Winding Temperature Distribution Research Articles

Framework for assessing the performance of overhead transmission lines under wind-temperature effects

This paper presents a framework for evaluating the wind-induced resistance of overhead transmission lines (OTLs), aiming to overcome the limitations associated with disregarding temperature effects and relying on a single metric for failure assessment. The proposed framework factors in temperature influence, carefully considers applied loads and structural characteristics, and accurately calculates failure probability based on a specific case study. Meteorological data is initially collected to create a probabilistic model of wind speed and temperature distribution, accounting for correlation. Components and systems are graded based on structural characteristics and damage modes. The neural network surrogate model is trained with finite element computations for load-structural response sample sets. The surrogate model, in conjunction with logistic regression, generates samples to determine fragility. Finally, the total structural failure probability and monthly failure likelihood are computed by integrating the joint probability model and fragility. Analyses highlight temperature's significant impact on conductor-ground line safety, validating the proposed framework's rationale.

Research on Real-Time Calculation Method of Transformer Temperature Field Based on Reduced Order Model and Sparse Measurement

The lifespan of transformers is closely related to their operating temperature. Among the existing temperature acquisition methods, the measurement method cannot obtain the complete temperature field temperature, while the numerical calculation method presents the challenge of significant computational expenses. This study theoretically derived how to determine the real-time temperature distribution of transformer windings based on sparse measurement data and reduced order models and solved sensor layout issues, including the number and placement position of sensors. In this study, the maximum calculation error of the temperature distribution is 1.8 K, and the calculation time is 0.38 seconds. The research findings suggest that multiple modes can contribute to the temperature distribution of a transformer. Under a constant load condition, the calculation of transformer temperature can be achieved by utilizing a temperature sensor positioned at the hot spot in conjunction with the first mode.

Fast calculation of temperature distribution in oil-immersed transformer windings based on U-net neural network

In this paper, a fast computational method based on the training of the U-net neural network is proposed to solve the fluid-thermal coupling problem of transformers. First, the input variables are selected according to the fluid-thermal coupling principle, and the finite volume method is applied to obtain the output results under different operating conditions and make them into training sets and test sets. Second, the training sets are normalized and input into the U-net neural network. At the same time, three hyperparameters that have more influence on the network training are discussed in detail, and the optimal combination of hyperparameters is determined. Finally, the prediction set is fed into the trained model for prediction computation, and the results are subjected to the inverse normalization operation, whose predictive results are consistent with those calculated by the finite volume method. In addition, the computational time is shortened from 300 to 0.07 s, and the prediction variance does not exceed 0.055 K2. The results show that the proposed method can be used to obtain the temperature of immersed transformer windings quickly, which provides an effective tool for real-time temperature simulation of the digital twin of power transformers.

Thermal analysis and optimization on a transformer winding based on non-uniform loss distribution

Generally, thermal analyses and optimizations on the transformer winding were carried out under an assumption of uniform heat losses. But in fact, winding heat losses are distributed unevenly, which may intensify local hot-spots and result in winding performance deterioration. This work was to investigate the difference of winding temperature distributions under the two loss conditions. To realize it, first, an electromagnetic-thermo-flow bidirectional coupling numerical model was developed for a converter transformer winding to calculate actual winding losses and temperature. Then, the winding temperature distribution was compared with that under the assumed uniform loss condition, and their differences were quantitatively analyzed. The results showed that for most winding structures studied in this work, the winding hot-spot temperature rises (ΔTmax) under the non-uniform loss condition was greater than that under the assumed uniform loss condition, and their difference was greater than 5%. This difference was more obvious at a less flow rate. This suggested that ΔTmax would be underestimated based on the assumption of uniform heat losses, which posed a threat to the transformer reliability. Therefore, it was necessary to consider non-uniform loss distribution to calculate the winding temperature, so as to improve the safety margin of the transformer and thus improve its reliability. Furthermore, to eliminate the uncertainty of multi-response optimization results caused by the uniform loss assumption, a multi-response optimization on the winding structural parameters was conducted based on the non-uniform loss distribution. The optimization results under the two loss conditions were compared. The results showed that the optimum winding structural parameters under the two loss conditions were consistent. However, the hot-spot positions of the optimum winding structure under the two loss conditions were different. This meant that it was feasible to adopt the general assumption to conduct multi-response optimizations to improve efficiency, but to predict the hot-spot of the optimum winding structure more accurately, it was necessary to consider the non-uniform loss distribution.

