A study of expected lifetime of XLPE insulation cables working at elevated temperatures by applying accelerated thermal ageing

Related factors of perioperative low body temperature and incidence of postoperative shivering in patients undergoing complex percutaneous nephrolithotomy and the effect analysis of composite insulation nursing intervention

This study aimed to analyze the factors associated with intraoperative hypothermia and postoperative shivering rates in patients undergoing complex percutaneous nephrolithotomy (PCNL) and investigate the effects of combined insulation nursing intervention. A total of 168 patients were included, with 103 patients in the control (Ctrl) group receiving routine care and 65 patients in the nursing (Nur) group receiving combined insulation nursing intervention measures. General information, surgical data, temperature, intraoperative hypothermia incidence, postoperative shivering, and complication rates were statistically analyzed between the two groups. Patient temperature, blood pressure, and blood gas indicators including pH value, bicarbonate, and lactate levels were recorded at admission (T0), before anesthesia (T1), 30 min after spinal-epidural combined anesthesia (T2), 60 min (T3), 90 min (T4), 120 min (T5), and postoperatively (T6). The results demonstrated that the average intraoperative temperature of patients in the Nur group was significantly higher than that of the Ctrl group (P < 0.001), and their incidence of hypothermia was significantly lower than that of the Ctrl group (P < 0.01). Additionally, the Nur group exhibited shorter recovery time (18.36 ± 3.58 min), extubation time (28.01 ± 3.12 min), and length of hospital stay (8.45 ± 2.14 days) compared to the Ctrl group (P < 0.05). The incidence of postoperative shivering was 4.62 %, significantly lower than that of the Ctrl group (P < 0.001). Multifactorial analysis revealed that age ≥60 years, stone diameter ≥3.0 cm, irrigation volume ≥3000 mL, nursing intervention measures, and surgical duration were the main factors influencing the occurrence of intraoperative hypothermia. Age ≥60 years, nursing intervention measures, surgical duration, and intraoperative temperature<36 °C are identified as major risk factors for postoperative shivering. This indicates that specialized nursing care and combined insulation nursing intervention measures in patients undergoing complex percutaneous nephrolithotomy contribute to reducing the incidence of intraoperative hypothermia and postoperative shivering. It is recommended to promptly address the risk factors associated with hypothermia and shivering during and after surgery to mitigate the risk of perioperative complications.

Diagnosis and Location of Power Cable Faults Based on Characteristic Frequencies of Impedance Spectroscopy

Power cable condition diagnosis and deterioration location rely on signatures of aging characteristics which precede the final breakdown. The purpose of this study was to investigate how to diagnose and locate the aging and/or deterioration of power cables through the analysis of the impedance spectroscopy. The concepts of the reference frequency and characteristic frequency of cable impedance spectroscopy are defined for the first time. Based on the reference frequency, the optimal frequency range for analysis of impedance spectroscopy can be determined, whilst based on characteristic frequency, a set of criteria for assessing cable conditions are examined and established. The solution proposed in this paper has the advantage of being easier to implement than the previously reported “broadband” impedance spectroscopy methods, as it helps to reduce the frequency range for measurement instrumentations; the proposed method also does not need the measurements of the parameters of the cable being tested.

Highly insulating thermoplastic nanocomposites based on a polyolefin ternary blend for high-voltage direct current power cables

Octyl-silane-coated Al₂O₃ nanoparticles are found to be a promising conductivity-reducing additive for thermoplastic ternary blends comprising low-density polyethylene (LDPE), isotactic polypropylene and a styrenic copolymer. The ternary blend nanocomposites were prepared by compounding the blend components together with an LDPE-based masterbatch that contained the nanoparticles. The nanoparticles did not affect the superior stiffness of the ternary blends, compared to neat LDPE, between the melting temperatures of the two polyolefins. As a result, ternary blend nanocomposites comprising 38 wt% polypropylene displayed a storage modulus of more than 10 MPa up to at least 150 °C, independent of the chosen processing conditions. Moreover, the ternary blend nanocomposites featured a low direct-current electrical conductivity of about 3 × 10^-15 S m^-1 at 70 °C and an electric field of 30 kV mm^-1, which could only be achieved through the presence of both polypropylene and Al₂O₃ nanoparticles. This synergistic conductivity-reducing effect may facilitate the design of more resistive thermoplastic insulation materials for high-voltage direct current (HVDC) power cables.

Reliability degradation prediction of photovoltaic modules based on dependability methods

Purpose

The reliability prediction is among the most important objectives for achieving overall system performance, and this prediction carried out by anticipating system performance degradation. In this context, the purpose of this research paper is to development of methodology for the photovoltaic (PV) modules' reliability prediction taking into account their future operating context.

Design/methodology/approach

The proposed methodology is framed by dependability methods, in this regard, two methods of dysfunctional analysis were used, the Failure Mode and Effects Criticality Analysis (FMECA) method is carried out for identification of the degradation modes, and the Fault Tree Analysis (FTA) method is used for identification the causes of PV modules degradation and the parameters influencing its degradation. Then, based on these parameters, accelerated tests have been used to predict the reliability of PV modules.

Findings

The application of the proposed methodology on PWX 500 PV modules' in different regions of Algeria makes it possible to predict its reliability, taking into account the future constraints on its operation. In this case, the temperature and relative humidity vary from one region to another was chosen as constraints. The results obtained from the different regions confirms the reliability provided by the designer of the Saharan cities Biskra, In Salah, Tamanraset, and affirms this value for the two Mediterranean cities of Oran and Algiers.

Originality/value

The proposed methodology is developed for the reliability prediction of the PV modules taking into account their future operating context and, the choice of different regions confirms or disproves the reliability provided by the designer of the PV modules studied. This application confirms their performance within the framework of the reliability prediction.

Demand Response Coupled with Dynamic Thermal Rating for Increased Transformer Reserve and Lifetime

(1) Background: This paper proposes a strategy coupling Demand Response Program with Dynamic Thermal Rating to ensure a transformer reserve for the load connection. This solution is an alternative to expensive grid reinforcements. (2) Methods: The proposed methodology firstly considers the N-1 mode under strict assumptions on load and ambient temperature and then identifies critical periods of the year when transformer constraints are violated. For each critical period, the integrated management/sizing problem is solved in YALMIP to find the minimal Demand Response needed to ensure a load connection. However, due to the nonlinear thermal model of transformers, the optimization problem becomes intractable at long periods. To overcome this problem, a validated piece-wise linearization is applied here. (3) Results: It is possible to increase reserve margins significantly compared to conventional approaches. These high reserve margins could be achieved for relatively small Demand Response volumes. For instance, a reserve margin of 75% (of transformer nominal rating) can be ensured if only 1% of the annual energy is curtailed. Moreover, the maximal amplitude of Demand Response (in kW) should be activated only 2–3 h during a year. (4) Conclusions: Improvements for combining Demand Response with Dynamic Thermal Rating are suggested. Results could be used to develop consumer connection agreements with variable network access.