جلوگیری از جریان اتصال کوتاه در ایستگاه های تبدیل فرکانس و تأثیر آنها بر قابلیت اطمینان سیستم قدرت
Abstract
I- Brief Introduction
II- Analysis of Single-Phase Short-Circuit Current at Converter Station
III- Analysis of Suppression Measures on Single-Phase Short-Circuit Current at Yibin and Fulong Converter Stations
IV- Conclusion and Advice
REFERENCES
Abstract
Aiming at the issue that the single-phase short-circuit current at the 500kV side of Yibin and Fulong converter stations has exceeded the breaking capacity of breaker, the reason is analyzed and the measures are put forward to reduce the single-phase short circuit, including limiting the output of thermal power near field, converter transformers neutral grounding by small reactance and 500kV lines adding series reactors. The limiting effects of single-phase short-circuit current and the impacts on power grid equipment operation and power supply reliability of different measures are compared. Feasible suggestions for reducing single-phase short-circuit current and improving power grid reliability are given.
BRIEF INTRODUCTION
Along with the expanding of the power grid construction and the strengthening of the AC and DC hybrid system, the short-circuit current level of the power grid is increasing year by year, and the single-phase short-circuit current of some buses is larger than the three-phase short-circuit current. Short-circuit current exceeding standard will bring difficulties to equipment selection, endanger the safety of people and equipment, which has become a main problem faced by power system planning and operation [1]. In the current Power System Analysis Software Package (PSASP), the converter transformer model is integrated in the DC system model. The DC system is treated as a load and does not provide short-circuit current when the model is used in the three-phase and single-phase short-circuit calculation. But in the actual power system, the converter transformer has a significant effect on the single-phase shortcircuit current. The capacity of converter transformers at Yibin and Fulong stations is respectively 9696MVA and 7706MVA, which is very large, and the converter stations have closely connection with neighboring 500kV power network [2]. Considering the influence of converter transformers on the zero sequence impedance and the centralized access of large capacity mating power supply such as Xiangjiaba and Xiluodu, the single-phase short-circuit current at the 500kV side of Yibin and Fulong converter stations has exceeded the three-phase short current or even exceeds the breaking capacity of breaker [3].