FIELD OF THE INVENTION

[0001] The present invention relates generally to electrical systems including protective Multiple Earth Neutral (MEN) links, and in particular to a system for monitoring the operating effectiveness of a MEN link and related switchboard circuitry.

BACKGROUND

[0002] Multiple Earth Neutral (MEN) systems enable dangerous currents from faulty electrical connections to follow a return path to a switchboard through an earth conductor. That can greatly improve the safety of an electrical system, as it enables the protective circuit elements of the switchboard, such as circuit breakers or fuse links, to timely operate and open a faulty circuit.

[0003] An MEN system generally employs a circuit’s neutral conductor for receiving fault currents. When a fault occurs that directs current from an active circuit component to a grounded component, the MEN system ensures that the fault current is directed to the switchboard through a low impedance MEN link circuit element. Without the MEN link, the fault current would generally be directed into the ground, where the impedance can be unacceptably high. Such high impedance can reduce the magnitude of the fault current so that the protective circuit elements of the switchboard do not operate, leaving a potentially dangerous and or deadly voltage present on metal enclosures in electrical contact with the faulty circuit.

[0004] Ensuring that a MEN link system is properly installed thus can be very important to the overall safety of an electrical installation, as it can enable faster and more reliable operation of circuit protection devices. Safety guidelines thus often recommend that electricians make a further safety check of a MEN link as a final task when installing or modifying electrical equipment. [0005] Fault loop impedance tests, using available supply voltage and a suitable plug-in test instrument can be a simple and reliable indication that a MEN link is working properly. A low value of fault loop impedance is generally a good indication that the fault loop path, including the MEN link, is effective. High fault loop impedance values should always be urgently investigated.

[0006] However, the ongoing operational effectiveness of a MEN link can be difficult, inconvenient and/or expensive to monitor, as switchboards may remain uninspected for long periods of time during which system degradation due to mechanical damage, corrosion, or unauthorised or hazardous modifications may undermine the safety and effectiveness of a MEN link.

[0007] There is therefore a need for an improved system for monitoring a MEN link.

OBJECT OF THE INVENTION

[0008] It is an object of the present invention to overcome and/or alleviate one or more of the disadvantages of the prior art or provide the consumer with a useful or commercial choice.

SUMMARY OF THE INVENTION

[0009] In a first aspect, although it need not be the only or the broadest aspect, the invention resides in system for monitoring a multiple earth neutral (MEN) link, comprising: a switchboard connected to a mains power supply via an active power line and a neutral line; a MEN link connected to the neutral line and to an earthing conductor; an energy storage system connected to the switchboard; and a hardware interface comprising: a first communication link to an external network; a second communication link to the energy storage system; a first data input channel connected to the earthing conductor; a second data input channel connected to the MEN link; a third data input channel connected to the neutral line; and a fourth data input channel connected to the active power line; wherein the first communication link is enabled to transmit status signals concerning the energy storage system and the MEN link.

[0010] Preferably, at least one of the first, second, third and fourth data input channels are connected to a power quality sensor.

[0011] Preferably, the power quality sensor outputs current and voltage signals.

[0012] Preferably, the hardware interface further comprises a computer processor for processing signals from at least one of the first, second, third and fourth data input channels.

[0013] Preferably, the fourth data input channel connected to the active power line transmits a power line feed signal.

[0014] Preferably, the third data input channel connected to the neutral line transmits a neutral line power signal.

[0015] Preferably, the first data input channel connected to the earth line transmits a current value and direction signal.

[0016] Preferably, the second data input channel connected to the MEN link transmits a current value and direction signal.

[0017] Preferably, the direction signal of the second data input channel connected to the MEN link is compared with a current direction signal of a MEN link of a neighbouring property.

[0018] Preferably, the energy storage system comprises a battery, a battery inverter and a solar power inverter. [0019] Preferably, at least one of the first and second communication links is a wireless communication link.

[0020] Preferably, the hardware interface is a single, integrated electronic device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, preferred embodiments of the invention are described below by way of example only with reference to the accompanying drawings, in which:

[0022] FIG. 1 is a schematic diagram of a system for monitoring an energy storage system and a MEN link, according to some embodiments of the present invention.

