Ground fault overvoltage relay device

A ground fault overvoltage relay device, comprising:

• an input unit configured to receive inputs of respective phase voltages of a power system detected by a voltage transformer;
• a ground fault detection unit configured to detect a ground fault based on a zero-phase voltage calculated from the respective phase voltages;
• a first determination unit 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 calculated based on the respective phase voltages are less than or equal to a first threshold value;
• a second determination unit configured to 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;
• a third determination unit configured to determine whether or not a third condition is satisfied, the third condition being that a maximum value of the respective phase voltages is greater than a third threshold value;
• and
• a lock unit configured to lock a detection output by the ground fault detection unit, wherein the lock unit locks the detection output when the first condition is satisfied, and the lock unit locks the detection output when the second condition is satisfied and the third condition is not satisfied.

A ground fault overvoltage relay device, comprising:

• an input unit configured to receive inputs of respective phase voltages and a zero-phase voltage of a power system detected by a voltage transformer;
• a ground fault detection unit configured to detect a ground fault based on the zero-phase voltage;
• a first determination unit 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 calculated based on the respective phase voltages are less than or equal to a first threshold value;
• a second determination unit configured to 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;
• a third determination unit configured to 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
• a lock unit configured to lock a detection output by the ground fault detection unit, wherein the lock unit locks the detection output when the first condition is satisfied, and the lock unit locks the detection output when the second condition is satisfied and the third condition is not satisfied.

A ground fault overvoltage relay device, comprising:

• an input unit configured to receive inputs of respective phase voltages and a zero-phase voltage of a power system detected by a voltage transformer;
• a ground fault detection unit configured to detect a ground fault based on the zero-phase voltage;
• a first determination unit 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 calculated based on the respective phase voltages are less than or equal to a first threshold value;
• a second determination unit configured to 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;
• a third determination unit configured to determine whether or not a third condition is satisfied, the third condition being that a maximum value of the respective phase voltages is greater than a third threshold value;
• and
• a lock unit configured to lock a detection output by the ground fault detection unit, wherein the lock unit locks the detection output when the first condition is satisfied, and the lock unit locks the detection output when the second condition is satisfied and the third condition is not satisfied.