ausgrid's underground high-voltage cable tunnels - providing p25 grn coverage using radio over...
DESCRIPTION
Ausgrid is investing more than $1 billion in the Sydney CBD electricity network over five years to 2014. Ausgrid's Sydney CityGrid project involves constructing new substations, replacing and upgrading high-voltage cables and constructing a new tunnel to link into our existing network of CBD cable tunnels. These tunnels connect to form an 8 km ring under Sydney's CBD that interconnects Ausgrid's substations. To provide a GRN P-25 coverage solution into these tunnels for Ausgrid's maintenance staff presented a challenge. Coverage is provided by utilising 'radio over fibre' repeater technology which rebroadcasts the NSW Government Radio Network from two dedicated base station sites located in two of Ausgrid's substations. Radiating cable, fixed to the ceiling of the tunnel, distributes the radio signals to the user in the tunnel, providing a method of communications deep underneath Sydney's CBD, where previously there was no way of communicating with the outside world. Steve Harvey, Engineering Manager, Distributed Coverage and Capacity Solutions (DCCS), CommScopeTRANSCRIPT
COMMS CONNECT 2014 Ausgrid's underground high voltage cables tunnels Providing P25 GRN coverage using radio over fibre repeaters Speaker: Steven Harvey
COMMS CONNECT 2014
CommsConnect 2013
Covering Ausgrid’s HV Cable Tunnels
City South
City West
City East – Under construcDon
• Ausgrid’s Sydney CityGrid project to construct new substaDons, replace and upgrade high voltage cables and construct a new City East tunnel, which links up the exisDng cable tunnels: • City South Tunnel and • City West Tunnel. • These three tunnel secDons connect to form a `7km ring under Sydney’s CBD, interconnecDng Ausgrid’s substaDons.
N
CommsConnect 2013
Challenges communicating underground
• OH&S procedures requires that tunnel workers have a method to contact the outside world if the need arises, whether by landline, radio or mobile phone. Maintenance staff are deployed at checkpoints where landline phones are available, then use simplex radio to contact the working team further within the tunnel.
• The tunnel maintenance team is impacted with the addiDonal labour required to man these checkpoints, leaving less manpower to address the actual maintenance task at hand.
• Since the cable tunnels have expanded from the original South tunnel, the current method of manning checkpoints puts addiDonal pressure on the maintenance team.
• A radio over fibre repeater system can enable coverage into these tunnels and provide a beZer, more efficient way for maintenance staff to communicate with the outside world using the exisDng GRN service.
CommsConnect 2013
Solution: ION-M4 Radio over Fibre Repeater
• Ausgrid are a GRN user, so maintenance staff already have handheld radios.
• A dedicated GRN base-‐staDon uDlises the ION-‐M radio over fibre repeater system, to distribute RF signal over leaky feeder cable run throughout the tunnel.
• This system provides a method of communicaDon to colleagues within any part of the tunnel and above ground to ensure safe and stable communicaDons.
CommsConnect 2013
ION-M4 Radio Over Fibre Repeater (RoF)
• Point to Point ConfiguraDon. Each remote unit is connected to one opDcal fibre. One single fibre supports UL and DL at the same Dme.
• Network Redundancy is achieved by two independent networks interleaved. A single system will meet minimum RSSI target Rx levels.
A
B
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ION-M Master Rack
• System B Equipment Room • ION-‐M RoF Master Rack • GRN Base StaDon • DC RecDfier and BaZery Back-‐Up • Tx Combining (1+3 channels)
CommsConnect 2013
ION-M Master Rack – Block Diagram
Base StaDon, Tx Combining
& Rx mulDcoupling
Single Mode OpDcal Fibre connects master rack OTRX To Remote Unit
Interface cards allow RF Levelling
CommsConnect 2013
Fibre – Connecting the Master Rack and Remotes
1310
1550
1310
1550
COUNTER-DIRECTIONAL
• The Master rack and each of the remote units connect to each other via using single mode opDcal fibre (SMOF) cable. One core per remote
• E2000-‐APC connectors are used (8 degree angled, polished connector)
• The system allows for a maximum of 10dB opDcal loss (0.5dB per 1000m @1550nm) and Auto levelling ensures RF gain remains constant no maZer what the opDcal loss is (within 10dB)
• Wavelength Division MulDplexing enables signals to transmit and receive at the same Dme over a single fibre, at specific opDcal wavelength. 1310nm is used for the downlink (Tx) and 1550nm is used for the uplink (Rx)
CommsConnect 2013
ION-M4 Remote Unit • Passive Cooling
• 180W Power Consumption
• Common PA – *40dBm composite power shared
• Duplexer is 5MHz bandwidth, so frequency planning is required to ensure channels are within the duplexer bandwidth
ION-‐M 4 Remote
Fibre Enclosure
CommsConnect 2013
ION-M4 Remote Unit
CommsConnect 2013
RF Design Parameter Considerations
• Link Budget: Downlink Power per carrier (control Channel) for shared PA.
• The system is designed for a target received signal strength (RSSI) of -95dBm (control channel) worst case for a single system, to meet Delivered Audio Quality DAQ3.4
• Frequency Planning for duplexer bandwidth, and avoiding co-channel and adjacent channel interference between System A and B
• TDI – Time domain interference due to overlapping coverage by simulcast signals. Maximum allowable delay is15 microseconds for P25 Phase 2 for signals of equal signal strength. The difference in fibre lengths to neighbouring remotes must be within 3000m before TDI occurs. Velocity through fibre.
