IEC 61643-21:2025

Overview

IEC 61643-21:2025 - "Low voltage surge protective devices - Part 21" specifies requirements and test methods for surge protective devices (SPDs) connected to telecommunications and signalling networks. It covers SPDs intended to protect equipment rated up to 1 000 V RMS and 1 500 V DC, including circuits that also carry power (e.g., Power over Ethernet / PoE). Devices covered contain at least one voltage‑limiting component (clamping or switching) and are designed to limit surge voltages and divert surge currents. This second edition is a technical revision aligned with IEC 61643-01:2024 and adds new structure and safety requirements.

Key topics and technical requirements

• Scope & classification: Definitions, SPD types, mounting methods, end‑of‑life modes and configurations (single‑port, two‑port, multimode).
• Electrical requirements: Protection against electric shock, continuous current handling, measured limiting voltage, operating duty, insulation resistance, dielectric withstand, behaviour under temporary overvoltages (TOV), impulse durability and reset behaviour.
• Current‑limiting and safety: Tests and performance for current‑limiting SPDs, overstress/fault modes, short‑circuit protection for end‑of‑life.
• Transmission & signal integrity: Requirements and test methods for insertion loss, return loss, near‑end crosstalk (NEXT), longitudinal balance and Bit Error Ratio (BER) for LAN/telecom links.
• Mechanical, environmental & material tests: Mechanical strength, connections, creapage/clearance, heat resistance, tracking resistance, damp‑heat ageing.
• Type testing & test procedures: Impulse tests (8/20 current, 1,2/50 voltage, combination wave), impulse durability, impulse reset, AC durability, total discharge current, and reduced test procedures. Annexes provide example test circuits, threat parameters and application guidance.
• Marking & documentation: Manufacturer information requirements and data necessary for type testing and product labelling.

Practical applications

• Protecting telecom and signalling equipment (switches, routers, PoE devices, signalling controllers) from indirect and direct lightning transients and other transient overvoltages.
• Ensuring SPDs meet both safety and signal‑integrity requirements when installed in LANs, industrial control networks, railway signalling and telecom infrastructures.
• Supporting product design, independent type testing, certification, procurement and compliance verification for low‑voltage telecom surge protection.

Who should use this standard

• SPD manufacturers and designers (product development and compliance teams)
• Test laboratories and certification bodies performing type testing
• Network and telecom equipment manufacturers integrating surge protection
• System integrators, installers and asset owners specifying surge protection for PoE, LAN and signalling systems
• Procurement and regulatory compliance professionals

Related standards

• IEC 61643-01:2024 (general requirements for low voltage SPDs) - IEC 61643-21:2025 is intended to be used in conjunction with IEC 61643-01:2024.

Keywords: IEC 61643-21, surge protective devices, telecommunications surge protection, PoE protection, low voltage SPD test methods, IEC surge protection standard.