NZ787440A - Anomalous neutral electrical protection apparatus - Google Patents

Abstract

Provided is anomalous neutral electrical protection apparatus 10 comprising at least one live detector 12 for operative interconnection to a live mains electrical supply 14 of an electrical installation 16, and a neutral detector 18 for operative interconnection to a MEN link 20 of said electrical installation 16. Apparatus 10 also includes an interrupter 22 configured to selectively interrupt the mains electrical supply 12, and a microprocessor 24 which is configured to i) via the live detector, continuously monitor the live mains electrical supply to detect live current level; ii) via the neutral detector, continuously monitor the MEN link to detect neutral current level; iii) correlate the monitored current levels to infer a line impedance criterion indicative of a neutral anomaly; and iv) if the inferred line impedance criterion is present for a predetermined period of time, interrupt the mains electrical supply 14 by means of the interrupter 22. nstallation 16. Apparatus 10 also includes an interrupter 22 configured to selectively interrupt the mains electrical supply 12, and a microprocessor 24 which is configured to i) via the live detector, continuously monitor the live mains electrical supply to detect live current level; ii) via the neutral detector, continuously monitor the MEN link to detect neutral current level; iii) correlate the monitored current levels to infer a line impedance criterion indicative of a neutral anomaly; and iv) if the inferred line impedance criterion is present for a predetermined period of time, interrupt the mains electrical supply 14 by means of the interrupter 22.

Description

Provided is ous neutral electrical protection apparatus 10 sing at least one live detector 12 for operative interconnection to a live mains ical supply 14 of an electrical installation 16, and a neutral detector 18 for operative interconnection to a MEN link 20 of said electrical installation 16. Apparatus 10 also es an interrupter 22 configured to selectively interrupt the mains electrical supply 12, and a microprocessor 24 which is configured to i) via the live detector, continuously monitor the live mains electrical supply to detect live current level; ii) via the neutral detector, continuously monitor the MEN link to detect neutral t level; iii) correlate the monitored current levels to infer a line impedance criterion indicative of a neutral anomaly; and iv) if the inferred line impedance criterion is present for a predetermined period of time, interrupt the mains electrical supply 14 by means of the interrupter 22.

NZ 787440 ANOMALOUS NEUTRAL ELECTRICAL TION TUS TECHNICAL FIELD This invention broadly relates to the field of electrical supply and safety, and more specifically to anomalous neutral electrical protection apparatus and an associated method of anomalous l electrical protection.

BACKGROUND ART The ing discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or ion that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

In electricity supply, a ‘broken’ or high impedance neutral is a relatively common but potentially lifethreatening electrical fault. Electrical power flows in and out of an installation, such as residential or commercial premises, from an electricity k, generally entering via the active conductor and leaving via the l conductor.

Most, if not all, electrical installations also have an earth connection. Such earth connection may be ly connected to the neutral connection, which is known as a MEN (Multiple Earthed Neutral) system of earthing. In such a system, i f there's a break in the neutral return path, electricity can still exit the premises via the earth connection.

For example, in MEN (Multiple Earthed Neutral) systems of earthing, which are common in countries like Australia, New d and South Africa, a network neutral conductor is used as the conductive path for installation earth fault currents. In an electrical fault where the active conductor is disconnected from the neutral conductor and connected to any exposed metal part of the installation, the current flows through the earth conductor to the switchboard, which allows the protective device (such as fuses or circuit breakers) to open circuit. In this manner, current can travel from one neutral-earth connection, through the ground and into r neutral-earth connection, then back into the network’s neutral. In this way, the MEN system increases the safety of the circuit in such a fault scenario.

In earthed electrical installations, if there are problems with the neutral path, electricity can travel by a different path, such as via water or gas pipes, stoves and metal taps or any other tor of electricity. As a result, any electrically-earthed exposed metal can become live under specific circumstances. This can be very dangerous and there is risk of serious electrical shock. Such anomalous neutral paths have resulted in serious es and fatalities in the past.

