Analysis of winding temperature field under dynamic variable load of oil-immersed transformer

The research on the temperature field of the transformer winding under dynamic variable load is of great significance for ensuring the safe operation of power systems. This paper takes an SSP-360000/500 transformer as the research object, establishes a 2-D simulation model, and uses the finite volume method to analyze the high voltage winding and low voltage winding temperature distribution of the transformer under dynamic variable load. The simulation calculation results have been fully verified by the experimental data to make the successful prediction of the overall temperature and hot spot temperature position of forced oil circulation transformers with a guided structure. The results show that the most significant temperature raise occurs at the secondary end of the winding. In the case of dynamic variable load. The temperature raise of the winding becomes larger as the load increases, but before the rated load is in the stable temperature rise range, it can run safely for a long time. However, during overload operation, the average temperature raise of the high voltage winding may exceed its limit, the insulation material is damaged.

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Calculation of the Internal Temperature Field of Transformer by the Method of Combination the Finite Element and the Finite Volume

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1079-1080.492 ◽

2014 ◽

Vol 1079-1080 ◽

pp. 492-497 ◽

Cited By ~ 1

Author(s):

Lun Ma ◽

Liu Wang ◽

Ying Ying Sun ◽

Tao Wan ◽

Jia Peng Wei ◽

...

Keyword(s):

Temperature Field ◽

Mixed Method ◽

Hot Spot ◽

Three Dimensional ◽

Internal Temperature ◽

Accurate Calculation ◽

Calculation Results ◽

Transformer Winding ◽

Regulatory Model ◽

Spot Temperature

Oil immersed transformer is an important equipment ofpower system, whose fault is often caused by the aging of insulation. In actualoperation, accurate calculation of the temperature field, especially hot spottemperature of transformer winding, is very important for stabilizing the powergrid operation and extending the transformer life. In order to calculate thetransformer's hot spot temperature accurately, a new method which is based oncomparison of respective advantages of the FEM and FVM is used; we take a31.5MVA transformer as exemple, using the hybrid method of the FEM and the FVM,the three-dimensional temperature field of transformer is calculated. Bycomparing the figures of top oil temperature of transformer monitored by theoperating transformer and the figures calculated by mixed method, the marginerror of the hot spot temperature is only 1.9°C. While the IEEE guidelines formodel calculation results, the calculated results of FEM algorithm and FVMalgorithm results with the monitoring data of standard deviation were as highas 4.6 °C, 3.8 °C and 3.1 °C. The Calculation accuracy is much higher than theaccuracy of the result using IEEE regulatory model, FEM and FVM, proved thatthis mixed method can calculate the internal temperature field of oil immersedtransformer accurately.

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Thermal optimization research of oil-immersed transformer winding based on the support machine response surface

Thermal Science ◽

10.2298/tsci210530264y ◽

2021 ◽

pp. 264-264

Author(s):

Fating Yuan ◽

Wentao Yang ◽

Bo Tang ◽

Yue Wang ◽

Fa Jiang ◽

...

Keyword(s):

Response Surface ◽

Low Voltage ◽

Hot Spot ◽

Optimization Method ◽

Design Parameters ◽

Support Vector ◽

Structure Parameters ◽

Transformer Winding ◽

Polynomial Response Surface ◽

Spot Temperature

In this paper, the CFD (computational fluid dynamics) model is established for the low voltage winding region of an oil-immersed transformer according to the design parameters, and the detailed temperature distribution within the region is obtained by numerical simulation. On this basis, the RSM (response surface methodology) is adopted to optimize the structure parameters with the purpose of minimizing the hot spot temperature. After a sequence of designed experiments, the second-order polynomial response surface and the SVM (support vector machine) response surface are established respectively. The analysis of their errors shows that the SVM response surface can be better used to fit the approximation. Finally, the PSO (particle swarm optimization) algorithm is employed to get the optimal structure parameters of the winding based on the SVM response surface. The results show that the optimization method can significantly reduce the hot spot temperature of the winding, which provides a guiding direction for the optimal design of the winding structure of transformers.

