Design And Development Of Over-voltage Online Monitoring System Based On Transmission Characteristics Of Devices

In the modern power systems, over-voltage often occurs because of the lightning strike, failure, resonance, switching operation, etc. As soon as running across the over-voltage, the electrical equipments during operation are likely to generate breakdown, discharge, flashover, explosion accident and so on. These accidents cause not only economic loss of power companies but also serious effect on the security and stability of the power network. Therefore, monitoring the change of the over-voltage of the power system is of great importance to ensure the security and stability of the power network.However, there are limitations of the existing on-line over-voltage monitoring devices in the modern power systems. Considering this problem, this paper presents a new method for on-line over-voltage monitoring based on the transmission characteristics of the devices in the substation, which could conquer the above certain limitations. This method modeled the potential transformer (PT), secondary cables and voltage divider as several two-port networks in cascade. Building transmission-parameters model and adoption of specific numerical method, obtaining the PT primary voltage signal by the in versed calculation.The article completes the hardware design and the software programming of the system.The hardware includes the choice of the PT.secondary cable,production of the voltage divider,selection and setting of the data acqusition card;measuring the scattering parameters of the PT,secondary cable and divider, calculating the transmission parameters.building the transmission parameters of the PT secondary cable and the voltage divider cascade model based on frequency domain measurement data,simplifying calculation model by measuring the frequency domain data analysis. Software programming includs the system interface design, data collection, the functionality of the software to achieve seamless connectivity and mixed programming.Over-voltage monitoring system software,which is designed as a platform of LABVIEW and MATLAB mixed programming,can display over-voltage data collected on-site,calculate over-voltage waveform of the PT primary,further process the waveform.Combination of hardware and software can get the waveform data,process image and display waveform,which has a strong engineering applications,but also has important scientific significance.