Page 50 - Security Today, January/February 2019

PoE Power Nomenclature
PoE
PoE+
4PPoE
Type 4
PoE Standard
802.3af (802.3 at Type 1)
802.3at (802.3 at Type 2)
802.3bt Type 3
802.3bt Type 4
Power Sourced (Provided) PSE
15.40W
30W
60W
100W
Power at end Device (PD)
12.95W
25.50W
51.W
71W
prior to procurement.
For both classified and non-classified environments, the next level
of security exists via access cards readers, smart doors, cameras, and software. These systems are one area where category cabling may not be appropriate. For many card readers, magnetic locks and magnetic jams, two wire applications still exist. The gauge of conductor and length of the runs preclude category cabling from being a suitable substitute. Building Codes and electrical codes are part of the consid- eration, as heavier gauges are needed to support the electrical require- ments for some of these applications. For some transmission require- ments, four pairs are simply overkill and fitting the necessary cabling within door jambs is already difficult at best. Adding three more pairs just to be adding them, just won’t work in these environments.
Beyond the doors, security cameras are in use in nearly all gov- ernment installations. The problem with the cameras is that in many cases, they are retrofits to existing installations or are a replacement for the older CCTV coaxial camera systems. Today, cameras need to have PTZ, clearer pictures and in some cases, need to have the ability to support facial recognition. Coax could carry image data packets over significantly greater distances than the 100m category cabling limit set by TIA/ ISO and IEEE. In addition to the extended dis- tances often needed, power is also necessary to support the camera. Power can be supplied either by an external power connection or via the switch with PoE. There are multiple levels and standards for PoE as shown in the table below.
There are several advantages to providing digital power to an end device:
• No need to run incremental AC power to the device.
• Power only needs to be backed up in the telecommunications area, additional battery backup solutions for edge devices is not
required.
• Some AC to DC conversions are eliminated resulting in lower
power losses.
• Single connections to devices.
Lending Support
These devices are supported by category cable. Just like in traditional electrical transmissions, the conductor size has bearing on the length supported. As these are Ethernet applications, most limit supported distances to 100 meters without some type of repeater or transceiver. There are, however, length optimized cables that can support both the Ethernet data transmission and the power well in excess of 100m. These length optimized cables are designed to support the lengths originally supported over coax, distances outside of the 100m range for 10/100/1000 Ethernet as well as the PoE portion. Underwriters Laboratory has verified these cables to fully support 200m for Gigabit applications with PoE+ and 850 feet for 10Mb/s Ethernet with PoE+. The distance alone eliminates the need for repeaters, transceivers, ad- ditional IDF or telecommunications areas making these cables highly sought after for longer distance PoE devices like cameras and Wire- less Access Points (WAPs).
For applications inside a building and places where cabling is congested, LP cables may be used. These cables are not necessary for smaller bundles. The NEC has provided ampacity tables to de- termine when in fact, these cables are needed. There is a misconcep- tion in the industry about when to actually use these cables. It is not
based on the amount of power only. The idea behind these cables is to stop the heat rise when multiple cables are bundled in a pathway. As they are more expensive than standard category cables, you can avoid the additional expense by keeping your bundle size under the NEC rating for the amount of power and gauge size of the conduc- tors, move to larger conductors (if possible), or use another form of mitigation. Where you can’t, these cables allow one to have the best of both worlds.
Most work areas should be installed with the expectation of sup- porting PoE applications. For years, laptops could not use PoE appli- cations, as the hard drive simply required too much power. However, with solid state drives and the advancements today, PoE workstations could very well be the norm soon. Likewise, many VoIP phones are designed to run while being powered over their Ethernet connections. For laptops that use wireless, there won’t be a PoE port available for them to use for power, but other devices are likely to make use of the PoE port.
Higher performing cabling systems like Cat 6A are an ideal solu- tion for long-term work areas with powered support. The fact that they can support 10GBASE-T over 100m is just a plus. If a work area is either temporary or used for terminal services alone, it may be prudent to use a Cat 6 cable, which will offer better power transmis- sion propagation than Cat 5E. For work areas outfitted with fiber for security reasons, it is still prudent to provide a 6 or 6A cable for PoE applications if security practices will allow copper.
The Fire Rating
Another consideration for cables outside of security is the life safety systems within the buildings. Circuit integrity cables are those cables that will allow data to pass for a period of time during a fire. The most common cables are those that carry a 2-hour fire rating, mean- ing that the cables will propagate signals for two hours during a fire event. This is accomplished via an outside jacket that “ceramifies” during a fire event to keep it from spreading flame and keep the cable from melting. Currently, this cable is specified for areas of refuge, the closing loop in closed loop fire systems, where fire system cabling crosses open/plenum areas and the like.
These cables are gaining traction in transport stations, airports, and other government installations. There are two designations for these cables, CI and CIC. CI is circuit integrity and CIC is circuit Integrity in Conduit. There are some that are both. There is also a tape that you can retrofit cables with to make them two-hour rated. This tape is ex- pensive, and it may be more cost effective to run new channels.
For all cabling considerations for government, it is in your best interest to look outside of a single vendor for the options available to you. The standards assure that transmissions will work and work well for all standards-based systems. If there are properties outside of the standards-based solutions, be sure that these properties matter before paying extra for them. For some solutions
that exceed the standards, there could be savings
to be had in other areas. If you aren’t really sure
what all of the parameters mean, silicate the ad-
vice of an RCDD.
Carrie Goetz is the CNID global technology direc- tor at Paige DataCom Solutions.
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