Lightning and Surge Protection of Photovoltaic Installations. Leutron GmbH 2013 Leinfelden-Echterdingen, Germany

Transcription

1 Lightning and Surge Protection of Photovoltaic Installations 1

2 Lightning and Surge Protection for PV Installations 2

3 Safeguard from Risks Ups, that was the insurance policy of my house!! 3

4 Why Lightning and Surge Protection? Photovoltaic (PV) installations are endangered by direct as well as close-up strikes. The high voltages and currents which occur induce electric and magnetic fields. Distant strikes (> 1000 m) often cause capacitive impacts which normally represent no danger. The strong magnetic field of close-up strikes (< 500 m) induce surge voltages in the electric installation loops which may cause damages. At indirect strikes partial lightning currents flow through the electric supply lines as well as in the metallic frames of the PV modules. At direct strikes (without external lightning protection) the entire lightning current flows through the PV installation. This, in general, causes heavy mechanical damages. 4

5 Destroyed Inverter Source: solar.schletter.de Source: g+h Themenheft

6 High Transient Voltages and Currents induced by Partial Lightning Currents metallic module frame A i lightning i lightning lightning rod Magnetic coupling between lightning rod and PV module lightning rod Induced voltage at the coil formed by the series connection of the PV modules 6

7 Induced Impulse Currents in PV Modules distance 0.5 m distance 1 m distance 2 m induced pulse currents at different distances Induced impulse currents almost 8/20 µs primary induced lightning current at different distances 10/350 µs primary lightning current 7

8 Low-inductance installation of the d.c. lines Wrong large-area installation Right minimised-area installation 8

9 Normative Recommendations At new erected photovoltaic installations the applicable standards respectively directives on the lightning protection of equipment, installations and persons must be applied: IEC part 1-4 IEC :2002 Solar photovoltaic (PV) power supply systems 9

10 Extract from DIN VDE 0100 part 712 Solar-Photovoltaic (PV) power supply systems light Design and protection system of a PV installation, according to DIN VDE photovoltaic generator disconnection device converter d.c. surge voltage protection circuit-breaker earth leakage circuit-breaker a.c. surge voltage protection supply electricity meter SHU switch infeed electricity meter SHU switch 10

11 DIN EN supplement 2 Photovoltaic and Solar thermal installations Photovoltaic and solar thermal installations A lightning protection system configured for the protection class III corresponds to the normal requirements of photovoltaic and solar thermal installations. In special individual cases additional measures according to DIN EN (VDE ) might be necessary. Photovoltaic and solar thermal installations on buildings must not interfere with existing lightning protection systems. Photovoltaic and solar thermal installations have to be protected by separate lightning rods according to DIN EN (VDE ) point 5.2 and 6.3 against direct lightning strikes. 11

12 DIN EN supplement 2 Photovoltaic and Solar thermal installations Photovoltaic and solar thermal installations Photovoltaic and solar thermal installations have to be protected by separate lightning rods against direct lightning strikes. If a direct attachment can not be avoided, the effect of a partial lightning current injected into the building has to be considered. Inside the building a potential equalization at lightning strikes at the electric and IT systems is reached according to DIN EN (VDE ) paragraph 6. Shielded main lines at the generator should be used to reduce the induction of surge voltages. Cable shields with sufficient cross section can be used to carry partial lightning currents if a connection of the generator to the external lightning protection is inevitable because of a to small separation distance. The lightning current carrying capacity of the generator main line has to be taken care of. 12

13 VDE supplement 2 additional information for special constructions Photovoltaic and solar thermal installations Example of a separated lightning rod for a photovoltaic installation including the necessary measures of surge voltage protection 13

14 Lightning and Surge Protection of a Solar Power Plant LPZ 0 A LPZ 0 B LPZ 1 Type 1 SPD (class I) e.g. IPV 320/12,5 ka Type 2 SPD (class II) e.g. CT PV-T2/2+GDT/1000 Type 2 (class II) SPD e.g. CT PV-T2/2+GDT/

15 VDE Supplement 2 Additional Information for Special Constructions Photovoltaic and solar thermal installations Example of a separated lightning rod taking into account the separation distance according to 6.3 in DIN EN (VDE ) 15

