Protection of photovoltaic systems

Photovoltaic arrays are costly to install and demanding in termsof technology.Their service life must be measured in decades tosee a return on the invested funds.Manufacturers usually provideabout a twenty-year guarantee for photovoltaic systems.

To provide trouble-free technology throughout its service life,it isnecessary to include comprehensive protection against atmospher-ic and induced overvoltage at the design stage to implement thetechnology into the project.Protection must be provided not only atthe output side of the inverter,but also at the photovoltaic panels.Solar photovoltaic arrays are usually installed on rooftops,or ona“greenfield“.

As for the anticipated risks (pursuant to IEC (EN)62305-2),director near lightning strikes are considered.Overvoltage or lightningstrike can bring about financial loss,and for photovoltaic systemsinstalled on rooftops where individuals could be working,injuryshould also be considered.

Photovoltaic system designs,including lightning and overvolt-age suppression,shall comply with the IEC(HD)60364-7-712standard (Electrical installations of buildings -Solar photovoltaic(PV)systems),technical specification CLC/TS 50539-12 (SPDfor specific application including DC-Selection and applicationprinciples -SPDs connected to PV installations)and standardIEC(EN)62305 (Lightning protection).

The core (key device)of the whole photovoltaic system is theinverter,so the lightning and surge protection should be focused on the inverter and,it should be incorporated into the wholelightning and surge protection system.Furthermore,photovoltaicunits and their bearing metal structures should be integrated intothe grounding design.

SPD selection for DC side:

Ucpvmaximum continuous operating voltage

Uocsre standardized test circuit voltage of PV String

Ucpv≥1,2×Uoc stc

lf separating spark-over distance “s”is kept-SPD PV Type 2 is installed

-If distance “I”between PV modules and inverter is longerthan 10m -SPD is installed on both sides of the DC line

lf separating spark-over distance "s"is not kept

-SPD PV Type 1 and Type 2 is installed

-It is always necessary to install SPD PV on both sides of the DCline