Directional comparison distance relay system

A directional comparison distance relay system configured to control a circuit breaker installed in a parallel three-phase AC electric power transmission system, the relay system comprising:

• a fault detection unit including a directional distance relay element configured to decide whether a fault is in forward or reverse directions relative to a location of a set of transformers which detect current and voltage in the power transmission system;
• a short-circuit distance relay element configured to decide whether a fault is within a protection zone by distance calculation based on the current and voltage;
• an under-voltage relay element configured to detect under-voltage based on the voltage;
• a transmission unit configured to send signals to and receiving signals from a neighboring relay system at an far end of the protection zone;
• an evolving fault detecting unit configured to decide an evolving fault when forward earth fault directional relays in at least two phases and a forward directional relay only in a single phase are in operation;
• and
• a block unit configured to block trip of a circuit breaker at a near end due to the short-circuit distance relay, and configured to block permissive trip signal to a circuit breaker at the far end, based on an operation of the evolving fault detecting unit.

A directional comparison distance relay system configured to cancel a circuit breaker installed in a parallel three-phase AC electric power transmission system, the relay system comprising:

• a fault detection unit including a directional distance relay element configured to decide whether a fault is in forward or reverse directions relative to a location of a set of transformers which detect current and voltage in the power transmission system;
• a short-circuit distance relay element configured to decide whether a fault is within a protection zone by distance calculation based on the current and voltage;
• an under-voltage relay element configured to detect under-voltage based on the voltage;
• a transmission unit configured to send signals to and receiving signals from a neighboring relay system at an far end of the protection zone;
• an evolving fault detecting unit configured to decide an evolving fault when under-voltage relays in at least two phases and a reverse directional relay are in operation;
• and
• a block unit configured to block trip of a circuit breaker at a near end due to the short-circuit distance relay, and configured to block permissive trip signal to a circuit breaker at the far end, based on an operation of the evolving fault detecting unit.

A directional comparison distance relay system configured to cancel a circuit breaker installed in a parallel three-phase AC electric power transmission system, the relay system comprising:

• a fault detection unit including a directional distance relay element configured to decide whether a fault is in forward or reverse directions relative to a location of a set of transformers which detect current and voltage in the power transmission system;
• a short-circuit distance relay element configured to decide whether a fault is within a protection zone by distance calculation based on the current and voltage;
• an under-voltage relay element configured to detect under-voltage based on the voltage;
• a transmission unit configured to send signals to and receiving signals from a neighboring relay system at an far end of the protection zone;
• an evolving fault detecting unit configured to decide an evolving fault when a trip signal is output only in a single phase and a reverse directional relay are in operation;
• and
• a block unit configured to block trip of a circuit breaker at a near end due to the short-circuit distance relay, and configured to block permissive trip signal to a circuit breaker at the far end, based on an operation of the evolving fault detecting unit.

A directional comparison distance relay system configured to control circuit breakers installed in a three-phase AC electric power transmission system, the relay system comprising:

• a fault detection unit including a directional distance relay element configured to decide whether a fault is in forward or reverse directions relative to a location of a set of transformers which detect current and voltage in the power transmission system;
• a short-circuit distance relay element configured to decide whether a fault is within a protection zone by distance calculation based on the current and voltage;
• and
• a delay unit configured to delay a trip command to the circuit breakers based on an operation signal from a Zone 1 element of a distance relay if the operation signal is sent when at least one of the circuit breakers is turned off.