Why Submarine Cables?

Transcription

1 Nalaka Siriwardena Engineer/SEA-ME-WE 4 Project Engineer/Projects Why Submarine Cables? Cost effective on large routes High bandwidth due to the evolution of technology such as DWDM High Quality with low attenuation. No interference High security Efficient Network Management High Reliability 1

2 Contents Pre-installation Desk top Study SLD Survey (Off shore, BAS, Inshore) Cable Laying Technology SEA-ME-WE 4 Experience Pre-Instillation... Desk Top Study (DTS) This is the first stage of any cable route survey operation. DTS draws on published information of interest to the cable engineers planning the route and selecting suitable cable types. DTS provides information on climate, weather patterns, bathymetry, temperatures, shipping, fishing, EEZ, Military Reserved Areas, other cables (both in use and out of use) etc. along the proposed route. Selecting a LP, Duct Route, OGB Site, Building & Access Facilities Deciding a Preliminary Cable route 2

3 Pre-Instillation Desk Top Study (DTS) Items Involved in DTS Collection of Data & Information Analysis and Assessment of Data and Information Collected Mapping of Data and Information Study of Prohibited or Dangerous Areas for Cable Installation Selection of Alternative Routes and LD A comparison and assessment of routes and LP Priority Ranking of Alternative routes and LP Conformation of Suitability of each LP Decision of the Preliminary Route Pre-Instillation Desk Top Study (DTS) Items Involved in DTS Collection of Data & Information Information on Natural Environment Marine Charts, Seabed topographic Map, Sea Bed Geographical Structure map, Topographic Map of Coastal sea Area, Map of Land conditions in coastal Sea Area Information on Fishing Industry Fishermen's Associations, Maps of Fishing Rights Areas, Under Water Fish Tanks, Positions of Fixed Nets, Fishing equipments & methods External Information mainly From Government Department Plan of Harbour, Construction plans for Coast Conservation, Areas of anchoring, Anchor Prohibited Areas, Coastal Preservation Areas, City/Airport Development Palns, Permits/Approvals 3

4 Pre-Instillation Desk Top Study (DTS) Outcome of DTS Route Positioning List (RPL) Route Chart Straight Line Diagram (SLD) Shore End Protection Methods Land Cable Route Any Other Specific Requirement Pre-Instillation Desk Top Study (DTS) Part of Our DTS 4

5 Pre-Instillation Desk Top Study (DTS) Our SLD during DTS Segment 1 of SEA-ME-WE 4 Cable System Colombo Bangladesh Thailand Malaysia Mumbai India Chennai India Singapore Segment 1b Segment 1a Pre-Instillation Desk Top Study (DTS) Our SLD during DTS Colombo LP DA/SA SA/LWA LWA/LWP km 4.277km 8.781km 5.218km Colombo BU DA SA LWA LWP Cum. Length km km km km Slack 1.00% 2.00% 2.00% 3.00% Depth 0m 250m 700m 1500m 1900m Note: These figures may change after Survey 5

6 Pre-Instillation Desk Top Study (DTS) OurSLD during DTS Selecting a Landing Point Location of Bach Man-hole Decide on the Location for BMH Investigate available BMH Or Construction of a new BMH Duct Routes New duct Route or Existing Ducts Routes Study on Man-holes Requirement of sub-ducts It is always advisable to use existing duct routes and existing BMH (if available). Otherwise construction of a new BMH and a duct route will cost more. Selecting a Landing Point Easy Access to the Proposed Cable Station Proposed LP 6

7 Pre-Instillation... Survey To obtain necessary information for selecting a Landing Point and a Cable Route Collect oceanic information for Designing Cable Types Planning Cable Laying Burial Operation Shore End Protecting methodology Landing Site Surveys Pre-Instillation... Survey Scope of Work Described in evolution SC of rocks SEA-ME-WE and land forms 4 general bathymetry; morphology and nature of the seabed; sea bottom and sub-bottom characteristics (such as sand waves, coral reef); sea bottom temperature and seasonal variations; surface, sub-surface and seabed current influences; seismic and volcanic activity; turbidity currents; climatologic conditions; territorial waters and exclusive economic zones; in-use, abandoned and planned dumping sites; in-service, out-of-service and planned pipelines; The branch of geology that studies the characteristics and configuration and Muddiness created by stirring up sediment or having foreign particles suspended in-service, out-of-service and planned cables (telecommunications and power); cable fault history; fishing activities, dredging, submarine resource development activities; shipping activities, navigation restrictions, anchoring and prohibited anchoring areas; wrecks and other hazards; route position list, straight line diagram and burial requirements; installation procedures. 7

8 Pre-Instillation... Survey International Waters, EEC, Territorial Waters Source: Internet Pre-Instillation Survey Marine Survey Landfall/ Inshore Survey Deep Water Survey Offshore shallow water Survey BM 1000m SEA 15-20m 3m Diver Swim Survey 8

