A Novel Generator Protection Algorithm Based on Instantaneous Power

There are many shortcomings in the generator main protections currently. For example, the differential protection is affected by current transformer saturation easily. The zero-sequence differential protection is usually affected by the stator eccentricity. So it needs better protection algorithms implement generator protection functions. Researches have shown that the instantaneous power of generator included the imbalance and balance power. The imbalance power is a direct component, which represented all the power from the source to the load. The balance power is the fluctuating power caused by the asymmetry of circuit between the source and the load. In this paper, by the instantaneous power transformation in two-phase coordinates, when an asymmetry fault takes place in generator, the imbalance power arises greatly while the balance power decreases in the generator instantaneous power output. The physical explanations of the phenomenon are given out. A new definition about instantaneous power asymmetry degree is defined. Its value is the ratio of the imbalance power to the balance power. Based on it, a novel generator protection algorithm is presented to realize the generator stator protection functions.