A sensor for monitoring loss of voltage on a monitored conductor includes first and second capacitors, each of which is charged by a rectifier circuit which derives operating power from the monitored conductor. Upon loss of voltage on the conductor, a discharge circuit discharges the first capacitor, while allowing the second capacitor to remain charged. When the voltage difference between the two capacitors exceeds a predetermined threshold level, an SCR discharge circuit discharges the second capacitor to provide an output signal.

A fault indicator for indicating the occurrence of a fault current in an alternating current conductor includes a pair of parallel-spaced reed switches in magnetic communication with the conductor. The reed siwtches are electrically connected in parallel by a magnetically conductive bridging element at one end of the pair and by a non-magnetically conductive bridging element at the other end of the pair. A permanent magnet bridging the non-magnetic bridge establishes a magnetic bias circuit which extends serially through the switches to increase the sensitivity of each switch to a fault current during a respective half-cycle of the alternating current cycle.

A reset coordinated fault indicator for indicating the occurrence of a fault current in a monitored conductor includes an electrically actuated indicator flag. A trip circuit within the fault indicator impulses the indicator flag from a normal reset-indicating state to a fault-indicating state following the occurrence of a fault current in the conductor. A reset circuit periodically impulses the indicator flag to the reset-indicating state upon restoration of power to the conductor. To preclude simultaneous actuation of the trip and reset circuits and consequent failure of the indicator flag to register a fault, the trip circuit, upon the occurrence of a fault, first actuates the reset circuit to render the reset circuit inoperative, and then actuates the indicator flag to provide a fault indication.

A circuit condition monitoring system for an electrical power distribution system includes a system connector component having an integrally molded test point socket within which a circuit module is received to provide fault current or voltage loss monitoring of a system conductor within the connector. The test point socket provides capacitive coupling to the monitored conductor without the use of a metallic test point, and a ground return to the electrically conductive outer sheath of the connector. An electrically conductive end cap may be provided to cover the projecting end of the module when the module is installed in the socket. Adapters installed on the other end of the module enable the module to be installed on prior metallic contact-type test points.

A fault indicator for monitoring an electrical conductor has a housing, an indicator flag or a light emitting diode (LED) that becomes visible from the exterior of the fault indicator upon the occurrence of a fault, and electronic circuitry for sensing a fault, for actuating the indicator flag or LED to a fault indicating condition and for resetting the indicator flag or LED to a non-fault indicating condition a predetermined time after the fault has occurred. An overload indicator provides an overload indication, such as a fast flash rate, for a predetermined time when an overload threshold is exceeded, and provides a different overload indication, such as a slow flash rate, for a predetermined time when the line current in the monitored conductor falls below the threshold.