of 2.4 kV each and only required 192 in series per valve – still a large number by modern standards – with two in parallel. As a result, each converter station contained a total of 22,656 thyristors. Other equipment The thyristors also had poor transient overcurrent capability, so another unusual feature of the scheme was the existence of overcurrent diverters between the valves and transformers, although these were later decommissioned at the Apollo station. AC filters tuned to the 5th, 7th, 11th and 13th harmonics of the 50 Hz power supply are installed at each station, approximately 195 MVAr at Apollo and 210 MVAr at Songo. There are two PLC repeater stations: one at Gamaboi in South Africa and one at Catope in Mozambique. Repairing the war damage After the civil war ended in 1992, one of the many effects of the decade of strife was the damage to the HVDC transmission lines. Nearly all of the 4200 transmission line towers located on the of line in Mozambique needed to be replaced or refurbished. This work was started in 1995 and took until late 1997 to complete. The system was restored to full power transmission capacity by 1998. Subsequently, Eskom has commenced electricity supply to Mozambique at 400 kV, under terms similar to the original wheeling agreement, from the Arnot Power Station in Mpumalanga, via Swaziland. The principal purpose of this infrastructure is to provide bulk electricity supplies to the Mozal Aluminium Smelter operated by BHP. The Memorandum of Understanding, signed on 2 November 2007, means that Mozambique will by the end of 2007 be in charge of a project located on its soil but on which it had no control for the past 30 years due to contractual obligations with Portugal. The new arrangement gives Mozambique 85 percent of the Cahora Bassa Hydroelectric (HCB) project while Portugal will retain only 15 percent. The project has a capacity to produce 2,000 megawatts of electricity and is one of the main suppliers of power to the Southern African Power Pool. Mozambique will, however, need to pay US$950 million to the Portuguese government as compensation for the post civil-war reconstruction and maintenance of the dam. The civil war resulted in serious damage to the transmission infrastructure, forcing the Portuguese government to pay about US$2.5 billion out of pocket to repair it. Apollo station upgrade In 2006 a contract was awarded to ABB