Digital simulation studies on long transmission line protection based on balance of energy

The protection based balance of energy is a new technique specially proposed for long transmission lines. This technique depends upon the calculation of net energy into the transmission line by two independent methods and comparing them to indicate healthy and faulty conditions. In order to study the performance and feasibility of the protection based on balance of energy, the new protection has been extensively tested by using EMTP on a long transmission line with various configurations and operating conditions (including single pole line, double circuit lines and two phase operation). The results calculated by EMTP show that under any condition of a power system, the proposed technique has excellent performance,the viability even for high resistance ground faults and a short operation time.

A DIGITAL SIMULATION TECHNIQUE FOR DRYDEN ATMOSPHERIC TURBULENCE MODEL

Dryden model is usually used in studying the response of flight vehicle to atmospheric turbulence.For a modern flight simulator,it is necessary to generate random winds ( in Dryden model or sometimesothers) with a digital computer.In this paper,a theoretically strict new method to meet this purpose isproposed.By this method,we can acquire a three-dimensional atmospheric turbulence which containsthree components of wind velocity and three components of wind velocity gradient.The reliability of thismethod is checked by comparing the obtained autocorrelation value with the theoretical one.A numericalexample has shown a satisfactory result.Finally,some proposals about how to use this mathematicalmodel in flight simulator are given.

Framework for Artificial Intelligence Analysis in Large-scale Power Grids Based on Digital Simulation

The planning,design,operation,control and scientific research of power systems all require a variety of simulation analysis.Thus power grid simulation analysis is a fundamental supporting technology of large-scale power grids.In power grid simulation analysis,in addition to simulation calculations,there are many links for analysis and decision-making,relying on specialists.The introduction of advanced artificial intelligence technology provides a new method to improve the efficiency and accuracy of power grid simulation analysis.Nevertheless,the research of the related artificial intelligence technologies face a great deal of new challenges due to the complexity of the largescale power grid simulation data,including massive volumes,high dimensionality,strong coupling and complex correlations.Also a great deal of knowledge and experience need to be integrated in the process of analysis.In order to deal with these challenges,based on the existing works,this paper focuses on the core scientific problem of artificial intelligence analysis and decision making related to the massive simulation results of large-scale power grids,and proposes an artificial intelligence analysis method framework for large-scale power grids based on digital simulation,which includes the power grid simulation analysis knowledge model with application method,the power grid simulation knowledge mining method and the artificial intelligence models with transfer learning ability of diversified grids as well as analyzing and calculation adjusting for largescale power grid simulation results,etc.This work is expected to open up a new technical approach for large-scale power grid simulation analysis and provide strong technical support for the safe and stable operation of large-scale power grids.

A Portable Multi-functional Real-time Digital Simulator Dedicated to Protective Relay Testing

The paper intfoduces a PC-DSP based real-time digital simulator which is portable in size and aimed at the closed-loop testing of various types of protective relays for their design and application. The simulator can be widely used in not only concerning utilities but also manufacturers and research / certification institutes because of its many functions. The hardware architecture and software implementation of the simulator are described. The main features and functions of the simulator are also

Design on the Prestressed Concrete Frame Beam-column

A bidirectional ribbed concrete beam slab structure was widly adopted for the upper space of industrial buildings.To maintain ample space and minimize the presence of conventional columns,a bidirectional prestressed concrete beam is often employed.The intersection node of the prestressed concrete frame beam column was characterized by a high density of steel reinforcement,significant structural loads,and complex construction requirements.To ensure the quality,safety,and progress of prestressed frame beamcolumn intersection nodes during construction,this article proposed a new technology for constructing such nodes,which includes setting the tensioning and haunching ends of nodes at different positions,using ABAQUS finite element software to optimize the design of cross-sectional dimensions,conducting stress analysis simulations.

Microscale crack propagation in shale samples using focused ion beam scanning electron microscopy and three-dimensional numerical modeling

Reliable prediction of the shale fracturing process is a challenging problem in exploiting deep shale oil and gas resources.Complex fracture networks need to be artificially created to employ deep shale oil and gas reserves.Randomly distributed minerals and heterogeneities in shales significantly affect mechanical properties and fracturing behaviors in oil and gas exploitation.Describing the actual microstructure and associated heterogeneities in shales constitutes a significant challenge.The RFPA3D(rock failure process analysis parallel computing program)-based modeling approach is a promising numerical technique due to its unique capability to simulate the fracturing behavior of rocks.To improve traditional numerical technology and study crack propagation in shale on the microscopic scale,a combination of high-precision internal structure detection technology with the RFPA^(3D) numerical simulation method was developed to construct a real mineral structure-based modeling method.First,an improved digital image processing technique was developed to incorporate actual shale microstructures(focused ion beam scanning electron microscopy was used to capture shale microstructure images that reflect the distri-butions of different minerals)into the numerical model.Second,the effect of mineral inhomogeneity was considered by integrating the mineral statistical model obtained from the mineral nanoindentation experiments into the numerical model.By simulating a shale numerical model in which pyrite particles are wrapped by organic matter,the effects of shale microstructure and applied stress state on microcrack behavior and mechanical properties were investigated and analyzed.In this study,the effect of pyrite particles on fracture propagation was systematically analyzed and summarized for the first time.The results indicate that the distribution of minerals and initial defects dominated the fracture evolution and the failure mode.Cracks are generally initiated and propagated along the boundaries of hard mineral particles such as pyrite or in soft minerals such as organic matter.Locations with collections of hard minerals are more likely to produce complex fractures.This study provides a valuable method for un-derstanding the microfracture behavior of shales.

