Insulation enhancement with heat-shrinkable components

The basic performance requirements for heat-shrinkable components and the compounding and processing techniques that are used to meet these requirements are covered. The emphasis is on the electrical, mechanical, and environmental protection features of components for low-voltage (up to 1 kV) applications. The aim is to provide a fundamental understanding of the capabilities and applications of heat-shrinkable components for insulation enhancement and environmental protection of electrical systems. Cross-linking, polymer selection, compounding, manufacturing, sealants, installation, and product configurations are discussed     

Insulation enhancement with heat-shrinkable components. I. Mediumvoltage

For pt.I see ibid., vol.7, no.2, p.33 et seq. (1991). Heat-shrinkable components that enhance the insulation performance of installed, medium-voltage electrical systems are described. The concept of insulation enhancement is explained, and some of its applications are examined. Materials selection and compounding are discussed, particularly as regards the prevention of tracking and wetting. The manufacture of sheet and tape products is briefly described. Design considerations are discussed, and specification guidelines are briefly considered     

超导电缆绝缘及其材料性能

在26篇文献的基础上综述了超导电缆本体及终端结构和绝缘特点。分析了不同绝缘结构的特点及主要绝缘材料常温和低温条件下的电气及机械性能。固体绝缘在低温下具有更优异的电气性能,但机械性能下降。EPR绝缘在液氮低温下的机械性能优于同条件下PE及XLPE的性能。液氮浸渍复合绝缘结构较易产生局部放电,纤维基绝缘材料的耐局部放电性能比薄膜材料差。提高液氮浸渍复合绝缘中液氮的压力可提高绝缘层局部放电的起始放电电压。     

A study of electric stress enhancement. Part 1. Implication in power cable design

The increase in electric stress due to a surface protrusion at the interface between a semiconductive shield and a polymer insulation layer in power cables can lead to localized electron injection into the polymer insulation and result in undesired material degradation. This paper reports the analyses of electric stress enhancement of surface protrusions in several commonly encountered medium- and high-voltage power cable configurations. First, a brief review of the electric stress enhancement theories is presented. Then evaluations using these theories for various power cable configurations are made, and it is shown that theories considering a hyperboloidal protrusion will exhibit more realistic stress enhancement results than the cases based on a spheroidal protrusion. Further examination reveals that, besides the sharpness of a protrusion, thickness of the insulation medium also plays a governing role in the stress enhancement at the interfaces between different dielectric media. Contrary to the conventional wisdom, it is a surprise to observe that a thicker insulation can actually cause higher stress enhancement at a protrusion tip, under a given applied voltage. Because of this, a flatter surface protrusion at a higher voltage setting, which usually has thicker insulation, can result in earlier degradation than a sharper protrusion at a lower voltage, even though sharper extrusions are expected to have higher stress enhancement. As a result, thicker insulation may not always be advantageous in the power cable design for higher voltage applications.     

一种高压电缆-架空线混合线路智能重合闸方案

提出了一种基于双端故障信息的高压混合线路智能重合闸方案,利用输电线路首末端电压、电流工频量分段递推,通过搜索两端线路沿线电压曲线交点来确定故障点位置,进而确定重合闸动作逻辑;讨论了架空线和电缆接头处发生故障的处理方法,提出了伪根问题的解决方案.仿真结果表明该方案精度高,不要求线路两端数据同步,不受故障点过渡电阻、伪根、混合线路多分段的影响,重合闸动作正确.     

Fault location scheme for combined overhead line with underground power cable

This paper presents a fault location scheme for transmission systems consisting of an overhead line combined with an underground power cable. The algorithm requires phasor measurements data from one end of the transmission line and the synchronized measurements at the most far end of the power cable. Fault location is derived using distributed line model, modal transformation theory and Discrete Fourier Transform. The technique can be used on-line or off-line using the data stored in the digital fault recording apparatuses. The proposed scheme has the ability to locate the fault whether it is in the overhead line or in the underground power cable. In addition to, the proposed scheme gives an accurate estimation of the fault resistance at fault location. Extensive simulation studies carried out using MATLAB show that the proposed scheme provides a high accuracy in fault location under various fault conditions.     

