【正文】 fold of the rate current (400 A).6　System Performance　The prototype of a bined electronic current and voltage transducer for a single conductor construction was tested for a 110 kV power system. An overview of primary test results is described below.　The ratio error characteristics of electronic current transducer at room temperature is shown in ratio error is represented on the vertical axis,while the primary current flowing to the conductor is represented on the abscissa. This figure indicates the relationship between the RMS(rootmeansquare)value of the output waveform of the optical interface andthe RMS value of the waveform of the primary currentas measured by a class coiltype CT. The output of Rogowski coil is designed to be 400 mV corresponding to the 400 A rate primary current, and the parameters of integrator arer=10 kΩ,C=. It may be seen from this figure that the ratio error of the ECT is at a range of177。%. As discussed above,signal is demodulated by software, so it is convenient to revise error by using digital signal processing technique, and higher measurement accuracy of % is expected to obtain. The measured phase error of current is better than 20 minutes at twenty percent of full load current at 50 Hz.　 shows voltage transducer test results. Both the high voltage capacitors in series and the low voltage capacitors are polypropylene capacitors. The test was carried out at room temperature. This figure indicates the relationship between the RMS value of the output waveform of the optical interface in control room and the RMS value of the waveform of the high voltage as measured by a class standard conventional PT. The low voltage is represented on the vertical axis, while the high voltage is represented on the abscissa. The linearity of the electronic voltage transducer was measured to meet the accuracy (%) of the measurement system. The phase error of voltage is better than 30 minutes when the voltage is over than 20% percent of the full scale.7 Conclusion　A bined digital electronic current and voltage measurement system has been described, which offers many advantages pared with the conventional CTs and PTs. These can be summarized as follow.(1) High measurement accuracy can be acquired with Rogowski coil and precise capacitive voltage divider, and it is convenient to revise error by software. The system is expected to have % class accuracy.(2) Wide measurement range and frequency range. Rogowski coils do not measure direct current, but unlike CTs, they can accurately measure currents when a large DC ponent is present, because there is no iron to saturate.(3) The bined structure of current and voltage measurements leads to small size, low weight and simple insulation structure.(4) Galvanic insulation from the high voltage with optical fiber. This poses of reliable noncontact measurement system with low insulation cost and strong resistant to EMI.(5) The system’s temperature characteristic is determined by the temperature sensitivity of the electronic elements, which is less than 50106/℃ by using advanced products.(6) The increased patibility with new electronic relay and metering equipment has been currently developed.　Further work is proceeding to put the bined digital electronic current and voltage measurement system into practical application.References[1]The Emerging Technologies Working Group. Optical current transducers for power systems: A review[J].IEEE Transactions on Power Delivery,1994,9(4):17781788.[2]Maffetone T D, McClelland T Substation optical current measurement system for revenue metering and protective relaying[J].IEEE Transactions on Power Delivery,1991,6(4):14301436.[3]Christensen Lars H. Design construction and test of a passive optical prototype high voltage instrument transformer [J].IEEE Trans. on PD,1995,10(3):13321337.[4]Instruction Book of Sensors [ M]. RITZ Messwandler Hamburg, Germany, .[5]Ramboz John D. Machinable Rogowski coils, design and calibration[J].IEEE Transactions on instrumentation and Measurement,1996,45(2):511515.[6]Ljubomir Kojovic. Rogowski coils suit relay protection and measurement[J].IEEE Computer Application in Power,July1997:4752.(Executive editor WANG HaiJiang) From： Journal of Shanghai University (English Edition), 2002,6(1): 79~84