Network Remote Powering using Packet Energy
`Transfer
`
`25.2
`
`
`
`Stephen S. Eaves
`VoltServer, Inc.
`Charlestown, RI
`
`Stephen.Eaves@VoltServer.com
`www.VoltServer.com
`
`
`
`Abstract - Network remote power feeding provides energy to
`telecommunications
`equipment over
`existing
`conductors
`normally used to transport data. Existing and emerging
`applications for remote powering are discussed along with the
`safety aspects, standards and limitations of using signal lines at
`elevated voltages. Finally the added capabilities of a new
`“digital” power distribution technology known as “Packet
`Energy Transfer” will be discussed.
`
`
`I.
`INTRODUCTION
`to
`Network remote power feeding provides energy
`telecommunications equipment over existing conductors used
`to transport data; such as twisted pair or coaxial cable. A
`common
`implementation
`is
`the powering of Digital
`Subscriber Line Access Multiplexers (DSLAMs) over
`twisted pair signal lines from a telecom central office. More
`recently, a rapidly expanding Compact Base Transceiver
`Station (CBTS) market for 3G and 4G wireless networks is
`demanding innovative methods to minimize the capital
`equipment and maintenance costs for power conversion and
`energy storage components in small cabinets. Figure 1
`exemplifies a pole mounted CBTS, sometimes referred to as
`
`
`
`Figure 1: Pole Mounted Microcell
`a “microcell”, that would serve one or two city blocks. The
`unit draws approximately 300 Watts. Nearly a million
`
`CBTS installations are expected to be deployed over the next
`several yearsi,ii.
`Existing suppliers offer remote power feeding equipment
`designed to the specifications of IEC 60950-21iii and GR-
`1089iv. Approved devices are limited to a maximum steady-
`state power of 100 Watts per conductor pair; resulting in a
`maximum load current of 250mA. Multiple pairs can be
`combined to increase the power to the load device, provided
`that the pairs are individually monitored and protected. Most
`remote power
`feeding devices are applied
`to DSL
`installations. Their proliferation to newer applications has
`been hindered by safety concerns originating from the
`convention that data cables traditionally carry only low
`voltages and are segregated from power lines; meaning that
`technicians and the public may be caught unawares when
`these cables are used for hazardous voltages.
`Packet Energy Transfer (PET) is a new technology that
`“digitizes” power by separating it into a series of discrete
`time domains referred to as energy packets. Each packet has
`a first component dedicated to energy transfer, and a second
`component dedicated to data; containing a digital and analog
`verification signature. Using this new approach, higher
`levels of safety for personnel and equipment can be achieved,
`opening the door for more widespread use of remote power
`feeding. The technology can distinguish between a person
`touching the power conductors and the regular current being
`drawn by the load equipment; something that has not been
`achieved using traditional methods.
`
`
`II.
`ELECTRICAL SAFETY
`The reaction of human muscle tissue to electrical current is
`dependent on the magnitude and duration of exposure. The
`magnitude of electric current through the body is determined
`by the contact voltage divided by the human body resistance,
`with the bulk of body resistance being dominated by skin
`resistance. For exposures of 10ms or more IEC 60479-1v
`provides a guide to the effect of various current-duration
`combinations on the human body; the worst case resulting in
`ventricular fibrillation. For shorter exposure periods IEC
`60479-2vi is referenced. Traditional remote power feeding
`devices limit human body current to relatively safe levels
`
`978-1-4673-1000-0/12/$31.00 ©2012 IEEE
`
`Authorized licensed use limited to: Stephen Eaves. Downloaded on January 27,2021 at 03:12:10 UTC from IEEE Xplore. Restrictions apply.
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`Page 1 of 4
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`VOLTSERVER EXHIBIT 1014
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`

`

`25.2
`
`when the fault is from a conductor line to earth using an
`approach similar to traditional ground fault interrupter (GFI)
`devices found in homes. However, when the fault occurs
`from one conductor to the other conductor (line-to-line) the
`exposure is undetectable by existing equipment and can fall
`into a dangerous region. At the 400Vdc maximum line-to-
`line voltage allowed by IEC 60950-21 for voltage limited
`circuits, the human body resistance from hand to hand is
`assumed to be 2,000 Ohms. This results in a body current of
`200mA. Since conventional network powering devices are
`unable to distinguish between a person touching damaged or
`exposed line conductors and the normal load current, the
`
`Figure 2: DC Current Effects (IEC-60947-1)
`
`shock period will continue until the person manages to
`release contact.
