A method generates a classification signal classifying an electrical impedance. The time characteristic of the impedance is measured resulting in impedance values. Impedance change vectors whose direction describes the movement of the impedance in the complex impedance plane and whose length describes the amount of the respective impedance change are formed with temporally successive impedance values. A check is carried out to determine whether the impedance shows a directional, continuous impedance movement. In the event of a subsequently detected change of direction of the impedance movement, the reaching of a reversal point is inferred and the rotation of the impedance change vectors is monitored with the result of a formation of an angle of rotation measured value. A classification signal indicating a fault is generated if the impedance change vectors have rotated in the area of the reversal point through a predefined maximum angle of rotation.

An arc suppression pre-charge circuit includes a source for providing energy to a load and a main contactor selectively closed to provide energy from the source to the load, wherein the main contactor provides an alternate current path from the source to the load and bypasses a pre-charge branch of the circuit when the main contactor is closed. The pre-charge branch includes a voltage-controlled resistor and a control circuit configured to control a resistance of the voltage-controlled resistor.

A three-stage surge protection device protects against complex, time-variant voltage transients, including those resulting from a high-altitude nuclear electromagnetic pulse or a solar coronal mass ejection. The device relies on interaction between a snubbing low-pass filter, a transient voltage suppressor, and an electronic crowbar circuit. The low-pass filter significantly lowers the let-through voltage of the device for short-duration pulses, and helps to spread the energy to more effectively utilize the transient voltage suppressor. The transient voltage suppressor limits the let-through voltage to a clamping level and provides indication to the crowbar circuit when it is no longer able to do so. Once the clamping level is no longer able to be maintained, the crowbar circuit draws enough current to trip an upstream protective device, such as a breaker or fuse.

A three-stage surge protection device protects against complex, time-variant voltage transients, including those resulting from a high-altitude nuclear electromagnetic pulse or a solar coronal mass ejection. The device relies on interaction between a snubbing low-pass filter, a transient voltage suppressor, and an electronic crowbar circuit. The low-pass filter significantly lowers the let-through voltage of the device for short-duration pulses, and helps to spread the energy to more effectively utilize the transient voltage suppressor. The transient voltage suppressor limits the let-through voltage to a clamping level and provides indication to the crowbar circuit when it is no longer able to do so. Once the clamping level is no longer able to be maintained, the crowbar circuit draws enough current to trip an upstream protective device, such as a breaker or fuse.

An overcurrent and/or short-circuit detector includes: at least one current sensor for picking up a current signal which has a predeterminable time resolution in at least one electrical current path; and at least one evaluation unit. The at least one evaluation unit: determines a first point in time of a predeterminable steep increase in the current signal, forms a temporal integral of current values of the current signal from the first point in time to a second point in time, compares a pair of values, including a relevant value of the integral and the relevant value of the current signal, with at least one predeterminable limiting condition at predeterminable temporal intervals substantially continuously, and emits an overcurrent and/or short-circuit signal to an outlet of the overcurrent and/or short-circuit detector if the pair of values exceeds a limiting condition.

An overcurrent and/or short-circuit detector includes: at least one current sensor for picking up a current signal which has a predeterminable time resolution in at least one electrical current path; and at least one evaluation unit. The at least one evaluation unit: determines a first point in time of a predeterminable steep increase in the current signal, forms a temporal integral of current values of the current signal from the first point in time to a second point in time, compares a pair of values, including a relevant value of the integral and the relevant value of the current signal, with at least one predeterminable limiting condition at predeterminable temporal intervals substantially continuously, and emits an overcurrent and/or short-circuit signal to an outlet of the overcurrent and/or short-circuit detector if the pair of values exceeds a limiting condition.

The present apparatus, system and method solves the problems of the prior art by enabling substantial dissipation of an electrical energy surge coming from communications antenna which has been struck by lightning. The apparatus is for mounting to an exterior of a building at or near communications antenna also located at the exterior of the building. The apparatus is connected with incoming coaxial cables extending from exterior mounted antenna and with outgoing coaxial cables which extend from the apparatus to communications equipment housed within a communications center. The lighting strike surge travels from antenna, along the incoming coaxial cable and is redirected within the apparatus by polyphasers which trip at capacity to redirect the surge to three separate grounding bars and prevent the surge from continuing along outgoing coaxial cables leading to communications equipment thus safely dissipating surge and shielding communications equipment.

A time-current coordination (TCC) curve for a programmable low-set instantaneous overcurrent (IOC) relay for at least one station breaker in an electrical distribution feeder with a fuse-saving scheme and a method of coordinating at least one recloser with the station breaker in the said feeder, for the reduction of frequency of power interruptions encountered by at least one load on the feeder and wherein the method includes the steps of: (a) feasible selection of a range for a time delay of a station breaker's programmable low-set IOC relay; (b) choosing a time delay based on a fuse-saving relation; and optionally (c) locating the recloser on the feeder.

A time-current coordination (TCC) curve for a programmable low-set instantaneous overcurrent (IOC) relay for at least one station breaker in an electrical distribution feeder with a fuse-saving scheme and a method of coordinating at least one recloser with the station breaker in the said feeder, for the reduction of frequency of power interruptions encountered by at least one load on the feeder and wherein the method includes the steps of: (a) feasible selection of a range for a time delay of a station breaker's programmable low-set IOC relay; (b) choosing a time delay based on a fuse-saving relation; and optionally (c) locating the recloser on the feeder.

Systems and method for detecting potentially harmful harmonic and direct current signals at a transformer are disclosed. One system includes a protection circuit electrically connected to a transformer neutral, the transformer electrically connected to a power grid, the protection circuit including a DC blocking component positioned between the transformer neutral and ground and one or more switches selectively actuated to form a path between the transformer neutral and ground in the event of unwanted DC current at the transformer neutral. The system also includes a control circuit electrically connected to the protection circuit and positioned to selectively actuate the switches based on observed conditions within the protection circuit. The system further includes a plurality of test connections disposed within the protection circuit and useable to test electrical properties of the protection circuit.