Anomalies on the neutral tor may include a broken or damaged line, or any occurrence that severely alters the inductance, capacitance and/or impedance of the neutral conductor. Due to the high impedance of the general mass of earth relative to a typical electrical supply l conductor, a significant voltage potential can exist n this earth connection and the l mass of earth.

For general ical protection, a variety of circuit breakers exist, such as DIN circuit protection breakers, e.g. residual current devices or RCDs. A DIN rail is a metal rail of a standard type widely used for mounting circuit breakers and industrial l equipment inside equipment racks. The term s from the original specifications published by hes Institut für Normung (DIN) in y, which have since been adopted as European (EN) and international (IEC) standards. DIN rails are widely used to mount circuit breakers, , programmable logic controllers, motor controllers, and other electrical equipment.

Conventional circuit breakers, such as DIN mount RCD breakers used in most electrical installations, cannot adequately avoid or address broken or anomalous neutral conditions on a supply side of an electrical installation.

Accordingly, Applicant has identified a shortcoming in the art for means to s broken or anomalous neutral conditions on a supply side of an electrical installation and the current invention was conceived with this shortcoming in mind.

SUMMARY OF THE INVENTION The skilled addressee is to appreciate that reference herein to an ‘electrical installation’ comprises reference to any electrical subsidiary circuit(s) supplied by an electrical supply system, such as individual residential or commercial premises supplied from a mains icity supply, as is known in the art of ical reticulation.

Similarly, reference herein to ‘MEN link’ generally refers to the link between the main earth terminal and the main l conductor as known in Multiple Earthed Neutral (MEN) systems of earthing.

According to a first aspect of the invention there is provided ous neutral electrical protection apparatus comprising: at least one live detector for operative interconnection to a live mains electrical supply of an electrical lation; a neutral detector for operative interconnection to a MEN link of said ical installation; an interrupter configured to selectively interrupt the mains ical supply; and a microprocessor configured to: i) via the live detector, continuously monitor the live mains electrical supply to detect live current level; ii) via the neutral detector, continuously monitor the MEN link to detect neutral current level; iii) correlate such monitored current levels to infer a line impedance criterion indicative of a neutral y; and iv) if the inferred line impedance criterion is present for a predetermined period of time, upt the mains electrical supply by means of the interrupter.

Typically, the apparatus comprises a DIN-mountable housing configured to be mounted in the electrical lation’s electrical distribution board, panel board, breaker panel, or electric panel, the detectors, interrupter and microprocessor housed within said housing.

Typically, the apparatus comprises a live detector for each phase of the live mains electrical supply, i.e. one live or for a single-phase supply and three live detectors for a three-phase supply.

In an embodiment, the live detector comprises a current transformer.

In an embodiment, the neutral detector ses a current ormer.

In an embodiment, the interrupter comprises a suitable breaker, such as an omechanical t r, configured to selectively interrupt the mains electrical supply.

Typically, the interrupter is comprised of an existing residual current device (RCD) within the electrical installation’s electrical distribution board, said microprocessor arranged in signal communication therewith and configured to activate such RCD to interrupt the mains electrical supply.

In an embodiment, the rocessor comprises a digital signal processor (DSP). However, the skilled addressee is to appreciate that the microprocessor may include any suitable processor or microcontroller configured to receive input, perform logical and arithmetical operations on a suitable instruction set, and provide output, as well as transitory and/or non-transitory electronic storage.

Typically, the microprocessor is configured to continuously monitor live and neutral current levels by detecting such levels at a predetermined rate or ncy.

Typically, the microprocessor ates the monitored current levels to infer line impedance by means of Fourier transform calculations.

Typically, the microprocessor infers the line impedance criterion indicative of a neutral anomaly at a specific frequency.

In an embodiment, the specific frequency is 50Hz, but ions hereon are possible and expected.

