Electric meter tamper detection via modified current analysis

Abstract

A tamper detection system for an electrical power meter is illustrated and described. The tamper detection system comprises a current sensor module operable to measure at least a portion of a load current between a line input and a load output of the electrical power meter. The system also has a load current modifier operable to modify the load current. A processor is configured to receive load current data from the current sensor module and, based at least in part on received load current and modified load current data, to determine a tamper or fault state of the meter.

Description

[0001] Electric Meter Tamper Detection via Modified Current Analysis

[0002] FIELD OF INVENTION

[0003] The present disclosure is in the field of electrical power metering systems, and relates particularly, to an electric meter tamper detection system using modified current analysis. The present disclosure also relates to a tamper detection method for an electric meter using modified current analysis.

[0004] BACKGROUND TO INVENTION

[0005] Electrical power meters are used to measure power usage, particularly for creating accurate billing information. Modern power meters can transmit / receive data, such as power usage data, which can then be used, at least in part, to charge end-users for the power that they consume. Electrical meters typically include one or more current sensors, such as a current sensing transformer and a metrology module for processing measurements of voltage and current.

[0006] End-users may tamper with their electrical power meter to fool their electricity provider into billing them for less energy than they have actually used. A not-uncommon tampering method involves breaking a meter’s seal, opening its housing (possibly even while a meter is powered on and still carrying end-user load current) and unplugging, shorting, or adding a series or parallel resistor to the current sensor or the connectors / wires thereof. An unplugged or shorted current sensor wire is normally indistinguishable from the end-user using no power. The addition of a series or parallel resistor in the wires that connect a current sensor to the metrology module can be especially problematic because the meter will still detect current flow, but only a fraction of the actual load current. This is also the case if an end-user shorts the line side of their meter directly to the load side, thus bypassing the meter such that a small fraction of the load current will still flow through the meter and be measured, making it seem accurate to the electricity provider, even though the meter is not measuring all of the end-user’s energy usage.

[0007] Electrical meters may also suffer from manufacturing defects and other faults, which may only become apparent after the meter has been dispatched / installed. The detection often involves a site / home visit by an engineer to determine the fault and to either fix / replace the meter. Another means of tampering, or source of fault(s) is the loss or corruption of meter calibration data.

[0008] It is therefore desirable to implement at least one of the following:

[0009] 1 ) Detection of electricity meter tampering by unplugged, shorted, overburdened, or voltage-divided current sensor(s) or connections / wires thereof;

[0010] 2) Detection of current sensor faults (e.g. opens / shorts) due to manufacturing defects that occur after a meter has been supplied;

[0011] 3) Detection of electricity service tampering by shorted line-side to load-side connectors of the meter (bypassing the meter); and

[0012] 4) Detection of the loss or corruption of meter calibration data.

[0013] It is therefore an aim of at least one embodiment of at least one aspect of the present disclosure to obviate or at least mitigate at least one of the above identified shortcomings of the prior art.

[0014] SUMMARY OF INVENTION

[0015] The present disclosure is in the field of electrical power metering systems, and relates particularly to an electric meter tamper detection system using modified current analysis.

[0016] According to a first aspect of the disclosure, there is provided a tamper detection system for an electrical power meter, the system comprising: a current sensor module operable to measure at least a portion of a load current between a line input and a load output of the electrical power meter; and a load current modifier operable to modify the load current.

[0017] The tamper detection system may comprise a processor. The processor may be configured to receive load current data from the current sensor module. The processor may be configured to receive modified load current data from the current sensor module.

[0018] The processor may be configured, based at least in part on received load current and modified load current data, to determine a tamper or fault state of the meter. The processor may be configured to transmit the received load current data to a further device, such as a computing device, a networked device, a server, or the like.

[0019] In use, the tamper detection system modifies the load current and may determine whether or not the meter has been tampered with, or has a fault. In some embodiments, the further device may be configured or operable to determine whether or not the meter has been tampered with, or has a fault.

