April 18, 2023
Will traditional AC (alternating current) electrical systems be replaced soon? Fault Managed Power (FMP) systems might have what it takes to incite a revolution in electricity.
Until recently, the term "fault management" was mainly linked to IT network systems. But now, power can also be referred to as fault managed. In this article, we're going to dive into the world of fault managed power (FMP) systems. We'll learn about what they are, how they work, and how they’re transforming electrical systems in buildings today.
Fault management in power systems is an intelligent safety feature that monitors for, and detects, pre-defined faults. When a fault is detected, power is shut off almost immediately (within a few milliseconds) to prevent electrical shock, fire, or damage to equipment. This allows higher voltages to be safely carried along cables, which itself comes with many benefits. If you’re familiar with GFCI (ground fault circuit interrupters), you can think of it like a digitally controlled, high speed GFCI that protects against more types of faults, and also works for DC (direct current) power. Let us explain further.
Fault managed power systems were recently standardized by the National Electrical Code (NEC) in the US, and UL has published supporting standards. The most recent edition of the NEC (released in February 2023), contained the addition of Article 726. Article 726 defines a Class 4 rating, which can be applied to power systems with fault management, and other credentials. Thus, Class 4 power systems are also known as fault managed power systems.
If you’re familiar with the NEC, perhaps you know of the other class ratings it defines. Class 1, 2, and 3 ratings can be given to certain power systems that have power limitations built-in, and don’t require a fuse box or breaker panel. Power systems that are given the Class 2 rating provide suitable protection from both fire and electric shock, and they usually supply DC (direct current) power, as opposed to AC (alternating current) power. The disadvantage with using a Class 2 power system is that it is power limited to 100 W per branch circuit, and would thus suffer significant line losses if power were to be transmitted over long distances. You can think of a power system given a Class 4 rating as a high-voltage version of a Class 2 power system, but with more intelligence built-in. Both are considered safe from fire and electric shock, and can deliver DC power. The main difference is that Class 2 power systems are power-limited, whereas Class 4 systems are fault managed.
As for the outlines that UL released in support of Article 726, find them linked below:
Fault management in network and IT applications has been around for decades. The FCAPS model was introduced in the 1980s as a way to proactively take control of, and manage, network infrastructure; implementing the technology for it in network equipment essentially prevents major faults by identifying minor faults quickly.
Fault management in network infrastructure can either be active or passive. Passive fault management involves less network chatter than active fault management, so it’s often preferred.
The definition of a Fault Managed Power (FMP) Systems is “a powering system that monitors for faults and controls power delivered to ensure that the amount of energy that goes into a fault is limited.” Fault managed power systems are relatively new (and only recently standardized), so the technology used for them varies widely from company to company. However, regardless of the company, this technology must adhere to the standards set out in the NEC and by UL. Different companies simply have different technological methods of meeting the same standards.
These are four of the main similarities across all fault managed power systems:
Class 4, fault managed power systems can deliver DC power. There are many benefits to delivering DC power, the main one being that powering DC devices with DC power eliminates the need for inefficient AC to DC conversions, which are normally executed by converters located on integrated device drivers. In fact, providing DC power to DC powered devices can reduce their consumed energy by up to 40%. Additionally, many devices in a building are DC powered, including LED lighting, HVAC systems with variable speed motors, and all digital devices (Wi-Fi routers, laptops, phones etc.). In total, about 74% of electrical loads in homes need DC power to operate (if powering electric vehicles and HVAC equipment with a DC motor).
DC power also suffers less line losses along cables, so it’s more efficient to distribute over further distances (as opposed to AC power). For example, if you have a larger project that would involve long lengths of cable, distributing DC power (at higher voltages) along those cables would reduce operating costs and energy consumption.
Fault managed power systems should all monitor for these fault conditions, and stop power within a few milliseconds if any of these faults occur:
There are several benefits to power systems that can monitor for predefined faults. Fault management is primarily a safety feature that, among other benefits, permits higher voltages to be transmitted along cables (up to 450V in the current Class 4 standard). They are able to distribute higher voltages because the rapid shutdown of power (when a fault is detected) significantly reduces the risk of electrical shock and fire. The use of higher voltages comes with its own benefits. For example, cable gauges can be smaller when carrying higher voltages, resulting in lower project capital costs associated with cabling. Furthermore, fault management enables Class 4 systems to be installed by the same technicians who install PoE cabling (depending on local regulations), which can potentially eliminate the need for electricians during installation.
Fault managed power systems should all be able to deliver hundreds (or even thousands) of watts of power, at up to 450V. When compared to a Class 2 power system, which can only deliver up to 100VA (or 100W at up to 60V), Class 4 power systems (synonymous with fault managed power systems) can practically deliver up to 20 times more power. Class 4 systems don’t technically have a power limit, because there is no current limit, only a voltage limit of 450V.
A hybrid cable incorporates optical fibers (for data transmission) and copper wires (for power transmission) within the same jacket. The power transmission wires would ideally be part of a Class 4 power system so cables could be fault managed, and carry higher voltages, while being about 10 times thinner than cables carrying 48V power.
The main benefit of hybrid cables is that they enable long-distance power supply while ensuring high-speed data transmission. Additionally, similarly to Power over Ethernet (PoE), they reduce cabling required because, instead of needing separate cables for both power and data, one cable can be used for both. This could reduce project costs associated with cabling, as well as simplify cable management. Hybrid cables are a distribution medium for both Class 4 power and data for 5G, so they are extremely beneficial when used in telecom infrastructure.
As we mentioned, the technology involved in Class 4 power systems varies depending on the manufacturer. Because of this, in order to demonstrate how a Class 4, fault managed power system works, we’ll use Cence Power’s system as an example.
Step 1: In a Class 4, fault managed power system, a Class 4 transmitter is connected to the main power supply of a building (such as an electrical panel). It includes an AC to DC converter, and DC-DC converter.
Step 2: Up to 450V DC flows through fault managed cables, with the transmitter and receiver continuously monitoring for faults on either end of cables.
Step 3: Power arrives at a Class 4 receiver
Step 4: The DC power load (such as an LED light fixture or telecom cell) receives power.
See below for a diagram of how the Cence Power fault managed power system works.
Although they are only in their naissance, companies such as Cence Power have already begun to offer fault managed power systems. Fault managed power systems will pose strong competition for traditional AC power systems because they can provide just as much power, and do so more safely and efficiently. Thus, although it would take time, fault managed, Class 4 power systems could someday be the primary electrical system in buildings.
Fault managed power systems can be a suitable solution for electrical projects that would benefit from an efficient and powerful DC power distribution system. Telecom equipment, data centers, hospitals, and LED lighting projects in general, could all benefit from such a system, for example. Additionally, as buildings become smarter and the proportion of electrical loads that are digital increases, this option will become even more beneficial. If you’d like to read more about the benefits of buildings switching over to higher voltage DC power (or just DC power in general), check out our article called: 5 Reasons DC Should Replace AC in Buildings.