Search results for "Insulation system"
showing 8 items of 8 documents
Partial discharge of gel insulated high voltage power modules subjected to unconventional voltage waveforms
2016
Performances and duration of the new generation of high voltage power electronic components are dependent on dielectric materials aim to insulating their internal terminals. The presence of defects, some due to faults generated during the manufacturing process, but also due to the internal design of layers and connections, can cause local enhancements of electric field and consequently possible activity of partial discharges phenomena or other effects (aging, tracking) that may result in reduction of device reliability. Furthermore, the usage of unconventional voltage waveforms, like square waves or pulse width modulated waves, additionally increases the electrical aging of the insulation s…
Electromagnetic Full-Wave Simulation of Partial Discharge Detection in High Voltage AC Cables
2019
Partial discharge (PD) activity in the insulation system of an electrical equipment can determine the failure of the whole apparatus. PD sensors are widely used in high-voltage electrical systems as the main elements of a detecting system oriented to real time monitoring. Recently, non-invasive sensors have been proposed in industrial applications for cable and other sensitive electrical parts: they are based both on capacitive and on the electromagnetic radiating coupling. In order to assess the real performance of a new sensor produced by a high voltage AC cables manufacturer, the paper proposes electromagnetic fullwave simulation results.
A portable instrument for the location and identification of defects generating PD
2011
A portable instrument based on an antenna probe and suitable for partial discharge detection, have been characterized through both laboratory and on-site experiments carried out on coils and stator windings of ac rotating machines. The antenna probe allows the capture of electromagnetic waves in a bandwidth of 0.1–100 MHz. Pulse signals and ac supply voltage reference are obtained by means of high-pass and low-pass filters, respectively, so avoiding the need of a direct connection with the objects under test. By this way, real-time phase resolved partial discharge patterns can be derived. Results of a comparison of the diagnostic information provided by PD patterns due to conducted and irra…
Design, manufacturing and testing of a fast disconnecting system for the European target assembly concept of IFMIF
2013
The International Fusion Materials Irradiation Facility (IFMIF) will be equipped with a lithium target assembly to produce the required neutron flux for the irradiation of candidate fusion materials up to a damage rate of 100 dpa (cumulated damage in five years). The present European target assembly design is based on the so called replaceable backplate bayonet concept that was developed with the objective to simplify the maintenance operations for its refurbishment/replacement and to reduce the material for disposal as well. To this purpose it was also conceived to be attached to the lithium pipes and to the beam line by means of remotely operated connections based on clamped flanges with …
Partial Discharge Detection Using a Spherical Electromagnetic Sensor
2019
The presence of a partial discharge phenomenon in an electrical apparatus is a warning signal that could determine the failure of the insulation system, terminating the service of the apparatus and/or the network. In this paper, an innovative partial discharge (PD) measurement instrument based on an antenna sensor is presented and analyzed. Being non-intrusive is one of the most relevant features of the sensor. The frequency response of the antenna sensor and the features to recognize different PD sources and automatically synchronize them with the supply voltage are described and discussed in details. The results show the performance of the instrument can make a fast and correct diagnosis …
High-Speed Machines: Typologies, Standards, and Operation under PWM Supply
2018
This paper presents an overview of the most recent state of the art in the field of high-speed electric machines fed through high-frequency converters. This type of systems is rapidly wide spreading in aeronautical and automotive applications, as well as microturbines. Each typology has its own advantages and downsides, which are analytically presented in this paper. Some types of high-speed electric machines require high-frequency voltage supply, highly stressing the dielectric materials of the winding insulation system. For this reason, in high-speed electric drives, premature failure may occur and a reduction of the total system reliability has been observed in the past years. Such issue…
Influence on PD Parameters due to Voltage Conducted Disturbances
2004
In the standard specification of ac dielectric-characteristic measurements of insulating materials, test voltage is prescribed as "approximately sinusoidal" when the highest acceptable deviation of the HV waveform, from the correct sinusoidal shape, is limited to a /spl plusmn/5% tolerance range of the crest factor value. In the field of partial discharge (PD) measurements and their statistical data processing, on which forecasts of long term behavior of components and their reliability are currently carried out, the results of elaborations depend on the voltage wave shape. In this paper, the errors in PD measurements, evaluated at industrial frequencies, due to applied voltages distorted b…
Model of ageing inception and growth from microvoids in polyethylene-based materials under AC voltage
2008
Several degradation mechanisms may affect polymeric insulation system reliability. Some authors postulate that, even in a perfect dielectric, nanoscale cavities can enlarge due to various mechanisms (from mechanical fatigue to lowering of the degradation reaction energy barrier) up to a point where highly energetic phenomena, which bring about breakdown, can be incepted. Other authors are more focused on the inherent limits of manufacturing processes, which leave cavities within the insulation system whose size is large enough to cause electron avalanches, thus a measurable partial discharge (PD) activity, from the time the system is put in service or as a function of external factors (e.g.…