Ocean Observatories Initiative Cabled Array Observatory Extension Cables/Connectors Mike Harrington mikeh@apl.washington.edu
Infrastructure Cable Laying Problem: Get to the interesting stuff. Laying interconnection (instrument and between nodes) cables with lengths between 150m and 4+ km. (Cables up to 200m have been deployed from tool basket/undervators) Solution: Key Enabling Technology - a cable laying system (ROCLS) has been used to successfully lay 80+ km of interconnect cable on OOI/CA. Description: the ROCLS system is composed of a drum inside a frame that is hung beneath the ROV. However, difficult to monitor and control cable tension. The system is subject to ship/rov motions, so restricted in sea state.
Axial Caldera Layout
Extension Cable Deployments 18 Electrical Optical Cables > 1Km long - 64km Total 42 Electrical Extension Cables with Wet Mate Connectors < 1km Lengths to 4800m installed by ROV Lengths to 17km installed by cable ship One failure during installation Hockle
Lessons Learned Plan Plan Plan Detailed surveys/route plan 2 years in advance Lots of meetings with vendors (ROPOS/ODI) Detailed loading of the spools Run the route before the lay Visual inspection of wet mate connectors. Test Test Test
ROV Cable Deployment
One Event.. X = 0 Z = 0 Secondary Cable UHMWPE 12-strand core with braided jacket 1.9 cm" OD x 3051 m EM Cable 4x #24 AWG and 2x #18 AWG conductors, Vectran strain member, urethane jackets 1.27 cm OD x 285 m 46" Float 474k g buoyancy Secondary Leg Releases Science Pod 182 kg buoyancy Z = -200 m VM Platform 2120 kg buoyancy EOM Cable 6x #10 AWG conductors, 6x SM fibers, Kevlar strain member, HDPE jacket 2.54 cm OD x 3085 m Cable Floats 94 syntactic floats attached to EOM cable 9 kg buoyancy/each Secondary Anchor 5455 kg Air / 4745 kg SW X = -1528 m EOM Anchor 5455 kg Air / 4745 kg SW EOM Leg Releases X = 1528 m Z = -2905 m
One Event Installed Mooring Turned it on Overcurrent Event Doh! How to debug with limited time/hardware? Output Port? Flooded Package? Bad Connector? Left to do other work for a couple of days.
One Event James Tilley Could the 200 Meter extension 2 conductor cable be wired backward? Seemed very unlikely but we had spare on board. Sure enough simple fix but could have been very ugly if we went down some other diag paths.
Control System
Problem: What is the right balance for redundancy backup systems versus simple? (why to planes have 2 engines now and not 4?) It is very expensive to service the infrastructure when there is a failure in the system so the tendency is to add more redundant and backup systems but this makes the system more complex, harder to fully test, more difficult to configure correctly, harder to operate so it is not clear that the final system is always more reliable or not. Solution: Focus on simple redundant systems where possible that do not rely on overly complex control circuits and are simple to test without adding new failure points.
Example: Overcurrent Protection We added many different points for overcurrent detect and port shut off in the secondary nodes but the logic and characteristics for each one are different and can make it difficult to test. In the end the DC/DC converters themselves have protection circuitry that probably was good enough to prevent hardware damage. Care must be taken to fully characterize power needs of instruments in all modes- many have large inrush needs but small overall power requirements because they are typically used with batteries. may need to add inline resistors or output caps. Fully testing all features in all cases can be difficult because they all have different set points/ response times etc. May end up with latent issues that don t show up until final integration testing (or worse after deployment)
Example: Loopback Testing We added a loopback configuration on the instrument ports to test the port when the relays were open to the outside world. Caused an issue in the Network Switch for Ethernet Instruments when the signals were looped back. Issue did not show up until after deployments because system used slightly differently than during testing.