What are the different types of surge arresters and when to use each?

Surge arrester classification by type:

• Type 1 SPD (High-current arresters) : Designed per IEC 61643-1 for direct lightning strikes, utility switching surges at service entrance. - Test waveform: 10/350 microsecond (high-current impulse simulating lightning directly on power line). - Discharge current rated: 10 kA–200 kA per impulse. - Limitation voltage: 2000–4000V (higher than Type 2). - Application: Main distribution board, immediately downstream of utility meter/main breaker. Protects entire facility. - Example: Socomec PRARCO Type 1 rated 100kA/10µs for 400V three-phase.
• Type 2 SPD (Standard arresters) : Designed for switching surges, typical distribution surges from utility grid or internal load switching. - Test waveform: 8/20 microsecond (standard transient impulse). - Discharge current: 5 kA–20 kA per impulse. - Limitation voltage: 1200–2000V (lower than Type 1; faster response). - Application: Sub-distribution boards, equipment branch circuits. Provides secondary protection for zone-specific loads. - Example: Socomec LIMDIS Type 2 rated 12.5kA/8µs for circuit breaker feeder protection.
• Type 3 SPD (Sensitive load arresters) : Compact, sensitive transient suppressors for protection near end-use equipment (IT, instrumentation, HVAC controllers). - Test waveform: combination of 1.2/50 μs (open-circuit voltage test) and 8/20 μs (short-circuit current test). - Discharge current: <5 kA (lower energy capacity). - Limitation voltage: 600–1200V (lowest; maximum component protection). - Application: Control cabinet surge suppressors, PLC circuit surge modules, sensitive sensor protectors. - Example: DIN-rail surge module protecting 24V DC instrument circuits.
• Multi-stage protection strategy : - Type 1 (main board): catches highest-energy surges, protects distribution feeders. - Type 2 (sub-board): absorbs residual surges, protects critical equipment branch. - Type 3 (near load): final protection against remaining transients, shields sensitive electronics (PLC inputs/outputs, servo drives). - Principle: "defense in depth" ensures no single surge defeats system.
• Installation sequence : Type 1 at main (0m from entry), Type 2 at sub-board (30–50m distance), Type 3 at equipment (>50m distance per IEC 61643-1 topology guidelines).
• Combination arresters (Type 1+2) : Single device provides both 10/350μs and 8/20μs protection. Simplifies installation; used when space limited or single feeder protection required.

Socomec modular surge protection system (PRARCO Type 1 + LIMDIS Type 2 stack) tested per IEC 61643-11, covering 99.5% lightning strike scenarios. Optim-Elec designs multi-stage protection per installation lightning-risk zone (low/medium/high) and critical load inventory. Contact optim-elec.com for risk assessment.