Performance of summertime temperature and wind fields under different background winds in Kowloon, Hong Kong

The increasingly frequent urban extreme heat events are adversely affecting human health and the economy worldwide. In the last three decades, Kowloon, Hong Kong, one of the most densely populated urban areas in the world, has witnessed a rapid warming rate of 0.31 °C/decade. An in-depth study of the wind and temperature environment is needed to explore the urban warming mechanisms in Kowloon. Using semi-idealised Weather Research and Forecasting (WRF) simulations, we investigated the wind flow fields over the Kowloon area under various background wind conditions. The evolution and interaction of urban heat island circulation, sea–land breeze circulation and mountain circulation under calm weather conditions were also studied. We examined weather photos of Kowloon to identify cloud locations and evaluate our predicted urban plumes. We also explored the association between background wind and spatial air temperature distribution in Kowloon. Northeasterly wind conditions can lead to high temperatures at the foothills of mountains situated northeast of Kowloon; a streamline analysis showed that heat advection accounts for this phenomenon during the day, while a possible foehn-like wind plays an important role at night. These insights into the wind and thermal environment in Kowloon can contribute to the interpretation and prediction of extreme heat events.

Modeling Method for Thermal Field of Turbulent Cooling Dry-Type On-Board Traction Transformer in EMUs

Adopting dry-type on-board traction transformer (OBTT) is one of the main ways to reduce the weight of electric traction systems, and its thermal characteristics are crucial for the safe operation of high-speed electric multiple units (EMUs). However, the existing thermal modeling methods either cannot realize the fast calculation of thermal characteristics of dry-type OBTT, or cannot accurately obtain the turbulence heat-transfer intensity when using the high-speed train-induced wind cooling. This article proposes an efficient method for dry-type OBTT thermal characteristics calculation. First, the thermal network of the winding area is proposed considering the thermal developing region of the air duct and the heat flow in the insulation paper between conductors. Then, the effects of key parameters on convective heat-transfer intensity are obtained by computational fluid dynamics (CFD) parametric sweeps, and then a novel local Nusselt number correlation for accurately calculating the turbulent convective thermal resistance is proposed. Finally, validation is performed with an experimental setup. The experimental results show that the computationally efficient thermal network model proposed in this article can quickly obtain the winding temperature distribution and the location of the hot-spot temperature. Moreover, the thermal analysis of a 6.3 MVA dry-type OBTT was conducted using the proposed modeling method.

Investigation of Open-Circuit Fault-Tolerant Strategy in a Modular Permanent Magnet Synchronous In-Wheel Motor Based on Electromagnetic–Thermal Analysis

This article investigates the asymmetric temperature distribution of a modular permanent magnet (PM) synchronous in-wheel motor under fault conditions, and based on this, proposes a fault-tolerant (FT) strategy named minimum temperature difference strategy (MTDS) to avoid the high temperature appearing at local winding. First, the modular motor system and the FT principle are introduced, and the reconfiguring fundamental magneto motive force (MMF) under open-circuit of one phase in one module is deduced. Second, the loss and temperature distributions of the motor with normal operation are analyzed by the coupled electromagnetic–thermal method. And the mutual verification between simulation and experiment is adopted to separate the copper losses, iron losses, and PM losses from total losses. Furthermore, the asymmetric temperature distributions of the motor operating with part of modules are analyzed in detail. Finally, the influence of the faulty windings on the temperature of healthy windings is investigated, and the FT strategy of MTDS is proposed. The asymmetric temperature distributions of the motor under various FT strategies are compared. The result shows that the MTDS can significantly reduce the maximum temperature of the windings and makes the winding temperature distribution more uniform.

