Research on Conducted Disturbance to Secondary Cable Caused by Disconnector Switching Operation

The disconnector switching operation in GIS not only generates very fast transient overvoltage (VFTO) in primary equipment, but also couples to the secondary system, which affects normal operation of the secondary equipment. In this study, aiming at the conducted disturbance caused by the disconnector switching operation of the 1,000-kV UHV GIS test circuit on the secondary cable, a broadband equivalent circuit model of the potential transformer and the grounding grid is proposed based on the vector fitting method and the impedance synthesis method, and the accuracy of the model is tested. On the basis of this model, the conducted disturbance voltage of the secondary cable core is obtained by combining the measured typical disturbance source waveform. The research results of the influencing factors of conducted disturbance show that the amplitude of the disturbance voltage generated by the capacitive conduction is higher than that generated by the resistive conduction, but the main frequency of the resistive conducted disturbance voltage is higher. The amplitude of the conducted disturbance voltage will decrease with the increase of the length of the cable and the length of the grounding wire. The single-ended grounding of the secondary cable shield at the GIS side will cause serious disturbance voltage. The research results of this study will be beneficial to the protection of secondary cable electromagnetic disturbance in the intelligent substation and have reference significance for the implementation of secondary equipment protection measures in the intelligent substation.

Simulated and Experimental Analysis of a Log Crane With Conventional and Direct Driven Hydraulics

The present paper compares the efficiency and dynamic behavior of a log crane while using two alternative transmissions. Firstly, the conventional mobile hydraulic valves with a load-sensing pump is used, and secondly, a novel electric-hydraulic energy converter and a direct driven hydraulic actuator is used. By applying lumped parameter models and the theory of centralized pressure, the hydraulic system models are constructed in MATLAB & Simulink environment. MathWorks Simscape Multibody is used in modeling of the multi-body system of the crane. The results of the simulation models are compared with those measured in the laboratory. Based on the verification results, such modes of operation in which the agreement between simulated results is the closest are selected for further investigation. The effectiveness of the system equipped with an electro-hydraulic converter is compared with that of the conventional system with a load sensing pump. Detailed models for components are given in the paper, and the results are discussed based on what obtained through simulation and experiments. The electric-hydraulic converter used in direct driven circuit is a novel prototype developed at LUT University. It has good power stiffness, and it provides good torque properties in a wide RPM area. The prototype is used in operating the lift or tilt cylinder, which is altered by using fast switching valves. The actual test circuit does not have electric storage. The ability of the converter to recover potential energy from the lifting system inertia is approximated in the efficiency comparisons.

RF Pogo-Pin Probe Card Design Aimed at Automated Millimeter-Wave Multi-Port Integrated-Circuit Testing

A prototype RF probe card is assembled to test the feasibility of Pogo-pins as robust probe tips for the automized testing of multiple-port millimeter-wave circuits. A custom-made ceramic housing machined from a low-loss dielectric holds an array of 157 Pogo-pins, each with 2.9 mm-length in fixed positions. The ceramic housing is then mounted onto a probe-card PCB for power-loss measurements on two signal-ground Pogo-pin connections arbitrarily selected from the array. The probing results on a test circuit with a simple thru-line indicate a successful power transfer with a small insertion loss of less than 0.5 dB per single Pogo-pin connection up to 25 GHz. A new probe card design using shorter Pogo-pins is being prepared to extend the operation frequency to beyond 40 GHz.

Verification Measurement of Laboratory Test Equipment for Evaluation of Technical Properties of Automotive Oil Filters

By simulating the operating conditions, it is possible to verify and evaluate the technical properties of motor vehicle oil filters and the functionality of the designed equipment. Contaminated engine oil from operation was used with MANN W950/26 oil filter and a CNH Industrial 2992242 oil filter in the test circuit. Before use, the level of engine oil contamination in the test circuit was determined by evaluating the physicochemical properties. The laboratory test equipment also allows monitoring the technical life of oil filters, with variously contaminated engine oil, with the possibility of extending engine oil change service intervals depending on changes in the physicochemical properties of engine oil and filter efficiency. These laboratory tests can be performed in parallel in two hydraulic circuits, which can significantly reduce the testing time of the filter capabilities of oil filters, without the risk of engine damage, provided that the tests were performed under operating conditions. The results of the evaluation of the filtration capacity of oil filters can be used in the design of new filter materials, but also with a suitably determined methodology of oil filter replacement and engine oil change interval, it is possible to extend replacement intervals, which has a significant benefit not only from an economic but also ecological point of view. The result of the measurements is the confirmation of the functionality of the device with the possibility of simulating the operating conditions, at different degrees of oil contamination, at different operating temperatures and using different oil filters.

Innovation of Pump as Turbine According to Calculation Model for Francis Turbine Design

The effective utilization of micro hydropower sources is often realized through the use of pumps as turbines (PAT). The efficiency of PAT is about the same as that of the original pump. A further increase in efficiency and power output can be achieved by modifying the parts interacting with the flow, especially the impeller and the adjacent volute casing and draft tube. This paper presents a user-friendly calculation model of Francis turbine design and its application for PAT geometry modification. Two different modifications of a single-stage radial centrifugal pump were designed according to this model. The first modification (Turbine) consisted of a complete revision of the impeller geometry, volute casing and draft tube, which corresponded to a conventional Francis turbine. The second modification (Hybrid) was based on altered calculation model and consisted of a modification of only the impeller, which can be used in the original volute casing. Both modifications were tested on hydraulic test circuit at different heads. A comparison of the results of the Hybrid and the Turbine modification with the unmodified machine (Original) proved an increase in overall efficiency by 10%. Both modifications provided a higher flow rate and torque. This resulted in an overall power output increase—an increase of approximately 25% and 40% due to the Turbine and Hybrid modifications, respectively.

Influence of the weight coefficients of measurements on the consistency of the assessment and calculation results of the power supply system steady-state operation conditions

The aim of this work is to develop an improved procedure for assessing the state of power supply systems based on adjusting the weight coefficients of measurements. To this end, non-linear optimisation methods were used. The control equations and the solution of the simultaneous linear equations were performed using the Crout method. The results of the calculation of the electrical power steady-state mode were considered as a reference. The lower the difference between the evaluation and steady-state calculation results, the higher the accuracy of the overall state assessment procedure. The problem of correcting the weight factors is set and solved as a nonlinear optimisation problem, where the optimisation parameters are taken as the dispersion of the measurements. The objective function was formulated as follows: to minimise the measurement evaluation dispersions that are part of a single control equation by maximising the active power measurements dispersion in the swing bus of the power supply system. In this study, limitations in the form of equation and inequality are monitored. The problem of optimising the dispersions is solved after the first iteration of the state assessment; starting with the second iteration, the state assessment is performed with new measurement weight factors. The calculations were performed on a 6-node test circuit. The control equations are drawn from the current measurements. The measurements data on the selected control equation of the test circuit are used to calculate the target function. The accuracy of the dispersions redistribution and their extreme values are controlled by the limitations. The results showed that, when adjusting the dispersion of measurements, the power assessments at all nodes are closer to the steady-state mode calculation results.