 Complete the following phrase:  On March 15, 1979, a 1920 MW thyristor based direct current connection between Cabora Bassa and Johannesburg 1,410 km was energized. The conversion equipment was built in 1974 by Allgemeine Elektricitäts-Gesellschaft AG AEG, and Brown, Boveri  Cie BBC and Siemens were partners in the project. Service interruptions of several years were a result of a 