[0020] The processor may be configured to determine the tamper or fault state from a plurality of tamper / fault states. The further device may be configured to determine the tamper or fault state from a plurality of tamper / fault states.

[0021] The processor may receive load current data, which may include any modification thereto caused by the load current modifier.

[0022] The current sensor module may be located within, or integrated with the electrical meter or separately formed from the electrical meter, or a combination thereof.

[0023] The current sensor module may comprise one or more current sensor elements, such as current sensing transformer(s), shunt current sensor(s), an inductor or coil such as a Rogowski coil, and the like. The, or each current sensor element may be configured to measure at least a portion of the load current.

[0024] In some embodiments, the current sensor module may be configured to measure at least a portion of the load current directly and in other embodiments, the current sensor module may be operable to measure at least a portion of the load current by obtaining data from the electrical meter.

[0025] The current sensor module may be configured to receive and / or transmit load current data to / from the meter by a wired connection to the meter or through a wireless connection, such as by radio or optical communication, or the like, or in any suitable way. The tamper detection system may comprise a communication unit. The communication unit may be configured for transmitting and / or receiving data from the electrical meter. The communication unit may be operable to send and / or receive data to / from the further device, which may include at least one of: load current data and voltage data, or any suitable data from the tamper detection device and / or the electrical meter.

[0026] The electrical meter may comprise a housing. The electrical meter may comprise one or more, or a plurality of line inputs and one or more, or a plurality of load outputs. The, or each line input may have a meter power line to a corresponding load side output, and in some embodiments, the, or each meter power line is a phase line of the electrical power supply.

[0027] The processor may be configured to control the load current modifier. The processor may be configured to activate and deactivate the load current modifier.

[0028] The load current modifier may be located within, or integrated with the electrical meter or separately formed. The load current modifier may be located within the housing of the electrical meter. The processor may be located within, or integrated with the electrical meter or separately formed. The processor may be located within the housing of the electrical meter.

[0029] The load current modifier may be connectable or connected to at least one meter power line to modify the current flow thereof, or to a plurality of meter power lines to modify the current flow thereof.

[0030] The load current modifier may comprise a plurality of terminals. The terminals may be for connecting the load current modifier to the meter power line(s). The terminals may be connectable to a first meter power line and a second meter power line. The terminals may be internal connections within the meter, such as printed circuit board (PCB) connectors / tracks or the like.

[0031] The meter may comprise a plurality of voltage sense lines, connectable to at least one, or a plurality of meter power lines. The at least one, or plurality of voltage sense lines may include one or more, or a plurality of load side voltage sense lines configured to measure a voltage at or adjacent to the load output(s) of the meter. The voltage sense lines may be arranged to measure line-line voltage between two meter power lines. The at least one, or plurality of voltage sense lines may include one or more, or a plurality of line side voltage sense lines configured to measure a voltage at or adjacent to the line input(s) of the meter.

[0032] The load current modifier may be connectable or connected at or adjacent to the load side output. The load current modifier may be connectable or connected at or adjacent to the line side input. The terminals of the load current modifier may be connectable or connected to the plurality of voltage sense lines, or to the plurality of load side voltage sense lines and / or the plurality of line side voltage sense lines.

[0033] The load current modifier may comprise a first plurality of terminals and a second plurality of terminals. The first terminals may be connectable or connected to a first plurality of voltage sense lines and the second terminals may be connectable or connected to a second plurality of voltage sense lines. The first plurality of voltage sense lines may be the line side voltage sense lines. The second plurality of voltage sense lines may be the load side voltage sense lines. The load current modifier may be operable to selectively activate current flow via the first terminals, the second terminals, or combination thereof.

[0034] The terminals of the load current modifier may be connectable to one or more, or a plurality of electrical supply lines external to the meter. The terminals of the load current modifier may be connectable to the electrical supply lines downstream of the load output(s) of the meter. In some embodiments, the load current modifier may be connectable remote from the meter. The terminals of the load current modifier may be connectable to an electrical terminal housing the plurality of electrical supply lines, such as a mains socket, or the like.