基于鲁棒无源控制的增强风电接入下电力系统稳定性研究

大规模风电的接入对电力系统稳定性带来了巨大挑战。双馈感应发电机(Doubly-Fed Induction Generator,DFIG)受风速强随机、建模不确定性的影响,经典比例-积分-微分(Proportional-Integral-Derivative, PID)控制难以获得令人满意的控制效果。提出了一种新型鲁棒无源控制(Robust Passive Control, RPC)以提高接入DFIG的电力系统稳定性。首先将发电机非线性、参数不确定性、未建模动态和风速随机性等效聚合为一个扰动,并由非线性扩展状态观测器(Extended State Observer, ESO)进行实时快速估计。随后,通过RPC对扰动估计进行在线完全补偿。同时,通过输出反馈对闭环系统能量进行重塑,从而注入较大的系统阻尼来改善DFIG在电力系统各种运行条件下的控制性能与暂态响应特性。最后,基于阶跃风速、机端电压跌落、区域间振荡以及发电机参数不确定性四个算例进行了仿真研究。仿真结果验证了RPC在各种工况下的有效性和鲁棒性。     

中央一号文件再次燃亮农网电缆市场

2010年1月31日发布了今年中央一号文件《中共中央、国务院关于加大统筹城乡发展力度进一步夯实农业农村发展基础的若干意见》,提出要“加强农村水电路气房建设抓紧实施新一轮农村电网改造升级工程,提升农网供电可靠性和供电能力”。电线电缆业内人士认为,这意味着,今年农网用电缆市场将再次火爆起来。     

带有长电缆的永磁同步电机无传感器速度控制

在采油过程中,潜油泵需要拖拽长功率电缆工作在500～2000 m的井下,由于电机的阻抗与动力电缆阻抗匹配问题会在电机端产生高于直流母线电压两倍的过压,而且井下工作环境复杂,电磁干扰严重,不适合安装位置传感器等精密器件.为了解决这些问题,并满足低速大扭矩工况的要求,提出了一种用于潜油泵的永磁同步电动机无传感器控制方法.设...     

挤出铝管式电力线光缆的探讨

介绍了挤出铝管式电力线光缆,其中光纤被直接放入一根挤出的铝管中而组成一个光纤单元,它不但可以用来制造OPGW、OPPC等架空光缆,而且也可以用来制造地下光缆和海底光缆。文章描述了这种光缆的特点,并报道了按照IEC60794和IEEE1138等标准进行的型式试验、耐腐蚀试验以及传递到支撑结构上的机械张力测试情况试验,结果表明,这种新式光缆符合国际标准,不仅保留了传统OPGW的光学机械、电气特性,而且其抗化学腐蚀、抗雷击和减缓机械张力等性能均有所提高。     

新型平行集束架空绝缘电缆的制造及应用

平行集束架空绝缘电缆是目前农网改造中最新推广使用的一种新产品 ,本文详细介绍了该种电缆的使用特点 ,并就其效益性作了阐述 ,同时对其标准的起草依据、生产工艺要点及使用情况也作了详细的说明。     

低通道依赖的变电站动力电缆漏电流监测方法

为缓解变电站动力电缆漏电状态判断算法对理想通信条件的高度依赖,提出了一种低通道依赖的变电站动力电缆漏电流监测方法。首先,在监测信号同步计算中对传统的参考相量法进行改进,以电源侧为相位差计算的参考基准,消除了负荷波动对信号同步计算的影响。然后,提出基于电流差动原理的复合漏电流判据,以解决系统在未采集到对比基准时的电缆漏电状态判断问题。同时,针对变电站实际运行中漏电流监测系统可能出现的非理想通信情况,建立了与之相匹配的不同漏电判断模式及相应的判断方法,实现了在信息不全的情况下动力电缆漏电状态的正常监测。最后,通过仿真及江苏某500 kV变电站实际数据对所提方法的有效性与优越性进行验证。结果表明,该方法能够在不同通信条件下灵活切换漏电判断模式,显著提高了对漏电状态判断的准确性与可靠性。     

