Review of recent research towards power cable life cycle management

Power cables are integral to modern urban power transmission and distribution systems. For power cable asset managers worldwide, a major challenge is how to manage effectively the expensive and vast network of cables, many of which are approaching, or have past, their design life. This study provides an in-depth review of recent research and development in cable failure analysis, condition monitoring and diagnosis, life assessment methods, fault location, and optimisation of maintenance and replacement strategies. These topics are essential to cable life cycle management (LCM), which aims to maximise the operational value of cable assets and is now being implemented in many power utility companies. The review expands on material presented at the 2015 JiCable conference and incorporates other recent publications. The review concludes that the full potential of cable condition monitoring, condition and life assessment has not fully realised. It is proposed that a combination of physics-based life modelling and statistical approaches, giving consideration to practical condition monitoring results and insulation response to in-service stress factors and short term stresses, such as water ingress, mechanical damage and imperfections left from manufacturing and installation processes, will be key to success in improved LCM of the vast amount of cable assets around the world

Time domain analysis of switching transient fields in high voltage substations

Switching operations of circuit breakers and disconnect switches generate transient currents propagating along the substation busbars. At the moment of switching, the busbars temporarily acts as antennae radiating transient electromagnetic fields within the substations. The radiated fields may interfere and disrupt normal operations of electronic equipment used within the substation for measurement, control and communication purposes. Hence there is the need to fully characterise the substation electromagnetic environment as early as the design stage of substation planning and operation to ensure safe operations of the electronic equipment. This paper deals with the computation of transient electromagnetic fields due to switching within a high voltage air-insulated substation (AIS) using the finite difference time domain (FDTD) metho

Implementation of explosion safety regulations in design of a mobile robot for coal mines

The article focuses on specific challenges of the design of a reconnaissance mobile robotic system aimed for inspection in underground coal mine areas after a catastrophic event. Systems that are designated for these conditions must meet specific standards and regulations. In this paper is discussed primarily the main conception of meeting explosion safety regulations of European Union 2014/34/EU (also called ATEX-from French "Appareils destines a etre utilises en ATmospheres Explosives") for Group I (equipment intended for use in underground mines) and Category M1 (equipment designed for operation in the presence of an explosive atmosphere). An example of a practical solution is described on main subsystems of the mobile robot TeleRescuera teleoperated robot with autonomy functions, a sensory subsystem with multiple cameras, three-dimensional (3D) mapping and sensors for measurement of gas concentration, airflow, relative humidity, and temperatures. Explosion safety is ensured according to the Technical Report CLC/TR 60079-33 "s" by two main independent protections-mechanical protection (flameproof enclosure) and electrical protection (automatic methane detector that disconnects power when methane breaches the enclosure and gets inside the robot body).Web of Science811art. no. 230

Fault location and diagnosis in a medium voltage EPR power cable

This paper presents a case study on fault location, characterization and diagnosis in a length of shielded 11 kV medium voltage ethylene-propylene rubber (EPR) power cable. The defect was identified on-site as a low resistance fault occurring between the sheath and the core. A 43 m section was removed for further analysis. The fault resistance was characterized and the location of the defect pinpointed to within a few cm using a combination of time-difference-of-arrival location and infra-red imaging. A combination of X-ray computed tomography, scanning electron microscopy and energy dispersive X-ray spectroscopy were then applied to characterize any abnormalities in the dielectric surrounding the breakdown region. A significant number of high density contaminants were found to be embedded in the dielectric layer, having an average diameter of the order of 100 um, a maximum diameter of 310 um and an average density of 1 particle per 2.28 mm3 . Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to determine the geometry and elemental composition of some initial contaminant samples. It was concluded that contamination of the EPR layer, combined with an observed eccentricity of the cable’s core and sheath resulting in a reduced insulation gap, may have led to an electric field concentration in the region of the defect sufficient to initiate breakdown. Preventative strategies are discussed for similar families of cables, including more stringent dielectric testing requirements at the manufacturing stage and PD monitoring to detect incipient failure

Power quality and electromagnetic compatibility: special report, session 2

The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15

Methodology for the Accelerated Reliability Analysis and Prognosis of Underground Cables based on FPGA

