV generator: series and parallel interconnected PV modules with mounting system (2) PV array combiner / junction box (incl. protective devices) (3) DC cabling (4) DC-main disconnect (5) Inverter (6) AC cabling Components of a grid tied PV-systems (7) Energy meter cabinet incl. meters for supply and feed in plus AC protective devices and grid connection for small PV installations Page 7

8 PV on pitched roofs Mainly roof-tiles Easy to mount Inverter often inside the building Most installation are not assessable without auxiliary means (ladders ) Roof is not in use for another purpose for small PV installations Page 8

including children have access Measures for electrical and mechanical

9 PV installation on flat top roofs Roof is often used for various purpose (laundry, playground) PV-installation is not separated or fenced, everyone including children have access Measures for electrical and mechanical safety for both people and installation is necessary for small PV installations Page 9

Isolation resistance Match PV generator and inverter Components Power dimensioning inverter Voltage adaptation,

10 Planning and sizing Determination of location and size of the usable roof area Location Yield assessment (using PVGIS), shading analysis Modules: size and characteristic values Choose concept Choose type and number of inverters Isolation resistance Match PV generator and inverter Components Power dimensioning inverter Voltage adaptation, number of modules per string Current adaptation, number of strings Optimization Block diagram for small PV installations Page 10

overvoltage protection AC safety technique, AC cable dimensioning Grid connection Energy meter, protection devices, switches

11 Check roof static, choose and size mounting system, note building law requirements Create a plan where to mount modules and hooks, cable routing Roof DC cable dimensioning, DC safety technique Junction box and DC main switch Cables, grid Planungsablauf Lightning and overvoltage protection AC safety technique, AC cable dimensioning Grid connection Energy meter, protection devices, switches Calculation, proposal Yield prediction Calculation of profitability With consideration of funding, taxes and interest for small PV installations Page 11

Module failure and thus partial or total loss of a String (Bypass diodes or connection of cells within a

12 Common failures and defects Failures according to the frequency of occurrence: 1. Inverter defects 2. Cable connections 3. String fuses 4. Module failure and thus partial or total loss of a String (Bypass diodes or connection of cells within a module) 5. Surge arresters 6. Isolation failure Modules Increasing: Theft Fire Inverter Mounting system Cables Failures in PV-plants Source: EuPD research Error rate for small PV installations Page 12

Alternating current / direct current AC Voltage Current (with phase shift) Sine curve of voltage and current Periodic zero crossing Arcs due to switching quench at the next zero crossing

13 Alternating current / direct current AC Voltage Current (with phase shift) Sine curve of voltage and current Periodic zero crossing Arcs due to switching quench at the next zero crossing Possibly phase shift between voltage and current DC Voltage Current No zero crossing Arcs don t quench automatically For PV: current depends on irradiation for small PV installations Page 13

Safe installation Generator junction box ( String diodes ) Isolators

certified components Proper planning regarding both yield and safety Earth

avoiding sharp edges, tight cable radius, Fused strings (positive and

Inverter and junction box mounted on flame retarding material Lightning

14 Safe installation Generator junction box ( String diodes ) Isolators String fuses DC main cable String fuses Isolators Inverter Use of certified components Proper planning regarding both yield and safety Earth fault and short circuit safe installation Protection class II Cable laying avoiding sharp edges, tight cable radius, Fused strings (positive and negative pole, DC-fuse) Correct use and assembling of terminals and plugs Inverter and junction box mounted on flame retarding material Lightning and overvoltage protection Good planning and craftsmanship! for small PV installations Page 14

15 Bad practice Installation on inflammable material Wrong assembling Tight bending radius or tight fixation No UV resistance Cable laying over sharp edges for small PV installations Page 15

16 Bad practice Components shall be assessable for service staff but not for everyone for small PV installations Page 16

17 Best practice: BOS components PV-cable (PV1-F) DC fuses, fuse holder, switches Latching plugs, no third party manufacturer Cable trays or UV resistant plastic stripes for fixation All components for DC applications regarding maximum voltage and current for small PV installations Page 17

Best practice: Modules and inverter Certified

clearly labeled Module installation regarding

18 Best practice: Modules and inverter Certified modules (IEC ) Certified inverters (VDE AR-N 4105 ) Sheltered inverter installation (no direct sun or rain) All components including cables clearly labeled Module installation regarding static behavior (wind loads) for small PV installations Page 18

people Firefighters can operate even if a PV system is installed In Germany:

