The insulation state assessment of two 200 kV HVDC XLPE cables, which have been in operation for 5 years, were performed after a breakdown fault. The electrical test including broadband dielectric spectrum (BDS) test and breakdown strength test. The material test including thermal stimulation current (TSC) test, differential scanning calorimetry (DSC) test, infrared spectrum test, degree of crosslinking test, and thermal elongation ratio test. The results show that the TSC and DSC test can represent the differences due to different breakdown energy between two cables. And the BDS, TSC and DSC test can distinguish between old and new cables. Meanwhile three indicators, including infrared spectrum, degree of crosslinking and thermal elongation ratio test of old cables were even better than new cables.

It is known that the main cause of the failure for submarine cable is damaged by external forces. As a result, regular inspection of the buried depth about submarine cable is extremely important to know the risk points and eliminate this hidden danger. Under normal circumstances, the detection of the burial depth of submarine cable requires a power outage, and a special signal with a low-voltage and different frequency should be injected onto the cable, so that the electromagnetic field of this signal could be picked up by the detection equipment to obtain the burial depth. For some key links, the submarine cables are always energized and in service, so it is not feasible to introduce a tone onto the power cables. In this paper, a device which could directly inspect the 500kV ultra-high voltage submarine cables with the cable keep running. The electromagnetic induction coil and collector of the detection device are redesigned, so that it can directly identify the signal of strong electromagnetic field with the voltage of 500kV, to avoid any saturation distortion. Using this device, the burial depth of running submarine cable could detected without power outage and additional detection tone injected. Hainan Power Grid Interconnection Projects are the only power links with great significance between Hainan Island and the mainland of China, and It is very difficult to shut down the power of these 500kV submarine cables. In December 2019, this detection equipment was installed onto the Remote Operated Vehicle to inspect the burial depth of the cables without a power outage. The result shown that it worked well and achieved great success.

In order to solve the problem that the traditional metal grading ring in the ultra-high voltage(UHV) field test is so large, heavy and difficult to install in the test field that reduce the test efficiency and increase workload, a design of new inflatable grading ring especially for integrated test platform was proposed. The material and mechanical structure of the inflatable grading ring are designed according to the environment requirements of the field test. Then the style and size of the grading ring are optimized by finite element analysis of electric field. The factory test and field test are carried out and proved that the proposed inflatable grading ring is easy to use, transport, store, and meets the requirements of field test of UHV equipment within 1200kV, which can be promoted to the future UHV field test.

AC withstand voltage test on site is an important means to test the insulation performance of UHV equipment. The traditional decentralized test devices cannot meet the requirements of installation progress of UHV GIS equipment. In view of this situation, an integrated test platform for the field test of UHV equipment has been developed successfully. In this paper, the key parameters of the transmission mechanism for erecting and transporting such as the hydraulic cylinder hinge point and the thrust are calculated with analytic method. The selection method of the hydraulic cylinder is explained. The analysis method and results in this paper provide a theoretical basis for the development and selection of similar equipment.

The 500kV submarine cable route of Hainan Networking System starts from Nanling Village, Jiaowei Township, Xuwen County, Zhanjiang City, Guangdong Province. It crosses the Qiongzhou Strait to Linshi Village, Qiaotou Town, Chengmai County, Hainan Province. Hainan Networking System 500kV AC Submarine Cable is the first ultra-high voltage, large capacity and long-distance cross-sea networking power cable in China. It is 31 km. In this article, there are three main parts. The first part introduces the status of submarine cable monitoring and the BOTDA test principle. The second part is to design a calibration experiment to calibrate the Brillouin temperature coefficient and the Brillouin strain coefficient for the test fiber of the submarine cable. The third part is to design the spatial distribution rate verification experiment of Brillouin optical time domain reflectometry analyzer to ensure the error of equipment and experiment, so that it can be applied in submarine cable in the future.

The UHV transmission technology has played a huge role in China's energy allocation, air pollution control, large-scale new energy grid access. In this paper, a self-supporting test platform suitable for UHV GIS field insulation test has been developed. The lifting of the test site was avoided. The test preparation time is reduced from 2-3 days to 4 hours. An internal structure of 1200kV integrated oil-immersed air core reactor suitable for UHV GIS field insulation test is proposed. Through mechanical analysis and calculation, the insulated support members have been optimized in the axial and radial directions. Based on the temperature field simulation, the internal temperature distribution has been improved through widening the oil channel. The top temperature of the reactor is reduced to below 60 °C. The platform has been expansion used in the valve side AC withstand voltage and partial discharge test for UHV converter transformer. The test process fully reflects the maneuverability and integration advantages of this platform. The development of this platform provides an important implementation example for the development of the field test equipment for UHV electrical equipment.

There are many factors affecting the resistance loss of wire rope over pulley, such as tension of wire rope, diameter of pulley, envelop angle and so on. In this paper, based on the mechanical model of wire rope over pulley, the bending effect of wire rope is considered. And the non-linear equations of exit tension with entry tension, pulley radius, envelop angle and bending stiffness are constructed. At last, the influence of various factors on resistance coefficient is analysed.

