Investigation On Fault Current Limiter

Fault current limiting relates to many important issues encountered in power systems such as limitation of circuit breakers in their current interrupting capability, fault impact on the safety operation of power equipment and power networks as well as on the power quality. Significant promotion of power systems could be achieved with the application of the fault current limiter (FCL), and therefore it has been widely investigated around the world.Fundamental investigations have been performed in this thesis on the fault current limiting schemes.The first investigation was made experimentally and theoretically on the current-transferring processes from a vacuum arc to a current limiting resistor. It was shown that, due to the small vacuum arc voltage, the current-transferring is difficult to realize in such a speed that the first peak of the fault current can not be limited. For the rapid current-transferring, a double current-transferring scheme was proposed in which a fast vacuum switch, a GTO based switch and a current limiting resistor are connected in parallel. The fault current limiting involves two current-transferring processes, the first one is from the fast vacuum switch to the GTO, and the second is from the GTO to the current limiting resistor. By using the fast switch, the power loss of the FCL in normal operation condition could be avoided, and by using the GTO, the rapid current-transferring could be realized with a smaller difficulty. The simulation test has showed the feasibility of this scheme, and the computer calculations showed that the arc voltage and the stray inductance and resistance of the current-transferring circuit make sensitive influence on the current transferring speed. Investigation was also made on the fault current limiting scheme of series resonance, the most practical one for power transmission system. The behavior of the series resonance type FCL with different parameter coordination has been investigated for their optimum selection.The work of the thesis expands the knowledge on the fault current limitation, especially on the practical demands and the difficulties. This makes a foundation for the further investigation in this area.