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Research of Temperature Field in Oil-Immersed Transformer Considering the Oil Speed

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.912-914.1041 ◽

2014 ◽

Vol 912-914 ◽

pp. 1041-1045

Author(s):

Guo Liang Yue ◽

Yong Qiang Wang ◽

Jie He ◽

Hong Liang Liu

Keyword(s):

Temperature Field ◽

Hot Spot ◽

Element Model ◽

Thermal Coupling ◽

Normal Range ◽

Steady State Temperature ◽

Oil Flow ◽

Transformer Winding ◽

The Mathematical Model ◽

Spot Temperature

In this paper, we have Elaborated the mathematical model of temperature field and flow field of the oil-immersed transformer, and analysis its structure of thermal .We established a temperature finite element model of an oil-immersed transformer using the method of flow-solid-thermal coupling. Using the software of ANSYS, simulating on a 250MVA oil-immersed transformer, we obtain the steady-state temperature distribution and the winding hottest locations. Analyze the effect of oil-speed to the temperature field and location of the hot spot temperature of oil-immersed transformer. The results show that when oil flow rate is increases in the normal range, Transformer temperature rise corresponding slowly, and its location hottest temperature slightly pulled accordingly. The fiber measure different speeds Oil immersed transformer winding hot spot temperature to provide a basis for positioning.

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Influence of HVDC Transmission on DC Bias of AC Grid and Its Treatment

10.3233/atde210306 ◽

2021 ◽

Author(s):

Ruifeng Zhan ◽

Yuying Hu ◽

Fan Li ◽

Zhou Mi ◽

Lingpeng Dong

Keyword(s):

High Voltage ◽

Direct Current ◽

Power Grid ◽

Hvdc Transmission ◽

High Voltage Direct Current ◽

Grid Topology ◽

Treatment Measures ◽

Calculation Results ◽

Transformer Winding ◽

Dc Bias

With the rapid development of China’s electric power industry, the high-voltage and long-distance direct current (DC) transmission effectively solved the problem of uneven power distribution. When the high voltage direct current transmission is in unipolar operation or bipolar asymmetric operation, part of the DC current will flow into the transformer winding through the grounded neutral point, which will cause the DC bias problem. This article used CDEGS software for modeling, and introduced the process of CDEGS software for DC bias simulation modeling. In this paper, the DC bias model of regional power grid is first established, based on the Zhejiang power grid topology and the test soil resistivity date. Then the DC bias currents of the transformers are calculated, and finally the corresponding treatment measures are proposed. According to the governance measures, this article adjusted the simulation model. The calculation results show that the treatment measures have good effects, which can provide an important reference for the future treatment of transformer DC bias.

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Investigation on the Resonant Oscillations in an 11 kV Distribution Transformer under Standard and Chopped Lightning Impulse Overvoltages with Different Shield Placement Configurations

Energies ◽

10.3390/en12081466 ◽

2019 ◽

Vol 12 (8) ◽

pp. 1466 ◽

Cited By ~ 2

Author(s):

Murthy ◽

Azis ◽

Yousof ◽

Jasni ◽

Othman ◽

...

Keyword(s):

Equivalent Circuit ◽

High Voltage ◽

Low Voltage ◽

Stress Distributions ◽

Voltage Distribution ◽

Distribution Transformer ◽

Resonant Oscillation ◽

Initial Voltage ◽

Transformer Winding ◽

Lightning Impulse

This paper presents an investigation on the resonant oscillations of an 11 kV layer-type winding transformer under standard and chopped lightning impulse overvoltage conditions based on calculated parameters. The resistances, inductances and capacitances were calculated in order to develop the transformer winding equivalent circuit. The impulse overvoltages were applied to the high voltage (HV) winding and the resonant oscillations were simulated for each of the layers based on different electrostatic shield placement configurations. It is found that the placement of grounded shields between layer 13 and layer 14 results in the highest resonant oscillation and non-linear initial voltage distribution. The oscillation and linear stress distributions are at the lowest for shield placement between the HV and low voltage (LV) windings.

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Wide Load Range ZVS Three-level DC-DC Converter: Modular Structure, Redundancy Ability, and Reduced Filters Size

Energies ◽

10.3390/en12183537 ◽

2019 ◽

Vol 12 (18) ◽

pp. 3537 ◽

Cited By ~ 1

Author(s):

Yong Shi ◽

Zhuoyi Xu

Keyword(s):