[0035] The load current modifier may be operable to modify at least one of: the amplitude / rms value, phase (relative to the voltage), or any suitable parameter of the load current.

[0036] The load current modifier may be operable to increase or decrease the amplitude / rms value of the load current.

[0037] The load current modifier may be configurable or configured in one or more current modes, or operable between two or more current modes. A first current mode may be a current sink mode, in which the load current modifier is configured such that additional power is drawn through the current sensor module. A second current mode may be a current source mode, in which the load current modifier provides power to the load side, which effectively reduces the current flow drawn from the electrical power supply via the line side.

[0038] In a third, current loop mode, the load current modifier may be configured to draw power in a loop formed by the line side to the load current modifier to the load side to the current sensor module back to the line side.

[0039] The load current modifier may be configured to provide the modified current flow component at least partially within the meter, or entirely within the meter.

[0040] The load current modifier may comprise a switching device for selectively activating and / or controlling the modification to the load current. The switching device may be or include one or more thyristors, TRIACs, transistors, relays (e.g. solid state and / or mechanical relay), or the like. The load current modifier may comprise one or more active or passive components, which may include the switching device, and one or more resistors, inductors, transformers, further switching devices, transistors and / or capacitors, for modifying the load current.

[0041] The switching device may be configured to switch or control the flow of current across the terminals of the load current modifier.

[0042] The tamper detection system may be operable to modify the power factor of the load downstream of the line input(s) of the meter, or downstream of the load output(s) of the meter. In some embodiments, the load current modifier may be operable to modify the power factor of the load. The load current modifier may be configured to activate power flow through a reactive load, such as a capacitive or inductive load, to modify the power factor of the load. In some embodiments, the load current modifier may be operable to both modify the load current for tamper / fault detection and to modify the power factor of the load.

[0043] The processor may be configured to determine when the load current is in a first, unmodified state. The first, unmodified state may include one or more or a plurality of unmodified load current periods. The first, unmodified state may include or may be a steady state or a substantially steady state. Modification to the load current by the load current modifier may be a second, modified current state. The processor may be configured to determine the first, unmodified state using the received load current data. In the first, unmodified state the load current may be within a predetermined threshold, such as varying by about 5% or less, or about 2% or less, or about 1 % or less. The processor may be configured to modify the load current at least once within a set time period when the load current is in the first, unmodified state. The processor may be configured to modify the load current automatically within a time period when the load current is in the first, unmodified state. It will be understood that the number of load current modifications carried out within a given time frame could be predetermined or selected, such as once per day, or monthly, or as required. The processor may be operable to run a load current modification automatically and / or in response to user input.

[0044] The load current modifier may be configured to modify the load current for any timed duration or any number of line cycles, which may include one or more or a plurality of fractional line cycles. The load current modifier may be configured to modify the load current for one or more cycles of the supply, optionally for 100 or fewer cycles, optionally for 10 or fewer cycles, optionally for 5 or fewer cycles, optionally for substantially one cycle, optionally for between 1 / 10 of a cycle and 1 cycle, optionally for between 1 and 100 cycles, optionally between 1 and 10 cycles.

[0045] The processor may be configured to obtain a plurality of samples of the first, unmodified state current to determine when to apply the modified current to carry out the tamper detection. The processor may be configured to wait a predetermined interval between obtaining the samples of the first, unmodified state current. The processor may be configured to obtain a plurality of samples of the modified current. The processor may be configured to average obtained samples, or to carry out any required data processing thereto.

