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    • 专利摘要:
    MULTIPOLAR ARC FAULT CIRCUIT BREAKER INCLUDING A NEUTRAL CURRENT SENSOR A fault detection system is provided for a power distribution system having at least first and second line conductors carrying AC currents that are out of phase with each other from a source to a load , and a common neutral conductor. The system includes an arc-fault current sensor comprising a coil wound on a hollow core and coupled to both line conductors so that electrical currents in the line conductors flow in opposite directions within the hollow core, and thus induce in the coil an output signal which is a function of the difference in electrical currents in said line conductors. A neutral current sensor produces an output signal representing the magnitude and phase direction of current in said neutral conductor. An arc-fault detection circuit includes a processor programmed to (1) respond to a change in the first output signal attributable at least in part to current in a line-to-line circuit, (2) if the response is in the affirmative, determine that a scaling factor is used to fit (...).
    公开号:BR112013011931B1
    申请号:R112013011931-4
    申请日:2011-10-20
    公开日:2021-08-31
    发明作者:Gary W. Scott；Paul A. Reid
    申请人:Schneider Electric Usa, Inc；
    IPC主号:
    专利说明:

    FIELD OF THE INVENTION
    [001] The present invention refers, in general, to multipole circuit breakers that are capable of detecting ground faults and arc failure. FUNDAMENTALS OF THE INVENTION
    [002] Multi-pole circuit breakers are used when it is necessary or desirable to simultaneously interrupt the flow of current in two or more power conductors. One example is the bipolar circuit breaker which is widely used to meet requirements that require all ungrounded conductors in a multi-wire branch circuit to be opened simultaneously. In a 120/240V power circuit, for example, the two phase conductors can be connected to a single 240V load, such as an electric stove, or to two separate 120V loads, and so the circuit must be able to open both phase conductors simultaneously. Bipolar circuit breakers capable of detecting ground fault and arc-fault have been known for some time, but these circuit breakers generally required separate current sensors for the two phase conductors. SUMMARY
    [003] According to an embodiment, there is provided a fault detection system for a power distribution system having at least first and second phase conductors that carry AC currents that are out of phase with each other from a source to a load, and a common neutral conductor. The system includes an arc-fault current sensor comprising a coil wound on a hollow core and adapted to be coupled to both phase conductors so that electrical currents in the phase conductors flow in opposite directions within the hollow core and thus inducing in the coil a first output signal which is a function of the difference in electrical currents in the phase conductors. A neutral current sensor produces a second output signal representing the magnitude and phase direction of current in the neutral conductor. An arc-fault detection circuit receives the first output signal and includes a processor that receives the first and second output signals and programmed to (1) respond to a change in the first output signal to analyze the second output signal for determine whether the change in the first output signal is attributable at least in part to current in a phase-to-phase circuit, (2) if the answer is yes, determine that a scaling factor is used to adjust the value of the first output signal , and (3) analyzing the first adjusted output signal to determine if an arc fault has occurred and produce a trip signal in response to detection of an arc fault.
    [004] The system may also include a sensing and current detection circuit with a ground fault. The ground fault detection circuit receives the output signal from the ground fault current sensor and produces a trip signal in response to the detection of a ground fault. A phase-to-ground fault produces a voltage at the ground-fault sensor, but a phase-to-phase fault or phase-to-neutral fault does not.
    [005] A specific application is in a bipolar circuit breaker for use in a three-wire AC power distribution system, single-phase, 120 V to neutral, 240 V phase-to-phase, in which the currents in two phases of 120 V are 180° out of phase with each other. The fault detection system senses the presence of an arc current in one or both circuits or poles of a bipolar circuit breaker containing the neutral conductor, and eliminates the arc by disconnecting both 120 volt phases, which are also the phases of 240 volts.
    [006] A parallel arc fault that occurs from phase-neutral is captured as large current fluctuations (generally greater than three times the direct current rating of the circuit). An algorithm determines that an arc is in a phase-neutral circuit by the presence of equal fluctuations in the output signals coming from both the arc-fault current sensor and the neutral current sensor. The absence of current fluctuations in the neutral current sensor output signal indicates that no phase-to-phase arc occurs, and an algorithm applies an appropriate scaling factor to the arc-fault current sensor signal.
