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HFC Powering Introduction CATV networks utilize its coaxial cable to carry the electrical power used by amplifiers, optical nodes, NID and any other active devices installed on the network. The electrical powering is provided by a Power Supply connected to the power line that transforms ordinary 110 Volts to a stable 60V or 90V 60Hz power source. Power supplies are installed in a pole mount or ground mount enclosure. In certain cases, enclosures will house more than one power supply to feed portions of the network with distinctive power sources. Batteries can be installed inside the same enclosure as the power supply or in a separate enclosure placed directly on top or under it. These batteries will provide power to the network for a limited amount of time, enough for a field technician to be able to install a UPS on the power supply. Monitoring devices can also be installed on power supply to remotely monitor and control every power source installed on the network. Power insertion The RF and AC are combined on the coaxial cable by using RLC circuitry (Resistor, inductors and capacitors) as illustrate bellow. The capacitor will acts as a short in high frequency (RF) and as an open circuit in low frequency (AC) while the inductor does the inverse. This circuit isolates the RF signal from the AC source and at the same time isolates the AC source from the RF signal source. You will find similar circuitry inside Power Inserters to isolate the power supply from RF signal, in Tap to allow the circulation of AC from the Input to the Output or from the output to the input of the tap while preventing the AC to circulate on the drops, and on active devices such as amplifier or NID to separate AC and RF signal on distinctive path. © 2009 Bentley Systems, Incorporated. All rights reserved. Page 1 of 10 Active devices In a coaxial network, you will find different kind of equipment powered from the network itself. Each of them will draw a certain amount of current from the power supply and will only work within a predefined voltage level. The following is a list of active devices usually found on a CATV network: Optical node Coax amplifier Network Interface Device (NID) Addressable Taps Field Switching Module (CLEARPath) © 2009 Bentley Systems, Incorporated. All rights reserved. Page 2 of 10 HFC network powering On a Hybrid Fiber-Coax network, small portions of the network are fed directly by optical signal carried on a fiber and converted to electric signal via an optical node. These nodes usually provide signal to 500 house counts and depending on the population density, can cover a small area in city zone or a larger area in rural zone. Different powering scenario will need to supported the different HFC architecture on dense and rural area. Scenario A and B will usually be found in low to medium density area while scenario C and D will mostly be found in dense area. A. Single power supply feeding a single node B. Multiple power supplies feeding a single node © 2009 Bentley Systems, Incorporated. All rights reserved. Page 3 of 10 C. Power supply feeding multiple nodes D. Power supply feeding portions of nodes © 2009 Bentley Systems, Incorporated. All rights reserved. Page 4 of 10 Single node powering examples 1. Single power supply connected to the network through a power inerter. 2. Single power supply connected to the network through one of the optical node leg. 3. Single power supply connected to the network through one of the amplifier leg. © 2009 Bentley Systems, Incorporated. All rights reserved. Page 5 of 10 4. Multiple power supply feeding different portion of the network. 5. Dual power supply installed in the same cabinet feeding two section of the network. 6. Dual power supply installed in the same cabinet feeding two nodes. © 2009 Bentley Systems, Incorporated. All rights reserved. Page 6 of 10 Cross node powering example 1. Single power supply feeding two nodes with the use of power inserter and a splitter. 2. Single power supply feeding two nodes with the use of power with multiple outputs (up to 4). 3. Single power supply feeding two nodes by connecting the power supply to one leg of one optical node and joining the two networks with a jumper and two power inserters. © 2009 Bentley Systems, Incorporated. All rights reserved. Page 7 of 10 The power supply could also be connected to the leg of an amplifier or to an additional power inserter installed on the network. 4. Single power supply feeding two nodes connected together for coaxial redundancy. The cable at the input of the second node will carry power and RF signal. Plug-in will need to be calculated for the second node as it could become the redundant source in case of fiber outage. 5. Single power supply feeding two nodes with a jumper connecting the nodes power ports together. 6. Connecting two output tap ports together. © 2009 Bentley Systems, Incorporated. All rights reserved. Page 8 of 10 Devices connecting Power Supply to the network Power supplies can be connected to the network by using the following equipments: A Power Inserter One of the legs of an Amplifier (Power Port) One of the legs of an optical node (Power Port) Fuses / Power director are used inside these equipments to direct the power to the desired portion of network. With this method, it is possible to assign a power supply to the desired amplifiers or nodes. Bentley Coax requirements Power Jumper Cable placed between a power supply and a coax devices. This cable carries only AC to the network. Jumper data will be saved in the same coax cable table in Oracle, but a special parameter will allow the application to stop the RF calculation when encountering it. The Jumper cable can use any model of cable (P3-625, P1-750, etc.). Power Port Information specifying if an amplifier or a node has a port to which a power jumper can be connected to. A power port could also be added to a tap (exception) or on misc devices to provide more flexibility. Power Supply New power supplies come with multiple outputs (4 outputs). It should be possible to connect multiple cables to a power supply to feed multiple nodes. Power will be calculated as if the cable was split. Enclosure housing two nodes should already be manageable with our current version. They will only need to create a cell with an enclosure & a power supply and another cell with only the power supply to simulate the double supplies. © 2009 Bentley Systems, Incorporated. All rights reserved. Page 9 of 10 Power supply will need to be placed from the design menu as the other coaxial equipment. Power Inserter A Power Inserter can be placed anywhere on the network. A cable will join the Power Supply to the AC Power Inserter port and depending on how it is fused, it will be able to feed the network upstream and/or downstream. Power inserter will need to be placed from the design menu as the other coaxial equipment. RF redundancy Some optical nodes will include an RF input for redundancy purpose. This coaxial cable will also carry the power from one node to the other. Example: GainMaker® Optoelectronic Node 1 GHz with 40/52 MHz Split and RF Redundancy Power Block Power block are placed on coax cable to identify where the powering will stop. It simulates the removal of a fuse in a coaxial device. Power block are identified by the following symbol: |( Powering with Power block After having placed the power supply, the power jumper, the power inserter and the power blocks on the network, the user will activate the Powering command and select the power supply to start the power calculation. The application will start identifying all the active devices on the network by verifying the connectivity and stopping at every cable where a power block is found. Voltage and current will then be calculated and applied to every devices as well as the total current drawn from the Power Supply. Power Supply Boundary Power Supply boundaries are placed on the network to identify the area feed by a particular power supply. This method is used to avoid having to place individual power block at every location where the power supply stops feeding the coax network. Powering with Power Supply Boundary After having placed the power supply, the power jumper, the power inserter and the power boundary on the network, the user will activate the Powering command and select the power supply boundary to start the power calculation. The application will start by identifying the power supply inside the power supply boundary and will start calculating powering on the network inside the boundary. Voltage and current will then be calculated and applied to every devices as well as the total current drawn from the Power Supply. © 2009 Bentley Systems, Incorporated. All rights reserved. Page 10 of 10