Speed Of Light Engineering

Effective design begins with overcurrent protection coordination. PV arrays can produce fault currents under short-circuit conditions, especially with parallel string configurations. String-level fuses must be sized based on module short-circuit current (Isc) with appropriate safety factors, while DC and AC-side breakers (MCBs/MCCBs) must ensure selective coordination. This prevents nuisance tripping while isolating only the faulted section.

Surge Protection Devices (SPD) are critical in regions with high lightning activity. In this scenario, the absence of Type II SPDs on the DC side allowed transient overvoltages to propagate into the inverter. Best practice involves installing Type I SPDs at the main distribution board (for lightning currents) and Type II SPDs at combiner boxes and inverter inputs to clamp switching and induced surges. Proper coordination between SPD classes ensures staged protection.