Depth of Burial of Subsea Power Cables
Submarine power cables operate in a dynamic seabed environment where cables can become
- exposed and prone to mechanical damage or
- heavily buried, leading to insufficient heat dissipation.
To reduce the risk of cable damage and to be conform with legal requirements, cable operators today are obliged to verify the burial depth of submarine cables in regular intervals, e.g. by carrying out costly magnetometer measurements or submarine Remotely Operated Vehicle (ROV) inspections. However, natural events such as sediment mobility or seismic activity can change the burial depth within a short period of time, making continuous burial depth monitoring the most reliable approach to risk mitigation. Burial depth monitoring enables maintenance to be planned and performed based on actual needs instead of pure periodical maintenance. Furthermore, burial depth monitoring helps to optimize operations and maintenance budgets, can reduce insurance premiums and extend cable life.
Depth of Burial State Monitoring (DoBS)
AP Sensing’s DoBS is a reliable and very accurate solution to enable predictive maintenance and regular monitoring of changes in the burial depth of a submarine power cable. It indicates whether a cable section is buried, has low coverage or is exposed. The trace of the burial depth state is a function of the observed dynamic temperature variations depending on the characteristics of the marine environment as well as the correlation with the cable load. Our unique solution neither requires the precise and spatially resolved knowledge of additional ambient conditions and soil parameters, nor any computational model. It also ensures that minor deviations in the input data do not lead to dramatic inaccuracies in the calculation of the burial depth that are observed with other solutions. For offshore power cables, AP Sensing’s DoBS solution only requires the installation of a DTS unit at an onshore or offshore location to enable an accurate determination of the burial depth state.
Quantitative Depth of Burial State Monitoring (QDoBS)
Based on the Depth of Burial State, AP Sensing’s qDoBS module offers a more detailed insight on submarine cables by providing the burial depth trace with centimeter-level accuracy. AP Sensing’s innovative algorithm offers fast calculation times, enabling multiple rating runs per day. This ensures the timely availability of accurate information whenever required. Quantitative DoBS is characterized by its ability to provide accurate results with centimeter-level accuracy regardless of the prevailing environmental conditions.
DoBS Features
- DoBS monitoring along the entire power cable with configurable pre-alarms and alarms
- Reliable detection of changes in the burial depth
- Accurate location of washed-out cable sections and free spans
- Accurate Depth of Burial trace with centimeter-level accuracy
- Thresholds are configurable for alarming and pre-alarming
Benefits of DoBS
- In contrast to full modelling approaches, AP Sensing’s unique solution works without the need to know the exact environmental conditions as input parameters (e.g., water temperature, soil type, current effects) and therefore allows more reliable results and a faster commissioning.
- Unlike model-based solutions that calculate incorrect DoB values even with very small deviations in environmental parameters, AP Sensing's DoBS solution computes stabile results under such conditions.
- Continuous monitoring of burial depth for the entire length of the subsea cable, based on a robust calculation engine delivering rapid results and enabling multiple updates per day.
Output Data
- DoBS – Distributed computation and visualization of the burial state
- qDoBS – Trace of burial depth in centimeter-level accuracy along the power cable line
- Pre-alarms, alarms, faults and system status
- Via industry protocols, such as Modbus TCP, IEC 60870-5-104, IEC 61850 and others
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