`This is depicted by the vertical red line at 200mA in Figure
`2 where as exposure time increases (symbolized by traveling
`upwards on the vertical red line), it enters the DC-4 danger
`region where ventricular fibrillation is probable. The danger
`region is reached in under 1/2 second. It is also important to
`note that injury may occur not only from ventricular
`fibrillation but from a secondary injury if the shock is
`intensive enough to cause a “panic reaction” where a person
`could fall off a ladder or bump his head.
`
`III. PACKET ENERGY TRANSFER OPERATION
`PET has the unique ability to distinguish the difference
`between a person touching power conductors and the normal
`power drawn by the load. As described above, traditional
`remote powering devices or GFI devices do not have this
`ability. Similarly, PET can distinguish between the energy
`going to the normal load device and energy lost to a short
`circuit, high resistance connection or insulation breakdown.
` As shown in Figure 3, PET separates electric power into a
`series of low energy packets with a period of approximately
`1.5ms. A single packet does not contain enough energy to
`harm a person or do damage to equipment. However, by
`transferring hundreds of packets per second, high power
`levels are achieved. Each packet contains an energy
`component and a data component.
`
`Energy Packet
`
`Energy
`
`1.1ms
`
`Data
`
`0.4ms
`
`
`
`Figure 4: Packet Format
`
`The energy component is approximately 1.1ms in duration.
`During this time, the source is electrically connected to the
`load; allowing electrical current to flow. During the 0.4ms
`data component, the power lines are isolated from both the
`source and load by the PET electronics. If a person or other
`conducting object comes in contact with the conductors, or if
`the conducting path resistance is out of the expected range,
`high speed voltage and current measurement made by the
`PET transmitting device do not concur with the receiving
`device; indicating an improper transfer of energy from the
`source to the load. If the transmitter cannot verify that a
`proper transfer is made, power is typically discontinued in
`two packet periods, or 3ms. The data component may also
`contain a unique verification code that must be corroborated
`between the transmitter and receiver.
`Figure 3 depicts that in a PET protected circuit, the body
`current at the same 400Vdc falls well into the safe region
`where ventricular fibrillation in improbable. Moreover, the
`energy is low enough where an individual coming in contact
`will have much less probability of a panic reaction where he
`might fall off a ladder or suffer from some other secondary
`injury.
`IV. MICROCELL APPLICATION
`
`
`
`Figure 3: DC Current Effects (IEC-60947-2)
`
`In one proposed remote power feeding application, a
`central hub or aggregation node processes data from a
`
`Authorized licensed use limited to: Stephen Eaves. Downloaded on January 27,2021 at 03:12:10 UTC from IEEE Xplore. Restrictions apply.
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`Page 2 of 4
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`

`
`number of remote CBTS units (microcells) located on
`telephone poles, street lamps or buildings. Communication
`to the microcells may be accomplished over optical fiber,
`coax or CAT5 (ethernet) cable. When power for the
`microcell cabinet is derived locally, a number of provisions
`must be employed to safely distribute and convert AC power
`from the utility to the DC power used by the microcell.
`Figure 1 depicts a typical installation with conduit run, utility
`meter, disconnect junction box and DC power plant with
`batteries supplying a 300W CBTS.
`Many service providers target at least four hours of battery
`back-up for the base station to support emergency services
`(911) during a utility outage. The service providers plan for
`the deployment of portable generators during extended
`outages where the batteries would be fully drained. In
`reality, limitations on cabinet weight and volume often
`reduce the installed battery capacity, and the logistics of
`deploying generators to hundreds or thousands of pole
`locations in severe weather results in wide spread service
`loss. Maintenance of the thousands of batteries in a CBTS
`network is intensive, particularly when the units are installed
`in metropolitan areas where the technician deployment cost
`alone (truck-roll) can reach $1,000 per visit.
