Expertise Reports

PV Plantseveral ( under construction) UK

Address:Andreas Iliou

81739 Munich

Technical Report

The present technical report is a Draft How to prevent Errors upfrontThis PV Parks with 4 transformers has similar installation with EARTH MAIN LOOP.( as future Projects )

The Park was installed (2014 ) Transformers

An analysis was conducted from September towards November 2015

Bonding,Earthing,Grounding....

with non combination of Main circulation loop and local Earthing Rod or 230 V AC supply we don t get the right Voltage level to trip the circuit breaker from Camera supply , otherwise a 16 A circuit breaker needs 5- 8 x times the amount of it s rating = 16x 5 least 80 A ( measured only 11A )

So without Earth leakage tester the system could start burning without notice ( 30mA is enough ) Iso fault.

in here the Main Ring loop 80 100mA increased through Minus Plus Cabling from Transformerstation

Conclusions:

Following action were implemented ( inside Transformer/Inverters)

-Earthing Panel via db board ( bigger Path back to source ) not via 230 V AC cables

-Earthing Panel via Earth Bar

-Earthing DB Board and Earth Bar ( all with 16mm thinwire)

-Earthing J Boxes via V Shape Earthing ( sec. time using Plus/Minus armoured shield)

One solution is to connect the LV installation frames to an earth connection that is electrically separate from that of the substation frames.

However , in practice, this separation is difficult due to frame meshing in MV/L V substations. Consequently standard IEC 60364-4-442 states that the L V installation frames can be connected to the earth connection of the transformer substation frames if the voltage Rp Ih MT is eliminated within the stipulated times.

Measurements regards Soil resistivity in prev. Installation during Comissioning.

How Earth Rods of module arrays/ frame can decrease Earthing values, better Bonding and betterGrounding of nearbye substations possible.

Different building codes, different countries , different values different Earthing standardsone common Problem in PV Installations.

MPPT value and only Common Grounding value will increase performance and also can get rid offatal Isolation faults and immediately fuses will blow.Instead a weak Grounding can result in ongoing Isofaults without disconnecting from Main supply line which will result in fire ( in near future ).

Values can be set and a much smoother operation can be achieved which will result in up to 25%more energy as frequently switched ON/OFF supply will create surges and result in many losses due to unwanted malfunctioning of circuit breakers which are very narrowly selected.

A DC circuit breaker is in between 1,2 towards 1,4 x times the rated capacity of the string , wired inside combiner boxes. So an array with 8 A roughly is between 10- 15 A circuit breakers supplied.

Overvoltages due to lightning striking the upstream MV network

When lightning strikes the MV network, a wave is transmitted to the live conductors on the L V side as a result of capacitive coupling between the transformer windings.

In view of the waveform of these overvoltages, the surge limiter is effective on the conductor to which it is connected. Consequently , regardless of the earthing system, we strongly recommend that surge arresters be installed at the origin of the L V network, between all live conductors and the earth, if there is a risk of the upstream MV network being directly struck by lightning (case of overhead lines) and especially if the L V network is also at risk. The surge limiter continues to perform its function for MV/L V disruptive breakdown.

u (kV) Ph/Ph Ph/PE Ph/N N/PE PE/deep earth System:IT 0.38 4.35 0.20 4.30 1.62TNS 0.36 4.82 0.20 4.72 1.62

Fig. 2 - overvoltages, caused by a lightning shock wave, measured at the end of a 50m cable supplying a resistive load.

Overvoltages due to lightning striking the building housing the installation

These overvoltages are caused by lightning current flowing through the buildings earth connection, particularly when lightning strikes a building equipped with a lightning rod.

In order to minimise these overvoltages on electrical installations, the buildings horizontal and vertical equipotentiality must be the best possible in low and high frequency . A single earth circuit (PE network) is naturally recommended, and use of metal cable trays with proper electrical connections (braids) is highly advisable for distribution.

Typical surge arrestors in LV side ( can be replaced easily ) cheaper version must be completely removed everytime a surge occures.

Possible connection points can be seen as a Camera supply Point , if the Grounding substructure is to weak or to far away from Poles a Earth Rod can be applied after Measurements were done + the existing Earthing structure should be wired towards Camera Pole ( a blank wire should be used instead isolated version ) the big advantage is that the soil can be picked up and further introduced towards local Earthing Point.In case 1 Earth Rod is not enough ( Measurements have to be done ) a Triangle version within 3 mtrs have to be applied , to get better rid of surges/ leakage current coming from Main supply Camera 230 V AC supply line ( Noise gets filtered away very quickly in V- Shape style)max Point earth structure is less than 0,5 mtrs.

Can be seen as building but also as higher Points in PV Plants which must be bonded towards Transformerstation or Building or modules arrays ( think about trackers )

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a sample of Earthing Points with a street in between arrays and the earthing Rods supplied...this 2 substructures should be bonded several times in between

building and earthing,Grounding supply to further decrease Earthing values in PV Plant

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unsymmetrical PV field and Earthing Rods and Main earthing Loop supplied ( UK version )

getting rid of surges ( antenna from existing Transformer/Inverter station ) during switch ON/OFFfighting Fire with Fire via DC Main cabling

(armoured cabling from 1000 V DC supply )

before the Datacabling was THE COMMON EARTHING POINT running through All Combiner Boxes and therefore getting ALL leakage current back to it s source (600-800 mA ) stray currents with All surge arrestors burned down without those lucky ones which had a better Grounding from array ( leakage was carried away via frames module arrays ) and not via Common Grounding backwards to Inverter.

( emf friendly solution must be supplied with 2 seperate Earthing Point 1 Common Earthing and1 Common Grounding )

The least resistance in this case was the Frame structure , less leakage occurred and surge arrestors were within boundary of 0,5 mtrs.If 0,5 mtrs can t be supplied via Earthing Rods or Earth supply lines a V Shape configured system has to be supplied ( if measured and still not enough ) a Trinagle Shape Earthing roughly 3 mtrs apart must surround ( e.g Camera supplies or/and Combiner Boxes).

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Grounding required at All Points of Entry , Filters , DB Panels , Switch Gears etc etc

noise been generated on side regards Datacabling before Remedy

.a already written report regards 12 V DC supply like Camera or light sockets and the Noise been generated and floating back to it s source , which will make Pixels of Camera pictures filled with Noise .Remedy is possible but needs measurements wether Problems comes from PV site or Transformerstation via Main supply.

The Noise been generated via Camera or Datalogging supply will also ( cause of the same Panel been distributed ) infiltrate into other systems installed and interact with them.One Problem will cause a chain reaction ( like datalosses, losses of pictures, MPPT keeps on switching ON/OFF etc etc )If one of the MW Transformer is not happy with measured values this can also cause malfunction of other MW transformer Inverterstations a YO YO Effect.

A meshed system approach mostly common in Greece, Italy and Germany

Cameras wether shielded or not with Earth Rod combined , one Remedy in place.

When RFI, EMI, analogue currents are encountered or determined a threat to your controland communications systems, some immediately think ground rods are the answer to most ofthese issues as a most cost effective solution. Good effective management of these matters calls for the best application of up to date grounding/earthing and bonding methods.

One must remember that all ferrous metals that make up structural and electricalsystems can and often are nothing more than huge antenea for collecting RF and electro magnetic signals that can be even amplified through these structures and electrical pipes and cabinets etc.

Driving a ground rod (local Earth only ) could inadvertently set up a loop that could be worse than the initial problem. So always ensure your plant facility has a truly effective low impedence infrastructure to facilitate a direct path to your proven and tested system earthing/grounding plane.

Munich , November 2015

Andreas Iliou