Use Of Crosslinked Polyethylene Research Articles

Quantitative Evaluation of Thermal Ageing State of Cross-Linked Polyethylene Insulation Based on Polarization and Depolarization Current

The widespread use of cross-linked polyethylene (XLPE) as insulation in cables may be attributed to its outstanding mechanical and dielectric properties. In order to quantitatively evaluate the insulation status of XLPE after thermal ageing, an accelerated thermal ageing experimental platform is established. Polarization and depolarization current (PDC) as well as elongation at break of XLPE insulation under different ageing durations are measured. XLPE insulation state is determined by the elongation at break retention rate (ER%). Based on the extended Debye model, the paper proposed the stable relaxation charge quantity and the dissipation factor at 0.1 Hz to evaluate the insulation state of XLPE. The results show that the ER% of XLPE insulation decreases with the growth of ageing degree. The polarization and depolarization current of XLPE insulation will increase obviously with thermal ageing. Conductivity and trap level density will also increase. The number of branches of the extended Debye model increases, and new polarization types appear. Stable relaxation charge quantity and dissipation factor at 0.1 Hz proposed in this paper have a good fitting relationship with ER% of XLPE insulation, which can evaluate the thermal ageing state of XLPE insulation effectively.

THE EFFECT OF SURGEON VOLUME ON REVISION FOR DEEP PERIPROSTHETIC JOINT INFECTION: AN ANALYSIS OF 602,919 PRIMARY TOTAL KNEE ARTHROPLASTIES

Deep infection is a devastating complication of total knee arthroplasty (TKA). This study aimed to determine if there was a relationship between surgeon volume and the incidence of revision for infection after primary TKA.Data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) from 1 September 1999 to 31 December 2020 for primary TKA for osteoarthritis that were revised for infection. Surgeon volume was defined by the number of primary TKA procedures performed by the surgeon in the year the primary TKA was performed and grouped as <25, 25-49, 50-74, 75-99, >100 primary TKA procedures per year. Kaplan Meir estimates for cumulative percent revision (CPR) and Cox Proportional Hazard Ratios were performed to compare rates of revision for infection by surgeon volume, with sub-analyses for patella and polyethylene use, age <65 years and male gender.5295 of 602,919 primary TKA for osteoarthritis were revised for infection. High volume surgeons (>100 TKA/year) had a significantly lower rate of revision for infection with a CPR at 1 and 17 years of 0.4% (95% CI 0.3, 0.4) and 1.5% (95% CI 1.2, 2.0), respectively, compared with 0.6% (95% CI 0.5, 0.7) and 2.1% (95% CI 1.8, 2.3), respectively, for low volume surgeons (<25 TKR/year). Differences between the high-volume group and the remaining groups remained when sub-analysis for age, gender, ASA, BMI, patella resurfacing and the use of cross-linked polyethylene (XLPE).High volume surgeons have lower rates of revision for infection in primary TKA.

Evaluation of cable moisture-proof measures based on AHP

With the widespread use of cross-linked polyethylene (XLPE) cables in the power system, the problem of aging due to moisture ingress of XLPE cables is becoming increasingly prominent. Under the humid laying environment, the XLPE cable sheath is easy to damage. The storage seal is improper or the water fill in the cable channel causes the XLPE cable to be immersed for a long time, which will seriously affect the insulation and service life of the cable. Therefore, it is important to establish a systematic evaluation system for moisture-proof measures of XLPE cables. This paper analyzes the reasons for the moisture of XLPE cables and the common moisture-proof measures. Based on the AHP method, comprehensively considers the impact of economy, technicality, applicability and feasibility, and establishes an evaluation system of cable moisture-proof measures. In the evaluation system, the criteria layer is subdivided into seven secondary indicators. For the plan layer, comprehensively consider the XLPE cable structure, cable materials, cable accessories and laying environment and other factors to select the XLPE cable moisture-proof measures for comparison. This paper uses AHP to figure out the comprehensive weight of each moisture-proof measure to the target layer, and the consistency test was conducted to prove the validity. The results have shown that the XLPE cable using water treeing resistant material in the plan layer has the best comprehensive effect. This paper provides a systematic and comprehensive evaluation system for future researches on cable moisture-proof measures, and the research results provide reference value for cable design and selection in the hot and humid areas.

