Distributed Low Voltage Power Combines Efficient Lighting with Intelligent Controls
Tom Lombardo posted on July 10, 2016 |

A typical commercial building dedicates about one-fourth of its electrical usage to lighting. LED retrofit lights are more efficient than fluorescent tubes, but the LED driver circuits that convert AC line voltage to LED-friendly DC are only 85% - 90% efficient. Since LEDs are native DC devices, it makes more sense to run them directly off of a DC bus. Several companies, including Cisco, Cree, and Eaton, are developing standards for smart LED lighting using low voltage DC wires to carry both power and data.

Power management company Eaton recently unveiled several of its new lighting technologies at the LIGHTFAIR International (LFI) 2016 trade show. Among these innovations is the Distributed Low Voltage Power (DLVP) system, which combines intelligent lighting controls with efficient DC power distribution. I contacted Ken Walma, vice president and general manager of Eaton's Lighting Division, who gave me a technical overview of DLVP.


TL: I'm curious about Eaton's use of its own proprietary DLVP as opposed to the Power over Ethernet (PoE) standard, especially since Eaton is a partner in the Cisco Digital Ceiling, which is based on PoE.

KW: The Distributed Low Voltage Power (DLVP) system does use specific cables that were chosen based on their properties. DLVP low-voltage cables enable addressable daisy-chain connected loads by utilizing the full class 2 power levels and communications inside a single cable. The connected cables are made from commercially available standard components from manufacturers like Belden and TE Connectivity. Using a standard communications protocol and enabling a customary wiring architecture, DLVP low-voltage cables are simply the appropriate tool for the application. Eaton is the first to use these standard components for this application.

It should be noted that PoE is a physical standard defined by passing power and communications through the same Ethernet cable. Today, there exists no communications standard around PoE. Eaton is currently working with Cisco to gather industry support for a PoE communications standard that would create a more useful PoE industry standard.

Image courtesy of Eaton
Image courtesy of Eaton

TL: What are the technological advantages to DLVP compared to PoE?

KW: DLVP and PoE are simply different tools utilizing class 2 low-voltage power as a means of addressing market applications. As customers have different needs and objectives, Eaton is aligned with two distinctly different low-voltage systems to target different value propositions.

In alliance with the Cisco Digital Ceiling, Eaton offers the PoE system in support of the IoT vision where all building level systems converge into a single IP-based system. This is a “connected” system, which simplifies the installation using standard Ethernet cabling and techniques in lieu of traditional class 1 line-voltage materials and methods. These customers value a common infrastructure, seek building-level analytics and seek higher order building control strategies to promote human-centric lighting.

Eaton’s DLVP system is designed with the electrical contractor and facility manager in mind.  The DLVP system blends the benefits of both AC and DC power distribution to reduce the total installed cost of a lighting project by up to 20% while providing a completely flexible and electrically efficient solution.

Low-voltage power systems offer the opportunity to reduce system installation costs (through labor and miscellaneous material reduction) and complexity when compared to line-voltage installations with overlay control systems. While PoE and DLVP are both low-voltage power systems, they differ in a few aspects.

Wiring architecture - The DLVP system utilizes the maximum class 2 power level (up to 100 watts), which enables daisy-chain wiring of multiple addressable loads, where the PoE system utilizes homerun wiring for individualized power and control aligning with IT infrastructures where high speed data transmission is required.

System efficiency – The DLVP system utilizes a higher bus voltage and leverages a backbone of line-voltage, alternating current for its transmission properties to deliver system electrical efficiencies comparable to traditional line-voltage LED installations.

Commissioning simplicity – DLVP, like PoE, utilizes addressable light fixtures, but due to its distributed architecture, DLVP is able to restrict the number of available addresses per low-voltage power module to simplify the system configuration process. The DLVP system is designed to be installed and configured so simply that third party commissioning technicians are not required.

TL: What are the voltage, current, and power specifications of DLVP?

KW: Low-voltage power modules in the DLVP system accept 120-277VAC 50/60Hz and output multiple circuits, or busses, of class 2 low voltage power. Class 2 electric power is currently limited to a maximum of 100-watts and 60VDC by Underwriter’s Laboratory (UL) and the National Electric Code (NEC). These power levels are transmitted via a cable-connector system that is plenum rated and chosen specifically to handle higher power class 2 applications. Low-voltage LED light fixtures are integrated into the DLVP system with low-voltage controllers. These programmable controllers are powered by the low-voltage power module bus and support class 2 LED fixtures up to 75 watts.

TL: What kind of information travels over the DLVP bus? Is it just lighting, or can it also handle HVAC and other things that the Cisco Digital Ceiling promises?

KW: Information communicated over the DLVP low-voltage bus includes light level commands, occupancy status and daylight information. Low-voltage power modules interface with other building systems through a BMS interface that announces occupancy status and responds to external time clock, alert and demand response inputs.

TL: What devices are compatible with DLVP?

KW: The DLVP system is based around low-voltage power modules and LED lighting fixtures utilizing low-voltage controllers. Low-voltage power modules enable use of low-voltage control devices and sensors. Low-voltage controllers provide power to and enable communications with multiple types of LED light fixtures.

TL: How do the devices communicate with each other? (As in, what type of communication protocol is in place?)

KW: The DLVP system utilizes a distributed intelligence approach with certain actions occurring locally at the device (integrated daylighting, for example) and others reporting to the system and responding to commands (occupancy detection as an example). System communication is enabled via the same low-voltage plenum rated cables that provide power to the devices. Device communications on the DLVP low-voltage bus are based on an industry standard protocol, which is commonly used for wired and wireless communications worldwide.

TL: How does a user interface with the system?

KW: System interactions from the user perspective are through hand-held infrared personal remote controls and through wall-mounted push-button controls. The system also incorporates energy code compliant sensors for occupancy detection and inputs for time clocks.

TL: How does a facilities manager set up, control, and maintain the system?

KW: The DLVP system was designed to be very simple to layout, install and configure.  The basic concept for configuring the system is assigning addressable fixtures to available control zones. Assignment of fixtures to control zones may be accomplished through hand-held infrared programming remote controls or through simple switches located on light fixtures. To achieve energy code compliance, control devices and sensors (external or fixture-integrated) may be connected to the system. Once the system is installed and configured, it operates stand-alone following a “set it and forget it” mindset. There is no maintenance expected beyond that of typical lighting and control systems, but low voltage power modules provide a convenient centralized location for system maintenance and system reconfiguration if needed.

TL: Is there a plan to open the standard to other manufacturers, in order to make the technology more widespread?

KW: Eaton researched and developed the DLVP system over several years. Eaton will be the first to commercialize the system, but welcomed collaboration is likely to bring about a new industry standard surrounding the innovative design.

It's Déjà vu All Over Again

Today’s intelligent lighting market looks like the computer networking industry a few decades ago: a variety of topologies, cabling, and communication protocols, each with its own advantages and tradeoffs, depending on the application. Early networks were used to connect a central mainframe computer to a group of dumb terminals; as terminals were replaced by personal computers, intelligence became distributed around the network, calling for more robust communication protocols. The major players in the lighting industry have already embraced the distributed intelligence concept and they’re working together, so I suspect that it will take less time for a unified standard to emerge. That’s good news for facilities managers, consumers, businesses, and the energy industry.


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