Multi-function inductive sensing

Abstract

The invention relates to multifunctional inductive sensing. A measurement system includes an arc fault detection circuit and a second detection circuit coupled to a current transducer. By using a current transducer to provide arc fault detection and further detection capabilities, the overall circuit size can be reduced. To allow the arc fault detection circuit and the second detection circuit to provide detection of different events, the circuits may operate at different sampling frequencies.

Description

Technical Field

[0001] The present disclosure relates to electrical sensing systems, and in particular to sensing systems capable of detecting arc faults. Background Art

[0002] An arc fault is an arc of current between two contact points on a single conductor or multiple conductors. An arc fault may occur when there is a small break in a conductor, and current arcs across the break to another break in the same conductor or to a break in one or more adjacent conductors. For example, an arc fault may occur between a broken wire in a live wire and a broken wire in a neutral wire when the insulation between them deteriorates. Typically, in an alternating current (AC) household or industrial power network, arcing occurs at high potential points in the AC cycle where a large potential difference exists between the contact points.

[0003] Arc faults cause the conductor (usually copper) to heat up and further break through the surrounding insulation, which can cause an electrical fire. In some instances, when the conductor is heated to high levels, the conductive material may spit out and come into contact with the surrounding building fabric. This is especially problematic in wood or timber frame buildings. To prevent this, arc fault circuit interrupt (AFCI) systems monitor the current in the wires and attempt to determine if an arc fault is occurring. If it is determined that an arc fault is occurring or has occurred, the AFCI can stop or cut off the power supply to the wire, allowing an electrician to perform a proper diagnosis at a later time.

[0004] AFCI systems tend to be large, dedicated units that provide only AFCI functionality. This can mean that many premises do not have any means for monitoring arc faults in the power system, or may only have a single AFCI system that monitors the total supply current drawn by the premises (i.e., the current drawn by the premises from the grid). Thus, the AFCI will cut power to the entire premises if any fault is detected. Summary of the invention

[0005] The present disclosure provides an improved measurement system for detecting arc faults, combining an arc fault detection circuit and a second detection circuit that provides at least one of metering and short circuit detection. The arc fault detection circuit and the second detection circuit are both coupled to the same current transducer. By providing a system in which only a single current transducer is used to provide measurements to two or more measurement and detection circuits, the overall size and cost of the system can be reduced compared to previous systems that use independent current transducers for each measurement and detection circuit. This makes the use of AFCIs in buildings more feasible because the cost of including the function as part of a conventional measurement and / or safety device (e.g., RCD / RCCB / RCBO / circuit breaker) becomes more reasonable. In addition, because the AFCI function can use the same current sensor as other functions, it is possible to include the AFCI function in, for example, an RCD / RCCB / RCBO / circuit breaker device, each of which monitors different circuits in a house (e.g., power outlets on each floor of a house, lighting rings on each floor of a house, etc.). Including arc fault detection without providing a disconnect or circuit interruption function in smart meters and terminal equipment containing metering (such as electric vehicle charging and solar inverters) can also be used as a fault notification function to notify consumers of the risk of arc faults in their wiring networks. Therefore, it is possible to provide more sophisticated arc fault detection and protection at a relatively small additional cost and to realize a protection or interruption system in which only the faulty circuit is isolated when an arc fault is detected without affecting other well-functioning circuits.

[0006] In a first aspect of the present disclosure, a measurement system for detecting an arc fault is provided, the measurement system comprising: a current transducer for measuring a current in a current-carrying conductor; an arc fault detection circuit, the arc fault detection circuit comprising: a first analog-to-digital converter ADC having an input coupled to an output of the current transducer; a frequency analysis circuit coupled to the output of the first ADC, wherein the frequency analysis circuit is configured to detect an arc fault; and a second detection circuit comprising: a second analog-to-digital converter ADC coupled to the output of the current transducer; and a digital processor coupled to the output of the second ADC, the digital processor being configured to determine at least one of: a measure of the current in the current-carrying conductor; the presence of a short circuit; and the presence of a residual current.

[0007] The first ADC may have a first sampling rate and the second ADC may have a second sampling rate, the first sampling rate being higher than the second sampling rate. The first sampling rate may be greater than 1 Msps. The first sampling rate may be greater than 100 Msps. The current transducer may be a current rate of change sensor.

[0008] The frequency analysis circuit can detect arc faults by detecting the frequency components of the measurement current in the frequency range of 100kHz-10MHz.

[0009] The second detection circuit may further include an integrator arranged to couple the output of the current transducer to the input of the second ADC, such that the integrator integrates the signal output from the current transducer and the second ADC digitally converts the integrated signal.

[0010] The current carrying conductor may be a live conductor of a network, wherein at least one of the frequency analysis circuit and the second detection circuit is configured to receive a voltage measurement between the live conductor and a neutral conductor of the network. The frequency analysis circuit may be configured to detect an arc fault based on the voltage measurement. The digital processor may be configured to determine the power or energy consumption of the network based on the current measurement and the voltage measurement.

[0011] The measurement system may further include a circuit breaker configured to interrupt current in the first current-carrying conductor when an arc fault, a short circuit, or a residual current is detected.

[0012] The arc fault detection circuit and the second detection circuit may be packaged together in the same integrated circuit. The arc fault detection circuit and the second detection circuit may be packaged in different integrated circuits respectively.

[0013] In a second aspect of the present disclosure, a system is provided, comprising: a first circuit for coupling to an output of a current transducer, the current transducer being used to measure a current in a current-carrying conductor, the first circuit being configured to perform a frequency analysis on the output of the current transducer to detect an arc fault event based on a frequency component of the measured current in a first frequency range; and a second circuit for coupling to the output of the current transducer, the second circuit being configured to perform at least one of: current measurement; short circuit detection; residual current detection.

[0014] The first circuit may include a filter configured to bandpass filter the output of the current transducer into a first frequency range, and an analog frequency analysis system configured to produce a rectified and averaged signal of the output of the bandpass filter.

[0015] The first circuit may further include an analog-to-digital converter configured to receive an output of the analog frequency analysis system and provide a digital output; and a digital processor configured to receive the digital output from the analog-to-digital converter and detect the arc fault based on a magnitude of the digital output.

[0016] The analog frequency analysis system may also be configured to compare the rectified and averaged signal to a threshold value, wherein the threshold value is indicative of an arc fault event.

[0017] The second circuit may be configured to perform current measurement and short circuit detection based on a frequency component of the measured current within a second frequency range.

