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Draft:Fault-Managed Power

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Fault-Managed Power

Fault-Managed Power (FMP), also known as Class 4 Fault-Managed Power, is a method of electrical power distribution defined in Article 726 of the 2023 National Electrical Code (NEC) as “a powering system that monitors for faults and controls current delivered to ensure fault energy is limited.”[1] FMP employs active fault detection, current limiting, and functional safety techniques to transmit higher levels of power over longer distances using small-gauge copper conductors, while maintaining safety comparable to traditional limited-energy systems.

History

The concept of FMP originated with Stephen S. Eaves, who patented the first system on July 14, 2014 (U.S. Patent 8,781,637). Eaves introduced the Packet Energy Transfer (PET) method, which delivers electrical power in discrete packets and continuously monitors for faults in real time.

Technology

FMP systems using Packet Energy Transfer divide electrical energy into discrete packets transmitted multiple times per second from a source to a receiving device. Each packet transfer is isolated by semiconductor switches and diodes that disconnect stored energy between transmissions. During each transmission cycle, the system performs real-time monitoring of line conditions; if a fault such as incorrect wiring, short circuit, or human contact is detected, energy transfer ceases within milliseconds.

This rapid fault isolation allows FMP systems to transmit up to 20 times more power than Power over Ethernet (PoE) while using similar cabling and installation practices. Transmission typically operates at voltages comparable to those of RFT-V systems (approximately ±190 VDC), but without fixed power limits per circuit. The technology supports multi-channel and interleaved packet delivery to enhance power density and reduce electromagnetic interference.

For compliance and safety, FMP systems are evaluated as integrated units, including the power source equipment, transmission cables, and powered devices. This system-level testing ensures controlled fault energy and safe operation even under fault conditions or accidental human contact.

Standards and Safety

Standardization of FMP began in 2020 with the publication of ATIS-0600040, defining fault energy thresholds and testing requirements.[2] Underwriters Laboratories subsequently developed UL 1400-1 for system-level certification[3] and UL 1400-2 for cabling requirements.[4] The 2023 edition of the NEC introduced Article 726, formally designating Class 4 Fault-Managed Power as a new power-limited circuit classification.[1]

UL 1400-1 incorporates fail-safe design principles aligned with international functional safety standards including IEC 61508-1 through -3,[5][6][7] ISO 13849-1 and -2,[8][9] and IEC 62061.[10] These standards require that FMP systems shut down within milliseconds to limit fault energy to safe levels.

In 2024, the FMP Alliance was established by Belden, Cisco, Panduit, Prysmian Group, and VoltServer to promote education, interoperability, and adoption of Class 4 power systems. The National Electrical Contractors Association (NECA) is developing NECA 726, Standard for Installing and Maintaining Class 4 Fault-Managed Power (FMP) Systems, to provide industry guidance for safe installation and maintenance practices.

References

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  1. ^ a b National Electrical Code (2023 edition). National Fire Protection Association, September 19, 2022, Article 726 “Class 4 Fault-Managed Power Systems”, ISBN-10 1455930342 / ISBN-13: 9781455930340.
  2. ^ ATIS-0600040 - Fault Managed Power Distribution Technologies – Human Contact Fault Analysis
  3. ^ UL 1400-1, Outline of Investigation for Fault-Managed Power Systems - Part 1: Safety Requirements. Underwriters Laboratories. Edition 7. Published Date: February 28, 2023
  4. ^ UL 1400-2, UL LLC Outline of Investigation for Fault-Managed Power Systems - Part 2: Requirements for Cables
  5. ^ IEC 61508-1, Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 1: General requirements
  6. ^ IEC 61508-2, Functional Safety of Electrical / Electronic / Programmable Electronic Safety Related Systems – Part 2: Requirements for Electrical / Electronic / Programmable Electronic Safety Related Systems
  7. ^ IEC 61508-3, Functional Safety of Electrical / Electronic / Programmable Electronic Safety Related Systems – Part 3: Software
  8. ^ ISO 13849-1, Safety of machinery — Safety-related parts of control systems, Part 1: General principles for design
  9. ^ ISO 13849-2, Safety of machinery — Safety-related parts of control systems, Part 2: Validation
  10. ^ IEC 62061, Safety of machinery - Functional safety of safety-related control systems
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