[0023] FIG. 2 is an illustration of an example of the energy storage system of the system of FIG. 1.

[0024] FIG. 3 is a schematic diagram of an example of the hardware interface of the system of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] The present invention relates to an improved system for monitoring a multiple earth neutral (MEN) link. Elements of the invention are illustrated in concise outline form in the drawings, showing only those specific details that are necessary to understanding the embodiments of the present invention, but so as not to clutter the disclosure with excessive detail that will be obvious to those of ordinary skill in the art in light of the present description.

[0026] In this patent specification, adjectives such as first and second, left and right, above and below, top and bottom, upper and lower, rear, front and side, etc., are used solely to define one element or method step from another element or method step without necessarily requiring a specific relative position or sequence that is described by the adjectives. Words such as “comprises” or “includes” are not used to define an exclusive set of elements or method steps. Rather, such words merely define a minimum set of elements or method steps included in a particular embodiment of the present invention.

[0027] According to one aspect, the present invention is defined as a system for monitoring a multiple earth neutral (MEN) link, comprising: a switchboard connected to a mains power supply via an active power line and a neutral line; a MEN link connected to the neutral line and to an earthing conductor; an energy storage system connected to the switchboard; and a hardware interface comprising: a first communication link to an external network; a second communication link to the energy storage system; a first data input channel connected to the earthing conductor; a second data input channel connected to the MEN link; a third data input channel connected to the neutral line; and a fourth data input channel connected to the active power line; wherein the first communication link is enabled to transmit status signals concerning the energy storage system and the MEN link.

[0028] Advantages of some embodiments of the present invention include a system that enables the improved safety of electrical switchboards installed in buildings and other locations. Real time monitoring of a MEN link can ensure that any relevant increase in impedance concerning the MEN link, whether due to improper installation or maintenance, mechanical damage, corrosion, or unauthorised or hazardous modifications, can be quickly alerted and corrected.

[0029] Further, some embodiments of the present invention enable use of a single hardware interface to achieve real time monitoring of both the energy storage system and the MEN link. Further, other elements of a switchboard also can be monitored in real time, including active, neutral and ground lines, and trends in impedance value changes over time can enable early detection and correction of deteriorating system conditions due for example to corrosion or loosening of wired connections.

[0030] Those skilled in the art will appreciate that not all of the above advantages are necessarily included in all embodiments of the present invention.

[0031] FIG. 1 is a schematic diagram of a system 100 for monitoring an energy storage system 105 and a MEN link 110. External power lines 115 from a mains or utility power supply are shown extending to a switchboard 120, such as a circuit breaker panel in a home. Both an active power line 125 and a neutral line 130 are connected to the switchboard 120, as is known in the art. The energy storage system 105 is also hard wired to the switchboard 120 via a connection 133. The MEN link 110 includes an earthed grounding connection 135 through a shunt 140, and is monitored by a power quality sensor 143. The shunt 140 enables measurement of the impedance of the MEN link 110.

[0032] A hardware interface 145 is generally mounted on or near the switchboard 120. The hardware interface 145 includes the following: a first data input point 150 connected to the earthed grounding connection 135 through a power quality sensor 155; a second data input point 160 connected to the power quality sensor 143 and shunt 140; a third data input point 165 connected to the neutral line 130 through a power quality sensor 170; a fourth data input point 175 connected to the active power line 125 through a power quality sensor 177; a first communication link 180 connected to an external network 183 via a wireless transceiver 185; and a second communication link 187 connected to the energy storage system 105.

[0033] The first and second communication links 180, 187 are generally wireless links, such as WiFi links, but wired links and various alternative wireless communication protocols also can be used. The external network 183 generally can be the Internet or an alternative proprietary or public communication network.

[0034] A monitoring station 189 receives data concerning the system 100 from the hardware interface 145 and transmits status reports and alerts to customers, such as the owner of a residence at which the switchboard 120, hardware interface 145 and energy storage system 105 are installed. For example, the monitoring station 189 may be affiliated with an installer or manufacturer of the energy storage system 105.