[0046] The processor may be configured to measure the difference between the modified current and the first, unmodified state load current. The processor may be configured to transmit first, unmodified state load current data to the further device. The further device may be configured to measure the difference between the modified current and the first, unmodified state load current. The parameters to be compared may include at least one of: amplitude / rms values, phase (relative to voltage), or any suitable parameters. The processor may be configured to obtain or store an expected difference value between the modified current and the first, unmodified state current. The processor may be configured to transmit the expected difference value between the modified current and the first, unmodified state current to the further device. The processor may be configured to compare the measured difference and the expected difference of the modified and first, unmodified state load currents. The further device may be configured to compare the measured difference and the expected difference of the modified and first, unmodified load currents. The processor may be configured to determine the tamper or fault state based on the comparison of the measured difference and the expected difference of the modified and first, unmodified state load currents. The further device may be configured to determine the tamper or fault state based on the comparison of the measured difference and the expected difference of the modified and first, unmodified state load currents.

[0047] The processor or the further device may be configured to adjust the expected current difference over time. In some embodiments this may at least partially compensate for component degradation, such as the drift in capacitor value overtime as the capacitor ages. This capacitor example is merely for illustrative purposes, and it will be appreciated that other compensation techniques may be readily employed.

[0048] The tamper or fault states may include a flag that a tamper or fault is possibly present.

[0049] The tamper or fault state may include at least one of:

[0050] (i) A no tamper / fault state, which may be when the measured current difference is equal to the expected current difference or within a tolerance (e.g. within 5%, or 2%, or 1 %);

[0051] (ii) A first tamper / fault state, which may be when the measured current difference is zero or within a tolerance (e.g. within 5%, or 2%, or 1%). The processor or the further device may infer at least one of: that the sensor module (or at least one sensor element thereof) has an open circuit or short circuit tamper / fault, manufacturing fault, or loss / corruption of meter calibration data.

[0052] (iii) A second tamper / fault state, which may be when the measured current difference is non-zero and less than the expected current difference (e.g. within 5%, or 2%, or 1%). The processor or the further device may infer that at least one of: the possibility of an added parallel / series component (e.g. a resistor) to the sensor module (or to at least one sensor element thereof); one or more line inputs of the meter connected directly to one or more of the load outputs of the meter to bypass the meter; or loss / corruption of meter calibration data.

[0053] (iv) A third tamper / fault state, which may be when the measured current difference is nonzero and more than the expected current difference (e.g. within 5%, or 2%, or 1%). The processor or the further device may infer at least one of: loss / corruption of meter calibration data.

[0054] The processor may be configured to determine a plurality of, or all of the tamper / fault states. The processor may be configured to flag a tamper / fault state with an inference of the possible or likely cause of the tamper / fault state. The further device may be configured to determine a plurality of, or all of the tamper / fault states. The further device may be configured to flag a tamper / fault state with an inference of the possible or likely cause of the tamper / fault state.

[0055] The numbering of the tamper / fault states is purely for explanatory purposes and does not attribute a preferred hierarchy or required number of tamper / fault states.

[0056] The tamper detection system may be configured to transmit the determined tamper / fault state(s) to the further device.

[0057] The tamper detection system may comprise the electrical power meter. The tamper detection system may be integrated with the electrical power meter or separately formed from the meter or combination thereof.

[0058] The processor may be configured to autonomously modify the load current and to transmit current data to the further device. The processor may be configured to autonomously carry out tamper detection and to autonomously determine the one or more tamper / fault states. The processor may be configured to autonomously transmit, send, or otherwise report the tamper / fault state to the further device. The further device may be configured to autonomously determine the tamper / fault state.

[0059] The current sensor module may be operable to measure the load current through one or more, or two or more meter power lines. The load current modifier may be operable to modify the load current through each meter power line. The, or each current sensor elements may be associated with at least one meter power line. The processor or the further device may be operable to determine the one or more tamper / fault states associated with a current sensor element.

[0060] The tamper detection system may be separate from the meter.

[0061] The tamper detection system may be formed in a discrete tamper detection device. The tamper detection device may be separate to the meter.

