用极低频以局放和损耗因数测量来鉴定中压电缆的新成果

引　言本文介绍采用一个 0 .1周正弦波极低频电源诊断系统进行现场试验的真实结果。这一采用新技术的新型诊断工具为地下电缆系统和电网的用户提供高效的测量步骤以判断老化特性、更换的需要程度以及更精确的投资规划预测。此外 ,远在击穿发生前这个方法提供了适时更换和对初期故障的预测。普遍使用这种诊断工具可以戏剧般地降低拥有者的投资 ,更换、维护和‘停电’的成本 ,同时可以得到较高的系统可靠性和配电的冗余度。以往 ,中压和高压电缆是用直流做试验的。它的好处是现场试验设备重量轻、便携带、使用方便和经济。在引入如聚乙烯、交…     

Comparison of on-line partial discharge detection methods for HV cable joints

The capacitive coupler, acoustic emission (AE) sensor and radio frequency current transducer (RFCT) have been used to detect partial discharge (PD) activity within a 132 kV prefabricated cable joint containing a known defect. Although each of the three methods has been applied individually under different situations, a comprehensive investigation and comparison of these three methods has not yet been made. Results obtained were compared to measurements made using the conventional electrical detection method. The quantification of the capacitive coupler measured signal in mV with a discharge apparent quantity in pC has been investigated and an on-line quantification method proposed. The capacitive coupler has good detection sensitivity and PD location can be realised by studying the time of Right between signals from two sensors. The difference in pulse shape, spectrum and time of flight between an internal discharge and external interference has been investigated. The AE approach has the advantage of being free from electrical interference. However, investigation indicated that AE signals were significantly attenuated within the cable joint. RFCTs were used to detect the discharge current flowing through the cable sheath. Where the detection sensitivity was low, a wavelet de-noising method was applied to process the RFCT signals and proved to tie effective in increasing the measurement signal to noise ratio.     

Partial discharge factory test requirements and in-field partial discharge testing of medium voltage cables

This article presents partial discharge testing of medium voltage cables. Utility engineers are faced with decision on whether to replace some of the older cables in their underground distribution systems. Today, measurement of PD at voltages above 1 Vg on extruded cables more than fifteen years old may not indicate that the cables have developed PD due to in-service aging. Removal of these cables based solely on PD measurements may not be warranted. Failure history of the cable, in conjunction with an analysis of the PD site, should be part of the utility engineer's decision-making process.     

XLPE电缆及接头局部放电的超高频测量与分析

超高频的局部放电测量是目前国外电力设备绝缘检测研究的焦点问题之一。本文建立了一套超高频局部放电的测量系统,设计了XLPE电力电缆及其接头局部放电超高频测量的电容耦合传感器,分析了传感器的等效电路,测量了其频率响应,对电缆以及接头中的实际放电进行了测量分析。     

Partial discharge on-line monitoring for HV cable systems using electro-optic modulators

A technique for the remote inspection and monitoring of partial discharge (PD) activity using an optical network is described. The network uses a LiNbO/sub 3/, modulator to modulate the intensity of the transmitted laser light approximately proportional to the voltage applied across the modulator. The laser light is transmitted along an optical fibre and measured remotely by a high-speed optical receiver. A capacitive coupler has been used to detect partial discharge activity and act as the modulator's input voltage source. The electro-optic modulator is passive and does not require a power supply at the site of the PD detection sensor. The system has the additional advantages of being immune to electromagnetic interference, having very little signal transmission attenuation, with good sensitivity, compact size, as well as being convenient to use and safe. Both simulation experiments and practical PD tests on two cable systems have indicated that the optical system provides a feasible remote PD monitoring technique for high voltage cable systems.     