    [007] According to another aspect of the present disclosure, a product that is a computer program is disclosed. The computer includes one or more tangible, non-transient media having computer-readable program logic incorporated therein. The computer-readable program logic is configured to run so as to implement a method for detecting failure in a power distribution system having at least first and second phase conductors that carry AC currents that are out of phase with one another from a source. for a load, and a common neutral conductor. The method includes producing a first signal that is a function of the difference in electrical currents in the first and second phase conductors, and producing a second signal representing the magnitude and phase direction of current in said neutral conductor. The method further includes analyzing the second signal, in response to a change in the first signal, to determine whether the change in the first signal is attributable at least in part to current in a phase-to-phase circuit and, if the answer is yes, determining a scaling factor to be used to adjust the value of the first signal, then analyze the first adjusted signal to determine if an arc fault has occurred.
    [008] According to another aspect of the present disclosure, a method is disclosed for detecting failure in a power distribution system having at least first and second phase conductors carrying AC currents that are out of phase with each other from a source to a load, and a common neutral conductor. The method includes producing a first signal that is a function of the difference in electrical currents in the first and second phase conductors, and producing a second signal representing the magnitude and phase direction of current in said neutral conductor. The method further includes analyzing the second signal, in response to a change in the first signal, to determine whether the change in the first signal is attributable at least in part to current in a phase-to-phase circuit and, if the answer is yes, determining a scaling factor to be used to adjust the value of the first signal, then analyze the first adjusted signal to determine if an arc fault has occurred.
    [009] The indicated aspects and other aspects of the present invention will be clear to those of ordinary skill in the art in view of the detailed description of various embodiments, which is made with reference to the drawings, a brief description of which will be provided below. BRIEF DESCRIPTION OF THE DRAWINGS
    [010] The invention will be better understood from the following description of the preferred embodiments, together with a reference to the accompanying drawings, in which:
    [011] Figure 1 is a schematic diagram of a three-wire, 120V to neutral, 240V phase-to-phase, three-wire AC power distribution system equipped with a bipolar circuit breaker.
    [012] Figure 2 is a graph of the outputs of the arc-fault current sensor and the neutral current sensor represented in opposition, both signals being represented as multiples of the nominal current.
    [013] Figure 3 is a more detailed functional block diagram of a system for fault detection using the sensor arrangement of Figure 1. DETAILED DESCRIPTION
    [014] Although the invention will be described in connection with some preferred embodiments, it will be understood that the invention is not limited to those specific embodiments. Rather, the invention is intended to cover all alternatives, modifications, and equivalent arrangements that may fall within the spirit and scope of the invention as defined by the appended claims.
    [015] In Figure 1, a pair of 120 volt power supplies 10a and 10b is connected to one or more electrical loads 11 via three phases L1, L2 and N. Power supplies 10a and 10b are typically provided by a winding center tapped secondary of a distribution transformer having a primary winding that receives an input voltage from a supply company transmission line. The center tap of the secondary winding is connected to the grounded neutral phase N, and opposite ends of the secondary winding are connected to phases L1 and L2. This arrangement forms a first 120 volt supply through phases L1 and N, a second 120 volt supply through phases L2 and N, and a 240 volt supply through phases L1 and L2. Each of the three supplies is single-phase, and the two 120-volt supplies are out of phase with each other. These are the three power supplies typically provided to residential users and small commercial power outlets in the United States.
    [016] A tripping mechanism 12 of a circuit breaker is coupled to phases L1, L2 and N between sources 10a, 10b, and load(s) 11, to open two pairs of contacts 13a, 13b and 14a, 14b when various types of failure are detected in the power circuit. Examples of faults like these are ground faults such as F1 fault from phase L2 to ground, parallel arc fault such as fault F2 between L1 and L2, and fault F3 between phase L2 and neutral, and fault arc in series that can be caused by a loose connection, a broken conductor or a worn insulation in any of the phases.
    [017] To detect ground fault in the illustrative system, a ground fault current sensor 20 is coupled to all three phases L1, L2 and N. All three conductors L1, L2 and N pass through a toroidal core 21 to form single-turn primary windings on that core. The electrical currents IL1, IL2 and IN in the three conductors L1, L2 and N, respectively, induce current flow Igf in a secondary winding 22. The magnitude of the induced current is: Igf= IL1 + IL2 + IN
    [018] When a ground fault occurs, the free current flow Igf induced in the secondary winding 22 increases to a level that can be detected by a controller 30, as is well known in the art. In the absence of a ground fault, the net current flow Igf induced in the secondary winding 22 is zero or close to zero. The ground fault sensor 20 senses any current that is not returned through one of the three wires. It is typically a copper winding around a magnetizable core with high permeability greater than about 5000 and a window large enough to pass the two phase wires L1 and L2 and the neutral wire N, similar to the sensor. lack of grounding described in US Patent 7,079,365 issued to Brown, which is assigned to the assignee of the present invention. The ground fault signal normally causes an instantaneous trip.