[0062] The tamper detection device may include one or more casings for the components thereof. The one or more casings may each be separate from the meter. The tamper detection system may be portable. The tamper detection device may be portable. The tamper detection system may be a hand-held system. The tamper detection device may be implemented in one or more hand-held casings. The tamper detection system, or the tamper detection device may be configured for carrying by hand.

[0063] The tamper detection system may comprise a housing, which may be the meter housing, or the casing(s) of the tamper detection device.

[0064] The current sensor module may be located within a casing of the tamper detection device. The load current modifier may be located within a casing of the tamper detection device. The processor may be located with a casing of the tamper detection device.

[0065] The electrical power meter may comprise at least one load current switch operable to interrupt the supply of current between the line input and the load output of the meter.

[0066] The tamper detection system may include one or more voltage sensors, which may obtain voltage measurements from the plurality of voltage sense lines. The one or more voltage sensors may be located within the meter.

[0067] The tamper detection device may be operable to obtain voltage data from the one or more voltage sensors of the meter. The tamper detection device may be operable to transmit the voltage data from the meter to the further device.

[0068] The tamper detection system may comprise a power supply. The power supply may be drawn from the plurality of voltage sense lines, optionally the line side voltage sense lines.

[0069] The tamper detection device may comprise a power supply, which may include a battery or the like.

[0070] The tamper detection system, or the electrical meter, or the further device may be configured to amend the total metered energy usage to account for power consumption of the tamper detection system, or the load current modifier thereof. This may include subtracting at least some of the energy consumed by the tamper detection system from the total metered energy usage.

[0071] It will be understood that in other examples, any one or combination of the components of the system could be located within the electrical meter and any one or combination of components could be separate to the electrical meter.

[0072] According to a second aspect of the disclosure, there is provided a tamper detection method for an electrical power meter, the method comprising: measuring at least a portion of a load current between a line input and a load output of the electrical power meter; modifying the load current; measuring the modified load current.

[0073] The method may comprise determining, based at least in part on the measured load current and measured modified load current, a tamper or fault state of the meter.

[0074] The method may comprise any further steps based on this disclosure and the steps of the method may be carried out in any order, unless the context provides otherwise.

[0075] According to a third aspect of the disclosure, there is provided an electrical power meter comprising a tamper detection system, the tamper detection system comprising: a current sensor module operable to measure at least a portion of a load current between a line input and a load output of the electrical power meter; and a load current modifier operable to modify the load current.

[0076] According to a fourth aspect of the disclosure, there is provided a tamper detection system for an electrical power meter, the system comprising: a tamper detection device comprising: a current sensor module operable to measure at least a portion of a load current between a line input and a load output of the electrical power meter; and a load current modifier operable to modify the load current.

[0077] The tamper detection device may be separate to the electrical power meter.

[0078] According to a fifth aspect of the disclosure, there is provided a tamper detection kit for an electrical power meter, the kit comprising: a current sensor module operable to measure at least a portion of a load current between a line input and a load output of the electrical power meter; and a load current modifier operable to modify the load current.

[0079] One or more of the components of the kit may be located in the same housing or casing. One or more of the components of the kit may be separate, discrete components of the kit.

[0080] The above summary is intended to be merely examples and non-limiting. The disclosure includes one or more corresponding aspects, embodiments or features in isolation or in various combinations whether or not specifically stated (including claimed) in that combination or in isolation. It should be understood that features defined above in accordance with any aspect of the present disclosure or below relating to any specific embodiment of the disclosure may be utilized, either alone or in combination with any other defined feature, in any other aspect or embodiment or to form a further aspect or embodiment of the disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0081] These and other aspects of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, wherein:

[0082] Figure 1 depicts an example of a tamper detection system for an electrical power meter, according to aspects of the invention;

[0083] Figure 2 depicts a further example of a tamper detection system for an electrical power meter, according to aspects of the invention;

[0084] Figure 3 depicts another example of a tamper detection system for an electrical power meter, according to aspects of the invention;

[0085] Figure 4 depicts a yet further example of a tamper detection system, which is separate from the electrical power meter, according to aspects of the invention;

[0086] Figure 5 depicts a schematic of the load current modifier of Figure 1 configured in a current sink mode;

[0087] Figure 6 depicts a schematic of the load current modifier of Figure 2 configured in a current source mode;

[0088] Figure 7 depicts a schematic of the load current modifier of Figure 3 configured in a current loop mode; and

[0089] Figure 8 depicts a schematic of the load current modifier of Figure 5, with a capacitor in place of the load resistor for power factor correction.

