توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱A Thermodynamic Model for Prediction of Asphaltene Precipitation from Crude Oils
نویسنده(ها): ،
اطلاعات انتشار: چهاردهمین همایش بین المللی نفت، گاز و پتروشیمی، سال
تعداد صفحات: ۱۰
In this study , a molecular thermodynamic model has been proposed for asphaltene precipitation under live oil conditions , at a wide range of pressures (up to reservoirs pressures) . The model is assumed that the precipitation phenomenon is a reversible process , and an equation of state SRK Eos is employed for phase behavior prediction. in this model a VLE and then SLE calculation is performed separately and sequentially.the characterization of unknown –heavy fraction of petroleum C7+ is obtained by the generatized molar mass distribution model [2], in which C7+ is represented by tour pseude–components. in this work the two heaviest pseudo – components of C7+ are identified as asphagtenes, that are considered as precipitating components where the lower pseudo –components are not . the model is verified by its ability to prediction of asphaltene precipitation in different thermodynamic conditions (T,P,and composition). also by using this model we are able to study the effect of pressure temperature and composition on the asphaltene precipitation.<\div>

۲Improving Capacitive Voltage Transformer Response and Its Impact on Distance Relay Performance
اطلاعات انتشار: بیستمین کنفرانس مهندسی برق ایران، سال
تعداد صفحات: ۶
Capacitive voltage transformer (CVT) has an ideal steady state response at the system power frequency, while its dynamic response is inferior. This may lead to the misoperationof distance relays during a fault. This paper presents a new method in order to correct CVT transient response. Theproposed method is able to eliminate transients emerging in the CVT output for various fault conditions and CVT parameters in the real–time. The simulation results reveal that the modifiedCVT exhibits a low percentage error. Moreover, the percentage overreach of distance relay connected to the modified CVT is considerably reduced<\div>

۳Voltage Transformer Protection Based on Distinguishing Ferroresinance from Permanent Faults
نویسنده(ها): ،
اطلاعات انتشار: کنفرانس بین المللی یافته های نوین پژوهشی درمهندسی برق و علوم کامپیوتر، سال
تعداد صفحات: ۱۰
Ferroresonance is highly probable in voltage transformers connected to ungrounded power systems.It is important to damp transient oscillations after ferroresonance occurrence in order to improve accuracy of measurements as well as protecting voltage transformer. One of the most effective methods to suppressferroresonance oscillations is connecting a damping resistor at open delta connection in three phase systems. However, when a permanent fault happens, zero sequence currents damage the resistor severely.This paper offered a new algorithm to distinguish ferroresonance conditions from permanent faults andisolate the damping resistor when a permanent fault condition is detected. Simulation results certify the accuracy and practicality of the proposed method.<\div>

۴Impact of Transformer Magnetic Characteristic on Voltage Measurements during Ferroresonance
نویسنده(ها): ،
اطلاعات انتشار: کنفرانس بین المللی یافته های نوین پژوهشی درمهندسی برق و علوم کامپیوتر، سال
تعداد صفحات: ۱۱
Ferroresonance phenomenon is likely in cable distribution systems particularly in ungrounded systems. The distortion amount of voltages and currents as well as overvoltages and overcurrents in the system are a function of system parameters such as phase to ground capacitance and transformer magnetic characteristic.In this paper a typical distribution system with three transformers having different core characteristics is considered and ferroresonance effect on measured voltages is studied for various conditions using Electro–Magnetic Transient Program (EMTP). Simulation results revealed that the severity of ferroresonance and voltage distortions in modern power transformers feature high inductance in their linear region and low core losses is more than conventional ones. The results also indicated that the total harmonic distortion of voltage during ferroresonance greatly depends on the system parameters<\div>
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