Numerical study of influential factors on partial discharges in HVDC XLPE cables

Abstract

Purpose For the dramatically developed high voltage direct current (HVDC) power transmission, HVDC cables play a vital role in the power transmission across seas and connections with renewable power sources. However, the condition monitoring of HVDC cables is still a challenging research topic. This paper aims to understand the influence of external factors, namely, current, cavity location and material properties, on partial discharge (PD) characteristics in HVDC cable in a numerical way referring to the refined Niemeyer’s model. Design/methodology/approach The influences of the three external factors are studied by a proposed numerical model for DC PDs based on the modification of a conventional PD model for AC voltage via a finite element analysis method. Findings The external factors can influence the discharge magnitude and discharge repetition rate via affecting the electrical conductivity of the material: DC PD is more frequent and with higher discharge magnitude when the cavity is closer to the conductor or the current through the conductor is higher. Both DC PD repetition rate and average discharge magnitude in long-term aged material are lower than virgin material. The effect of discharge on insulation degradation becomes decreasingly significant. Research limitations/implications The current work is based on the numerical modelling of DC PDs. Further experimental validations and comparisons are essential for improving the model. Practical implications The studies of the influence factors for PDs under HVDC voltage can benefit the research and practical power transmission on DC PDs, contributing the design and test of DC PDs in HVDC cables, exploring the understandings of the DC PDs’ mechanism. Originality/value This paper, to the best of author’s knowledge, first studies the influence factors on DC PDs based on the numerical modelling work.

Numerical Modeling of PD Pulses Formation in a Gaseous Void Located in XLPE Insulation of a Loaded HVDC Cable

“…At the same time, due to a significant increase in conductivity, the PD repetition rate increases, in particular in sources located in areas with the highest temperature, i.e., in Zone I, close to the cable core. A similar effect of changing the parameters of the PD pulse sequence was also obtained in other studies based on field modeling of the gaseous void in XLPE insulation of HVDC cables [70,72]; however, the influence of the location of the defect on the PD time sequences was not analyzed. It is seen that the factor increasing the PD repetition rate is also the E field strength, reaching for loaded cable the highest values in Zone II, especially in the area close to the outer radius of the insulation.…”

“…In order to take into account the influence of temperature and electric fields on conductivity in polymer insulation, a model function derived from the hopping theory of conduction in dielectrics is also often used [41,42,46,49,[68][69][70][71][72]:…”