16 Protection of PV Modules via Lightning Rods 16

17 Height of the Lightning Rods according to the Rolling Sphere Method R (radius of the rolling sphere) Protection class I II III IV M (mesh width) 5 x 5 10 x x x 20 Radius of the rolling sphere and mesh width in dependence of the protection class 17

18 VDE Supplement 2 Additional Information for Special Constructions Photovoltaic and solar thermal installations separation distance protection angle radius of the rolling sphere depending on protection class lightning rod shading line Example for several separated lightning rods taking into account the shading line 18

19 Isolated mounted Arrester Line 19

20 PV Installation in Berlin with External Lightning Protection 20

21 Lightning and Surge Protection of a PV installation on the roof of a building 1. PV installation without external lightning protection 2. PV installation with external lightning protection and sufficient separation distance 3. PV installation with external lightning protection and insufficient separation distance 21

22 1. PV installation without external lightning protection LPZ 0 A Type 2 SPD (class II) e.g. EL-T2/ LPZ 1 d.c. input Type 2 SPD (class II) e.g. CT PV-T2/2+GDT/1000 a.c. output meter, main distribution board DNO bounding service entrance box equipotential bonding strip Type 2 SPD (class II) e.g. EL-T2/

23 1. PV installation without external lightning protection Type 2 - DC Type 2 - AC 23

24 1. PV installation without external lightning protection Type 2 - DC Type 2 - DC Type 2 - AC Type 2 - AC 24

25 1. PV installation without external lightning protection generator junction box (if existing) d.c. isolation device TT system 230 V a.c. inverter TN system 230 V a.c. inverter > 10 m CT PV-T2/2+GDT/1000 *) CT PV-T2/2+GDT/1000 *) EL-T2/ ) EL-T2/ ) to the PV module frame *) up to U d.c V 1) at 3-phase inverters -> EL-T2/ ) at 3-phase inverters -> EL-T2/

26 2. PV installation with external lightning protection and sufficient separation distance LPZ 0 A LPZ 0 B Type 2 SPD (class II) e.g. EL-T2/ LPZ 1 a.c. output d.c. input Type 2 SPD (class II) e.g. CT PV-T2/2+GDT/1000 meter, main distribution board bounding DNO equipotential bonding strip service entrance box Type 1 SPD (class I) e.g. IPV 320/12,5 ka 26

27 2. PV installation with external lightning protection and sufficient separation distance Type 2 - DC Type 1 - AC 27

28 2. PV installation with external lightning protection and sufficient separation distance Type 2 - DC Type 2 - DC Type 2 - AC Type 1 - AC 28

29 2. PV installation with external lightning protection and sufficient separation distance generator junction box (if existing) d.c. isolation device TT system 230 V a.c. inverter TN system 230 V a.c. inverter > 10 m CT PV-T2/2+GDT/1000*) CT PV-T2/2+GDT/1000 *) EL-T2/ ) EL-T2/ ) to the PV module frame *) up to U d.c V 1) at 3-phase inverter -> EL-T2/ ) at 3-phase inverter -> EL-T2/

30 3. PV installation with external lightning protection and insufficient separation distance LPZ 0 A LPZ 0 B Type 2 SPD (class I + II) e.g. EL-T2/ LPZ 1 a.c. output d.c. input Type SPD (Class I + II) e.g. PP PV 1000 meter, main distribution board xxx DNO service entrance box equipotential bonding strip Type 1 SPD (class I) e.g. IPV 320/12.5 ka 30

31 3. PV installation with external lightning protection and insufficient separation distance Type 1 DC according to DIN EN , Beiblatt 5 Type 1 - AC 31

32 3. PV installation with external lightning protection and insufficient separation distance Type 1 DC according to DIN EN Beiblatt 5 Type 1 DC according to DIN EN Beiblatt 5 Type 2 - AC Type 1- AC 32

