SPD Installation Problems & Best Practices

Common Issues and Solutions for SPDs in Practical Applications

Surge Protective Devices (SPDs) are critical for protecting electrical systems from transient overvoltages. However, several common issues occur in real-world installations:

• Insufficient maximum continuous operating voltage (Uc): Uc is lower than the grid’s maximum possible voltage, leading to SPD overheating or failure.

• Voltage protection level (Up) exceeds equipment impulse withstand voltage (Uw): SPD cannot adequately protect sensitive equipment.

• Poor energy coordination between multi-stage SPDs: Incorrect staging or lack of coordination reduces protection effectiveness.

• Degraded or damaged SPDs not replaced: Indicators show failure (e.g., color change, alarm), or physical damage (burnt, cracked), yet devices remain in service.

• False installation reporting: SPDs missing in critical panels (main/sub-distribution boards, equipment front-end), but inspection reports falsely confirm installation.

• Undersized grounding conductor: Cross-sectional area below code (Type I: ≥16mm²; Type II: ≥10mm²; Type III: ≥4mm², copper).

• Missing upstream backup protective device: No fuse or circuit breaker installed to isolate SPD faults.

These issues can result in:

• Ineffective surge suppression, causing equipment damage;

• Short circuits and fire risks from degraded SPDs;

• Ground conductor melting during surge discharge;

• Electrical fires due to unisolated SPD faults.

To ensure SPD reliability and safety:

• Select SPDs based on protected equipment’s Uw and installation location (e.g., LPZ0–1, LPZ1–2); ensure proper stage coordination;

• Install SPDs close to the power inlet of protected equipment;

• Use SPDs with status indicators or remote alarms;

• Implement regular inspection and timely replacement programs;

• Verify grounding conductor size and connection integrity;

• Always install code-compliant backup overcurrent protection upstream of SPDs.