In an embodiment, the microprocessor infers the line impedance criterion tive of a neutral anomaly by monitoring harmonics of the specific frequency, e.g. at 150Hz, lly, the microprocessor correlates the monitored current levels via a comparison between detected live and neutral current levels as a ratio to infer the line impedance criterion indicative of a neutral anomaly, i.e. a ratio between detected live and neutral ts.

In an embodiment, the microprocessor correlates the monitored current levels at different harmonics of the live mains electrical supply frequency, i.e. 50Hz and d harmonics.

Typically, the predetermined period of time comprises a range of between 10ms and 3000ms.

In an ment, the microprocessor is configured to infer the line impedance criterion indicative of a neutral anomaly according to a magnitude thereof compared to a duration thereof, a time-dependent line impedance criterion.

Typically, the microprocessor is configured to record and/or transmit red current levels, ed line impedance criteria and/or details of interruptions to the mains electrical supply.

According to a second aspect of the invention there is provided an anomalous neutral electrical protection breaker comprising: a untable housing for mounting as part of an electrical distribution board of an electrical installation; at least one live detector for ive onnection to a live mains electrical supply of the electrical installation; a neutral detector for operative interconnection to a MEN link of said electrical installation; an interrupter configured to selectively interrupt the mains electrical supply; and a microprocessor configured to: i) via the live or, continuously monitor the live mains electrical supply to detect live current level; ii) via the neutral detector, continuously monitor the MEN link to detect neutral current level; iii) correlate the monitored current levels to infer a line impedance criterion indicative of a l anomaly; and iv) if the inferred line impedance criterion is t for a predetermined period of time, interrupt the mains electrical supply by means of the interrupter.

Typically, the breaker comprises a DIN-mountable housing configured to be mounted in the electrical installation’s electrical distribution board, panel board, breaker panel, or electric panel, the detectors, interrupter and microprocessor housed within said housing. lly, the r comprises a live or for each phase of the live mains electrical supply, i.e. one live detector for a single-phase supply and three live detectors for a three-phase supply.

In an embodiment, the live detector comprises a current transformer.

In an embodiment, the l detector comprises a current transformer.

In an embodiment, the interrupter comprises a le breaker, such as an electromechanical circuit breaker, configured to selectively interrupt the mains electrical supply.

Typically, the upter is comprised of an existing residual current device (RCD) within the electrical installation’s electrical distribution board, said microprocessor arranged in signal communication therewith and configured to activate such RCD to interrupt the mains electrical supply.

In an ment, the microprocessor comprises a digital signal processor (DSP). lly, the microprocessor is ured to continuously monitor live and neutral t levels by detecting such levels at a predetermined rate or frequency.

Typically, the microprocessor correlates the monitored current levels to infer line impedance by means of Fourier transform calculations.

Typically, the microprocessor infers the line impedance criterion indicative of a l y at a specific frequency.

In an embodiment, the specific frequency is 50Hz, but variations hereon are le and expected.

In an embodiment, the microprocessor infers the line impedance criterion indicative of a neutral anomaly by monitoring harmonics of the specific frequency, e.g. at 150Hz, Typically, the microprocessor correlates the monitored current levels via a comparison between detected live and neutral current levels as a ratio to infer the line impedance criterion indicative of a neutral anomaly, i.e. a ratio between detected live and neutral currents.

In an embodiment, the microprocessor correlates the monitored current levels at different harmonics of the live mains ical supply frequency, i.e. 50Hz and related harmonics.

Typically, the predetermined period of time comprises a range of between 10ms and 3000ms.

In an embodiment, the microprocessor is configured to infer the line impedance ion indicative of a l anomaly according to a magnitude thereof compared to a on thereof, a time-dependent line nce ion.

Typically, the microprocessor is configured to record and/or transmit monitored current levels, inferred line impedance criteria and/or details of interruptions to the mains electrical supply. lly, the breaker is configured to be reset by means of bespoke tool to prevent unauthorised resetting for safety.