Effect of Loads on Temperature Distribution Characteristics of Oil-Immersed Transformer Winding

The temperature of the hot-spots on windings is a crucial factor that can limitthe overload capacity of the transformer. Few studies consider the impactof the load on the hot-spot when studying the hot-spot temperature and itslocation. In this paper, a thermal circuit model based on the thermoelectricanalogy method is built to simulate the transformer winding and transformeroil temperature distribution. The hot-spot temperature and its location underdifferent loads are qualitatively analyzed, and the hot-spot location is ana-lyzed and compared to the experimental results. The results show that thehot-spot position on the winding under the rated power appears at 85.88% ofthe winding height, and the hot-spot position of the winding moves down by5% in turn at 1.3, 1.48, and 1.73 times the rated power respectively.

Fringing-Effect Losses in Inductors by Thermal Modeling and Thermographic Measurements

The fringing-field phenomenon can have a significant impact on power loss and temperature distribution in windings of magnetic components with an air gap. The magnetic flux in a core does not cross the air gap in straight lines, but fringes out into the surrounding medium, causing electromagnetic interactions with the winding enclosing the air gap. The fringing flux induces excess eddy currents in the windings, causing localized heating and reducing the overall efficiency of power conversion. This effect can be analyzed by infrared thermography. In this article, the investigated component is an output choke in a forward converter. Thermographic analysis and power loss measurements were carried out for two different air gap configurations: a single discrete air gap and a quasi-distributed air gap. The obtained thermal characteristics were utilized to construct compact thermal models of the inductor. Compact thermal modeling coupled with thermographic measurements can be used to identify power loss density in individual sections of the copper coil and estimate the impact of the fringing effect on the winding in the vicinity of the air gap. As shown herein, splitting the single air gap into a number of individual air gaps, hence creating a quasi-distributed air gap, causes the fringing effect to be largely diminished.

Study on Oil Flow Characteristics and Winding Temperature Distribution of Oil-immersed Transformer

The stability and effective functioning of a power grid depends upon the reliability as well as safety prospects of a transformer which is the principal component of the power system. The natural oil circulation in the oil-immersed transformer drifts the oil flow by the change in the density which is again caused by the change in temperature. But the pressure is comparatively low with respect to the oil pump causing the lower down of velocity which in turn dissipates unimpressionable heat. In this paper, a noble attempt has been made to build a natural oil circulation layer-type winding transformer based on a fluid-solid coupling heat transfer model pertaining to the internal temperature field and flow field by using the fluid mechanics’ simulation software. In the next stage, the authors have analyzed the temperature distribution, hot spot, position condition of the variable winding, the horizontal the oil channel width as well as the temperature of the winding transformer. The paper is of great significance as it examines the influence of the flow characteristics of oil channel on the winding temperature distribution. The outcome can significantly improve the structure of heat dissipation and the operating environment of the transformer.

Spatial environment design and comfort simulation of high-latitude building bottom based on geological conditions

In order to solve the situation that the temperature in the high-latitude area is large and the space comfort of the bottom of the building is poor, the bottom space environment of the high-latitude building based on geological conditions is designed, and the comfort of the space environment is simulated. The numerical simulation technology is used to simulate the temperature information of the bottom space of the building, and the temperature, velocity, and humidity fields of the space air at the bottom of the building affected by the geological conditions are obtained. Based on the characteristics of the high-latitude space environment, the design is applied to the single-core bottom space and the multi-core bottom space. The space environment at the bottom of the high-latitude building is divided into functional partitions of the bottom space; the outdoor open space thermal comfort model of Actual Sensation Vote (ASV) is used to simulate the wind environment, radiation distribution, temperature, and humidity distribution and simulate the comfort of the space environment at the bottom of the building. The analysis of the experimental results shows that the weather condition at 8:00 am is the most comfortable time for human body to feel. At this time, the thermal feeling in most areas of the indoor space is moderate, which shows that the method can accurately simulate the comfort of the space environment at the bottom of the building from the perspective of radiation distribution, wind speed distribution, and thermal comfort distribution, and the designed space environment function layout at the bottom of the building is reasonable.

