power system structure

lecture 1
A power system will have been planned and constructed, and be operated, to maintain reasonable redundancy as an essential characteristic. Thus the system may continue to operate successfully in most cases even if a large part of it is suddenly cut off. On the contrary, the rare failure of one tiny part, for example a protective relay (or just one of its components), may trigger a kind of domino effect leading to a black-out. Disruption of large part of power system network by ‘domino-effect’ means big power failure leaded by abrupt segmentation of power system network, which may be probably caused by cascade trips of generators caused by total imbalance of power generation and consumption which leads to ‘abnormal power frequency exceeding over or under frequency capability limits (OF/UF) of individual generators’, ‘cascade trips of generators caused by power stability limits, Q-V stability limits or by any other operational capability limits’, ‘cascade trips of trunk-lines/stations equipment caused by abnormal current flow exceeding individual current capacity limits (OC), or by over or under voltage limits (OV/UV)’, ‘ succeeding cascade trips after fault tripping failure due to a breaker set back or caused by mal-operation of a protective relay’ and so on, and may be perhaps
Caused as of ‘these composite phenomena’. These natures of power systems are the outcome that all the equipment and parts of the power system, regardless of their size, are closely linked and coordinated. The opposites of toughness with well redundancy and delicacy are the essential nature of power system.