[0090] DETAILED DESCRIPTION OF DRAWINGS

[0091] Figure 1 shows a tamper detection system 100 for an electrical power meter 102, which in the examples shown here is an ANSI form 2 meter (the most common residential meter in the US). The system 100 comprises a current sensor module 104 operable to measure the load current 106 between two line inputs 108 and two load outputs 110 of the electrical power meter 102. Two phase lines L1 , L2 and a neutral line 1 12 are present within the split phase system shown here, and no current measurements are carried out on the neutral line 112, however it will be understood that in other embodiments, any single-phase or polyphase measurement system could be employed, and the specific currents that are measured may be different to those described and shown here.

[0092] The tamper detection system 100 includes a load current modifier 114 operable to modify the load current 106, and the reason for the modification is to determine whether or not the meter 102 has been tampered with, or has a fault. The system 100 relies on analysis of a normal load current 106, representing power consumed by the end-user (or power provided back to the utility provider by the end-user) and a deliberately modified load current 106, to determine if tampering has taken place, or if a fault is present.

[0093] In the examples of Figure 1 to 8, the system 100 includes a processor 116 configured to receive load current data from the current sensor module 104, which includes any modification created by the load current modifier 114. Based at least in part on the received load current and modified load current data, the processor 116 determines one or more tamper or fault states of the meter 102. However, in other embodiments, the processor 116 may be configured to transmit load current data to a further device, such as a computing device, networked device, or server, or the like, and the determination of the one or more tamper or fault states of the meter 102 is carried out by the further device.

[0094] The processor 116 can take any suitable form, such as an embedded processor, and in some examples the processor 116 may be considered a measurement and analysis unit of the system 100.

[0095] In the embodiments illustrated and described here, the tamper detection system 100 enables the following tamper or faults to be identified:

[0096] 1) Detection of electricity meter 102 tampering by unplugged, shorted, overburdened, or voltage-divided current sensor(s) or connections / wires thereof;

[0097] 2) Detection of current sensor faults (e.g. opens / shorts) due to manufacturing defects that occur after a meter 102 has been supplied;

[0098] 3) Detection of electricity service tampering by shorted line-side to load-side connectors of the meter 102 (bypassing the meter); and

[0099] 4) Detection of the loss or corruption of meter calibration data.

[0100] It will be understood that in other examples, the system 100 may detect fewer or more tamper / fault states.

[0101] The processor 116 is configured to determine the tamper / fault state from a plurality of tamper / fault states.

[0102] The main differences between the examples of Figures 1 to 3 are in the configuration of the load current modifier 114, which will be explained in detail below. In the examples shown in Figures 1 to 3, the tamper detection system 100 is located within, and integrated with the meter 102, whereas in the embodiment of Figure 4, the tamper detection system 200 is separate to the meter 102. Like reference signs in Figure 4 have been used, incremented by 100 over the examples of Figures 1 to 3. It will be understood that in some examples, the tamper detection system 100 may be partly integrated with the meter 102, such that some components thereof are separate to the meter 102.

[0103] In Figures 1 to 3, the current sensor module 104 is located within and integrated with the electrical meter 102. In the example of Figure 4, the current sensor module 204 is separately formed from the meter 102 (and is separate to the meter’s current sensor module 104), and can obtain load current data from the meter 102.

