Adaptable method for detection and localisation of a broken conductor occurrence in single wire earth return (SWER) networks

Abstract

A method for detection and localisation of a broken conductor within a Single Wire Earth Return (SWER) power distribution network is provided. The method includes: injecting, from one or more transmitters, a unique and continuous Zadoff-Chu Orthogonal frequency-division multiplexing (OFDM) signal for each transmitter into the network via a coupling circuit. A receiver continuously samples and demodulates the signals to detect the presence of transmitters, wherein detection of a signal is asserted by comparing the averaged cross-correlation signal peak for a particular transmitter and one or more channels in the OFDM scheme designated for estimating noise, as the loss of such signal indicating a broken conductor occurrence. Upon detecting a broken conductor occurrence, the method sends a trip signal to a switching device associated with the receiver to remove power from the system. The method further uses time or frequency reflectometry to estimate the broken conductor location in the network.

Description

ADAPTABLE METHOD FOR DETECTION AND LOCALISATION OF A BROKEN CONDUCTOR OCCURRENCE IN SINGLE WIRE EARTH RETURN (SWER) NETWORKSTechnical Field

[0001] The present invention relates to electrical power distribution protection systems and, more particularly, to electrical power distribution protection systems for SWER networks.Background of Invention

[0002] A SWER network is an electrical power transmission arrangement that is used to deliver electricity in remote areas by way of a single high-voltage conductor for the transmission of electrical power, with the earth itself acting as the return path for the current.

[0003] In remote areas, SWER networks are advantageous in that they have relatively low infrastructure costs due to their simple construction. This is particularly important in remote areas since the cost of installing and maintaining a traditional power line configuration is prohibitive.

[0004] Existing SWER protection schemes, such as Automatic Circuit Reclosers (ACRs), are ineffective at protecting against breakages that do not develop into severe faults. Additionally, there are no current effective solutions for precisely localizing power line breaks after they occur, with localization currently mainly done by field inspections.

[0005] The infrastructure associated with SWER networks heavily limits the ability to monitor for faults. In SWER networks, both faults and load currents return through the earth's path and, in contrast to three-phase systems, voltage imbalances cannot be sensed between phases. SWER networks also have a higher risk of conductor breakages due to their relatively long spacing between poles with highly tensioned conductors. As a result, broken conductors can remain undetected for extended periods, posing serious fire-ignition and safety hazards, as well as downtime in servicing power to customers.

[0006] A problem with existing SWER networks and associated infrastructure is that it is not possible to detect and localise broken conductor occurrences in the network that have not yet developed into a severe earth fault. Further, due to the scale of SWER networks (in Australia, for example) - in the order of hundreds of thousands of kilometres - it is necessary to detect and localise broken conductor occurrences in a timely and accurate manner to significantly reduce their fire-ignition risk. There have been instances of broken conductor-ignited fires in SWER networks resulting in drastic economic damages (in the order of billions) and loss of life in a single event.

[0007] It would be desirable to provide a system and method that ameliorates or at least alleviates one or more of the above problems or to provide an alternative.

[0008] It will be appreciated that the discussion of the background of the invention is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to is published, known or part of the common general knowledge.Summary of Invention

[0009] According to a first aspect, the present invention provides a method for detection and localisation of a broken conductor occurrence by the interaction of at least one transmitter and at least one receiver within a Single Wire Earth Return (SWER) power distribution network, the method including the steps of: (a) injecting, from one or more transmitters, a unique and continuous Zadoff-Chu Orthogonal frequency-division multiplexing (OFDM) signal for each transmitter into the power distribution network via a transmitter coupling circuit; (b) receiving and demodulating the signal from the transmitter via a receiver coupling circuit associated with the receiver, wherein the transmitter and the receiver can be synchronized via a GPS reference signal; (c)the receiver continuously sampling and demodulating signals to detect the presence of transmitters, wherein the detection of a signal is asserted by comparing the averaged cross-correlation signal peak for a particular transmitter and one or more channels in the OFDM scheme designated for estimating the noise, as the loss of such signal indicates a broken conductor occurrence; (d) upon detecting a broken conductor occurrence, sending a trip signal to a switching device associated with the receiver to remove power from the system, mitigating fire ignition risk; and (e)analysing the signal via the receiver using time or frequency reflectometry techniques to estimate the broken conductor location in the network.

