scholarly journals Thermal Ageing of Power Cable Components Through Penetrations

2019 ◽  
Vol 19 (1) ◽  
pp. 36-42
Author(s):  
D. Puiu ◽  
B. Corbescu ◽  
C. Cepisca
Keyword(s):  
Temperature Increase ◽  
Laboratory Tests ◽  
Thermal Ageing ◽  
Power Cable ◽  
Power Cables ◽  
Temperature Influence ◽  
The Real ◽  
Service Conditions

AbstractThe power cables passing through penetration leads to growth of the thermal ageing mechanisms rate. The paper presents the results of the laboratory tests when the real environmental service conditions for penetration are simulated comparison with the result of the thermal computation of the power cables heating and of the temperature influence evaluation of temperature increase of the power cable components on the cable lifetime. For this particular case, a power cable with PVC insulation, we estimated a lifetime decrease about 20 years referring to lifetime (30÷40 years) for location in air.

scholarly journals Polyethylene Nanocomposites for Power Cable Insulations

Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 24 ◽  
Author(s):  
Ilona Pleşa ◽  
Petru Noţingher ◽  
Cristina Stancu ◽  
Frank Wiesbrock ◽  
Sandra Schlögl
Keyword(s):  
Electrical Performance ◽  
Power Cable ◽  
Power Cables ◽  
Structure Property ◽  
Thermoplastic Polymers ◽  
Water Tree ◽  
Tree Resistance ◽  
Structure Property Relationships ◽  
Aging Mechanisms ◽  
Comprehensive Study

This review represents a comprehensive study of nanocomposites for power cables insulations based on thermoplastic polymers such as polyethylene congeners like LDPE, HDPE and XLPE, which is complemented by original results. Particular focus lies on the structure-property relationships of nanocomposites and the materials’ design with the corresponding electrical properties. The critical factors, which contribute to the degradation or improvement of the electrical performance of such cable insulations, are discussed in detail; in particular, properties such as electrical conductivity, relative permittivity, dielectric losses, partial discharges, space charge, electrical and water tree resistance behavior and electric breakdown of such nanocomposites based on thermoplastic polymers are described and referred to the composites’ structures. This review is motivated by the fact that the development of polymer nanocomposites for power cables insulation is based on understanding more closely the aging mechanisms and the behavior of nanocomposites under operating stresses.

Failure Analysis of a Shaft Belonging to a Ship Engine Speed Controller

1999 ◽  
Author(s):  
Miguel V. Figueiredo ◽  
Fernando M. Oliveira ◽  
Paulo T. de Castro ◽  
António A. Fernandes
Keyword(s):  
Electron Microscopy ◽  
Fracture Surface ◽  
Failure Analysis ◽  
Laboratory Tests ◽  
Engine Speed ◽  
Notch Toughness ◽  
Severe Damage ◽  
Speed Controller ◽  
Service Conditions ◽  
Scanning Electron

Abstract The fracture of a shaft belonging to the speed controller of a ship’s engine is presented. An over-speed situation occurred as a result of the fracture of this shaft, which led to severe damage to the engine. The failure examination concentrated first on the study of the available evidence, which included the analysis of the shaft’s material and fracture surface. The shaft’s material was studied as concerns chemical composition, mechanical properties and micrographic structure. The fracture surface was studied using scanning electron microscopy. Several different destructive laboratory tests were conducted on the material, in order to obtain fracture surfaces which could be used for comparison purposes, and thus help to identify the cause of the fracture. The next step of the failure analysis consisted of a stress analysis of the shaft under service conditions. A probable scenario for the failure was proposed, which helped the interested parties to reach an agreement concerning responsibilities for the failure. It was found that the shaft material presented low notch toughness. The stress levels at the time of the accident imply that it is unlikely that the fracture was due to fatigue. The probable cause of the failure was sudden blockage of the shaft.

EFFICIENCY OR EFFECTIVENESS

PEDIATRICS ◽  
1975 ◽  
Vol 56 (2) ◽  
pp. 245-245
Author(s):  
R. J. H.
Keyword(s):  
Health Care ◽  
Medical Care ◽  
Laboratory Tests ◽  
Economies Of Scale ◽  
Utilization Review ◽  
The Real ◽  
Real Issue

The problem of rising costs of medical care has been attacked by two general methods: increased efficiency with business-like methods ("economies of scale," "managing the enterprise," etc.), and reducing use of the most expensive services-excessive hospitalization and laboratory tests—by utilization review. The second approach is more likely to be useful but still misses the real issue, i.e., how effective is what we do in medicine. As Drucker says, "It is effectiveness and not efficiency which the service institutions lack. Effectiveness can not be obtained by business-like behavior as the term is understood." If we could only set objectives, then determine how effectively we achieve them and concentrate our efforts in those areas where effectiveness has been demonstrated, we would have less emphasis on efficiency in health care.

