Charge-Simulation-Based Electric Field Analysis and Electrical Tree Propagation Model with Defects in 10 kV XLPE Cable Joint

Abstract

The most severe partial discharges and main insulation failures of 10 kV cross-linked polyethylene cables occur at the joint due to defects caused by various factors during the manufacturing and installation processes. The electric field distortion is analyzed as the indicator by the charge simulation method to identify four typical defects (air void, water film, metal debris, and metal needle). This charge simulation method is combined with random walk theory to describe the stochastic process of electrical tree growth around the defects with an analysis of the charge accumulation process. The results illustrate that the electrical trees around the metal debris and needle are more likely to approach the cable core and cause main insulation failure compared with other types of the defects because the vertical field vector to the cable core is significantly larger than the field vectors to other directions during the tree propagation process with conductive defects. The electric field was measured around the cable joint surface and compared with the simulation results to validate the calculation model and the measurement method. The air void and water film defects are difficult to detect when their sizes are less than 5 mm3 because the field distortions caused by the air void and water film are relatively small and might be concealed by interference. The proposed electric field analysis focuses on the electric field distortion in the cable joint, which is the original cause of the insulation material breakdown. This method identifies the defect and predicts the electrical tree growth in the cable joint simultaneously. It requires no directly attached or embedded sensors to impact the cable joint structure and maintains the power transmission during the detection process.

A Closed-form Expression to Estimate the Uncertainty of THD Starting from the LPIT Accuracy Class

“…In both expressions, P is the well-known Pochhammer function [58] implemented with the parameters m and 1 2 . The latter parameter value is due to presence of only one element under the square root expression of THD, hence to the degrees of freedom.…”

“…To this purpose, the literature provides a variety of works tackling almost all particular aspects related to the assets. For example, a critical cable accessory like the cable joint is tackled in [1][2][3][4][5], while studies on electrical insulators have been completed in [6][7][8][9]. Two asset management systems have been developed in [10,11] and the integration of electric vehicles and storage systems into smart grids has been detailed in [12] and [13], respectively.…”

Effect of Interface Defects on the Harmonic Currents in Distribution Cable Accessories under Damp Conditions

“…At the same time, formation of joints along the surface of the flashover discharge and carbonization along the surface of the cable insulation channel easily occur, resulting in joint breakdown accidents, etc. [4][5][6][7][8].…”

Modelling of Electric Field Distributions on Cable Termination Defects under DC Plus Ripples

“…Other cable insulation defects including creepage, corona, scratch and cavity were simulated and verified by practical experiments in [16], showing that corona led to a high rate of discharges and the severest electric field distortion. In addition, the electric field distributions around air void, water film, metal debris and metal needle defects within cable samples were modelled by a chargebased simulation method and experimentally validated in [17], finding that the metal needle defect had the most intensive field compared to other defects under test.…”