Dependable electrical power distribution systems demand high reliability levels that cause increased maintenance costs to the utilities. Often, the extra costs are the result of unnecessary maintenance procedures, which can be avoided by monitoring the equipment and predicting the future system evolution by means of statistical methods (prognostics). The present thesis aims at designing accurate methods for predicting the degradation of high and medium voltage underground Cross-Linked Polyethylene (XLPE) cables within an electrical power distribution grid, and predicting their remaining useful life, in order inform maintenance procedures. However, electric power distribution grids are large, components interact with each other, and they degrade with time and use. Solving the statistics of the predictive models of the power grids currently requires long numerical simulations that demand large computational resources and long simulation times even when using advanced parallel architectures. Often, approximate models are used in order to reduce the simulation time and the required resources. In this context, Field Programmable Gate Arrays (FPGAs) can be employed to accelerate the simulation of these stochastic processes. However, the adaptation of the physicsbased degradation models of underground cables for FPGA simulation can be complex. Accordingly, this thesis proposes an FPGA-based framework for the on-line monitoring and prognosis of underground cables based on an electro-thermal degradation model that is adapted for its accelerated simulation in the programmable logic of an FPGA.Energia elektrikoaren banaketa-sare konfidagarriek fidagarritasun maila altuak eskatzen dituzte, eta honek beraien mantenketa kostuen igoera dakar. Kostu hauen arrazoia beraien bizitzan goizegi egiten diren mantenketa prozesuei dagokie askotan, eta hauek eragoztea posible da, ekipamenduaren monitorizazioa eginez eta sistemaren etorkizuneko eboluzioa aurrez estimatuz (prognosia). Tesi honen helburua lurpeko tentsio altu eta ertaineko Cross-Linked Polyethylene (XLPE) kable sistemen eboluzioa eta geratzen zaien bizitza aurreikusiko duten metodo egokiak definitzea izango da, banaketa-sare elektriko baten barruan, ondoren mantenketa prozesu optimo bat ahalbidetuko duena. Hala ere, sistema hauek oso jokaera dinamikoa daukate. Konponente ezberdinek beraien artean elkar eragiten dute eta degradatu egiten dira denboran eta erabileraren ondorioz. Estatistika hauen soluzio analitikoa lortzea ezinezkoa da gaur egun, eta errekurtso asko eskatzen dituen simulazio luzeak behar ditu zenbakizko erantzun bat lortzeko, arkitektura paralelo aurreratuak erabili arren. Field Programmable Gate Array (FPGA)k prozesu estokastiko hauen simulazioa azkartzeko erabil daitezke, baina lurpeko kableen degradazio prozesuen modelo fisikoak FPGA exekuziorako egokitzea konplexua izan daiteke. Beraz, tesi honek FPGA baten logika programagarrian azeleratu ahal izateko egokitua izan den degradazio elektrotermiko modelo baten oinarritutako monitorizazio eta prognosi metodologia bat proposatzen du.Las redes de distribución de energía eléctrica confiables requieren de altos niveles de fiabilidad, que causan un mayor coste de mantenimiento a las empresas distribuidoras. Frecuentemente los costes adicionales son el resultado de procedimientos de mantenimiento innecesarios, que se pueden evitar por medio de la monitorización de los equipos y la predicción de la evolución futura del sistema, por medio de métodos estadísticos (prognosis). La presente tesis pretende desarrollar métodos adecuados para la predicción de la degradación futura de cables de alta y media tensión Cross-Linked Polyethylene (XLPE) soterrados, dentro de una red de distribución eléctrica, y predecir su tiempo de vida restante, para definir una secuencia de mantenimiento óptima. Sin embargo, las redes de distribución eléctrica son grandes, y compuestas por componentes que interactúan entre sí y se degradan con el tiempo y el uso. En la actualidad, resolver estas estadísticas predictivas requieren grandes simulaciones numéricas que requieren de grandes recursos computacionales y largos tiempos de simulación, incluso utilizando arquitecturas paralelas avanzadas. Las Field Programmable Gate Array (FPGA) pueden ser utilizadas para acelerar las simulaciones de estos procesos estocásticos, pero la adaptación de los modelos físicos de degradación de cables soterrados para su simulación en una FPGA puede ser complejo. Así, esta tesis propone el desarrollo de una metodología de monitorización y prognosis cables soterrados, basado en un modelo de degradación electro-térmico que está adaptado para su simulación acelerada en la lógica programable de una FPGA