19 Fire prevention and fire fighting Main protection goal No touchable hazardous DC-voltage inside a building in case of fire Safe fire fighting and rescue of people Firefighters can operate even if a PV system is installed In Germany: necessary distances given in regulation VDE 0132 for small PV installations Page 19

20 Measures to reach the given protection goal Organizational measures Information sign located at the house connection box or the main distribution board General plan for fire fighters Supplements to existing ground plan for fire brigade use Structural measures Fire resistant laying of DC cables DC cables outside the building Inverter mounted outside or at the outer wall or Technical measures Remote DC switch (fire switch) (Module integrated switch) (Protective extra low voltage) for small PV installations Page 20

21 Structural measures: cable laying (A.Häring, SMA) for small PV installations Page 21

22 Examples structural measures Use of fire resistant conduits DC cables outside the building Inverter mounted outside (sheltered installation recommended) Fire resistant conduit Adolf Würth GmbH & Co. KG Absender Titel TT.MM.JJJJ Seite 22 for small PV installations Page 22

23 Fire protecting walls Quelle: VGH OBO Bettermann Sufficient distance between PV-modules and fire protecting wall Cable crossing only protected (fire bulkhead) for small PV installations Page 23

24 Lightning protection, earthing, potential equalization for small PV installations Page 24

Commissioning of a PV plant In accordance with VDE 0100 part 610 and BGV A2 (electrical installations and equipment) a test has to be done for personal and operational safety.

25 Commissioning of a PV plant In accordance with VDE 0100 part 610 and BGV A2 (electrical installations and equipment) a test has to be done for personal and operational safety. A report has to record the measurement of: earth resistance open circuit voltage of each string short circuit current of each string (DGS: operation current) voltage drop at each diode/fuse isolation resistance of the PV-generator and DC main cable for small PV installations Page 25

26 Excerpt from commissioning protocol IEC Absender Titel TT.MM.JJJJ Seite 26

27 Operating & Maintenance How often Where What Who Daily Inverter Operating indicator Owner/operator Monitoring system Operating state (isolation fault) Analysis of error messages Remedy of faults Owner/operator Electrically skilled person Monthly Energy meter Yield Owner/operator Generator Optical inspection Owner/operator Frequently (4 year period) Whole system Follow up tests and measurements according to start up test (VDE , VDE ) Electrically skilled person for small PV installations Page 27

Safe working on flat top roofs Protective

(but most expensive) safety measure Consider

28 Safe working on flat top roofs Protective belt to a safe attachment point Temporary fence Distance to roof edge > 2m: barrier tape is sufficient Scaffold is the safest (but most expensive) safety measure Consider national regulations for small PV installations Page 28

Former quality checks have shown that the quality increases when an independent quality check is pronounced.

29 Quality Program A sufficient quality program has to ensure the quality of all components and the correct function of the whole system. All edge conditions have to be recognized. Only an independent control gives certainty that a PV-system fulfils all necessary quality requirements. Former quality checks have shown that the quality increases when an independent quality check is pronounced. Best results are given if the following items are included Yield Prediction / Site Evaluation Component Qualification Plan Checking Services Field / Commissioning Inspection Verification Of Yield Prediction Follow Up Inspections / Ongoing Monitoring for small PV installations Page 29

30 Conclusion For high yield and a safe operation of a PV system a proper planning with certified components for DC application and a good craftsmanship is inevitable The use of flat top roofs for other purpose must be considered For fire safety a high quality installation and certain structural measures can ensure low risks at economically justifiable costs A proper commissioning gives certainty that the PV system can operate safely and obtain the predicted yield A minimum of maintenance is necessary even for small PV-installations National regulations must be considered An independent quality control as it is performed for larger PV systems is too expensive for small installations A sufficient training for planners, craftsman and maintenance staff is strongly recommended for small PV installations Page 30

31 Thank You For Your Attention DGS-Berlin Brandenburg Dip.Ing. Udo Siegfriedt Erich Steinfurt Straße Berlin, Germany Tel.: +49 (0) Fax: +49 (0) us@dgs-berlin.de Internet: For small PV installations Page 31

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