[0018] In a third aspect of the present disclosure, a system is provided, comprising: a current change rate sensor; a first circuit, the first circuit being coupled to the output of the current sensor; and a second circuit coupled to the output of the current sensor, wherein the first circuit is configured to perform at least one detection function, and the second circuit is configured to perform at least one detection function different from the detection function performed by the first circuit, and wherein the detection functions include: arc fault detection; short circuit detection; current measurement; residual current detection.

[0019] The current change rate sensor may be a Rogowski coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Various aspects of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:

[0021] Figure 1 is a current plot during an arc fault event;

[0022] Figure 2 It shows the information that may be contained in different frequency components of an electric power network;

[0023] Figure 3 is a first schematic diagram of a measurement system for detecting arc fault events according to one aspect of the present disclosure;

[0024] Figure 4 is a second schematic diagram of a measurement system for detecting arc fault events according to another aspect of the present disclosure;

[0025] Figure 5 is a second schematic diagram of a measurement system for detecting arc fault events according to another aspect of the present disclosure;

[0026] Figure 6 is a second schematic diagram of a measurement system for detecting arc fault events according to another aspect of the present disclosure;

[0027] Figure 7a a first circuit board layout for a measurement system;

[0028] Figure 7b a second circuit board layout for the measurement system;

[0029] Figure 7cThird board layout for the measurement system. DETAILED DESCRIPTION

[0030] Known arc fault detection and arc fault circuit interruption (AFCI) systems typically require dedicated current sensors and large packaging, which reduces their usability in space-constrained metering units or circuit breakers. The system size can be reduced by providing a system in which a single current sensor is coupled to multiple detection circuits, such as an arc fault detection circuit and a second detection circuit that provides other functions. This can allow more grid analysis and protection functions to be provided in a smaller space and reduce the cost of the system through strategic reuse of certain components. Each detection circuit can consider different frequency components of the current being measured to provide detection of different events, such as arc faults, short circuits and / or meters to monitor consumption. Metering and fault detection circuits may also need to measure voltage in the same frequency range as current monitoring.

[0031] Figure 1 A graph of the current drawn by the grid during an arc fault event is shown. In an AC system, the current drawn by the grid alternates, however for short periods of time, during normal operation, the current draw can be considered to be substantially constant, or flat. Figure 1 Regions 102 and 106 show a substantially constant current draw for a short period of time, indicating normal operation of the grid. In an arc fault event, current arcs between two contact points of a single conductor or multiple conductors, essentially jumping between those contact points. Figure 1 The current drawn in an arc fault event shown in area 104 is much greater than during normal operation. Arc fault events may last for a very short time and include very high frequency oscillations, for example, an arc fault may only occur at the highest potential point in the AC cycle. Measuring the voltage across the phase and neutral points of the power grid can be used to determine the potential when the current event 104 occurs and to help determine the arc fault. Arc faults may cause high frequency current peaks that include very high frequencies. Arc faults are characterized by the energy they contain between >lMHz, >5MHz, >10MHz and <50MHz, <20MHz, <10MHz, <5MHz. For example, arc faults may be characterized by the energy they contain in the frequency range of lMHz-50Mhz, lMHz-20MHz, 1MHz-10MHz, lMHz-5MHz, such as Figure 2, as shown in range 206. Such high currents can cause the insulation surrounding the conductors in the grid to heat up and further degrade. As a result, arc faults in their initial formation often appear to be intermittent relative to the line sequence, which helps to separate them from other high frequency conventional noise sources (such as dimming circuits, motor brushes or drive electronics, AC-DC converters, etc.) whose noise signatures are relatively periodic and stable.

[0032] Figure 1 The high frequency current draw 104 shown in may indicate a parallel arc fault event. Parallel arc fault events occur due to, for example, a bridging between a live conductor and a neutral conductor of a power grid. Therefore, they may occur briefly at a high voltage point in the AC cycle. Due to the large current draw in parallel arc faults, parallel arc faults may be considered more dangerous, resulting in a higher probability of damage to surrounding materials and a higher probability of fire. Series arc fault events may also occur, such as through an air gap of a single conductor, where the current jumps along the single conductor through the air gap. Compared to parallel arc faults, series arc faults have limited maximum current draw because they are limited to the load current drawn by the load connected to the system. Series arc faults can be detected by drawing changes in the waveform of the current, such as the current drawn in an AC system can be non-sinusoidal. Therefore, series arc faults can be detected by considering lower frequency components than parallel arc faults.

[0033] Short circuits can also occur in the electrical network. A short circuit differs from an arc fault in that it involves a physical breaking of the current between two electrical contacts. Short circuits occur over a longer period of time than arc faults because the physical short allows the current to flow more easily, meaning they can be low frequency events occurring during the AC cycle. A short circuit can occur at any point in the main cycle. Once a short circuit occurs, its characteristics are usually relatively ohmic or resistive, tracking the voltage on the line, so a short circuit contains lower frequency content than an arc fault event, such as Figure 2 As shown in the figure 204.

[0034] A similar event that requires protection is overcurrent protection, for example, when a device on a line circuit draws more current than the safe current draw for that line or circuit. This could be because too many devices are connected to the circuit, one or more of them are heavily loaded, or one or more of them are faulty, causing a change in efficiency. In this case, the role of the circuit breaker is to trip to protect the wires and grid above and below it. However, while the circuit breaker needs to trip when a real problem occurs, it does not need to trip if the event is a false positive. This means that when the current level measured by the circuit breaker is just below or above the overcurrent level, several ms or even half a line cycle, full line cycle or multiple line cycles need to be analyzed to distinguish between events that will not cause damage or require interruption, such as emergency current plugging or starting equipment.

[0035] The response to a short circuit can be a function of the magnitude of the current. For example, when the short-circuit current is large, but the grid is energized and the potential of the neutral is low, the short-circuit protection circuit needs to respond quickly to protect the line, circuit, and switch, respond faster than other upstream circuit breakers, cause the circuit breaker closest to the fault to trip first, be easy to identify and rectify, and avoid affecting other circuits that are not faulty. Therefore, the measurement of any current used for short-circuit protection also needs to be fast and have low latency. When a circuit breaker needs to respond very quickly is when it is just closing, usually at the potential zero point. As the potential builds to its peak at 90 degrees of the fundamental frequency, if there is a hard short circuit, the current will build up just as fast. For example, if the short circuit is <1 ohm, it may only take a few 10s us to reach a few 10s Amps. If the circuit breaker delays in opening the circuit, the maximum current may be 100s Amps in a few ms. The desired requirements for short-circuit detection can be in the range of <10 us, <50 us, <100 us, <500 us, <1 ms. In these cases, the sensing and measurement bandwidth needs to be in the range of 10s kHz, 100s kHz, or even up to a few MHz. It is important to know the potential phase relative to the current and the state of the switches in the circuit breaker. For example, a short circuit can be detected by considering the frequency components in the range of 10 kHz - 100 kHz, 10 kHz - 500 Hz, or 10 kHz - 1 MHz.