[0010] Preferably at step (e), analysing the signal further includes the steps of: (i) continuously monitoring time or frequency reflectometry metrics from all the transmitters; (ii) for each transmitter, comparing the signal reflection delays from both prior to and after the broken conductor occurrence; and (iii) combining the responses from each transmitter to thereby estimate the location of the fault from the combination of their metrics. The method at step (ii) may further include searching for new reflection points and / or removal of prior reflection points that were evident before the broken conductor occurrence.

[0011] Preferably, at step (a) or (b), the method is remotely configured to include or use different Zadoff-Chu-based OFDM modulation schemes, wherein the modulation schemes include one or more of time-shift, interleaved sub-carrier, and distinct-band interleaved component modulation. Preferably, the modulation schemes and signal bandwidth are dynamically selected based on one or more characteristics and / or noise conditions of the SWER network based on the channel estimation metrics given by sweeping the available bandwidth with the transmitted Zadoff-Chu-based signal, whereby frequency ranges can be excluded or shifted to adapt to stationary noise sources or signal fading. Advantageously, this ability to change given network characteristics constitutes the ‘adaptable’ nature of the system.

[0012] Preferably, at step (c), one or more multiplexing cross-correlation techniques are applied to detect the presence of transmitter signals.

[0013] Preferably, at step (c), averaging a period corresponding to one power cycle of signal detection metrics is employed to improve signal discrimination given by the improvement of signal-to-noise ratio.

[0014] Preferably, at step (c), spike detection and / or band jammer mitigation methods are applied, whereby signals containing samples bigger than a threshold, or frequency bands much higher than their average level, are removed from the averaging process, thereby eliminating transient disturbances and persistent narrowband interference, and further increasing signal to noise ratio.

[0015] Preferably, at step (c), an up-down counter is applied to assert a broken conductor occurrence, where its register is incremented at every signal detection and decremented if the signal is not detected, whereby a broken conductor is only asserted after this register accumulates enough instances (a programmable threshold) of no signal detection, further increasing the method’s robustness to spurious noise and false positives.

[0016] Preferably, the synchronisation between the receiver and transmitters is to be carried out via a GPS reference signal, thereby improving signal delay analysis for broken conductor localisation estimates.

[0017] Preferably, at step (a), the transmission is constrained such that there is an integer number of such sequences in a single mains power cycle associated with the network which, when averaged, mitigates the effect of the main’s voltage phasedependent generated noise.

[0018] Preferably, the transmitter coupling circuit is connected to the low-voltage side of a SWER transformer.

[0019] Preferably, the receiver and transmitter are remotely accessible, having software configurable for signal conditioning, including attenuation and amplification, signal processing parameters for handling noise, and software updates, which are set to adapt to different dynamic ranges of the sampled signal, thereby further improving signal integrity and signal propagation through the system.

[0020] Preferably, the receiver and / or transmitter periodically sends processed data, the processed data including one or more of the results of demodulating and detecting transmitter signals, raw time-series samples, and device monitoring metrics via a communication means associated with the receiver and / or the transmitter respectively to a remote server.Brief Description of Drawings

[0021] Figure 1 is a schematic diagram illustrating the overall operation of the method for detection and localisation of a broken conductor occurrence within a SWER power distribution network;

[0022] Figure 2 is a system diagram illustrating the overall operation of the invention as part of a SWER network whereby the data, including raw time-series, processed, and sensor data, may be constantly saved to a cloud storage and provided to a user or displayed in a live dashboard;

[0023] Figure 3 is a flow diagram illustrating the process steps in an embodiment of the invention;

[0024] Figure 4 is a schematic diagram of the receiver architecture associated with the present invention provided within a SWER network; and

[0025] Figure 5 is a schematic diagram of the transmitter architecture associated with the present invention provided within a SWER network.Detailed Description

[0026] The invention will now be described in further detail by reference to the accompanying drawings. It is to be understood that the particularity of the drawings does not supersede the generality of the preceding description of the invention.

