Surge Protective Device (SPD) Buying Guide for Global Procurement
Specifying surge protective devices starts with the SPD type and the standard it is tested to. Type 1 (T1) devices are tested with the 10/350 µs impulse (Iimp) for service entrances exposed to direct lightning; Type 2 (T2) devices use the 8/20 µs waveform (In / Imax) for sub-distribution boards; Type 3 (T3) protect sensitive end equipment. AC devices must conform to IEC/EN 61643-11, while photovoltaic applications require IEC/EN 61643-31. The decisive performance figures are Uc (maximum continuous operating voltage), In and Imax (nominal and maximum discharge current in kA), and above all Up (voltage protection level) — Up must sit comfortably below the impulse withstand of the equipment being protected.
Equally important are the safety mechanisms: an integrated thermal disconnector to isolate an end-of-life module, a mechanical status indicator (green/red), and a declared short-circuit withstand with the correct backup fuse. For three-phase networks, confirm the protection configuration (L-N, L-PE, N-PE full mode) matches the earthing system (TT, TN-S, TN-C-S). For solar, DC SPDs must be rated for the full open-circuit string voltage (1000 V or 1500 V) and use a fail-safe Y design.