CONTROL AND PROTECTION SCHEMES UNDER THE FAULT CONDITION IN MULTITERMINAL HVDC POWER SYSTEM.

Selective dc line fault protection in multiterminal hvdc power systems is discussed. The advantages and disadvantages of dc power transmission are examined and it is pointed out that multiterminal hvdc transmission will be one of the promissing systems for the economical management of enlarged power networks in the near future. The basic performance of a dc converted is described and possible configurations of point-to-point and multiterminal dc transmission systems are shown. The influences of converter control modes and ac voltage variation on an inverter operating in a parallel linked multiterminal hvdc system are discussed. Selective protection by means of a high-speed isolater with the help of converter control is proposed and demonstrated experimentally. Transient overvoltages induced in multiterminal dc systems by the action of dc circuit breakers are discussed. Finally, the possibility of selective protection by using a dc load breaker having a medium interrupting capacity with the assistance of converter control is examined.