guides
Surge Protection Device Selection Guide
Surge protection devices (SPDs) protect electrical equipment from voltage transients caused by lightning strikes, switching operations, and power system disturbances.
Surge Current Rating Selection
Select SPD rating based on location and exposure:
- Service entrance (high exposure): 200kA-300kA per phase
- Service entrance (standard): 100kA-150kA per phase
- Distribution panels: 50kA-100kA per phase
- Equipment protection: 20kA-50kA per phase
Protection Modes
Complete protection requires all modes:
- L-L: Line-to-line protection
- L-N: Line-to-neutral protection
- L-G: Line-to-ground protection
- N-G: Neutral-to-ground protection
Coordination Strategy
Implement coordinated protection:
- Higher capacity SPD at service entrance
- Lower capacity SPDs at distribution panels
- 10-20 foot separation between levels
- Cascade protection reduces stress on downstream devices
💡 FAE Insights
Frequently Asked Questions
1. How often should SPDs be replaced?
SPDs should be replaced when: 1) Visual indicator shows failure; 2) After major surge events; 3) Every 5-10 years depending on exposure. MOVs degrade over time from repeated surges even without complete failure.
💡 Decision Guide: Replace when indicator shows failure or every 5-10 years. Monitor status regularly.