According to a third aspect of the invention there is provided a method of anomalous neutral electrical protection, said method comprising the steps of: continuously monitoring a live mains ical supply of an electrical installation to detect a live current level; continuously monitoring a MEN link of said electrical installation to detect neutral current level; correlating the monitored current levels to infer a line impedance criterion indicative of a neutral anomaly; and if the inferred line impedance criterion is present for a predetermined period of time, automatically interrupting the mains electrical supply by means of an interrupter; wherein said method is tically performed by a DIN- mountable r comprising at least one live detector for operative interconnection to the live mains electrical supply, a neutral detector for operative interconnection to the MEN link, an interrupter configured to selectively interrupt the mains electrical , and a microprocessor adapted to perform the steps of monitoring, correlating and interrupting.

According to a further aspect of the invention there is provided ous neutral electrical protection apparatus, an anomalous neutral electrical protection breaker, and a method of anomalous neutral electrical protection, substantially as herein described and/or illustrated.

BRIEF DESCRIPTION OF THE GS The description will be made with reference to the accompanying drawings in which: Figure 1 is a diagrammatic overview representation of a live mains electrical supply of an electrical installation; Figure 2 is a diagrammatic perspective-view representation of an embodiment of ous neutral electrical protection tus as a DIN-mountable breaker for the live mains electrical supply of the electrical installation of Figure 1, in accordance with s of the present invention; Figure 3 is a entation of a flow diagram of indicative method steps of an example method of anomalous neutral electrical protection, in accordance with aspects of the present invention; and Figure 4 is a diagrammatic electrical connection entation showing the interaction of the anomalous neutral electrical protection apparatus with the live mains ical supply of an electrical installation.

DETAILED DESCRIPTION OF EMBODIMENTS Further es of the present ion are more fully described in the following description of several nonlimiting ments thereof. This ption is included solely for the purposes of exemplifying the present invention to the skilled addressee. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above.

In the figures, incorporated to illustrate features of the example embodiment or embodiments, like reference numerals are used to identify like parts throughout.

Additionally, es, mechanisms and aspects nown and understood in the art will not be described in detail, as such features, mechanisms and aspects will be within the understanding of the skilled addressee.

With reference now to the accompanying figures, there is shown an example of an electrical supply for an electrical installation 16, such as a house, where mains electricity (such as live connection 14 and neutral connection .2) comes from a mains supply to a step-down transformer 8 before being supplied to said electrical installation 16, typically via a distribution board or panel board 14.1.

The present invention es for anomalous neutral electrical protection apparatus 10 which is typically connected within or proximate such distribution board 14.1, often where conventional breakers, electricity meters and residual current protection devices (RCDs) are mounted. lly, le earth connections 20.1 are common throughout as well, particularly in Multiple Earthed Neutral or MEN systems of earthing, which are common in countries like Australia, New Zealand and South Africa. Single-phase or threephase electrical supplies may be present, ements depending, with additional phases indicated in Figure 4 as ‘opt’ for optional.

In a general embodiment, apparatus 10 ses at least one live or 12 for operative interconnection to the live mains electrical supply 14 of an electrical installation 16, and a neutral detector 18 for operative interconnection to a MEN link 20 of said electrical installation 16. Typically, the apparatus 10 comprises a live detector 12 for each phase of the live mains electrical supply 14, i.e. one live detector for a single-phase supply and three live detectors for a three-phase supply. In one embodiment, the live detector(s) 12 and the neutral detector 18 comprise current transformers, but variations hereon are possible and within the scope of the present invention.

Apparatus 10 further includes an interrupter 22 which ured to selectively upt the mains electrical supply 14. Again, an embodiment may have an interrupter 22 per phase of the supply. In an embodiment, the interrupter comprises a suitable breaker, such as an electromechanical circuit breaker, configured to selectively interrupt the mains electrical supply. lly, the interrupter is comprised of an existing al current device (RCD) within the ical installation’s ical distribution board 14.1, the microprocessor 24 arranged in signal communication therewith and configured to activate such RCD to interrupt the mains electrical .