Comparative Study of Three Stator Cooling Jackets for Electric Machine of Mild Hybrid Vehicle

Three stator cooling jacket concepts, including a new cooling jacket concept with parallel straight spiral channels, are evaluated for electric machine of mild hybrid electric car. Steady-state cooling jacket thermal flow analysis and transient-state full motor simulations with circumferential, axial, and spiral jacket concepts are carried out to predict their heat transfer performance and temperature distribution. A prototype motor has been made with the new jacket concept. Infrared thermography is performed to detect the transient temperature distribution of the motor stator windings and laminations for validation of the thermal flow analysis.

CFD analysis on velocity and temperature distribution of airflow inside model building with windcatcher

Windcatchers are ventilation instruments used for obtaining the characteristic of cooling. They have been utilized in the buildings for a long time ago in countries with hot dry atmospheres especially in the Middle East. Natural ventilation is progressively utilized in the modern building to limit the use of non- sustainable supply. This study describes another alternative for adopting clean energy in buildings by applying windcatcher on buildings. This present study analyses between two types of windcatcher (one-sided and two-sided windcatcher) by varying the inlet velocity of airflow. This study aims to investigate wind velocity and temperature distribution in a model building with one outlet opening position using Computational Fluid Dynamics (CFD) simulation. Reynolds-Average Navier Stokes (RANS) approach with the turbulence model of standard k-ε was used to perform the simulation. It is shown that the two-sided windcatcher is more effective than the one-sided windcatcher. Two-sided windcatcher induces a high volume of airflow inside the building compared to the one-sided windcatcher.

A Dynamic Multilayer Winding Thermal Model for Electrical Machines With Concentrated Windings

This paper presents a dynamic multilayer winding lumped-parameter thermal model dedicated to electrical machines with concentrated windings. The winding is layered into a series of circular rings by a novel layer strategy according to the winding temperature distribution obtained by a two-dimensional analytical slot winding thermal model. Accordingly, the layer number can be automatically and dynamically adjusted so as to accurately model the winding temperature distribution using the smallest layer number. Besides, the end-winding is also layered similarly to the slot-winding based on the thermal behavior of the nonoverlapping concentrated windings. The proposed winding model could accurately calculate the temperature distribution within the slot, including the winding maximum and average temperature. Experiments on a winding motorette and a water-cooled permanent magnet machines with concentrated winding intended for electric vehicles have been implemented to validate the proposed winding thermal model.

Eddy Current Loss Effect in Foil Winding of Transformer Based on Magneto-Fluid-Thermal Simulation

The foil winding temperature distribution is crucial to the life of power transformer since local heating can accelerate aging of insulation materials. However, based on the traditional 3-D electromagnetic model and the principle of heat transfer, the non-uniform losses and temperature distribution of foil windings are difficult to estimate because of complex magnetic leakage flux. In this paper, the magneto-fluid-thermal coupling model has been established to calculate the temperature rise and predict the potential hotspots of a simplified dry-type power transformer rated at 2500 kVA. Moreover, the influence of insulation barrier is considered to reshape the air-flow path and to affect the radiative effect between the high-voltage and low-voltage windings. Experimental temperature rises are measured with infrared thermography to verify the simulation results, which achieved reasonable hotspot predictions and provide the theoretical method for transformer designers.

The Effects of Water Friction Loss Calculation on the Thermal Field of the Canned Motor

The thermal behavior of a canned motor also depends on the losses and the cooling capability, and these losses cause an increase in the temperature of the stator winding. This paper focuses on the modeling and simulation of the thermal fields of the large canned induction motor by different calculation methods of water friction loss. The values of water friction losses are set as heat sources in the corresponding clearance of water at different positions along the duct and are calculated by the analytical method, loss separation test method, and by assuming the values that may be larger than the experimental results and at zero. Based on Finite volume method (FVM), 3D turbulent flow and heat transfer equations of the canned motor are solve numerically to obtain the temperature distributions of different parts of the motor. The analysis results of water friction loss are compared with the measurements, obtained from the total losses using the loss separation method. The results show that the magnitude of water friction loss within various parts of the motor does not affect the position of peak temperature and the tendency of the temperature distribution of windings. This paper is highly significant for the design of cooling structures of electrical machines.

