Voltage measuring equipment in power grids often requires capacitive voltage dividers to realize conversion of high voltage electrical quantities to low voltage signal quantities.The new floating-ground capacitive vol...Voltage measuring equipment in power grids often requires capacitive voltage dividers to realize conversion of high voltage electrical quantities to low voltage signal quantities.The new floating-ground capacitive voltage divider(FG-CVD)can eliminate original lumped capacitors and its supporting insulation structures by adopting precisely designed parasitic capacitance as a high voltage arm capacitor,which can greatly save cost and volume.However,the utilization of parasitic capacitance not only makes FG-CVD sensitive to external conductor interference,but also causes transient waveform distortion,especially when the connecting lead between the FG-CVD and high-voltage conductor is lengthy.On the basis of transfer characteristic analysis,this paper proposes a complete parameter design method for FG-CVD to improve stability of its transfer ratio under interference of the external conductor.Moreover,by establishing a wideband equivalent model with lead inductance,the transient waveform distortion problem of FG-CVD is well explained,and a resistance compensation scheme is also proposed to reduce ratio error.Finally,a 500:1 FG-CVD prototype with a measurement bandwidth of 2MHz is developed.Experimental results show the prototype has high accuracy in both power frequency and lightning pulse voltage measurement,and ratio error decreases from 20.33%to less than 1.3%.展开更多
A high performance current and voltage measurement system has been developed in power system. The system is composed of two parts: one current measurement element and one voltage measurement element. A Rogowski coil ...A high performance current and voltage measurement system has been developed in power system. The system is composed of two parts: one current measurement element and one voltage measurement element. A Rogowski coil and a capacitive voltage divider are used respectively for the line current and voltage measurements. Active electronic components are used to modulate signal, and power supply for these components is drawn from power line via an auxiliary current transformer. Measurement signal is transmitted by optical fibers, which is resistant to electromagnetic induction and noise. With careful design and the use of digital signal processing technology, the whole system can meet 0.5% accuracy for metering and provides large dynamic range coupled with good accuracy for protective relaying use.展开更多
With the increase of the operating voltage and enlargement of the size of the capacitor voltage transformer(CVT),the additional measurement error caused by stray capacitance coupling and leakage current along the poll...With the increase of the operating voltage and enlargement of the size of the capacitor voltage transformer(CVT),the additional measurement error caused by stray capacitance coupling and leakage current along the polluted surface of the CVT becomes noticeable.The equipotential shielding CVT(EPSCVT)was proposed and designed by the authors to mitigate these effects.An improved conceptual design option of the EPS-CVT is presented in this paper with special references to this study to improve the shielding effect without the increase of shielding capacitance.A proposed method of non-uniform capacitance configuration can improve the shielding effect significantly without an increase of the external shielding capacitance.Based on this achievement,the potential difference and the capacitive current exchange between the internal measuring system and external shielding systems are significantly reduced.In the evaluation of the shielding effect for the influence of stray capacitance,compared with a conventional CVT with equal capacitance,EPS-CVT can reduce the measurement error by two orders of magnitude.In addition,the measurement error caused by the leakage current can also be greatly reduced,especially for the reduction of the phase angle error.Based on the improved design method,a design scheme for an engineering application is proposed which can achieve effective shielding while ensuring as good a technical performance as the existing CVT.展开更多
基金supported by the Science and Technology Project of SGCC under Contract 5500-202140126A-0-0-00.
文摘Voltage measuring equipment in power grids often requires capacitive voltage dividers to realize conversion of high voltage electrical quantities to low voltage signal quantities.The new floating-ground capacitive voltage divider(FG-CVD)can eliminate original lumped capacitors and its supporting insulation structures by adopting precisely designed parasitic capacitance as a high voltage arm capacitor,which can greatly save cost and volume.However,the utilization of parasitic capacitance not only makes FG-CVD sensitive to external conductor interference,but also causes transient waveform distortion,especially when the connecting lead between the FG-CVD and high-voltage conductor is lengthy.On the basis of transfer characteristic analysis,this paper proposes a complete parameter design method for FG-CVD to improve stability of its transfer ratio under interference of the external conductor.Moreover,by establishing a wideband equivalent model with lead inductance,the transient waveform distortion problem of FG-CVD is well explained,and a resistance compensation scheme is also proposed to reduce ratio error.Finally,a 500:1 FG-CVD prototype with a measurement bandwidth of 2MHz is developed.Experimental results show the prototype has high accuracy in both power frequency and lightning pulse voltage measurement,and ratio error decreases from 20.33%to less than 1.3%.
文摘A high performance current and voltage measurement system has been developed in power system. The system is composed of two parts: one current measurement element and one voltage measurement element. A Rogowski coil and a capacitive voltage divider are used respectively for the line current and voltage measurements. Active electronic components are used to modulate signal, and power supply for these components is drawn from power line via an auxiliary current transformer. Measurement signal is transmitted by optical fibers, which is resistant to electromagnetic induction and noise. With careful design and the use of digital signal processing technology, the whole system can meet 0.5% accuracy for metering and provides large dynamic range coupled with good accuracy for protective relaying use.
文摘With the increase of the operating voltage and enlargement of the size of the capacitor voltage transformer(CVT),the additional measurement error caused by stray capacitance coupling and leakage current along the polluted surface of the CVT becomes noticeable.The equipotential shielding CVT(EPSCVT)was proposed and designed by the authors to mitigate these effects.An improved conceptual design option of the EPS-CVT is presented in this paper with special references to this study to improve the shielding effect without the increase of shielding capacitance.A proposed method of non-uniform capacitance configuration can improve the shielding effect significantly without an increase of the external shielding capacitance.Based on this achievement,the potential difference and the capacitive current exchange between the internal measuring system and external shielding systems are significantly reduced.In the evaluation of the shielding effect for the influence of stray capacitance,compared with a conventional CVT with equal capacitance,EPS-CVT can reduce the measurement error by two orders of magnitude.In addition,the measurement error caused by the leakage current can also be greatly reduced,especially for the reduction of the phase angle error.Based on the improved design method,a design scheme for an engineering application is proposed which can achieve effective shielding while ensuring as good a technical performance as the existing CVT.