Importantly, apparatus 10 also es a suitable microprocessor 24 which is configured to, via the live detector 12, continuously r the live mains electrical supply 14 to detect live current level, and via the neutral detector 18, continuously monitor the MEN link 20 to detect neutral current level. Processor 24 is further ured to correlate the monitored current levels to infer a line impedance criterion indicative of a neutral anomaly, and if the inferred line impedance criterion is present for a predetermined period of time, interrupt the mains electrical supply 14 by means of the interrupter 22.

In an embodiment, the microprocessor comprises a digital signal processor (DSP). However, the skilled addressee is to appreciate that the microprocessor may include any suitable processor or microcontroller ured to receive input, perform logical and arithmetical operations on a suitable instruction set, and provide output, as well as transitory and/or non-transitory electronic storage.

Typically, the rocessor 24 is configured to continuously monitor such live and neutral current levels by detecting such levels at a ermined rate or frequency. In a typical example, the microprocessor 24 correlates the monitored current levels to infer line impedance by means of Fourier transform calculations, as is known in the art of signal processing.

Accordingly, the microprocessor 24 may infer the line impedance criterion indicative of a neutral anomaly at a specific frequency. In an embodiment, the specific ncy is 50Hz, but variations hereon are possible and expected. For example, such a specific frequency is typically a supply frequency, often being 50Hz in countries with MEN earthing practices. Additionally, the microprocessor 24 may be configured to infer the line impedance criterion indicative of a neutral anomaly by monitoring harmonics of the specific frequency, e.g. at 150Hz, etc.

Typically, the microprocessor 24 correlates the monitored current levels via a comparison between detected live and neutral current levels as a ratio to infer the line impedance ion indicative of a neutral anomaly, i.e. a ratio n detected live and neutral currents. Such a value ratio may be le and proportional to the t levels and is typically expressed in decibels (dB) as a ratio between active and neutral ts.

In an embodiment, the microprocessor 24 correlates the monitored current levels at different harmonics of the live mains electrical supply frequency, i.e. 50Hz and related harmonics.

Typically, the predetermined period of time in which the inferred line impedance ion must be present before interruption of the mains supply is in the range of between 10ms and 3000ms, but variations hereon are le, requirements depending.

In an embodiment, the microprocessor 24 is configured to infer the line impedance ion indicative of a neutral anomaly ing to a magnitude thereof compared to a duration thereof, a ependent line impedance criterion.

For e, a value ratio of 6dB for a predetermined time of 2500mS causes supply interruption, and a value ratio of 30dB for a predetermined time of 100mS causes supply interruption, or the like.

Typically, the microprocessor is configured to record and/or transmit monitored current levels, inferred line impedance criteria and/or details of interruptions to the mains electrical supply. For example, is a supply interruption occurs, the inferred value ratio may be recorded, the predetermined period may be recorded, etc. such recording and reporting typically finds application in safety audits and fault-finding.

As shown in Figure 2, the apparatus 10 typically comprises a untable housing 26 configured to be mounted in the electrical installation’s electrical distribution board 14.1 with the ors 12 and 18, interrupter 22 and microprocessor 24 housed within said g 26, as required.

The interrupter 22 may also be configured to be reset by means of bespoke tool to prevent unauthorised resetting for safety purposes, i.e. if an earth-neutral fault occurs which causes supply interruption by apparats 10, supply cannot be ed without authorisation.

Figure 3 shows an example of an ated method 30 of anomalous neutral electrical protection. The method 30 generally comprises the steps of continuously monitoring the live mains electrical supply of the electrical installation to detect a live current level, continuously monitoring the MEN link of said electrical installation to detect neutral current level, and correlating the monitored t levels to infer a line impedance criterion tive of a neutral anomaly.