[0027] Figure 1 is a schematic diagram illustrating the overall operation of the method for detection and localisation of a broken conductor occurrence within a SWER power distribution network 1000. In the SWER network 1000 there may be provided one or more receivers RX and one or more transmitters TX1, TX2 and TX3. In the present example, only one receiver and three transmitters are shown, but as would be appreciated by the skilled person, any number of receivers and / or transmitters may be provided over any number of SWER networks. The transmitters and receivers are interconnected over a SWER network 1000, which provides power to customers -typically in rural and remote areas. The receiver is coupled to the high-voltage (SWER) power line through a coupling capacitor 1025, capturing a high-fidelity signal at the transmitted signal bandwidth. There is provided a network switching device (at the beginning of the network) as well as a switching device, such as an Automatic Circuit Recloser (ACR), that may be provided at the receiver location. Each of the transmitters TX1 , TX2 and TX3 are deployed to the respective SWER transformers 1005, 1010 and 1015 which are existing power transformers at the customers’ site. These transmitters inject signals on the low-voltage winding side of the transformer, leading to a more cost-effective installation as compared to high-voltage coupling. The detailed operation of the receiver RX and transmitters TX1, TX2 and TX3 will be further described with reference to Figures 4 and 5.

[0028] As can be seen in Figure 1 , there is a broken conductor 1020 in the SWER network 1000. Detecting broken conductors is carried out by placing transmitters at the ends of the SWER network 1000 with a receiver RX provided at a network switching point. Transmitters TX1, TX2 and TX3, for example, are used for continuous transmission of a Zadoff-Chu-based sequence in an Orthogonal frequency-division multiplexing scheme. Although focus is given to the Zadoff-Chu sequence due to its characteristics, other repeating sequences are also possible using the same methods described here. The receiver RX is preferably located at the beginning of the SWER network 1000 at the network switching point and monitors the signal sent by the transmitters TX1 , TX2 and TX3 such that if a signal at any one of TX1 , TX2 or TX3 is lost for a predetermined time period (for example, one second) then the receiver can issue a trip signal through its interface to the network switching device.

[0029] The injected signals are Zadoff-Chu sequences that have zero cyclic autocorrelation, constant amplitude, and low cross-correlation, improving conditions for channel estimation and signal delay analysis. Through cross-correlation analysis and pulse compression, receivers can combine signal delay metrics from all unique transmitters to ultimately determine the location of the broken conductor. It will be appreciated that the broken conductor shown in Figure 1 will change signal propagation delays which can be used to estimate the new distance travelled by transmitters and have its location estimated. This will be further described with reference to Figure 3.

[0030] Figure 2 is a system diagram 2000 illustrating the overall operation of the invention as part of a SWER network 1000 whereby data, including raw time-series, processed and sensor data, which can be accessed by a user or visualised in a live dashboard 2020.

[0031] As will be appreciated, the invention may monitor one or more networks 1000 - 1000n (detail of which is such as that shown in Figure 1). The detailed operation of the arrangement for the detection and location of a broken conductor occurrence will be further described with reference to Figure 3.

[0032] It will be appreciated that each of the transmitters and receivers in the SWER network 1000 are connected by a powerline. The receivers and transmitters are in turn connected to a cellular network 2005 via a mobile communication connection which may be, for example, an LTE network, satellite network or the like. Cellular network 2005 may in turn be connected to the Internet 2010 via backhaul and in turn to a cloud server 2015. Cloud server 2015 may be connected to a cloud storage service, and one or more users 2020 who may be utilising a user device to receive data and alerts in relation to the SWER network 1000, and / or to interface with the receiver RX....RX-n or transm itters TX1 ... TXn.

[0033] In operation, the receiver RX... RX-n may periodically or continuously send data through the network to the cloud server 2015, including a cloud storage service, to a dashboard or the like, and to one or more users 2020 for monitoring. For example, when a conductor breakage occurs, an alert may be emitted to one or more users 2020 to alert for the occurrence of an event. Moreover, the receiver RX.... RX-n has the ability to not only continuously send processed data to the cloud server 2015, but also preferably raw, time-series signal capture for further diagnosis of events. It will be appreciated that the user 2020 has complete control of the method in that they have the ability to remotely access the transmitters and receivers and the like, so it can be fully programmable. User 2020 can also send commands to change all that is programmable in the transmitters and receivers. Alerts and data are also provided to the device.

[0034] Figure 3 is a flow diagram illustrating the process steps in an embodiment of the present invention, which may be implemented by software and / or hardware components such as those described with reference to Figures 1 , 2 and 4 to 5.