Power Systems ◽

High Voltage ◽

High Performance ◽

Low Voltage ◽

Modular Architecture ◽

Load Range ◽

Zero Voltage Switching ◽

Conduction Loss ◽

Zero Current Switching ◽

Zero Current

In future dc distributed power systems, high performance high voltage dc-dc converters with redundancy ability are welcome. However, most existing high voltage dc-dc converters do not have redundancy ability. To solve this problem, a wide load range zero-voltage switching (ZVS) three-level (TL) dc-dc converter is proposed, which has some definitely good features. The primary switches have reduced voltage stress, which is only Vin/2. Moreover, no extra clamping component is needed, which results simple primary structure. Redundancy ability can be obtained by both primary and secondary sides, which means high system reliability. With proper designing of magnetizing inductance, all primary switches can obtain ZVS down to 0 output current, and in addition, the added conduction loss can be neglected. TL voltage waveform before the output inductor is obtained, which leads small volume of the output filter. Four secondary MOSFETs can be switched in zero-current switching (ZCS) condition over wide load range. Finally, both the primary and secondary power stages are modular architecture, which permits realizing any given system specifications by low voltage, standardized power modules. The operation principle, soft switching characteristics are presented in this paper, and the experimental results from a 1 kW prototype are also provided to validate the proposed converter.

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Bidirectional Interleaved PWM Converter with High Voltage-Conversion Ratio and Automatic Current Balancing Capability for Single-Cell Battery Power System in Small Scientific Satellites

Energies ◽

10.3390/en11102702 ◽

2018 ◽

Vol 11 (10) ◽

pp. 2702 ◽

Cited By ~ 6

Author(s):

Masatoshi Uno ◽

Masahiko Inoue ◽

Yusuke Sato ◽

Hikaru Nagata

Keyword(s):

Power Systems ◽

Single Cell ◽

High Voltage ◽

Pulse Width Modulation ◽

Low Voltage ◽

Conversion Ratio ◽

Pwm Converter ◽

Bidirectional Converters ◽

Battery Power ◽

Voltage Conversion

Single-cell battery power systems are a promising bus architecture for small scientific satellites. However, to bridge the huge voltage gap between a single-cell battery and power bus, bidirectional converters with a high voltage conversion ratio and a large current capability for the low-voltage side are necessary. This article proposes a bidirectional interleaved pulse width modulation (PWM) converter with a high voltage conversion ratio and an automatic current balancing capability. By adding capacitors to conventional interleaved PWM converters, not only are inductor currents automatically balanced without feedback control or current sensors, but also voltage conversion ratios at a given duty cycle can be enhanced. Furthermore, the added capacitors can reduce voltage stresses of switches and charged-discharged energies of inductors, realizing more efficient power conversion and reduced circuit volume in comparison with conventional converters. A 100-W prototype was built for experimental verification, and results demonstrated the fundamental characteristics and efficacy of the proposed converter.

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Development of Broadband Resistive–Capacitive Parallel–Connection Voltage Divider for Transient Voltage Monitoring

Energies ◽

10.3390/en15020451 ◽

2022 ◽

Vol 15 (2) ◽

pp. 451

Author(s):

Shijun Xie ◽

Zhou Mu ◽

Weidong Ding ◽

Zhenbo Wan ◽

Shaochun Su ◽

...

Keyword(s):

Power Systems ◽

High Voltage ◽

Low Voltage ◽

Influence Factors ◽

Voltage Divider ◽

Step Response ◽

Internal Electric Field ◽

Scale Factors ◽

Different Temperatures ◽

Transient Voltages

The on-site measurement of transient voltages is of great significance in analyzing the fault cause of power systems and optimizing the insulation coordination of power equipment. Conventional voltage transformers normally have a narrow bandwidth and are unable to accurately measure various transient voltages in power systems. In this paper, a wideband parallel resistive–capacitive voltage divider is developed, which can be used for online monitoring of transient voltages in a 220 kV power grid. The structures of the high-voltage and low-voltage arms were designed. The internal electric field distribution of the high-voltage arm was analyzed. The influence factors and improvement techniques of the upper frequency limit were studied. The parameters of the elements of the divider were determined. The voltage withstand performances and scale factors under lightning impulses and AC and DC voltages, the temperature stabilities of scale factors and the step response and bandwidth of the developed voltage divider were tested. The results show that the deviations of the scale factors under various voltage waveforms and different temperatures ranging from −20 to 40 °C are within 3%. The withstand voltage meets the relevant requirements specified in IEC60071-1-2011. The step response 10~90% rise time is approximately 29 ns, and the 3 dB bandwidth covers the range of DC to 10 MHz.

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