Zhang Chengxue

A live-line measurement method to parameters of high voltage cable lines with mutual inductance based on GPS

The theoretical calculation method with formulae and the conventional measurement method of zero-sequence self-and mutual-impedance of high voltage cable lines are reviewed. Then the principles and mathematical models of zero-sequence parameter live-line measurement method of cable lines with mutual inductance based on GPS (Global Positioning System) technology are presented together with key techniques, hardware structure and software algorithm of the measurement system. Finally, field measurement results with the three different methods are given. Theoretical analysis and field measurement results prove that this new live-line method proposed in the paper is correct, effective and efficient.

The effects of flexible AC transmission systems device on protective relay

The paper introduces the basic structure and equivalent circuit model of unified power flow controller (UPFC) and then analyzes its effects on the transmission line distance relay in two cases. Different location of the UPFC, fault resistance, parameters of UPFC, the location of the fault and system operation conditions all affect the measured apparent impedance to some degree. The presence of UPFC will make the relay under-reach or over-reach. In order to eliminate the effects of a UPFC device on protective relay, two methods are given in this paper. One is to equip protective relay devices in which the UPFC device is equipped. In this way the UPFC device is always beyond the fault loop. The other is to use an artificial neural network to eliminate the effects of UPFC device.

Realization of high speed digital carrier communication module using COFDM

In this paper, realization of high speed carrier communication module using new coded orthogonal frequency division multiplexing (COFDM) is discussed. OFDM theory and its coding technology are simply introduced .The advantage of using COFDM modulating technology in power carrier wave communication is analyzed, and data transfer flow of the corresponding COFDM wave-carrier system is presented. The module design based on DSP is put forward, channel coding simulation and hardware composition and realization are also presented in this paper.

Harmonic real time estimation by artificial neural network based on network and GPS technology

A new harmonic real time identification approach by adaptive neural network based on GPS technology and distributed Ethernet network was proposed in this paper. The method uses an adaptive neural network to estimate the amplitudes and angles of the distorted current in power system. In this method, only half cycle harmonic current signal was used as the input of the neural network. In order to improve the accuracy of harmonic source identification, GPS (global positioning system) is used as the synchronized signal for the embedded measurement system based on digital signal processor (DSP). The samples selecting and training methods of artificial neural network are explained and the hardware structure of the embedded harmonic identification system is given. RTDS (real-time digital simulator) simulation results illustrate the effectiveness of the proposed approach

The hardware configuration and field experiment of GPS-based for online parameter tester for transmission lines with mutual inductance

A GPS-based power transmission line tester, in which the time tag of GPS is used as the synchronization signal, is developed practically to realize the online measurement of power system parameters. The principles of the new measurement scheme are reviewed in the first part of the paper. The hardware and numerical algorithms are then presented in details, followed by experimental results.