[0035] The present invention detects and localises an occurrence of broken conductors by way of the interaction with at least one transmitter and at least one receiver within a SWER power distribution network.

[0036] At step 3005, a unique and continuous Zadoff-Chu Orthogonal Frequency-Division Multiplexing (OFDM) signal is injected from one or more transmitters into the SWER distribution network via a transmitter coupling circuit. The transmitter coupling circuit will be described further with reference to Figure 5.

[0037] Advantageously, the use of Zadoff-Chu-based sequences allows for continuous channel estimation (applicable to the adaptability of the system in terms of modulation schemes), and synchronisation between transmitters and receivers with a GPS reference signal or other sources of time reference (such as mains frequency). The use of Zadoff-Chu-based sequences further provides robustness due to improved Peak-to-Average Power Ratio (PAPR) and excellent correlation properties, which allow time and or frequency domain processing and a large number of sequences with bounded cross-correlation features (which allows a defined leakage tolerance between networks of a multi-network system).

[0038] At step 3010, the signal is received and demodulated from the transmitter via a receiver coupling circuit associated with the receiver. The transmitter and receiver are preferably synchronised via a GPS reference signal or the like. Operation of the receiver coupling circuit will be further described with reference to Figure 4.

[0039] At step 3015, the receiver continuously samples and demodulates signals to detect the presence of transmitters. The detection of a signal is determined by comparing the averaged cross-correlation signal peak for a particular transmitter and one or more channels designated for estimating the noise, as the sustained loss of such signal (over a predetermined time period such as 1 s) indicates a broken conductor occurrence. Upon detecting a broken conductor occurrence, the method proceeds to step 3020 in which a trip signal is sent to a switching device associated with the receiver to remove power, mitigating fire ignition risk, for example.

[0040] In an embodiment, the signal may be detected continuously or semi-continuously (for example, at every 1ms or as per particular network requirements). The determination is made by comparing the multiplexing channels in the signal that represent different transmitters and noise. The detection threshold may be a value based on the distance between signal correlation values of a particular user and noise. Advantageously, the present invention can dynamically and remotely change the modulation parameters to adapt to different network characteristics, which results in a more robust solution as SWER networks are noisy and may generate interference in particular bands.

[0041] The system’s adaptability allows it to function effectively across various SWER network topologies, including those with underground sections. It can adjust its operational parameters in response to changing network conditions, ensuring consistent performance over time.

[0042] It will be appreciated that at step 3015 the receiver continuously samples and demodulates signals using time-shift or frequency interleaved multiplexing techniques to detect the presence of transmitters. The detection of a signal may be determined by comparing the averaged cross-correlation signal peak for a particular transmitter and a channel designated for estimating the noise, where channels with transmitters, the cross-correlation of the signal yields a peak higher than the peak of the channel designated for noise measurements. It will be appreciated that the detection threshold may be a value based on the distance between signal correlation values of a particular transmitter and noise. The sustained loss of one of the transmitters (over a predetermined time period) resulting in the cross-correlation peak of that channel to fall nearby (or close to) the peak of the channel designated for noise measurements thereby indicates a broken conductor occurrence.

[0043] Finally at step 3025, the signal is analysed by the receiver using time or frequency reflectometry techniques to estimate the broken conductor location in the network.

[0044] Advantageously, the transmitter and receiver coupling circuits are designed to allow for seamless integration with the SWER network without significant changes to the infrastructure. Preferably, a large number of transmitters are utilised in the network with the present invention, since the ability to monitor the network improves with the number of transmitters used.

[0045] It will be appreciated that step 3025 may further include the steps of analysing the signal by: continuously monitoring time or frequency reflectometry metrics from all the transmitters; and for each transmitter, comparing the signal reflection delays from both prior to and after the broken conductor occurrence determined at step 3020 above. The method may further include the step of combining the responses from each transmitter to thereby estimate the location of the fault based on the combination of their metrics.

[0046] It will be appreciated that when comparing the signal reflection delays from both prior to and after the broken conductor occurrence, the method may further include searching for new reflection points and / or removal of prior reflection points that were evident before the broken conductor occurrence.

[0047] In an embodiment, at either step 3005 or 3010 the method may be remotely configured to include or use different Zadoff-Chu-based OFDM modulation schemes, wherein the modulation schemes include one or more of time-shift, interleaved subcarrier, and distinct-band interleaved component modulation.

