Abstract: Due to the regulation of the electricity market, the reliability of distribution networks becomes more and more important. Network operators are forced to maintain the distribution cable system carefully. Withstand testing after installation or after repair of failures reduces significantly the failure rate during normal operation. This paper describes the evolution of the Very Low Frequency (VLF) testing technology over the past two decades. Since the introduction of the VLF technology not only the technology itself has changed. Because of the large number of systems in operation and the gathered field data/performed researches, also the application has received high attention from the asset management.

Abstract: Cable joint is used to connect different sections of cable because a cable section is limited to a certain length. The design of a cable joint mainly depends on the cable type, the applied voltage and the cores. These factors contribute to the way of how electric field stress is distributed at the cable joint. If there are defects exist within the cable joint insulation material, the electric field at that region is altered. The alteration may cause electrical discharges to occur within the defects if the electric field magnitude is larger than the breakdown strength at the defect sites. Therefore, this paper investigates the electric field distribution in a medium voltage cable joint in the presence of defects. The investigation was done through modelling a medium voltage (MV) cable joint using finite element analysis (FEA) software. Several parameters such as the defect size and location, insulation material dielectric constant and insulation thickness have been studied of their effects on the electric field distribution at the cable joint. The results obtained may be able to help in the designing of cable joint structures which can reduce the electric field stress.

Abstract: Analysis and Measurement Services (AMS) Corporation has been conducting two research projects focused on understanding cable aging and developing cable condition monitoring technologies for nuclear power plants. The goal of the first project is to develop a cable aging management program to correlate the aged condition of a cable with condition monitoring techniques that can identify and locate aging in the cable's polymer material as well as faults that may occur in the conductor. This project involves laboratory experiments using low and medium voltage cable types typically installed in nuclear power plants. The second project is focused on development of an integrated cable condition monitoring system for nuclear facilities. This system integrates a number of cable testing and cable condition monitoring techniques, such as time domain reflectometry (TDR), frequency domain reflectometry (FDR), inductance, capacitance, resistance (LCR), reverse TDR (RTDR), voltage, waveform acquisition, current-to-voltage (IV) for testing of nuclear instrumentation sensors, and insulation resistance (IR). The purpose of the project is to combine all proven technologies into one system to detect and pinpoint problems in cable circuits as well as cable insulation, shield, or jacket material.

Abstract: Recently, the improvement of diagnosis techniques of electric power equipment with increasing of demand for energy and high electric power is necessarily This paper describes that test of very low frequency (VLF) Tanδ performed on cable samples of Medium Voltage (MV) class The paper shows that tanδ measurements using the weibull distribution are properly diagnostic techniques in condition assessment of insulation

Abstract: Cable separation rules to prevent crosstalk between different cable categories are in use for over five decades. The rules have been developed in the analogue era and when equipment was not fulfilling any, or maybe some, electromagnetic interference standard. This has changed but the rules are still in use. The technical rationale is unknown, so simulations and measurements have been performed to understand and interpret crosstalk between various cables, to develop ingredients for a general model that includes sources, coupling and victims. The goal is to eventually find ways to simplify, harmonise and improve these rules.

Abstract: This contribution presents new developments in the field of on-site (E)HV cable testing, in particular testing of long lengths of power cable A modern solution is presented for on-site testing and diagnosis of transmission power cables by means of sinusoidal damped AC voltages With this testing technique on-site voltage testing is performed with additional non-destructive measuring techniques eg partial discharges or dissipation factor measurements To improve the PD detection and particularly the PD location possibilities on long cable lengths an additional range extension measurement system has been developed for PD detection on longer cable lengths This distributed measurement system can be installed at cable accessories to detect PD signals

Abstract: This paper addresses the challenges arising when considering the conversion of an existing low voltage cable infrastructure in distribution networks from AC to DC. It will explore the ageing mechanisms of low AC voltage cable insulation and how could they differ when operated at DC voltages. In a DC environment, the cables may experience lower voltages but higher currents; hence the thermal ageing could be the dominant stress component that may determine the lifetime of DC cables. A model based on a campus distribution network is used to identify possible constraints. Existing AC cables and their characteristics (based on a 6.6 kV distribution network), such as ampacity, temperature-current characteristics, power requirements of the system and simulation results for cables at different loads are investigated. Properties affected by ageing under AC conditions for the existing cables are considered along with constraint-points of the network.