[0036] In addition, residual current may exist in the grid, indicating a current leakage within the grid. By detecting the difference between the currents in the live wire and the neutral wire of the grid, the residual current can be detected at a relatively low frequency. The differential current detected for this protection can be as low as a few milliamps, and when the current is greater than a few tens of milliamps, the system may need to be able to respond within a few milliseconds. The residual current is relatively low compared to the total current carried on the live and neutral conductors, which may be in the range of 10s Amps. Therefore, the preferred detector for this application is a magnetic current transformer through which the live and neutral conductors pass, although other technologies involving gating devices are used, and it is desirable to avoid direct current, otherwise it may saturate the core of the current transformer. Residual current detection techniques can measure the currents on the neutral and live / phase separately and then calculate the difference, usually learning or calibrating the mismatches in the measurements to make the measurement accuracy meet the requirements in mA. In both of these sensing modes, the bandwidth is less than 10 kHz, and the decision-making process is greater than ms, for example, between 0 kHz - 10 kHz, 10 Hz - 10 kHz, 50 Hz - 10 kHz, 10 Hz - 20 kHz. The residual current detector also incorporates a circuit breaker function to open the circuit in case of overcurrent or short circuit. Therefore, in addition to the differential sensor, it only contains sensors for the phase or neutral.

[0037] Due to the potential fire risks associated with arc faults and short circuits, as well as the dangers of residual or leakage current, it may be important to provide accurate and reliable detection of these events. In some cases, it may be necessary or advisable to be able to detect and prevent arc faults and short circuits on a given wiring circuit in a home, such as a bathroom. In addition, the system can disconnect the current to prevent the arc fault, short circuit, residual current or overcurrent event from continuing.

[0038] Both domestic and industrial power grids can be provided with electrical metering units, allowing the total current drawn on the premises to be determined, thereby calculating energy consumption for billing purposes. Conventional systems provide separate units for metering and each safety function, such as an arc fault circuit interrupter (AFCI) unit (or just an arc fault detection unit), a short circuit detection unit, a residual current device or residual current circuit breaker, and a metering or electrical metering unit. This results in duplicated components, greater space requirements and costs.

[0039] Figure 2An example of a frequency domain representation of a measured current signal when an arc fault occurs is shown. Most measured current signals are likely to be in a relatively low frequency range, typically at or around the fundamental frequency of the AC network (typically between 50-60Hz). Therefore, for electrical metering, it is important to consider low frequency current draw 202, particularly current drawn at the fundamental frequency of the grid and low harmonics of the fundamental frequency. For example, the metering system may consider current drawn between 10Hz-lOkHz, the fundamental frequency of the grid and 10kHz, or between the fundamental frequency and the 20th harmonic, or the 50th harmonic, or the 100th harmonic. This range can be extended below the fundamental frequency of the power network, at least because the frequency at which the network operates may drift over time. Current measurements can be made with voltage measurements to create a measure of the power used, as well as the nature of the power and whether it is active or reactive. This is also used to generate a measure of the energy consumed. The meter may have to measure current consumption up to 200A with an accuracy better than 0.1%, while also being able to measure consumption down to 10s of mAs with an accuracy of <0.5%. These requirements are often outlined in standards such as IEC62053 and ANSI C12.20. Due to this large dynamic range, metering systems most often use oversampling converters (sigma delta) that sample in the Msps range and provide output data rates and analog bandwidths in the Ksps and KHz range. These sampling converters have a delay of many clock cycles from their sinusoidal filters at this rate. A key criterion for billing current measurements is the stability of the measurement over environmental and lifetime conditions, for example, stability criteria may be in the range of <1%, <0.5%, <0.1%. In contrast, for fault detection such as arc fault or short circuit detection, stability criteria may be in the range of >1%, >5%, >10%. For energy measurements for EMI billing, there are additional difficult criteria that also go beyond those for fault detection circuits, such as immunity to strong external AC and DC magnetic fields, with only a few tenths of a percent effect, and immunity to high frequency conduction currents from switching circuits.

[0040] Metering devices can also detect when and how much appliances and devices of the type connected consume by analyzing them during the line cycle and non-intrusive load monitoring during the day, week, month and year. All this information is useful for consumers to track and optimize their electricity consumption. The greater the granularity of measurement in the network, such as at each branch within the junction box, the more likely it is that users will be able to track and optimize their consumption. However, in order to achieve this, the cost and space required for metering measurements need to be effectively incorporated into the primary circuit breaking and fault detection functions.

[0041] When a short circuit is present in the circuit, the current being measured may include significant content at a frequency (or frequencies) above the metering frequency range, or may require a detection delay that is lower than the sampling rate and delay used in the metering system. The short circuit protection system may be allowed more time to determine overcurrent events that are closer to the threshold than larger events, in which case the frequencies involved may include the metering range.

[0042] Thus, to determine a short circuit, the system may consider frequency components of the measured current within the mid-frequency range 204 of the measured current signal. For example, current draw between 10kHz-100kHz may indicate the presence of a short circuit or overcurrent event. The frequency ranges of interest for short circuit detection may be between 5kHz-100kHz, 10kHz-200kHz, 10kHz-500kHz. Short circuit detection may be further enhanced by considering current draws within a wider range 208, such as by considering frequencies in the metering range 202 and a specific short circuit detection frequency range 204, such as currents within a 10-10kHz frequency range may indicate a short circuit or overcurrent event. The bandwidth of the short circuit detection system may sometimes need to be in the 100s KHz or low MHz range to adequately protect a network or switch, such as a solid-state switch of a silicon carbide switch, for example, 10Hz-1MHz, 100Hz-1MHz, 1kHz-1MHz, 1kHz-500kHz.

