Abstract: A power distribution system isolator is provided including a trailer having a hitch and a pair of wheels for transportation purposes. Also included is an electrical assembly with a fuse and a pair of cables each connected to the fuse for connecting to a power distribution system to isolate the same.

Abstract: A ground fault and over-voltage detector and method is disclosed for sensing a loss of neutral continuity between the respective neutral conductors of a ground power unit and an aircraft power system coupled to the unit. The detector includes a feedback path for carrying a feedback signal from the aircraft to the ground power unit. The feedback signal comprises a voltage signal referenced to the aircraft neutral and includes a ground fault voltage component. The detector further includes a signal conditioner disposed in the ground power unit for receiving the feedback signal and generating a signal representative of the magnitude of the ground fault voltage component. A comparator connected to the output of the signal conditioner contrasts the ground fault voltage magnitude signal to a predetermined threshold and a cutoff mechanism responsive to the comparator, when the ground fault voltage is greater than the threshold, to interrupt ground power from the ground power unit to the aircraft.

Abstract: A three-phase electrical system includes an interrupt controller. The interrupt controller protects against inadvertent current flow between a phase conductor and ground and between phase conductors. The interrupt controller measures the voltage across a series connection of current transformers disposed about various phase conductors. If an inadvertent current path exists between one of the phase conductors and ground or between two of the phase conductors, the interrupt controller interrupts the current flow in the phase conductors. Additionally, a single-phase electrical system with a hot conductor and a neutral conductor includes an interrupt controller. The interrupt controller protects against inadvertent current flow between the hat conductor and ground and between the hot conductor and the neutral conductor. The interrupt controller measures the voltage across a series connection of current transformers disposed about the hot and neutral conductors.

Abstract: The present invention is directed to a system for sensing fault current flowing through a person who touches an exposed conductor in a cable connecting a machine to a power distribution center wherein the power distribution center has a number of power cables for connecting a number of machines thereto. Each power cable has a different frequency impressed thereon by an oscillator which frequency is transmitted through an electrical path including the power center if the operator touches the fault. A sensing circuit for each cable is connected in the electrical path and tuned to only the frequency applied to that cable. When the sensing circuit detects that frequency, the sensing circuit interrupts power to the cable. If, for some reason, the sensing circuit fails to interrupt power to the cable, within a selected time interval of less than one-half second, a backup system interrupts power to the entire power center.

Abstract: A leakage voltage inductor serves as an electrical safety protection device used to send an instant alarm or to cut off the power when a leakage is detected in an electric appliance, the device being used to send the alarm and to cut off the power automatically whenever a potential difference of more than 6V is detected between the housing of the appliance and the ground on which a person stands, for electrical safety protection purpose.

Abstract: System For Detecting A Breakage Of A Power Cable For An Elevator System Which can accurately detect the breakage of at least one copper wire in the respective power cables present between the inverter of the elevator system and a linear motor moving element and which is difficult to visually inspect.

Abstract: An electrical apparatus for magnetothermal and differential protection, of the type comprising a device for sensing differential currents associated with a magnetothermal protection switch, comprises a differential current sensor connected to an input of a controlled gain signal amplifier, in turn connected to a plurality of light indicators arranged to go on progressively in dependence on the sensor. The apparatus provides a quantitative and qualitative measurement of the stray current.

Abstract: An electrical ground fault detection and limitation system for employment with a nuclear reactor utilizing a liquid metal coolant. Elongate electromagnetic pumps submerged within the liquid metal coolant and electrical support equipment experiencing an insulation breakdown occasion the development of electrical ground fault current. Without some form of detection and control, these currents may build to damaging power levels to expose the pump drive components to liquid metal coolant such as sodium with resultant undesirable secondary effects. Such electrical ground fault currents are detected and controlled through the employment of an isolated power input to the pumps and with the use of a ground fault control conductor providing a direct return path from the affected components to the power source.

Abstract: A gas insulated switchgear system having two gas insulated switchgear equipments, each of which consists of first disconnecting switches, circuit breakers, and second disconnecting switches, three phase gas insulated buses which are respectively connected to the first disconnecting switches of the two gas insulated switchgear equipments in every three phases thereof, a single phase reserve buses which are commonly connected to all of the second disconnecting switches of the two gas insulated switchgear equipments, and an operating device for opening the circuit breakers and the first disconnecting switches in only one phase of the gas insulated switchgear equipments and closing the second disconnecting switch in only the one phase. A gas insulated switchgear system having single phase reserve bus is economical and switches one of the three phase main buses to the single reserve bus without forming short circuit.

