An approach to the modelling of partial discharges in electrical trees

Abstract

A partial discharge model has been developed to simulate experimental partial discharge activity within electrical tree structures grown in polymeric based insulation. A pin plane electrode arrangement and tree were defined on a grid representing an area 2 mm by 2.1 mm. A sinusoidal 50 Hz voltage was applied to the pin tip and 3600 time steps per cycle were used to give a phase resolution of . Partial discharges were simulated at each time step by adding one or more dipoles of charge onto the tree structure to reduce the potential difference between adjacent points in the tree from to . Each dipole of charge represents a local electron avalanche occurring over a distance equal to the grid spacing. The model parameters, and , represent the discharge properties of the decomposition gas. Partial discharge current pulses in the external circuit and the induced image charge were calculated as a function of time. The spatial distribution of the emitted light in the tree structure over one cycle of the applied voltage was also calculated. The close agreement between the calculated and experimental data suggests that the underlying assumptions used in the construction of the partial discharge model are appropriate for the case of electrical trees grown in the flexible epoxy resin.

Partial discharge patterns in conducting and non-conducting electrical trees

“…2c and 2d, it is noteworthy to emphasize that the partial discharge rates are significantly higher while the magnitudes of the measured discharges are approximately 2-3 orders of magnitude smaller. The deterministic simulation model of PDs in electrical trees proposed in [4,6] was used to simulate the PD activity in conducting and non-conducting electrical trees and to obtain the corresponding PD apparent charge magnitudes. The PDs were simulated over 50 cycles of the applied sinusoidal voltage, so that the results of the simulation can be directly compared to the experimental data.…”

“…Deterministic simulations of the partial discharges within electrically conducting and non-conducting tree structures were based on the techniques described in references [4,6]. The simulations were based on using spheres of charge to describe the pin electrode and the induced charge at the pin-tip from charge contained within the tree structure.…”

“…Deterministic models of electrical tree growth have been quite successful in producing branched structures and have provided an insight into the physical processes governing electrical tree inception and propagation [3]. A deterministic approach was adopted in [4] for modelling partial discharges in electrical trees and the model was successful in reproducing the spatial extent of the partial discharge activity and the PD apparent charge magnitudes. However, the model was not investigated further to determine whether such deterministic models can reproduce the statistical characteristics of the PD patterns observed in the experiments.…”

Stochastic Modeling of Electric Tree Progression due to Partial Discharge Activity

“…Tree progression is assumed to proceed in a step-wise fashion under the combined influence of the actual field conditions and random unknown factors [4]. Tree progression occurs when the field at a tree tip exceeds the critical field, E, for the given material, forming fine filamentary tree channels due to erosion of material.…”

Tree growth in a propylene / ethylene copolymer: relationships between electrical activity during growth and the structure, chemistry and properties of the trees that result

“…It is evident that, during treeing, electrical activity occurs within just a subset of the available branches within the tree; presumably, this is driven by the local field distribution [5]. Time and spatially varying PD therefore influence, and are influenced by, the dynamic space charge distribution within the tree structure that forms.…”