[0043] In contrast, as described above, parallel arc-fault events typically occur very quickly over a short period of time. Therefore, signal components within the measured current draw range associated with an arc fault may be within a relatively high frequency range 206. For example, current draws at frequencies greater than 1 MHz, between 1 MHz-10 MHz, or between frequencies > 20 MHz may indicate an arc fault event. In contrast, a series arc fault may be determined by considering a lower frequency range, such as considering the frequency range 202 for metering or considering the frequency range 204 for short circuit detection.

[0044] By taking into account the different frequency components of the drawn current, the measurement system can provide metering and / or short circuit detection and interruption, as well as arc fault detection and optional interruption. Advantageously, this may allow the system to provide these functions in a single package.

[0045] Figure 3 A measurement system 300 is shown comprising both a first circuit 302 and a second circuit 304. The first circuit 302 provides arc fault detection functionality, while the second circuit 304 provides metering and / or short circuit detection functionality and / or residual current detection and / or overcurrent detection.

[0046] The measurement system 300 includes a current transformer 306 configured to measure the current of a current carrying conductor 322 passing through a circuit or network. The circuit or network may include a first current carrying conductor 322 and a neutral conductor 324. Although this represents a single-phase system, it is clear that the techniques described herein are applicable to three-phase systems including three phase conductors and a neutral conductor, or other types of power grids. The current transformer can be a rate of change current sensor, which is a current sensor that responds to a changing current in a current carrying conductor so that the output of the current sensor is proportional to the rate of change of the current or di / dt. Therefore, the rate of change of the current sensor can be referred to as a di / dt current sensor. The rate of change of current sensors provides a good high frequency response because their measurement gain increases with the signal frequency, which may provide a better signal-to-noise ratio for higher frequency signals. Since arc fault events are high frequency events (~lMHz), the improved signal-to-noise ratio of the high frequency rate of change of the current sensor can enable more accurate detection of arc faults using the rate of change of the current sensor to measure the signal. For example, the rate of change of the current sensor can be an air core current sensor, such as a Rogowski coil. Such a di / dt sensor can be implemented on a PCB or wrapped around a structure. PCB-based coils have the advantages of high cost and regular structure, but their signal size is small and require special winding topology to reject external magnetic fields.

[0047] Rate of change current sensors are more challenging to use for metrology because their fundamental frequency response and small signal size mean that analog integration requires the associated issues of increased noise and drift from large resistors and capacitors often used for analog integration. If digital integration is used, the signal bandwidth is limited to a few kHz by analog means to maintain the amount of dynamic range required in the amplification and digitization prior to the digital integrator to avoid clipping which will introduce rectification and large errors to the integrated current, in which case the current draw at higher frequencies, such as 20kHz may be lost.

[0048] Other current sensors or current transducers may also be used when the rate of change of the current sensor provides an additional high frequency signal, such as a current transformer (CT) or current shunt or a Hall effect or other magnetic field sensor.

[0049] The first circuit 302, or arc fault detection circuit, is configured to perform frequency analysis on the output of the current converter 306 to determine the occurrence of an arc fault event. The first circuit 302 optionally includes a first matching network 308 configured to match the impedance of the current converter 306 to prevent or reduce signal reflections. A skilled person will readily understand how to implement such a matching network, and therefore, this will not be further described in this disclosure. The path may also include a buffer 326 to separate the arc fault detection circuit 302 from the current converter 320, for example, to separate any reliance on the operation of the first circuit 302 from the operation of the second circuit 304. For example, if the detection mechanism includes a switching stage or a hybrid stage, the buffer 326 will prevent charge from being kicked back. The buffer stage 326 may include gain elements and / or filtering elements to further pre-stage the arc fault signal of interest. When the buffer 326 is shown as coupled to the output of the matching network, it may be alternatively positioned before the matching network 308. Alternatively, the buffer 326 may be external to the first circuit 302, for example, coupled to the input of the first circuit 302. Matching network 308, buffer 326, and filter 330 may be implemented using a single circuit or separate circuits. Additionally, these circuits may not be included, or only a subset of these circuits may be included.

[0050] The first circuit 302 also includes a first analog-to-digital converter (ADC) 310 and a frequency analysis circuit 312. The frequency analysis circuit 312 may be a digital processor. The first ADC 310 may be any suitable type of ADC, such as a flash ADC, a SAR ADC, a pipelined ADC, etc. The first ADC 310 converts the analog output of the current transducer 306 into a digital signal and provides it to the frequency analysis circuit 312. The frequency analysis circuit 312 is configured to monitor the occurrence of arc faults in the power grid. For example, the frequency analysis circuit 312 may monitor the frequency components of the measured current in the 5 MHz-20 MHz range or the range 206 of the measured current, wherein if the amplitude / intensity / amplitude of the component in the monitored frequency range exceeds a threshold amount (e.g., a threshold amount set to avoid normal signals in the frequency range from being interpreted as arc faults), then an arc fault is detected. The threshold may be set to any suitable value depending on the characteristics of the measurement system 300 and / or the characteristics of the circuit being monitored. The system may use a digital bandpass filter to determine the energy in a band, or use a more granular frequency analysis technique, such as performing a Fast Fourier Transform (FFT), to determine the energy in multiple frequency "bins."

[0051] As previously described, there may also be a measurement of the line voltage provided by the voltage measurement device 328. The frequency analysis system 312 may monitor energy within a frequency band of interest occurring simultaneously within a voltage cycle of the AC system, for example, energy representative of an arc fault occurring within an AC cycle and / or energy representative of an arc fault occurring within multiple cycles. This may reduce the likelihood of false alarms / false detections of arc fault events. For example, arc faults may be detected by detecting intermittent high frequency current draws relative to the line sequence. This ensures that the system is able to determine the difference between an arc fault and other regular high frequency noise with relatively stable noise characteristics.

[0052] The first ADC 310 may be configured or selected to have a relatively high sampling rate that is capable of providing adequate definition of the frequency components of the drawn current that are relevant to arc fault detection. For example, the sampling rate of the first ADC 310 may be greater than 1Msps, or greater than 10Msps, or greater than 100Msps. As previously described, the frequencies of interest for arc fault detection may be between Figure 2 206. The optional filter 330 can be configured to bandwidth limit the signal received from the current transducer 306 or the optional buffer 326 and / or the matching network 308. The ADC 310 can then sample at a frequency range greater than the band of interest 206 or at a sampling rate greater than several times. Digital filtering can then be used following the ADC to extract the signal of interest.