    [019] As indicated in Figure 1, the controller 30 includes a ground fault detection circuit 31 and an arc fault detection circuit 32. These two circuits 31 and 32 preferably share a common processor to analyze their respective signals. input to detect the occurrence of failure.
    [020] When a fault condition is detected by any of the detection circuits 31 and 32, the controller 30 produces a trigger signal that triggers the trigger mechanism 12 mechanically coupled to the moving contact in each of the two pairs of contacts 13a, 13b and 14a, 14b to simultaneously open both phases L1 and L2. The triggering mechanism typically includes a solenoid having a movable armature coupled to one or both movable contacts, which can be mechanically coupled together when the solenoid armature is coupled to only one of the movable contacts. As is conventional in circuit breakers, the moving contacts can also be opened manually, and can typically be closed by manual operation.
    [021] The ground fault detection circuit 31 may be a conventional circuit for generating a trip signal in response to the detection of a ground fault. An example of such a ground fault detection circuit is described in US Patent 7,193,827, assigned to the assignee of the present invention. The detection circuit described in that patent detects both ground faults and grounded neutrals with just a single current sensor. Typical thermomagnetic current sensing components such as a bimetallic overload and an instantaneous magnetic latch may be present as well.
    [022] To detect arc fault in the illustrative system, the two phases L1 and L2 are coupled to a shared arc fault current sensor 40 that includes a core 41 consisting of a low permeability magnetic material to form a di sensor. /dt. The phase segments L1 and L2 passing through the core 41 enter the interior of the core and exit it on opposite sides, so that currents flowing in the two conductors L1 and L2 have the same effect on a secondary winding 42 wound on the core 41. Specifically, as illustrated in Figure 1, the source end L1a of the segment of the L1 conductor passing through the core 41 is at the top of the core 41, and the charging end L1b of that segment of the L1 conductor is at the bottom of the core. 41. For conductor L2, the source end L2a of the segment of conductor L2 passing through the core 41 is at the bottom of the core 41, and the charging end L2b of that segment of the conductor L1 is at the top of the core 41.
    [023] The electrical currents in the two phase conductors L1 and L2 are 180° out of phase with each other. However, due to the fact that the lagged currents in the two phase segments L1 and L2 within core 41 flow in opposite directions, they both induce current flow in the same direction in the secondary winding 42. Thus, when a phase-arcing fault occurs In phase, the amplitude of the signal induced in the secondary winding 42 is increased by the additive effect of the two phase currents within the core 41. The core 41 preferably has a low level of magnetic permeability, so that the signals induced in the secondary winding 42 are signals di/dt, and the final output signal of the secondary winding 42 is the difference of the two di/dt signals induced in that winding by the currents flowing in the segments of the two phase conductors L1 and L2 passing through the core 41. A phase arc -phase will generate twice the signal as a neutral-phase arc. A series arc in a phase-to-phase load circuit will generate twice the signal as a series arc in a phase-to-neutral load circuit.
    [024] Core 41 of the shared arc-fault di/dt sensor has a sufficient number of turns in the winding to allow the sensor and associated filter components to produce an appropriate output signal over the specified circuit breaker current range. For example, the usable current range over which arcs can be detected can be from approximately 3 to 1000 amps. (Lack of grounding can be detected as early as 5 milliamps). Sensor 40 senses two-phase current fluctuations and is not magnetically saturated in the current range up to the trigger level of the instantaneous magnetic tripping component (eg, up to 15 times the circuit's direct current rating, which is the current that a circuit breaker is designed to carry continuously without overheating or excessive mechanical stress). Sensor 40 is generally a copper winding around a magnetizable core of low permeability of less than about 300 µm (air = 1), and a window large enough to pass the two phase wires. The output signal is a signal derived from the time equivalent to the di/dt of the two phases that pass through the window. This output signal can be time-integrated into Isaf, the actual current value.
    [025] In one example, the arc-fault sensor 40 is a toroid-type sensor having a magnetic permeability in the range of 10 to 100 µm, with 200 to 1000 turns in winding 42. Alternative structures for the sensor include multiple cores parts and coils that form a single sensor when assembled, and similar Hall effect or Giant Magnetic Resistance (“GMR”) sensors. An additional configuration for a three-pole arc-fault circuit breaker can use two di/dt current sensors instead of the three normally expected sensors.