The force-displacement data during loading and unloading process is obtained by wire rope stretch experiment, which includes 7 different diameters ropes. Based on the data, deformation curves of elastic extension are established. It is shown that the loading and unloading curves compose of the elastic hysteresis loop because the wire rope during unloading shows obvious anelasticity. Analysing the elastic deformation curve characteristics, the values of loading and unloading curve parameters are provided by fitting the experimental data. The loading elastic modulus is constant independent of initial load, and the unloading elastic modulus is non-linear which is related with the maximum load. The elastic modulus is applied to the calculation of freight ropeway bearing cable. Compared the result with the actual project data, it shows that the method considering the wire rope anelasticity can improve the precision of bearing cable calculation.

Based on the analysis of the mutual interaction between bearing cable and traction cable of single-span circulating ropeway, the calculation method is proposed for working cables of ropeway with arbitrary loads. The 5 sets nonlinear equations are set up for the working cables according to the equal spans and altitude differences of the bearing cable and the traction cable, the constant of the load running space and the bearing cable length, and the tension balance of bearing cable and traction cable beside load. The resolving method is proposed based on the Newton iterative method. The correctness and feasibility of the method are proved by the results of engineering test. From the solution, the tension and coordinate of working cables can be obtained accurately, which is meaningful for the design and analysis of the freight ropeway.

Basis of the boom force analysis of special mobile crane for plain region in transmission line, the load type of boom design is confirmed. According to the different combinations of boom sections, the composite pattern of the different boom length is obtained to suit the actual conditions of boom overlapping. The large deformation model is employed with FEM to simulate the stress distribution of boom, and the calculation results are checked. The performance curves of rated load with different arm length and different working range are obtained, which ensures the lifting capacity of special mobile crane meeting the requirement of tower erection of transmission line. The proposed FEM of boom of mobile crane would provide certain guiding and reference to the boom design.

According to actual working condition, the catenary equations of elastic track tope for setting-up is proposed based on the cableway erection requirement, such as the erection angle of end, the initial cable length and midpoint position of cable. The mechanics equilibrium equations, the loads span equations and the consistent equations are presented by analysis of track rope stress state under loads. The nonlinear equations are constructed for elastic track tope with multiple loads and the initial values of newton iteration method are obtained to solve the nonlinear equations. The results of this method are compared with the testing results and numerical results in other literatures and the contrast verifies the reliability of this method. The method is more concise and has smaller amount of calculations with a unified form. It can provide effective means to design the cargo cableway and to check the engineering safety during the erection stage and running stage of cableway.

The nonlinear strain and stress expressions of suspension cable are established from the basic condition of suspension structure on the Lagrange coordinates and the equilibrium equation of the suspension structure is obtained. The dynamics equations of motion of the suspended cable with attached masses are proposed according to the virtual work principle. Using the spline function as interpolation functions of displacement and spatial position, the spline function method of dynamics equation of suspension cable is formed in which the stiffness matrix is expressed by spline function, and the solution method of stiffness matrix, matrix assembly method based on spline integral, is put forwards which can save cost time efficiency. The vibration frequency of the suspension cable is calculated with different attached masses, which provides theoretical basis for valuing of safety coefficient of the bearing cable of the cableway.

The contract model of the freight ropeways bearing cable and the saddle is established by FEM software, and the simulation calculation is carried out. The calculating formula for total contact pressure is fitted from the analysis result. According to setting requirement of the freight ropeway, simulation calculations of the different bearing cables are carried out under different operation conditions, and the relationships are obtained between contact pressure and influent factors, such as curvature radius of the saddle, the envelope angle and the drawing force. The results shows that contact pressure is in inverse proportion to the curvature radius of the saddle, in direct proportion to envelope angles and drawing force of the cable. Friction force between the bearing cable and the saddle made of nylon, bronze and steel three different materials are summarized through field test, and the friction coefficients applicable to the saddle of different material are obtained in combination with simulation results of the touch models.

A novel circuit breaker closing resistance instrument is designed in this paper. Super capacitor was used as test power source, and a digit signal processor as microcontroller, moreover AD526 and LM324 were used for signal amplifying and filtering. On-chip Analog-Digital converter was used to acquire voltage data. Closing resistance, loop resistance, and pre-insertion time can be measured in one closure using the instrument. Experiment results show the instrument's high precision and high reliability. Besides, the instrument is very practical and easy to use in field.

Gas insulated switchgear (GIS) is the most important equipment in the power grid. Especially, for insulation failure, the monitoring, analysis and pattern recognition technology of partial discharge in GIS is the most important. Thus a 220 kV GIS bus bar cavity was taken as an object to design three PD physical models. The PD signals on different defects were detected with the IEC60270 method. The effects of the applied voltage on the center-phase distribution and average amplitude of the discharge pulses were investigated. The experimental results indicated that the phase-resolved PD (PRPD) patterns, average amplitude and central phase changing of PD signals had very similar distribution characteristics and those of different defect had different ones. The results provide a test basis for the recognition of PD types and a deeper study of the mechanism of PD.

In order to make more profound comprehension of propagation characteristics for E-M signals from partial discharge in GIS, the GIS models with isolating switch are creation to analysis the E-M wave propagation characteristics using FDTD method. The influences of the isolating switch and difference receive degree on the propagation characteristics of E-M wave with comparison of isolating switch close and cut are examined in this paper. As a result, this study identified that the crest value of received signal is decrease but the whole energy is little change as the excite source becomes more distant. The energy reflection and dispersion in isolating switch fracture resulted in a decrease in the crest value and energy.