Configuration of Huawei SUN2000-20KTL-M2 with Risen 545 W

Hello.

I have some doubts about the characteristics of the inverter SUN2000-20KTL-M2.

In the user manual, it is written that there is a DC switch, but it is recommended to install a PV circuit breaker with a rated voltage greater than or equal to 1100 V DC and a rated current of 15 A. Why? If there is integrated DC protection into the inverter with the DC switch, why should I install another one?

The second doubt is this: Even if I have to install the PV circuit breaker, why is the recommended rated current 15A? In the datasheet, it is written that MPPT current is 22A, while the short circuit current is 30A. According to this, I can install PV modules with MPPT current higher than 11A (but lower than 22A) and short circuit current higher than 15A (but lower than 30A). With this configuration, I must use one input per MPPT.

I need a clarification for this one. I installed already Risen 545 W modules with Impp= 17.22 A and Isc=18.23 A (under STC conditions). I am using 18 PV modules per string and having 2 different strings that will enter different MPPT. If this is not satisfying the characteristics of the inverter, I should change it immediately. Do you think that I will have a problem with this configuration?

Thank you.

PV circuit breakers are designed to protect against overload, short circuit, peak voltage or according to safety requirements. A DC circuit breaker can protect against overload and short circuit, but will not protect against peak voltage. A PV circuit breaker with a rated voltage greater than or equal to 1100 V DC and a rated current of 15 A can protect against peak voltage and other safety requirements. The integrated DC protection in the inverter can provide overload and short circuit protection, but there is still a risk of equipment damage or operator exposure to peak voltage. Installing an additional PV circuit breaker with the appropriate voltage and current parameters will provide additional protection and safety.

The rated current of the PV circuit breaker is 15A as this is the maximum allowable current required to perform the MPPT input for the selected system. The rated current of the circuit breaker is always lower than the maximum rated current of the PV module or other component of the installation. For the PV circuit breaker, the manufacturer recommended the use of circuit breakers with a rated current of 15 A.

The rated current of the PV circuit breaker should be adjusted to the maximum current that can flow through the PV line. To do this, add up all PV modules connected in series, which in your case is 18 x 17.22 A = 306.96 A. Then multiply this value by 1.25 (1.25 is a safety factor) and select the appropriate circuit breaker PV.