    [026] When an arc fault occurs, the high frequency components resulting from the current flow induced in the secondary winding 42 allow the arc fault sensing circuit 32 to detect the occurrence of arc fault, as is well known in the art. The arc-fault detection circuit includes a processor programmed to analyze the second output signal from coil 42 and produce a trip signal in response to detection of an arc-fault. An example of such an arc-fault detection circuit is described in US Patent 7,345,860, which is assigned to the assignee of the present invention.
    [027] To detect whether an arc fault signal is one or both of the turns or phases through the di/dt sensor, a neutral current sensor 50 uses the inherent impedance of the neutral wire, represented by the resistor. R1 in Figure 1. The neutral current sensor consists of a low resistance shunt conductor (eg 0.0005 ohms) that produces a low voltage (eg 10 millivolts) at 20 amps of neutral current and can carry a complete short circuit current without destruction when necessary. Alternatively, the neutral current sensor can be an inductance that gives an indication of the magnitude of neutral current. The main purpose of the neutral current sensor is to indicate the level and phase direction of current in the neutral phase N. This enables the algorithms to arc detection, to determine whether an arc-fault signal is possibly due to a phase-to-neutral fault or a phase-to-phase fault, using the following equations: ILI = % (Isaf - IN) IL2= — % (Isaf + IN)
    [028] It is important to determine whether a change in the output signal of the shared arc fault sensor 40 is attributable to a change in current in a phase-to-phase load or in a phase-neutral load, such that the output signal of the sensor 40 can be appropriately scaled to accurately represent the actual magnitude of current in the circuit in which the change has occurred. The signal from the neutral current sensor 50 makes this determination possible, because the current flowing in the neutral conductor (IN = -ILI - IL2) will be zero when the change in current detected by sensor 40 is caused solely by a change in current in a phase-to-phase circuit, and will be equal to the current detected by sensor 40 when the change in current detected by sensor 40 is caused solely by a change in current in a single phase-neutral circuit. Thus, the magnitude of the neutral current sensor signal 50 can be used to determine which scale factor (SF) should be applied to the value represented by the output signal from sensor 40 before that value is used in an algorithm to determine if it occurred. an arc fault.
    [029] When the current in the neutral conductor is zero, a scaling factor SF of 0.5 is selected, and when the current in the neutral conductor is equal to that detected by the arc-fault current sensor 40, a scaling factor SF of 1.0 is selected (ie, there is no scaling). When the output signal from the neutral current sensor 50 represents a neutral current magnitude between zero and that of the current detected by the arc-fault sensor 40, a scaling factor SF between 0.5 and 1.0 is selected. When neutral current or its fluctuations have (have) a low magnitude compared to those of phase currents, any arc will likely be due to phase-to-phase currents, and so a scaling factor of 0.5 is applied to the signal of output of shared arc fault sensor 40, ie SF = 0.5(1 + IN/Isaf). When the neutral current has a greater magnitude, similar to that of the phase currents, then the arc will likely be due to a single-phase wire (ie, phase L1 or L2), and thus the fault sensor output signal per shared bow 40 remains at the 1.0 scale. For probable series arc faults, the scaling factor remains at 1.0 for all signals as long as the sum of IN and Isaf is less than 6 times the rated current.
    [030] A parallel arc fault is an arc occurring either phase-to-phase or phase-to-neutral and will likely be three times the rated current, which will be called “a 3X current”. A 3X arc fault is sensed by the di/dt sensor as a 3X current if it occurs phase-neutral, or as a 6X current if it occurs phase-to-phase.
    [031] The arc-fault algorithms used to determine if an arc-fault has occurred typically require an estimate of the phase current as well as the power factor of the loads. The nature of the shared arc-fault sensor 40 is that a current flowing through a phase-to-phase connected load will produce twice the signal at the arc-fault sensor as a current flowing through a phase-to-neutral load. In case the load is a mixture of phase-neutral and phase-phase loads, the fraction of current associated with a possible arc occurrence can be estimated. Figure 2 shows the scale factors from 0.5 to 1.0 that can be multiplied by the output signal from the shared arc fault sensor 40 to correct for the phase-to-phase currents that are detected by that sensor. This scaling factor is applied to current signals that represent at least a phase current rated 3X.