[0048] In an embodiment, the modulation schemes and signal bandwidth may be dynamically selected based on one or more characteristics and / or noise conditions of the SWER network based on the channel estimation metrics given by sweeping the available bandwidth with the transmitted Zadoff-Chu-based signal, whereby frequency ranges can be excluded or shifted to adapt to stationary noise sources or signal fading.

[0049] In an embodiment, the method at step 3015 may further include one or more multiplexing cross-correlation techniques being applied to detect the presence of transmitter signals.

[0050] In a further embodiment, at step 3015, signal discrimination may be improved by averaging a period corresponding to one power cycle of signal detection metrics to thereby improve the signal-to-noise ratio.

[0051] In an embodiment, step 3015 may include a spike detection and / or band jammer mitigation method. This may include having signals containing samples bigger than a particular threshold, or frequency bands that are much higher than their average level and are removed from the averaging process, thereby eliminating transient disturbances and persistent narrowband interference, and further increasing the signal-to-noise ratio.

[0052] In a further embodiment, step 3015 may include an up-down counter applied to assert and / or determine sustained loss of signal reception indicative of a broken conductor occurrence. In operation, an up-down register is incremented at every signal detection and decremented if the signal is not detected. In this way, a broken conductor is only asserted after this register accumulates enough instances (a predeterminedprogrammable threshold, for example) of no signal detection, further increasing robustness to spurious noise.

[0053] The system employs an up-down counter method to enhance reliability in bursty, noisy environments. This method ensures that momentary signal losses or impulsive noise do not trigger false alarms, while still maintaining the ability to detect genuine breakage within one second.

[0054] It will be appreciated that the synchronisation between receiver and transmitters may be carried out via a GPS reference signal thereby improving signal delay analysis for broken conductor localisation estimates.

[0055] In an embodiment, the transmission at step 3005 may be constrained such that there is an integer number of such sequences in a single mains power cycle associated with the network which, when averaged, may mitigate the effect of the mains voltage phase-dependent generated noise. Advantageously, this allows for compensation for line voltage (or current) dependent distortions.

[0056] The system implements a pre-distortion technique to improve crosscorrelation levels at the receiver. This technique applies inverse distortion to the input signal of the line driver to minimize the distortion generated by the power amplifier and SWER transformer, enhancing the overall signal quality and detection accuracy.

[0057] In an embodiment, the receiver and transmitter associated with the method 3000 may be remotely accessible, such as described with reference to Figure 1 , having software configurable for signal conditioning, including attenuation and amplification, signal processing parameters for handling noise, and for software updates. Preferably, each of these may be set to adapt to different dynamic ranges of the sampled signal, thereby further improving signal integrity and signal propagation. For example, remote programmability allows a flexible frequency-dependent amplitude modulation to compensate for specific network attenuation characteristics, which results in improved signal transmission and improved signal integrity at the receiver. In a further example, a transmitter pre-distortion technique may be applied to the frequency-dependent amplitude and / or phase of the Zadoff-Chu signal to counteract against attenuations or fading from the transmission channel (power line), resulting in a signal at the receiver with a higher degree of correlation to the original signal.

[0058] Preferably, the receiver and / or transmitter periodically sends processed data, the processed data including one or more of the results of demodulating and detecting transmitter signals, raw time-series samples, and device monitoring metrics via communication means associated with the receiver and / or the transmitter respectively to a remote server such as that described with reference to Figure 4 and 5.

[0059] Figure 4 is a schematic diagram of the receiver architecture 4000 associated with the present invention and utilised in combination with a receiver 4005 and a receiver coupling capacitor 4010 and provided within and connected to a SWER network 4015 (and such as that also illustrated in Figure 1). The receiver coupling circuit, part of receiver 4005, includes impedance matching circuits and band-pass filters, interfacing signals from the coupling capacitor with the receiver 4005. The receiver 4005 includes a power / BMS (battery management system), which powers the receiver 4005 and can sustain functionality without power for continuous diagnostics. The receiver also includes a number of components namely a coupling circuit filter component, controllable amplifier, ADC (analogue-to-digital converter), FPGA, LTE modem, gateway, CPU and DSP and further including a GPS antenna / Pulse Per Second for synchronisation. Interface components 4020 include a remote server, storage, a user dashboard and user access / device which can be remotely connect to the receiver 4005.