Abstract: Hybrid MV cable networks can be a very complex compound of PILC, XLPE, high number joints, and joints with different kind of weaknesses in different elements of one cable line. Condition based maintenance strategies in such networks require a combination of testing methodologies and differentiated interpretation of test results.

Abstract: Distribution cables rated 22 kV which were submerged under water for more than 45 days due to flash floods in one of the processing industry were assessed using VLF technique in addition to other techniques like insulation resistance and dc voltage withstand test. Special technique used for extraction of water from the cable termination is discussed. The consequences of bad crimping of cable lugs and improper cable terminations on the penetration of water into the cable length are highlighted. The study showed abnormal dielectric losses in the cable insulation as a result of highly polar contaminants in the cable. The precaution to prevent water entry into the cable are suggested in this paper

Abstract: Recently, cabtyre cables are widely used in power systems due to low cost and its flexibility Correct estimation of cabtyre cable parameters is necessary to compute overvoltage phenomena in cabtyre cable applications The primary physical parameters resistance, inductance, capacitance and conductance are necessary to evaluate the phenomena The resistance, capacitance and inductance are essential for representing the wave propagation characteristics along the cable In this paper, parameters of a cabtyre cable are investigated by measurements This study is helpful for modeling a cabtyre cable

Abstract: In spite of having excellent short-term dielectric properties, polymeric insulated cables are subjected to serious degradation problems due to defects, water treeing, partial discharges, etc… Canada more than 20% of the installed power cables are older than their designed life-time. Therefore, utilities are challenged to make the right decisions in repairing, refurbishing or completely replacing older cables. The best option for utilities is to apply a so called “smart replacement strategy of power cables”, i.e. only replacing cables that could adversely affect the reliability of a network in the near future. This will be the best approach to cut operation costs as well as increase the reliability of a power system. The implementation of such a strategy can only be accomplished if and when the utilities have access to reliable and non-destructive diagnostic tools that can be applied on-site. At the National Research Council of Canada (NRC), an on-site testing technique for estimating the degree of degradation of power cables based on the polarization/depolarization current principle has been developed using a nearly noiseless high voltage solid state switch with a few ns rise time. The high frequency (HF) components of the depolarization current (I DEP ) can be measured and the area under the HF component of the I DEP curve, Q Dep , can be linked to the intensity of water treeing in cable insulations. This was observed from a series of tests on flat samples and miniature cables aged in a wet environment, and from measuring specimens removed from failed cables. Using Q Dep as Diagnostic Indicator, the tested cables were divided into three categories: Good Condition, Fair Condition and Poor Condition. In 2011 this technique was applied to a large number of cables in the local utility network. The results of these tests will be described in this paper. It will be shown that the age was not the determining factor of the cable condition. Also, it will be clarified that only −1 kV dc is sufficient to assess the condition of cables, therefore, testing with −3 kV will not change the condition determined with 1 k kV.

Abstract: The 11kV distribution cables in HK Electric system are installed underground by direct burial method. PILC (Paper Insulated Lead Covered) cables were commonly installed prior to 1976, before the adoption of XLPE (Cross Linked Polyethylene) cables.

Abstract: The selection of both lightning and switching impulse test values for a power DC link are mainly based on numerical simulation and past experience on similar links, since well-established and standardized practices are missing In this paper, as a continuation of a previous investigation, the selection of lightning and switching impulse voltage levels to be applied on short cable lengths in the prequalification and/or type tests is addressed for long DC cable lines taking into account the impulse withstand behaviour vs cable length via the enlargement law and the effect of overvoltage attenuation for surges travelling along the cable In particular, a deeper analysis into the algorithm of voltage impulse level selection is performed aiming at considering the typical range of variation of all the parameters that take part in this process The analysis is performed via Montecarlo simulations considering all the variable involved in the estimation of the impulse withstand voltages This approach is particular useful since at present standardized impulse voltage levels for HVDC cables are still left to an agreement between manufacturer and user

