Conductor Temperature Research Articles

Analysis on the Temperature Field and the Ampacity of XLPE Submarine HV Cable Based on Electro-Thermal-Flow Multiphysics Coupling Simulation.

The operating temperature and the ampacity are important parameters to reflect the operating state of cross-linked polyethylene (XLPE) submarine high voltage (HV) cables, and it is of great significance to study the electrothermal coupling law of submarine cable under the seawater flow field. In this study, according to the actual laying conditions of the submarine cable, a multi-physical coupling model of submarine cable is established based on the electromagnetic field, heat transfer field, and fluid field by using the COMSOL finite element simulation software. This model can help to analyze how the temperature and ampacity of the submarine cable are affected by different laying methods, seawater velocity, seawater temperature, laying depth, and soil thermal conductivity. The experimental results show that the pipe laying method can lead to the highest cable conductor temperature, even exceeding the maximum heat-resistant operating temperature of the insulation, and the corresponding ampacity is minimum, so heat dissipation is required. Besides, the conductor temperature and the submarine cable ampacity have a linear relationship with the seawater temperature, and small seawater velocity can significantly improve the submarine cable ampacity. Temperature correction coefficients and ampacity correction coefficients for steady-state seawater are proposed. Furthermore, the laying depth and soil thermal conductivity have great impact on the temperature field and the ampacity of submarine cable, so measures (e.g., artificial backfilling) in areas with low thermal conductivity are needed to improve the submarine cable ampacity.

Time-Process Power Flow Calculation Considering Thermal Behavior of Transmission Components

The conductor temperature is a critical state variable that should be considered in power flow calculations to improve the calculation accuracy and reveal the potential thermal loadability of transmission components. This paper proposes a calculation method for time-process power flow considering the thermal behavior (TPPFCTB) of transmission components to calculate the temperature dynamics of overhead lines, power cables, and transformers under anticipated system operation scenarios. The TPPFCTB model is represented by differential-algebraic equations, which can be solved as a sequence of extended power flow problems at discretization time intervals. Based on the Newton method, incomplete and complete decoupling methods are proposed to decouple the correction equations into several independent groups with constant coefficient matrices, thus improving computational efficiency. The work presented in this paper provides an effective method for the detection of potential power transfer capability problems associated with transmission components, thus guiding operators to make more economical decisions. Numerical simulations were conducted to verify the effectiveness of the proposed method.

Choice and justification of the optimum cooling temperature for HTS cable

At the first stage of designing a high-temperature superconducting (HTS) cable and its cryogenic refrigeration system (CRS), it is necessary to choose the optimum cooling temperature. The operating temperature is selected not only according to the critical parameters of the HTS conductor, but also taking into account other design and operational characteristics - geometry, length, operating current and the need to have subcooled nitrogen to prevent the occurrence of steam inclusions. Normally the range of cooling temperatures is limited by the critical temperature of the HTS conductor (THTS≤ 104К) and the triple point temperature of nitrogen (TLN≥ 63.15K). The choice of a certain temperature value will enable us to approximately evaluate the parameters of the CRS and overall characteristics of the cable. The article presents an analysis of the dependence of the electric power magnitude consumed by the CRS on the choice of the cooling temperature value and cable geometry. The analysis may be useful for determining the characteristics of the HTS cable operating at different temperature levels.

On-Line Control of DERs to Enhance the Dynamic Thermal Rating of Transmission Lines

The increasing penetration of variable distributed generation causes the transmission lines to operate closer to their design thermal limits. In this context, Dynamic Thermal Rating is a very promising technique, since it permits a better exploitation of the real capability margins of the infrastructures and eliminate network congestions. In this vein, the article proposes a novel control strategy that allows maintaining the conductor temperature of a given line within its thermal limit through the real-time curtailment of distributed energy resources in the network. The impact of weather volatility and measurement uncertainty on the dynamic response of the controller is evaluated. A comprehensive case study, based on a real-world Italian sub-transmission system and measurement data serve to illustrate the dynamic behavior of the proposed controller. The effect of measurement noise and delays is also discussed. Finally, the performance of the proposed control strategy is compared with a conventional robust optimal power flow approach.

