1、 ATIS-0600012.01 ATIS Standard on - ELECTRICAL PRIMARY PROTECTION CONSIDERATIONS FOR BROADBAND XDSL SYSTEMS As a leading technology and solutions development organization, ATIS brings together the top global ICT companies to advance the industrys most-pressing business priorities. Through ATIS commi
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5、er Access transmission system on metallic access cables; Symmetrical single pair high bit rate Digital Subscriber Line (SDSL); Part 2: Transceiver requirements.315 ITU-T Recommendation G.991.1, High bit rate Digital Subscriber Line (HDSL.)416 ITU-T Recommendation G.991.2, “Single-pair high-speed dig
6、ital subscriber line (SHDSL) transceivers”.417 ITU-T Recommendation G.992.1, Asymmetric digital subscriber line (ADSL) transceivers.418 ITU-T Recommendation G.992.2, Splitterless asymmetric digital subscriber line (ADSL) transceivers.419 ITU-T Recommendation G.992.3, Asymmetric digital subscriber li
7、ne transceivers 2 (ADSL2).420 ITU-T Recommendation G.992.4, Splitterless asymmetric digital subscriber line transceivers 2 (splitterless ADSL2).41This document is available from the Alliance for Telecommunications Industry Solutions (ATIS), 1200 G Street N.W., Suite 500, Washington, DC 20005. 2This
8、document is available from the Institute of Electrical and Electronics Engineers (IEEE). 3This document is available from the European Telecommunications Standards Institute (ETSI). 4This document is available from the International Telecommunications Union. ATIS-0600012.01 3 21 ITU-T Recommendation
9、 G.992.5, Asymmetric Digital Subscriber Line (ADSL) transceivers - Extended bandwidth ADSL2 (ADSL2+).422 ITU-T Recommendation G.993.1, Very high speed digital subscriber line transceivers (VDSL).423 ITU-T Recommendation G.993.2, Very high speed digital subscriber line transceivers 2 (VDSL2).424 NFPA
10、 70-2011, National Electrical Code (NEC).525 Telcordia Technical Reference TR-EOP-000001, Lightning, Radio Frequency, and 60-Hz Disturbances at the Bell Operating Company Network Interface, Issue 2, June, 1987.626 Telcordia, GR-974-CORE Generic Requirements for Telecommunications Line Protector Unit
11、s.627 Telcordia, GR-3154-CORE Generic Requirements for High-Density Feeder Distribution Interconnection and Surge Protection.628 Telcordia, GR-1089-CORE, Electromagnetic Compatibility (EMC) and Electrical Safety-Generic Criteria for Network Telecommunications Equipment.629 UL60950, Safety of Informa
12、tion Technology Equipment.730 ITU-T K.44, Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents - Basic Recommendation.43 Definitions, Acronyms, it will conduct current once its breakdown voltage has been exceeded (it is a variable resistor model). 3.1.18 Posit
13、ive Temperature Coefficient (PTC) thermistor: A current limiting device, the resistance of which increases as a function of the temperature caused by the heating effect of the current and PTC resistance. 3.1.19 Primary Protector: Used to protect an equipment interface and wiring system located where
14、 it diverts most of the stressful voltages and currents from propagation into the equipment thus protecting inside wiring. It also minimizes voltage gradients within outside plant wiring but does not limit current in outside plant wiring. It is generally accessible, removable, and connected to equip
15、otential bonding. 3.1.20 Quiescent State (Off-State): The surge protector, while not being exposed to external voltages that would cause it to operate, should present low loss at transmission frequencies. 3.1.21 Thyristor: A semi-conductor device that conducts current by switching into a short-circu
16、it once its breakdown voltage has been exceeded. The thyristor is reset back into its high-impedance state once the current falls below its holding current value. 3.1.22 Transverse Voltage (also known as Differential or Metallic Voltage): A voltage between the tip conductors and the ring conductors.