If the inferred line impedance criterion is present for a predetermined period of time, the method includes the step of automatically interrupting the mains electrical supply by means of the upter, n such a method 30 is typically automatically performed by a DIN-mountable breaker comprising at least one live detector for operative interconnection to the live mains electrical supply, a neutral detector for operative interconnection to the MEN link, an interrupter configured to ively interrupt the mains electrical supply, and a microprocessor adapted to perform the steps of ring, correlating and interrupting, as described above.

As described above, such broken neutral detection is broadly achieved by monitoring active (L1, L2, L3) and neutral (N) currents on a consumer meter side before the MEN link of an electrical installation. Such ring is typically performed by means of current transformers (CT) or other t monitoring devices. The monitored t information is applied to a digital signal processor (DSP), which utilises various algorithms as broadly described to filter and detect current magnitude on all input lines (L1, L2, L3 and N). In one embodiment, 1st and 3rd harmonic energy are detected and a magnitude of the outputs is applied to an algorithm to allow the detection of differences in the current magnitudes. This information is then used to calculate an effective neutral impedance.

For low impedances, the algorithm analyses the information until a time and value threshold is met, and at this point the circuitry triggers the external residual current devices (RCD's) by applying a mismatched current from active to earth. For high value neutral impedance (Neutral Line Open) the algorithm has a large output and rs the RCD's in less than 100mS, for e.

Protection to a consumer with this approach ensures that no high earth voltage can exist under broken or high neutral impedance . The monitoring of t ts before the MEN enables the real time calculation of neutral impedance. The interrupter typically operates or trips an existing RCD within the existing switchboard enclosure. The apparatus 10 also uses low power during operation so that there is minimal impact on supply costs. tus 10 may also provide external control feedback and reporting via wireless interface such as Bluetooth or the like. Apparatus 10 may further e an internal mechanism for calibration of installation earth impedance, such as measurement of line impedance during installation, which is then saved as a reference for future calculations by the processor, or the like.

Applicant believes it particularly ageous that the present invention provides for apparatus 10, typically as a DIN-mountable circuit breaker, which is able monitor for neutral anomalies on an electrical installation’s supply and to automatically interrupt said supply if a potentially dangerous or harmful anomaly is detected.

Optional embodiments of the present invention may also be said to broadly consist in the parts, elements and features referred to or indicated herein, individually or collectively, in any or all combinations of two or more of the parts, elements or es, and wherein specific integers are mentioned herein which have known equivalents in the art to which the ion relates, such known equivalents are deemed to be incorporated herein as if individually set forth. In the example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in , as such will be y understood by the skilled addressee.

The use of the terms "a", "an", "said", "the", and/or similar referents in the context of describing various ments (especially in the context of the claimed subject matter) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and ining" are to be construed as openended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. No language in the specification should be construed as indicating any non-claimed subject matter as essential to the practice of the claimed subject matter.

Spatially ve terms, such as "inner," "outer," "beneath," "below," "lower," "above," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or e(s) as rated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or es would then be oriented "above" the other elements or features. Thus, the example term "below" can encompass both an orientation of above and below.

The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially ve descriptors used herein interpreted accordingly.

It is to be appreciated that reference to "one example" or "an example" of the ion, or similar exemplary ge (e.g., "such as") herein, is not made in an exclusive sense. Various substantially and specifically practical and useful exemplary embodiments of the d subject matter are described herein, textually and/or cally, for carrying out the claimed subject matter.

Accordingly, one example may exemplify certain aspects of the invention, whilst other aspects are exemplified in a different example. These examples are intended to assist the skilled person in performing the invention and are not intended to limit the overall scope of the invention in any way unless the context clearly indicates otherwise. Variations (e.g. cations and/or enhancements) of one or more embodiments described herein might become nt to those of ordinary skill in the art upon reading this application. The inventor(s) expects skilled artisans to employ such ions as appropriate, and the inventor(s) intends for the claimed subject matter to be practiced other than as specifically described herein.