Nonlinear heat wave propagation in a rigid thermal conductor

We present new nonlinear, one-dimensional equations of extended thermodynamics for temperature and heat flux that describe damped heat wave propagation and predict dependence of the second sound velocity on temperature and heat flux in a rigid thermal conductor. The aim of the present work is to investigate the implications of the considered nonlinearities on the process of heat propagation, especially that such nonlinear effects cannot be disregarded for nanosystems and in small-sized heat conductors, when temperature or heat flux variations are not always proportional to gradients. The characteristics of the nonlinear system of equations are investigated, and a formula for the breaking distance is obtained. For illustration, these equations are solved in the linear approximation by separation of variables, then in the nonlinear case by the homotopy perturbation method in the half-space, and numerically in a bounded interval under concrete initial and boundary conditions. The solutions are discussed in detail and presented graphically. They illustrate the effect of the different material parameters on the propagation of thermal waves and may be used to evaluate some material parameters. The proposed equations provide a closer insight into the thermal interactions in rigid thermal conductors.

Simulation study on ±320kV DC power cable steady-state temperature field distribution and its influencing factors

Temperature distribution is an important parameter in the operation of DC cables, while there are few studies at present. In this paper, the steady-state temperature field distribution of DC cable was calculated by simulation, and the factors including conductor current and outer surface temperature were discussed and analyzed. The results showed that there is a temperature gradient in the radial direction of the cable; Both the conductor current and the outer surface temperature have a significant effect on the overall temperature of the cable; The increase in the conductor current and the outer surface temperature will significantly increase the conductor temperature. However, the insulation temperature difference changes little.

Uncertainties in the Testing of the Coefficient of Thermal Expansion of Overhead Conductors

Overhead lines can be replaced by high temperature low sag (HTLS) conductors in order to increase their capacity. The coefficients of thermal expansion (CTE) of the HTLS conductors are lower than the CTE of conventional conductors. The utilities and conductor manufacturers usually carry out the verification of the CTE of the overhead conductors in an actual size span. The verification is based on the observation of the change of the conductor length as a result of the conductor temperature change. This process is influenced by the coefficient of thermal expansion to be verified. However, there are other factors that also affect it. This paper analyzes the effect of some of the uncertainty sources in the testing of the coefficient of thermal expansion of the overhead conductors. Firstly, the thermal expansion process is described and the uncertainty sources related to the conductor and the line section are identified. Then, the uncertainty sources and their effect on the CTE testing are quantified.

Temperature Analysis Based on Multi-Coupling Field and Ampacity Optimization Calculation of Shore Power Cable Considering Tide Effect

Shore power system that powers berthing ships is gradually becoming widely used worldwide because it helps reduce air and noise pollution. However, due to the bad environment of the port, the influence of the port tide on the temperature distribution and the ampacity of the shore power cable connecting the ship and shore can't be ignored. Therefore, in this paper, a thermal field calculation model of shore power cable based on electromagnetic-thermal-flow coupling field is presented, in which the impact of tide has been considered. And the validity of the coupling model is verified by thermal circuit method base on IEC(International Electrotechnical Commission) 60287 standard. Then, the influence of cable immersion depth, water velocity and temperature, wind speed and air temperature on the temperature distribution of shore power cable was analyzed based on the multi-field coupling model. Finally, the ampacity of shore power cable in different environments is calculated by the combined Newton iterative and numerical simulation method. The results indicate that the conductor temperature firstly decreases and then increases with the immersion depth. And when the immersion depth is small, the wind speed dominates the temperature of the conductor. While the water flow speed plays a leading role in the conductor temperature when the immersion depth is deeper. In addition, the relationship between ambient temperature and capacity of shore power cable is approximately linear.

An Efficient Procedure for Temperature Calculation of High Current Leads in Large Power Transformers