17、 ATIS-0600012.01 5 3.2 Acronyms Access transmission system on metallic access cables; Symmetrical single-pair high bit rate Digital Subscriber Line (SHDSL); Part 2: Transceiver requirements 14. SHDSL is typically used as a transport technology to commercial customer locations due to its high-speed s
18、ymmetric characteristics. SHDSL can be used by applications that require symmetric access. The international standard for SHDSL is ITU-T Recommendation G.991.2, Single-pair high-speed digital subscriber line (SHDSL) transceivers 16. The highest signal frequencies for SHDSL are: 385kb/s 120 kHz; 784
19、kb/s 250 kHz; 1.56 Mb/s 500 kHz. ADSLx can transmit a high speed down-stream data rate up to 27 Mbps to the subscriber, a lower speed up-stream data rate up to 2 Mbps, and can coexist with Plain Old Telephone Service (POTS). When POTS and ADSLx coexist on the same twisted-pair, then a splitter/filte
20、r is required at the Network End (Central Office, Remote Terminal, etc.) and at the Remote End (Customer Location) to separate the POTS and ADSLx signals. The ADSLx technology is intended for applications such as internet access, multimedia access, and video on demand that can be provided by an asym
21、metric system. The standard for ADSL is ATIS-0600413.2009, Network and Customer Installation Interfaces Asymmetric Digital Subscriber Line (ADSL) Metallic Interface 2. The international standards for ADSL are the ITU-T standards ITU-T Recommendation G.992.1, Asymmetric digital subscriber line (ADSL)
22、 transceivers 17 and ITU-T Recommendation G.992.2, Splitterless asymmetric digital subscriber line (ADSL) transceivers 18. The ADSL2 standards are ITU-T Recommendation G.992.3, Asymmetric digital subscriber line transceivers 2 (ADSL2) 19 and ITU-T Recommendation G.992.4, Splitterless asymmetric digi
23、tal subscriber line transceivers 2 (splitterless ADSL2) 20. The ADSL2plus standard is ATIS-0600417.2007 (R2012), Spectrum Management for Loop Transmissions Systems 3. The international standard is ITU-T Recommendation G.992.5, Asymmetric Digital Subscriber Line (ADSL) transceivers - Extended bandwid
24、th ADSL2 (ADSL2+) 21. The highest signal frequency for ADSL and ADSL2 is 1.1 MHz. VDSLx is similar to ADSLx access but at higher data rates on shorter loop distances than ADSLx and can be symmetric or asymmetric. The VDSL standard is ATIS-0600424.2004 (R2009), Interface between Networks and Customer
25、 Installation Very High Bit Rate Digital Subscriber Lines (VDSL) Metallic Interface (DMT based) 5. The international standard for VDSL is ITU-T Recommendation G.993.1, Very high speed digital subscriber line ATIS-0600012.01 7 transceivers (VDSL) 22 and for VDSL2 it is ITU-T Recommendation G.993.2, V
26、ery high speed digital subscriber line transceivers 2 (VDSL2) 23. The highest signal frequency for VDSL1 and VDSL2 is up to 30 MHz (some versions stop at 8.5 or 17 MHz.) Table 1 - DSL Systems Technology Data Rate Mode Some Applications ISDN (Integrated Services Digital Network) 144 kbps (2B+D) Duple
27、x Voice and Data Communication HDSL,2,4 (High-Speed Digital Subscriber Line) 1.544 Mbps (T1) 2.048 Mbps (E1/J1) Duplex Duplex T1/E1/J1 Service, Feeder Plant, WAN and LAN access, internet server access SDSL (Symmmetric Digital Subscriber Line) Up to 2.048 Mbps (E1/J1) Duplex E1/J1 Service, Feeder Pla
28、nt, WAN and LAN access, internet server access SHDSL (Symmetric High-Speed Digital Subscriber Line) Up to 5.7 Mbps Duplex Same as HDSL, plus location access for symmetric servicesADSL (Asymmetric Digital Subscriber Line) Up to 9 Mbps Up to 640 kbps Downstream upstream Internet access, video on deman
29、d, remote LAN access, interactive media ADSL2 (Asymmetric Digital Subscriber Line) Up to 12 Mbps Up to 2Mbps Downstream upstream Internet access, video on demand, remote LAN access, interactive media ADSL2plus (Asymmetric Digital Subscriber Line) Up to 27 Mbps Up to 2Mbps Downstream upstream Interne
30、t access, video on demand, remote LAN access, interactive media VDSL (Very High Data Rate Digital Subscriber Line) Up to 52 Mbps Up to 7 Mbps Downstream Upstream Same as ADSL and High Definition TV VDSL2 (Very High Data Rate Digital Subscriber Line) Up to 100 Mbps Up to 100 Mbps Downstream Upstream
31、Same as ADSL and High Definition TV The transport capacity of the DSL systems depend on the physical characteristics of the twisted-pair cabling system such as cable length, wire gauge, impairments (example: cross talk, impulse noise, etc), and the presence of bridge taps and load coils. The transmi
32、ssion rate is constrained by the line attenuation that increases as the line length, wire gauge, and frequency increase. Figures 1a, 1b, 1c, and 2 demonstrate the typical differences in loop lengths at which each technology is capable of operating. 4.1 Pair Bonding (Non-Physical Layer Bonding) The u
33、se of more than one ADSL2plus or VDSL2 line typically two lines for residential service, and up to twelve lines for a business customer to provide service to a customer is referred to as pair bonding and enables much higher bit rates or service to longer lines. For a given loop length, bonding two l
34、ines approximately doubles both the downstream and upstream service bit-rates. Alternatively, for the same bit-rate, bonding two lines enables approximately 50% longer lines than using one line. Bonding, in combination with vectoring, could make 100 Mb/s up to 500m (1.64 kft) on 24 AWG and 40 Mbps t
35、o 1220m (4 kft) on 24 AWG service cost-effective for many more customers. ATIS-0600012.01 8 4.2 Performance Comparisons of Different xDSL Technologies The various technologies of xDSL have very different performance characteristic. Within each technology type, there are performance differences, i.e.
