With Change Control And Data Acquisition System And Gprs Based Data Compression

It's very important and urgent to be solved of large quantity of measured data's communication and storage in power system with the gradually spread of transformer substation automatization and the key way to this problem is carrying out data compression. To this actuality in our country, this paper has discussed theoretically and made mass simulations on the related problems to the compression, remote transmission and decompression of measured data of power system.Firstly, the popular data compression algorithms are analyzed. Then the article briefly introduced the GPRS technology characteristic and the superiority, introduced the GPRS network architecture, but also has carried on the analysis to GPRS in the electric power communications network feasibility.For the recorded data of stable state, the article discussed two compression approaches in detail. The first one is a lossless algorithm called liner prediction differential and static Huffman joint encoding. The algorithm first removes the data correlative between the samples by replacing the sampling data by the differential value and then reduces the data redundancy by Huffman encoding. The second one is to use Fourier transformation to convert the source signal from time domain to frequency domain and to discard high frequency harmonious components upwards of 19, then to use static Huffman coding to encode the quantized character array which is composed of reserved direct current component and basic wave and each high frequency 's amplitudes and angles. For the recorded data of transient state, the algorithm called wavelet transformation and LZW joint encoding. Wavelet transformation has good multi-resolution ability both on the time domain and frequency domain, so it is very useful for recorded data compression. In order to get better compression effect, LZW algorithm is introduced to encode the quantized wavelet coefficients.For the recorded data with both stable state data and transient state data, a novel synthesis algorithm for complex electric signal, based on Fourier transformation and Wavelet transformation, is proposed to compress the power recorded data in this paper. It first classifies power quality disturbances into stable one and transient one by wavelet's multi-resolution analysis, and then compresses the stable and transient recorded signals by Fourier transformation and orthogonal wavelet transformation respectively. Then the LZW and Huffman algorithm is introduced to encode the quantized wavelet and Fourier coefficients respectively.Mass simulations and analysis under several circumstances have been done to show that the data compression approach based on Wavelet transformation and Wavelet transformation, are performed to verify the effectiveness of the novel synthesis algorithm. Lastly, the experiment of file transmission by GPRS has been done. The comparative analysis of transport effectiveness between the source file and the compressed source file is to verify that the data compression is indispensable.