Abstract: A signal representative of the zero sequence current is obtained from current transformers associated with each phase and with the neutral if applicable by separate summing, in two distinct conductors, of the positive half-wave currents and of the absolute value of the negative half-wave currents produced by the set of current transformers, the difference between the currents flowing through these two conductors being representative of the zero sequence current.

Abstract: A protective grounding and referencing arrangement for a high-voltage, high-energy bulk supply is provided in the present invention. Isolation from ground is provided through the use of an isolation transformer connected between the a-c utility supply and the rectifiers which are provided for conversion to d-c. The d-c bus and its energy storage capacitors are then referenced to ground by a high resistance divider network. In such an arrangement the likelihood of an insulation breakdown to ground is significantly reduced. More importantly, in the event that such a breakdown should occur from one or the other terminal of the d-c bus the fault currents that result are limited by the referencing arrangement to a safe level. The energy hazard is thus very significantly reduced for the equipment.

Abstract: An electric shock protector apparatus includes a circuit for detecting an electric shock current signal which has a frequency substantially higher than the line frequency of a power distribution system. The current of the power system is passed through a filter which eliminates the power supply frequency and produces a signal indicative of an electric shock current. The electric shock current signal is passed to positive and negative half-cycle operation signal circuits which transmit signals to a logic gate for operating a relay to disconnect the power source from the line conductors.

Abstract: Improved shock and electrical-fire protection circuits provide line-to-ground plus "line-to-line" fault protection in a power system, and monitor conditions after protective interruption to safely provide automatic restoration of current when the fault is cleared. Both full-wave and half-wave circuits employ less expensive component combinations, including rectifiers and electromagnetic relays, to carry and switch load current. Protection is provided against the possibility of semi-conductor failure and the hazards associated with severed power conductors. A specialized resistance network fault detector for sensitizing enclosures, a hybrid zero sequence current transformer system and polyphase supply provide additional features.

Abstract: Electronic system grounding includes two system grounding paths for card cage electronic modules, with a first grounding path through the card cage and a second grounding path through the system power supply. The two system grounding paths are used to minimize noise and reduce unwanted induced superimposed transient voltage levels.

Abstract: An apparatus and method for continuously monitoring and detecting an open ground connection which may occur anywhere between the chassis of an electrical appliance and the grounding terminal of a receptacle. The apparatus includes a plug having a grounding blade and a sensing blade which together form an assembly adapted for insertion into the grounding terminal of the receptacle. When inserted into the grounding terminal, the grounding and sensing blades complete a closed current path formed by a sensing conductor connected to the sensing blade and a grounding conductor connected to the grounding blade. The sensing conductor is connected to an inverter and the input of the inverter is also connected through a resistor to the DC power source so as to place the small current on the sensing conductor at the input of the inverter.

Abstract: In accordance with the present invention, an electrical system is provided for disconnecting a power source from a load when a voltage potential in excess of a predetermined threshold is detected between a test point and a selected voltage reference point. Switch means is electrically connected intermediate the power source and the load for switchably connecting and disconnecting the power source with the load. Voltage-reference means provides predetermined reference voltage at the selected voltage reference point. Voltage-detection means is electrically connected with the test point and the selected voltage reference point for detecting when the voltage potential between the test point and the selected voltage reference point exceeds the predetermined threshold. Switch-actuator means responsive to the detection means is provided for actuating the switch means to disconnect the power source from the load when voltage potential in excess of the predetermined threshold is detected by the detection means.

Abstract: This invention relates to an arrangement for attaching discrete electrical components to a generally flat layer of sheet material. Both mechanical and electrical connections are provided by the attachment elements of the present invention. One form of the invention is directed to a membrane switch keyboard wherein one of the layers of the membrane switch has a tail extending therefrom. The tail has a free end which is adhesively secured to some portion of the keyboard. Conductive traces are formed on the tail and extend to the free end where they contact the leads of an electrical component. The component is held between the tail and the keyboard. In another aspect, which may be applied to the membrane switch keyboard just described, the invention includes a sheet material having two or more slits cut therein for each of the component's leads. The slits are cut in a portion of the sheet having conductive traces formed thereon.

