Research On Relay Protection Cause By Over-voltage In Rogowski Coil Current Transformer

Electromagnetic current transformer has played a huge role in the power system development, but the presence of hysteresis and magnetic saturation and other defects that it can not meet the development trend of digital substation. Electronic current transformer, which has a simple structure, high sensitivity, wide measurement, can effectively overcome the lack of electromagnetic current transformer and meet the development needs of the digital advantages. The Rogowski coil electronic current transformers, which has good frequency response, measurement accuracy, measurement range, simple structure, excellent performance and low cost, is considered one of the best electronic current transformer. Many research institutions manufacturers, and universities had spend a lot of time studying it.Although there are many Rogowski coil current transformer be widely used, its stability and accuracy of measurement affected by various factors. There are already many universities, research institutions, enterprises do lots in-depth research and analysis on electromagnetic interference, temperature, relative placement of the bus, among other factors, established a theoretical model and proposed solutions. However, in practice there are still some new interfering factors, this paper, a new principle of analysis of the interference factors, and gives the appropriate solution. The new interference is:When the power system there have been struck by lightning strike or over-voltage, The induced electromotive force of Rogowski current transformer is interfered and disturbance, due to coupling capactio, causing the electric current measured value rised and causing protective relaying tripping.This paper describes the one-dimensional wavelet analysis of discrete Mallat algorithm, and analyze reason of the boundary effect of Mallat algorithm This paper will use the wavelet transform method to analysis the measure increases-current cause by lightning strike or over-voltage, and identify the current increases cause by the failure resulting. After verified by experiment, the wavelet transform method is effective.