Service Life Of Cables Research Articles

Method of calculation of temperature parameters and service life of 10 kv cable lines

This study is based on the analysis of the methodology for calculating the temperature parameters of 10 kV cable lines and calculating the service life of insulation under various operating conditions, as well as identifying dependencies that allow the most accurate selection of cable parameters during operation at industrial facilities. The results of the study can be used to improve the energy efficiency of enterprises, and contribute to reducing the number of emergency failures of cable lines that may occur due to thermal breakdowns caused by incorrect choice of cable parameters under certain operating conditions, which may cause an increase in production costs in general. Conducting research and calculations of temperature parameters of cable lines at a voltage of 10 kV with different laying methods and with different capacity factors according to the climatology of the Republic of Tatarstan, as well as identifying key dependencies that will enable to draw appropriate conclusions on the operation of cables in the conditions under consideration. The article uses methods for calculating temperature parameters and cable service life, as well as methods for processing the data obtained as a result of calculations, including the method of function approximation. Special software is also used to visualize the results obtained after the calculations. The results of calculations of temperature parameters of 10 kV cable lines for various laying methods, with different types of insulation and with different capacity factors according to climatology of the Republic of Tatarstan are presented. Calculations of the service life of cable lines under the conditions under study have been made and conclusions have been drawn on optimal cable loads that will not lead to premature thermal aging of insulation under certain operating conditions. The initial data for the calculations and the methodology used comply with GOST standards for cable lines. The results of the study and the calculations performed can be used to evaluate and select the optimal load of cable lines under selected conditions at the design stage of power supply systems.

Study on temperature rise characteristics of 110 kV XLPE cable under different service years considering dielectric loss

This paper studies temperature rise characteristics of 110 kV XLPE cable under different service years. When the load is 900 A, the maximum temperature of the cable under 0, 15 and 30 service years is 335.5 K, 372.96 K and 393.88 K respectively. Compared with the data obtained from non-aged cable, the temperature increase for samples operating for 15 and 30 years is 111.15% and 117.4% higher. For these samples, the proportion of heating due to cable dielectric loss is 2.77%, 25.45% and 34.78%. The research content of this paper provides a basis for the research on the optimal current carrying capacity of cables with different service years, provides a reference for the actual application of cables, and has guiding significance for the research on prolonging the service life of cables and improving the utilization rate of cable resources.

Prevention of emergency malfunctions

The article discusses the most common type of malfunctions and the main causes of damage to the electrical cable. A case study of cable failures in the urban network shows that the main cause is the deterioration of insulation, especially due to the fact that the service life of cables reaches 35 years. Therefore, in order to prevent failures and reduce threats, it is necessary to strengthen the monitoring of cable systems and use cables with higher reliability and functionality, for instance, cables made of cross-linked polyethylene.

Aging of Cross-Linked Polyethylene Insulation Cable Lines

Abstract. Preference is given to cable lines with cross-linked polyethylene insulation in electrical networks with a nominal voltage of 10 kV during reconstruction of existing and construction of new industrial enterprises. The standard service life of such cables is at least 30 years (subject to the conditions of storage, transportation, installation and operation), and the actual one is determined by the technical condition of the cable. The service life of a cable line depends on the state of its insulation, the aging of which occurs under the influence of several factors. Conventionally, all factors influencing one or another degree on the cable insulation resource can be divided into thermal, electromagnetic, climatic, mechanical and operational. The most significant reason for the insulation aging is high temperature, which accelerates the reaction of thermo-oxidative destruction, during which high-molecular polymer compounds decompose. In fact, cables are operated at temperatures below the long-term permissible values, and, therefore, the aging of the insulation is slower, and the actual service life will be longer than the standard. At present, condition of the insulation is monitored with the use of high voltage tests related to destructive testing methods. When designing and operating cable lines, it is necessary to estimate the duration of the actual service life under various operating conditions. In theory, there are several expressions for calculating the service life of a cable line when exposed to temperature, humidity, electric field and aggressive environments, but all of them are not applicable in practice due to the presence of a large number of coefficients whose values are unknown. The paper presents an analytical expression obtained for determining the service life of power electric cables, taking into account the aging of the insulation under the influence of temperature and electric field.

