The influence of DC component within combined AC and DC voltage on charge dynamics in polyethylene

The influx of a switching impulse during DC steady-state operations causes severe electrical stress on the insulation of HVDC cables. Thus, the insulation should be designed to withstand a superimposed switching impulse. All major manufacturers of DC cables perform superimposed switching impulse breakdown tests for prequalification. However, an experimental approach to study space charge dynamics in dielectrics under a switching impulse superposed on DC voltage has not been reported yet. This is because, unlike the DC stress, it is not possible to study the charge dynamics experimentally under complex stresses, such as switching impulse superposition. Hence, in order to predict and investigate the breakdown characteristics, it is necessary to obtain accurate electric field distribution considering space charge dynamics using a numerical approach. Therefore, in this paper, a numerical study on the switching impulse superposition was carried out. The space charge dynamics and its distribution within the dielectric under DC stress were compared with those under a superimposed switching impulse using a bipolar charge transport (BCT) model. In addition, we estimated the effect of a superimposed switching impulse on a DC electric field distribution. It was concluded that the temperature conditions of dielectrics have a significant influence on electric field and space charge dynamics.

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Space charge dynamics at the physical interface in oil-paper insulation under DC voltage

IEEE Transactions on Dielectrics and Electrical Insulation ◽

10.1109/tdei.2015.7116372 ◽

2015 ◽

Vol 22 (3) ◽

pp. 1739-1746 ◽

Cited By ~ 19

Author(s):

Meng Huang ◽

Yuanxiang Zhou ◽

Weijiang Chen ◽

Licheng Lu ◽

Fubao Jin ◽

...

Keyword(s):

Space Charge ◽

Dc Voltage ◽

Charge Dynamics ◽

Paper Insulation

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Numerical modelling on partial discharge in HVDC XLPE cable

COMPEL The International Journal for Computation and Mathematics in Electrical and Electronic Engineering ◽

10.1108/compel-07-2017-0297 ◽

2018 ◽

Vol 37 (2) ◽

pp. 986-999 ◽

Cited By ~ 6

Author(s):

Miao He ◽

Miao Hao ◽

George Chen ◽

Xin Chen ◽

Wenpeng Li ◽

...

Keyword(s):

Numerical Model ◽

Numerical Modelling ◽

Electric Field ◽

Direct Current ◽

Distribution Systems ◽

Partial Discharge ◽

Discharge Characteristics ◽

Content Type ◽

Dc Voltage ◽

Charge Dynamics

PurposeHigh voltage direct current (HVDC) cable is an important part in the electric power transmission and distribution systems. However, very little research has been carried out on partial discharge under direct current (DC) conditions. Niemeyer’s model has been widely used under alternating current (AC) conditions. This paper aims to intend to modify the Niemeyer’s model considering both electric field and charge dynamics under DC conditions, and therefore proposes a numerical model describing partial discharge characteristics in HVDC cable. Design/methodology/approachThis paper intends to understand partial discharge characteristics under DC conditions through numerical modelling. Niemeyer’s model that has been widely used under AC conditions has been modified, taking both electric field and charge dynamics under DC conditions into consideration. The effects of loading level or current through the conductor, cavity location and material properties on partial discharges have also been studied. FindingsElectrical conductivity is important in determining the characteristics of partial discharge under DC conditions and discharges tend to happen in short when the cavity field exceeds the inception level under the parameter values studied in the paper. Research limitations/implicationsBuilding the numerical model is the purpose of the paper, and there is lack in experiment and the comparison between the simulation results and experiment. Practical implicationsThe proposed model provides the numerical model describing partial discharge in HVDC cable and helps understand the partial discharge mechanism under DC voltage. Originality/valueTo the best of the author’s knowledge, this paper is a very early research on the numerical modelling work on partial discharge under DC voltage.

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Influence of the DC offset on the DFT-based frequency estimation for noised multifrequency signals in PV systems with a DSP processor

E3S Web of Conferences ◽

10.1051/e3sconf/20186406011 ◽

2018 ◽

Vol 64 ◽

pp. 06011

Author(s):

Kania Dariusz ◽

Borkowski Józef

Keyword(s):

Signal Processing ◽

Digital Signal Processing ◽

Frequency Estimation ◽

Time Windows ◽

Estimation Method ◽

Digital Signal ◽

Dc Voltage ◽

Dc Offset ◽

Pv Systems ◽

Dc Component

Digital signal processing is present in many areas of industry and science. One of them is analyzing multifrequency signals, e.g. in photovoltaic systems. This paper focuses on the frequency estimation of pure signals and signals distorted by AWGN noise in the presence of a DC voltage offset. The used IpDFT estimation method is based on the FFT procedure, I class Rife-Vincent time windows and three points of the spectrum taken to calculations. Measurement time was limited only up to two cycles of a tested signal and the method is very accurate even below one cycle. Obtained results show that additional DC component negatively affect the accuracy. The paper can be very useful because it shows properties of the method in real measurement conditions for various values of parameters.

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