Abstract: Before commencing excavation or other work where power or other cables may be buried, it is important to determine the location of cables to ensure that they are not damaged. This paper describes a method of power-cable detection and location that uses measurements of the magnetic field produced by the currents in the cable, and presents the results of tests performed to evaluate the method. The cable detection and location program works by comparing the measured magnetic field signal with values predicted using a simple numerical model of the cable. Search coils are used as magnetic field sensors, and a measurement system is setup to measure the magnetic field of an underground power cable at a number of points above the ground so that it can detect the presence of an underground power cable and estimate its position. Experimental investigations were carried out using a model and under real site test conditions. The results show that the measurement system and cable location method give a reasonable prediction for the position of the target cable.

Abstract: High voltage apparatus and reliable power supply are of vital importance for subsea processing. The purpose of this work has been to develop a small high voltage penetrator for use with high pressure vessels in the laboratory. Such equipment can facilitate high voltage and current testing of models and materials at relevant subsea conditions. It is shown that the penetrator can withstand a hydrostatic differential pressure of 500 bars and 90°C for more than 6 months. The breakdown voltage of the penetrator is only limited by the model cable used in the design, making it attractive to use high voltage class cables. Sensitive partial discharge measurements of pressurized test objects can be implemented by using adapted oil-filled terminations.

Abstract: DC high potential and insulation resistance testing have historically been used as the primary means for field installation verification testing for medium voltage power cables. Since power frequency AC high potential testing is not a practical solution for the field environment other techniques have been developed to effectively test the integrity of cables and terminations before placing MV cables in service. Among these testing methods are very low frequency (VLF), partial discharge, and tan delta testing.

Abstract: Three-core power cables with single selection generally follow the following rules:6~10 kV cables usually selected three core cable,66 kV and above the general cable select select single-core cables.However,voltage 35 kV has three-core and single cable.How is the selection of the engineers and technicians need to face a difficult problem.Based on the three core and single core cables 35 kV analysis and comparison,A clear application of their own environment and conditions for the majority of electricity and technical personnel in engineering practice,has selected the cable to provide a reference and help.

Abstract: One of the challenging issues with high voltage network connections, be it for off-shore windfarms, inter-network HVDC connections, or simply overhead line replacement is to test the complete connections before bringing them into service. Even if all components are individually tested before being brought onto the construction site the final assembly needs to tested as a complete system before it is put in service. There are currently several challenges in the area of testing 150KV and higher voltages: First for short length cables the cost of measurement is prohibitive due to the fact that most current testing equipment is designed for laboratory use, requires specialized and time consuming setup and is therefore uneconomical to use. Another challenging area is the testing of long cables completely assembled: Current testing technology requires multiple test systems to be interconnected, resulting in severe logistics and technical challenges and even then most time testing is done in sections. Furthermore for HVDC and voltages above 400kV testing is limited to laboratory tests mainly by lack of appropriate testing equipment and standards. A new technology development has promising capacities for these field testing needs: Differential Resonance Technology (DRT) is developed based on long years of experience in VLF field testing and before that specialised laboratory test equipment. Differential resonance technology, as the name describes uses the differential of 2 resonance circuits to create a high-voltage low frequency signal in the range from 0,1 Hz to 10Hz. In this way compact and powerful testing equipment for High and Ultra High voltage and DC can be constructed. Current status: the first prototype systems have been build, currently tested up to 200kV RMS, and the current product range goes from 100KV up to 400KV (RMS) and 600KV DC, and cable lengths over 100KM. Scientific work on raising the output voltage to 800KV RMS and higher load capacities for future use has been started. The paper will focus in detail on the design issues of Digital Resonance Technology High Voltage testing systems. In addition we will present typical test applications for long range cables for off-shore windmills parks and for high voltage cable projects. (3 pages)

Abstract: The presented paper concerns the insulation of cables providing the link between the converters and electrical machines in aircraft. It focuses on thermal aging tests performed on cables with the analysis of the capacitance variation. The tests were conducted on samples of a three-wire shielded cable, insulated with polyimide and polytetrafluoroethylene (PTFE). This study shows that the capacitance between the conductors of a cable is correlated with the aging of its electrical insulation.