This article presents an efficient methodology for calculating the steady-state temperature of high current busbar leads (HCBL) oil-immersed in large power transformers. The temperature at the surface of the copper HCBL is mainly affected by the Joule effect caused by the passing current, the paper insulation, the top oil temperature rise, and the ambient temperature. The Power Transformer Manufacturers usually follow their proprietary technical specifications for HCBL design in the absence of normalization, and customers would request guidance for temperature calculations independently of proprietary techniques. To date, there is a lack in the literature for this purpose. The method allows calculating the temperature on the HCBL as a function of the parameters already mentioned being flexible because it allows change of the parameters. The method is based on calculating the convection heat transfer coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$h$ </tex-math></inline-formula> ), which in turn depends on the geometry factors and cooling system characteristics. The parameter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$h$ </tex-math></inline-formula> ) is of major importance and play the primary role during temperature calculation, once the desired temperatures are susceptible to its value and accuracy. Other relevant factors such as the skin and proximity effect are determined by the Finite Element Method (FEM). To validate the proposed method’s accuracy, we did measurements using the T2TM Fiber Optic Temperature Sensor from NEOPTIX on a 460 MVA Transformer, running the heating test at 100% of load during 72 hours, yielding satisfactory results. The method is also compared with the winding gradient, which is usually used to estimate the top’s conductor temperature.

Review of Thermal Stress and Condition Monitoring Technologies for Overhead Transmission Lines: Issues and Challenges

The overhead transmission line system is one of the methods of transmitting electrical energy at a high voltage from one point to another, especially over long distances. The demand for electrical energy is increasing due to the increase in the world population, the evolution of transport technology, and economic expansion, thereby resulting in overloading to the overhead line (OHL) system. In building new infrastructure for transmission lines, several issues need to be addressed. Thus, optimizing existing power by increasing the ampacity of power line is a practical solution to meet energy demand issues. During long-term operation, the temperature of OHL conductors may increase beyond their rated temperature, which is typically 75 °C for conventional conductors such as aluminum-conductor steel-reinforced cable. This condition is defined as thermal stress, which results in lower sag vertical clearance, tensile loss, elongation and creep, and reduced life span of the conductors. This condition must be avoided to ensure that the line is not permanently elongated, which can disrupt the vertical ground clearance, and to expand the conductor’s life. Other factors such as lightning, wildfire, aging, and degradation of the conductor can also cause thermal stress on the conductors and have thermal effects on the conductor’s performance. Therefore, unwanted thermal stress needs to be examined and identified by monitoring the thermal effect and behavior of the lines. This paper presents the state of the art in monitoring technologies that can be used to identify thermal stress on OHL conductors, including the issues and challenges in monitoring. At the end of this paper, a few suggestions are included to address the occurrence and assessment of thermal stress in lines. Ultimately, this work may provide complete information to researchers and maintenance engineers to enable them to make better decisions on condition monitoring, operation, and maintenance of the system.

Non-contact Dynamic Capacity-Increasing of Overhead Conductor Based on Cooling Tester (CT)

The traditional dynamic capacity-increasing technology of overhead conductors needs to monitor the operation state of conductors (temperature, sag, etc.), and the relevant sensors are usually installed directly on the surface of conductors. The installation cost is high, and the operating maintenance is complicated. In this paper, a non-contact dynamic capacity-increasing method for overhead conductors based on CT is proposed. Firstly, the theory of the non-contact dynamic capacity-increasing method for conductors is introduced, and a cooling testing device is designed according to the theory. Then, the cooling index is defined to represent the cooling capacity of the object, and the corresponding cooling indexes for the conductors and the CT are calculated based on the steady-state thermal balance equation. By establishing a cooling correlation model for the conductors and the CT, the calculation for the dynamic ampacity of the conductors can be obtained. Finally, the cooling conditions of cooling testing device at different ambient temperatures and wind speeds are calculated through the finite element simulation method. Combined with the dynamic capacityincreasing method proposed in this paper, the corresponding ampacity value are obtained, and the effect of capacity increase is analyzed. The results show that the non-contact dynamic capacity-increasing method based on the CT has obvious effect in capacity-increasing compared with the static ampacity.

The thermal inertia time constants and its influencing factors in the thermal dynamic process of overhead line and cable

Due to the existence of thermal capacity, the conductor temperature of overhead line and cable changes later than current steps (thermal inertia), and the thermal dynamic process of the conductor contains the huge current-carrying potential. As an important symbol of thermal dynamic process, the thermal inertia time constant is of great significance to describe the characteristics of thermal dynamic process accurately. In this paper, the thermal inertia time constants of overhead line and cable and its influencing factors are studied based on the heat balance models, which can be solved by the fourth order Runge-Kutta method. Then the four factors including the current step, ambient temperature, wind speed and global radiation intensity are used to explore their influence on the thermal inertia time constant of overhead line, and the current step and soil temperature on cable. The numerical results show the effects of influencing factors on the thermal inertia time constant and provide a theoretical basis for a more detailed evaluation of the thermal dynamic process.

