Modeling water tree phenomenon for insulated cable loss current estimation

Abstract-It is widely recognized that one of the major problems responsible for unscheduled interruptions is related to the degradation of power cables insulation. The water tree effect emerges as an important cause for the deterioration of their insulation layer. In this context, the loss current technique is a suitable method for investigating slight degradation, since the cable degradation by water tree gives rise to harmonics components in the loss current. This paper presents an analysis of the influence of the length of the water-tree, the voltage stress and the frequency in the values of various parameters that has been used to evaluate, predict, and indicate the operational status of operating power cables. The procedure aims to estimate the parameters of insulation deterioration from the measurement of the supply voltage and the leakage current that flows through the insulation carried out in hot-line cables without interrupting the service.

Section: Theta 3 Variation Due the Degradationmentioning

confidence: 97%

Section: Fig 5 I-v Characteristic Curves Of Water Trees [18]mentioning

confidence: 99%

A Contribution for the Diagnosis of Insulation Cables due different conditions of degradation, voltage stress and frequency.

Lima¹,

França²,

Finazzi³

et al. 2024

“…The hypothesis for this discrepancy is that the loss current obtained by the procedure 1 contains capacitive harmonics. To eliminate these capacitive harmonics in order to prove this hypothesis, is used a mathematical procedure that was developed by the authors and tested with success to recovery the loss current waveform, reported in [15]. This is feasible because through this mathematical procedure it is possible to identify the capacitive current that flows in the insulation due to water tree, as shown below.…”

Section: Experimental Loss Current Measurement Circuitmentioning

confidence: 99%

“…Taking in to account the results obtained in reference [15] it is possible to ensure that the difference between the curves obtained by the procedures mentioned above is due to the existence of capacitive harmonic components in the loss current measured by the procedure 1. By having the loss current and the capacitive current it is possible to determine the following parameters: total harmonic distortion, power loss, tanδ, I3 and θ3.…”

Section: Experimental Loss Current Measurement Circuitmentioning

confidence: 99%

A comparative analysis of loss current obtained by measuring circuits used in studies of degradation power cables

Lima¹,

Finazzi²,

Carvalho³

et al. 2024

Abstract-It is widely recognized that water tree degradation would cause serious problems and it is generally agreed that is one of the most hazardous factor in the life of XLPE power cables and hence a major cause of MV power insulation premature failure. Such accidents affect the power supply system operation and reliability. Therefore, many techniques have been developed and employed in order to detect water tree at the early stages. In this context, the loss current technique is a suitable method for investigating slight degradation, since the cable degradation by water tree gives rise to harmonics components in the loss current. A comparative analysis of the values of various performance parameters that has been used in studies to evaluate the water tree degradation in power cables, obtained from the different loss current measuring circuits, is presented. This comparative analysis is made through a mathematical procedure and confirms the possibility to identify, with a very good accuracy, the loss current only from the measured leakage current without the need for specific measurement circuit used to distinguish the loss current that flows in the insulation layer. Furthermore opens the possibility to use the Fryze's equivalent conductance to eliminate in real cases the fundamental capacitive current of the total leakage current and perform online diagnosis only from the applied voltage and total leakage current measurements.

“…Researchers conducted and described in [10][11][12][13], complementary to the state of art of the theme, report contributions towards the establishment of mathematical models to represent and simulate water tree phenomena and, from sampled data, show directions to obtain performance indexes that indicate the operational state of insulated cables.…”

Section: Introductionmentioning

confidence: 99%

Performance Analysis of Methods at Estimating Insulated Cables Degradation

Velasco¹,

Reis²,

Oliveira

et al. 2024

Self Cite

The quality of electricity supply, among other issues, deals with continuity indicators as one of the most important factors for the characterization of an adequate service as far as power quality is concerned. In this context, one of the major problems responsible for the unscheduled interruptions is related to the degradation of electrical cables insulation and the well-known water tree effect emerges as an important cause for the deterioration of their insulation layer. If this phenomenon happens, a large loss of insulating properties of dielectric material used to build up such component will occur. In light of these facts, the development of procedures to evaluate, predict, and indicate the operational status of operating cables shows itself highly attractive in order to improve the quality and reliability of energy supply. Focusing on this subject, this paper presents a synthesis of existing methods and a new trend towards the mentioned matter. By using experimental measurements, carried out in medium voltage commercial operating cables in a distribution utility throughout non-invasive approach, applied voltage and insulating leakage currents are obtained to support the analysis. The data are used to obtain degradation indexes to estimate the cables physical operational conditions and the indicators found are further considered in the view of the effectiveness of the strategies for the diagnosis purposes.