[0035] By combining data from the energy storage system 105 with data from the data received at the first, second, third and fourth data input points 150, 160, 165, 175, respectively, which each define a data channel, the hardware interface 145 is enabled to monitor the operating integrity of the system 100. For example, using the first data input point 150 the interface 145 can monitor the earthed grounding connection 135 for imbalance and a direction of any resultant energy flows. Using the second data input point 160 the interface 145 can monitor for any imbalance concerning the MEN link 110 and the direction of any resultant energy flows. Using the third data input point 165 the interface 145 can monitor for any imbalance concerning the neutral line 130. Using the fourth data input point 175 the interface 145 can monitor in real time the active power line 125 and line feed parameters concerning the feed into the customer’s premises.

[0036] Real time monitoring by the interface 145 enables improved and comprehensive reporting to a customer concerning the safety and operation of the switchboard 120 and the local electrical circuitry and appliances connected to the switchboard 120, including the energy storage system 105 and the MEN link 110.

[0037] The interface 145 detects voltage and current in the active power line 125 and in the neutral line 130, and detecting voltage, current and current direction in the MEN link 110 and earthed grounding connection 135. Normal operation of the system 100 requires the ratio of the active current and neutral current to be less than 1 ; whereas a fault condition is detected if the ratio of the active current and neutral current is greater than 1. Further, the neutral line 130 is determined to be open if its current flow drops to zero and fault current flows via the earthed grounding connection 135. Also, fault detection for a broken earth connection is detected if the ratio of the active current and neutral current is one. [0038] According to some embodiments, data from additional switchboards 190, 195 installed at neighbouring properties, such as adjacent houses on a same street, is also transmitted to the wireless transceiver 185 using a known wireless communication protocol.

[0039] By simultaneously monitoring multiple neighbouring properties, additional data integrity and intelligence concerning the monitored systems can be obtained. For example, when premises with contiguous boundaries are monitored, the location of a fault in a MEN link, neutral line or active line can be pinpointed by comparing the direction and magnitude of current flow at each premise’s MEN link. Variations in data due to weather events also can be corrected.

[0040] FIG. 2 is an illustration of an example of the energy storage system 105 of the system 100, according to some embodiments. The system 105 includes a housing 205 covering a plurality of batteries 210, having for example voltage and energy specifications of 48 V, 3.3kWh or 6.5kWh or greater. Solar and battery inverters 210, 215 convert variable direct current outputs of a photovoltaic solar panel (not shown) or the batteries 210 into a utility frequency alternating current that can be fed into the power lines 115 of the local electrical grid or used by a local, off-grid electrical network serviced through the switchboard 120. Vents 220 assist in keeping the interior of the housing 205 within a desired operating temperature range.

[0041] FIG. 3 is a schematic diagram of an example of the hardware interface 145 of the system 100, according to some embodiments. For example, each of the first, second, third and fourth data input points 150, 160, 165, 175 comprise a pair of 4-20 mA and/r 0-5 V analogue inputs for receiving the various data signals from the corresponding power quality sensors 155, 143, 170, 177, respectively. The interface 145 further includes a computer processor 300 for processing signals received at the interface 145 and instructing output signals transmitted from the interface 145. Such signals also can be further processed at the monitoring station 189.

[0042] Based on an analysis of received data, the monitoring station 189 determines if any unsafe conditions are present in the circuitry associated with the switchboard 120. If an unsafe condition is detected, the monitoring station 189 can immediately send alerts to a customer or automatically dispatch a technician to the relevant premises.

[0043] Various communication protocols can be used to communicate between the hardware interface 145 and the monitoring station 189. For example, Modbus over Ethernet, as is known in the art, facilitates a structured addressable table for swapping of information/control data.

[0044] Those skilled in the art will understand that the concept of a MEN link as defined in the present specification is functionally equivalent to corresponding neutral-earth concepts used in other jurisdictions, including Protective Multiple Earthing (PME) systems in the United Kingdom, and Multi- Grounded Neutral (MGN) systems in North America. The term MEN link as used herein thus should be interpreted broadly to include the related technology of such corresponding systems.

[0045] Those skilled in the art will appreciate that various components of embodiments of the present invention can be made of various materials and as various integrated or non-integrated designs.

[0046] The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. Numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. Accordingly, this patent specification is intended to embrace all alternatives, modifications and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.