`The alternative of remote power feeding places the DC
`power plant and batteries at the aggregation node. The -48V
`DC plant voltage at the node is stepped up to +/-190V by the
`remote power feeding source and distributed to the microcell
`units over CAT3, CAT5 or other copper cable. A power
`converter at the microcell down-converts the +/-190V back
`to -48V to power the base station. In the “digitized”
`convention of Packet Energy Transfer, the source converter
`is referred to as a “transmitter” and the destination converter
`is referred to as the “receiver”. A single channel, 300W PET
`transmitter/receiver pair is depicted in Figure 5. The PET
`receiver unit can be placed inside the microcell enclosure or
`mounted externally adjacent to it.
`
`
`
`
`
`25.2
`meter, disconnect and DC plant cabinet be removed. The DC
`power plant and storage batteries for all the microcells would
`be centralized at the node cabinet. Since a DC power plant
`is already required at the node, much of the equipment costs
`have already been incurred or can be expanded by adding
`modular components, such as additional rectifier modules.
`The AC utility meter at each CBTS would also be eliminated
`in exchange for a single meter at the node; eliminating the
`cost of the meter and meter reading labor. Some CBTS
`installations do not include a meter, but these are often
`penalized by a utility bill pegged at a single peak power
`consumption rate.
`larger batteries and DC power plant
`The cost of
`components can be 30-40% less in the larger format of the
`centralized configuration, off-setting the cost of the remote
`power feeding equipment. Moreover, the larger format
`batteries often come in “telecom grade” versions that have a
`longer service life at lower cost.
`
`Service visits for battery maintenance are greatly reduced
`in a centralized system. Assuming a system of ten CBTS
`remote cabinets (microcells) per node, and a battery
`replacement interval of 3 years, there is an avoided cost of
`$1,500 to $3,000 per year in truck-rolls alone at $500-$1000
`per truck-roll. Finally and perhaps more importantly, battery
`capacity is no longer governed by the weight and volume
`limitations of the remote cabinets, and generator back-up is
`greatly simplified when delivered to a single aggregation
`node. Overall, customers can experience the availability
`during a utility outage previously known only with Plain Old
`Telephone Service (POTS) where reserve power originates at
`the central office.
`
`
`
`Figure 6 - Remote Powering of a Microcell using CAT 3 (telephone) Lines
`
`
`
`Figure 5 - PET Transmitter and Receiver
`
`
`
`
`
`
` A
`
` depiction of remote powering over existing aerial CAT3
`(phone) lines is shown in Figure 6. It is proposed that the
`
`Authorized licensed use limited to: Stephen Eaves. Downloaded on January 27,2021 at 03:12:10 UTC from IEEE Xplore. Restrictions apply.
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`25.2
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`
`
`V.
` CONCLUSION
`A remote power feeding architecture can significantly
`reduce capital equipment and maintenance costs in CBTS
`networks or other systems involving a central node that
`interfaces with multiple remote installations. The DC plant
`equipment and batteries are typically less expensive to
`acquire and install, and often more reliable in a centralized
`architecture. Additional benefits include reduced battery
`maintenance and POTS-like availability during utility
`outages.
`Remote powering using Packet Energy Transfer, offers an
`unprecedented level of safety for both personnel and
`equipment, making it an attractive alternative to local
`powering approaches.
`
`
`
`
`
`i “The Future of Infrastructure: Compact Base Stations”, In-Stat, June
`2010,http://www.in-stat.com/
`ii
` “Small Cell Economics and the Future of Mobile Broadband Services”,
`Wireless Week, June 2012
`iii “IEC 60950-21, Information technology equipment –. Safety –. Part 21:
`Remote power feeding”, International Electrotechnical Commission, Voltage
`Limited Equipment, Sect. 6.2, http://www.iec.ch/
`iv “GR-1089, Electromagnetic Compatibility and Electrical Safety - Generic
`Criteria
`for Network Telecommunications Equipment”, Telcordia
`Technologies, http://telecom-info.telcordia.com
`v “IEC 60479-1, Effects of current on human beings and livestock - Part 1:
`General
`aspects”,
`International
`Electrotechnical
`Commission,
`http://www.iec.ch
`vi “IEC 60479-2, Effects of current on human beings and livestock - Part 2:
`Special
`aspects”,
`International
`Electrotechnical
`Commission,
`http://www.iec.ch
`
`Authorized licensed use limited to: Stephen Eaves. Downloaded on January 27,2021 at 03:12:10 UTC from IEEE Xplore. Restrictions apply.
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