The assessment of the measurement error status of online Capacitor Voltage Transformers (CVT) within the power grid is of profound significance to the equitable trade of electric energy and the secure operation of the...The assessment of the measurement error status of online Capacitor Voltage Transformers (CVT) within the power grid is of profound significance to the equitable trade of electric energy and the secure operation of the power grid. This paper advances an online CVT error state evaluation method, anchored in the in-phase relationship and outlier detection. Initially, this method leverages the in-phase relationship to obviate the influence of primary side fluctuations in the grid on assessment accuracy. Subsequently, Principal Component Analysis (PCA) is employed to meticulously disentangle the error change information inherent in the CVT from the measured values and to compute statistics that delineate the error state. Finally, the Local Outlier Factor (LOF) is deployed to discern outliers in the statistics, with thresholds serving to appraise the CVT error state. Experimental results incontrovertibly demonstrate the efficacy of this method, showcasing its prowess in effecting online tracking of CVT error changes and conducting error state assessments. The discernible enhancements in reliability, accuracy, and sensitivity are manifest, with the assessment accuracy reaching an exemplary 0.01%.展开更多
Output voltage is an important performance characteristic of planar insulating core transformer (PICT).In PICT magnetic cores are insulated from their neighboring magnetic cores by solid insulating materials.Solid ins...Output voltage is an important performance characteristic of planar insulating core transformer (PICT).In PICT magnetic cores are insulated from their neighboring magnetic cores by solid insulating materials.Solid insulating materials can increase leakage flux.This results in a low generated voltage in secondary coils,especially on the upper stages.Connecting flux compensation capacitors to secondary coils can compensate the flux loss.Design equations to calculate the flux compensation capacitors value and relevant simulation by CST and Protel software were presented.Simulation results of an actual PICT showed that output voltage increased by 19% after being connected to flux compensation capacitors and the voltage on every stage was equally distributed.Results of simulation were consistent with the following experimental test,which revealed that flux compensation capacitors were effective.展开更多
The main purpose of the electrical power system is to transport and distribute energy generated by the central power plants in a safe and reliable manner to the customer premises. Most of the electrical equipment is e...The main purpose of the electrical power system is to transport and distribute energy generated by the central power plants in a safe and reliable manner to the customer premises. Most of the electrical equipment is exposed within the open which suggests they can be vulnerable to lightning strikes, road dwindling, windstorms, and a few engineering activities with the potential of causing different degrees of damage to the electrical equipment. One of the ways to guard the equipment is to deploy switching devices. However, the operations of most of these switching devices produce oscillatory transient in the electrical transmission and distribution systems which result in voltage, current, and frequency fluctuations in the load. This paper investigates the effect of switching devices on power quality and proposes a positive sequence voltage power transient suppression technique that can spontaneously improve the distorted voltage at the instant of capacitor switching using the capacitor line model as a case study. MATLAB/Simulink software was utilized for the analysis on an electrical network model with bus voltages of 69 kV/12.47 kV and 480 V. The results showed that, during switching operations, the positive sequence voltage power detector block produces ripple-free accurate results.展开更多