9 Pre-Instillation... Survey Marine Survey Equipments Purpose Equipment the shape of an area of land and the things that are on it, including its hills, valleys etc Measuring the depths of the oceans Depth of Water Topography Surface of Sea Bottom Echo Sounder, Multi Narrow Beam Sounder Bathymetry Mapping System Side Scan SONAR, Camera Sub Bottom Profile Sonoprobe, SG SONAR, Airgun, Sparker Materials of Sea Bottom Water Temperature Grab Sampler, Dredge, Poston Core, Sampler, Vibro Corer XBT, Electric Water thermometer Ocean and Tidal Current Anderaa Current Meter Burial Assessment Anchor Towing, Plow Towing, Cone Penetration Testing Pre-Instillation... Survey Submarine Topography Materials of sea bed/burial Assessment Mud Sand Rock Thickness of sediment Positioning (GPS) Implementation of Route Survey 9

10 Pre-Instillation... Survey Part of bathymetry Chart of SEA-ME- WE 4 Pre-Instillation...Survey Conclusions and recommendations of Survey Discussion of results Recommended cable types Recommended cable slack for installation Recommended Route Position Lists Recommended Straight Line Diagrams Recommended cable protection measures Marine installation procedures Any information considered to be of value to cable route engineering, installation and maintenance 10

11 Cable Installation Important Follow the finalized RPL Confirm the laying on actual sea bed without suspension and residual tension Maintain Proper speed of Ship and Cable lay speed Positioning of submerged Plants properly Follow the International Regulations/Laws and Safety Features Cable Installation Cable Slack A Cable Holding Position d B θ l 1 l 2 l = l 1 -l 2 Zero Tension s = l d d 11

12 Cable Installation Cable Configuration during Laying 1 V 2 s d 2 (.sinθ ). ρ θ W θ V s When the force equilibrium, 1 W.cos = C. Vs.sinθ 2 ( ) 2 d ρ θ. W: weight per unit length θ: Cable Incident Angle V s Speed of Cable Ship d: Diameter of Cable ρ: Density of sea water Cable Installation Ship Velocity Vs Cable Angle Source: Submarine Cable Network Systems 12

13 Cable Installation Cable Configuration during Laying Cable Holding Start of Laying of the Cable from Cable Holding End of Cable Laying Cable Lay on Slope Transient Slack when Cable Type/Ship Speed is changed Real Time Slack Control Cable Installation Cable Laying Operation From offshore towards the cable landing station A, one end of the cable is paid out by the ship and "landed". During this phase, the cable is suspended by balloon buoys to prevent possible damage to the cable. Later the buoys are detached, allowing the cable to sink to the ocean floor. Drawings taken from web 13

14 Cable Installation Cable Laying Operation The ship lays cable as it navigates towards the opposite station or a designated point in mid-ocean. Cable Installation Cable Laying Operation At the designated point, the Ship connects its cable With the terminal of a cable previously laid from station B. 14

15 Cable Installation Cable Laying Operation Upon completion of the final connection; the cable is allowed to sink to the ocean floor. Protection Technology Causes for Submarine Cable Faults Natural Phenomenon Earthquakes abrasion due to currents/wave action Fish bite Human Activities Fishing Activities Ship Anchoring 15

16 Protection Technology Strengthening of Cable Adding armoring High quality materials Burying the Cable Simultaneous burial with Cable Laying Operations (Using Plough) Retro-burial (Using ROV, Seabed Tractors) Protection Technology Types of Cable Burial Systems Cable Plough Burial of the cable into the seabed for enhanced cable protection using a plough (usually towed from the installation vessel as the cable is deployed from the vessel). Depth of Water: Up to 1500m, Burial Depth: 3m The cable is guided into the bottom of a narrow trench cut into the seabed by the plough depressor 16

17 Cable Plough Protection Technology Types of Cable Burial Systems ROV Remotely Operated Vessel A submersible unmanned vehicle used to inspect, debury, bury or re-bury cables. They can also be used to carry out surveys and inspection of the cable on the seabed. ROV s are usually fitted with cameras, cable tracking equipment and for burial operations can be fitted with a jetting or trenching tool package. 17

18 ROV (Remotely Operated Vessel) Protection Technology Types of Cable Burial Systems Tractor Injector Cable Trencher 18

19 More Topics to Discuss Surveying Vessels Cable Ships Submarine Cable Repairs Multi-Cable Landing Pipe Landing Method (HDD) Test Equipments During Land Fall/Inshore Survey at Galle Face Unforgettable experience during the Survey. It was on 26 th December 2004, we continued our survey. It was the last day of the survey at the shore-end. Sea water level rose up to the Galle Face Ground Level within a few seconds A big surprise Suddenly the water receded exposing the sea-bed which looked like a grassless ground A very rare sight Our Officers were lucky enough to capture the moment electronically in their cameras Later we understood that it was a Tsunami, striking our coasts 19

20 The moment just before Tsunami waves hit during the Survey at Galle Face, Colombo Memories of SEA-ME-WE 4 Cable Project Tsunami waters disturbing the Survey Memories of SEA-ME-WE 4 Cable Project 20

21 Wonders in the sea bed after Tsunami SEA-ME-WE 2 Cable in the sea bed exposed Memories of SEA-ME-WE 4 Cable Project Cable laying During SEA-ME-WE 4 21

22 During SEA-ME-WE 4 During SEA-ME-WE 4 22

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