Session C2.4: AC Transmission and Distribution System

In order to prevent rolling stones from impacting the tower foundation of the transmission line and causing damage or instability of the tower, this article uses Rocfall software to establish a rolling rock movement model for a typical slope accident, and obtains the rolling trajectory, bouncing height, and impact of the rock through simulation calculations. Kinetic parameters such as kinetic energy, then combined with the Hertz theory, based on the conservation of energy theory and the Japanese formula to obtain the maximum impact force when different rolling stones impact the tower, based on the calculation results of the maximum impact force and the yield strength of the Q235 angle steel to evaluate the danger of the rolling stones to the tower . The calculation results show that the rolling stone impact force on the legs of the tower is 3.6 × 10⁶Pa to 2.55 × 10⁷Pa, which exceeds the yield strength of the tower material. At the same time, the best control position of the slope surface is selected from the bottom of the slope by 25 to 75 meters, it provides a theoretical basis for the design, construction, operation and maintenance, and protection device design of transmission lines in high-rolling-rock risk areas in mountainous areas, which is conducive to the safe and stable operation of iron towers.

Wu Tian(1983-02), Senior engineer, graduated from Wuhan University in June 2012, majoring in High Voltage and Insulation Technology. In 2012, joined the live working laboratory of the Institute of High Voltage Research, China Electric Power Research Institute, and engaged research work on live working, power grid operation and maintenance and external insulation, participate in the development of four industry standards. He joined the School of Electrical and New Energy of three Gorges University in May 2017.

When the lead wires of a inductive potential transformer (PT) of a distribution network are overlapped with electricity, ferro-resonance often occur, which will cause serious damage to the power system. In order to understand the resonance characteristics of PT uninterrupted operation in distribution network, an ideal transformer is used to simulate the PT, and the TYPE98 model is used instead of the excitation inductance. Based on this, a ferroresonance model in 10kV isolated neutral electrical system is established, and simulation is completed in ATP-EMTP and carried out simulation experiments. The effects of line length, PT excitation characteristics and PT neutral connection on the PT ferroresonance of distribution network were studied respectively. The simulation and experimental results show that as the line length increases, the system will have high frequency, fundamental frequency and frequency division resonances in succession. When the line is increased to a certain length, the PT ferroresonance phenomenon will disappear; it has better excitation characteristics The non-linear resistance of the neutral point of PT or PT primary winding can effectively suppress the occurrence of ferroresonance.

With the construction and development of power grid in Northwest China, 750kV four-circuit line on the same tower has become the key technology to solve the problem of corridor shortage. To ensure the safe maintenance of 750kV four circuit line on the same tower, in this paper, a 1:1 simulation tower body is made according to the four layer cross arm structure, and the gap discharge characteristics of special live working conditions are obtained. According to the characteristics we acquired the minimum safety distance of equipotential worker to the tower body and the lower cross arm, which is 4.2m and 4.3m respectively, and the minimum safety distance between phases is 5.8m, the minimum combined gap distance between the two phases is 6.3m. By simulation and calculation, we obtained that the maximum induced voltage is 64.5kv when two ends of the line are not grounded during outage maintenance, and the maximum induced voltage is 114v-195v after both ends are grounded, while the maximum peak value of the induced current in the loop is in the range of 0.57A-1.5A. The research results of this paper can provide technical support for safe maintenance of 750kV four-circuit line on the same tower.

Master's degree, engineer, working at China Electrical Power Research Institute, mainly engaged in research on live working technology.

With the rapid development of technology in unmanned aerial vehicles (UAV), more and more UAVs are used by power supply companies for power line inspection and maintenance. However, a large quantities of aerial images captured by UAVs are processed manually at present, which relies on prior knowledge of power towers and is not only time-consuming but also inefficient. Worse still, the geographical positions of abnormal power towers are difficult to be obtained so that the maintenance team has no direction to proceed. In this work, we propose a deep learning based method for detecting and locating abnormal power towers from the aerial images captured by UAVs. In this method, an objection detection algorithm based on deep convolutional neural network (CNN) is firstly designed to identify and detect abnormal power towers from aerial images. Secondly, the geographical positions of the detected abnormal power towers are approximated by UAV metadata recorded in aerial images (e.g. pixel size, altitude, pitch angle, roll angle, yaw angle, et al.) and several coordinate transformations. Compared with the classical image processing methods, the present method is automatic and end-to-end, and can be easily applied in the UAV based inspection of power transmission lines.

Dr. Linlin Zhong is an Assistant Professor (Lecturer) with Southeast University. His current research interests include the interdisciplinary study of plasma physics, electrical engineering, and computer science, including computational plasma physics, gas discharges, and artificial intelligence.

Corona noise has become an important part of noise in substations, especially in areas with severe operating conditions such as high winds, sand and dust. UV imaging detection technology can effectively find corona discharges on the surface of substation fittings. In this paper, by analyzing the test results of corona noise and ultraviolet imaging of typical fittings of 500kV substations, the main corona noise generating areas in the substation 500kV area are found. Based on the commonly used fitting structures, improvement measures are given for areas prone to corona noise. The results can provide a basis for corona noise control in 500kV substation.

Xing Ge(1995), male, master, engaged in research on  external insulation technology of power transmission,

This paper proposes a method for voltage collapse point estimation in AC-DC hybrid power systems considering the voltage source converter-based high voltage direct current transmission (VSC-HVDC). Using the proposed holomorphic embedding method (HEM) with physical germ solution, analytical power flow solution of the AC/DC hybrid power system can be calculated without iteration, and it guarantees the convergence if the solution exists. Considering the capacity limit of VSC-HVDC converter, an accurate loading limit at each load bus can be obtained to confirm the voltage collapse point of the AC/DC hybrid system. Additionally, different control modes of the VSC-HVDC system can be adapted for the proposed approach. In this paper, the HEM application is firstly extended to the power flow calculation of AC-DC system containing VSC-HVDC. Case studies on a five-bus test system are implemented in MATLAB in detail to verify the effectiveness of proposed method.

Chengxi Liu, received the B.Eng. and M.Sc. degrees from Huazhong University of Science and Technology, Wuhan, China, in 2005 and 2007, respectively, and the Ph.D. degree from the Department of Energy Technology, Aalborg University, Aalborg, Denmark in 2013. Now he is a professor in School of Electrical Engineering and Automation, Wuhan University. His research interests include power system stability and control, renewable energies, and the applications of artificial intelligence.