Sun S.,Kunming University of Science and Technology |
Shu H.,Kunming University of Science and Technology |
Wang J.,Liaocheng Power Supply Company |
Sun X.,Kunming University of Science and Technology
Gaodianya Jishu/High Voltage Engineering | Year: 2013
The sequence of three-phase re-closure greatly influences the closing voltage of 750 kV transmission line. Therefore, on the basis of distributed-parameter models of 750 kV transmission line with and without shunt reactors respectively, we analyzed voltage levels of three-phase reclosing on a three-phase fault in a single-phase fault, and set a strategy for reclosing sequence in the prospective of constraining reclosure over-voltage. The results reveal that, for reclosing to three-phase transient fault, the reclosing sequence is consistent with planned closing: a) for a transmission line in the absence of shunt reactor, large sources should reclose first; b) for a transmission line in the presence of shunt reactor, closing on the large source side when the compensation degree is less than the given critical value can suppress closing voltage. The results also reveal that, it is more complex for reclosing at single-phase fault: a) for a transmission line in the absence of shunt reactor, the closing sequence should be determined according to the conditions of fault point and the line impedance, i. e. tripping at small source side as well as far-from-fault side firstly can decrease the residual voltage of sound-phase, while tripping large source side and close-to-fault side firstly decreases the closing voltage; b) for a transmission line in the presence of shunt reactor, peak value of three-phase reclosing over-voltage is affected by capacity of system, fault point and compensation degree; specifically, when compensation degree is less than its critical value, large source and close-to-fault side should reclose first, otherwise the small source and far-from-fault side should reclose at first; c) if the large source side is not the same as close-to-fault side, the reclose sequence depends on the product of the coefficient of increment of power-frequency voltage and the coefficient of increment of voltage induced by single-phase fault. The proposed setting strategy of reclosing sequence is verified by multiple simulations in PSACD.
Jia X.,North China Electrical Power University |
Ma J.,North China Electrical Power University |
Zhang Y.,Yangquan Power Supply Company |
Zhao Q.,Liaocheng Power Supply Company
Proceedings - International Conference on Electrical and Control Engineering, ICECE 2010 | Year: 2010
Voltage fluctuation and flicker has become an important concern for customer, especially those who are sensitive to power quality at the point of common coupling. While voltage fluctuation and flicker occurs, the identification of flicker disturbance sources has great significance to confirming responsibility of power quality and bringing power quality under control. The voltage level of flicker disturbance source is identified according to the flicker transforming characteristic among different voltage levels. By analyzing simplified equivalence circuit of power system, a novel method to determine flicker disturbance source is proposed, which utilizes the directions of power flow of flicker frequency components and the percent of amplitude of flicker frequency components. Finally, the feasibility of this method is verified by results of RTDS test. © 2010 IEEE.
Liang J.,Liaocheng Power Supply Company |
Wang X.,Liaocheng Power Supply Company |
Shi L.,Liaocheng Power Supply Company |
Yang J.,North China Electrical Power University
Advanced Materials Research | Year: 2013
To develop an economic and effective online monitoring method is necessary as the normal running of distribution line is critical to ensure the reliability of power system. And the distribution line state monitoring technology improved steadily nowadays, the monitoring of operating status can be achieved by using online monitoring devices. However, its installation and maintenance cost a lot, it is poor in economy. A new method, in which line resistance was selected as a reference quantity, was proposed in this article. The monitoring of distribution line running status can be realized by analyzing the line resistance value that calculated by real-time measurement data. The method improves the utilization of information system and requires no additional investment costs. And the example verified the validity of the method; it is possible to learn about the operational status timely through analyzing the changes in line resistance value. © (2013) Trans Tech Publications, Switzerland.
Wang K.,State Grid Corporation of China |
Sheng G.,Shanghai JiaoTong University |
Sun X.,Liaocheng Power Supply Company |
Wang W.,NARI Group |
And 2 more authors.
Dianwang Jishu/Power System Technology | Year: 2013
It is significant for secure and economic operation of transmission lines to predict dynamic line rating (DLR) in realtime mode and reasonably arrange the operation mode during peak load period and scheduling management, meanwhile it can provide technical support for determining grid-connected capacity of intermittent renewable energy resources such as wind power and so on. For this reason, using redial base function neural network (RBFNN) an online prediction method to implement the prediction of DLR is proposed. Firstly, the online learning and prediction of wind and sunshine radiation temperature is performed by RBFNN, then based on IEEE 738 standard the online short-term DLR is predicted. In the prediction of DLR by use of typical measured data in summer season and winter season, it is found that the maximum relative error in the prediction of dynamic capacity for next one, two and four hours are less than 10%, 20% and 40% respectively. Combining the short-term load forecasting method with the proposed method, the decision-making can be provided to intelligent dispatching during the peak load period in the region lacking of power supply.
Chen Y.B.,Shanghai JiaoTong University |
Sun Y.,Liaocheng Power Supply Company |
Sun X.R.,Liaocheng Power Supply Company |
Sheng G.H.,Shanghai JiaoTong University |
Jiang X.C.,Shanghai JiaoTong University
Applied Mechanics and Materials | Year: 2014
The safe operation of power transformers mainly depends on proper functioning of insulation, whose status is revealed by temperatures. Applying ZigBee wireless network, a real-time temperature on-line monitoring and analysis system is developed to view the operation status of underground distribution transformers and process fault diagnosis. Furthermore, using the top-oil and hot-spot temperature calculation method in IEEE Std C57.91-1995, the system can compute a prediction of those temperatures with current load ratio and ambient temperature. System will display early warnings if temperatures are much higher than expected ones, in which way insulation aging can be handled in advance. Insulation fault and big disasters will be prevented. © (2014) Trans Tech Publications, Switzerland.