to replace the thyristor valves at the Apollo station. The outdoor mounting concept was retained, but each of the new housings contains a complete six-pulse bridge instead of only two valves, and the replacement thyristor valves are of a more conventional air insulated, water-cooled design using 125mm, 8.5 kV thyristors. 36 such thyristors are connected in series in each valve, without parallel connection, and the new valves are capable of a subsequent upgrade to 600 kV, 3300 A. At the same time, the AC filters were replaced. Sites See also High-voltage direct current HVDC converter HVDC converter station Cahora Bassa Cahora Bassa Dam Energy in Mozambique Electricity sector in South Africa References Further reading Eustace F. Raynham, Apollo – Cahora Bassa: enigma and diversions, EE Publishers, , External links Bibliography of references on the social and economic impact of the project Location of Apollo CIGRÉ SC B4 Compendium of HVDC schemes, 2005 CIGRÉ SC B4 Compendium of HVDC schemes, 2005 Siemens HVDC Reference List ABB HVDC Reference Projects – Cahora Bassa Cahora Bassa HVDC transmission link – Guide: Apollo station; ABB publication No. POW-0054. Cahora Bassa HVDC transmission link – Apollo station refurbishment project; ABB publication No. POW-0055. HVDC transmission lines Electric power infrastructure in Mozambique Electric power infrastructure in South Africa Energy infrastructure completed in 1979 Mozambique–South Africa relations 1979 establishments in Mozambique 1979 establishments in South Africa