The Experts below are selected from a list of 5172 Experts worldwide ranked by ideXlab platform
Huang Jisheng - One of the best experts on this subject based on the ideXlab platform.
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On-Line Detection of Voltage Transformer Insulation Defects Using the Low-Frequency Oscillation Amplitude and Duration of a Zero Sequence Voltage
Energies, 2019Co-Authors: Hongwen Liu, Ke Wang, Qing Yang, Huang JishengAbstract:The insulation degradation of a Voltage Transformer winding is not easy to find, but it may ultimately cause the Transformer to explode, leading to accidents such as phase-to-phase short circuits. At present, power Transformers, lightning arresters, and other equipment have on-line methods to detect the insulation state. However, there is no mature method for the on-line monitoring of Voltage Transformer winding insulation. In this study, a small current disturbance method based on a zero-sequence loop is proposed. The characteristic parameters of the low-frequency oscillation of zero-sequence Voltage after a disturbance are used to evaluate the insulation state of the winding and detect faults. Theoretical modeling, simulation tests, and field tests show that when the insulation resistance of the Voltage Transformer winding is in the range 0–40 kΩ, a low frequency oscillation of about 10 Hz can be detected on the zero-sequence Voltage, and its amplitude and duration are proportional to the degree of damage to the insulation. This can hence be used as a criterion for the on-line detection of Voltage Transformer winding insulation defects.
Zeng Rong - One of the best experts on this subject based on the ideXlab platform.
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Study on Necessity of OverVoltage Protection for Secondary Winding Neutral-point of Voltage Transformer: Numerical Analysis on Potential Distribution of Ground Grid during Ground Fault or Lightning Stroke
Guangdong Electric Power, 2009Co-Authors: Zeng RongAbstract:In view of the multiple protection misoperation accidents caused by incorrect breakdown of discharge gap at the secondary winding neutral-point of Voltage Transformer in Guangdong power grid in recent years,test and theoretical study are made on the necessity of installing overVoltage protection at the secondary winding neutral-point of Voltage Transformer.Through numerical analysis and experimental verification of the potential difference between two points of substation ground grid under the situation of power-frequency earth fault,direct or extremely near lightning stroke,the transient and stable potential difference levels between two points of ground grid are determined,and the necessity of installing lightning overVoltage protection at the secondary winding neutral-point of Voltage Transformer is confirmed.
Liu Qi - One of the best experts on this subject based on the ideXlab platform.
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Analysis on Arresters as the Protection of Secondary Winding Neutral-point of Voltage Transformer
High Voltage Engineering, 2009Co-Authors: Liu QiAbstract:In order to define the necessity and the technical qualification of the overVoltage protection of secondary winding neutral point of Voltage Transformer,both of the impact transfer Voltage test in the lab and the numerical simulation analysis based on the ATP software were carried out to study the lightning transfer in the neutral point of the secondary winding and potential difference between two points of ground network under the situation of lightning invasion,direct lightning stroke and power frequency grounding fault.As a result,overVoltage level of lightning transmission at the neutral point of the secondary winding,and the potential difference between neutral points of secondary windings under both transient and steady-state situations are determined.The transfer overVoltage in secondary circuit of Voltage Transformer especially in capacitive one will largely exceed the lightning impulse level of the neutral point in secondary circuit when the amplitude of lightning overVoltage is high or the rise time is fast.It is necessary to install ZnO arrester on site to protect the Transformer from the overVoltage of the neutral point of the secondary winding.Six kinds of developed ZnO arresters are installed in neutral point of secondary winding to test the protection effectiveness through the the impact transfer Voltage test in the lab and the numerical simulation analysis.The results show it is an effective protection in the neutral point insulation of secondary even in a worst situation with large amplitude and steep waveform of overVoltage.
Hongwen Liu - One of the best experts on this subject based on the ideXlab platform.
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On-Line Detection of Voltage Transformer Insulation Defects Using the Low-Frequency Oscillation Amplitude and Duration of a Zero Sequence Voltage
Energies, 2019Co-Authors: Hongwen Liu, Ke Wang, Qing Yang, Huang JishengAbstract:The insulation degradation of a Voltage Transformer winding is not easy to find, but it may ultimately cause the Transformer to explode, leading to accidents such as phase-to-phase short circuits. At present, power Transformers, lightning arresters, and other equipment have on-line methods to detect the insulation state. However, there is no mature method for the on-line monitoring of Voltage Transformer winding insulation. In this study, a small current disturbance method based on a zero-sequence loop is proposed. The characteristic parameters of the low-frequency oscillation of zero-sequence Voltage after a disturbance are used to evaluate the insulation state of the winding and detect faults. Theoretical modeling, simulation tests, and field tests show that when the insulation resistance of the Voltage Transformer winding is in the range 0–40 kΩ, a low frequency oscillation of about 10 Hz can be detected on the zero-sequence Voltage, and its amplitude and duration are proportional to the degree of damage to the insulation. This can hence be used as a criterion for the on-line detection of Voltage Transformer winding insulation defects.
Wei Xue-ying - One of the best experts on this subject based on the ideXlab platform.
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The Error Analysis And Verification of 500kV Voltage Transformer Calibration System
Electrical Measurement & Instrumentation, 2005Co-Authors: Wei Xue-yingAbstract:This paper introduces measurement principle of new 500kV Voltage Transformer calibration system,analyses the error origin of the calibration system,calculates the uncertainty in measurement,testes and verifies the accuracy of the calibration system.