[0104] In the examples of Figure 1 to 3, the current sensor module 104 comprises two current sensing transformers 104a, which are examples of current sensing elements. In other examples, the current sensor module 104 could comprise any suitable current sensing element, such as shunt element(s), inductors, coils, Rogowski coils, or the like, and the use of transformers is purely for example purposes. Each current sensor element 104a is configured to measure a portion of the load current 106.

[0105] In the meter- integrated examples of Figures 1 to 3, the current sensor module 104 measures the load current 106 directly and in the example of Figure 4, the current sensor module 204 is separate from the meter 102 and measures the load current 106 by obtaining data from the electrical meter 102 during tamper detection.

[0106] In the example of Figure 4, the current sensor module 204 is configured to obtain load current data from the meter 102 by a wireless connection 207a, such as by radio, controlled by a communication unit 207 of the system 200. The wireless connection 207a can also obtain current / voltage data from the meter 102 to the system 200. Many wired / wireless methods of obtaining the data can be used.

[0107] In some embodiments, the current sensor module 204 shown in Figure 4 could measure the load current 106 directly rather than via the meter 102. In some examples it may therefore be desirable for the communication unit 207 to be configured for sending and / or receiving current data to / from the meter 102, and optionally to / from the further device. It will be appreciated that any suitable way of sharing data between the system 200, the meter 102 and the further device can be implemented.

[0108] Turning back to the examples of Figure 1 to 3, the electrical meter 102 includes a housing 1 18 for the components thereof. The plurality of line inputs 108 and load outputs 110 will be a connector on the housing 1 18, with no connection to the neutral line 112. In other examples, the neutral line may also be connected through the meter 102 as per the phase lines (L1 , L2). Each line input 108 has a meter power line 120 to a corresponding load output 1 10. Each meter power line 120 is a phase line (L1 , L2) of the electrical power supply, which excludes the neutral line 1 12. It will be understood that in other embodiments, it may be desirable to implement a different arrangement in this respect, and the two-phase system shown here is purely exemplary.

[0109] The current sensor module 104 is operable to measure the total load current 106 (the combination of the current through each of two meter power lines 120) because of the configuration of the current sensing transformers 104a, and the load current modifier 1 14 is operable to modify the individual load current through each meter power line 120, which therefore modifies the total load current 106. Each current sensing transformer 104a is associated with a meter power line 120. In other examples, the current sensor module 104 may measure the individual load current through each meter power line 120 which will then be summed to know the total load current 106.

[0110] In Figures 1 to 3, the processor 1 16 is configured to activate, deactivate and control the load current modifier 114, and both the processor 1 16 and the load current modifier 1 14 are located within the housing 1 18 and integrated with the electrical meter 102. In Figure 4, the processor 216 and the load current modifier 214 are both separately formed to the meter 102.

[0111] With reference to Figures 1 to 3, the load current modifier 1 14 is connected via terminals 114a thereof to two meter power lines 120 to modify the current flow thereof. In these examples, the terminals are printed circuit board (PCB) connections, which can be tracks, connectors, or any suitable way of connecting the load current modifier 114 to the meter power lines 120. “Terminal 1 14a” is not intended to necessarily mean a physical, accessible terminal, although in some examples the terminals 1 14a may be implemented as such.

[0112] The meter 102 comprises a plurality of voltage sense lines, connected to the two meter power lines 120 to measure the line-line voltage thereof. This includes two line side voltage sense lines 122a configured to measure a voltage adjacent to the line inputs 108 and two load side voltage sense lines 122b configured to measure a voltage adjacent to the load outputs 110. In the examples of Figures 1 to 3, the current sense transformers 104a are located between the voltage sense lines 122a, 122b. The term “adjacent” in this context means that the line side voltage sense line 122a is located closer to the line input 108 than the load output 1 10, with the load side voltage sense line 122b located closer to the load output 110 than the line input 108.