    [032] When the neutral current is zero, the arc signal is known to be entirely due to a phase-to-phase arc or to an arc in series with phase-to-phase loads. The resulting arc signal is thus scaled by 0.5 to account for the signal multiplier by 2 of the two turns across the sensor.
    [033] When the magnitude of the neutral current is equal to the output signal of the integrated shared arc fault sensor, it is known that the arc signal is due entirely to a single arc or a single phase-neutral load, and thus a 1.0 scaling factor is applied to the sensor output signal.
    [034] When the magnitude of the neutral current is between zero and the magnitude of the time-integrated output signal of the shared arc-fault sensor, the arc signal is assigned the worst (highest) case of the two possible phase currents, and an algorithm calculates an arc probability based on the scaling factor in Figure 2.
    [035] Figure 2 is a graph of Isaf versus IN, with both signals represented as multiples of the rated current. The scale on the right vertical axis and line B in Figure 2 are the SF values required to satisfy the equation SF = 0.5(1 + IN/Isaf). As shown in Figure 2, SF scaling factors are only applied to Isaf values that lie within the “parallel fault zone”, which is the region below line A and between line B and the right vertical axis. Line A represents IN=Isaf, and line B represents (IN+Isaf) = 6.
    [036] The region above line A is designated the "possible wiring error zone" because the current sensed by the neutral current sensor 20 has a higher multiple of the rated current than the current sensed by the arc-fault sensor 40, which indicates that an arc fault does not exist, but that there may be a wiring error.
    [037] The region below line A and to the left of line B is designated the "series fault zone" because the sum of the multiples of currents captured by the neutral current sensor 20 and the shared arc fault sensor 40 is smaller than 6 (IN + Isaf < 6), which indicates that any arc fault that exists is likely a series arc fault rather than a parallel arc fault. Thus, a scale factor of 1.0 is used for all Isaf values that fall within this region. The two effective turns on the shared arc fault sensor 40 automatically produce the same signal level for a typical series arc that occurs on a phase-to-neutral load or a phase-to-phase load.
    [038] A series arc has the property of imposing voltage fluctuations in series with the total voltage drop across the load. The current fluctuations resulting from a series arc current in a phase-to-neutral connected load circuit are twice as large as those in a phase-to-phase circuit. A small 1-volt change in the series arc causes twice as much change in current, or di/dt, in a 120-volt phase-to-neutral circuit than it would in a similar phase-to-phase current with a load of 240 volts.
    [039] An arc occurrence in a series connection is picked up via one di/dt sensor turn during a phase-to-neutral arc, but across both sensor turns during a phase-to-phase arc. The effect of turns is to multiply the series arc signal by two in a phase-to-phase circuit. This means that a 1 volt fluctuation in a series arc will create the same signal at the di/dt sensor regardless of whether or not the circuit contains a phase-phase charge or a phase-neutral charge.
    [040] Within the "parallel fault zone", the combined values of IN and Isaf indicate a potential arc fault, and thus the SF values in that zone are used to adjust the value integrated to the time of Isaf before it is used in the algorithms used to determine if an arc fault has occurred. In general, an output signal from sensor 40 that is at least triple the rated current will be considered an arc fault if the “signature” of that current otherwise meets the criteria for an arc fault. However, when the current sensed by sensor 40 is passing through a phase-to-phase load, the output signal from sensor 40 will have a magnitude that is twice that produced by a current passing through a phase-to-neutral load. This is because the change in current produced by an arc fault appears on both phases L1 and L2 with a phase-to-phase load, but on only one of the phases (L1 or L2) with a phase-to-neutral load.
    [041] For example, if the arc-fault sensor 40 produces a signal that, when time-integrated, represents a current Isaf of 200 A and the neutral current sensor produces a signal that represents a current IN of 60 A, and the circuit breaker is rated at 20 A, so Isaf is a multiple of three times the rated current. As can be seen from Figure 2, the SF scale factor for the present example is 0.65 (identified by an “x” in Figure 2), and thus the 200 A value of Isaf is multiplied by 0 .65 before being used in the algorithms to determine if an arc fault has occurred. In other words, the Isaf value used by those algorithms is 130 A instead of 200 A.
    [042] When the output signal from the neutral current sensor 50 represents a neutral current magnitude between zero and the current detected by the arc-fault sensor 40, the direction of change in the outputs of the two sensors 40 and 50 can be used to associate detected parallel arc to one of the two phases L1 or L2. Specifically, an increase in the neutral current signal by the neutral current sensor 50 will be associated with phase L1 if the output signal from the arc-fault sensor 40 increases. Similarly, a decrease in the neutral current signal by the neutral current sensor 50 will be associated with phase L1 if the output signal from the arc-fault sensor 40 increases, and with phase L2 if the output signal from the arc-fault sensor by 40 bow decrease.
