Loss of excitation (LOE) event threatens both the generator and power system stability. Several methods have been proposed for LOE detection, most of which are based on the impedance trajectory. Such approaches may not be able to distinguish between LOE and stable generator swing (SGS). Thus, allocating an operation time delay is usually used to overcome the LOE relay misoperation due to SGS. This paper presents a new approach for the LOE relay. The proposed strategy exploits a combined scheme based on derivative of both the terminal voltage and the output reactive power of the generator. Comprehensive simulation studies are accomplished for various generator conditions and system disturbances to determine the relay setting and to evaluate its performance. The performed studies demonstrate that the proposed strategy enhances both security and operation time of the LOE relay, as compared with some existing methods.

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Oxidative damage of sperm by means of reactive oxygen species generated by the cellular components of semen is one of the main reason of declined motility and fertility of sperm during the freeze-thawing process. This study was conducted to determine the influence of vitamin C and vitamin E on rooster post-thawed sperm motility, viability and malondialdehyde (MDA) level. Semen samples from 10 sexually-mature Ross 308 breeder roosters were collected and pooled, divided into nine equal parts and diluted with modified Beltsville extender containing with no antioxidants (control), or containing 100 (C100), 200 (C200), 400 (C400), 800 (C800) µg/mL vitamin C, and 2 (E2), 5 (E5), 10 (E10) and 15 (E15) µg/mL vitamin E. After thawing, total and progressive sperm motility, sperm viability and semen MDA level were assessed. The results shown that C200 and E5 extenders resulted in higher total motility (p < 0.05) compared to other extenders, with exception of E10 extender. Progressive motility was higher in E5 extender (p < 0.05) compared to other extenders, with exception of C200 and E10 extenders. Also, C200 and E5 extenders resulted in higher viability of post-thawed spermatozoa (p < 0.05) compared to other extenders. Finally, the results showed that MDA level was lower in C100 and C200 extenders compared to other extenders (p < 0.05), with exception of E5 extender. In conclusion, the results of the present study demonstrate that C200 and E5 can improve the function of post-thawed rooster spermatozoa.

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