Abstract: In electro-energy an important problem is to ensure production and transport of electricity in optimum conditions and safety. In this respect knowing of the degree of aging of electrical equipment (transformers, cables, accessories, etc.) becomes a strategy matter of the maintenance management. Optimized and improved test methods and equipment for HV and MV power cables for the early detection of existing defects in the insulation by assessing the partial discharges (PD) have developed. The news trends in the achievement of the modern electrical equipment for test the electrical cables, on-line or off-line, have objective to increase the sensibility, the diminution of the consumption of power energy, the reproductibility of the test condition, to be easy in use and portable in site etc. This paper presents classical and modern methods of off-line and on-site testing with AC power cables. A comparative study is made on energy consumption required by conventional methods of testing with AC voltage power cables (AC method with line frequency and AC method with series resonant circuit) and the method Oscillating Wave Test System - OWTS using damped AC Voltages (DAC). Calculations have shown a substantial less consumption of the OWTS method comparison with the AC method known and analyzed in this paper, underlining the economical character of the OWTS method.

Abstract: The calculation of transients in power cables requires both the use of accurate simulation models and proper formulations for the representation of the imperfect earth. However, the scarcity of available field tests in the literature leads to questionable results in several simulation cases. In this paper a set of field measurements is presented, which has been conducted on a medium-voltage single-core cable lying on the ground surface. The cable is excited by various types of voltage sources, while several grounding and termination scenarios are implemented. The examined cable is further modified and modeled in order to simulate transient phenomena, using a recently developed frequency-domain universal model, including different earth formulations. The simulation results are compared with the corresponding field measurements, leading to significant remarks. An improvement in the calculation of the frequency dependent per-unit-length parameters is also proposed, which may lead to the more accurate modeling of cables lying on the ground surface.

Abstract: Underground residential distribution (URD) power cables are aged due to electrical, thermal, mechanical stresses and environmental stress during their service. For utilities, the online diagnostics of the dielectric conditions of the cables are of much interest. One of the cable online diagnostic methods is based on analysis of the voltage transients in URD. The cable elbow connectors are manufactured with capacitive voltage test points to indicate the power frequency voltage on the cable conductor. A voltage transient measurement system based on signal processing using the cable elbow connectors will be presented in the paper. Using this technique, less expensive cable elbow connectors can be calibrated and installed widespread in underground residential distribution power cables.

Abstract: Still today on-site testing of high voltage AC and DC extruded cables is a challenging and not clearly defined task. The aim of this paper is to show important aspects of on-site testing and to explain why performing on-site tests is still a technical, economical and physical challenge. One reason is the physical length of the laid cables and the increasing test voltage. For DC cables lengths of more than 100 km is more and more asked for. The cable capacitance increases linearly with length, the needed test power quadratic with the applied test voltage.

Abstract: This paper presents a method of 1394b bus transmission cable electric parameters testing and provides a reliable way in selecting transmission cable. This paper introduces the IEEE-1394b protocol for transmission cable of electric parameters and requirements. We set up platform for 1394 cable testing, taking four kinds of 1394 bare wire cable and cable with Quadrax connector for dielectric withstanding voltage, differential impedance and so on. Using this test method can accurately reflect the 1394 cable’s electrical characteristics.

Abstract: This paper presents a new concept of an ultra-low loss cable which can be used in transmission and distribution systems. The cable has been developed by the reconfiguring of a capacitor which has a “theoretically” zero loss and practically ultra- low losses. The main idea behind this new concept is to present the cable as a linear capacitor where the power can be transmitted without any significant losses.

Abstract: Based on the international experiences as collected in the last 2 years at different power grids, cable manufacturers and normalisation work of international bodies, this contribution focuses on several fundamental and applied aspects of on-site testing and diagnosis of new and service aged HV power cables Based on the above consideration and evaluation and supported by field experiences, a concept of testing recommendation and procedure will be discussed In particular different important aspect of testing new connections as well as condition assessment of service aged power cables will be mentioned in this paper

Abstract: XLPE insulated power cables are used for transmission and distribution of electrical power in urban centers. Extensive high voltage testing is conducted on such cables for performance evaluation and quality control purposes. During such testing, the cable ends have to be prepared carefully to make a proper end termination. Usually deionized water terminations are used for this purpose. Alternatively conductive paint is used to prepare a resistive termination. This paper discusses a method of calculating the voltage distribution across such a resistive termination when subjected to impulse high voltages. The proposed method is used to determine the effect of different design parameters on the impulse stress distribution of such cable ends.