A ground fault detector for detecting both balanced and unbalanced faults, eg. leakages to ground or other faults in a floating direct current system, comprises, first and second resistances connectible respectively to the positive and negative buses of the system, a two-way switching device operable to connect to the first and to the second resistances alternately, a fault condition being detected by voltage level detecting means connected between the switching device and ground, and a method o...

Methods and apparatus are provided for attenuating through-fault pressure disturbances in fault relays for a liquid-filled transformer. The method comprises the interposition of a mechanical filter between the transformer and the relay for attenuating through fault pressure variations while passing internal pressure faults. The filter consists of a pressure attenuation passage having an optimum length to diameter ratio for attenuating higher frequency pressure oscillations in excess of 50 Hz.

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 whic...

Methods and apparatus are provided for attenuating through-fault pressure disturbances in fault relays for a liquid-filled transformer. The method comprises the interposition of a mechanical filter between the transformer and the relay for attenuating through fault pressure variations while passing internal pressure faults. The filter consists of a pressure attenuation passage having an optimum length to diameter ratio for attenuating higher frequency pressure oscillations in excess of 50 Hz.

A combined ground fault and arc fault circuit interrupter includes a differential current transformer, a hot electrical line and a neutral electrical line passing through the current transformer and forming the primary thereof, an asymmetrical current transformer having a core through which the hot and common electrical leads pass, and a secondary wound on the core for producing a signal more strongly responsive to the current in the common line than in the hot line. An arc fault detector is con...

A ground fault detector having an indicator which indicates the presence of a ground or similar fault in an electrical line to be protected where the fault current is not of sufficient magnitude to cause the ground fault indicator to trip a circuit breaker to thereby interrupt the circuit in which the ground fault current is flowing. The indicating circuit provides a recognizable warning that a ground fault has begun or is in progress so that appropriate steps may be taken to cure the fault to l...

A ground fault module is designed for ease of assembly within a ground fault circuit breaker. The module houses the pre-assembled signal processor module, which contains the ground fault circuit interruption logic, along with the mechanical components required for translating the trip initiating response from the signal processor solenoid to the circuit breaker operating mechanism. The ground fault test button and related circuitry are also supported within the ground fault module.

A fault tolerant computer system has a central processing system which includes at least one set of data pathways, and executes a series of data processing instructions including the transfer of messages along the plurality of data pathways. At least one set of transaction data storage devices are coupled to the data pathways for storing a predetermined number of successive messages transferred most recently on the data pathways. Error checking devices are included for detecting the presence of ...

A circuit is disclosed for detecting ground faults and neutral faults and for providing power interruption in response thereto. The circuit monitors the current flow in the line and neutral conductors and provides a signal to a power interruption circuit in the event that a ground fault or a neutral fault condition is detected. In addition, a signal having a certain frequency is generated and coupled on the neutral line to enhance the probability of detecting neutral faults.

A fault detector circuit in a silicon controlled rectifier (SCR) control for series-connected direct-current motors in which current to the motor flows in pulses through a main SCR as the main SCR is repeatedly turned on and off. If during operation the main SCR shorts, the field winding is disconnected from the armature and maintained disconnected. If during operation the main SCR is not defective but fails to commutate, the field winding is disconnected from the armature and then reconnected t...