Single-phase voltage regulators and three-phase systems

Voltage regulators are applied on distribution systems to control the voltage delivered to customers within acceptable industry standards. Concerns about the quality of electric power delivered to customers by electric utility companies have raised the level of awareness of high- and low-voltage conditions at customer facilities. Normally occurring voltage drops through lines and transformers vary with the load level on the system. Voltage regulators, when properly applied, can compensate for these voltage drops and keep customer voltage within proper limits. Single-phase voltage regulators can be applied on three-phase systems in a variety of ways, including grounded-wye, open-wye, closed-delta, and open-delta. The capabilities of the regulator systems are affected by the system design. In this article, the authors review the characteristics of the closed-delta and wye applications, and discuss the advantages and disadvantages of each application scheme. The impact of the regulator connection on overcurrent protection is also reviewed     

A new approach to partial discharge testing of HV cable systems

This paper describes the application of an innovative partial discharge (PD) detection and analysis approach to the diagnosis of HV polymeric cable systems. The results of PD measurements performed off-line on cable systems, rated from 220 to 400 kV just after laying or after some time in operation, are presented. PD generating defect identification and location are discussed, also in relation to forensic observations.     

Medium voltage cable defects revealed by off-line partial discharge testing at power frequency

This paper describes typical cable defects uncovered while testing over 9,000 km of medium voltage XLPE insulated cables. After a brief review of the testing method, the procedure that led to the identification, localization, and characterization of typical defects found in operating cables is described. The paper also discusses the "conversion" of water trees (WT) to electrical trees (ET) which are associated with partial discharge (PD) activity in the context of laboratory research. Based on actual service performance of cables, several cases in which ETs associated with WTs did not lead to cable failure even after several years of service in very harsh operating environments are cited.     

高压电缆接头局部放电声光联合检测系统设计与实现

针对传统局部放电检测系统成本高、易受电磁干扰、检测距离和准确性有限等缺点,基于超声与紫外两种非电气局部放电检测技术,利用超声传感技术实现近端局部放电信号的高灵敏、动态和精确捕获,利用空气中紫外光比超声信号衰减慢弥补超声的检测距离极限,综合实现复杂电磁干扰环境下远距离、非接触、信息可靠和低成本的高压电缆接头处局部放电状态...     

Development of a method of partial discharge detection inextra-high voltage cross-linked polyethylene insulated cable lines

Deterioration in the insulation performance of extra-high voltage XLPE (cross-linked polyethylene) cables is believed to be attributable to the deterioration caused by partial discharges. After using an XLPE cable to investigate the behavior of partial discharges under various adverse conditions, the authors succeeded in developing a highly sensitive novel method of measuring partial discharge in XLPE cable lines. Partial discharges in a 275 kV XLPE cable live line have been measured using this method. As a result, a detection sensitivity of 1 pC has been achieved     

Technical trends in medium voltage URD cable specifications

It has been more than thirty years since high molecular weight polyethylene (HMWPE) was first introduced as a commercial insulating material for medium voltage (15-35 kV) underground residential distribution (URD) cables. That began a dramatic expansion of utility electrical service that has led to the installation of several million miles of URD cables by over 3,000 utility companies across America. When early cables began failing prematurely, the industry was challenged to diagnose the causes and find corrective solutions that would give utilities the confidence to continue their commitment to underground cable. The past 25 years have been a story of constant technical improvements, increasingly tighter industry specifications and positive advancements in URD cable life performance. This paper discusses the significant technical changes that have taken place during this period and their impact on cable performance. The results of a 1983-1993 ten-year study of the major technical specification changes of the 25 largest Investor-Owned Electric Utility Companies (IOUs) is also presented. The data illustrate how quickly new cable technology is specified by these leading utilities and provide a clear picture of the key technical trends occurring throughout the utility industry during the 1990s     

Numerical simulation of partial discharge propagation in cable joints using the finite difference time domain method

In this second of a series of three papers, the authors investigate partial discharge (PD) detection and propagation in cable joints. The complex nature of cable joints leads to errors when PD analysis is carried out using conventional equivalent circuits. The authors use the finite difference time domain method to determine the transient electromagnetic fields caused by simulated PD in model cable joints.     

Cost-effective on-line partial discharge of measurements for cables

On-line partial discharge (PD) measurements are an efficient method for detecting certain insulation defects of cables. These include defects in cable joints and terminations, and defects due to mechanical impact. Noninvasive, efficient, and widely applicable, portable on-line PD measurement techniques are strongly favored by the electricity industry. Three on-site PD measurements for cables are described in this article to illustrate how the techniques achieve cost-effective insulation diagnosis to protect the main assets.     

