Abstract: A ground fault overvoltage relay device is configured to: determine whether or not a first condition is satisfied, the first condition being that at least two of line voltages between respective two phases are less than or equal to a first threshold value; determine whether or not a second condition is satisfied, the second condition being that a ratio between a minimum value of the line voltages between the respective two phases and a minimum value of the respective phase voltages is less than or equal to a second threshold value; determine whether or not a third condition is satisfied, the third condition being that the zero-phase voltage is greater than a third threshold value; and lock a ground fault detection output when the first condition is satisfied, or when the second condition is satisfied and the third condition is not satisfied.

Abstract: A ground fault overvoltage relay device is configured to: determine whether or not a first condition is satisfied, the first condition being that at least two of line voltages between respective two phases are less than or equal to a first threshold value; determine whether or not a second condition is satisfied, the second condition being that a ratio between a minimum value of the line voltages between the respective two phases and a minimum value of the respective phase voltages is less than or equal to a second threshold value; determine whether or not a third condition is satisfied, the third condition being that the zero-phase voltage is greater than a third threshold value; and lock a ground fault detection output when the first condition is satisfied, or when the second condition is satisfied and the third condition is not satisfied.

Abstract: A digital signal input device has a first input terminal and a second input terminal, a charging circuit connected between the first input terminal and the second input terminal, and a digital signal detection unit that outputs a digital signal of a logical value corresponding to a level of a charging voltage to an internal circuit. A pulse control unit generates a pulse signal having a fixed period using designated pulse width and pulse period. A switching element is provided between the charging circuit and the first input terminal or the second input terminal, which controls a period of applying a DC voltage to the charging circuit using a pulse width of the pulse signal.

Abstract: A digital signal input device has a first input terminal and a second input terminal, a charging circuit connected between the first input terminal and the second input terminal, and a digital signal detection unit that outputs a digital signal of a logical value corresponding to a level of a charging voltage to an internal circuit. A pulse control unit generates a pulse signal having a fixed period using designated pulse width and pulse period. A switching element is provided between the charging circuit and the first input terminal or the second input terminal, which controls a period of applying a DC voltage to the charging circuit using a pulse width of the pulse signal.