SPDA and SPD

According to IEC 61643-01:2024, a Surge Protective Device Assembly (SPDA) is an integrated unit consisting of one or more Surge Protective Devices (SPDs) combined with internal or external disconnectors (such as fuses or circuit breakers), designed to ensure safe and reliable operation during surge events and under fault conditions.

1. Core Definition and Composition

·An SPDA includes at least one nonlinear component (e.g., metal oxide varistor/MOV or gas discharge tube) to suppress surge voltages and divert surge currents.

·It must incorporate disconnectors or overcurrent protection devices (e.g., fuses, circuit breakers), which can be internally integrated or externally specified by the manufacturer. These disconnectors safely isolate the SPD from the power system upon failure (e.g., short-circuit) to prevent fires or system damage and maintain power continuity.

2. Key Safety and Performance Requirements

·Short-Circuit Current Withstand Test: SPDAs must undergo rigorous testing to verify their ability to handle declared rated short-circuit currents (Isccr) without hazardous effects like arcing, combustion, or casing rupture.

·Dedicated Overload Test: This test simulates abnormal conditions (e.g., temporary overvoltages). The disconnector must interrupt current within specified times, forcing the SPDA into a safe open-circuit failure mode. Sample preparation varies based on protection modes (e.g., replacing voltage-limiting components to simulate worst-case scenarios).

·Temporary Overvoltage (TOV) Tolerance: SPDAs must withstand or safely fail under TOV events (e.g., caused by ground faults or neutral disconnections). The standard defines four TOV types, requiring SPDAs to either tolerate the overvoltage or fail safely (e.g., open circuit) to avoid fire risks.

3. Classification and Testing Methods

SPDAs are categorized based on their protective components, each with specific test requirements:

·Integrated Fuses: Refer to IEC 60269 series standards (e.g., for industrial, PV systems).

·Integrated Circuit Breakers: Refer to IEC 60947-2 (industrial) or IEC 60898 (household) standards.

·SPDs with Internal Short-Circuit Protection: No external disconnector needed.

· Composite Function SPDAs: Combine surge protection and short-circuit protection inseparably.

4. SPDA vs. Ordinary SPD

5. Design Purpose and Applications

·SPDAs address safety risks during SPD failure (e.g., short-circuit fires) by integrating disconnectors, simplifying installation, and enhancing system reliability.

·They are suitable for AC (≤1000 V) and DC (≤1500 V) systems, commonly used in photovoltaic power stations, EV charging facilities, industrial distribution, and other scenarios requiring high safety standards.

Conclusion

IEC 61643-01:2024 emphasizes system-level safety and reliability for surge protection. SPDAs represent a critical evolution by combining SPDs with disconnectors in a pre-validated assembly, ensuring safer failure modes and reduced risks. Manufacturers must redesign products to meet these enhanced requirements, while users benefit from higher security and simplified compliance.

For further details, refer to IEC 61643-01:2024 Sections 9.3.6 (short-circuit tests) and Appendix F (combined protection mode testing).