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ISRAEL Energy AuditAndreas Iliou - measurements analysis, connectors
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01Module Circuit Design
Different strings
Iso fault measurements
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Powador Inverters modules STP 210 18 Ud
It is highly important to measure one module only against frame , either isolatedwith wood or similar isolator
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Measuring + Pole and Pole seperate against frame or/ and structure
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01
Earthing structure several times earthed towards the roof structure , thereforeIf the wiring to bond with the earth near inverter is not big enough ,after
Kirchhoff s law, current will flow according the lowest resistance.
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7 Module Circuit Design Analysing
Measured 25,9 MOhm with normal Isolationtester Megger ~okIf still mounted on the structure
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8 Module Circuit Design Analysing
Measured (isolated) real values / 1 module but + and - shortcut
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9 Module Circuit Design Isolation fault
Measured 625 MOhm with Isolationtester HT 420
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10 Module Circuit Design Analysing/ImpedanceImpedance
The current will flow in any direction, if earth wire (back) is to small
UL = 25V0.71 Ohm (RS)
338 Ik
UL = 25V1.04 Ohm (RS)
230 Ik
UL = 25V0.18 Ohm (RS)
1315 Ik
230V +50A*0,71Ohm~265,5V AC
230V + 50A*1,04Ohm~282 V AC
230V + 50A*0,18Ohm~239 V AC
Overcoming earthing (Ri)and Impedance (Rn)problems-
-with a existing value of 1,02 OhmRn~ max 10,791 kW 3 phase can be realised
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01
Earthing with Aluminium corrosion protected
Different clamp variations
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01
Earthing with Aluminium corrosion protected
Lightning rods can be used to bond , without corrosion- like sample here
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14 Modules checked , earthing concept
Value to high 13, 79 Ohm measured, flow will divert into the Pillars
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15 Modules checked , earthin concept
Value to high 4,8 Ohm measured, flow will divert into the Pillars
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16 Modules checked , earthing concept
Value here 0,08 Ohm measured, flow will divert into the Pillars-The other earthing point not good
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17 Module 816W/m 25degrees angle
1. Row 2,4A ~ 7A
816 W 46,4 degree C
Cloudy but values ok
2 rows always checked with temperatures 44 degree C
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18 Bypass Diodes
Bypass diodes getting hotter, heating up- normal values
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19 Conclusion
-During dry period all measurements done showed > 199 Ohm
-When we poured water over the surface and tested with PV Benningvalues stayed longer on safe side
because of it s triggering capacity and adjustment regards PV
Megger testing device not purely for PV onlyEarth loop and Neutral Impedance has to be checked on site
- Earth Rod has to be done via Tri Pod or 45 degrees angled( wrong/false readings from Inverter )
During operationthe module somehow accumulated static loads.
With a massive grounding ( way below 1 Ohm) we can dischargequickly any static or impedance driven faulty readingsand
faulty Phantom Iso fault will disappear.The inverter if configured upfront Suisse Mode by that a emf friendly version
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20 Conclusion I
Equal to the new israely local requirements ( since 2012 )Earth wiring should be done via a aluminium wire only,
- The earthing structure won t corrode over time otherwisewe will face the same problem every year once the earth will
loose it s conductivity over time.- 10sqmm or 16sqmm are sometimes not enough it should be strong enough
to bring any problems ( leakage currents) back to source withoutstray currents involved direct or indirect.
- The surface of the installed m should not exceed 60. Afterwards the structure should be broken to let not to many modules ran parallel over the same area
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21Thank you Andreas Iliou
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