[0053] The filter 330 may also provide an anti-aliasing function depending on the type of ADC 310 coupled to the output of the filter 330. Alternatively, the anti-aliasing function may be implemented by the buffer 326 or the matching network 308.

[0054] If analog filtering 330 is included before the ADC 310 to perform analog bandpass or bandlimiting of the frequency components of interest 206, the ADC 310 can be configured to undersample the frequency band of interest 206, with a sampling rate lower than the frequency band of interest 206. This is possible when the sampling bandwidth of the ADC is greater than its conversion frequency, because such energy will be folded below the frequency of the frequency band of interest 206 and still be captured by the ADC. Undersampling in this manner may reduce the power consumption and requirements of the ADC. Likewise, the ADC can have a sampling bandwidth within the frequency band of interest 206.

[0055] The current sensor 306 may be a di / dt or rate of change current sensor. This type of current sensor 306 benefits from an output that is proportional to the frequency of the signal being measured - therefore, it can be considered a form of a high pass filter at the system level. Therefore, the band pass filter implemented by the filter 330 may be implemented using two low pass filters to reduce cost and circuit complexity. For example, the first low pass filter may have a corner frequency at the lowest frequency of the frequency range of interest 206 for arc fault detection, and the second low pass filter may have a corner frequency at the highest frequency of the frequency range of interest 206 for arc fault detection. In this way, the combined response of the di / dt sensor and the two low pass filters approximates a band pass filter centered on the frequency range 206 suitable for arc fault detection. For example, the filter 330 may implement an analog low pass filter of 5 MHz and then another analog low pass filter of 15 MHz, resulting in a low cost first order band pass filter that may be formed prior to the ADC to form the signal of interest. These filters may be passive or active. Although the filter 330 is shown as a separate element, it may be part of the buffer 326 and / or the matching network 308 if such elements are present.

[0056] Although Figure 3 The system includes an analog-to-digital converter 310 and a digital frequency analysis system 312, but it can also be configured to provide analog detection or analog processing of arc fault events before digitally detecting arc fault events, such as Figure 4 shown.

[0057] For example, Figure 4 A system including an analog frequency analysis system 414 is shown. Matching network 308, buffer 326, and filter 330 are optional components that can be used in accordance with Figure 4 Filter 330 can receive the output from current sensor 306 and a bandpass filter. For example, filter 330 can approximate a bandpass filter centered around a frequency range 206 suitable for arc fault detection, or a frequency range 206 of interest for arc fault detection. By bandpass filtering, the output of the filter only contains signals within a frequency band relevant to arc fault detection.

[0058] The output of the filter 330 inputs the analog signal to an analog frequency analysis system or circuit 410. The analog frequency analysis system 410 may perform operations on the received signal to create an output signal representing the energy contained in the current component in the frequency range of interest 206 for arc fault detection. This may produce a signal that represents the energy received at the input within the target frequency band 206. The analog frequency analysis system 412 may further or alternatively provide peak detection or RMS estimation to its received input.

[0059] For example, analog frequency analysis system 414 may rectify and average received signals passed by filter 330 to provide a signal indicative of energy contained in current components within frequency range of interest 206 for arc fault detection. Other methods of providing a signal indicative of energy within a frequency range may be used.

[0060] System 414 can compare the rectified and / or averaged signal to a threshold value indicating the occurrence of an arc fault. For example, the analog frequency analysis system can include a variable threshold value that is set at the time of manufacture to represent an arc fault indication level. If the rectified and / or averaged signal is greater than the threshold value, an arc fault may be detected.

[0061] This analog approach may be more energy efficient, while the digital approach may allow for more sophisticated evaluation of arc fault waveforms through machine learning and other advanced signal recognition beyond just energy measurement.

[0062] Although the arc fault detection system 402 can be a completely analog arc fault detection system, it can further or alternatively include an ADC 410 and a digital processor 412. As described above, the analog frequency analysis system 414 can generate a signal that indicates arc fault detection within the energy 326 within the frequency band of interest. The signal can be provided to the analog-to-digital converter 410, which converts the analog signal to a digital signal. The digital signal can be provided to the digital processor 412. The digital processor can determine the presence of an arc fault event based on the magnitude of the signal indicating the energy within the frequency band of interest.

[0063] Because the system operates to provide a simplified signal to the digital processor 412, the digital processor 412 does not need to perform any complex frequency analysis, such as a fast Fourier transform. Instead, the digital processor 412 can determine the presence of an arc fault based on changes in the received signal representing energy within the frequency band of interest. For example, the digital processor can monitor the received signal over time and determine the presence of an arc fault event based on rapid changes in energy within the frequency band of interest 206, such as changes compared to an average value of the energy over a period of time. In addition, the digital processor can receive measurements of the phase voltage from the voltage measurement device 328 (the voltage between the live conductor 322 and the neutral conductor 324 being tested). The digital processor 412 can determine the presence of an arc fault based on a representative signal of energy in the arc fault frequency band 206 and the voltage between the conductors, such as based on the energy within the frequency band of interest 206 compared to the portion of the AC voltage cycle in which the energy network current is located.

[0064] The second circuit 304, or second detection circuit, is configured to perform at least one of current measurement, short circuit detection, residual current detection, and overcurrent protection. The second circuit 304 may also provide series arc fault detection by considering low frequency components.

[0065] The second circuit 304 includes a second ADC 316 and a digital processor 318. The second ADC 316 may be any suitable type of ADC, such as a SAR ADC, a sigma delta ADC, a pipeline ADC, etc. The second ADC 316 converts the analog output of the current transducer 306 into a digital signal and provides it to the digital processor 318. The digital processor 318 may be configured to determine the current drawn by the electrical network measured by the current transducer 306, and more specifically the current drawn by the current carrying conductor 322 of the electrical network measured by the current transducer 306. Alternatively, or in addition, in addition to determining the current, power, and energy, the digital processor 318 may determine a short circuit or overcurrent event in the electrical network or the current carrying conductor.

[0066] like Figure 2 As shown, the current component associated with short circuit or current measurement is lower in frequency range than the current component associated with arc fault detection. Therefore, the second ADC 316 may have a lower sampling rate than the first ADC 310, allowing the second ADC 316 to trade off bandwidth with the dynamic range and stability required by the metering application, so it may also be a lower cost and complexity component, which may further allow the circuit space required for the second ADC 316 to be reduced. By providing separate first and second ADCs, specific stability, bandwidth and accuracy requirements of different applications can be met, thereby reducing the cost of implementing the system as a single ADC that can meet all requirements. However, the system can be replaced with a single ADC in place of the first ADC and the second ADC. The most common one that provides dynamic range is the sigma delta ADC, which, although it oversamples the input at a higher rate, has a much lower output word rate. For example, the second ADC 316 may have a sampling rate of 16ksps, 32ksps, 64ksps, or 100ksps.