[0060] It will be appreciated that the coupling circuit, included in the receiver 4005, allows a matching of impedance from a coupling capacitor circuit to a signal conditioning circuit within the receiver 4005. The circuit conditioning circuit may be composed of band-pass filters and selects frequencies within the relevant band. The controllable amplifier allows for programmable gain before the ADC so it can adjust to different dynamic ranges. The ADC converts sampled values to digital signals that are routed to the FPGA. The FPGA, DSP, CPU and gateway are the computational part of the receiver 4005 and could be provided as one unit, but are shown separately for completeness. A programmable logic device (FPGA) that generates the sampling clock from an external high-precision clock and accumulates the samples from the ADC to a buffer. The buffer is transmitted to the real-time processor (DSP), which is responsible for the signal processing functions mentioned before, i.e. spike detection, band jammer, correlation, delay analysis, then outputs the metrics to a CPU. It will be appreciatedthat the CPU and the Gateway can be the same device and they package and compress the outputs from the DSP and transmit to the cloud through the gateway. The DSP may also store raw time-series data, that can be transmitted by the CPU and gateway to the cloud. They can be transmitted at regular intervals or by user request. The CPU can also capture data from sensors and device health and send it to the cloud for continuous monitoring.

[0061] Figure 5 is a schematic diagram of the transmitter architecture 5000 associated with the present invention and utilised in combination with transmitter 5005 and circuit 5010 connected to the low voltage side of the existing SWER transformer on the SWER network 5015 (and such as that also illustrated in Figure 1). The transmitter circuit 5010 includes an SWER transformer with the transmitter circuit 5010 being connected to the low-voltage side of the SWER transformer as well as a low-pass filter for avoiding unwanted emissions from the transmitters which interfere with customer loads. The transmitter 5005 includes a power / BMS (battery management system) which powers the transmitter 5005. The transmitter also includes a number of components, namely a line driver, DAC (digital to analogue converter), FPGA, LTE modem, gateway and CPU and further including a GPS antenna / Pulse Per Second for synchronisation. Interface components 5020 include a server and user access / device, which is remotely connected to the transmitter 5005.

[0062] It will be appreciated that the term 'user device' may refer to any device that employs a processor and memory and can perform computing functions, such as a personal computer or a mobile device, wherein a mobile device is any mobile communication device, such as a cellular telecommunications device (i.e., a cell phone or mobile phone), personal digital assistant (PDA), a mobile Internet accessing device, or other mobile device.

[0063] It will be appreciated that some embodiments may be comprised of one or more generic or specialised controllers or processors (or 'processing devices') such as microcontrollers, microprocessors, digital signal processors, customised processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and / or apparatus described herein. Alternatively, some or allfunctions could be implemented by a state machine that has no stored program instructions, or in one or more application-specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used.

[0064] As discussed above, the various embodiments can be implemented in a wide variety of operating environments, which in some cases can include one or more user computers, computing devices, or processing devices that can be used to operate any of a number of applications. User or client devices can include any one of a number of general-purpose personal computers, such as desktop or laptop computers running a standard operating system, as well as cellular, wireless, and handheld devices running mobile software and capable of supporting a number of networking and messaging protocols. Such a system can also include a number of workstations running any of a variety of commercially available operating systems and other known applications for purposes such as development and database management. These devices also can include other electronic devices, such as dummy terminals, thin-clients, gaming systems, and other devices capable of communicating via a network.

[0065] Some embodiments may utilise at least one network that would be familiar to those skilled in the art for supporting communications using any of a variety of commercially available protocols, such as TCP / IP, OSI, FTP, UPnP, NFS, and CIFS. The network can be, for example, a local area network, a wide-area network, a virtual private network, the Internet, an intranet, an extranet, a public switched telephone network, an infrared network, a wireless network, and any suitable combination thereof.

[0066] While the invention has been described in conjunction with a limited number of embodiments, it will be appreciated by those skilled in the art that many alternatives, modifications and variations in light of the foregoing description are possible. Accordingly, the present invention is intended to embrace all such alternative, modifications and variations as may fall within the spirit and scope of the invention as disclosed.