This article presents an extensive examination and modeling of Capacitor Coupled Substations (CCS), noting some of their inherent constraints. The underlying implementation of a CCS is to supply electricity directly f...This article presents an extensive examination and modeling of Capacitor Coupled Substations (CCS), noting some of their inherent constraints. The underlying implementation of a CCS is to supply electricity directly from high-voltage (HV) transmission lines to low-voltage (LV) consumers through coupling capacitors and is said to be cost-effective as compared to conventional distribution networks. However, the functionality of such substations is susceptible to various transient phenomena, including ferroresonance and overvoltage occurrences. To address these challenges, the study uses simulations to evaluate the effectiveness of conventional resistor-inductor-capacitor (RLC) filter in mitigating hazardous overvoltage resulting from transients. The proposed methodology entails using standard RLC filter to suppress transients and its associated overvoltage risks. Through a series of MATLAB/Simulink simulations, the research emphasizes the practical effectiveness of this technique. The study examines the impact of transients under varied operational scenarios, including no-load switching conditions, temporary short-circuits, and load on/off events. The primary aim of the article is to assess the viability of using an established technology to manage system instabilities upon the energization of a CCS under no-load circumstances or in case of a short-circuit fault occurring on the primary side of the CCS distribution transformer. The findings underscore the effectiveness of conventional RLC filters in suppressing transients induced by the CCS no-load switching.展开更多
为保证电网安全、稳定和可靠运行,对系统暂态过电压进行监测研究,从而采取相关措施解决其危害是具有重要意义的。文中基于500 kV电容式电压互感器(capacitor voltage transformer,CVT)对电网暂态过电压在线监测技术进行了系统研究。采...为保证电网安全、稳定和可靠运行,对系统暂态过电压进行监测研究,从而采取相关措施解决其危害是具有重要意义的。文中基于500 kV电容式电压互感器(capacitor voltage transformer,CVT)对电网暂态过电压在线监测技术进行了系统研究。采取改造CVT即内置串联低压电容C3形成可靠的耦合分压装置、雷电和操作冲击试验及分析结果表明,其性能满足电网暂态监测要求。基于该分压装置研制了一套智能型暂态过电压监测系统,在实验室通过了相关性能测试,主要为开关动作的单分、单合、重合闸、分合分以及工频电压耦合操作冲击模拟试验电压波形记录。在上述基础上,结合华东电网"瓶窑500 kV变电站配串调整工程"进行了现场安装和立屏,就窑阳5438线启动调试进行了录波。最后对后期运行监测获取的电网暂态过电压典型波形进行了示例,进一步说明该在线监测技术及系统在现场长期应用的可行性和可靠性。展开更多
电容式电压互感器(CVT Capacitor Voltage Transformer)含有电容和非线性电感元件,当一次隔离开关操作时可能引起二次电压异常,影响变电站继电保护装置的正常运行,甚至引起主变过励磁保护误动作。运用ATP建立CVT及其所运行的变电站的等...电容式电压互感器(CVT Capacitor Voltage Transformer)含有电容和非线性电感元件,当一次隔离开关操作时可能引起二次电压异常,影响变电站继电保护装置的正常运行,甚至引起主变过励磁保护误动作。运用ATP建立CVT及其所运行的变电站的等值电路模型,仿真计算一次侧隔离开关操作过程中CVT二次电压情况。比较影响二次侧电压的主要因素,分析在CVT一次侧隔离开关操作过程中主变过励磁保护误动作的原因。正常操作不会引起主变过励磁保护误动作。展开更多
文摘The assessment of the measurement error status of online Capacitor Voltage Transformers (CVT) within the power grid is of profound significance to the equitable trade of electric energy and the secure operation of the power grid. This paper advances an online CVT error state evaluation method, anchored in the in-phase relationship and outlier detection. Initially, this method leverages the in-phase relationship to obviate the influence of primary side fluctuations in the grid on assessment accuracy. Subsequently, Principal Component Analysis (PCA) is employed to meticulously disentangle the error change information inherent in the CVT from the measured values and to compute statistics that delineate the error state. Finally, the Local Outlier Factor (LOF) is deployed to discern outliers in the statistics, with thresholds serving to appraise the CVT error state. Experimental results incontrovertibly demonstrate the efficacy of this method, showcasing its prowess in effecting online tracking of CVT error changes and conducting error state assessments. The discernible enhancements in reliability, accuracy, and sensitivity are manifest, with the assessment accuracy reaching an exemplary 0.01%.
文摘Output voltage is an important performance characteristic of planar insulating core transformer (PICT).In PICT magnetic cores are insulated from their neighboring magnetic cores by solid insulating materials.Solid insulating materials can increase leakage flux.This results in a low generated voltage in secondary coils,especially on the upper stages.Connecting flux compensation capacitors to secondary coils can compensate the flux loss.Design equations to calculate the flux compensation capacitors value and relevant simulation by CST and Protel software were presented.Simulation results of an actual PICT showed that output voltage increased by 19% after being connected to flux compensation capacitors and the voltage on every stage was equally distributed.Results of simulation were consistent with the following experimental test,which revealed that flux compensation capacitors were effective.