• BRx Uplink Noise figure for multiple Optical Remotes. NF +10 log N, where N = number of remote units
• Uplink Gain Mode: ICP3 or Noise Figure Optimised. Handset TX power and RU Receiver blocking
Downlink - RF Budget Frequency 450MHz
Power Output at MMR4 Remote 26.00 dBm for 8 x 25Khz carriersHybrid Combiner 3.50 dBLDF4-50RN tails 0.15 dB 2connector pairs 0.20 dB 3
Power into Radiax 22.15 dB
Radiax RXL5-1RN-Battenuation at 450MHz is 3.1dB per 100m 0.031 dB/mCoupling Loss (95% confidence) at 2m perpendicular distance from cable 86 dB
Handheld Receiver Noise Figure 10 dB
ENBW - Receivers Equivalent Noise Bandwidth 25000 HzThermal Noise Threshold is KTB + NF -120.02 dBm
Minimum RSSI to Handset (Cf/N)to meet DAQ3.4 is 20dB +/- 5dB above noise -95.02 dBm
Antenna Adj / Body Loss / Statistical Variation -9.00 dB
Design Target for RSSI -86.02 dBm
Min Power at end of Radiax -0.02 dBm
Max Length of Radiax (metres) 715.08 metresfrom split output of Remote
Total distance covered by Remote 1430.15 metres
Total Length of Tunnels 7000.00 metresNumber of remotes 5.00
m
CommsConnect 2013
RF Design - Schematics
• Passive components such as couplers and splitters are used to distribute RF signals to the leaky feeder and discrete antennas in sub stations.
• 50ohm terminations are used to isolate remotes connected by the same leaky feeder cable.
• RF signals from System A are strongest where System B are weakest or vice versa
CommsConnect 2013
RF Design cont.
• Hybrid Couplers are used to mix System A and B into antenna feeds for Sub Station antennas
• Coupler values are selected to distribute equal RF signals to each discrete folded dipole antenna
Fibre
System A
System B
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Leaky Feeder Cable RCT4-WBC-1X-RNA
• Mos.
CommsConnect 2013
Leaky Feeder – Coupling Loss
• Longitudinal InserBon Loss (Pi)
Measure of loss within the coaxial cable
• Coupling Loss Measure of the efficiency
to radiate the signal at a specified distance (D)
Y-A
xis
X-Axis
D Pin
Pout
LI = Pin - Pout
PR
Lc = Pin - [ PR(d) - Li • d ]
CommsConnect 2013
RCT Radiax – Radiating Mode (slotted)
• Mo
Signal
Input
RF Signal is LAUNCHED from the Cable. The signal “leaks” or couples out of the cable through
slots in the outer conductor.
“Radiating Mode” RADIAX® RCT Series
CommsConnect 2013
Types of tunnel – Leaky Feeder Cable Mounting
• Leaky feeder cable should be spaced away from walls and fixtures by 51mm.
• Refer to mechanical specifications in data sheet
• Pre-cast concrete panel. CLIC fasteners, spaced every 1m.
• Shotcrete lined tunnel, used stainless steel catenary wire suspended from cable tray, fastened every 1m using cable tie with plastic spacer to separate RCT4 cable from wire.
CommsConnect 2013
System Commissioning – Master Rack
ION-‐M Master Rack Sojware
Alarms can be interfaced to an NMS via A.I.M.O.S server
sojware
CommsConnect 2013
System Commissioning – RF Tests
Spectrum Analyser used to measure control channel power into antenna, to be verified against link budget calculaDons
All coaxial cables tested for: Cable loss (inserDon loss) Return Loss (RL) for VSWR Distance to Fault (DTF) to verify length
CommsConnect 2013
System Commissioning – RF Tests
Off air measurements with an Anritsu S412E LMR Master (opDons 0521 and 0522) for P25 decode. Control Channel RSSI can be ploZed and presented as a “snail trail” map
Outdoor measurements?
Measurement: RSSI (dBm) Excellent > = -‐70.0 dBm Very Good > = -‐80.0 dBm Good > = -‐90.0 dBm Fair > = -‐100.0 dBm Poor less than -‐100.0 dBm
CommsConnect 2013
Fibre Testing and Commissioning
• Optical Power Meters – quick test, provides Optical loss.
• OTDR – Optical Time Domain Reflectometer.
Launch Lead 1 Launch
Lead 2
Fusion Splice
Connector
CommsConnect 2013
Summary and Benefits of Radio over Fibre Repeater
• CommScope have provided a GRN P-‐25 coverage soluDon into these tunnels for Ausgrid’s maintenance staff using CommScope’s ION-‐M Radio over Fibre repeater which re-‐broadcasts the NSW Government Radio Network from two dedicated Base staDon sites located in two of Ausgrid’s sub staDons. CommScope’s RCT radiaDng cable, fixed to the ceiling of the tunnel, distributes the radio signals to the user in the tunnel, providing a method of communicaDons deep underneath Sydney’s CBD, where previously there was no way of communicaDng with the outside world.
• The base staDon/master rack has been expanded to feed the City East Cable Tunnel, reducing expense of building an enDre new system for the new tunnel.
• A similar soluDon using a dedicated base staDon and ION-‐M system could be used to provide Radio Network coverage into localised underground car parks, Shopping Centres, Road and Rail tunnels.
www.COMMS-‐CONNECT.com.au
Conference materials available at
COMMS CONNECT 2014