The estimation of ship cable condition by the means of measuring its insulation characteristics

Timely detection of defects in electrical equipment and cable network is required for the ensuring the fire safety of a modern marine vessel. The method of continuous monitoring of the resistance value of cable insulation is not very informative and is not applicable for assessing the service life of cables and predicting their replacement during operation and repair. Currently the problem of developing modern non-destructive methods of insulation control is very urgent in order to determine the operability of the cable, search for diagnostic parameters characterizing the state of insulation during prolonged aging, as well as the introduction of traditional methods of diagnostics of electrical equipment that have shown their effectiveness at the facilities of the coastal infrastructure. A promising solution for this problem is a method for monitoring the values of the tangent of the dielectric loss angle tgδ of cable insulation using devices that allow registering parameters with high accuracy. In this study the determination of changes in the parameters of a ship cable subjected to accelerated thermal aging at temperatures 120-130 °C has been made. The tgδ measurements of the cable sheath have been carried out using the Tangent-2000 insulation meter. The tests have shown that aging of cable hose insulation is accompanied by a non-linear change in tgδ; at certain values of the tangent of dielectric loss angle, visible cracks appear indicating the onset of an emergency condition of the cable. The nature of the change in the parameter tgδ is explained by the occurrence of reactions of oxidative dehydrochlorination of polychloroprene in the process of thermal aging of insulation and changes in its mass. Thus, the tangent of the dielectric loss angle can be one of the diagnostic parameters for assessing the state of the insulation of the ship's cable and predicting its service life.

Partial Discharge Experimental Study for Medium Voltage DC Cables

Medium voltage dc (MVDC) distribution is a promising solution for many applications such as transportation electrification, city centers, oil and gas platforms, and renewable energy collection systems. Compared to ac, a MVDC system can significantly improve power density, energy efficiency, and controllability. Weight and size of power equipment are limiting factors in transportation electrification, and cables usually take up a large space in a power system. A focus of this research is to investigate the potential of dc supply to reduce cable size without compromising cable service life. Since partial discharges (PD) in internal voids have been identified as a major source for power equipment premature failure, it is critical to understand PD mechanisms of medium voltage cables under both ac and dc, especially PD from internal void and delamination. This paper presents PD experimental data from medium voltage cables and test coupons to show that dc supply could be a more favorable condition for cables than ac.

Experimental study on cable rejuvenation via simulated cable operation

To extend the cable service life, the feasibility of cable rejuvenation on two retired cables through heat treatment was investigated in this study. First, two retired 110 kV AC cables without overheated record were annealed at four temperatures of 90, 95, 100, and 105 °C by simulating the cable operation. Second, the insulation layer of the annealed cables was peeled, and the peels near the inner conductor were selected as test samples. Then, differential scanning calorimetry was performed, and the DC conduction current and dielectric breakdown strength E B were measured. The results showed that the heat treatment of simulating cable operation could be a feasible method to rejuvenate retired cables and 95 °C was determined to be the optimum annealing temperature for the two cables.

Ageing Analysis of Power Cable used in Nuclear Power Plant

The aim of nuclear power plant ageing management and assessment is to maintain an adequate safety level throughout the life time of the plant and helps in determining the useful operation. Various factors involved in the insulation of polymeric cables such as continuous heat, radiation and atmosphere result in the alteration of chemical and physical properties as well as lowers the service life of material. PVC (Poly Vinyl Chloride) is the most commonly used insulation material in NPP (Nuclear Power Plant). Purpose of this work is to predict the service life of PVC insulation cable for which extrapolation ageing has been performed. Ageing mechanism proceeds in laboratory scale rig to provide temperature and radiation sources. The variation in temperature is regulated and monitored through thermocouple. At higher temperature, semi crystalline free radical may escape out resulting in the degradation of polymer. Different tests have been carried out like shore hardness testing, tensile testing, Differential Scanning Calorimeter and Thermo gravimetric Analysis before and after ageing to analyze the Ageing effect. The impact of ageing days upon yield strength of single stress ageing has been carried out in this research work and it is found that aging has significant effect on service life of cables used in power plants.

