In this article, an improved setting-free loss-of- excitation (LOE) protection is developed for fast and reliable clas- sification of various events. In the proposed scheme, the internal voltage and reactive power of the synchronous generator (SG) have been exploited to fulfill the condition of not needing the threshold amount because they are directly dependent on the rotor field and continuously reduced during the LOE, leading to having a negative polarity of variation. However, due to slow dynamic variation dur- ing the LOE condition, they are multiplied to accelerate and high- light the reduction changes, giving rise to increasing the detection speed. Meanwhile, owing to the considerable difference between the value of internal voltage and reactive power and to highlight the effect of multiplication function, an adaptive gain on the basis of steady-state parameters of SG is suggested. Furthermore, given that the negative polarity of the multiplied parameters can be affected during the hybrid events, the limited integral function is implemented to eliminate the happened swings, resulting in keeping the negative polarity and thus clustering the hybrid events reliably. The performed simulations on the IEEE 9-bus and 39-bus test systems prove that the provided setting-free protection can detect all types of the events reliably and quickly than other schemes.
