Dielectric loss and extended voltage response measurements for low-voltage power cables used in nuclear power plant: potential methods for aging detection due to thermal stress

Abstract

This paper discusses the effect of thermal stress on the electrical properties, conduction and polarization, of low-voltage CSPE/XLPE-based power cables used in a nuclear power plant. The cables were subjected to an accelerated thermal stress at 120°C for an equivalent service period of 20, 40, 60 and 80 years. The capacitance, tanδ, resistivity at different frequencies and extended voltage response were the methods used for the investigation. A significant variation in the values of tanδ at low frequency, i.e., at 100 Hz, was observed. For the extended voltage response measurement, the decay voltage slope increased, showing the increase in the conduction particles inside the insulation material. While the decrease in return voltage slope showed that the slow polarization processes occurring at very low frequencies were decreased with aging. A strong correlation between the tanδ and decay voltage slope was also observed, which increased as the insulation aging increased. The results showed that the methods could be used for the in situ measurement of conduction and polarization phenomenon in the low-voltage cables, and hence helping in the assessment of the condition of cable insulation.

Implementation of Non-Destructive Electrical Condition Monitoring Techniques on Low-Voltage Nuclear Cables: I. Irradiation Aging of EPR/CSPE Cables

“…In the last few years, the EVR technique has been adopted for aging investigations in electrical insulating materials ranging from high-voltage to lowvoltage applications [23,24]. The detailed working of the EVR can be found elsewhere [1,2].…”

“…This paper is a continuation of the work published in papers focusing on the investigation and implementation of non-destructive condition monitoring (CM) techniques for low-voltage (LV) nuclear power plant (NPP) cables [1,2]. According to the latest report from the International Atomic Energy Agency (IAEA) [3], many NPPs are designed to operate for 30-40 years, with some evidence of aging being underestimated not only during original design but also during operation.…”

Feasibility Study on Online Diagnosis of Aging and Deterioration of Medium Voltage (MV) Three-Core Cable Based on Impedance Spectroscopy

“…Recently, insulation degradation analysis techniques such as Extended Voltage Response [16][17][18] and Polarization Depolarization Current [19][20] have also attracted attention. In [16], the relationship between the material properties and the voltage response measurement has been firstly presented.…”

“…In [17], the voltage response method has been developed by the systematic changing of the discharging times, which makes the method more precisely. In [18], the extended voltage response method has been used for the aging detection of low-voltage power cables, which shows a conclusive potential. In [19] and [20], the polarization and depolarization currents have been used as aging indicators for cables and show a good correlation.…”

Thermal aging management for electricity distribution networks: FEM-based qualification of underground power cables

“…The researchers and scientists have so far analyzed load diagrams [9,10], thermal IEC-based (analytical) models [9,10], and thermal FEM-based (numerical) models [11][12][13] of various power cables for the purposes of associated thermal aging management. The most frequently analyzed power cables are those with cross-linked polyethylene (XLPE) insulation, which have the expected total service lifespan of 40 years and which are not considered to be replaced or relocated during their designed lifespans [9,12,14,15]. Since the underground cable lines have limitations in terms of accessibility, visual and physical inspections, and applications of diagnosis techniques, it is crucial to estimate the condition of power cables and determine appropriate time for replacement or relocation of them [9,16,17].…”