    [043] As a further differentiation, the neutral current sensor signal 50 can be used to determine whether an arc fault is in a 120 volt circuit or a 240 volt circuit so that different algorithms can be used. For example, if the arc fault is on a 240 volt circuit, the algorithm used may trip the circuit breaker faster than the algorithm used for an arc fault on a 120 volt circuit (existing standards such as UL 1699 specify faster triggers for higher levels of arc-fault currents). If the signal from the neutral current sensor 50 indicates the possibility of an arc and is floating in phase with the signal from the arc-fault sensor 40, then the arc-fault is in a 120-volt circuit. The 120 volt loop algorithm is used to analyze any phase current indicated by the polarity of the current represented by the neutral current sensor output signal, and no scaling factor is applied to the output signal coming from the arc fault sensor 40 If the neutral current sensor signal 50 indicates current flowing in the neutral conductor, but it is not floating, then the arc fault is in a 240 volt circuit. The 240 volt loop algorithm is used to analyze the output signal coming from the arc fault sensor 40, using a scaling factor of 0.5.
    [044] Figure 3 is a more detailed functional block diagram of a fault detection system using the sensor arrangement of Figure 1. In one embodiment, the components of the ground fault sensor circuit 31 and the sensor circuit detector arc fault 32 are provided on a specific integrated circuit (ASIC) 60 for a given application. Suitable signals from the ASIC 60 are fed to a microcontroller or microprocessor 61 which, based on further analysis and processing of the signals provided by the ASIC 60, makes a decision as to whether or not to send a trigger signal. This trigger signal is used to activate trigger mechanism 12.
    [045] A wideband noise detector 62 comprises one or more bandpass filter circuits 63 that receive the rate of change of current signal from the di/dt sensor 40. The bands passed by these circuits 63 are selected to allow for detecting the presence of broadband noise in frequency ranges that are representative of a typical arc-fault frequency spectrum. Each of the bandpass filter circuits 63 feeds a filtered signal, comprising those components of a di/dt sensor input signal that fit within their respective bandpass frequency ranges, to a signal detector circuit 64.
    [046] The output of sensor 40 can also feed a time integration circuit or integrator 65. The integrator can be a passive resistor-capacitor circuit followed by an amplified integrator, whose output is proportional to the AC current. Integrator 65 provides a signal to be sampled by an analog to digital A/D converter 66. In one embodiment, the output of the A/D converter 66 is a series of 8-bit (minimum) values representing current at a rate of 32 samples per half cycle. The A/D converter can be a part of the microcontroller 61. As the frequency moves away from the nominal, the time between voltage zero crossings detected in a zero crossing detection circuit 67 is measured using internal timers and used to vary the sample rate to achieve a constant number of samples per cycle. Zero crossing detection circuit 67 receives voltage signals from a voltage sensor 71.
    [047] The wideband noise detector 62 determines if there is simultaneously a trigger level signal in two or more frequency bands. To do this, a portion of the signal from the di/dt sensor 40 is routed to bandpass filters 65. The minimum number of bandpass filters is two. The filter frequency ranges are chosen across the spectrum from 10 kHz to 100 kHz. In one example, for a two-band implementation, the center frequencies are 33 kHz and 58 kHz. In this example, the output signals from bandpass filters 63 are detected (rectified) and filtered with a low pass filter having a corner frequency of 5 kHz. The signal output from each frequency range is routed to a comparator (signal detector) 64, where it is compared to a reference voltage level, and, if sufficient, triggers an output pulse. The signal “trigger level” of each band required to produce a signal pulse from the comparator is determined by the application's non-arc-related load-generated signature analysis. Additional comparators (ND ports) are used to send a pulse whenever multiple filter bands simultaneously receive a trigger signal in their band. The resulting pulses indicating signal acquisition in multiple bands are counted by the microcontroller 61 and used in some arc detection algorithms.
    [048] The use of the terms "bandpass filter", "comparator", "AND port", and "integrator" does not limit the invention to hardware equivalents of these devices. Software equivalents of these functions can be implemented, provided that the di/dt signal (from sensor 40) is first amplified and converted to digital values.