36、, synchronization rate or data rate, based on loop length as shown in Figures 1a, 1b, 1c, and 2 below. Figure 1A is based on data from Broadband forum (BBF) TR100 Table A.1-15; Figure 1B is based on data from BBF TR114 Table 46; and Figure 1C is based on data from BBF TR114 Table 62. Figure 1a - Rat
37、e and Reach Performance - ADSL2plus ATIS-0600012.01 9 Figure 1b - Rate and Reach Performance - VDSL2 profile 8d Figure 1c - Rate and Reach Performance - VDSL2 profile 17a ATIS-0600012.01 10 5 Available Primary Protection Technologies The following types of primary surge protection devices are common
38、ly used in the telecommunications network: Carbon Air Gap; Gas Tube; Gas Tube with Back-Up Air Gap (BUG); Gas Tube with Metal Oxide Varistor (MOV) Backup: Hybrid - Gas Tube with MOV; and Solid State. Performance testing of protection devices is described in Telcordia GR-974-CORE, Generic Requirement
39、s for Telecommunications Line Protector Units 26, and in Telcordia GR-3154-CORE, Generic Requirements for High-Density Feeder Distribution Interconnection and Surge Protection 27. The impulse breakdown voltage characteristic of these devices is illustrated in Figure 3 below. The breakdown voltage di
40、stribution comparison is shown in Figure 2 below. Figure 2 - Breakdown Voltage Comparisons Figure 5 100 V/us Impulse Breakdown Voltage(New Protectors / Full -20 to +65C Temperature Range)3104152903805451060020040060080010001200Carbon Gas Tube Solid StateBreakdown Voltage(Volts)Breakdown Voltage Dist
41、ribution ComparisonBreakdown Voltage(Volts)100 V/s Impulse Breakdown Voltage (New Protectors / Full -20 to +65 C Temperature Range) ATIS-0600012.01 11 Figure 3 - Impulse Breakdown, Gas Tube, Hybrid, Solid State 5.1 Carbon Air Gap Protectors These devices consist of two small carbon electrodes which
42、provide a small (3 to 6 mils) air gap between a conductor and ground. During a surge event, if the potential difference between the conductors and ground across the carbon electrodes exceeds the sparkover rating of the gap, an arc will be established, grounding the line conductor. If the surge is sh
43、ort-lived (e.g., a lightning stroke), the arc-over will be extinguished when the current in the conductor is reduced to below approximately 50 mA, allowing the protector to return to its open-circuited condition. During steady-state discharges of considerable duration (e.g., power cross), the air ga
44、p is permanently shorted, grounding the conductor and providing a low impedance path to ground. When the fault on the conductor is cleared, the carbon block protector must be replaced. Carbon air gap protectors are not recommended for use with modern xDSL technologies. These items may be difficult t
45、o acquire or replace. They may produce distortion or noise performance related issues with xDSL equipment. 5.2 Gas Tube Protectors Gas Discharge devices are switching overvoltage protectors that have a discontinuous voltage/current (VI) characteristic. Power loss occurs in the glow and arc regions o
46、f the Gas-Discharge Tubes (GDT) characteristic. By changing the formulation of the gas in a GDT, “regular” and “fast” devices can be fabricated. Fast GDTs offer lower impulse sparkover (at the expense of a shorter life for high surges wearout), but higher glow and arc voltage values. Typically, the
47、arc voltage of a fast GDT is about two to three times higher than a regular GDT arc voltage. Capacitance of the GDT is normally linear and only a few pF, and as a result has little or no effect on broadband signals regardless of the frequency. TimeVoltageGas TubeHybrid (Gas + MOV)Solid StateImpulse
48、Breakdown VoltageVoltageATIS-0600012.01 12 Figure 4 - Gas Tube Operating Regions When the voltage across the GDT conductors reaches its sparkover value, the GDT will enter into its glow voltage region. The sparkover voltage is dependent on the rate of voltage rise (dv/dt) across its conductors. A GD
49、T DC sparkover is characterized with a ramp rate of 100-300 V/s and addresses low frequency fault events such as AC power contact. GDTs are also characterized with faster rising ramp rates such as 1 kV/s to address fast-rising surge type events. The glow region is where the gas in the tube starts to ionize due to the charge developed across metal electrodes. During the glow region, the voltage across the GDT is constant and an increase of current flow will create an avalanche effect in the gas ionization. Should en
