Abstract

An arc fault current detector for an electricity supply having at least two supply conductors (P1, P2) comprises a coil (L1) disposed adjacent to but not surrounding at least one of the conductors and inductively coupled thereto. A circuit (14) is connected to the coil for detecting a signal induced in the coil having frequency characteristics corresponding to an arc fault in the supply.

IPC Classes  ?

• H02H 1/00 - Details of emergency protective circuit arrangements
• G01R 31/12 - Testing dielectric strength or breakdown voltage
• H02H 3/46 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to frequency deviations
• H01F 38/28 - Current transformers

Abstract

A residual current device (RCD) comprises test circuitry which issues intermittent first test pulses each simulating a residual current fault for which a corresponding fault signal is generated. In the case of a fault in which a corresponding fault signal is not received in respect of a first pulse, the RCD attempts to force the load contacts open. The test circuitry further issues intermittent second test pulses at a frequency less than that of the first test pulses, each second test pulse simulating a residual current for which a corresponding fault signal is generated. The duration of each corresponding fault signal is greater than the response time of the load contacts to allow the load contacts to open. If the test circuitry detects that the load contacts do not open, the RCD attempts to force the load contacts open.

IPC Classes  ?

• H02H 3/08 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to excess current
• H01H 83/04 - Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by earth fault currents with testing means for indicating the ability of the switch or relay to function properly
• H01H 83/14 - Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by imbalance of two or more currents or voltages, e.g. for differential protection
• H02H 3/33 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to difference between voltages or between currentsEmergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers

Goods & Services

Electrical safety and protection products; residual current devices; residual current monitors; remote control plugs and sockets; surge suppressors; radio frequency interference suppressors, leakage current detectors, arc fault detectors, overvoltage detectors.

Abstract

A device for detecting a fault in an AC supply comprising a detection circuit for detecting a fault in an AC supply to a load and providing a corresponding output. A disconnect circuit disconnects the load from the supply in response to an output from the detection circuit. The device also includes a generator of intermittent test pulses, and a test circuit coupled to the detection circuit and containing a first solid state switch. Each test pulse turns on the solid state switch for the duration of the test pulse so that a current simulating the fault flows intermittently in the test circuit and a corresponding output is provided by the detection circuit. The device further comprising means to disable the disconnect circuit in response to each test pulse.

IPC Classes  ?

• H02H 3/00 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection
• H02H 3/08 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to excess current
• H02H 3/04 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned
• H02H 3/16 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to fault current to earth, frame or mass
• H02H 3/33 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to difference between voltages or between currentsEmergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
• G01R 31/42 - AC power supplies

Abstract

A residual current device (RCD) comprises test circuitry which issues intermittent first test pulses each simulating a residual current fault for which a corresponding fault signal is generated. In the case of a fault in which a corresponding fault signal is not received in respect of a first pulse, the RCD attempts to force the load contacts open. The test circuitry further issues intermittent second test pulses at a frequency less than that of the first test pulses, each second test pulse simulating a residual current for which a corresponding fault signal is generated. The duration of each corresponding fault signal is greater than the response time of the load contacts to allow the load contacts to open. If the test circuitry detects that the load contacts do not open, the RCD attempts to force the load contacts open.

IPC Classes  ?

• H02H 3/08 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to excess current
• H01H 83/04 - Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by earth fault currents with testing means for indicating the ability of the switch or relay to function properly
• H01H 83/14 - Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by imbalance of two or more currents or voltages, e.g. for differential protection
• H02H 3/33 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to difference between voltages or between currentsEmergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers

Goods & Services

Electric and electronic apparatus and instruments and parts and fittings thereof; electrical safety and protection products; residual current devices; residual current monitors; remote control plugs and sockets; surge suppressors; radio frequency interference suppressors, leakage current detectors, arc fault detectors, overvoltage detectors.

