Introduction to School of Environmental Science and Engineering of North China Electric Power University

Along with the fast development of national economy, environmental issues have become more and more prominent. China has promulgated a series of policies of energy-saving and emission-reduction to

Reduction of electric field strength by two species of trees under power transmission lines

Electrical pollution is a worldwide concern,because it is potentially harmful to human health.Trees not only play a significant role in moderating the climate,but also can be used as shields against electrical pollution.Shielding effects on the electric field strength under transmission lines by two tree species,Populus alba and Larix gmelinii,were examined in this study.The electrical resistivity at different heights of trees was measured using a PiCUS sonic tomograph,which can image the electrical impedance for trees.The electric field strength around the trees was measured with an elf field strength measurement system,HI-3604,and combined with tree resistivity to develop a model for calculating the electric field intensity around trees using the finite element method.In addition,the feasibility of the finite element method was confirmed by comparing the calculated results and experimental data.The results showed that the trees did reduce the electric field strength.The electric field intensity was reduced by 95.6%,and P.alba was better than L.gmelinii at shielding.

Electrical bearing failures in electric vehicles

In modern electric equipment,especially electric vehicles,inverter control systems can lead to complex shaft voltages and bearing currents.Within an electric motor,many parts have electrical failure problems,and among which bearings are the most sensitive and vulnerable components.In recent years,electrical failures in bearing have been frequently reported in electric vehicles,and the electrical failure of bearings has become a key issue that restricts the lifetime of all‐electric motor‐based power systems in a broader sense.The purpose of this review is to provide a comprehensive overview of the bearing premature failure in the mechanical systems exposed in an electrical environment represented by electric vehicles.The electrical environments in which bearing works including the different components and the origins of the shaft voltages and bearing currents,as well as the typical modes of electrical bearing failure including various topographical damages and lubrication failures,have been discussed.The fundamental influence mechanisms of voltage/current on the friction/lubrication properties have been summarized and analyzed,and corresponding countermeasures have been proposed.Finally,a brief introduction to the key technical flaws in the current researches will be made and the future outlook of frontier directions will be discussed.

Techno-economic analysis of the adoption of electric vehicles

Significant advances in battery technology are creating a viable marketspace for battery powered passenger vehicles.Climate change and concerns over reliable supplies of hydrocarbons are aiding in the focus on electric vehicles.Consumers can be influenced by marketing and emotion resulting in behaviors that may not be in line with their stated objectives.Although sales of electric vehicles are accelerating,it may not be clear that purchasing an electric vehicle is advantageous from an economic or environmental perspective.A technoeconomic analysis of electric vehicles comparing them against hybrids,gasoline and diesel vehicles is presented.The results show that the complexity of electrical power supply,infrastructure requirements and full life cycle concerns show that electric vehicles have a place in the future but that ongoing improvements will be required for them to be clearly the best choice for a given situation.