Mechanism of Rubber Cracking

1946 ◽  
Vol 19 (2) ◽  
pp. 406-416 ◽  
Author(s):  
E. F. Powell ◽  
V. E. Gough
Keyword(s):  
Laboratory Tests ◽  
Surface Film ◽  
Factors Affecting ◽  
Laboratory Conditions ◽  
Service Conditions ◽  
Exposure Conditions

Abstract Rubber and rubberlike polymers, in common with other materials which deteriorate on exposure to oxidizing or similar agents, eventually crack under normal atmospheric service conditions. The present paper confines itself to the factors affecting the type and appearance of the cracking which eventually occurs when a surface film of a rubber object (particularly when stressed) hardens and deteriorates in strength from any cause whatsoever. The importance of an understanding of the effects of exposure conditions on the character of the cracking produced cannot be too highly emphasized. This is so even if interest is confined solely to simple tests on new protective paints on an acceptance basis rather than research into surface deterioration. It is probable that many protective agencies have been accepted or rejected for extensive production tests because the initial laboratory tests have either not been representative of service or have been inadequate in scope. This still remains a major problem. The theory presented here has gradually taken shape over a period of some ten years and appears to describe adequately the general findings on the whole gamut of cracking, viz., fine check cracking and isolated deep cracks produced under service and laboratory conditions, the latter covering flexing, roof exposure, ozone and similar tests.

scholarly journals Experimental Validation of a Heat Transfer Model in Underground Power Cable Systems

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1747 ◽  
Author(s):  
Paweł Ocłoń ◽  
Janusz Pobędza ◽  
Paweł Walczak ◽  
Piotr Cisek ◽  
Andrea Vallati
Keyword(s):  
Experimental Validation ◽  
Thermal Conditions ◽  
Test Stand ◽  
Temperature Fields ◽  
Transfer Model ◽  
Power Cable ◽  
Power Cables ◽  
Temperature Changes ◽  
Steady State Temperature ◽  
Underground Power Cable

This paper presents the laboratory test stand that is used for experimental validation of underground power cable system models. Determination of temperature distribution in the vicinity of the cable is the main goal of the study. The paper considers a system of three power cables, situated in the in-line arrangement, and buried in sand. Three electrical heaters of special construction are used in order to simulate the heat flux that is generated in the power cables during their operation. The test stand is designed to be placed in a thermoclimatic chamber, which allows testing the system in various thermal conditions when the ambient temperature changes by 20 °C to 30 °C. Numerical computations of the steady-state temperature fields are performed using the finite element method.

scholarly journals Thermal Ageing of XLPE Cable Insulation under Operational Temperatures – Does It Exist?

2018 ◽  
Author(s):  
Rasmus Olsen ◽  
Joachim Holboell ◽  
Mogens Henriksen ◽  
Jens Z. Hagen
Keyword(s):  
Power Systems ◽  
Elevated Temperatures ◽  
Thermal Ageing ◽  
Power Cables ◽  
Xlpe Cable ◽  
Practical Concern ◽  
Failure Statistics ◽  
Laboratory Investigations ◽  
Mind Set ◽  
Very High

<p>Thermal ageing of power cables may cause premature breakdown if the cables are operated at elevated temperatures, a relation usually described by Arrhenius’ law. The purpose of the present study is to investigate if any significant ageing takes place under normal operational temperatures. The investigation shows that thermal degradation at these comparably low temperatures is hardly reported and seems not to be of practical concern to transmission system operators. This may be the result of a conservative mind-set during the dimensioning of power systems, here in the case of power cables, which means that the lines are generally lightly loaded. Based on the literature found or, to be more precise, on the literature not found it seems to be very difficult to determine that thermal ageing should be problematic for operational power cables at all, in particular as compared to laboratory investigations at very high temperatures, where thermal ageing clearly takes place. To this conclusion contributes the fact that failure statistics do not correlate failures with severity of loading, and that the laboratory studies (which mosly conclude thermal ageing to be problematic) exposes the materials to unrealistic conditions.</p>

scholarly journals Study on the damage analysis of 110kV cable structure

2021 ◽  
Vol 243 ◽  
pp. 01006
Author(s):  
Zhitao He ◽  
Wen He ◽  
Haohui He ◽  
Junxuan Hong
Keyword(s):  
Structural Analysis ◽  
Structural Damage ◽  
Power Grid ◽  
Partial Discharge ◽  
Power Engineering ◽  
Power Cable ◽  
Power Cables ◽  
Engineering Construction ◽  
Cable Structure ◽  
Cable Damage

The market application value of power cables has gradually emerged with the development of various industries. Cable laying is a basic project in the construction of power grid and a key part of power engineering construction, and a key content of power engineering construction, which is related to the safe and reliable operation of the entire power grid. With the laying process of power cable, the metal sheath is subjected to structural damage such as extrusion deformation. This paper takes a 110kV cable line as an example, The case of cable damage was introduced in detail, and targeted measures were proposed based on the defects caused by the damage. At the same time, the structural analysis of the cable damage is carried out, and the structural analysis and simulation are performed, and the partial discharge test is performed on the damaged portion of the insulation to obtain the stress received when the cable is recessed, and the partial discharge signal detected by the damage of the insulating shielding layer is collected. Provide reference for staff related to power cables.

