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As an important part of power grid’s construction and development, it is imperative to establish informatization and intelligent power grid planning system, in order to deal with the change of technology and idea caused by the electric power big data. In the view of data acquisition, processing and application schemes of power grid planning system in the background of big data, a new planning system was proposed. Then, the acquisition of big data and the application of unstructured data in power grid planning were analyzed in detail. This paper proposed some suggestions for the promotion of the new power grid planning system from aspects of technology, staff, management, etc.
To improve the prediction accuracy of short-term load in holidays, this paper proposed a load prediction method based on the combination of base value and normalized curve, as well as the grey correlation degree of meteorological correction. The principle of “near greater far smaller” was also taken into account in the base value prediction, and the index smoothing method was improved and used for the load forecasting in holidays. The smoothing factor was determined using 0.618 optimization methods, and the samples in correlation days were processed with using index smoothing method. It was suggested that the similarity of load fluctuation in same holidays should be considered and the meteorological correlation should be analyzed with using grey correlation degree, during the prediction of normalized curve. According to 96 points holidays load forecasting for a city in Guangdong province, the accuracy of the prediction method was better, which verified the feasibility of this method. In this model, the base values of normal days and the short-term load forecasting method of normalized curve were used for the load prediction in holidays, which could overcome the problem of poor prediction accuracy caused by poor samples, and could be a reference for the power company to forecast holiday loads.
Study on magnetizing inrush current of converter transformer, which caused by no-load closing, is an important basis of the design of overvoltage and filter and the configuration of protection in UHVDC projects. In order to study the causes of magnetizing inrush current of UHVDC converter transformer, the production conditions of magnetizing inrush current were illustrated in principle based on the saturation characteristic curve of ferromagnetic material. Combined with the simplified mathematical and physical model of single phase converter transformer, the simulation model of electromagnetic transient was constructed to verify the derivation, based on ±1 100 kV UHVDC hig-side converter transformer. The calculation results of main circuit parameters were provided for transformer manufacturers as design input to get the saturation characteristics of converter transformer. Finally, the influence of short circuit capacity, closing resistor and phase selection on magnetizing inrush current and its restraining was studied. The research result has guiding significance in the magnetizing inrush current and its restraining for UHVDC converter transformer, especially ± 1 100 kV UHVDC system.
According to the problems of baseline jitter in chromatogram, errors or missing recognition in chromatographic peaks, which were caused by the field interference of monitoring device, this paper proposed an analysis method with multi-parameter weight. First, this paper calculated the offset time of peak, the half width of the peak shape, the similarity of the peak shape compared with the standard peak, the peak height and other characteristic parameters, and made normalization processing for these parameters. Meanwhile, this paper set the parameters of the right weight under different conditions, and comprehensively judged peak difference between true and false peaks. Test results show that the algorithm can avoid the impact of site disturbance and improve the accuracy of the peak detection for the gas with low concentrations, which can help improve the monitoring reliability of transformer oil dissolved gas.
Based on the theory of thermal elastic-plastic coupling mechanics, this paper firstly analyzed the welding thermal effect of the inserted flange connection on UHV steel tube transmission towers with using finite element numerical simulation method. The results show that the finite element method is applicable for the analysis on the nonlinear heat conduction problem during welding. The effect of high-temperature melting of welding will result in the irreversible plastic deformation. After cooling, the steel pipe near the welding area shrinks toward the centre of the section, which increases the brittleness of steel. Due to the temperature field effect of welding area, the influencing region of weld residual stress is formed after cooling. According to calculation results of Q345 steel with 1 500 ℃ welding temperature, 30 ℃ temperature boundary, the maximum axial residual stress is up to 44% of the designed yield strength （345 MPa）, and the serious influencing range is about 4 times of the weld from the welding ring.
Considering the possibility of maloperation or miss trip in switch and protection, this paper proposed a fault diagnosis method for transmission lines based on the data of electrical information. Firstly, it preprocessed the massive alarm information of the wide area measurement system （WAMS） terminal, and filtered out irrelevant data； then, it determined the fault boundary field according to the electric quantity data； finally, it used the improved ROC change rate index function to calculate the change of current mutation, and find the fault zone with maximum velocity current for fault diagnosis. According to the simulation and the real power system fault, the proposed method can accurately and quickly diagnose the fault, save the data using unit and enhance the efficiency of diagnosis.
To improve the power supply reliability of power system and reduce the incidence of large-scale cascading failure, this paper presented a new line importance degree evaluation index for the propagation of cascading failures, which was used to quantify the impact of transmission line fault on cascading failure propagation. According to the evaluation results of line’s importance degree, this paper proposed the matching model of transmission capacity, which could reasonably configure the transmission capacity of system, and optimize the load rate distribution of system, so as to improve the power supply reliability of power system. The simulation experiment results show that in the case of transmission capacity redundancy （the same overall load rate of system）, the transmission capacity matched in the proposed optimization model or the adjustment of load rate distribution can prevent the evolutionary trend of load rate to heterogeneous distribution during fault propagation process, so as to reduce the risk of large-scale cascading failure.
To design a new packet capture and analysis tool, first of all, this paper analyzed the principle of PRP around with network redundancy. Then, based on parsing new packet structure, this paper developed the packet capture and analysis tool containing the sampling values of PRP in Windows platform, by using the network development kit Wireshark and combining with the interface design tool GTK. At last, the feasibility of protocol analysis tool was verified with using the interface function of WinPcap to simulate device to send packets. The results show that this tool can correctly analyze the load content of data packet, which has great significance to the promotion of the second edition of IEC 61850.
Compared with common aluminium conductor steel reinforced （ACSR） with equal outside diameter, the DC resistance of energy-saving conductor is lower, which can decrease the power losses of transmission line and achieve energy-saving effect in the premise of without reducing the mechanical properties of wires. Combined with a typical 500 kV AC double-loop transmission lines, this paper comparative analyzed the power loss and ontology investment of three kinds of energy-saving wires （high conductivity ACSR, ACAR, moderate-strength AAAC） with the same outside diameters, by taking common ACSR as reference； and put forward the applicable scopes of three energy-saving wires by contrasting the annual cost of each wire scheme in several different boundary conditions （transmission capacity, electricity price and wire price）, which could provide some references for the selection, popularization and application of energy-saving wires in transmission lines.
