High-precision fast measuring circuit and method for wide-range currents in power system

The invention discloses a high-precision fast measuring circuit and method for wide-range currents in a power system. The circuit comprises a current transformer, a signal processing circuit, an amplitude limiter, an A/D converter (analog to digital converter) and a CPU (central processing unit) which are connected in sequence. The signal processing unit comprises a pre-amplifier, a main amplifier and a self-adaptive amplifier which are connected in sequence. The pre-amplifier is connected with the current transformer. The self-adaptive amplifier is connected with the amplitude limiter. The node between the main amplifier and the self-adaptive amplifier is connected with three branches. Each branch is provided with an average value extracting circuit and a voltage comparator which are connected in sequence. Each average value extracting circuit is connected to the input end of the self-adaptive amplifier. Each voltage comparator is connected with a multi-way switch through a first level converter. Due to the