Abstract: There is disclosed a monitoring system for insuring the continuity and integrity of a power distribution system comprising a plurality of trailing cables, each trailing cable connected at a central station to a common power source and transmitting a power energizing signal to a load disposed at a remote location. In particular, the monitoring system comprises a transmitter and receiver for each trailing cable of the power distribution system whereby a monitoring signal is transmitted from the central station to the remote location and returned to be detected by the receiver. If there is a fault condition within the trailing cable, the receiver provides a signal indicative thereof to be applied to a circuit breaker or coupling switch actuating the coupling switch to its open position thereby disconnecting the power from the trailing cable and its load.

Abstract: Disclosed is a ground conductor monitoring system which makes efficient use of an audio signal to continuously check the continuity of at least the ground conductor of a cable system.

Abstract: A plural phase high current low voltage load break switch with built-in ground fault sensing comprises an insulator base and a plurality of individual phase circuits mounted on and extending across the base in parallel spaced relation to each other, each phase circuit including, in series, an input connector, a fixed switch contact, a movable switch contact, a fuse, and an output conductor; a neutral conductor is mounted on and extends across the base in parallel spaced relation to the phase circuits. A switch operator mechanism mounted on the base is connected to all of the movable switch contacts for opening and closing these contacts simultaneously; that mechanism includes an electrically operated trip actuator for actuating the operator mechanism to open the switch contacts. A zero sequence ground fault sensor coil is disposed in encompassing relation to all of the phase circuits and the neutal conductor; the sensor coil is aligned with the movable switch contacts.

Abstract: An improved ground monitoring circuit for detecting the integrity and proper connection of the ground conductors in an electrical cable of an electrical power distribution system of a type that is commonly used at a surface mining site. A complete conductive loop is established between the ground conductor, or conductors, and the ground check, or pilot wire of the cable. A sensing signal at a frequency higher than the power frequency is coupled onto the ground monitoring loop. The monitoring loop includes a terminating resistor of predetermined value. The sensing signal on the ground conductor in the loop is isolated from local ground by means of an impedance element that presents a high impedance at the sensing signal but not at the power frequency. The impedance element is connected between the ground conductor of the power cable and the local ground.

Abstract: This invention relates to an arrangement for attaching discrete electrical components to a generally flat layer of sheet material. Both mechanical and electrical connections are provided by the attachment elements of the present invention. One form of the invention is directed to a membrane switch keyboard wherein one of the layers of the membrane switch has a tail extending therefrom. The tail has a free end which is adhesively secured to some portion of the keyboard. Conductive traces are formed on the tail and extend to the free end where they contact the leads of an electrical component. The component is held between the tail and the keyboard. In another aspect, which may be applied to the membrane switch keyboard just described, the invention includes a sheet material having two or more slits cut therein for each of the component's leads. The slits are cut in a portion of the sheet having conductive traces formed thereon.

Abstract: The secondary currents of plural current transformers are applied to a full-wave rectifying network for developing an overcurrent signal and a ground fault current signal; the latter flowing in a circuit path embraced by the toroidal core of a miniature current transformer. A transformed ground fault current signal appearing in the multi-turn secondary winding thereof is applied to a ground fault trip mode network operating to measure the signal magnitude against an adjustably established, continuous ground fault trip-time curve including a vertical pick-up curve portion and a sloping inverse time (I.sup.2 t) delay portion which terminates in a selected one of plural horizontal, fixed time delay portions pursuant to issuing an appropriately delayed ground fault trip signal. Provisions for zone selective interlocking between upstream and downstream breakers are also described.

Abstract: A circuit breaker having an electronic fault sensing and trip initiating unit which provides increased versatility and ability to coordinate the circuit breaker with other interrupting and protective devices in a wide variety of electrical distribution systems. Electronic circuits and components are provided to vary the ampere rating of the breaker, to adjust current carrying capacity, to provide a long time delay trip, a short time delay trip and an instantaneous trip depending on the amplitude of high fault currents, to provide a ground fault trip, to shorten or lengthen the trip time for short time delay faults and for ground faults, and to provide shunt trip capability. The tripping mechanism is magnetic and mechanical, and includes a plunger movable between a trip and non-trip position controlled by an electronic switch in the electronic circuitry, and a toggle mechanism which is unlatched by the plunger when it moves to the trip position.

