With the breakthrough of electrooptical technology research on sensor application, the promulgation of IEC 61850, the application of Ethernet communication technology and the development of intelligent breaker, digital substation has become the mainstream of substation automation technology development in future. This paper briefly discusses issues related to electric energy measurement in digital substation, including the differences between electric energy measurement in digital substation and conventional substation, the impact to energy measurement of electronic transformer's application. Meanwhile, aiming at the present issues, potential research fields of electric energy measurement in future digital substation is proposed as well.

Aiming at the achievement of virtual power and electric energy measurement in digital substation, considering the unreasonable harmonic energy measurement problem in present power systems, according to the principle that the harmonics are produced by the phase -locking and frequency multiplication of first-harmonic, a kind of harmonic power computation based on the phase difference correcting method is introduced. The method corrects the harmonic frequency after correcting the first-harmonic frequency. The effectiveness of the method in normal and frequency deviation condition is simulated in the software LabVIEW and the results of the simulation are analyzed. Meanwhile, the method is tested in the existing virtual instrument software and hardware platforms. Both the simulation and the test results certify the real-timing and high accuracy of the virtual power measurement method. At last, in order to indicate the real-timing of the method in the practical electric energy measurement application, comparison experiments with watt-hour meter are performed. The results show the method still has good real-timing and high accuracy in the practical electric energy measurement.

The performance of electronic current transformer could been deteriorated,even destroyed during some extreme circumstance,for example,overvoltage or over current.This paper introduces the protective problems of several parts for ECT,LPCT(low power current transformer),Rogowski coil,power supply system and signal processing circuits in high-voltage side,the corresponding protective methods and design criterions have been proposed.Errors on LPCT induced by leakage current are analyzed.The analysis results show that errors induced by protection components could be ignored through selecting appropriate parameters.Type test results show the ECT based on the proposed methods meets IEC 0.2 class requirements,and the validity of the measures have been proved.

Measuring accuracy is a key parameter for electronic current transformer(ECT), but the temperature variation of the surrounding environment may influence its measuring accuracy. Temperature-dependent accuracy is one characteristic for ECT compared to traditional current transformer and it is a key parameter to be analyzed during the development of ECT. According to the function of an ECT based on low power current transformer (LPCT), several sub-systems are decomposed by this paper. Temperature-dependent accuracy of these sub-systems is analyzed and the expressions on temperature dependence of LPCT and the amplifiers in the electronic circuitry in high voltage side are proposed. One type of electronic current transformer was developed and passed the type test in the national authoritative department of China. The test results show that the transformer developed by this paper fulfils IEC 0.2 class accuracy requirements and achieves accuracy within ±0.1% in ratio error and ±4′in phase error at ?25～50℃. The validity of the analysis is confirmed by the results.

The development of an optical instrument transducer to measure rotor's voltage and current in power generator is described in the paper. The system is based on A/D conversion and optical fiber transmission principle. The voltage/current signal from SCR bridge of an power generator is conditioned to ADC and than the digital signal from ADC is transmitted to local module through optical fiber. The uncertainty of the OIT is estimated to be less than 0.2% in ratio and the delay time of the step response is less than 7 ms.

The system error characteristics are analyzed to improve the measurement accuracy of electronic instrument transformers.The noise characteristics of the electronic instrument transformers are related to the error characteristics of front-amplifiers,A/D converters,and signal processing units on the low-voltage side.The analysis identifies the key factors influencing the system measurement accuracy.Criteria are then developed for component selection and system design of the transformers with a 220 kV electronic current transformer developed and tested.The results show that the current transformer meets the IEC 0.2 class accuracy requirements,has a ratio the range of error of less than ±0.1% and a phase error of less than ±2′ at the range of-30℃ to +70℃.

For measuring current in three-phase plate-form busbars, this paper proposed an indirect method that used planar Rogowski coil as the current sensing part. Based on the electromagnetic induction law, Biot-Savart law and the numerical integration arithmetic, the vector potential of the busbar was calculated and the electromotive force of the planar coil for the single phase and three-phase busbar current was deduced. The relative error that was caused by vertical displacement, flat displacement and rotated displacement of coil was measured and calculated when the coil was used for the measurement of plate-form busbar current. The results of the theoretical calculation about the coil have good accordance with the experiments. More than two years of field testing shows that the current transducers based on the planar Rogowski coil proposed by this paper meets the requirement of practicality.

For measuring current in three phase plate form busbars, this paper proposed an indirect method that used planar Rogowski coil as the current sensing part. Based on the electromagnetic induction law, Biot-Savart law and the numerical integration arithmetic, the vector potential of the busbar was calculated and the Electromotive force of the planar coil for the single phase and three phase busbar current was deduced. The relative error that was caused by vertical displacement, flat displacement and rotated displacement of coil is measured and calculated when the coil is used for the measurement of plate form busbar current. The results of the theoretical calculation about the coil have good accordance with the experiments. More than two years of field testing shows that the current transducers based on the planar Rogowski coil proposed by this paper meets the practicality.

Reliability analysis is the key procedure during the development of electronic current transformer (ECT). On the basis of the contrastive analysis on reliability of electromagnetic current transformers, by means of failure modes and effects analysis (FMEA) as well as fault tree analysis (FTA) the reliability of a kind of electronic current transformer is researched, and perfect worksheets of both FMEA and FTA are established. All of minimum cut sets of fault trees are found out and the qualitative analysis on the reliability of the ECT is conducted. The effectiveness of the presented reliability analysis method is verified by the results of the analysis on two practical examples during the development and test process of the ECT.

本文介绍了清华大学非电专业"计算机硬件技术基础"课程在能力导向理念下的教学目标、教学内容、教学方法、成绩评定和教学效果,着重描述了"以学生为本、培养学生综合能力"的教学思想在各教学环节中的具体实施。

一、亚伯塔大学简介 亚伯塔大学成立于1908年,是加拿大五所最大的以科研为主的综合性大学之一,在加拿大<Maclean's>杂志2003年对加拿大该类大学的综合声誉排名、最佳教学质量排名、最富创新精神排名中均名列前6名.

在清华985教学重点建设的"计算机基础教学与实验基地建设"项目中,清华大学计算机系先后选派了从事计算机基础教学的六位青年骨干教师到剑桥大学、曼彻斯特大学、斯坦福大学、墨尔本大学、亚伯塔大学等名校进行了为期半年的访问进修学习。那么,在培养计划、课程设置、课程管理、实验教学、实验室管理等方面,他们都有什么收获呢?且看本文的国外名校计算机基础教学状况与目前国内的计算机基础教学情况的对比介绍。

介绍了一种应用于高压测量系统中电源方案,可成功地解决高压侧电子测量设备的电源问题与对地绝缘之间的矛盾.该方案已应用于10 kV光电式电流互感器中,取得了良好的运行效果.