Methods and systems for detecting a falling power line in a power transmission or distribution system are described. Electrical measurements at various points in the power distribution system are used to detect changes in a power line indicating that the conductor has broken or become disconnected. Upon detection, control mechanisms are used to deenergize the conductor while the conductor is falling and/or before it contacts the ground.

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.

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.

Provided is disclosure for embodiments providing surge protection, where the electric load can be isolated from its power supply upon detection of a wiring fault, undervoltage, and/or overvoltage.

A method and an apparatus for detecting a vector shift in an AC power system, the apparatus comprising frequency measuring means adapted to determine a frequency of the AC power system, derivation means adapted to determine a time derivative of the frequency, filtering means adapted to filter the time derivative of the frequency, and detection means adapted to calculate time derivatives for the filtered time derivatives of the frequency over a time period having the length of the fundamental period of the AC power system, to determine a number of positive and negative time derivatives among the calculated time derivatives, and to detect a vector shift in the AC power system in response to an absolute value of a difference between the determined number of positive time derivatives and negative time derivatives exceeding a predetermined threshold value.

A method and an apparatus for detecting a vector shift in an AC power system, the apparatus comprising frequency measuring means adapted to determine a frequency of the AC power system, derivation means adapted to determine a time derivative of the frequency, filtering means adapted to filter the time derivative of the frequency, and detection means adapted to calculate time derivatives for the filtered time derivatives of the frequency over a time period having the length of the fundamental period of the AC power system, to determine a number of positive and negative time derivatives among the calculated time derivatives, and to detect a vector shift in the AC power system in response to an absolute value of a difference between the determined number of positive time derivatives and negative time derivatives exceeding a predetermined threshold value.

A safety tripping device for a frame-type ACB drawer seat, which includes a special gear, a first lever, a tension spring, a second lever, and a tripping shaft. The special gear includes the first rotation shaft and the first irregular convex flange feature. The irregular convex flange is lapped with a bending edge of one end of the first lever. The other end of the first lever is connected to the tension spring. An arc-shaped notch is provided at one end of the first lever which corresponds to the connecting spring. An arc-shaped protrusion matching the arc-shaped notch is provided at one end of the second lever. The arc-shaped protrusion engages with or separates from the arc-shaped notch to achieve the tripping operation. The frame-type ACB drawer seat according to the present invention is suitable for large-scale production applications.

A safety tripping device for a frame-type ACB drawer seat, which includes a special gear, a first lever, a tension spring, a second lever, and a tripping shaft. The special gear includes the first rotation shaft and the first irregular convex flange feature. The irregular convex flange is lapped with a bending edge of one end of the first lever. The other end of the first lever is connected to the tension spring. An arc-shaped notch is provided at one end of the first lever which corresponds to the connecting spring. An arc-shaped protrusion matching the arc-shaped notch is provided at one end of the second lever. The arc-shaped protrusion engages with or separates from the arc-shaped notch to achieve the tripping operation. The frame-type ACB drawer seat according to the present invention is suitable for large-scale production applications.

In order to heighten the level of electrical safety in residential, commercial and industrial networks, stay alert electronic control equipment are needed to detect and report the more common failures in the function of the electric circuitry: high and low line voltage, inversion of the phase sequence in three-phase networks, abnormal current flow between neutral and the ground conductor, and unplanned neutral interruption. When such failures suddenly come about, its effects can provoke harsh damages to users.

The integration in a device of the protection action against different failures such as neutral conductor interruption, a very dangerous and unpredictable failure, high and low voltage failures, phase sequence mistakes, and grounding currents in three phase systems, based on microcontrollers technology and the application of a neutral conductor interruption sensor in three phase systems and in any kind two phase systems improves the electrical safety in any electrical system.