The method of symmetrical components provides a practical technology for understanding and analyzing the operation of a system during power unbalanced conditions, such as those caused by faults between phases and ground, open phases, unbalanced impedances, and so on. In addition, many protective relays operate from symmetrical component quantities. Thus, a good understanding of this subject is of great value and another very important tool in protection.
In a sense, symmetrical components can be called the language of the relay engineer or technician. Its value is both in thinking and visualizing unbalances, and it is a means of detailed analysis of them from the system ...