33 3. Protection suggestion with external lightning protection and insufficient separation distance generator junction box (if existing) shielded wiring d.c. isolation device TT system 230 V a.c. inverter TN system 230 V a.c. inverter power supply system 3x 230/400 V a.c. CT PV-T2/2+GDT/1000 *) CT PV-T2/2+GDT/1000 *) EL-T2/ ) EL-T2/ ) PP BCD TNS 25/100 or 4 pcs. IPV 320/12,5 ka to the PV module frame *) up to U DC 1000 V 1) at 3-phase inverter -> EL-T2/ ) at 3-phase inverter -> EL-T2/

34 PV Installation with lightning rods of the extended external lightning protection installation Source: Thormählen GmbH 34

35 SPD Type (class I + II) for protection of PV installations with system voltages up to 800 and 1000 V d.c. 35

36 PP PV 800 und PP PV 1000 Two-pole combined lighting current and surge arrester dc, class I and II. Applicable at the LPZ transition point 0A-1 and higher Test standard: IEC / EN Space required for installation: 36 mm Optional with remote signal contact 12,5 ka (10/350µs) per pole When applied in PV installations, these devices are placed inside the connection box of the solar generator and on the dc side of the inverter. 36

37 Selection and Application of Type 2 (class II) Surge Arresters in Photovoltaic Installations 37

38 Risks by Improper Design of the SPD panel Uoc <1000 Vc isolation fault against PE Ipv MOV 550 V corresponds to half PV voltage There is a fire hazard at the varistor due to overload 38

39 Risks by Improper Design of the SPD insulation fault inverter Insulation fault at the PV generator: - Overload of the SPD caused by excess of the max. permissible continuous operating voltage PV generator Entire voltage of the PV generator at the SPD at insulation faults! type 2 surge voltage arresters SPD configured for at least 50 % of the max. no-load voltage 39

40 Back-up Fuses offer no Protection insulation fault PV generator inverter The hazard of fire can not totally be excluded! A fire hazard at the SPD is not excluded no back-up fuses exist, because the shortcircuit current of the PV generator corresponds approximately to the nominal current. This makes a proper selection of a fuse impossible. type 2 surge voltage arresters 40

41 Y-Connection with 3 Varistors PV generator Uoc <1000 Vc DC inverter AC Insulation fault against PE MOV = Metal Oxide Varistor MOV MOV Aging of the varistors and frequent exposure to surges may result in a significant rise of the leakage current. Fault resistant Y-connection, However, even here a fire can not totally be excluded. 41

42 Y-Protective Circuit with 2 Varistors and a Spark Gap PV generator Uoc <1000 Vc DC AC inverter Insulation fault against PE MOV 1) 1) MOV= Metal Oxide Varistors 2) GDT= Gas Discharge Tube GDT 2) There is no overload at the MOV and no hazard of fire exists, because the total voltage of the MOV and the GDT exceeds 1000 V DC. 42

43 Solution: By Y-Protective Circuit PV generator inverter Fault-resistant Y-protective circuit, composed by two varistors and a summation spark gap Therefore no activation of the protective circuit caused by an isolation fault and no damage of the SPD This kind of protective circuit offers a completely non-earthed design even at very high d.c. voltages. No interference with the insulation monitoring thanks to the absence of leakage currents Solution: CT PV-T2/2+GDT/1000 type 2 surge voltage arresters U OC STC = Voltage of the no-load circuit at standard conditions for testing 43

44 Type 2 SPDs for Protection of Photovoltaic Installations with System Voltages up to 1000 V d.c. 44

45 CT PV-T2/2+1/1000 and CT PV-T2/2+GDT/1000 Item No Item No

46 CT PV-T2/2+1/1000 (Item No ) and CT PV-T2/2+1/1000-FM (Item No ) surge voltage arrester type 2, SPD Type 2 (class II) multi-pole complete unit consisting of basic module with pluggable protective modules fault-resistant Y-connection with metal oxide varistors (MOV) increased discharge capacity I n : 15 ka (8/20 µs) visual fault indicator by colour change green/red function control by optional potential-free remote contact (changeover contact) 46

47 Dimensions and Circuit Diagram Housing size 3 MW according to DIN CT PV-T2/2+1/1000 (-FM) 47

48 CT PV-T2/2+GDT/1000 Advantage: Type 2 SPD up to 1000 V DC and leakage current-free inverter PV generator CT PV-T2/2+GDT/1000 type 2 surge voltage arresters Basic circuit diagram 48

