Low-Cost Monitoring Unit for MV Cable Joints Diagnostics

et al. 2019

The use of medium voltage cable joints is mandatory when dealing with power cable faults and the installation of new lines. However, such an accessory is among the top causes of faults among the grid. To this purpose, one of the quantities monitored to understand the causes of such faults is the interfacial pressure between the insulating layers of the cable joint. In this work, the interfacial pressure between Cross-linked polyethylene (XLPE) and silicon rubber has been evaluated when the cable joint experiences thermal cycles. From the results, the pressure variation caused by the thermal cycles is demonstrated. Such a phenomenon may be connected to the generation of voids and weak spots that accelerate cable joint ageing. Therefore, proper comments and conclusions are drawn.Sensors 2020, 20, 169 2 of 13 delta at ambient temperature. The same setup is then used to perform measurements in the 5-60 • C temperature range [25]. The experiments demonstrated a relationship between the temperature and the tangent delta, affecting the cable joint service life. In [26,27], different Tanδ extraction methods are presented.The pressure between the insulating elements and the cable joint is also believed to affect the insulation effectiveness provided by the cable joint. The selection of materials plays a relevant role in this respect [28]. A method is available in literature to calculate and simulate the surface pressure [29]. The correlation between the interfacial pressure and tangent delta has been explored in [30]. The variation of the interfacial pressure with the ambient temperature was also investigated [31].As for the PD, they are considered by several experts to be an effective method to assess the "healthy" status of the cable joints. Therefore, literature provides a high number of studies on this topic. For example, new PD extraction and analysis methods are presented in [32,33], while an on-line measurement setup is described in [34]. Based on these works [30,31], a correlation between the three physical parameters involved can be established.In light of the above mentioned, the aim of this paper is to measure and evaluate the interfacial pressure between XLPE and SR when subject to thermal cycles. Such cycles aim at reproducing the ambient temperature variations that a cable joint suffers during its working life. From the results, compared also with the current literature, it can be appreciated a typical behavior, due in this case by the thermal cycles, that is cause of ageing acceleration of cable joints (as detailed below).The paper is structured as follows. In Section 2 the measurement setup and the details of its elements are described. The experimental tests are described in Section 3, while Section 4 is dedicated to the results analysis and comparison with consistent literature. In Section 5, comments on the obtained results and conclusion are drawn.

Section: Description Of the Experimental Testsmentioning

confidence: 99%

“…A given type of joint must exhibit good thermal performance [15][16][17] since this capability is related to cable ampacity. Different sensing systems have been proposed for continuous temperature monitoring in cable joints [18][19][20][21] and to be able to plan predictive maintenance.…”

Section: Introductionmentioning

confidence: 99%

Effects of Thermal Cycles on Interfacial Pressure in MV Cable Joints

Sante

Ghaderi

et al. 2019

“…Furthermore, its large bandwidth makes it suitable for different high frequency applications [ 31 , 32 , 33 ]. Instead, in [ 34 , 35 , 36 , 37 , 38 ] the authors present several applications where the Rogowski coil is implemented to perform diagnostic and predictive maintenance measurements (for cable joints, motors, feeders, onsite calibration, etc.).…”

Section: Introductionmentioning

confidence: 99%

Smart Characterization of Rogowski Coils by Using a Synthetized Signal

Peretto

Tinarelli

2020

With the spread of new Low-Power Instrument Transformers (LPITs), it is fundamental to provide models and characterization procedures to estimate and even predict the LPITs’ behavior. In fact, distribution system operators and designers of network models are looking for all forms of information which may help the management and the control of power networks. For this purpose, the paper wants to contribute to the scientific community presenting a smart characterization procedure which easily provides sufficient information to predict the output signal of a Low-Power Current Transformer (LPCT), the Rogowski coil. The presented procedure is based on a synthetized signal applied to the Rogowski coil. Afterwards, the validity of the procedure is assessed within the Matlab environment and then by applying it on three off-the-shelf Rogowski coils. Simulations and experimental tests and results involving a variety of distorted signals in the power quality frequency range and by adopting a quite simple measurement setup demonstrated the effectiveness and the capability of the procedure to correctly estimate the output of the tested device.

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Peretto

Tinarelli

2020

Power quality is a wide-ranging and current topic that involves a huge effort from the scientific community. Power quality issues have to be avoided or solved in order to preserve the integrity of the network and its assets. To this purpose, several power quality indexes and measurement techniques have been developed and used by experts. This paper aims at solving the issue of having an uncertainty associated to the total harmonic distortion (THD) measurements. The idea is to obtain a close-form expression, which only requires the knowledge of the instrument transformer accuracy class, to estimate the mean value and the variance of THD. After the development of such an expression, it has been tested and stressed to confirm its effectiveness and applicability in a variety of conditions, and for harmonics up to 25th (of 50 Hz), defined by the standards.