Main Approaches to Cable Aging Management at Nuclear Power Plants in Ukraine

The mechanisms of cable ageing at nuclear power plants (NPPs) mainly depending on the insulation material, as well as the damaging factors affecting cables that are determined by the operating conditions are considered in the paper. The main and additional mechanisms of aging resulting from the effects of damaging factors are provided. The paper presents the main methods of cable aging management: determining the actual service life and testing using field methods and other means. The basic principles for the arrangement of cable aging management at Ukrainian NPPs, as well as the methods used to investigate the technical condition of cables, are presented. A list of mandatory lists has been defined when performing activities on cable aging management. A methodology is described for lifetime extension of cables, and conditions for extending the service life of cables that are in service are provided. A number of methods of testing cables for aging management are considered: visual inspection of insulation and measurement of crack size, discoloration, etc.; insulation hardness test; insulation chemical analysis; electrical insulation tests; tensile strength measurement; measurement of elongation at break; measurements of dielectric loss at low frequency or sweep frequency; testing by dynamic reflectometry method; AC and DC current impedance measurements. The paper presents results of separate laboratory studies for selected 1 kV representative power cables with PVC insulation of SUNPP-1, ZNPP-1 and KhNPP-2 conducted within Ukrainian NPP long-term operation, which included a stage of laboratory examination and examination of cable samples in operating conditions. The following results were obtained: dependence of VVGng 4x6 cable lifetime on operating temperature; dependence of AVVG cable lifetime on operating temperature; dependence of AVVG (a) cable lifetime on operating temperature. There are possibilities and conditions under which the use of cables within long-term operation is permissible.

A predictive model for polyethylene cable insulation degradation in combined thermal and radiation environments

Reliable prediction of material service lifetime is important for ensuring safe operation in safety-critical systems such as nuclear facilities. Materials in these environments degrade due to several simultaneous effects, most important stressors are heat and radiation. In this work, samples of medium density polyethylene cable insulation were subjected to thermal (110 °C) and γ-radiation stress (500 Gy h−1); a combined thermal and radiation test (85 °C and 4.5 Gy h−1) was also performed. Stability of cable insulation was studied by differential scanning calorimetry and isoconversional kinetic analysis employing a non-Arrhenian temperature function was carried out. From the dependence of residual stability on the degradation dose a predictive model for the cable service life was developed based on the thermal and radiation stress tests; the model validity was verified using the combined stress test results. The model assumes a first-order exponential decay of the residual stability with degradation dose. It allows to predict the degree of insulation damage in wide range of environmental conditions as both temperature and radiation dose effects are considered and radiation dose rate effect is also taken into account.

MODIFICATION OF COMPOSITE MIXTURES FOR MANUFACTURING SHIP CABLEWARE MATERIALS

The purpose of this work was to develop a modified polymeric composite mixture for the manufacture of the outer shell of a ship's cable operating under conditions of aggressive environment and increased fire hazard. The performed research resulted in the analysis of the basic polymeric composite mixtures. A complex of the most important technical and operational characteristics of the cable shell was formed. These characteristics are wear resistance, oil resistance and fire safety. On the basis of these assumptions a new polymer composition based on chloropolyethylene TYRIN CM 3630E with an increased oxygen index and improved physical and mechanical properties was developed. Modification of the mixture was carried out by increasing the mass fraction of flame-retardant additives and adding stabilizers to the mixture. Thanks to a balanced combination of technical and operational properties the use of the developed compound will increase the cable service life and operating time and will reduce the overall weight of the cable by using conductors of a smaller cross-section at a higher operating temperature.

Parametric study of the dynamic motions and mechanical characteristics of power cables for wave energy converters

A case study of a point-absorber wave energy converter (WEC) system is presented. The WEC system forms an array, with several WECs located around a central hub to which they are each connected by a short, free-hanging power cable. The objective of the study is to analyse the dynamic characteristics and estimate the fatigue life of the power cable which is not yet in use or available on the commercial market. Hence, a novel approach is adopted in the study considering that the power cable’s length is restricted by several factors (e.g., the clearances between the service vessel and seabed and the cable), and the cable is subject to motion and loading from the WEC and to environmental loads from waves and currents (i.e., dynamic cable). The power cable’s characteristics are assessed using a numerical model subjected to a parametric analysis, in which the environmental parameters and the cable’s design parameters are varied. The results of the numerical simulations are compared and discussed regarding the responses of the power cables, including dynamic motion, curvature, cross-sectional forces, and accumulated fatigue damage. The effects of environmental conditions on the long-term mechanical life spans of the power cables are also investigated. Important cable design parameters that result in a long power cable (fatigue) service life are identified, and the cable service life is predicted. This study contributes a methodology for the first-principle design of WEC cables that enables the prediction of cable fatigue life by considering environmental conditions and variations in cable design parameters.

