| With gradual expansion of the power network scale and bulk nationwide interconnection, power network strengthens the contact among areas, makes full use of the resource but also brings hidden troubles to power network security. Following the blackout on August 14, 2003 in the United States and Canada, more blackouts happened then which shows that the safe operation of the power system has already become a topic of worldwide concern. It is against such a background that a preliminary study is made on the cascading blackouts with fault-chain, and the key problems are discussed in fault-chain use in analyzing cascading failures.It studies the consistency between fault-chain and cascading failure. And the maturity of fault-chain makes it more suit to study blackouts.How to select peak failure and how to obtain one fault-chain are problems when using Fault-chain theory. First, for the former ,according to the practical blackouts, the paper considers that power system's out of stability is more close to the blackouts than busbar failure that usually selected in recent blackout study. Also the paper explains deficiency of selecting busbar and proves rationality of selecting system's out of stability as the peak failure. Secondly, It explains the meaning of structure characteristic, through which the paper distilling the process that shows structure characteristic. As to how to obtain one fault-chain, the paper cites forecasting formula. It makes the formula more practical mainly in the number of broken-down components appearing in aftertime. In original principle for forecasting, the number is four while it is one in this paper, and the reason is given on the choice. Thirdly, the paper actualizes the initialized failure's enumeration according to the influence on the other lines of power system brought by load's transferring.Finally, taking IEEE-39 for example,the paper actualizes the upward theory and brings control methods forward to avoid blackouts.
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