Transfer of phthalates from c-polyvinyl chloride and cross-linked polyethylene pipe (PEX-b) into drinking water

Several different materials have been used for production of domestic water pipes throughout history. In recent years, the use of cross-linked polyethylene (PEX) pipe has increased dramatically, yet the potential for leaching of phthalates, which are endocrine disrupting compounds associated with adverse reproductive effects in humans, has not been examined. In this study, the potential of chlorinated polyvinyl chloride (cPVC) and red, blue, and heat PEX piping to leach phthalates into static hot and cold water after 2, 8, and 48 hours was evaluated. Concentrations of six phthalates, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), benzyl-butyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), and di(n-octyl) phthalate (DNOP), were determined by gas chromatography-mass spectrometry. Pipe type (F3,71 = 15.6, P = 0.001) contributed significantly to phthalate concentrations in water, while temperature (F4,71 = 1.74, P = 0.106) and time (F4,71 = 1.02, P = 0.427) were not significant factors. Significantly higher concentrations of DEP, DBP, and BBP were observed in cPVC pipe (<method detection limits (MDL) to 466 ng L−1, 252–4,219 ng L−1, 473–18,400 ng L−1, respectively) compared to blue PEX (T2 = 12.2, P < 0.001; <MDL, <MDL − 140 ng L−1, <MDL − 459 ng L−1, respectively), red PEX (T2 = 19.3, P < 0.001; <MDL, <MDL − 188 ng L−1, <MDL − 881 ng L−1, respectively), and heat PEX (T2 = 19.9, P < 0.001; <MDL, <MDL − 162 ng L−1, <MDL − 169 ng L−1, respectively). Phthalate exposure from drinking water via cPVC or PEX is low when compared to other dietary sources. Nonetheless, a shift from cPVC to PEX pipes in households would decrease potential exposure to phthalates.

Neural networks and fuzzy logic approaches to predict mechanical properties of XLPE insulation cables under thermal aging

The widespread use of cross-linked polyethylene (XLPE) as insulation in the manufacturing of medium- and high-voltage cables may be attributed to its outstanding mechanical and electrical properties. However, it is well known that degradation under service conditions is the major problem in the use of XLPE as cable insulation. Laboratory investigations of the insulations aging are time-consuming and cost-effective. To avoid such costs, we have developed two models which are based on artificial neural networks (ANNs) and fuzzy logic (FL) to predict the insulation properties under thermal aging. The proposed ANN is a supervised one based on radial basis function Gaussian and trained by random optimization method algorithm. The FL model is based on the use of fuzzy inference system. Both models are used to predict the mechanical properties of thermally aged XLPE. The obtained results are evaluated and compared to the experimental data in depth by using many statistical parameters. It is concluded that both models give practically the same prediction quality. In particular, they have ability to reproduce the nonlinear behavior of the insulation properties under thermal aging within acceptable error. Furthermore, our ANN and FL models can be used in the generalization phase where the prediction of the future state (not reached experimentally) of the insulation is made possible. Additionally, costs and time could be reduced.

Prediction of mechanical properties of XLPE cable insulation under thermal aging: neural network approach

The widespread use of Cross-linked Polyethylene (XLPE) as insulation in the manufacturing of medium and high voltage cables may be attributed to its outstanding mechanical and electrical properties. However, it is well known that degradation under service conditions is the major problem in the use of XLPE as insulation in cables. In order to reduce the aging experiments time, we have used Artificial Neural Networks (ANN) to predict the insulation properties. The proposed networks are supervised and non supervised neural networks. The supervised neural network was based on Radial Basis Function Gaussian (RBFG) and was trained with two algorithms: Backpropagation (BP) and Random Optimization Method (ROM). The non supervised neural network was based on the use of Kohonen Map. All these neural networks present good quality of prediction.

Space Charge Measurement on XLPE Cable for HVDC Transmission using PEA Method

Abstract The use of cross-linked polyethylene (XLPE) cables for High Voltage Alternating Current (HVAC) transmission has been successful in the world. However polymer insulated cables for High Voltage Direct Current (HVDC) transmission are still in development due to space charge build-up that occurs in cables under DC stress. Knowledge must be gained on the processes of charge build-up, including nature, kinetics and amount of accumulated charges, and on the consequences of charge accumulation regarding field distribution in the insulation. One way to determine the space charge distribution in XLPE cables for HVDC transmission non-destructively is the Pulse Electro Acoustic (PEA) method, a direct method for measuring space charge distribution in dielectric materials. The PEA method was chosen because it is suitable for a wide range of sample geometry (thin and thick samples), and is available for cable geometry. The present contribution concerns space charge distribution measurements in sections of HVDC model cables. To account for the situation of cables in service, measurements were performed with a temperature gradient across the insulation thickness, and this could be achieved by heating through the cable conductor. Measurements performed on XLPE insulated model cables with 4.5 mm insulation thickness were realized with -40 kV DC applied for 150 minutes. Injecting a current of 200A in the conductor produced theoretically a temperature gradient of 8 °C between the core and the outer face of the cable, with a surface temperature of the cable of 50 °C. A deconvolution procedure, wherein attenuation, dispersion and cylindrical geometry are accounted for, was used to recover space charge profiles at different times under stress. It is shown that considerable field redistribution occurs within the cable, compared to the Laplacian field distribution predicted in cylindrical geometry, due in part to the conductivity gradient associated with the thermal gradient, and for the other part to charge build-up occurring within the cable.

