Search

In order to prevent the faults caused by the overheating phenomena of gas insulated switchgear (GIS) contacts, it is necessary to monitor and predict the temperature of GIS contacts. In view of the problems that the temperature of contacts is not easy to be directly measured and the temperature is easily affected by the operation conditions and external factors, a prediction method of GIS contact temperature based on multiple parameters is proposed in this work. The temperature distribution law of GIS under different influencing factors is investigated by employing a three-dimensional simulation model. The influencing factors are contact resistance, load current, ambient temperature, wind speed, SF6 pressure and solar radiation intensity. The reliability of the model is validated by use of heat circuit model. The results indicate that the key factors to predict the contact temperature are the shell temperature rise, load current, wind speed, SF6 pressure and solar radiation intensity. At the same time, the influence of ambient temperature can be ignored. Further, the back propagation (BP) neural network is adopted to predict the temperature rise of the contacts with the above factors. The predicted temperature rise is compared with the calculated one of the model, and the error is in the range of -0.70~0.68 ℃. The method comprehensively takes into account the influence of various factors on the GIS temperature field, and it helps to give a reference for the temperature prediction of GIS contacts based on external sensors.

The purpose of this paper is to obtain the temperature variation characteristics of the optical phase conductor, the criteria of whether the transmission line is covered by ice or not and the methods for predicting the thickness of ice for the case which is more close to the actual ambient temperature. In this paper,the 3D model of the temperature field of icing optical phase conductor is established when the ambient temperature conforms to the sine function,and the finite elements method is used to solve it. The amplitude and lagging phase characteristics of the temperature of the icing part and the uncoated part of the transmission line are analyzed. The relationship between the lagging phase and the fluctuating amplitude of ambient temperature is investigated. The results reveal that the effect of the fluctuating amplitude of ambient temperature on the lagging phase can be ignored. The relationship between the lagging phase and the thickness of ice is studied. Then the criteria of whether the transmission line is covered by ice or not and the prediction formula of the thickness of ice based on the lagging phase feature are proposed. Finally the variations of fiber temperature are modeled and obtained when the ambient temperature varies according to 4 nonsinusoidal functions,and the error of the prediction formula of ice thickness is analyzed based on this. The proposed icing criterion and the prediction formula of ice thickness based on lagging phase are validated by simulation.

For investigation of the temperature variation characteristics of the overhead transmission line under different meteorological conditions and the influence of wind speed on the effectiveness of the overhead transmission line icing monitoring based on the distributed optical fiber sensing technology,a 3D temperature field model for the ice-covered optical phase conductor is established. The variation characteristics of optical fiber temperature under different ambient temperature,wind speed and icing-thickness are analyzed and obtained using the finite element analysis. From this,the results reveal that the temperature difference between the icing part and the non-icing part is independent of the initial value of the ambient temperature,and the critical wind speed expression separately considering the rate of ambient temperature change or icing-thickness is provided. In addition,the critical wind speed value under the ambient temperature change rate and icing-thickness within the common range is presented. Based on the wind speed value and interpolation,a more accurate critical wind speed value can be given under the ambient temperature change rate and icing-thickness within the common range. It provides a reference for researching the temperature variation characteristics of ice-covered overhead transmission lines under different meteorological conditions and the influence of wind speed on the effectiveness of overhead transmission line icing monitoring based on distributed optical fiber sensing technology.

To locate and read the complex pointer meter dial for the images with uneven illumination, blurred dial, and tilted dial, this paper firstly proposes an improved BRISK‐FREAK algorithm for dial position. Then, combined with the Line Segment Detector (LSD) algorithm, an automatic identification method for complex pointer meter is proposed. The dial of a large number of SF6 complex pressure pointer meter images are located and the results reveal that the proposed improved BRISK‐FREAK algorithm has good adaptability under strong interference. The computational speed of the proposed algorithm is 33% and 17% higher than the Scale‐Invariant Feature Transform (SIFT) algorithm and the Binary Robust Invariant Scalable Keypoints (BRISK) algorithm respectively. The positioning success rate of the proposed algorithm is 40%, 64%, and 32% higher than that of the SIFT, Oriented FAST and Rotated BRIEF (ORB) and BRISK algorithms respectively. The reading success rate of the proposed method is 94.5%, which is 19.5%, 39.9% and 14.8% higher than that of the methods based on the ORB, SIFT and BRISK algorithms respectively. It is particularly suitable for application in the actual substations to realize the identification of complex pointer meters. [ABSTRACT FROM AUTHOR]

The gas insulated switch (GIS) vibrates during operation. In order to analyze the difference between the vibration signals for loosed bolts or misaligned conducting rods at the connection of GIS shell and the normal operation without defects,a 3D model of 252 kV three-phase box-type GIS is established in this paper. Computational modal analysis is firstly performed on the model in the field of solid mechanics. Secondly,the natural frequency is determined,and the representative sixth mode shapes are obtained. By applying different loads and changing the parameters of the model,the time-domain signals of the vibration acceleration of GIS shell under the state of no fault,different number of bolts loose and different cases of conducting rod misalignment are solved in the solid mechanics field. Then the frequency-domain signals are obtained through spectrum analysis. By comparing and analyzing the difference of vibration acceleration signals of GIS shell in several cases,the characteristics of vibration acceleration of GIS shell in case of bolt loosening fault and conducting rod misalignment fault are obtained. Finally,the criteria for the above faults are obtained. Some certain reference value about the follow-up GIS equipment running condition monitoring,mechanical fault identification and vibration research have been provided in the conclusion of this paper.