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

In a nuclear power plant environment, low-voltage cables experience different stresses during their service life which challenge their integrity. A non-destructive and reliable condition monitoring technique is desired to determine the state of these low-voltage cables during service and for the life extension of nuclear power plants. Hence, in this research work, an EPR/CSPE-based low-voltage cable was exposed to γ-rays for five different absorbed doses. The overall behavior of the cable under stress was characterized by frequency and time domain electrical measurements (capacitance, tan δ, and Extended Voltage Response) and a mechanical measurement (elongation at break). Significant variations in the electrical parameters were observed, as was a decline in the elongation at break values. A strong correlation between the measurement methods was observed, showing the ability of the electrical methods to be adopted as a non-destructive condition monitoring technique.

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Condition Assessment of Low Voltage Photovoltaic DC Cables under Thermal Stress Using Non-Destructive Electrical Techniques

Transactions on Electrical and Electronic Materials ◽

10.1007/s42341-020-00201-3 ◽

2020 ◽

Vol 21 (5) ◽

pp. 503-512

Author(s):

Ehtasham Mustafa ◽

Ramy S. A. Afia ◽

Zoltán Ádám Tamus

Keyword(s):

Thermal Stress ◽

Condition Monitoring ◽

Low Voltage ◽

Research Work ◽

Diagnostic Methods ◽

Voltage Response ◽

Insulation Material ◽

On Line ◽

Non Destructive ◽

Line Condition

Abstract The output power of the photovoltaic system is heavily dependent on the low voltage (LV) DC cables which are exposed to multiple stresses such as climatic, mechanical, electrical, and thermal stress, hence makes them more exposed to aging as compared to other components in the system. Accordingly, it is essential to monitor the state and know the real cause of the insulation degradation of the cable. The physio-chemical changes inside the insulation during service is attributed to the thermal stress, which the cable has to endure constantly. Traditionally, destructive test techniques have been adopted to study the aging phenomenon in the cable insulation, making them unsuitable for on-line condition monitoring. This research work has been aimed to study the degradation in LV photovoltaic DC cables under thermal stress by measuring the dielectric properties; complex permittivity, tanδ with the change in frequency and decay and return voltage slopes using extended voltage response method. The non-destructive diagnostic methods used are based on the phenomenon of polarization and conduction in the insulation material. The noteworthy change in the values of the imaginary part of permittivity, tanδ at low frequencies, and the overall decrease in the values of return voltage slope showed the change in the structure of the polymer matrix under the stress which was related to the cross-linking based chemical reactions. The results show that the techniques can be adopted for the on-line condition monitoring of the cable for the PV system and the dielectric parameters can be used to study the chemical and physical changes happening inside the material effectively.

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Aging Mechanisms and Non-Destructive Aging Indicators of XLPE/CSPE Unshielded LV Nuclear Power Cables Subjected to Simultaneous Radiation-Mechanical Aging

Polymers ◽

10.3390/polym13183033 ◽

2021 ◽

Vol 13 (18) ◽

pp. 3033

Author(s):

Ramy S. A. Afia ◽

Ehtasham Mustafa ◽

Zoltán Ádám Tamus

Keyword(s):

Mechanical Properties ◽

Nuclear Power ◽

Power Plants ◽

Low Voltage ◽

Voltage Response ◽

Power Cables ◽

Mechanical Parameters ◽

Electrical Parameters ◽

Cable Systems ◽

Non Destructive

Low-voltage cable systems in nuclear power plants are key components that have a crucial role in the safe operation of nuclear facilities. Thus, the aging management of cable systems is of utmost importance as they cannot easily or economically be replaced or upgraded. Therefore, there is a continuous need to develop reliable non-destructive condition monitoring techniques, mostly based on the measurement of the dielectric properties of cable insulation. This paper introduces the changing of dielectric and mechanical properties of XLPE insulated and CSPE jacketed unshielded low-voltage nuclear power plant power cable in case of simultaneous mechanical and radiation aging. The cable samples were bent and exposed to 400 kGy gamma irradiation with a 0.5 kGy/hr dose rate. Dielectric response (real and imaginary permittivity) in the 0.1 Hz−1 kHz frequency range, extended voltage response (EVR), and the Shore D hardness test techniques were measured to track aging. The electrical and mechanical parameters have increased monotonically with aging, except the imaginary permittivity, which increased only at frequencies higher than 10 Hz. Furthermore, different quantities were deducted based on the frequency and permittivity data. The electrical parameters and deducted quantities correlation with aging and mechanical parameters were investigated. Since the deducted quantities and the electrical parameters are strongly correlated with absorbed dose and mechanical properties, the electrical measurements can be applied as a non-destructive aging indicator for XLPE/CSPE unshielded low-voltage nuclear power cables.