Claims

The claims defining the invention are as follows:

1. A method for detection and localisation of a broken conductor occurrence by the interaction of at least one transmitter and at least one receiver within a Single Wire Earth Return (SWER) power distribution network, the method including the steps of:(a) injecting, from one or more transmitters, a unique and continuous Zadoff-Chu Orthogonal frequency-division multiplexing (OFDM) signal for each transmitter into the power distribution network via a transmitter coupling circuit;(b) receiving and demodulating the signal from the transmitter via a receiver coupling circuit associated with the receiver, wherein the transmitter and the receiver can be synchronized via a GPS reference signal;(c) the receiver continuously sampling and demodulating signals to detect the presence of transmitters, wherein the detection of a signal is asserted by comparing the averaged cross-correlation signal peak for a particular transmitter and one or more channels in the OFDM scheme designated for estimating the noise, as the loss of such signal indicating a broken conductor occurrence;(d) upon detecting a broken conductor occurrence, sending a trip signal to a switching device associated with the receiver to remove power from the system, mitigating fire ignition risk; and(e) analysing the signal via the receiver using time or frequency reflectometry techniques to estimate the broken conductor location in the network.

2. The method of claim 1 , wherein at step (e), analysing the signal further includes the steps of:(i) continuously monitoring time or frequency reflectometry metrics from all the transmitters;(ii) for each transmitter, comparing the signal reflection delays from both prior to and after the broken conductor occurrence; and(iii) combining the responses from each transmitter to thereby estimate the location of the fault from the combination of their metrics.

3. The method of claim 2, wherein at step (ii), the method further includes searching for new reflection points and / or removal of prior reflection points that were evident before the broken conductor occurrence.

4. The method of claim 1 , wherein at step (a) or (b), the method being remotely configured to include or use different Zadoff-Chu-based OFDM modulation schemes, wherein the modulation schemes include one or more of time-shift, interleaved sub-carrier, and distinct-band interleaved component modulation.

5. The method of claim 4, wherein the modulation schemes and signal bandwidth are dynamically selected based on one or more characteristics and / or noise conditions of the SWER network based on the channel estimation metrics given by sweeping the available bandwidth with the transmitted Zadoff-Chu-based signal, whereby frequency ranges can be excluded or shifted to adapt to stationary noise sources or signal fading.

6. The method of claim 1, wherein at step (c), one or more multiplexing crosscorrelation techniques are applied to detect the presence of transmitter signals.

7. The method of claim 1 , wherein at step (c), averaging a period corresponding to one power cycle of signal detection metrics is employed to improve signal discrimination given by the improvement of signal-to-noise ratio.

8. The method of claim 1 , wherein at step (c), spike detection and / or band jammer mitigation methods are applied, whereby signals containing samples bigger than a threshold, or frequency bands much higher than their average level, are removed from the averaging process, thereby eliminating transient disturbances and persistent narrowband interference, and further increasing signal-to-noise ratio.

9. The method of claim 1 , wherein at step (c), an up-down counter is applied to assert a broken conductor occurrence, where its register is incremented at every signal detection and decremented if the signal is not detected, whereby a broken conductor is only asserted after this register accumulates enough instances (a programmable threshold) of no signal detection, further increasing the method’s robustness to spurious noise and false positives.

10. The method of claim 1, wherein the synchronisation between the receiver and transmitters can be carried out via a GPS reference signal, thereby improving signal delay analysis for broken conductor localisation estimates.

11. The method of claim 1 , wherein at step (a) the transmission is constrained such that there is an integer number of such sequences in a single mains power cycle associated with the network which, when averaged, mitigates the effect of the main’s voltage phase-dependent generated noise.

12. The method of claim 1, wherein the transmitter coupling circuit is connected to the low-voltage side of a SWER transformer.

13. The method of claim 1, the receiver and transmitter being remotely accessible, having software configurable for signal conditioning, including attenuation and amplification, signal processing parameters for handling noise, and software updates, which are set to adapt to different dynamic ranges of the sampled signal, thereby further improving signal integrity and signal propagation.

14. The method of claim 1 , wherein the receiver and / or transmitter periodically sends processed data, the processed data including one or more of results of demodulating and detecting transmitter signals, raw time-series samples, and device monitoring metrics via a communication means associated with the receiver and / or the transmitter respectively to a remote server.

Images