A control system comprising: an analog/digital conversion unit which is configured to introduce an analog electric quantity provided from an electric power system and to convert the analog electric quantity into a digital quantity; and a digital operation processing unit which is configured to perform protection control operation regarding a state of the electric power system using the digital quantity, wherein the analog/digital conversion unit includes a ΔΣ modulating device which is configured to sample the analog electric quantity provided by the electric power system with a predetermined modulation frequency and to output a bit stream changing over time of single bit obtained by performing ΔΣ modulation, characterized in that the digital operation processing unit includes a plurality of digital filters each of which is configured to input the bit stream from the ΔΣ modulating device and of which frequency characteristics differ according to a type of protection control operation, and a plurality of operation processing elements each of which is connected to a respective digital filter and which are configured to perform different kinds of protection control operation processing regarding protection control, based on the bit stream provided by the respective digital filter, and each digital filter of the digital operation processing unit is configured to output data of different sampling cycles for the protection control operation processing of the operation processing elements, and includes processing for performing moving average in a same period as an ultimate output data cycle of the digital filter or a period longer than the ultimate output data cycle of the digital filter; wherein the moving average processing of the digital filter includes first stage moving average processing and decimation processing, and subsequent second stage moving average processing and decimation processing which is processing into an ultimate sampling cycle, and the first stage moving average processing includes a combination of moving averages of two different types of tap lengths, and the first stage moving average processing includes processing for performing moving average in a same period as the ultimate sampling cycle or a period longer than the ultimate sampling cycle. an analog/digital conversion unit which is configured to introduce an analog electric quantity provided from an electric power system and to convert the analog electric quantity into a digital quantity; and a digital operation processing unit which is configured to perform protection control operation regarding a state of the electric power system using the digital quantity, wherein the analog/digital conversion unit includes a ΔΣ modulating device which is configured to sample the analog electric quantity provided by the electric power system with a predetermined modulation frequency and to output a bit stream changing over time of single bit obtained by performing ΔΣ modulation, characterized in that the digital operation processing unit includes a plurality of digital filters each of which is configured to input the bit stream from the ΔΣ modulating device and of which frequency characteristics differ according to a type of protection control operation, and a plurality of operation processing elements each of which is connected to a respective digital filter and which are configured to perform different kinds of protection control operation processing regarding protection control, based on the bit stream provided by the respective digital filter, and each digital filter of the digital operation processing unit is configured to output data of different sampling cycles for the protection control operation processing of the operation processing elements, and includes processing for performing moving average in a same period as an ultimate output data cycle of the digital filter or a period longer than the ultimate output data cycle of the digital filter; wherein the moving average processing of the digital filter includes first stage moving average processing and decimation processing, and subsequent second stage moving average processing and decimation processing which is processing into an ultimate sampling cycle, and the first stage moving average processing includes a combination of moving averages of two different types of tap lengths, and the first stage moving average processing includes processing for performing moving average in a same period as the ultimate sampling cycle or a period longer than the ultimate sampling cycle.