文摘The main purpose of the electrical power system is to transport and distribute energy generated by the central power plants in a safe and reliable manner to the customer premises. Most of the electrical equipment is exposed within the open which suggests they can be vulnerable to lightning strikes, road dwindling, windstorms, and a few engineering activities with the potential of causing different degrees of damage to the electrical equipment. One of the ways to guard the equipment is to deploy switching devices. However, the operations of most of these switching devices produce oscillatory transient in the electrical transmission and distribution systems which result in voltage, current, and frequency fluctuations in the load. This paper investigates the effect of switching devices on power quality and proposes a positive sequence voltage power transient suppression technique that can spontaneously improve the distorted voltage at the instant of capacitor switching using the capacitor line model as a case study. MATLAB/Simulink software was utilized for the analysis on an electrical network model with bus voltages of 69 kV/12.47 kV and 480 V. The results showed that, during switching operations, the positive sequence voltage power detector block produces ripple-free accurate results.
文摘This article presents an extensive examination and modeling of Capacitor Coupled Substations (CCS), noting some of their inherent constraints. The underlying implementation of a CCS is to supply electricity directly from high-voltage (HV) transmission lines to low-voltage (LV) consumers through coupling capacitors and is said to be cost-effective as compared to conventional distribution networks. However, the functionality of such substations is susceptible to various transient phenomena, including ferroresonance and overvoltage occurrences. To address these challenges, the study uses simulations to evaluate the effectiveness of conventional resistor-inductor-capacitor (RLC) filter in mitigating hazardous overvoltage resulting from transients. The proposed methodology entails using standard RLC filter to suppress transients and its associated overvoltage risks. Through a series of MATLAB/Simulink simulations, the research emphasizes the practical effectiveness of this technique. The study examines the impact of transients under varied operational scenarios, including no-load switching conditions, temporary short-circuits, and load on/off events. The primary aim of the article is to assess the viability of using an established technology to manage system instabilities upon the energization of a CCS under no-load circumstances or in case of a short-circuit fault occurring on the primary side of the CCS distribution transformer. The findings underscore the effectiveness of conventional RLC filters in suppressing transients induced by the CCS no-load switching.
文摘为保证电网安全、稳定和可靠运行,对系统暂态过电压进行监测研究,从而采取相关措施解决其危害是具有重要意义的。文中基于500 kV电容式电压互感器(capacitor voltage transformer,CVT)对电网暂态过电压在线监测技术进行了系统研究。采取改造CVT即内置串联低压电容C3形成可靠的耦合分压装置、雷电和操作冲击试验及分析结果表明,其性能满足电网暂态监测要求。基于该分压装置研制了一套智能型暂态过电压监测系统,在实验室通过了相关性能测试,主要为开关动作的单分、单合、重合闸、分合分以及工频电压耦合操作冲击模拟试验电压波形记录。在上述基础上,结合华东电网"瓶窑500 kV变电站配串调整工程"进行了现场安装和立屏,就窑阳5438线启动调试进行了录波。最后对后期运行监测获取的电网暂态过电压典型波形进行了示例,进一步说明该在线监测技术及系统在现场长期应用的可行性和可靠性。
文摘电容式电压互感器(CVT Capacitor Voltage Transformer)含有电容和非线性电感元件,当一次隔离开关操作时可能引起二次电压异常,影响变电站继电保护装置的正常运行,甚至引起主变过励磁保护误动作。运用ATP建立CVT及其所运行的变电站的等值电路模型,仿真计算一次侧隔离开关操作过程中CVT二次电压情况。比较影响二次侧电压的主要因素,分析在CVT一次侧隔离开关操作过程中主变过励磁保护误动作的原因。正常操作不会引起主变过励磁保护误动作。
