Protection Current Transformer For Simulation And The Anti-saturation Algorithm

The thesis focuses attention on the current transformer(TA) for protection. Whereas thinking about the problems existing in the choices and applications of TA,we have done some research about the theory and digital simulations on the base of our reading and anaysing of many pertinent meterials. In this thesis ,we mainly dress the following aspects:(1) Itemizing different types of TA ,including their characteristics.Giving out the method for calculating and selecting fundamental performance parameters, such as primary current, primary winding, secondary current, secondary load, time constant and so on.(2) Introducing new method, which improves and pertectes the conventional method, for establishing TA model and simulating the excitation curve by using matlab coding. As a result, we get much better effects, not only the limiting hysteresis loop, local hysteresis loop but also various saturation waves.(3) We analyze the impact to the relay protection by studying the following elements:line protection, bus protection, main transformer protection, shunt reactor protection,circuit breaker protection,etc.(4) Studying on the measures for resisting TA's saturation and getting some methods for detecting TA's saturation. Emphasis on the utility of current transformer saturation detection by using magnetic restraint principle. This method effectively resolves the problem that it's hard to get the initial remanence in the core when we are calculating the flux linkage by using the integral algorithm, and also the problem of mal-operation brought in by the remanence.