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

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1466 ◽  
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.

scholarly journals Evaluation of Methodology for Lightning Impulse Voltage Distribution over High-Voltage Windings of Inductive Voltage Transformers

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5144
Author(s):  
Bojan Trkulja ◽  
Ana Drandić ◽  
Viktor Milardić ◽  
Igor Žiger
Keyword(s):  
High Voltage ◽  
Equivalent Circuit Model ◽  
Boundary Element Methods ◽  
Design Stage ◽  
Iron Core ◽  
Voltage Distribution ◽  
Specific Design ◽  
Impulse Voltage ◽  
Lightning Impulse ◽  
Capacitance Matrix

Knowledge of lightning impulse (LI) voltage distribution over transformer windings during the design stage of the transformer is very important. Specific design differences in inductive voltage transformers make the transient analysis approach different to the approach to the power transformers. In this paper, a methodology for acquiring lightning impulse voltage distribution over high-voltage (HV) winding of inductive voltage transformers is presented and evaluated. Resistance, inductance, and capacitance matrices are calculated using the integral and boundary element methods (BEM) approach. Additionally, in order to improve the capacitance matrix solver, adaptive cross approximation (ACA) is applied. These parameters are then used to solve the equivalent circuit model in time domain. In order to evaluate the methodology, an experimental and numerical investigation of the layer discretisation, iron core influence, and accuracy of the proposed methodology is performed. The comparison of numerical results with measurements confirms the validity of the methodology.

The Measurement of the Voltage Distribution along High Voltage Suspension Porcelain (5-6-7 Insulator)/String in Case of Clean Condition

2015 ◽  
Vol 752-753 ◽  
pp. 1133-1138 ◽  
Author(s):  
Norrawit Tonmitr ◽  
Eiji Kaneko ◽  
Kittipong Tonmitr ◽  
Arkom Kaewrawang ◽  
Amnart Suksri
Keyword(s):  
Equivalent Circuit ◽  
High Voltage ◽  
Material Properties ◽  
Research Laboratory ◽  
Experimental Results ◽  
Guard Ring ◽  
Voltage Distribution ◽  
Porcelain Insulator ◽  
Power Frequency ◽  
Simulation Results

The operational voltage or the voltage distribution along porcelain insulator string is affected by stray capacitances, which causes a non-uniform voltage distribution. The recital of insulator sometimes depends on the amount of insulator/string. In order to explain these activities and phenomena clearly in this research, an equivalent circuit that takes the insulator material properties and the stray capacitances is implemented in the TINA program package to analyze the voltage distribution along the insulator string with and without guard ring under power frequency voltage. Finally, the simulation results of voltage distribution have been compared with experimental results, which were obtained in the KKU High Voltage Research Laboratory. To investigate the voltage along across each (5, 6, 7) insulator/string in clean condition, the string efficiency has been measured by sphere gap method. From the simulation results, the voltage across (5, 6, 7 clean and contaminated insulator/string) with and without guard ring were simulated by the TINA program. From this simulation results, we found that the string efficiency of clean string insulator condition which the insulator consists of 5, 6, 7 insulator/string without guard ring equals 66.92, 58.45 and 53.71%, respectively. The string efficiency which the insulator consists of 5, 6, 7 insulator/string with guard ring equals 90.42, 87.03 and 78.35%, respectively. In the experiment, the sphere gap was used to measure the voltage along insulation string. In case of the clean string insulator condition, the string efficiency which the insulator consists of 5, 6, 7 insulator/string without guard ring equals 69.12, 62.67 and 57.04%, respectively. The string efficiency which the insulator consists of 5, 6, 7 insulator/string with guard ring equals 76.36, 66.69 and 59.76%, respectively.

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