scholarly journals Denoising of Heavily Contaminated Partial Discharge signals in High-Voltage Cables Using Maximal Overlap Discrete Wavelet Transform

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6540
Author(s):  
Mohammed A. Shams ◽  
Hussein I. Anis ◽  
Mohammed El-Shahat
Keyword(s):  
Wavelet Transform ◽  
Discrete Wavelet Transform ◽  
High Voltage ◽  
Signal To Noise Ratio ◽  
Partial Discharge ◽  
Gaussian White Noise ◽  
Discrete Wavelet ◽  
Power Cable ◽  
Power Cables ◽  
Algorithm Performance

Online detection of partial discharges (PD) is imperative for condition monitoring of high voltage equipment as well as power cables. However, heavily contaminated sites often burden the signals with various types of noise that can be challenging to remove (denoise). This paper proposes an algorithm based on the maximal overlap discrete wavelet transform (MODWT) to denoise PD signals originating from defects in power cables contaminated with various levels of noises. The three most common noise types, namely, Gaussian white noise (GWN), discrete spectral interference (DSI), and stochastic pulse shaped interference (SPI) are considered. The algorithm is applied to an experimentally acquired void-produced partial discharge in a power cable. The MODWT-based algorithm achieved a good improvement in the signal-to-noise ratio (SNR) and in the normalized correlation coefficient (NCC) for the three types of noises. The MODWT-based algorithm performance was also compared to that of the empirical Bayesian wavelet transform (EBWT) algorithm, in which the former showed superior results in denoising SPI and DSI, as well as comparable results in denoising GWN. Finally, the algorithm performance was tested on a PD signal contaminated with the three type of noises simultaneously in which the results were also superior.

scholarly journals Particular properties of estimation of partial capacitances of insulation of three core power cables by applying aggregate measurements

2021 ◽  
pp. 15-20
Author(s):  
Ivan Kostiukov
Keyword(s):  
Root Mean Square Error ◽  
Mean Square Error ◽  
Root Mean Square ◽  
Least Squares Method ◽  
Power Cable ◽  
System Of Equations ◽  
Power Cables ◽  
Mean Square ◽  
Algebraic Equations ◽  
Linear Algebraic Equations

This paper presents a description of specific properties of determining the values of partial capacitances of insulation gaps in power cables with paper insulation for various ways of forming and solving the system of linear algebraic equations. Possible ways of inspection the insulation of three core power cables for the estimation of values of partial capacitances by applying aggregate measurements which are based on various ways of connection of emittance meter to tested sample of power cable are given. Estimation of partial capacitances by the direct solution of a system of linear algebraic equations, by minimizing the root mean square error of solving an overdetermined system of equations by the least squares method, as well as by finding a normal solution of an indefinite system of equations by the pseudo-inverse matrix, is also considered. It is shown that minimization of the root mean square error by the least squares method and the direct solution of system of equations show quite similar results for the case of estimation of partial capacitances by means of aggregate measurements, at the same time the solution of an indefinite system of equations by the method of a pseudo-inverted matrix allows to reproduce rather accurately only 3 out of 6 values of partial capacitances. The uneven effect of frequency on the electrical capacitance of the insulation gaps between the cores of the power cable and between its cores and the sheath is shown. It was proposed to use the frequency dependence of the electrical capacitance of insulation gaps as an informative parameter about the technical state of insulating gaps between the cores of the power cable and between its cores and its sheath.   Keywords: root mean square error; least squares method; system of linear algebraic equations; dielectric losses; dielectric permittivity.

scholarly journals A statistical method for stastical appraisal of the power cable conditions based on the TD and PD diagsnostics result

2019 ◽  
Vol 124 ◽  
pp. 02014
Author(s):  
T. Neier ◽  
J. Knauel ◽  
M. Bawart ◽  
D. Antipov ◽  
S. Kim
Keyword(s):  
Life Time ◽  
Distribution Networks ◽  
Power Cable ◽  
Practical Case ◽  
Power Cables ◽  
Remaining Life ◽  
Power Utilities ◽  
Underground Power Cables ◽  
Asset Managers

This study handles one of the key questions of network operators: How can the remaining life time of underground power cables be estimated? The answer to this question is explained by a new method of KEPCO Korea. When combining VLF Tan Delta (TD) and Partial Discharge (PD) diagnostic it is possible to identify and localize weak individual spots along a cable. After weak spots are cleared, the general aging condition of the cable can be evaluated and the Remaining Life Time can be estimated. The implementation of this approach in the KEPCO Distribution Networks is illustrated in a practical case study. A new tool for asset managers is available and it is expected that it will help to further develop the preventive maintenance approach by power utilities all around the world.

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