49 Diagram of Connections CT PV-T2/2+GDT/1000 L = cable length PV generator Uoc <1000 Vc DC AC inverter + PE CT PV T M CT PV T2 GDT M CT PV T M CT PV-T2/2+GDT/1000 Item no CLASS II CLASS II CLASS II CLASS II 1000 V DC Application at the d.c. side of the inverter and additionally with L > 10 m in the vicinity of the PV generator 49

50 Leaflet for PV Fitters [Lightning and surge protection of photovoltaic installations at buildings] Basically describes the technological requirements in terms of lightning and surge protection. 50

51 Leaflet for PV Fitters Lightning and surge protection for photovoltaic installations on buildings Situation A: Building has no external lightning protection system type 2 SPD optional SPD = surge protection device type 2 SPD optional inverter type 2 SPD optional optional: generator wire with functional earthing conductor Note: Often there are type 3 surge voltage arresters integrated into the d.c. and a.c. terminal of the inverter for protection. equipotential bonding strip 51

52 Leaflet for PV Fitters Lightning and surge protection for photovoltaic installations on buildings Situation A: Building has no external lightning protection system Recommended functional earthing of the metallic PV mounting rack Connection of the module frames and racks with the main earthing busbar of the building Cross section should be at least 6 mm 2 (Cu) or have corresponding conductance Mutual connection of all mounting rack rails with a wire of this cross section Laying of the functional earthing conductor in parallel as close as possible to the a.c. and d.c. cables and wires Reduction of the economic damages to the PV installation by application of surge protection devices and shielded wires at PV inverters and PV generators Before the set-up of a PV installation on a public building it has to be checked, if the building needs a lightning protection system according to the state's building regulations. 52

53 Leaflet for PV Fitters Lightning and surge protection for photovoltaic installations on buildings Situation B: Building has or needs an external lightning protection system zone 0A zone 0B (protection area) type 2/1 SPD* zone 0B (protection area) SPD = surge protection device s = separation distance inverter type 1/2 SPD type 2/1 SPD* down conductors Note: By early consulting of a specialist in lightning protection it is possible to prevent later module shadowing and direct connection. equipotential bonding strip 53

54 Leaflet for PV Fitters Lightning and surge protection for photovoltaic installations on buildings Situation B: Building has or needs an external lightning protection system Adherence to the separation distance (s) between the external lightning protection system (air terminals, down conductors) and the PV installation (modules, frames, cables etc.) Proper separation distance (s) and PV installation within the protection area of the external lightning protection system Application of type 2 SPDs at the PV generator and PV inverter Alternatively: Laying of single-wire double-insulated PV cables / wires in combined metallic cable ducts / protection tubes (at least 6 mm 2 (Cu) or corresponding conductance) Connection of the metallic cable ducts / protection tubes at both ends by special cable connection to the PV module frame and to the main earthing busbar 54

55 Leaflet for PV Fitters Lightning and surge protection for photovoltaic installations on buildings Situation B: Building has or needs an external lightning protection system No proper separation distance (s) and PV installation not within the protection area of the external lightning protection system Application of type 1 SPDs at the PV generator and PV inverter Alternatively: Shielding with lightning current carrying capacity for all wires Note: Induced partial lightning currents will only be decoupled at the main earthing busbar. The installation of further SPDs is necessary. Alternatively: Laying of single-wire double-insulated PV cables / wires in combined metallic cable ducts / protection tubes (at least 16 mm 2 (Cu) or corresponding conductance) Connection of the metallic cable ducts / protection tubes with lightning current carrying capacity at both ends by special cable connection to the PV module frame and to the main earthing busbar 55

56 SPD SPD Grid-coupled PV Installations Surge protection devices by LEUTRON SPD generator connection box string control box (optional) Circuit concept of a PV installation operating in parallel with the grid PV generator PV terminal disconnector SPD DC disconnector x n inverter inverter infeed meter home network supply utility main distribution board equipotential bonding strip 56

57 Basic Circuit Diagram of a PV System with Surge Protection solar generator inverter infeed electricity meter energy grid 57

58 58