浅析10kV配电线路设计技术要点

在电力工程中,配电线路的设计直接影响着供电企业的运行,本文主要探讨在电力工程中,针对10kV配电线路的设计技术要点。     

Infinite-dimensional VARs and factor models

This paper proposes a novel approach for dealing with the ‘curse of dimensionality’ in the case of infinite-dimensional vector autoregressive (IVAR) models. It is assumed that each unit or variable in the IVAR is related to a small number of neighbors and a large number of non-neighbors. The neighborhood effects are fixed and do not change with the number of units (N), but the coefficients of non-neighboring units are restricted to vanish in the limit as N tends to infinity. Problems of estimation and inference in a stationary IVAR model with an unknown number of unobserved common factors are investigated. A cross-section augmented least-squares (CALS) estimator is proposed and its asymptotic distribution is derived. Satisfactory small-sample properties are documented by Monte Carlo experiments. An empirical illustration shows the statistical significance of dynamic spillover effects in modeling of US real house prices across the neighboring states.     

10kV配电线路保护的整定计算

10kV配电线路结构特点是一致性差,如有的为用户专线,只接带一、二个用户,类似于输电线路;有的呈放射状,几十台甚至上百台变压器T接于同一条线路的各个分支上;有的线路短到几百m,有的线路长到几十km;有的线路属于最末级保护,有的线路上设有开关站或有用户变电所等。     

10kV配电线路接地故障原因及有效预防措施

配电线路是电网的基础设施,其故障发生频率较高并且涉及的原因也比较广泛。文章主要介绍了10 kV配电线路中单相接地的故障类型及发生原因,并阐述了一定的预防措施和处理方法以及新技术和新设备在该方面的应用。     

Who should sell stocks?

Never selling stocks is optimal for investors with a long horizon and a realistic range of preference and market parameters, if relative risk aversion, investment opportunities, proportional transaction costs, and dividend yields are constant. Such investors should buy stocks when their portfolio weight is too low and otherwise hold them, letting dividends rebalance to cash over time rather than selling. With capital gains taxes, this policy outperforms both static buy‐and‐hold and dynamic rebalancing strategies that account for transaction costs. Selling stocks becomes optimal if either their target weight is low or intermediate consumption is substantial.     

The financial crisis and its impacts on global agriculture

The financial crisis arose in the industrial countries, but has affected developing countries through higher interest rates, sharp changes in commodity prices, and reductions in investment, trade, migration, and remittances. For most low‐income countries, shocks that affect food prices or wage rates for unskilled workers seem likely to have the biggest impact on poverty, with the declines in key food prices associated with the crisis helping to reduce poverty. Policies to address the crisis must include measures to deal with: financial sector problems; the resulting reductions in aggregate demand; and the particular vulnerabilities of poor people.