System Topology Explanation

2-Pole HSP-D40（500/600/800/1000V PV）

Unilateral non-grounding: for floating PV strings, SPD suppresses surge between L+ and L-. Unilateral grounding: one PV busbar connected to PE, provides line-line & line-earth surge protection. Dual-stage protection: SPD in combiner box + SPD at inverter DC port, graded lightning protection.

3-Pole HSP-D40（1500V PV only）

Covers L+, L-, PE terminals, for 1500V utility solar farms. 3-way protection: L+↔L-, L+↔PE, L-↔PE. Works with DC switch & string fuses before inverter.

Universal Rules

• Graded protection: SPD at combiner box and inverter to lower residual voltage.
• Series fuse required before each SPD to avoid thermal runaway.
• 3P SPD mandatory for 1500V systems; 2P cannot be used on 1500V arrays.
• PE cables must be short, low-resistance copper wire for fast surge discharge.