[0067] The second detection circuit 304 may include a second matching network 314 configured to match the impedance of the second circuit 304 to the current converter 306, thereby preventing or reducing signal reflections. A skilled person will readily understand how to implement such a matching network, and therefore, this will not be further described in this disclosure.

[0068] The second circuit may have gain and filtering before digitization, since the signal from the current converter 306 can be very small and needs to be resilient to high frequency transients. The full scale signal of the PCB di / dt sensor at 50Hz fundamental may be as low as ImV RMS and even a 200A signal needs to be unsaturated with fast edges of a few Amps / us that may produce a step of several hundred mV for the same sensor. The di / dt sensor needs to be integrated to get a flat frequency response energy measurement containing the fundamental frequency (usually 50 or 60 Hz) and multiple harmonics, such as 11, 25, 50, 100 harmonics, typically at 5-10Hz-10kHz. This integration can be done in the analog domain, such as by an integrator / low pass filter 314, but at the expense of noise and drift, or in the digital domain, but this requires managing the dynamic range under fast transients to avoid causing clipping that may result in erroneous power due to rectification. The signal may also need to be high pass filtered to avoid accumulation of offset in the integration. The high-pass filter should not be too close to the fundamental frequency, or it will introduce unacceptable phase or gain errors when the fundamental frequency is offset by several %, for example, the corner frequency of the high-pass filter should be 10kHz, 20kHz or 50kHz.

[0069] The second circuit 304 optionally includes an integrator or a band-limited low-pass filter 314 on top of an anti-aliasing filter to handle the di / dt sensor. In the case of a digital integrator solution, due to the reduced gain of the low-pass filter 314 at high signal frequencies, the low-pass 314 can be used to prevent high di / dt current pulses from passing to the second ADC 316 and digital processor 318. This helps prevent signal saturation at the ADC 316 or any amplifier in the signal path.

[0070] In addition to determining the current in conductor 322, digital processor 318 may also provide power and energy calculations. Digital processor 318 may receive voltage measurements on live 322 and neutral 324 conductors from voltage measurement device 328 to calculate power and / or energy measurements.

[0071] Figure 3 The system 300 in FIG. 3 includes a first circuit 302 and a second circuit 304 , both of which obtain the output of a current converter 306 from a node 320 . Figure 5 It shows a similar Figure 3 and Figure 4 measurement system, with like reference numbers associated with like components. Figure 3 and Figure 4 The description is also Figure 5 For example, Figure 5 The first and second circuits may include Figure 3 and Figure 4 Any components shown in the first and second circuits.

[0072] exist Figure 5 In the embodiment, the measurement system 400 includes a first circuit 502 and a second circuit 504. The first circuit 502 is configured to perform a frequency analysis on the output of the current transducer 306 to determine the occurrence of an arc-fault event, such as Figure 3 The second circuit 504 is configured to perform current measurement and / or short circuit detection.

[0073] Figure 5 The integrator / low pass filter 514 in may be an RC filter including a first resistor and a second resistor connected in series, with a first capacitor coupled to the first resistor and a ground node or a reference voltage node.

[0074] The first circuit 502 is coupled to the current transducer 306 through or after a low pass filter 520 of the second circuit 504. The low pass filter 520 may have a corner frequency for arc fault detection set above the frequency range of interest 206. In this way, both the first and second circuits are protected from very high frequency signals. The first circuit may have a second filter 514 having a corner frequency lower than the corner frequency of the first filter 520. By coupling the first circuit 502 or the first ADC 310 to the current transducer 306 in this manner, the first circuit 502 may be protected from very large di / dt signals, which may be measured by the current transducer 306. It will be appreciated that the filter may be implemented in many different ways, for example, as a component around an amplifier that may provide gain and bandwidth control to the system. The filter 514 can limit the signal from the sensor so that the ADC 316 does not respond to it, but if it is set below the frequency range of interest associated with the current measurement, when the fundamental is 50 Hz, especially when the current sensor 306 is a rate of change current sensor, it can also perform analog integration at 5 Hz to flatten the rate of change of the current sensor frequency response through the integrator / low pass filter 514. Compared to a rate of change sensor system that uses a digital integrator after the ADC to flatten the response, this low pass filter performs the task of limiting the bandwidth and response of the sensor above the frequency of interest, usually above the 10th harmonic.

[0075] Both the first circuit 502 and the second circuit 504 may be protected from very high frequency noise, such as radio frequency noise, by providing a first low pass filter 520. The second low pass filter acts only to filter the signal provided to the ADC 316 and may therefore have a much lower corner frequency suitable for metrology.

[0076] The filter 520 can be implemented as an RC low pass filter. For example, the low pass filter 520 can be formed by discrete resistors and discrete capacitors. Alternatively, if the current sensor 306 is a Rogowski coil, the low pass filter can be formed by the trace resistance of the Rogowski coil and a discrete capacitor coupled to the output of the Rogowski coil, allowing the use of fewer components.

[0077] Any suitable type of low pass filter / integrator may be used. The first circuit may be coupled to the current sensor after the low pass filter. The low pass filter may be implemented as part of a gain stage in an input or feedback network.