Abstract: The increased use of cable systems in power distribution in urban areas lead to the need for more reliable cable system. To ensure the reliability of the cable system, a diagnostic system that can assess the cable system in field conditions is needed. Partial Discharge (PD) and Tan Delta (TD) are the two parameters that can be measured to diagnose the condition of cable system in the field. Based on the measurement of these parameters, the condition of cable system can be determined whether the cable is in good condition, needs attention or in bad condition. In this paper the methods of PD and TD field measurement on 20 kV cable systems are described. Furthermore, the method of analysis using data obtained from the measurement of PD and TD is also described. PD measurement in this study is performed using damped AC voltage source (DAC), while TD measurement is carried out by using Very Low Frequency voltage source (VLF). In the end an assessment scheme is proposed for cable diagnostic that can be served as a guideline for Condition Based Maintenance (CBM) of cable system. This scheme will increase not only the reliability of cable system but also the performance of power distribution network.

Abstract: Demand for low voltage cable diagnostics, arising from lifetime extension programs of power plants, grows recently. This paper reports on investigations of the authors with partial discharge testing of low voltage control, measurement and signal cables. The construction of low voltage cables differs in many ways from the middle voltage and high voltage cables, on which partial discharge diagnostics has been widely investigated and highly developed. The lack of semiconducting layers makes them less lossy on higher frequencies than MV and HV ones. These results in a different behavior of the propagation of PD induced impulses. Besides, without smoothing layers, these cables are not necessarily PD free at their test voltage. Due to the issues mentioned above, the bandwidth and impulse resolution of the measuring equipment were addressed as well as the discrimination between discharge impulses formed in the insulation bulk and on the conductor surfaces. Measurements were carried out on single and multiple conductor cables by equipments with different bandwidth. The results of the investigation are presented and discussed in this paper.

Abstract: Cross-linked polyethylene(XLPE) insulated power cables are increasingly used in high voltage and extra high voltage engineering due to technical and economical advantages.Partial discharge(PD) detection is the most effective method for testing the cable's insulation condition.However,PD signals in cross-bonded cable systems are interfered by each other,which brings about great difficulty in online PD detection,and therefore it is indispensable to research on the propagation characteristics of PD in cross-bonded XLPE cable systems through simulation and experiment.Present research results indicate that extruded semi-conducting layers in cables have a serious attenuation and dispersion effect on the high frequency components of PD.Based on the improved cable model proposed by Blackburn,and through properly adjusting parameters,a J-Marti frequency-dependent model for three-phase cross-bonded cable systems was established;and the PD propagation characteristics in this model were explored.Experimental results showed that this model can reasonably explain the propagation characteristics of PD signals in three-phase cross-bonded cable systems.

Abstract: This paper presents the results of a study carried out in order to perform a condition assessment of seven MV submarine cables operated by Hydro-Quebec Distribution (HQD). The assessment was based of the principle of dielectric loss characterization. Two methods were chosen: Time Domain Spectroscopy (TDS) and VLF Tan delta. Results show that combining the two methods provides a valuable source of information. The use of VLF Tan delta also allows for comparison with the extensive measurement database of tests performed on other equivalent cable systems.

Abstract: This paper investigates the operation of single core underground medium voltage cables connected in parallel. The examination is based on an existing power cable arrangement connecting a 38 MW wind farm with the transmission grid. The cable arrangement consists of nine single core cables connected in parallel to form a triple 3-phase system. Several connection scenarios such as the earthing of the cable sheaths at one or both ends and the application of sheath cross-bondings are examined. Various simulation parameters are also investigated such as the grounding resistance of the cable sheaths and the number of the cable sheath transpositions. The respective voltages and currents induced on the cable sheaths are calculated under steady-state and short circuit conditions.