A number of facts about quadratic load ow problems y = f(x) = 0, x 2 R n x , y 2 R n y is proved. The main results are the following 1]. If any point x belongs to a straight line connecting a pair of distinct solutions in the state space R n x , the Newton-Raphson iterative process goes along this line. If a loading process y() reaches a singular point of the problem, the corresponding trajecto...