[0078] The short circuit detection function can use information from two paths, so that it receives information about the first circuit and the second circuit related to the current draw over a wide frequency range 208. For example, Figure 6 A system 600 is shown that includes a first circuit 602, a second circuit 604, and a short circuit detection system 608. The first circuit 602 may be configured as described with respect to Figure 3-5 The first circuit 302, 402, 502 in the embodiment of the present invention operates in the manner described above and provides a signal indicating the high frequency current component within the range 206 to the short circuit detection circuit 608. The second circuit 604 can be used in a manner related to Figure 3-52 and 204. The first circuit 602 and the second circuit 604 operate in the manner described above and provide a signal to 608 of the short circuit detection circuit 608 indicative of a low frequency current component within the range 202 and / or 204. Therefore, these circuits are not described in detail herein. In this manner, the first circuit 602 provides a high frequency analysis of the current in the current carrying conductor 322 suitable for arc fault detection, while the second circuit 604 provides a low frequency analysis (relative to the high frequency analysis of the first circuit) of the current in the current carrying conductor 322 suitable for current measurement and metering. Under marginal overcurrent conditions (i.e., the short circuit is a relatively high ohmic resistance), the system will need to operate with the accuracy of the lower bandwidth metering path 604 and will consider the signal decision to detect the short circuit for a longer time, which path may use a sigma delta or oversampled SAR ADC, which have relatively long delays and sampling rates of 10ksps, 20ksps or 100ksps after filtering. To detect high current short circuits, especially when there is a delay critical response time, such as when the circuit breaker is reset and the short circuit is still present, the short circuit detection system 608 may need to use information from the high speed path 602 for AFCI detection by taking into account the high frequency component 206. For delay critical applications, the processing after the ADC in the first circuit 602 may need to be supplemented with an additional path to provide the required detection bandwidth in the range of 10 Hz to 100 kHz, rather than in the range of several MHz. For example, the stream from the high frequency ADC can go to a separate digital integrator and high pass low pass filter, rather than to the stream for AFCI detection.

[0079] Alternatively, or in addition, the short circuit detection circuit may be coupled directly to the current sensor. Where the short circuit detection system 608 receives a dedicated input from the current converter 306, the short circuit detection system 608 may include its own dedicated analog adaptive and ADC or threshold comparator for low latency high current short circuit determination. The system (dedicated path from the current breaker 306 to the short circuit detection circuit 608 and their respective components) is only active after the circuit breaker is tripped and reset, thereby reducing the overall power requirements of the system

[0080] As previously described, the first circuit 602, the second circuit 604, and the short circuit detection system 608 may include inputs for receiving voltage measurements of phase voltages. This enables these circuits to determine the event phase for short circuit detection and arc fault detection and determine whether an interruption is required or whether an event notification needs to be sent somewhere.

[0081] These functions can be integrated into a system with residual current detection to provide a combined device where some of the functions can share resources with residual current detection, for example there can be separate measurements of the current in the live and neutral conductors to determine the delta current which can share resources with the metering measurement path. For example, the current measurement in one conductor (e.g. the live conductor) can be determined by Figure 3-5 The current measurement system for any one of the live conductors may be performed by a current measurement system, while the current in the second or neutral conductor may be performed by a separate current measurement system. Alternatively, the system may determine the current in the first conductor and provide it to a separate residual current detection device, or a residual current circuit breaker device (RCCB). The residual current circuit breaker may include a standard device for determining residual current, such as a transformer surrounding the live conductor and the neutral conductor. The residual current circuit breaker may determine whether to open the circuit based on the residual current detected by the transformer and the current measured by the measurement circuit.

[0082] By using a single current transducer 306 to measure the current, the output of which is used to provide arc fault detection and short circuit and / or metering and / or residual current functions, the physical size and cost of the system can be greatly reduced compared to providing dedicated systems for each arc fault detection, short circuit function, residual current function and metering function. This can allow the system 300, 400 to be installed to monitor the current associated with a smaller power grid, for example, more systems will fit into the same size electrical metering or safety unit. For example, the system can be installed in the circuit breaker, providing one system per circuit within the premise. In a home or domestic power grid, a single system can provide arc fault detection and metering and / or short circuit detection and / or residual current detection for a single room or single circuit (such as a lighting ring for a part of the house or floor, or a power socket ring for another part of the house or floor). Therefore, a consumer unit with multiple RCDs or circuit breakers can include arc fault detection functionality in each RCD or circuit breaker. This further allows greater granularity to be provided to electricians at the fault location compared to only providing arc fault detection for the entire electrical network. Additionally, the arc fault detection circuit may be part of an arc fault circuit interrupter (AFCI) configured to disconnect power to a faulty circuit when an arc fault is detected while leaving other circuits unaffected.

[0083] When based on Figure 3-6 When the detection system of any of the figures is included in a circuit breaker, the circuit breaker can be operated to trip or disconnect from the power grid when at least one of an arc fault, a short circuit, a residual current or an overcurrent is detected.

[0084] according to Figure 3 and Figure 4The described measurement systems both include a first circuit 302, 402 and a second circuit 304, 404. The packaging of these circuits may provide different advantages for the overall measurement system in terms of measurement accuracy, space requirements, component requirements, replaceability, and so on.

[0085] The first circuit 302, 402 and the second circuit 304, 404 may be packaged separately, for example, in separate integrated circuits. By packaging the circuits separately, the second circuit 304, 404 may be closer to the current transducer than the first circuit 302, 402, reducing the effect of external magnetic field coupling to the first circuit by reducing the routing length. Since the second circuit provides a metering function, external magnetic field coupling has a significant effect on the accuracy of current measurement. In contrast, the arc fault detection circuit is arranged to provide an indication of the presence or absence of an arc fault, and therefore, it is acceptable to have a larger external magnetic field coupled into the circuit than the metering circuit.

[0086] Where the packages are separated, the first circuit 302, 402 and the second circuit 304, 404 may be located on separate printed circuit boards, or on different sides of the same circuit board. Figure 7a As shown, the first integrated circuit 702 can provide the functionality of the first circuit 302, 402, and the second integrated circuit 504 can provide the functionality of the second circuit 304, 404. The first circuit and the second circuit can be arranged on the same side of a printed circuit board 706 and coupled to the printed circuit board 706. The printed circuit board 706 can include a printed circuit board-implemented rate of change current sensor, for example, a Rogowski coil implemented as a PCB of the current converter 306, 406. Alternatively, as Figure 7b As shown, the first integrated circuit 702 and the second integrated circuit 704 can be located on opposite sides of a printed circuit board 706. By providing the packages on different sides of the same circuit board, the conductive traces on the printed circuit board 706 can be positioned to provide a certain amount of field cancellation and further ensure that the two packages are only located a short distance from the current transducer.

[0087] The first circuit 302, 402 and the second circuit 304, 404 may be packaged together, or packaged in a single integrated circuit. Packaging these circuits together may reduce the size of the entire system, making it occupy a smaller space. For example, Figure 7cAs shown, a single integrated circuit 708 can provide the functionality of both the first circuit 302, 402 and the second circuit 304, 404. The integrated circuit 708 can be coupled to a printed circuit board, which, as described above, can optionally include a printed circuit board-implemented current transducer, such as a PCB-implemented Rogowski coil. Co-packaging can allow for a reduction in routing length between the current transducer 306 and the frequency analysis / digital processor circuit 302, 402, thereby reducing the effects of external magnetic field coupling. Such co-packaged circuits can provide improved reduction of external magnetic field coupling for metering circuits and arc fault circuits.