Prediction of oil flow and temperature distribution of transformer winding based on multi‐field coupled approach

For large oil-filled transformers, the oil flow and temperature distribution in transformer windings are an essential issue to be addressed. However, the computation of the oil flow and temperature distribution is a complicated engineering problem because of the complex physical structure of the winding area and the coupled effect of electromagnetic, fluid and thermal fields. This study presents a multi-filed coupled approach to compute and analyse the oil flow and temperature distribution of the winding area for an ODFS-334 MVA/500 kV single-phase auto-transformer. The eddy current losses of the transformer winding discs are computed based on the combined finite element and analytical method, and the computational fluid dynamics based on 3D fluid-thermal coupled method is used to calculate the oil flow and temperature properties of the prototype. The computation of the oil flow and temperature distribution reveals accurately the hot spot of the transformer. To validate the feasibility and applicability of the proposed method, the numerical results obtained using the proposed method are compared with those of the experimental ones.

A study on wind and air temperature distribution in coastal urban area and urban design model for improving the ventilation

A study on wind and air temperature distribution in coastal urban area and urban design model for improving the ventilation

Ascertainment of fringing-effect losses in ferrite inductors with an air gap by thermal compact modelling and thermographic measurements

Recent years have been characterized by a rapid increase in the efficiency of energy conversion and power density, which are the key criteria in the design of high-frequency power converters and the best measures of their performance. The demand for reduced size and minimization of losses has led to a revaluation of the approach to building magnetic components, driving the operating frequency to ever higher levels in order to facilitate more compact and efficient designs. These could not have been achieved without the investigation of phenomena associated with electromagnetic fields and the utilization of thermal analysis tools. Thermal qualification is particularly crucial for magnetic components with an air gap, due to the fringing magnetic field around the air gap. The fringing flux induces excess eddy currents in the windings causing localized heating (hotspots) and reducing the overall efficiency of power conversion. This extra power loss is beginning to be a significant factor in an increasing number of designs. As shown herein, the power loss associated with the phenomenon can make up about 25% of the total losses in a magnetic component. This illustrates the potential hazards of designing magnetic components with an air gap, be they transformers or chokes, without taking the fringing effect into consideration.A novel approach is presented here to estimate the fringing-effect power loss. This method is based on compact thermal modelling and thermographic measurements. A DC-DC high-frequency forward converter and a centre-gapped ferrite core inductor were constructed so as to perform dynamic, time-dependent thermographic analysis on the latter. The obtained thermal characteristics, juxtaposed with the thermal compact model created for the inductor, allowed for the extraction of the fringing-effect loss from all power-loss sources present. The ascertainment of the fringing-effect loss is problematic, as the phenomenon is not limited only to the area above the air gap but has an effect on neighbouring copper wires, causing a distinctive pattern in temperature distribution in windings if measured along the gapped middle column of the ferrite core. The power-loss density in areas away from an air gap, where the fringing-effect component is not present or largely diminished, is nearly homogenous. This power-loss density, if referred to the entire volume of the coil, yields the power loss in the winding with no fringing-effect component. A simple deduction from the measured total power dissipated in the winding leads to the ascertainment of the fringing-effect loss.

Analysis of Physics Environment in Urban Village Building

Urban villages often lag behind the urban planning. Besides, illegal construction is quite concentrated on some certain areas, showing high housing density, poor ventilation as well as lighting conditions, whose dwellers live in harsh environment. First of all, this paper will simulate the physical environment of a urban village in Guangzhou, and analyze the problems in the physical environment of the village from the angle of wind speed distribution, temperature distribution and sunshine time. Secondly, three representative buildings are selected to analyze the indoor physical environment. Finally, some countermeasures are put forward to solve the problems found in the analysis, for example setting the natural ventilators, Wingwall and reflector, strengthening the air tightness of the doors and windows, enhancing the ventilation by the Solar chimney and greening the external wall. Through the above measures, to some extents, it could improve the living environment of the urban village, and provide some reference for the reconstruction of the urban village.