    [049] In the illustrative mode, the voltage sensor 71 can be implemented as a resistor divider (not shown) that provides an attenuated voltage level compatible with solid state logic devices. The zero crossing circuit 67 can be implemented with a low pass filter (1kHz corner frequency) and comparators to provide a digital "1" when the voltage is above zero and a digital "0" when the voltage is below zero volts. The microcontroller 61 accepts the logic levels and incorporates timers to determine if the system frequency has increased or decreased from the previous cycle. The A/D sample rate is then adjusted faster or slower to maintain 64±1 samples per cycle.
    [050] Ground fault sensing circuit 31 feeds an absolute value circuit 68 that changes signals that are turning negative into positive signals and passes positive signals through without change. Positive signals are then provided to the microcontroller 61.
    [051] Figure 3 illustrates an embodiment of an ASIC 60 to perform the operations described above. Further details of an ASIC 60 and equivalent circuitry that may be used can be found in US Patent 6,246,556 assigned to the assignee of the present invention. Details regarding an algorithm used to analyze current waveforms and broadband noise to determine if an arc is present can be found in US Patent 6,259,996, assigned to the assignee of the present invention.
    [052] Although specific embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the exact construction and compositions described herein and that various modifications, changes, and variations may be made clear from the descriptions. carried out without departing from the spirit and scope of the invention as defined in the appended claims.
    权利要求:
    Claims (18)
    [0001]
    1. Fault detection system for a power distribution system having at least first and second phase conductors carrying AC currents that are out of phase with each other from a source (10a, 10b) to a load (11), and a conductor common neutral, comprising: an arc-fault current sensor (40) comprising a coil (42) wound on a hollow core (41) and coupled to both said phase conductors so that electrical currents in said conductors phase flow in opposite directions within said hollow core (41) and thus induce in said coil (42) a first output signal which is a function of the difference in electrical currents in said phase conductors, an arc fault detection circuit (32) receiving said first output signal and including a processor (61) receiving said first output signal, CHARACTERIZED in that it further comprises: a neutral current sensor (50) producing o a second output signal representing the magnitude and phase direction of current in said neutral conductor, and the processor (61) further receiving said second output signal and programmed to: respond to a change in said first output signal to analyze said second output signal to determine whether said change in said first output signal is attributable at least in part to current in a phase-to-phase circuit and, if the answer is yes, determine that a scaling factor is used to adjust the value of said first output signal, and analyze said first adjusted output signal to determine if an arc fault has occurred.
    [0002]
    A system according to claim 1, CHARACTERIZED in that said power distribution system has a nominal current, said processor (61) is programmed to compare the currents represented by said first and second power signals. output with said rated current, and to analyze said second output signal only when said current represented by said first output signal exceeds said rated current by a multiple of said rated current which is at least as large as the multiple by which said current represented by said second output signal exceeds said rated current.
    [0003]
    3. System according to claim 1, CHARACTERIZED by the fact that said power distribution system has a nominal current, said processor (61) is programmed to compare the currents represented by said first and second output signals with said rated current, and to analyze said second output signal only when said currents represented by said first and second output signals exceed said rated current by a predetermined amount.
    [0004]
    4. System according to claim 1, CHARACTERIZED by the fact that said processor (61) is programmed to determine a scale factor that is one half of the sum of one plus the ratio between said second output signal and the said first output signal.
    [0005]
    5. System according to claim 1, CHARACTERIZED by the fact that said processor (61) is programmed to determine whether said change in said first output signal is attributable solely to a change in current in a phase-to-phase circuit , and if the answer is yes, reduce the value of that first output signal by 50%.
    [0006]
    6. The system of claim 1, CHARACTERIZED by the fact that said processor (61) is programmed to determine whether said change in said first output signal is attributable solely to a change in current in a phase- neutral, and if the answer is yes, analyze that first output signal, without any adjustment, to determine if an arc fault has occurred.
    [0007]
    7. System according to claim 1, CHARACTERIZED by the fact that said power distribution system includes at least one 120 volt circuit and at least one 240 volt circuit, and said processor (61) is programmed to analyzing said first and second output signals to determine whether a change in said first output signal is attributable to a change in current in said 120 volt circuit or said 240 volt circuit.
    [0008]
    8. The system of claim 1, CHARACTERIZED in that said processor (61) is programmed to use the magnitude of said second output signal to determine whether a detected arc fault is a phase-arc fault. neutral or a phase-to-phase arc fault, based on the fact that said second output signal has a greater magnitude when a phase-to-neutral arc fault occurs than when a phase-to-phase arc fault occurs.
