1、PDF原文：http:/ 3060 字 附录 A 外文翻译 A.1 外文 原文 Measurements of the distorted no-load current of a 20/60kV 6MVA Yy0 power transformer Kim SgaardWojciech T.Claus Leth Bak AalborgUniversityWiechowskiAalborgUniversity Aalborg, DenmarkAalborgUniversityAalborg, Denmark soegaardieee.orgAal
2、borg, Denmarkclbiet.auc.dk wtwiet.auc.dk ABSTRACT This paper presents the results from measurements of the distorted no-load current of a 6MVA 20/60kV transformer. In the execution of the measurement, the supply setup during the measurements has been changed. The changes imply different connections
3、of the 0.4/20kV supplying transformer. The secondary winding of the supplying transformer are connected in D, wye and YN, and for each connection, the measurements are repeated. The measurement is performed with constructed current and voltage transducers with an amplitude accuracy better than 1%. I
4、t has been shown that the harmonic contents in the no-load current the 6MVA 20/60kV transformer Thrige is as predicted by 6. 1. INTRODUCTION Due to the lack of measurements of the distorted no-load current of large power transformers published in the literature, this paper is prepared. T
5、he main reason for the measurements is to validate a new power transformer model based on a procedure presented by 3. The Ph.D. student Wojciech Wiechowski implements the Transformer model in DIgSILENT Powerfactory. The origin of the Ph.D. project is that the Danish transmission company ELTRA has ex
6、perienced operational malfunctions of some of the measuring and protection equipment. The conclusion after a preliminary investigation was that the reason for that were harmonic voltages and currents that propagate in the transmission grid. To investigate and map the harmonic propagation, ELTRA has
7、offered this Ph.D. project. The Contribution of this Ph.D. project is to build a computer model of the entire transmission system in the area supplied by the Danish transmission company ELTRA so it will reflect the real system behaviour at harmonic frequencies, up to 1-2 kHz. Special focus shall be
8、paid on the nonlinearities present on the transmission level, which means HVDC links and transformer core nonlinearities. In the collaboration between AalborgUniversity and the Danish distribution company HEF Net, a 6 MVA 20/60 kV transformer 20/60 kV Thrige are at disposal for the author. The
9、 original setup for the transformer 20/60 kV Thrige includes voltage and current transformers intended to measure the fundamental frequency component of voltages and currents. These original voltage and current transformers do not measure with an acceptable accuracy in the frequency range dc up to 2
10、 kHz. To measure more accurately a measuring setup has been designed and constructed. The measuring setup consists of three current and voltage transducers and a data acquisition device. The current transducer is a LEM current clamp. The voltage transducer is made of two capacitors that form a capac
11、itive voltage divider. Originally, the 20/60 kV Thrige transformer is supplied from the 60 kV bus at the 60/20 kV station Aggersund in northern Jutland. However, to ensure that malfunction of the measuring setup does not interfere with the rest of the 60/20 kV station, this 20/60 kV transforme
12、r Thrige is supplied through the local 0.4 kV network in Aggersund. 0.4 kV supplying voltage is transformed to 20 kV through a 100 kVA transformer connected on the high voltage side in Y or YN or a 160 kVA transformer connected on the high voltage side in D. A schematic diagram of the supply setup f
13、or Thrige is shown on Figure 1, with the tree different connection on the high voltage side of the 0.4/20kV transformer. Figure 1. Schematic diagram of the supply setup for20/60kV transformer Thrige in Aggersund. 2. MEASUREMENT SETUP 2.1. CURRENT TRANSDUCER The
14、 current transducer is a LEM PR30 current probe. The current transducer transforms the measured current to a voltage with a precision that is present in Table 1 next to the demands from IEC 61000-4-75. Table 1. Precision for the current transducers and demands from IEC 61000-4-7.
15、 Accuracy current IEC61000-4-7 Transducer Amplitude 1 % 5 % Phase < 2 - Frequency range DC to 100 kHz DC to 2.5 kHz The precision for the current transducer is obtained from the relevant datasheet 4. The LEM current transducer is placed on adapted cardboard that guarantee centre position around the conductor. 2.2. VOLTAGE TRANSDUCER The voltage transducer is constructed of two capacitors connected in series, as illustrated on Figure 2.
