A Generic Approach for HVDC Cable Accessories Modelling

Frobin, Saskia Josefine; Niedik, Christoph Felix; Freye, Claudius; Jenau, Frank; Haring, Dominik; Schroder, G.H.

doi:10.1109/icd.2018.8468426

Cited by 4 publications

(6 citation statements)

References 10 publications

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“…Based on this rule, the tangential field near the central deflector will be the largest in case of SiR joint material and for the EPDM at 30 • C, i.e., in cases where a minimization of the tangential field under the cone is obtained. A better control of the field at the central deflector will be reached with shaping it, as is obtained for the cone [4,9].…”

Section: Discussionmentioning

confidence: 93%

“…In this contribution, we report mainly on the modelling of the electric field distribution in unsteady situations from the electrical and thermal point of view in cable accessories comprising an association of insulators of different nature in a specific geometry. In many situations, simulations have been conducted on admittedly complex objects but in a stationary situation [4]. However, one must wonder about the redistribution of the electric field in the case in which the transmitted power suddenly increases, implying to have a thermal transient in the accessory and also to have an idea of the thermal equilibrium time of the system.…”

Section: Introductionmentioning

confidence: 99%

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Electric Field Distribution in HVDC Cable Joint in Non-Stationary Conditions

Teyssèdre

Roy

2021

Energies

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Accessories such as joints and terminations represent weak points in HVDC cable systems. The DC field distribution is intimately dependent on the thermal conditions of the accessory and on material properties. Moreover, there is no available method to probe charge distribution in these conditions. In this work, the field distribution in non-stationary conditions, both thermally and electrically, is computed considering crosslinked polyethylene (XLPE) as cable insulation and different insulating materials (silicone, rubber, XLPE) for a 200 kV joint assembled in a same geometry. In the conditions used, i.e., temperatures up to 70 °C, and with the material properties considered, the dielectric time constant appears of the same order or longer than the thermal one and is of several hours. This indicates that both physical phenomena need to be considered for modelling the electric field distribution. Both the radial and the tangential field distributions are analysed, and focus is given on the field distribution under the stress cone on the ground side and near the central deflector on the high voltage side of the joint. We show that the position of the maximum field varies in time in a way that is not easy to anticipate. Under the cone, the smallest tangential field is obtained with the joint insulating material having the highest electrical conductivity. This results from a shift of the field towards the cable insulation in which the geometrical features produce a weaker axial component of the field. At the level of the central deflector, it is clear that the tangential field is higher when the mismatch between the conductivity of the two insulations is larger. In addition, the field grows as a function of time under stress. This work shows the need of precise data on materials conductivity and the need of probing field distribution in 3D.

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Section: Discussionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Electric Field Distribution in HVDC Cable Joint in Non-Stationary Conditions

Teyssèdre

Roy

2021

Energies

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“…Therefore, the corresponding equation was applied so that the conductivity of XLPE and SiR depended on temperature and electric field. The main parameters used in the thermal electrical model are shown in Table 1 [32,33]. Figure 3b shows the joint cross-sectional structure used in the thermal mechanical model to compare the interfacial pressure according to the load cycle.…”

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confidence: 99%

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confidence: 99%

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Numerical Analysis of Electric Field Characteristics and Interfacial Pressure of HVDC XLPE Cable Joint Considering Load Cycles

et al. 2022

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Recent innovations in HVDC extruded cable systems require the development of reliable and safe cable accessories. Cable accessories are made of several insulating materials and contain several interfaces. Interfaces made of different materials can cause electric field distortion and localized enhancement of the field. In addition, the internal temperature profiles of accessories differ depending on load conditions or installation environments, which may lead to an increase in or loss of interfacial pressure due to changes in the mechanical properties of materials. The loss of interfacial pressure degrades the contact state between materials. The micro voids formed due to pressure loss can cause partial discharge and tree, which in turn can lead to reduced lifespan and failure of the cable system. Therefore, it is necessary to study the electrical and mechanical characteristics of cable accessories considering various transient states. However, there is a limit to experimentally analyzing the actual structure. In this paper, electric field and mechanical stress for pre-molded cable joints were analyzed using an electrical model based on the conductivity of the material and a mechanical model based on elastic theory. Temperature fluctuations were simulated according to the sequence of the cable load cycle test, and time-varying electric fields and mechanical stresses were analyzed. From the simulation results, it was confirmed that the electric field and stress distribution in the joint continuously changed according to the heating and cooling periods. In addition, during the cooling cycle, the field strength at the interface near the conductor increased and the interface pressure decreased. In conclusion, it is important to ensure sufficient initial pressure so that the dielectric strength at the interface does not decrease even if there is a loss of interface pressure due to temperature fluctuations.

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Insulating Materials for HVDC Cable Accessories: Effects on the Electric Field in Nonstationary Situations

Teyssèdre¹,

Roy³

2022

IEEE Electr. Insul. Mag.

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With the move to DC technologies for power transmission, the computation of the field distribution in insulations has become a tricky task as the materials response is less well mastered as under ac stress. This is true for HVDC cables where essentially the conductivity law must be identified for the used insulating material. Cables represent a relatively simple case study. Accessories as cable joints and terminations are certainly more delicate to address. First, more than one material has to be handled; second the translational symmetry is broken, and tangential fields have to be computed in a situation of inhomogeneous temperature conditions. Finally, non-stationary situations have to be managed and modelled for accounting for on-line operations as well as surges seen by cables. Our purpose in this work is to give an overview on how far these transient phenomena are handled in the literature and to demonstrate how far the electrical as well as thermal properties of materials actually determine the field distributions.

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A Generic Approach for HVDC Cable Accessories Modelling

Cited by 4 publications

References 10 publications

Electric Field Distribution in HVDC Cable Joint in Non-Stationary Conditions

Electric Field Distribution in HVDC Cable Joint in Non-Stationary Conditions

Numerical Analysis of Electric Field Characteristics and Interfacial Pressure of HVDC XLPE Cable Joint Considering Load Cycles

Insulating Materials for HVDC Cable Accessories: Effects on the Electric Field in Nonstationary Situations

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