The exploitation of asymmetry in electric power transmission networks

For more than a century electric networks have evolved on the basis of a three phase symmetrical equilibrium system. If the current and voltage distortion is seen as inevitable in the daily exploitation, the philosophy basically remains the same: the three phases are considered as a single symmetric ensemble. In high, very high and ultra high voltage (HV, VHV, and UHV) the appearance of a contingency automatically carries out cutting of the three phase line into single, two or three phases all at once. But, having the same reaction vis-a-vis the whole, the case of faults is not optimal. In this article, we effect a revue of methods and criteria actually used in the assertion of security limits, we set out the concepts and basis of constraints binding the exploitation of a three phase line as three independent lines and discuss a realisable solution for the exploitation of a HV or VHV transmission network managing asymmetry and security.