Abstract: A circuit breaker having an electronic fault sensing and trip initiating unit which provides increased versatility and ability to coordinate the circuit breaker with other interrupting and protective devices in a wide variety of electrical distribution systems. Electronic circuits and components are provided to vary the ampere rating of the breaker, to adjust current carrying capacity, to provide a long time delay trip, a short time delay trip and an instantaneous trip depending on the amplitude of high fault currents, to provide a ground fault trip, to shorten or lengthen the trip time for short time delay faults and for ground faults, and to provide shunt trip capability. The tripping mechanism is magnetic and mechanical, and includes a plunger movable between a trip and non-trip position controlled by an electronic switch in the electronic circuitry, and a toggle mechanism which is unlatched by the plunger when it moves to the trip position.

Abstract: A system for monitoring the continuity of at least the ground wire of a cable connected between a mining machine and a power center. At the power center, a monitor signal is coupled to multi-phase power conductors of the cable through a multi-phase filter. The monitor signal from the conductors is coupled to the ground wire at the mining machine through another multi-phase filter. The signal returns through the ground wire to the power center where a current transformer couples the signal from the ground wire to a receiver. The receiver which receives and senses the characteristics of the returned signal includes parallel phase locked loop discriminators to prevent false tripping of the main power breaker if the monitor frequency should vary only slightly. The parallel discriminators provide a fail safe arrangement to prevent the main power breaker from remaining closed if one of the parallel discriminators should malfunction.

Abstract: To detect system ground faults and shorted alternator output winding turn-to-turn faults, the series combination of a resistor and the operating coil of an electrical relay having a normally closed contact pair is connected between the neutrals of two parallel connected polyphase alternator output winding groups, the junction between the resistor and operating coil is connected through a resistor to ground and the normally closed relay contact pair is connected in series in the alternator exciting field winding energizing circuit. To detect open diodes in the main polyphase diode bridge type full-wave rectifier circuit, an auxiliary polyphase full-wave rectifier circuit having the operating coil and normally closed contacts of two relays in series in each leg is provided. Upon the failure of a diode of the main rectifier circuit, sufficient current to operate the corresponding relay in the auxiliary rectifier circuit is diverted therethrough.

Abstract: Various embodiments of a ground fault protection system are disclosed for protecting a multiple source distribution network consisting of at least two sources having their neutral points interconnected by main neutral and tie neutral bus and also typically by separate ground connections. The system operates to selectively trip a ground fault circuit interrupter by distinguishing between normal neutral loading regardless of the routes taken by neutral currents in returning to the sources and a ground fault regardless of the routes taken by ground fault currents in returning to the source feeding the fault.

Abstract: Disclosed is a system for monitoring the resistance in the pilot and ground conductors of a power cable and for interrupting power if the resistance exceeds a predetermined limit established for the particular cable. Novel circuit arrangements are employed to reset and calibrate the system.

Abstract: A system and method for monitoring the continuity of a ground conductor in a power transmission system. A plurality of power transmission cables extend between a power source and a load and include a ground conductor extending between the source and the load. The monitoring system includes a transmitter for transmitting a signal within the audio range over the ground conductor. A receiver receives the signal from the transmitter over the ground conductor. The receiver has associated therewith an alarm device and/or a circuit breaker. In response to the absence of the signal at the receiver which would correspond to an interruption in the ground conductor, the circuit breaker is opened to disconnect the power source from the load. Both the receiver and transmitter are coupled to the ground conductor through closed inductive systems comprising toroids.

Abstract: A conventional residential ground fault circuit interrupting (GFCI) device is utilized to control a traditional circuit interrupter in protecting a large power distribution circuit against ground faults. The GFCI device is connected in an energization circuit for a solenoid operable to open the interrupter contacts. A sensor responds to ground faults on the distribution circuit by impressing the current signal on one side of the energization circuit, thus creating a current imbalance effective to trip the GFCI device. Interruption of the energization circuit causes the solenoid to initiate opening of the interrupter contacts. In an alternative embodiment, the GFCI device is adapted to initiate opening of the interrupter contacts upon degradation of ground circuit continuity.

Abstract: A conventional residential ground fault circuit interrupting (GFCI) device is utilized to control a traditional circuit interrupter in protecting a large power distribution circuit against ground faults. The GFCI device is connected in an energization circuit for a solenoid operable to open the interrupter contacts. A sensor responds to ground faults on the distribution circuit by impressing the current signal on one side of the energization circuit, thus creating a current imbalance effective to trip the GFCI device. Interruption of the energization circuit causes the solenoid to initiate opening of the interrupter contacts. In an alternative embodiment, the GFCI device is adapted to initiate opening of the interrupter contacts upon degradation of ground circuit continuity.