    [0009]
    9. System according to claim 1, CHARACTERIZED by the fact that said power distribution system has a nominal current, said processor (61) is programmed to compare the currents represented by said first and second output signals with said rated current, and to determine that there is a potential wiring error when said current represented by said second output signal exceeds said rated current by a multiple of said rated current which is greater than the multiple by which said current represented by said first output signal exceeds said rated current.
    [0010]
    10. System according to claim 1, CHARACTERIZED by the fact that said power distribution system has a nominal current, said processor (61) is programmed to compare the currents represented by said first and second output signals with said rated current, and to determine that there is a series arc fault when said currents represented by said first and second output signals exceed said rated current by an amount less than a predetermined amount.
    [0011]
    11. Method for detecting failures in a power distribution system having at least first and second phase conductors carrying AC currents that are out of phase with each other from a source (10a, 10b) to a load (11), and a conductor common neutral, comprising: producing a first signal that is a function of the difference in electrical currents in said first and second phase conductors, CHARACTERIZED by the fact that it additionally comprises: producing a second signal representing the magnitude and phase direction of current in the said neutral conductor, in response to a change in said first signal, analyzing the second signal to determine whether the change in said first signal is attributable at least in part to current in a phase-to-phase circuit and, if the answer is affirmative, to determine that a scaling factor be used to adjust the value of said first signal, and analyze said first adjusted signal to determine whether a fault has occurred. r bow.
    [0012]
    12. Method according to claim 11, CHARACTERIZED by the fact that said power distribution system has a rated current, and said method includes comparing the currents represented by said first and second signals with said rated current, and analyzing said second signal only when said current represented by said second signal exceeds said rated current by a multiple of said rated current which is at least as large as the multiple by which said current represented by said first signal exceeds said current nominal.
    [0013]
    13. Method according to claim 11, CHARACTERIZED by the fact that said power distribution system has a rated current, said method includes comparing the currents represented by said first and second signals with said rated current, and analyzing said second signal only when said currents represented by said first and second signals exceed said rated current by a predetermined amount.
    [0014]
    14. Method according to claim 11, CHARACTERIZED by the fact that it includes determining a scale factor that is one half of the sum of one plus the ratio between said second signal and said first signal.
    [0015]
    15. Method according to claim 11, CHARACTERIZED by the fact that it includes determining whether said change in said first signal is attributable solely to a change in current in a phase-to-phase circuit, and if the answer is affirmative, reducing the value of that first signal by 50%.
    [0016]
    16. Method according to claim 11, CHARACTERIZED by the fact that it includes determining whether said change in said first signal is attributable solely to a change in current in a phase-neutral circuit, and, if the answer is affirmative, analyze said first signal, without any adjustment, to determine if an arc fault has occurred.
    [0017]
    17. The method of claim 11, CHARACTERIZED in that said power distribution system includes at least one 120 volt circuit and at least one 240 volt circuit, and said method includes analyzing said first and second signals for determining whether a change in said first signal is attributable to a change in current in said 120 volt circuit or in said 240 volt circuit.
    [0018]
    18. The method of claim 11, CHARACTERIZED in that it includes using the magnitude of said second signal to determine whether a detected arc fault is a phase-neutral arc fault or a phase-phase arc fault, based on the fact that said second signal has a greater magnitude when a phase-neutral arc fault occurs than when a phase-phase arc fault occurs.
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    同族专利:
    公开号 | 公开日
    US20120119751A1|2012-05-17|
    CN103250316A|2013-08-14|
    EP2641311A1|2013-09-25|
    CN103250316B|2015-07-08|
    BR112013011931A2|2016-11-01|
    US8542021B2|2013-09-24|
    WO2012067750A1|2012-05-24|
    EP2641311B1|2015-12-30|
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    法律状态:
    2018-12-18| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2019-09-10| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2020-10-27| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|
    2021-07-27| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2021-08-17| B09W| Correction of the decision to grant [chapter 9.1.4 patent gazette]|Free format text: RETIFICACAO DO DESPACHO 9.1, PUBLICADO NA RPI 2638, DE 27/07/2021 |
    2021-08-31| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 20/10/2011, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    US12/947,001|US8542021B2|2010-11-16|2010-11-16|Multi-pole arcing fault circuit breaker including a neutral current sensor|
    US12/947,001|2010-11-16|
    PCT/US2011/057122|WO2012067750A1|2010-11-16|2011-10-20|Multi-pole arcing fault circuit breaker including a neutral current sensor|
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