TX Completes Work on Advanced Array Optimiser
As part of the EU-funded FLOTANT project, TX has developed advanced software for designing the cables that collect power from individual offshore wind turbines: so-called “array cables”.
TX identified that there were few products available for the optimisation of array cables when they are configured to form loops, an approach used on a third of UK offshore wind farms and 80% of German offshore wind farms. It is also an approach that is likely to be particularly useful on future floating wind farms.
The software developed by TX has a number of advanced features:
- It considers not only capital costs, but also the cost of losses and the cost of curtailing generation following a fault.
- Cable crossing are allowed, with the extra cost of the crossing being included in the optimisation. This can give cheaper layouts in some situations.
- The cable cross sections are optimised, with the optimiser finding the best 2 (or best 3) sizes from the full range of possible sizes and also deciding which size of cable should be used for each connection in the array.
- For large wind farms, the software will automatically break the wind farm into areas connected to separate offshore substations.
- The optimum location can be found for the offshore substation (or multiple substations where the wind farm is large).
Tests of the software against actual wind farm designs have shown cost reductions on the array cables of up to 7%. On all tested projects – even projects still under construction – we found that TX’s software gave savings of several million pounds.
For more information see our report, or contact TX on +44 7767 298 983.
Converter Dominated Grids: Recent Webinar
As more DC-to-AC converters (e.g. wind, solar, HVDC transmission and battery energy storage) are connected to the grid, and as traditional synchronous machines are displaced from the grid, new voltage stability challenges are emerging.
Along with two partner companies (HVDC Technologies Ltd and Power Technologies Ltd) TX has been working for National Grid Electricity System Operator, undertaking simulations of the future British grid system in order to learn more about these emergent challenges.
The level of detail involved in these simulations is unprecedented: the simulations have a time resolution of just 50 micro-seconds in order to fully capture the behaviour of power electronics and converter control systems, a significant part of the British grid has been modelled in detail, and all generators throughout the grid are modelled as either synchronous machines or as DC-to-AC converters (i.e. no ideal sources).
The results of this work were presented at a recent webinar [Download slides from Webinar]. Work on this project is continuing.
TX Completes Major Submarine Cable Research Project
Transmission Excellence (TX) has recently completed a major 2-year study of offshore cable ratings for the Offshore Wind Accelerator, a research programme administered by the Carbon Trust on behalf of a consortium of offshore wind developers.
This study examined the behaviour of offshore cables in environments that can act as “bottlenecks” that restrict their power-carrying capacity. These environments included J-tubes, cable protection systems, offshore burial at greater than usual depth, and drilled landfalls. For all of these use cases simple formulae describing the thermal behaviour of the cable were developed. For J-tubes and cable protection systems these formulae were verified using full scale tests with actual wind farm cable. For landfalls the formulae were checked against measured temperature patterns on in-service cables.
Using these formulae it was then possible to build a model that simulated the temperatures inside a cable over a period of decades, using multi-decade hourly weather data from the MERRA database (operated by the American space agency NASA) and seabed temperature data from the EU’s Copernicus database. This in turn allowed us to show how wind farm developers can compute the economically optimum size of wind farm that can be accommodated on any export cable, making use of the fact that the wind does not blow continuously.
Our results showed that the economically optimum design involves a wind farm which is substantially larger than the continuous capacity of the cable that connects it to shore. The potential saving from using the optimum design, relative to a wind farm that is limited to the continuous capacity of its export cable, is up to £40m per GW of offshore wind.
A further part of the project made recommendations for how cable temperatures should be monitored in order avoid the risk of damaging cables that are operated well above their continuous capacity.
The study was undertaken by TX in conjunction with Southampton University, who carried out the laboratory tests using their facilities, and who contributed their extensive knowledge of cable thermal modelling. The results are summarised in a joint paper which has been presented at the 2018 IET Renewable Power Generation conference.
TX Moves to New Offices
Transmission Excellence (TX) has moved to new offices in Kenilworth’s historic High Street. The new larger offices will help to accommodate the growth of the business, as well as meeting the company’s objective of providing staff with a beautiful working environment.
TX Delivers Report into Improving Export Cable Reliability
As revealed in a previous report by TX (“Export Cable Reliability: Description of Concerns”) the rate of failures occurring on the high voltage submarine export cables which serve Britain’s offshore wind farms is higher than expected, and this is due to problems with the optical fibres included within these power cables.
Sean Kelly, the director of TX, is leading an industry group which is seeking to understand these failures and to improve the design and reliability of future cables.
In parallel with this, TX has written a further report (“Export Cable Reliability: Alternatives to Interstitial FIMT Optical Fibres”) which explores more radical options – new types of optical fibre, moving the optical fibre out of the power cable, or even removing the optical fibre altogether.
The report can be downloaded using the link below.