Any method steps, processes, and operations bed herein are not to be construed as necessarily requiring their mance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

Claims (37)

1. Anomalous neutral electrical protection apparatus comprising: at least one live detector for operative interconnection to a live mains electrical supply of an electrical installation; a neutral detector for operative interconnection to a MEN link of said electrical installation; an interrupter configured to selectively interrupt the mains electrical supply; and a microprocessor configured to: i) via the live detector, continuously monitor the live mains electrical supply to detect live t level; ii) via the neutral detector, continuously monitor the MEN link to detect l current level; iii) correlate such monitored current levels to infer a line impedance criterion indicative of a neutral anomaly; and iv) if the inferred line impedance ion is present for a predetermined period of time, interrupt the mains electrical supply by means of the interrupter.

2. Apparatus of claim 1, which comprises a DIN-mountable housing configured to be mounted in the ical lation’s electrical bution board, panel board, breaker panel, or electric panel, the detectors, interrupter and microprocessor housed within said housing.

3. Apparatus of either of claims 1 or 2, which ses a live detector for each phase of the live mains electrical supply, i.e. one live detector for a single-phase supply and three live detectors for a three-phase supply.

4. Apparatus of any of claims 1 to 3, wherein the live detector comprises a current transformer.

5. Apparatus of any of claims 1 to 4, wherein the neutral or comprises a current transformer.

6. Apparatus of any of claims 1 to 5, wherein the interrupter comprises a suitable breaker, such as an electromechanical circuit breaker, configured to selectively interrupt the mains electrical supply.

7. tus of any of claims 1 to 6, wherein the upter is comprised of an existing al current device (RCD) within the electrical installation’s electrical bution board, said microprocessor arranged in signal communication therewith and configured to activate such RCD to upt the mains electrical supply.

8. Apparatus of any of claims 1 to 7, n the microprocessor comprises a digital signal processor (DSP).

9. Apparatus of any of claims 1 to 8, wherein the microprocessor is configured to continuously monitor live and neutral current levels by ing such levels at a predetermined rate or frequency.

10. Apparatus of any of claims 1 to 9, wherein the microprocessor correlates the monitored current levels to infer line impedance by means of Fourier transform calculations.

11. Apparatus of any of claims 1 to 10, wherein the microprocessor infers the line impedance criterion indicative of a neutral anomaly at a specific frequency.

12. Apparatus of claim 11, n the specific frequency is 50Hz.

13. Apparatus of either of claims 11 or 12, wherein the microprocessor infers the line impedance criterion indicative of a neutral anomaly by monitoring harmonics of the specific frequency, e.g. at 150Hz.

14. Apparatus of any of claims 1 to 13, wherein the microprocessor correlates the monitored current levels via a comparison n detected live and neutral current levels as a ratio to infer the line impedance criterion indicative of a neutral anomaly, i.e. a ratio between detected live and neutral currents.

15. Apparatus of any of claims 1 to 14, wherein the microprocessor ates the red current levels at different harmonics of the live mains electrical supply frequency, i.e. 50Hz and related harmonics.

16. Apparatus of any of claims 1 to 15, wherein the predetermined period of time ses a range of between 10ms and 3000ms.

17. Apparatus of any of claims 1 to 16, wherein the microprocessor is configured to infer the line impedance ion tive of a neutral anomaly according to a magnitude thereof compared to a duration thereof, a timedependent line impedance criterion.

18. Apparatus of any of claims 1 to 17, wherein the microprocessor is configured to record and/or transmit monitored t levels, inferred line nce criteria and/or details of interruptions to the mains electrical supply.