Correlation between mechanical and electrical properties for assessing the degradation of ethylene propylene rubber cables used in nuclear power plants

The correlation among the indenter modulus, the elongation-at-break, and the breakdown-voltage strength for the ethylene propylene rubber (EPR) cables subjected to long-term thermal aging and high-temperature water submerging conditions were investigated in this work. The mechanical and electrical limits of EPR insulation material were evaluated by using an indenter modulus, with non-destructive advantage, to monitor the cable condition and to assess its remaining life. Results show that it is plausible to use indenter modulus to monitor the EPR cables for the condition approaching the end of cable service life. Testing parameters on indenter modulus, including indenter diameter, penetration speed, and penetration depth, were studied for monitoring cable degradation condition. Finally, this paper discusses the cable acceptance criteria under thermal and moisture-related aging environments. Results show that the breakdown-voltage strength is a better acceptance criterion for assessing the cable aging condition in a wet environment. While, if the cable is located in a high temperature environment, the elongation-at-break is a better criterion.

Study of the natural ageing of PVC insulation for electrical cables

The characterisation of high voltage cable insulation waste is addressed in an effort to determine their further utilisation either as feed in reprocessing or for the recovery of the energy and material content by pyrolysis. Electrically aged (18 years outdoors at 6–10 kV) polyvinyl chloride (PVC) cables were ground by mechanical or cryogenic procedures. The waste was studied in comparison with a PVC virgin resin and a PVC virgin formulation similar to that of the cables both in quantities of additives and structure of polymer. After successive extractions in acetone and benzene the base polymer and extracts were analysed by elemental analysis, GPC, viscometry, IR and 1H-NMR spectroscopy, TG, DSC, and several standard methods of plastic analysis (plasticizer absorption, static thermal stability, etc.). From the acetone extracted quantities and the plasticizer absorption measurements it appears that only 1–2% di-2-ethylhexylphthalate (DOP) was lost during the service-life of cables and most of the initial quantity remained in the cable composition so only a small addition is necessary for the reprocessing. The IR spectra of polymer extracted from electrical cable waste exhibit important changes concerning double bonds and carbonyl groups. The T g value is higher for the waste material indicating that it was rigidized due to the polyene fragments arising from partial dehydrochlorination. This is also supported by the viscometric and GPC measurements, the PVC from waste having a higher molecular weight than virgin PVC. Based on T g curves and static thermal stability the following order of thermal stability has been established: PVC waste jacket<PVC electrical cable waste<virgin PVC<PVC virgin cable formulation. One can conclude that PVC cable wastes have retained most of the characteristics required for reprocessing, but a higher level of stabilisers must be used to ensure the stabilisation of the deteriorated structure and compensate partial deactivation of the initial stabiliser system.

The Development and Commercialization of Ignition Suppressant, Moisture Barrier Instrument, Control and Power Cables

Plastic coated metal shielding tapes are becoming more and more prevalent in the wire and cable industry. When these tapes are bonded to a chlorinated polyethylene jacket, a moisture/chemical barrier sheath is created that can be utilized in cables for aboveground applications such as in cable trays, in conduit, or for aerial use on messengers. These designs can also be used for direct burial and inside buildings. Specifically, the development of such coated tapes and chlorinated polyethylene jackets provides wire and cable users with additional sheath designs which can be used to reduce expensive maintenance and extend cable service life.

The Development and Commercialization of Ignition Suppressant, Moisture Barrier Instrument, Control and Power Cables

Plastic coated metal shielding tapes are becoming more and more prevalent in the wire and cable industry. When these tapes are bonded to a chlorinated polyethylene jacket, a moisture/chemical barrier sheath is created that can be utilized in cables for above, ground applications such as in cable trays, in conduit or for aerial use on messengers. These designs can also be used for direct burial and inside buildings. The physical properties of the shielding tapes, combined properties of the tape and jacket, and the properties of various cable designs are all discussed. Additionally, case histories are reviewed which describe the use of these cables in various industrial environments. Specifically, the development of such coated tapes and chlorinated polyethylene jackets provides wire and cable users with additional sheath designs which can be used to reduce expensive maintenance and extend cable service life.