A short-time physics problem in superconductivity: Stability against quench

This paper investigates the stability problem of superconductors against quench. Numerical Finite Element simulations are applied to calculate the distribution of transient temperature, critical current density and transport current in the conductor cross-section under a disturbance, here flux flow losses. Contrary to standard stability models, the focus of the paper is on situations very close to the superconducting/normal conducting phase transition. The obtained results demonstrate it is not realistic, even in thin films, to assume uniform conductor temperature under a disturbance. A method is suggested on how to predict the time and position of a quench when it is expected to occur in the conductor cross-section. Quench starts locally. Application of a microscopic stability model allows to describe continuous, not abrupt but very fast break-down of transport current in situations close to the phase transition.

Demand Response and Dynamic Line Ratings for Optimum Power Network Reliability and Ageing

This study proposes a methodology to optimise the use of average demand loss of each load bus to enhance line ratings and modify load curves, by minimising demand loss and network ageing due to elevated conductor temperatures. The considered lines are connected to load buses, operated with dynamic line rating technology and have actual conductor physical properties. The simulation of line failures considers line loadings, whose values are based on utilizations of the average demand loss of load buses where the lines are connected, and the remaining service life of the conductor. Demand response in the form of peak-shaving and valley-filling is used to modify load demand curves, with the allowable peak load reduced based on utilizations of the remaining average demand loss. The average demand loss values are determined in the preliminary screening module of the proposed method. Various trade-offs between ageing and reliability of the network are solved based on the two-objective non-sorting genetic algorithm and fuzzy decision-making method in the execution module of the proposed method. Results have shown that the proposed method is cost-effective in that it strategically increase line ageing slightly to enhance system reliability, by as much as 71.9%, based on the equal emphasis of network ageing and reliability, when compared with the scenario that only prioritizes the protection of network ageing. Line ageing is also 68.2% lower on average across the entire spectrum of rating exceedance (1% to 25%) compared to the scenario that only prioritizes enhancement of network reliability.

A Review of Dynamic Thermal Line Rating Methods With Forecasting

Power flow, on both AC and DC overhead transmission lines, is limited to keep the conductor temperature below a maximum (TCMAX) specified to limit both conductor sag and the aging of conductors and splices over time. This power flow limit (line thermal rating) varies with weather conditions along the line corridor but, for simplicity, static line ratings (SLR) are normally calculated for “suitably conservative” annual or seasonal weather conditions. Dynamic line ratings (DLR) change with the real-time weather conditions along the line, are usually higher than SLR, and are more complex to use in system operation. Forecasting of DLR requires forecasting of line corridor weather conditions but makes DLR more useful to power system operations. This paper discusses DLR methods including forecast techniques and presents various field applications.

Calculation of electrothermal coupling power flow for XLPE insulated cable-based distribution systems

Power cable is an important transmission component in distribution systems. The full utilization of the cable's transfer capability is of great significance to improve the economic and security performances of distribution systems. In this paper, a calculation method for electrothermal coupling (ETC) power flow for cable-based distribution systems is developed by embedding the solution of the thermal model of the crosslinked polyethylene (XLPE) insulated cable into the forward-backward sweep power flow calculation process of distribution systems. The method can be used to calculate the temperature dynamics of 3-phase cables under anticipated operation scenarios of distribution systems, thus revealing the potential transfer capability exists in the thermal inertia process of cable lines to operators. In case studies, the validity of the proposed ETC power flow calculation method is verified. Besides, the influence of the temperature of cable conductors on power flow is analyzed and the benefits of implementing the ETC power flow for the cable-based distribution systems are also illustrated.

