Article 726 Class 4 Fault-Managed Power Systems.

Fault-managed power systems are also referred to as packet energy transfer (PET), Digital Electricity (DE), Pulsed Power, and Smart Transfer Systems.
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Fault-managed power systems are also referred to as packet energy transfer (PET), Digital Electricity (DE), Pulsed Power, and Smart Transfer Systems.

Code Change Summary: New article provides requirements for Class 4 Fault-Managed Power Systems.

New Article 726 covers Class 4 Fault-Managed Power Systems.

In the 2023 NEC®, Fault-Managed Power (FMP) is defined in Article 100 as a powering system that monitors for faults and controls current delivered to ensure fault energy is limited.

In the electrical industry, “Fault-Managed Power” has also been referred to as Packet Energy Transfer (PET), Digital Electricity (DE), Pulsed Power, and Smart Transfer Systems. A fault-managed power circuit is also referred to as a Class 4 circuit.

According to informational note No. 1 in new Article 726, Section 726.1, Class 4 fault-managed power systems consist of a Class 4 power transmitter and a Class 4 power receiver connected by a Class 4 cabling system. These systems are characterized by monitoring the circuit for faults and controlling the source current to ensure the energy delivered into any fault is limited.

Instead of limiting the power source output to a certain threshold such as in Class 2 and Class 3 systems, the Fault-Managed Power system monitors the circuit in real time and limits the power available during a fault event. Communication occurs between the receiver and the transmitter and if all conditions are safe, power is delivered to the load. If a fault is detected, the FMP system will halt transmission within a fraction of a second.

Since power is only limited when a fault is detected, the FMP system is ideal for powering higher loads across extremely long distances.

Highlights in new Article 726 include:

Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2023 NEC® edition of NFPA 70.

2020 Code Language:

This article did not exist.

2023 Code Language:

726.1 Scope. This article covers the installation of wiring systems and equipment, including utilization equipment, of Class 4 fault-managed power (FMP) systems.

726.130 Terminals and Connectors.

(A) Listing. Connecting hardware used on Class 4 distribution systems shall be listed.

(B) Noninterchangeability. Connectors for Class 4 circuits shall be designed such that they are not interchangeable with non-power-limited sources located on the same premises.

(C) Guarding. Any junctions and mating connectors shall be constructed and installed to guard against inadvertent contact with live parts by persons.

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Article 726 Class 4 Fault-Managed Power Systems.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Based on the 2023 NEC, which of the following is true for terminals and connectors used on Class 4 systems?

A: Connectors for Class 4 circuits shall be designed such that they are not interchangeable with non-power-limited sources located on the same premises.
B: Terminals for Class 4 circuits shall be interchangeable with non-power-limited sources located on the same premises.
C: Mating connectors shall permit inadvertent contact with live parts by persons.
D: Junctions and mating connectors shall be installed to allow inadvertent contact with live parts by persons.
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