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박지경(Ji-Kyung Park),김광현(Kwnag-Hyun Kim),김철환(Chul-Hwan Kim),유영식(Young-Sik Lyu),양정재(Jeong-Jae Yang) 대한전기학회 2017 전기학회논문지 Vol.66 No.8
After North American wide area black out on August 14, 2003, various studies have been conducted to find out the reason of the disaster. One of main reasons was misoperation of generator protection system. Since then, protective coordination between generator protection system and excitation system controls has been hot issue among electrical engineers. Among various generator protection relays, in this paper, we focused on generator overvoltage and overexcitation relay, which protect the over-flux condition of the generator. Thus, at first, we modeled the generator overvoltage, overexcitation relay and detailed power system including excitation system, governor and etc., based on actual field data. And then, we reviewed the protective coordination of generator overvoltage and overexcitation relay using electromagnetic transient program. In addition, we discussed the protective coordination method for redundant protection relays in both automatic voltage regulator and generator side.
터빈 블레이드 모델링을 통한 터빈 발전기 축 시스템의 기계적 토크 응답 분석
박지경(Ji-Kyung Park),정세진(Se-Jin Chung),김철환(Chul-Hwan Kim) 대한전기학회 2015 전기학회논문지 Vol.64 No.9
Turbine-generator torsional response is caused by interaction between electrical transient air-gap torque and mechanical characteristics of turbine-generator shafts. There are various factors that affects torsional interaction such as fault, circuit breaker switching and generator mal-synchronizing, etc. Fortunately, we can easily simulate above torsional interaction phenomena by using ElectroMagnetic Transient Program (EMTP). However, conventional EMTP shows the incomplete response of super- synchronous torsional mode since it does not consider turbine blade section. Therefore, in this paper, we introduced mechanical-electrical analogy for detailed modeling of turbine-generator shaft system including low pressure turbine blade section. In addition, we derived the natural frequencies of modeled turbine-generator shaft system including turbine blade section and analyzed the characteristics of mechanical torque response at shaft coupling and turbine blade root area according to power system balanced/unbalanced faults.
송전선로 고장제거 지연에 따른 동기 탈조 계전기 동작 검토
박지경(Ji-Kyung Park),김광현(Kwang-Hyun Kim),김철환(Chul-Hwan Kim),유영식(Young-Sik Lyu),양정재(Jeong-Jae Yang) 대한전기학회 2017 전기학회논문지 Vol.66 No.10
Generally, electrical torque in synchronous generator is balanced with the rotor mechanical torque under steady-state condition. Thus, the synchronous generator rotor rotates at constant speed. However, under fault condition, the electrical torque output is suddenly decreased and the sum of both torques does not remain constant. If the mechanical torque is not decreased at the same time, the generator rotor would accelerate. Therefore, this accelerating generator rotates at different speeds with respect to other generators in the power system. This phenomena is called as Out-of-Step (OOS). In this paper, we presented a certain two-step type quadrilateral OOS relay setting, which is applicable in actual field, and examined the validity of its setting value with OOS simulation conditions due to delayed fault clearing in transmission line. In order to conduct the study of OOS relay characteristics, we checked the impedance locus and generator output characteristics under the various delayed fault clearing conditions. Moreover, we proposed a countermeasure for avoiding the misoperation of OOS relay during the stable swing by modifying the setting values.