Fundamental aspects of PD patterns of on-line measurements onturbogenerators

This paper discusses partial discharge (PD) measurements performed on turbogenerators using the VHF PD detection technique. With this technique it is possible to perform PD measurements on turbogenerators without interruption of their operation. In addition to PD in any particular phase, the recorded patterns can show crosstalk from other phases and disturbances. The membership of each signal source (phase's own PD pattern, crosstalk, disturbances) to the recorded pattern depends on the selected center frequency. By examination of some typical examples, the relationship between the center frequency and recorded patterns is discussed. Furthermore, PD measurements performed over time on the same generator are studied to discuss possible changes in the spectral responses of particular phases of a turbogenerator. By visual comparison of PD patterns as well as computer-based discrimination tools it was found that several center frequencies are suitable to tune the VHF PD detection technique. However, these center frequencies can change in the course of time for a particular phase of a turbogenerator. As a result, in order to avoid a misjudgment on the insulation condition of turbogenerators, the analysis of on-line recorded PD should not be restricted to just one single center frequency     

The effect of voltage distortion on ageing acceleration ofinsulation systems under partial discharge activity

This paper focuses on the features of harmonic distortion which may affect significantly the reliability of typical ac-power network equipment, such as low-voltage self-healing capacitors used for reactive power and harmonic compensation. Moreover, the effect of high-frequency pulse-like voltage generated by Adjustable Speed Drives (ASD) on electrical machine insulation is also investigated, resorting to life tests carried out on different insulating materials of the standard and “corona resistant” type, at electrical field levels able to incept partial discharges (PD)     

磁悬浮交通用特种中压电缆的结构

上海磁悬浮已于2004年1月以430km／h的速度正式运行,一条30公里长的双轨线路连接着上海浦东国际机场和市区的地铁龙阳路车站,这是高速磁悬浮技术的首次商业应用。上海磁悬浮成功的商业运行有助于推动世界各地的磁悬浮项目,这些项目迄今为止一直处于试验阶段。     

中压电缆终端高频电热老化试验装置的研制及分析

中压电缆终端被广泛应用于柔性交流输电和作为逆变器和电机的连接中,这些电缆终端可能会遭受到高频谐波电压的冲击,从而导致其绝缘迅速失效.本文研制了模拟电网高频谐波电压和工频大电流的电热老化试验装置.首先,通过信号发生器和功率放大器产生低压大电流信号,再通过高频变压器升压获得高频高压;同时通过工频试验变压器产生工频高压,将工...     

欧洲新开发的地下、中压架空的电力电缆

1.低压电缆整个欧洲有一种倾向,那就是不使用EPDM绝缘和PVC护套,而使用经过硅烷交联的TPE-O族塑性体,不过要以得到足够的柔软性为条件。在材料从XLPE向热塑聚合物过渡的过程中,应考虑到成本、再利用以及其他因素。因为需要连续的硫化线,其固化更昂贵。还有一个因素是挤出速度慢     

The excitation of UHF signals by partial discharges in GIS

The fundamental theory of the UHF method for detecting partial discharge (PD) in gas insulated substations (GIS) is presented. The effects of position, size, current amplitude and pulse shape of the PD source on the UHF signal can be predicted using this theory. Excitation of propagating electromagnetic waves by a PD current pulse within the coaxial waveguides formed by GIS components is explained by making use of dyadic Green's functions for the electric fields of propagating modes. Experiments with a coaxial test chamber are used to verify the theoretical predictions, and comparisons are made between measured and simulated UHF signals. Some implications for the UHF measurement of PD are discussed, together with positioning and sensitivity requirements for UHF couplers. A scheme is proposed for standardizing PD measurements made using the UHF technique     

用交流电压进行高压XLPE绝缘电缆线路的现场试验

根据XLPE绝缘电缆用直流电压进行现场试验的经验,要求开发新的方法。现在有一种移动式调频串联揩振装置能够用交流电压进行试验,这意味着适用于塑料绝缘电缆敷设后的试验将有重大突破。配有经由户外户内开关设备而接至电缆线路的连接线,以满足不同用户的要求。