Digital/Analog Simulation Platform for Distributed Power Flow Controller Based on ADPSS and dSPACE

Distributed power flow controller,which is among the most powerful distributed flexible transmission equipments,is still only in the stage of the oretical research and digital simulation.In order to promote the engineering demonstration of a distributed power flow controller,it is urgent to establish a digital/analog simulation platform that supports closed-loop real-time simulation of a distributed power flow controller.In this paper,the electromagnetic transient model of a distributed power flow controller is established on ADPSS(advanced digital power system simulator).The rapid control prototype realized by dSPACE is connected to ADPSS to form a digital/analog simulation platform for a distributed power flow controller.Through a voltage control and power flow control simulation of the test system with a distributed power flow controller,the correctness and effectiveness of the constructed simulation platform are verified,which provides a new way for the verification of the new theory of a distributed power flow controller.

Modeling methodology and fault simulation of distribution networks integrated with inverter-based DG

The increasing penetration of inverter-based distributed generations(DGs)significantly affects the fault characteristics of distribution networks.Fault analysis is a keystone for suitable protection scheme design.This paper presents the modelling methodology for distribution networks with inverter-based DGs and performs fault simulation based on the model.Firstly,a single inverter-based DG model based on the cascaded control structure is developed.Secondly,a simulation model of distribution network with two inverter-based DGs is established.Then,different fault simulations are performed based on the Real Time Digital Simulator(RTDS).Theoretical analyses are conducted to justify the simulation results,including the equivalent circuit of distribution networks with inverter-based DGs and the solution method for loop currents.

Control and protection strategy for MMC MTDC system under converter-side AC fault during converter blocking failure

This paper investigates a control and protection strategy for a four-terminal modular multilevel converter(MMC)based high-voltage direct current(HVDC)system under a converter-side AC fault.Based on the system operating condition,a control and protection strategy against the fault with normal blocking of the converter is proposed.In practical,applications encountering such a fault,the MMC at the fault side may experience different conditions of blocking failure.The blocking failures may occur on:①the whole converter;②one converter arm;③one sub-module(SM)/several SMs of one converter arm;④other conditions.The phenomenon of the multi-terminal HVDC(MTDC)system following the fault is analyzed under the first three conditions with real-time simulations using the real-time digital simulator(RTDS).Based on the impact of different conditions on the MTDC system,the necessity of utilizing special control and protection is discussed.A special control and protection strategy is proposed for emergency conditions,and its effectiveness is verified by real-time simulation results.

Exploring expressive and functional capacities of knitted textiles exposed to wind influence

This study explores the design possibilities with knitted architectural textiles subjected to wind.The purpose is to investigate how such textiles could be applied to alter the usual static expression of exterior architectural and urban elements,such as facades and windbreaks.The design investigations were made on a manual knitting machine and on a CNC(computer numerically controlled)flat knitting machine.Four knitting techniques-tuck stitch,hanging stitches,false lace,and drop stitch-were explored based on their ability to create a three-dimensional effect on the surface level as well as on an architectural scale.Physical textile samples produced using those four techniques were subjected to controlled action of airflow.Digital experiments were also conducted,to probe the possibilities of digitally simulating textile behaviours in wind.The results indicate that especially the drop stitch technique exhibits interesting potentials.The variations in the drop stitch pattern generate both an aesthetic effect of volumetric expression of the textile architectural surface and seem beneficial in terms of wind speed reduction.Thus,these types of knitted textiles could be applied to design architecture that are efficient in terms of improving the aesthetic user experience and comfort in windy urban areas.

A novel hybrid cybersecurity scheme against false data injection attacks in automated power systems

The conventional power systems are evolving as smart grids.In recent times cyberattacks on smart grids have been increasing.Among different attacks,False Data Injection(FDI)is considered as an emerging threat that has significant impact.By exploiting the vulnerabilities of IEC 61850 Generic Object-Oriented Substation Events(GOOSE)and Sam-pled Values(SV)attackers can launch different FDI attacks.In this paper,a real-time set up capable of simulating FDI on GOOSE and SV protocols is developed to evaluate the impact of such attacks on power grid.IEC 62351 stipulates cybersecurity guidelines for GOOSE and SV,but only at communication or Information Technology(IT)level.Hence there is a need to develop a holistic security both at IT and Operation Technology(OT)level.In this regard,a novel sequence content resolver-based hybrid security scheme suitable to tackle FDI attacks on GOOSE and SV is proposed.Furthermore,the computational performance of the proposed hybrid security scheme is presented to demonstrate its applicability to the time critical GOOSE and SV protocols.