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Visible and near infrared spectroscopy has been widely used to develop a method for rapidly determining organic carbon in soils or sediments (SOC). Most of these studies concentrated on how to establish a good spectral model but ignored how to evaluate the method, such as the use of detection range (max and min), resolution and error for SOC spectral analysis. Here, we proposed a method to evaluate the spectral analysis of SOC. Using 96 sediments sampled in the Yellow Sea and Bohai Sea, China, we established three spectral models of SOC after collecting their spectral reflectance by Agilent Cary 5000, ASD FieldSpec 4 and Ocean Optics QEPro, respectively. For both the calibration set and validation set in each spectrometer, the predicted SOC concentrations followed a distribution curve (function), in which the x-axis was the SOC concentrations. Using these curves, we developed these four technical parameters. The detection ranges were the SOC concentrations where the curve was near to or crossing with the lateral axis, while the detection resolution was the average difference between the two neighboring SOC concentrations. The detection errors were the differences between the predicted SOC and the measured SOC. Results showed that these technical parameters were better in the bench-top spectrometer (Cary 5000) than those in the portable spectrometers when analyzing the same samples. For the portable spectrometers, QEPro had a broader detection range and more consistent detection error than FieldSpec 4, suggesting that the low-cost QEPro performed as well as the high-cost FieldSpec 4. This study provides a good example for evaluating spectral analysis by spectroscopy, which can support the development of the spectral method.

This study introduces a circuit breaker flashover accident caused by lightning strokes in a row of Xingren convertor station in Guizhou. To find out the reason of the flashover and whether fault circuit breaker insulation coordination can meet requirements under multiple lightning strikes, the overvoltage condition of hot-standby circuit breakers under lightning surge is calculated and checked by using EMTP and full-scale high impulse voltage test of the fault circuit breaker is conducted for the first time. Owing to the hot-standby state of the circuit breaker, the flashover accident is more likely to happen when lightning surge invades the substation or convertor station again. Measures to improve the hot-standby circuit breakers’ lightning withstand level are proposed and by simulating analysis, the measure combined installing a line arrester at a tower of the inlet line and installing an arrester near a certain breaker on the line proves to be effective.

A novel integrated scheme based on relationships exploration (RE) is presented for the online estimation of the relative voltage stability margin (VSM). The proposed scheme can select the optimal variables as input features for estimation by detecting the relationship between each operation variable and the relative VSM in a large data set. Each relationship is given scores by the maximal information coefficient (MIC) and the Pearson correlation coefficient (PCC). The variables selected for estimation are corresponding to the relationships highly ranked by MIC and PCC, including linear relationships and nonlinear functional ones. Some of the highly ranked relationships are shown, curve fitted and described from the perspective of power system operation. If the data of the selected variables are obtained online from the wide area measurement system (WAMS), the relative VSM can be online estimated based on the explored relationships. The integrated scheme using RE-based process is examined on a 21-bus test system and a practical 1648-bus system provided by the software PSS/E, and it presents acceptable estimation accuracy. The impacts of training set size, selected relationships' types, total number and ranks on estimation accuracy are analyzed. The robustness of the scheme to measurement errors and topology variation is studied.