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Earlier calculations of geomagnetically induced currents (GICs) in Chinese power grids have mainly concentrated on the highest voltage-level system whose geomagnetic risk is considered to be the largest, thus ignoring secondary voltage-level systems. With the 1000-kV system being newly added to China's power system, it is significant to figure out the interaction between GIC in the 500 kV [extremely high voltage (EHV)] system and GIC in the 1000 kV [ultra-high voltage (UHV)] system. Based on the North China-Central China-East China Power Grids, this paper establishes a single-voltage grid by only considering the 1000-kV system and a dual-voltage grid by considering the 1000- and 500-kV systems and investigates GIC in these two grids by developing their GIC “Full-node models.” The impact of the 500-kV system on GIC in the 1000-kV system is analyzed. GIC risks in the UHV and EHV systems are assessed by comparing calculated GIC data with monitored values of GIC. The results show that the impact of the 500-kV system on GIC in the 1000-kV system is obvious, both the EHV and the UHV grid have a high GIC risk. So calculating GIC in the UHV system and in the EHV system should utilize GIC modeling methods for multivoltage power grids. [ABSTRACT FROM PUBLISHER]

This paper presents an investigation into cloud-to-ground lightning activity data collected by a lightning detection system in the Guang-Dong Province, the southernmost in China. Annual lightning days are acquired and ground flash density maps are constructed from the database, which contains the information of more than one million flashes. The lightning days are compared with annual thunderstorm days collected by the Guang-Dong Meteorological Agency, and a weak correlation is noted. The correlation between ground flash density and thunderstorm day is studied, and an empirical formula is presented. The relationship between transmission line faults and ground flash density is discussed in this paper too. It is noted that the correlation with the faults caused by lightning is relatively high. The correlation coefficient does not significantly vary with the threshold of discharge current set for constructing the map of revised ground flash density. [ABSTRACT FROM AUTHOR]

Due to the uneven geographical distribution between load and wind power, currently it is difficult to integrate the large-scale wind power into the State Grid in China. There are significant wind curtailments for wind farms due to system restrictions. This paper proposes a new way of utilizing wind power, i.e., in-situ consumption, as an alternative to the costly development of long-distance transmission of large-scale wind power. Electrolytic aluminum load, which is one of the most typical high energy consuming loads, is employed to absorb the excess wind power in western China. An actual isolated industrial power system for aluminum production driven by wind power and coal-fired power is described. The penetration level of wind power in the isolated power system is up to 48.8%. The power imbalance between generation and load demand caused by wind power fluctuation or the tripping of coal-fired generators can dramatically impact the frequency stability of the isolated power system, which is of small inertia. An online identification method of power imbalance based on Wide Area Measurement System (WAMS) is presented. According to the characteristics of the electrolytic aluminum load, a system frequency control method by regulating the bus voltages of aluminum loads to eliminate the power imbalance is introduced. The simulation is done in Real Time Digital Simulator (RTDS) and the results verify the validity of the proposed frequency control method. [ABSTRACT FROM PUBLISHER]

The article presents an introduction to a paper about developments, current status and future prospects for ultra-high-voltage (UHV) transmission in China. The authors of the paper examined the accomplishments of the country in the field of UHV transmission research. Their aim is to enhance the safety and reliability of the future UHV grid in the country. Furthermore, they aim to provide a reference for other countries working to create similar UHV grid. One of the primary problems which complicate the country's attempts to distribute electric power more effeciently is the vastness of its electric grid system.

Parallel adjacent erection of UHVAC and UHVDC transmission lines in the same corridor will occur in the east of China. So the calculation method for the ac and dc hybrid electric field over the ground surface under this type of lines need to be studied so as to satisfy the requirements of engineering design and environmental protection. Based on the analysis of mutual influences between UHVAC and UHVDC transmission lines in the same corridor, a calculation method is proposed. The corresponding calculation results obtained with this method are shown as follows. Near the center of UHVAC and UHVDC transmission lines in the same corridor, especially in the side of UHVDC transmission lines, the change of voltages applied to ac conductor bundles can evidently affect the magnitude of the hybrid electric field; the hybrid electric field is sometimes enhanced and sometimes diminished, and the total effect appears subdued in an ac cycle. Except for the area close to the center of this type of lines, that whether the mutual influences between UHVAC and UHVDC transmission lines are considered or not can hardly affect the lateral distribution of the hybrid electric field. [ABSTRACT FROM AUTHOR]

The China Southern Power Grid (CSG) interconnects four provincial power grids: Guangdong, Guangxi, Yunnan, and Guizhou. It is the only ac/dc hybrid grid in China with dual ac/dc transmission corridors in parallel. The practical high-voltage direct current (HVDC) control scheme of the CSG and its modeling is first presented. Both the stability and small-signal analysis environments of 2005 CSG are established using a commercial software package. Interarea oscillatory modes among the four provincial power grids are then investigated. On the basis of modal analysis, a hierarchical optimization scheme is implemented for the parameter setting of selected power system stabilizers (PSS) and HVDC damping controllers. Digital simulations show that proper coordination of the PSS and HVDC modulation controllers can effectively suppress the interarea oscillation in large-scale ac/dc hybrid power systems under a wide range of operating conditions. [ABSTRACT FROM AUTHOR]

In view of frequent and severe overvoltage failures of 40.5-kV vacuum circuit breakers (CBs) while switching off the shunt reactors in the 35-kV distribution systems in China, a series of field tests was carried out to determine the mechanism of this kind of disruption. The transient process and phenomena were analyzed and summarized based on the overvoltage waveforms obtained from the field tests. The experimental results indicated that the probability of reignition is greater for a 40.5-kV CB than in a 12 kV one. The interphase overvoltage was especially critical. The causes of severe overvoltages were analyzed, and it was indicated that the difference of CBs, multireignitions by the interphase coupling, and the different application conditions were the main effect factors. In addition, some suggestions were given. [ABSTRACT FROM AUTHOR]

Along with the rapid growth of the national economy in China, the electric utility is faced with an ever rising demand for electricity and the problem to solve large capacity power transmission. Under the support of the High Technology Research & Development Program of China, a 1.5 kA/10.5 kV 10-m long 3-phases HTS transmission power cable and a 75-m long, 3-phase, 10.5 kV/1.5 kA HTS power cable have been developed successfully by the Institute of Electrical Engineering, Chinese Academy of Sciences. The 75-m long HTS power cable operates now at a local live distribution grid of 6.6 kV to supply electric power for Changtong's factory in Baiyin, Gansu Province. The cable operates stably and reliably over 7000 hours since December 2004. [ABSTRACT FROM AUTHOR]