Abstract: An electric power system relay includes a simulator that substitutes test values of current and voltage for sensed values for use by relay logic to perform specified relay functions, but without loss of the relay protection functions. The sensed values of current at least are monitored even while the test values are being used by the relay logic. If the monitored sensed values exceed a threshold value, a data switch operates to return to use of the sensed current and voltage values by the relay logic. In addition, the sensed values of current and voltage replace the test values, if a time interval longer than that required to perform the specified relay functions using the test values has expired.

Abstract: A circuit breaker includes a line terminal adapted to receive a line voltage having a nominal voltage value and an excessive voltage value, a load terminal, one or more neutral terminals, and separable contacts electrically connected between the line and load terminals. An operating mechanism opens and closes the separable contacts. A trip circuit cooperates with the operating mechanism to trip open the separable contacts. The trip circuit includes a solenoid having a trip coil with a threshold voltage for energization, a circuit adapted to detect an arc fault or ground fault trip condition and to responsively energize the trip coil with the line voltage, and a MOV adapted to detect an excessive voltage condition associated with the load and neutral terminals and to responsively energize the trip coil with at least the threshold voltage.

Abstract: An electric power system relay includes a simulator that substitutes test values of current and voltage for sensed values for use by relay logic to perform specified relay functions, but without loss of the relay protection functions. The sensed values of current at least are monitored even while the test values are being used by the relay logic. If the monitored sensed values exceed a threshold value, a data switch operates to return to use of the sensed current and voltage values by the relay logic. In addition, the sensed values of current and voltage replace the test values, if a time interval longer than that required to perform the specified relay functions using the test values has expired.

Abstract: A tester for verifying the integrity of insulation in a branch circuit of a power distribution system. Two test circuits are included; the first providing an insulation test; and a second, a shared/grounded neutral test. In the insulation test, a 500-volt ac output limited to 5 milliamps is selectively applied to the pairs of wires of the branch circuit. If an output current of greater than 3 milliamps is recorded, an insulation failure is noted and the operator proceeds to the second test which applies a pulsed 3 volt, 1 ampere current-limited voltage across the suspected leads. One of the suspected leads is monitored with a portable ammeter to detect any pulse current.

Abstract: A GFCI/AFCI circuit breaker includes a housing, separable contacts, and an operating mechanism for opening and closing the separable contacts. A first trip mechanism includes a GFCI/AFCI trip circuit having a resistor. The resistor is energized in response to a trip condition. The first trip mechanism cooperates with the operating mechanism to trip open the separable contacts in response to the trip condition. The resistor has a body which burns open in response to a failure of the separable contacts to trip open. A second trip mechanism engages the body of the resistor and cooperates with the operating mechanism to trip open the separable contacts in response to the body of the resistor burning open.

Abstract: A circuit breaker includes a line terminal adapted to receive a line voltage having a nominal voltage value and an excessive voltage value, a load terminal, one or more neutral terminals, and separable contacts electrically connected between the line and load terminals. An operating mechanism opens and closes the separable contacts. A trip circuit cooperates with the operating mechanism to trip open the separable contacts. The trip circuit includes a solenoid having a trip coil with a threshold voltage for energization, a circuit adapted to detect an arc fault or ground fault trip condition and to responsively energize the trip coil with the line voltage, and a MOV adapted to detect an excessive voltage condition associated with the load and neutral terminals and to responsively energize the trip coil with at least the threshold voltage.

Abstract: An electronic protective relay emulates an electromechanical protective relay so that operation of the two types of relays can be coordinated in providing protection in an electric power distribution system. The electronic protective relay incorporates a digital processor which increments a variable delay tally as an inverse current function and a fixed delay tally by a corresponding proportionate amount. During each running of the routine, only the smaller of the two tallies is increased so that they are forced to track one another. When both tallies reach a trip value, a trip signal is generated. The processor also applied a reset function when the measured current is below a pickup value. In accordance with the preferred reset feature, the variable delay tally is reduced using an inverse current function and the fixed delay is reduced by the same amount.

Abstract: A security system includes cameras disposed for activation by components of the system to record images of activity detected by the components. The system responds to a keypad and/or communications from a public switched telephone network to present the images for viewing. A system according to the invention supports visual verification of false alarms, tracking of arrivals and departures and recording those who arm and disarm the system. Visual verification also can be used in connection with remote notifications or authorizations of entry to the secured area.

Abstract: A multiwire branch circuit including two line conductors and a grounded, common neutral conductor is protected by a two pole circuit breaker connected to independently interrupt overcurrent conditions in the two ungrounded line conductors. Three separate protection circuits provide arc fault protection for each of the ungrounded line conductors and ground fault protection for all three conductors. The arc fault detectors use the bimetal of the thermal-magnetic trip device for the associated line conductor for current detection, and therefore, are individually referenced to the associated line voltage. Hence, the outputs of the arc fault detectors are electrically isolated from each other and from the output of the ground fault detector, but operate a common trip circuit to simultaneously open both poles of the two pole circuit breaker. The arc fault detectors have separate isolated power supplies.

Abstract: An arc fault detector of the type which generates a trip signal when a time attenuated accumulation of pulses produced each time an arc is struck reaches a selected value, includes a pulse conditioner which discriminates against false trips induced by phenomena such as tungsten bulb burn out and turn on of a cold tungsten bulb controlled by a dimmer. The pulse conditioner includes a zener diode which limits the amplitude of the pulses applied to the integrator, and stretches all of the pulses to reduce the variation in pulse duration. The latter can be accomplished by a peak detector which stretches pulses which reach the zener limit to a duration of at least about a half cycle.

Abstract: A multiwire branch circuit including two line conductors and a grounded, common neutral conductor is protected by a two pole circuit breaker connected to interrupt current flow in the two ungrounded line conductors. Three separate protection circuits provide arc fault protection for each of the ungrounded line conductors and ground fault protection for all three conductors. The arc fault detectors use the bimetal of the thermal-magnetic trip device for the associated line conductor, and therefore, are individually referenced to the associated line voltage. Hence, the outputs of the arc fault detectors are electrically isolated from each other and from the output of the ground fault detector, but operate a common trip circuit to open the two pole circuit breaker. The arc fault detectors have separate isolated power supplies. The ground fault detector is powered by a supply which is energized if either of the ungrounded line conductors is energized.

Abstract: The stray inductance created by the loop formed by voltage sensing conductors connected to opposite ends of the bimetal in a miniature circuit breaker for determining load current is reduced by joining a voltage sense bar to the free end of the bimetal. The voltage sense bar extends beside the bimetal toward the fixed end of the bimetal where an insulated wire connected to the free end of the sense bar forms a twisted pair with an insulated wire secured to the fixed end of the bimetal.

Abstract: Method and apparatus for pulling a vehicle free from mud, etc. using a vehicle drive wheel as a windless or winch and employing an elongated flexible strap, a gripper plate mounted on a leading end of the strap and an anchor plate mounted on a trailing end of the strap. The gripper plate is inserted between the tire and its support surface with upstanding teeth of the gripper plate engaging the tire. The drive wheel is then rotated with the vehicle engine to draw the gripper plate around the tire and wrap the trailing strap around the tire. The gripper plate is then secured to the overlapping strap, the anchor plate is anchored at a remote point aligned with the drive wheel and the vehicle is driven towards the anchor point using the strap to pull the vehicle free.

Abstract: An insertion machine system provides for the rapid determination of a value of postage required for a mailpiece by a table search technique which searches for and locates the value of postage in a predetermined table of postage values, the search being guided by the information provided by a predetermined data key.