Learnings

Outcomes

The main outcomes of the project at this stage include the following:

• A comprehensive review of cable solutions for both AC and DC applications at ultra-high voltage levels has been carried out. It is found out that some of the limitations are associated with the technologies themselves whilst others may be related to availability in the market.
• A review of HVDC technologies and their applications internationally including multi-vendor HVDC standards, as well as low frequency transmission technology.
• The initial feasibility studies of HVDC tower design with a focus of optimising dimensions and initial lab testing for audible noises was carried out. The initial studies suggested that the  potential design solutions might be feasible to restrict the dimension of the 550kV & 800kV UHV HVDC OHL tower to be within 50-55m wide and high which is similar to the dimension of some existing 400kV OHL tower in the network. More detailed studies are due to be completed.
• Initial lab testing on audible noises for Aluminium Alloy Conductor (AAAC) samples under both dry and continuous spray conditions with both positive and negative DC voltages under various surface electric fields has been carried out.  It is noticed that for surface electric fields less than 24kV/cm, positive DC produced more A-weighted decibels, while negative DC produced more at higher electric fields. 

Lessons Learnt

No lessons learnt to report at this early stage of the project. 

Dissemination 
Although the project is still at a relatively early stage, the initial work carried out and key findings have been shared with relevant stakeholders from NGET, SPEN and SSEN via two stakeholder workshops (held on 25th October 2023 and 28th February 2024).