Partial discharge. XXII. High frequency attenuation in shieldedsolid dielectric power cable and implications thereof for PD location

PD testing and location is an essential part of factory testing of shielded solid dielectric power cable. The accuracy with which a PD source can be located is limited by high frequency attenuation of PD pulses as they propagate through the cable     

Application of arithmetic coding for electric power disturbance data compression with wavelet packet enhancement

In this paper, an application of wavelet packet-enhanced arithmetic coding to compress the electric power disturbance data is proposed. In the proposed method, the wavelet packet is first applied in anticipation that the disturbance signal can be optimally decomposed into higher frequency components and lower frequency ones on a best wavelet basis. Then, the arithmetic coding approach is utilized to reduce the redundancy of data encoding, thereby lowering down the cost related with data storage and transmission. This integrated method has been tested on different scenarios and the results are compared with other published techniques.     

Damping enhancement of multimachine power system using adaptive generator control system with neural networks

The authors proposed a nonlinear adaptive generator control system with neutral networks for improving damping of power systems, and showed its effectiveness in a one-machine infinite bus test power system in a previous paper. The proposed neurocontrol system adaptively generates appropriate supplementary control signals to the conventional controllers such as the automatic voltage regulator and speed governor so as to enhance transient stability and damping of the power system. In this paper, the applicability of the proposed neurocontrol system to multimachine power systems is discussed. Digital time simulations are carried out for a 4-machine test power system, where one or several synchronous generators is equipped with the neurocontrol system. As a result, also in the multimachine power system, the proposed adaptive neurocontrol systems improve the system damping effectively and they work adaptively against the wide changes of the operating conditions and the network configuration.     

电气化交通和城市电网协同韧性提升方法综述

随着电气化交通技术的发展,电气化交通系统与城市电网的相互影响已不容忽视.本文首先从城市电网的韧性视角出发,总结了电气化交通系统与城市电网间的互动方式与耦合技术.接着,从城市电网长期韧性规划、灾前调整预防、灾中应急响应、灾后持续供电四个角度,阐述了电气化交通系统提升城市电网韧性的机制.最后,展望了碳达峰、碳中和政策影响下...     

High frequency properties of shielded power cable. Part 2: sources of error in measuring shield dielectric properties

This paper provides a theoretical context for the types of errors that are likely to occur during the measurement of high frequency cable shield properties. The paper considers a RC dielectric system as it relates to measuring the dielectric properties of cable shield materials.     

A new parallel ZVS converter with less power switches and low current stress components

A new direct current (DC)/DC converter with parallel circuits is presented for medium voltage and power applications. There are five pulse‐width modulation circuits in the proposed converter to reduce current stress at low voltage side for high output current applications. These five circuits share the same power switches in order to reduce switch counts. To reduce the converter size, conduction loss, and voltage stress of power semiconductors, the series connections of power metal‐oxide‐semiconductor field‐effect transistor (MOSFET) with high switching frequency instead of insulated gate bipolar transistor (IGBT) with low switching frequency are adopted. Thus, the voltage stress of MOSFETs is clamped at half of input voltage. The switched capacitor circuit is adopted to balance input split capacitor voltages. Asymmetric pulse‐width modulation scheme is adopted to generate the necessary switching signals of MOSFETs and regulate output voltage. Based on the resonant behavior at the transition interval of power switches, all MOSFETs are turned on under zero voltage switching from 50% load to 100% load. The circuit configuration, operation principle, converter performance, and design example are discussed in detail. Finally, experimental verifications with a 1.92 kW prototype are provided to verify the performance of the proposed converter. Copyright © 2015 John Wiley & Sons, Ltd.