A protection and control system, comprising: a first merging unit which obtains an electric variable from a transformer installed in an electric power system, and digitally converts the obtained electric variable to output as first electric variable information to a first network; and a plurality of first protection and control devices, each of which obtains the first electric variable information from the first merging unit through the first network, judges whether or not a system fault occurs in a zone to be protected of the electric power system based on a predetermined relay characteristic, and outputs main trip information to the first network when that the system fault occurs is judged; characterized by: a second merging unit which obtains the electric variable from the transformer installed in the electric power system, and digitally converts the obtained electric variable to output as second electric variable information to a second network; and a second protection and control device (108-2, 108-3) which obtains the second electric variable information from the second merging unit through the second network, judges whether or not the system fault occurs in the zone to be protected of the electric power system based on a plurality of the relay characteristics which are predetermined as respective fault detection relays of the first protection and control devices, and outputs fault detection trip information to the first network when that the system fault occurs is judged; wherein the first merging unit has a trip command output unit which judges whether or not to open a circuit breaker installed in the electric power system, based on the main trip information and the fault detection trip information, and outputs a trip command when to open the circuit breaker is judged. a first merging unit which obtains an electric variable from a transformer installed in an electric power system, and digitally converts the obtained electric variable to output as first electric variable information to a first network; and a plurality of first protection and control devices, each of which obtains the first electric variable information from the first merging unit through the first network, judges whether or not a system fault occurs in a zone to be protected of the electric power system based on a predetermined relay characteristic, and outputs main trip information to the first network when that the system fault occurs is judged; characterized by: a second merging unit which obtains the electric variable from the transformer installed in the electric power system, and digitally converts the obtained electric variable to output as second electric variable information to a second network; and a second protection and control device (108-2, 108-3) which obtains the second electric variable information from the second merging unit through the second network, judges whether or not the system fault occurs in the zone to be protected of the electric power system based on a plurality of the relay characteristics which are predetermined as respective fault detection relays of the first protection and control devices, and outputs fault detection trip information to the first network when that the system fault occurs is judged; wherein the first merging unit has a trip command output unit which judges whether or not to open a circuit breaker installed in the electric power system, based on the main trip information and the fault detection trip information, and outputs a trip command when to open the circuit breaker is judged. a second merging unit which obtains the electric variable from the transformer installed in the electric power system, and digitally converts the obtained electric variable to output as second electric variable information to a second network; and a second protection and control device (108-2, 108-3) which obtains the second electric variable information from the second merging unit through the second network, judges whether or not the system fault occurs in the zone to be protected of the electric power system based on a plurality of the relay characteristics which are predetermined as respective fault detection relays of the first protection and control devices, and outputs fault detection trip information to the first network when that the system fault occurs is judged; wherein the first merging unit has a trip command output unit which judges whether or not to open a circuit breaker installed in the electric power system, based on the main trip information and the fault detection trip information, and outputs a trip command when to open the circuit breaker is judged.