The 150kV transmission system was constructed by CNI22 under a contract with the Timor-Leste Government. The construction began in 2009 and was completed in 2014. A 5-year contract for the operation and maintenance (O&M) of the transmission system between the then Ministry of Public Works, Transport and Communication (MOPTC) and CNI22 was signed in 2016. This O&M contract ends in September 2021 and EdTL is in the process of tendering the O&M contract for a subsequent period. The transmission system consists of 603.42 circuit kms, with mostly single circuit lines, except for the Dili-Hera-Manatuto section, which is double circuit (50.8 kms). In general, the transmission network has surplus capacity and will not require expansion for quite some time. However, some of the substations will require additional spare transformers, as a backup when the service transformer requires repairs or upgrading. EdTL is taking measures to address this shortcoming in Dili’s Camea 150kV/20kV substation and in the Liquiçá 150kV/0kV substation. During the term of this BDP, EdTL will begin to train its transmission staffing the O&M of the 150kV transmission line network and associated substations, and towards the end of the BDP they will be able to take over the O&M operations.

EdTL’s transmission network is exposed to extreme weather conditions (tropical cyclones, flooding, and salt spray), primarily from strong winds that often cause indirect damage due to encroaching vegetation. The devastating storm and subsequent flooding, in April 2021, has highlighted this exposure. A significant amount of vegetation management is needed as the transmission network is vulnerable to falling or wind-blown tree limbs. The grid does not feature any sub-transmission circuits or trunk feeders as one would see in larger and more densely populated areas internationally. This makes Timor-Leste’s grid largely radial in nature with little ability to interconnect or mesh the networks to provide multiple transmission routes to key customers or core areas of service.