Grid Tie Solar PV Strings Overcurrent Protection

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MWAzhar

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Hi everyone, I am relatively new in solar PV systems so I would like to ask few questions regarding grid connected photovoltaic system mainly about the sizing of fuse since it is required to comply with the standard in my country.

For simplicity, let’s say I am designing a 10kWdc Solar array using 335W per panels . I designed the system to be 2 parallel strings connected to 1 MPPT inverter with 15 panels connected in series each string. This modern inverter has built in DC SPD and DC breaker.

Here are the solar panel’s datasheet

Voc: 41.32V

Isc:10.38A

Imp :9.72A

Maximum fuse rating 20A

My question here is, since the 2 strings are connected in parallel into 1 MPPT, does the Maximum fuse rating provided by the solar panel manufacturer also doubles? And what is the suitable size of fuse rating for each string?

Itrip > 1.5x Isc

Itrip< 2x Isc

Is my calculation below here correct?

Total Voc of array : 15x 41.32 = 619.8V

Total Isc of array : 10.38*2 = 20.76A

Maximum Fuse rating : 20x2 = 40A

1.5x 20.76 =31.14A

2 x 20.76 = 41.52 A

Therefore, Itrip for each string should be in the range of 31.14A to 41.52A ;

Since Maximum Fuse rating is 40A, I should use 40 A, 1000V rated fuse for both of the string?

Appreciate feedbacks.

 
UK spec inverters look for DC issues, so we havn't fitted DC string fuses for a very long time - just not needed. I suspect your inveter will work in the same way.

 
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