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Electrical condition monitoring techniques for low-voltage cables used in nuclear power plants

2013 IEEE Electrical Insulation Conference (EIC) ◽

10.1109/eic.2013.6554299 ◽

2013 ◽

Cited By ~ 6

Author(s):

L. Verardi ◽

D. Fabiani ◽

G. C. Montanari ◽

Pavel Zak

Keyword(s):

Condition Monitoring ◽

Nuclear Power ◽

Power Plants ◽

Nuclear Power Plants ◽

Low Voltage ◽

Monitoring Techniques ◽

Electrical Condition

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Analysis of the Degradation Tendency of NPP Cables Using a Wireless Cable Indenting Robot

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.284-287.1749 ◽

2013 ◽

Vol 284-287 ◽

pp. 1749-1753

Author(s):

Kyung Nam Jang ◽

Jong Soeg Kim ◽

Sun Chul Jeong ◽

Kyung Heum Park ◽

Sung Yull Hong

Keyword(s):

Power Plant ◽

Nuclear Power Plant ◽

Condition Monitoring ◽

Nuclear Power ◽

Power Plants ◽

Accelerated Aging ◽

Test Equipment ◽

Testing Time ◽

Operation Period ◽

Non Destructive

In nuclear power plants, there are many cables that perform safety-related functions. These cables should implement condition monitoring during the operation period in the nuclear power plant, in order to assess the remaining qualified life and extend the qualified life. In this study we focused on the indenting method which can measure the hardness of the cable jacket. This method is selected because it is non-destructive and requires short testing time and small sized equipment. In order to address the problems with the existing indenting test equipment, we developed new indenting test equipment, which could automatically move on the surface of the object cable. The newly developed equipment is designed for a small-sized and light-weight robot using wireless communication in order to implement condition monitoring in a harsh environment or locations that are inaccessible to the tester. The developed wireless cable indenting robot is composed of three parts, which are mechanical and electrical hardware parts and remote-control part. In order to analyze the degradation tendency of the cable, we prepared four thermally aged specimens and one un-aged specimen. Using the developed robot, we measured the modulus of the cable jacket of each specimen. The test data showed that the modulus of the cable jacket increased linearly as the accelerated aging time increased. From these results, we can analyze the degradation trends pertaining to cables installed in nuclear power plant according to the operation period.

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Nuclear Power Plant Instrumentation and Control Cable Prognostics Using Indenter Modulus Measurements

International Journal of Prognostics and Health Management ◽

10.36001/ijphm.2015.v6i3.2261 ◽

2020 ◽

Vol 6 (3) ◽

Author(s):

Dan McCarter ◽

Brent Shumaker ◽

Bryan McConkey ◽

Hash Hashemian

Keyword(s):

Condition Monitoring ◽

Nuclear Power ◽

Power Plants ◽

Accelerated Aging ◽

Remaining Useful Life ◽

Test Bed ◽

Efficient Operation ◽

To Come ◽

And Control ◽

Non Destructive

As the fleet of nuclear power plants (NPPs) approach their1 original qualified life (typically 40 years) and operators seek license extensions, regulators require assurance that they can continue to operate safely in the decades to come. Some of the most important, yet often overlooked components, are the cables that provide the signal paths for instrumentation and control (I&C) systems used to ensure safe and efficient operation of NPPs.In response to this, the authors explore the use of expanding indenter modulus (IM), an industry-accepted technique for cable condition monitoring, into a prognostic tool for predicting the remaining useful life (RUL) of I&C cables. Not only is this technique non-destructive, but it can be performed while NPP cables are in service, thus making it practical for adoption into existing cable condition monitoring programs. In this paper, the authors describe an accelerated aging cable test bed used to acquire several types of measurement parameters as cables age. Additionally, practical techniques are described in which simple IM measurements can be leveraged for condition monitoring and RUL estimation.Error analysis indicates the proposed method is superior to conventional RUL estimation techniques, such as simple trending and curve fitting. The authors demonstrate that using IM can potentially provide a non-destructive, in-situ estimation of RUL for I&C cables. As described in this paper, the IM data clearly shows trends as a function of cable age, and shows promising performance for RUL estimation especially compared with conventional techniques.

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