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Cai X.-L.,Guangdong Power Grid Dispatch Control Center | Song G.-B.,Xian Jiaotong University | Gao S.-P.,Xian Jiaotong University | Suonan J.-L.,Xian Jiaotong University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

It is pointed out that DC transmission line current mutation characteristic protection and AC line protection traveling wave current polarity protection are essentially the same. The pilot directional protection of VSC-HVDC cable lines can be achieved using current fault component polarity and fault component protection criterion. In respect to the presence of proximal relay protection disoperation, fault pole choose and other issues, when the principle is used for the protection of VSC-HVDC cable lines, the applicability study is conducted and solutions are given. The system of VSC-HVDC is built in PSCAD and frequency-depend parameter cable line model is adopted. The simulation results show that the principle proposed is simple, reliable, practical with absolute selectivity and only low sampling frequency is needed. Source


Song G.,Xian Jiaotong University | Chu X.,Xian Jiaotong University | Cai X.,Guangdong Power Grid Dispatch Control Center | Gao S.,Xian University of Science and Technology
International Journal of Electrical Power and Energy Systems | Year: 2013

This paper presents a novel pilot protection principle for VSC-HVDC cable lines based on fault component current. In the transient process of cable line, if a fault occurs over the cable line, the current measured at both convert stations would have the same changing direction and the signs of the fault component current at both convert stations are the same to each other; otherwise, if a fault occurs beyond the cable line, the current measured at two convert stations would have the opposite changing direction and the sign of the fault component current at both convert stations are opposite to each other. According to this characteristic, the directional element can be located at both convert stations and state signal can be sent to the other station. Thus, the pilot protection principle can be implemented only using two terminal current. In addition, the setting principle is proposed based on fault component current in this paper. The proposed pilot protection principle is simple, reliable, and practical. It can be implemented with a low sampling rate and does not need the current data synchronization seriously. Compared with current differential protection, the proposed method has a low requirement on baud rate. At the same time, various faults are simulated by using the system of VSC-HVDC built in PSCAD/EMTDC, in which frequency-dependent parameter cable line model is adopted. The simulation results show that the method can identify the fault reliably and rapidly in different conditions only using the current measured at both convert stations and has sufficient sensitivity for high resistance ground fault. © 2013 Elsevier Ltd. All rights reserved. Source


Song G.,Xian Jiaotong University | Chu X.,Xian Jiaotong University | Cai X.,Guangdong Power Grid Dispatch Control Center | Gao S.,Xian University of Science and Technology | Ran M.,Xian Jiaotong University
International Journal of Electrical Power and Energy Systems | Year: 2014

This paper presents a novel method for locating fault on VSC-HVDC transmission line using one terminal current data. The proposed method is developed based on the natural frequency of distributed parameter line model. In the presence of the large shunt capacitor at both terminals of the VSC-HVDC line, the high frequency traveling wave is approximately totally reflected at the terminals. It is found that the value of natural frequency of VSC-HVDC transmission line is only related to fault distance and wave speed. Using this characteristic, a single-end fault location method is developed. The natural frequency can be obtained by the PRONY algorithm. Compared with traveling wave method, this approach can use any section of the in-fault data to locate fault, without having to capture the instant at which wave-front arrives, which requires higher sampling rate. A short data window is sufficient for extracting natural frequency accurately in practice. The proposed method is verified using the frequency-dependent line model in EMTDC. The simulations have demonstrated validity, rapidity and accuracy of the proposed fault location algorithm. © 2014 Elsevier Ltd. All rights reserved. Source


Liu C.,North China Electrical Power University | Wu M.,North China Electrical Power University | Xiong C.,Shanghai Electric Power Company | Lu E.,Guangdong Power Grid Dispatch Control Center | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2014

Fast restoration from a large scope blackout is very important to power systems. However, the existing optimal objective and model to start-up all the generators may cause problems that some of the generators are ramping while others are waiting. To solve this problem, considering the generator regulation characteristics, we presented a minimizing variable constrained maximum value model to describe the actual problem. Through introducing a time variable t, the variable constrained optimization problem was converted to a constrained optimal power flow (OPF) problem, which can be solved by using interior point method. By using the proposed model and method, the optimization method considering the characteristics of the generator for power system black start was proposed in this paper. Numeric tests on IEEE 30-bus system show that the proposed algorithm is effective and can obviously reduce the restoration period of the system. The proposed method has been successfully applied to the restoration decision software of power systems in Guangdong Power Grid Corporation. © 2014 Chinese Society for Electrical Engineering. Source

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