[0088] The first circuit 302, 402 and the second circuit 304, 404 may be packaged alternately so that analog components (components that process signals in the analog domain) and digital components (components that process signals in the digital domain) are packaged separately. Existing ADCs may be included in an analog package or a digital package. For example, the system may include a first analog chip that includes all analog processing components from the first circuit 302, 402 and the second circuit 304, 404. The system may also include a digital chip that includes all digital processing components from the first circuit 302, 402 and the second circuit 304, 404. For example, the analog chip may include a Figure 3 The digital chip may include components 308, 326, 320, 314 of the first and second circuits. Figure 3 The components 312 and 318 of the first and second circuits. The ADCs 310, 316 may be included on an analog chip or a digital chip. This may allow a simpler manufacturing process to be used.

[0089] Although the above system includes an arc fault detection circuit and a second detection circuit, the system may also include a first functional circuit and a second functional circuit coupled to the current sensor. The first functional circuit and the second functional circuit may be configured to have different functions, such as: current measurement, arc fault detection, short circuit detection, residual current detection, residual current circuit breaking. Since the first functional circuit and the second functional circuit are coupled to the same current transducer, the system may be provided in a smaller space, or more functions may be provided in the same space.

[0090] If the current transducer is a Rogowski coil, the Rogowski coil may be a printed circuit board implementing the Rogowski coil, provided on the same printed circuit board as the first circuit and the second circuit. Alternatively, the Rogowski coil may be a conventional Rogowski coil, which is not provided on a printed circuit board. The conventional Rogowski coil may then be coupled to the first circuit and the second circuit in any suitable manner. Alternatively, the current transducer may be any other type of current transducer, such as a current shunt.

[0091] Various modifications may be made to the above described examples by adding, deleting or substituting features to provide further examples, any and all of which are intended to be encompassed by the appended claims.

[0092] The term "coupled" used above includes a direct electrical connection between two components, as well as an indirect electrical connection where two components are electrically connected to each other through one or more intermediate components.

Claims

1. A measurement system for detecting arc faults, the measurement system comprising: Current transducers, used to measure the current in a current-carrying conductor; An arc fault detection circuit, the arc fault detection circuit comprising: a first analog-to-digital converter ADC having an input coupled to the output of the current transducer; a frequency analysis circuit coupled to an output of the first ADC, wherein the frequency analysis circuit is configured to detect an arc fault; and The second detection circuit comprises: a second analog-to-digital converter ADC coupled to the output of the current transducer; and a digital processor coupled to an output of the second ADC, the digital processor configured to determine at least one of: a measure of the current in the current-carrying conductor; the presence of a short circuit; and The presence of residual current. 2 . The measurement system of claim 1 , wherein the first ADC has a first sampling rate and the second ADC has a second sampling rate, the first sampling rate being higher than the second sampling rate. The measurement system of claim 2 , wherein the first sampling rate is greater than 1 Msps. The measurement system of claim 2 , wherein the first sampling rate is greater than 100 Msps.

5. The measurement system of any one of the preceding claims, wherein the current transducer is a current rate of change sensor.

6. The measurement system according to any one of the preceding claims, wherein the frequency analysis circuit detects arc faults by detecting frequency components of the measurement current in the frequency range of 100 kHz-10 MHz.

7. A measurement system according to any one of the preceding claims, wherein the second detection circuit further comprises an integrator, which is arranged to couple the output of the current transducer to the input of the second ADC, so that the integrator integrates the signal output from the current transducer and the second ADC performs digital conversion on the integrated signal.

8. A measurement system according to any one of the preceding claims, wherein the current carrying conductor is a live conductor of a network, wherein at least one of the frequency analysis circuit and the second detection circuit is configured to receive a voltage measurement between a live conductor and a neutral conductor of the network.

9. The measurement system of claim 8, wherein the frequency analysis circuit is configured to detect an arc fault based on the voltage measurement.

10. The measurement system of claim 8 or 9, wherein the digital processor is configured to determine the power or energy consumption of the network based on the current measurement and the voltage measurement.

11. The measurement system according to any one of the preceding claims, wherein the measurement system further comprises: A circuit breaker is configured to interrupt the current in the first current-carrying conductor when an arc fault, a short circuit or a residual current is detected.

12. The measurement system of any one of the preceding claims, wherein the arc fault detection circuit and the second detection circuit are packaged together in a same integrated circuit.

13. The measurement system according to any one of the preceding claims, wherein the arc fault detection circuit and the second detection circuit are respectively packaged in different integrated circuits.

14. A system comprising: a first circuit for coupling to an output of a current transducer for measuring current in a current carrying conductor, the first circuit being configured to perform a frequency analysis on the output of the current transducer to detect an arc fault event based on a frequency component of the measured current in a first frequency range; as well as a second circuit for coupling to an output of the current transducer, the second circuit being configured to perform at least one of the following: Current measurement; Short circuit detection; Residual current detection.

15. The system of claim 14, wherein the first circuit comprises: a filter configured to bandpass filter the output of the current transducer into the first frequency range; as well as An analog frequency analysis system is configured to produce a rectified and averaged signal of the output of the bandpass filter.

16. The system of claim 15, wherein the first circuit further comprises: an analog-to-digital converter configured to receive an output of the analog frequency analysis system and provide a digital output; as well as A digital processor is configured to receive the digital output from the analog-to-digital converter and detect the arc fault based on a magnitude of the digital output.

17. The system of claim 15 or 16, wherein the analog frequency analysis system is further configured to compare the rectified and averaged signal to a threshold, wherein the threshold is indicative of an arc fault event.

18. The system of any one of claims 14 to 17, wherein the second circuit is configured to perform current measurement and short circuit detection based on frequency components of the measured current within a second frequency range.

19. A system comprising: Current rate of change sensor; a first circuit coupled to an output of the current sensor; as well as a second circuit coupled to an output of the current sensor, wherein the first circuit is configured to perform at least one detection function, and the second circuit is configured to perform at least one detection function different from the detection function performed by the first circuit, and The detection functions include: Arc fault detection; Short circuit detection; Current measurement; Residual current detection.

20. The current rate of change sensor of claim 19, wherein the current rate of change sensor is a Rogowski coil.

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