Goods & Services

Electric and electronic apparatus and instruments and parts and fittings thereof, namely, electric switches and circuit breakers; Electrical safety and protection products, namely, electronic monitors for monitoring electric current; Residual current devices, namely, ground fault circuit interrupters; electronic residual current monitors; remote control plugs and sockets; voltage surge suppressors; radio frequency interference suppressors, leakage current detectors, arc fault detectors, overvoltage detectors

Abstract

A fault detecting device having a plurality of supply conductors, including a first current transformer having a primary winding comprising at least two supply conductors and a secondary winding into which a current is induced in response to a fault current in the primary winding. A fault detection circuit connects the secondary winding to an electromechanical actuator having mechanical contacts in the supply conductors, the fault detection circuit generating an output signal to the actuator when an induced current is detected in the secondary winding, the output signal causing the actuator to open the mechanical contacts. The device further includes a second current transformer having a primary winding connected to an oscillator and a secondary winding comprising at least one supply conductor, the second current transformer arranged to induce an oscillating current into the at least one supply conductor in the event of a fault condition.

IPC Classes  ?

• H01H 35/00 - Switches operated by change of a physical condition
• H01H 83/00 - Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current
• H02H 3/33 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to difference between voltages or between currentsEmergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
• H02H 3/16 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to fault current to earth, frame or mass

Abstract

A device for detecting a fault in an AC supply comprises a circuit (CT, 100) for detecting a fault in an AC supply to a load (LD) and providing a corresponding output (IO), and an electromechanical switch means (SOLI, SWI) to disconnect the load from the supply if said output persists for at least a certain period of time. The device includes a generator (30) of intermittent test pulses each simulating a fault. In certain embodiments the duration of each test pulse is less than said certain period of time, and the circuit includes means (D2) for providing a visual and/or audible indication in response to the detection of test pulses by the detecting circuit.

IPC Classes  ?

• H02H 9/08 - Limitation or suppression of earth fault currents, e.g. Petersen coil
• H02H 3/16 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to fault current to earth, frame or mass
• H02H 3/33 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to difference between voltages or between currentsEmergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
• H02H 3/44 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to the rate of change of electrical quantities

Abstract

A circuit for detecting a DC current in a conductor (L1) includes a current transformer (CT) having a ferromagnetic core (10), a primary winding comprising the conductor (L1) and at least one secondary winding (W1). The circuit further includes an oscillator (12) for supplying an oscillating signal across the secondary winding and means for detecting a dc offset in the current flowing in the oscillator circuit. The circuit includes a capacitor (C1) in series with the secondary winding, and the detecting means is arranged to detect a non-zero voltage across the capacitor above a certain level.

IPC Classes  ?

• G01R 15/18 - Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers

Abstract

An arc fault detector comprises a current transformer (CT) having a primary winding and a secondary winding (W1), the primary winding being formed by at least one conductor (L) of an AC or DC supply circuit. The inductance of the CT is selected so that the CT has a lower frequency operating point (LFOP) of at least 10 KHz. The detector also comprises circuitry (10, 12, SW) for disconnecting the supply if the voltage induced in the secondary winding meets predetermined criteria as to magnitude and duration.

IPC Classes  ?

• H02H 3/26 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to difference between voltages or between currentsEmergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to phase angle between voltages or between currents

Abstract

A device for detecting a fault in an AC supply comprises a circuit (CT, 100) for detecting a particular type of fault in an AC supply to a load (LD) and providing a corresponding output (10). A relay (RLA) is responsive to said output (10) to open a set of load contacts (SW1) in the AC supply to disconnect the load from the supply. Test means (TS, Rt, W2) are provided for simulating a supply fault of the said type, and means (C3, R5, SCR2, SOL, SW2) are provided for causing the load contacts (SW1) to open if they do not open in response to the simulated fault within a certain period of time.

IPC Classes  ?

• H02H 3/00 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection
• H02H 9/08 - Limitation or suppression of earth fault currents, e.g. Petersen coil
• H02H 3/33 - Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to difference between voltages or between currentsEmergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition, with or without subsequent reconnection responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
• H02H 7/00 - Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
• G01R 31/42 - AC power supplies