Effects of Harmonics on Power Loss in XLPE Cables

Harmonics in power systems is increasingly at high level. Also, there has been an incredible growth in the use of cross linked polyethylene (XLPE) cables in distribution systems. Harmonics cause additional power loss/temperature rise; causing premature failure of cables. Catastrophic failure of power cables leads to great inconvenience to consumers and loss of system reliability and money. To avoid the overheating of power cables; the additional power loss due to harmonics should be accurately calculated and properly accommodated by derating the cable. The present method of calculating the power loss in cables in harmonics rich environment is very arduous. The aim of this paper is to present the reasonably accurate method for evaluating effects of harmonics on the power loss in XLPE cables. Computational model is developed in MATLAB for power loss calculation using conventional method. Using this model, calculations are performed for aluminium and copper conductor XLPE cables of different size and type; for three different types of harmonics spectrums having total harmonics distortion (THD) of 30.68%, including all odd harmonics components up to 49th order. Using these results; a mathematical model in the form of simple empirical formula is developed by curve fitting technique. The results obtained by various models are presented and compared with error justification.

Cross-linkedversusconventional polyethylene for total hip replacement

We conducted a systematic review and meta-analysis of randomised controlled trials comparing cross-linked with conventional polyethylene liners for total hip replacement in order to determine whether these liners reduce rates of wear, radiological evidence of osteolysis and the need for revision. The MEDLINE, EMBASE and COCHRANE databases were searched from their inception to May 2010 for all trials involving the use of cross-linked polyethylene in total hip replacement. Eligibility for inclusion in the review included the random allocation of treatments, the use of cross-linked and conventional polyethylene, and radiological wear as an outcome measure. The pooled mean differences were calculated for bedding-in, linear wear rate, three-dimensional linear wear rate, volumetric wear rate and total linear wear. Pooled risk ratios were calculated for radiological osteolysis and revision hip replacement. A search of the literature identified 194 potential studies, of which 12 met the inclusion criteria. All reported a significant reduction in radiological wear for cross-linked polyethylene. The pooled mean differences for linear rate of wear, three-dimensional linear rate of wear, volumetric wear rate and total linear wear were all significantly reduced for cross-linked polyethylene. The risk ratio for radiological osteolysis was 0.40 (95% confidence interval 0.27 to 0.58; I(2) = 0%), favouring cross-linked polyethylene. The follow-up was not long enough to show a difference in the need for revision surgery.

Wear, Debris, and Biologic Activity of Cross-linked Polyethylene in the Knee

Cross-linked polyethylene currently is being introduced in knee prostheses. The wear rates, wear debris, and biologic reactivity of non cross-linked, moderately cross-linked, and highly cross-linked polyethylene have been compared in multidirectional wear tests and knee simulators. Multidirectional pin-on-plate wear studies of noncross-linked, moderately cross-linked (5 Mrad), and highly cross-linked (10 Mrad) polyethylene showed a 75% reduction in wear with the highly cross-linked material under kinematics found in the hip, but only a 33% reduction under wear in kinematics representative of the knee. In knee simulator studies, with the fixed-bearing press-fit, condylar Sigma cruciate-retaining knee under high kinematic input conditions, the wear of 5 Mrad moderately cross-linked polyethylene was 13 +/- 4 mm per 1 million cycles, which was lower (p < 0.05) than the wear of clinically used, gamma vacuum foil GUR 1020 polyethylene (23 +/- 6 mm/1 million cycles). For the low-contact stress mobile-bearing knee, the wear of moderately cross-linked polyethylene was 2 +/- 1 mm per 1 million cycles, which was lower (p < 0.05) than GVF GUR 1020 polyethylene (5 +/- 2 mm/1 million cycles). The wear debris isolated from the fixed-bearing knees showed the moderately cross-linked material had a larger percentage volume of particles smaller than 1 mum in size, compared with GVF GUR 1020 polyethylene. Direct cell culture studies of wear debris generated in sterile wear simulators using multidirectional motion showed a increase (p < 0.05) in tumor necrosis factor-alpha levels and reactivity for GUR 1050 cross-linked polyethylene debris compared with an equivalent volume of noncross-linked GUR 1050 polyethylene. The use of cross-linked polyethylene in the knee reduces the volumetric wear rate. However, the clinical significance of reduced fracture toughness, elevated wear in abrasive conditions, and the elevated tumor necrosis factor-alpha release from smaller more reactive particles warrant further investigation.