Comparison of Two Electro-Quasistatic Field Formulations for the Computation of Electric Field and Space Charges in HVDC Cable Systems

Jörgens, Christoph; Clemens, Markus

doi:10.1109/compumag45669.2019.9032818

Cited by 4 publications

(15 citation statements)

References 5 publications

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“…The solution of Equation ( 4) yields only the potential, and the corresponding space charge density is obtained in a postprocessing step, using Equation (2). Nearly identical results are obtained by utilizing both formulations; however, tests in [11] showed that the scalar potential field formulation has better stability characteristics.…”

Section: Numerical Computation Of the Coupled Electro Thermal Fieldmentioning

confidence: 99%

“…showing that Equations ( 6)-( 8) are mathematically equivalent to Equation (9) [10,11]. Applying e.g., the explicit Euler time integration method to the system of ordinary differential Equation ( 9), the vector of scalar potentials Φ m+1 = Φ(t m+1 ) in the discrete time step m + 1 is computed by…”

Section: Numerical Computation Of the Coupled Electro Thermal Fieldmentioning

confidence: 99%

“…A sketch of the cable model geometry is shown on the right side in the same figure. The HVDC cable model is 6)-( 8) [11].…”

Section: Single Cablementioning

confidence: 99%

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Electric Field and Temperature Simulations of High-Voltage Direct Current Cables Considering the Soil Environment

Jörgens

Clemens

2021

Energies

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For long distance electric power transport, high-voltage direct current (HVDC) cable systems are a commonly used solution. Space charges accumulate in the HVDC cable insulations due to the applied voltage and the nonlinear electric conductivity of the insulation material. The resulting electric field depends on the material parameters of the surrounding soil environment that may differ locally and have an influence on the temperature distribution in the cable and the environment. To use the radial symmetry of the cable geometry, typical electric field simulations neglect the influence of the surrounding soil, due to different dimensions of the cable and the environment and the resulting high computational effort. Here, the environment and its effect on the resulting electric field is considered and the assumption of a possible radial symmetric temperature within the insulation is analyzed. To reduce the computation time, weakly coupled simulations are performed to compute the temperature and the electric field inside the cable insulation, neglecting insulation losses. The results of a weakly coupled simulation are compared against those of a full transient simulation, considering the insulation losses for two common cable insulations with different maximum operation temperatures. Due to the buried depth of HV cables, an approximately radial symmetric temperature distribution within the insulation is obtained for a single cable and cable pairs when, considering a metallic sheath. Furthermore, the simulations show a temperature increase of the earth–air interface above the buried cable that needs to be considered when computing the cable conductor temperature, using the IEC standards.

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Section: Numerical Computation Of the Coupled Electro Thermal Fieldmentioning

confidence: 99%

Section: Numerical Computation Of the Coupled Electro Thermal Fieldmentioning

confidence: 99%

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Electric Field and Temperature Simulations of High-Voltage Direct Current Cables Considering the Soil Environment

Jörgens

Clemens

2021

Energies

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“…Several authors outlined the modeling and simulation of HV cable joints [21,22]. Only a few systematic investigations have been carried out so far on the nonlinear field-controlling behavior of HVDC cable joints [23][24][25]. The strongly field and temperature dependent electric conductivity of the FGM exacerbates the numerical simulation of these joints (see, e.g., [5,25]).…”

Section: Introductionmentioning

confidence: 99%

Towards Electrothermal Optimization of a HVDC Cable Joint Based on Field Simulation

et al. 2021

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Extruded high-voltage direct current cable systems transmit electric power over long distances. Numerical field simulation can provide access to the internal electrothermal behavior of cable joints, which interconnect cable sections. However, coupled nonlinear electrothermal field simulations are still a challenge. In this work, a robust numerical solution approach is implemented and validated. This approach allows for efficient parameter studies of resistively graded high-voltage direct current cable joint designs. It is assessed how the dielectric stress distribution between the conductor connection and the grounded cable sheath is influenced by nonlinear field and temperature dependent electric conductivity of the field grading material. Optimal field grading material parameters, which fulfill the field grading and power loss requirements, are suggested based on the simulation studies.

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“…Many researchers have focused their attention on the amount of space charge accumulated within the insulation of HVDC cables in presence of thermal gradient, coming to the conclusion that the importance of this phenomenon can be generally considered as proportional to the size of the cable [7][8][9][10]. This is because the thicker the dielectric of a cable, the greater its thermal resistance and therefore the drop in temperature between the internal and the external boundary.…”

Section: Introductionmentioning

confidence: 99%

The Effect of the Axial Heat Transfer on Space Charge Accumulation Phenomena in HVDC Cables

et al. 2020

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To date, it has been widespread accepted that the presence of space charge within the dielectric of high voltage direct current (HVDC) cables is one of the most relevant issues that limits the growing diffusion of this technology and its use at higher voltages. One of the reasons that leads to the establishment of space charge within the insulation of cables is the temperature dependence of its conductivity. Many researchers have demonstrated that high temperature drop over the insulation layer can lead to the reversal of the electric field profile. In certain conditions, this can over-stress the insulation during polarity reversal (PR) and transient over voltages (TOV) events accelerating the ageing of the dielectric material. However, the reference standards for the thermal rating of cables are mainly thought for alternating current (AC) cables and do not adequately take into account the effects related to high thermal drops over the insulation. In particular, the difference in temperature between the inner and the outer surfaces of the dielectric can be amplified during load transients or near sections with axially varying external thermal conditions. For the reasons above, this research aims to demonstrate how much the existence of “hot points” in terms of temperature drop can weaken the tightness of an HVDC transmission line. In order to investigate these phenomena, a two-dimensional numerical model has been implemented in time domain. The results obtained for some case studies demonstrate that the maximum electric field within the dielectric of an HVDC cable can be significantly increased in correspondence with variations along the axis of the external heat exchange conditions and/or during load transients. This study can be further developed in order to take into account the combined effect of the described phenomena with other sources of introduction, forming, and accumulation of space charge inside the dielectric layer of HVDC cables.

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Comparison of Two Electro-Quasistatic Field Formulations for the Computation of Electric Field and Space Charges in HVDC Cable Systems

Cited by 4 publications

References 5 publications

Electric Field and Temperature Simulations of High-Voltage Direct Current Cables Considering the Soil Environment

Electric Field and Temperature Simulations of High-Voltage Direct Current Cables Considering the Soil Environment

Towards Electrothermal Optimization of a HVDC Cable Joint Based on Field Simulation

The Effect of the Axial Heat Transfer on Space Charge Accumulation Phenomena in HVDC Cables

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