Abstract: An object of the present invention is to provide a network system or the like in which the construction cost of a network for a plurality of control systems is suppressed which is excellent in resistance to a network failure.

Abstract: An object of the present invention is to provide a network system or the like in which the construction cost of a network for a plurality of control systems is suppressed which is excellent in resistance to a network failure.

Abstract: Disclosed are a digital protection control system and a digital protection control apparatus, wherein the digital protection control apparatus can easily be made to have more terminals, even when the number of terminals of a power transmission line increases. The digital protection control system has, as terminal stations thereof, a reference station that is to become the reference point for the sampling time at which power grid current information is to be taken in, tail-end stations that take in power grid current information from the power grid system, and intermediate stations that are connected between the reference station and the tail-end stations via transmission paths. The intermediate station is provided with an uplink transmission unit that is connected to a transmission path at the reference station side thereof, and a plurality of downlink transmission units that are connected to transmission paths at the tail-end station side thereof.

Abstract: Disclosed are a digital protection control system and a digital protection control apparatus, wherein the digital protection control apparatus can easily be made to have more terminals, even when the number of terminals of a power transmission line increases. The digital protection control system has, as terminal stations thereof, a reference station that is to become the reference point for the sampling time at which power grid current information is to be taken in, tail-end stations that take in power grid current information from the power grid system, and intermediate stations that are connected between the reference station and the tail-end stations via transmission paths. The intermediate station is provided with an uplink transmission unit that is connected to a transmission path at the reference station side thereof, and a plurality of downlink transmission units that are connected to transmission paths at the tail-end station side thereof.

Abstract: A multi-terminal power line protective relay system is provided, which divides a power transmission line having four or more terminals into two or more power line sections composed of three adjacent terminals and portions of the power transmission line lying among the three adjacent terminals and one of the three adjacent terminals being shared by two adjacent power line sections, and includes protective relays at the respective terminals including a current-driven differential protective relay element for detecting a fault occurring in a power line section through current-differential calculation by using measured currents, inter-terminal communication channels linking two protective relays at two different terminals; and intra-terminal communication channels linking two protective relays at each shared terminal.

Abstract: A multi-terminal power line protective relay system is provided, which divides a power transmission line having four or more terminals into two or more power line sections composed of three adjacent terminals and portions of the power transmission line lying among the three adjacent terminals and one of the three adjacent terminals being shared by two adjacent power line sections, and includes protective relays at the respective terminals including a current-driven differential protective relay element for detecting a fault occurring in a power line section through current-differential calculation by using measured currents, inter-terminal communication channels linking two protective relays at two different terminals; and intra-terminal communication channels linking two protective relays at each shared terminal.