STUDY OF A FLOWING-TYPE HEAT TRANSFER INTENSIFIER USED AS PART OF A THERMOELECTRIC SEA WATER DESALINATION SYSTEM

Objectives To analyse the thermophysical processes in the thermoelectric heat transfer intensifier operating as part of a desalination system based on semiconductor thermoelectric converters.Method A mathematical model for the design of a desalter containing a thermoelectric heat exchanger, which provides for the use of heat flows by natural thermal conductivity due to so-called heat channels, is proposed. The proposed method of using additional heat sinks on the heat-absorbing side of the device and additional heat sources on the fuel side determines the need for a new mathematical model that differs from the known mathematical models describing heat transfer in the heat transfer flowing-type intensifier.Results The analysis of modelling results shows that a significant contribution to the temperature field of heat conductors is made when considering the heat transfer over the heat channels. The value of the contribution is the greater, the higher the thermal conductivity of the heat channels and the temperature difference between the heat conductors and the surface of the heat channels. In accordance with their purpose, flow-type thermoelectric heat transfer intensifiers (THTIs) for desalination applications must ensure efficient heat transfer from the cooled fluid flow to the heated fluid flow. The results show that, at a given limited length of the heat exchanger, the use of a thermoelectric battery together with heat channels allows equality of temperatures of heat conductors at the output to be achieved.Conclusion The modelling results show that, under the operating conditions of the thermal battery in intensifier mode, the length of the heat exchanger shall not exceed the value, at which the temperature of the heat conductor at the outlet becomes equal. The system solution provides the required length of the thermal battery, which allows equality of coolant temperatures to be achieved at the exit from the THTI operation mode. Following the logic of the desalter scheme under consideration, it is obvious that the reduction in the length of the heat exchanger, with all other things being equal, gives a reduction in the mass and size of the device as a whole.

Investigations on High Temperature Low Sag (HTLS) Conductors

Electric power demand is growing at an exponential rate due to establishment of industries and economic growth in the country. Central electricity authority of India (CEA) has estimated per capita electricity consumption will increase at a rate of 6 percent per annum, this will increase the load on the transmission and distribution system. Limitations of Right of Way (ROW) has made it difficult to construct new lines, particularly in metropolitan and densely populated cities, hence high temperature low sag (HTLS) conductors are being used adopted, several projects in the country are being executed to overcome the problem of burdening of transmission/distribution system. HTLS conductors operate at 2–3 times higher ampacity and thermal rating, hence can be used for higher power transmission without upgrading the existing towers and infrastructure. The present investigation aims to understand and estimate the conductor temperature and ampacity dependent on different parameters like wind velocity, wind angle, emissivity and fault current level. The investigation highlights the dynamic thermal rating of HTLS conductor with change in wind velocity and angle, thermal performance of conductor during fault condition and thermal rating with emissivity, absorptivity and ambient temperature during flow of fault current is presented. A new experimental setup is established to investigate the performance of HTLS and Traction copper conductor in the laboratory, attempt has been made to study effect of magnetic fields and conduct EBSD analysis, some important conclusions drawn from the investigations are analyzed and presented.

A Design of Analysis Influence of Channel Flow Instability Against Andongan On SUTT 150 Kv

A Transmission lines airgenerally use ACSR type conductors. Increased demand for electrical energy, the effort to increase the transmission line capacity is done by optimizing the current carrying capacity of the existing transmission line, but the problem that arises in this optimization is the increase in voltage and the portion of the conductor. This study aims to determine the effect of channel flow instability on the conductor temperature, the conductor section, andongan angle and conductor voltage, which is then useful for the construction of the transmission line construction structure in accordance with the mechanical properties of the conductor used. The calculation in this study uses the heat balance equation to calculate the conductor temperature. The Basic Span Length method is used to determine the equivalent span length.

Melt dripping behavior in the process of flame spread over energized electrical wire at different pressures

SummaryMelt dripping of polymer insulation in electrical wires is impacted by some factors, such as ambient pressure and electric current. The motivation of this paper is to investigate and discuss the effect of these factors on melt dripping characteristics in the process of flame spread over electrical wire. The results show that the number of dripping times and dripping frequency generally increase with ambient pressure reduced. No dripping phenomenon occurs when the ambient pressure is below 40 kPa at any electric current or is above 70 kPa without electric current applied. There is a good parabolic correlation between the ambient pressure and dripping frequency. The equilibrium temperature of conductor resulted by electric current increases with electric current. A critical electric current found to divide the temperature rate into two regimes is about 8 A. The dripping period and dripping frequency depend on the electric current. The dripping frequency fits well with electric current using a power‐law function. The numerical data are consistent with the experimental data. Besides, the decrease in dripping frequency is greater with ambient pressure at reduced electric current, whereas at larger electric current, the electric current, rather than the ambient pressure, dominates the increased dripping frequency.