19. An anomalous neutral electrical protection r comprising: a DIN-mountable housing for mounting as part of an electrical bution board of an electrical installation; at least one live detector for operative interconnection to a live mains electrical supply of the ical lation; a neutral detector for operative interconnection to a MEN link of said electrical installation; an interrupter configured to selectively interrupt the mains electrical ; and a microprocessor configured to: i) via the live detector, continuously monitor the live mains electrical supply to detect live current level; ii) via the neutral detector, uously monitor the MEN link to detect neutral current level; iii) correlate the monitored current levels to infer a line impedance criterion indicative of a neutral anomaly; and iv) if the inferred line impedance criterion is present for a predetermined period of time, interrupt the mains electrical supply by means of the interrupter.

20. The breaker of claims 19, which comprises a live detector for each phase of the live mains electrical supply, i.e. one live or for a single-phase supply and three live detectors for a three-phase .

21. The breaker of either of claims 19 or 20, wherein the live detector comprises a current transformer.

22. The breaker of any of claims 19 to 21, wherein the neutral detector comprises a current transformer.

23. The breaker of any of claims 19 to 22, wherein the interrupter comprises a le breaker, such as an electromechanical circuit breaker, configured to selectively interrupt the mains electrical supply.

24. The breaker of any of claims 19 to 23, wherein the interrupter is comprised of an existing al t device (RCD) within the electrical installation’s electrical distribution board, said microprocessor ed in signal communication therewith and configured to activate such RCD to interrupt the mains electrical supply.

25. The r of any of claims 19 to 24, wherein the microprocessor comprises a digital signal processor (DSP).

26. The breaker of any of claims 19 to 25, wherein the microprocessor is configured to continuously monitor live and neutral current levels by detecting such levels at a predetermined rate or frequency.

27. The breaker of any of claims 19 to 26, wherein the microprocessor correlates the monitored current levels to infer line impedance by means of Fourier transform calculations.

28. The breaker of any of claims 19 to 27, wherein the microprocessor infers the line impedance ion indicative of a neutral anomaly at a specific frequency.

29. The breaker of claim 28, wherein the specific frequency is 50Hz.

30. The breaker of either of claims 28 or 29, wherein the microprocessor infers the line impedance ion indicative of a l anomaly by monitoring harmonics of the specific ncy, e.g. at 150Hz, etc.

31. The breaker of any of claims 19 to 30, wherein the microprocessor correlates the monitored current levels via a comparison between detected live and neutral current levels as a ratio to infer the line impedance criterion indicative of a l anomaly, i.e. a ratio between detected live and neutral currents.

32. The breaker of any of claims 19 to 31, wherein the microprocessor correlates the monitored t levels at different harmonics of the live mains electrical supply frequency, i.e. 50Hz and related harmonics.

33. The breaker of any of claims 19 to 32, wherein the predetermined period of time ses a range of between 10ms and 3000ms.

34. The breaker of any of claims 19 to 33, wherein the microprocessor is configured to infer the line impedance criterion indicative of a neutral y according to a magnitude thereof compared to a duration thereof, a pendent line impedance criterion.

35. The breaker of any of claims 19 to 34, wherein the microprocessor is configured to record and/or transmit monitored current levels, inferred line impedance criteria and/or s of interruptions to the mains electrical supply.

36. The breaker of any of claims 19 to 35, wherein the breaker is configured to be reset by means of bespoke tool to prevent unauthorised resetting for safety.

37. A method of anomalous l electrical protection, said method comprising the steps of: continuously monitoring a live mains electrical supply of an electrical installation to detect a live current level; continuously monitoring a MEN link of said electrical installation to detect neutral current level; correlating the monitored current levels to infer a line impedance criterion indicative of a neutral anomaly; and if the inferred line impedance criterion is t for a predetermined period of time, automatically interrupting the mains electrical supply by means of an interrupter; wherein said method is automatically performed by a DIN- mountable breaker comprising at least one live detector for ive interconnection to the live mains electrical , a neutral detector for operative interconnection to the MEN link, an interrupter configured to selectively interrupt the mains electrical supply, and a microprocessor adapted to perform the steps of ring, correlating and interrupting.