[0113] In the examples of Figures 1 and 2, the load current modifier 1 14 is connected adjacent to the load output 110 downstream of the current sensing transformers 114a. The Figure 1 example is a first, current sink mode, in which the load current modifier 1 14 is configured such that additional power is drawn through the current sensor module 104 and dissipated by the load current modifier 114. Of course, for a.c. systems current flow will be bi-directional through the meter power lines 120, but what is being explained here is that power will be drawn from the electricity supply, through the power lines 120, to the current modifier 1 14 for consumption there, which is a current sink mode as power is being consumed. This type of modified current adds to the power consumed by the end-user load.

[0114] Figure 2 shows the load current modifier 114 configured in a second, current source mode, in which the load current modifier 1 14 provides power to the load side, which effectively reduces the current flow (and the power) drawn from the electrical power supply via the line side. This type of modified current reduces the effective current (and power) measured by the current sense module 104 and the meter 102.

[0115] In the examples of Figure 1 and 2, the terminals 1 14a of the load current modifier 1 14 are connected to the two load side voltage sense lines 122b.

[0116] In the example of Figure 3, the load current modifier 114 is configured in a third, current loop mode, to draw power in a loop formed by the line side to the load current modifier 1 14 to the load side to the current sensor module 104 back to the line side. In this example, power is consumed in the load current modifier 114 but the power is alternately drawn down through the current sensing module 104, or upwards through the current sensing module 104.

[0117] In the example of Figure 3, a first set of terminals 1 14a’ are connected to the line side voltage sense lines 122a and a second set of terminals 1 14a” are connected to the load side voltage sense lines 122b. The load current modifier 1 14 is configured to selectively activate bidirectional current flow through the first terminals 1 14a’ to the second terminals 114a”, which effectively results in bi-directional power flow in a loop as depicted in Figure 3, which in the case of a predominantly reactive load within the current modifier 1 14, results in a “phantom load” within the meter 102 which does not consume any, or negligible real power. In some examples, the load current modifier 114 may be operable to selectively draw power through the first terminals 1 14a’ and / or the second terminals 114a”.

[0118] Whereas in Figure 3 the load current modifier 114 is connected to the line side and the load side, in some examples the load current modifier 1 14 may be connected at or adjacent to the line side only or the load side only.

[0119] In the example of Figure 4, the terminals 214a of the load current modifier 214 are connectable to a plurality of external electrical power supply lines 130 external to, and downstream of the meter 102. In this example, typically the load current modifier 214 is connectable remote from the meter 102 to an electrical terminal housing the plurality of external electrical supply lines 130, such as a mains socket, or the like. The electrical supply lines 130 will follow on from the meter power lines 120, but it will be understood that in the example of Figure 4, the load current modifier 214 can be configured for connection to any suitable node or point of the electrical power supply lines 130 on the load side. For example, the terminals 214a of the load current modifier 214 could be pins, plugs, clips, probes, or the like, for connecting with various parts of the load side, such as sockets, bare wires, terminals, etc. Figure 4 depicts only one possible connection where the terminals 214a are connected to the L1 and L2 lines, but this is an example and the terminals 214a are connectable to the L1 & N lines, or L2 & N lines.

[0120] In some examples, including those shown here, the load current modifier 114, 214 is operable to modify the amplitude / rms value of the load current 106. However, in other examples additional or alternative parameters could be modified, such as the phase of the load current 106 relative to the voltage, or any suitable parameter of the load current 106. It will be understood to those of skill in the art that changing the phase of the load current 106 may change the polarity of power flow for at least a portion of a cycle (from consuming power to providing power back to the electrical supply, for at least some of the cycle). For brevity, the present specification often describes load current modifications without detailing the accompanying power flow, with the skilled person understanding that in some examples the load current modifier 1 14 may change the load current 106 in such a way that the magnitude and / or the polarity of the power flow may change. The skilled person will also readily appreciate that manipulating the load current 106 can be done in a great many ways to determine various tamper or fault states, and the use of amplitude modification is merely an example to demonstrate how a load current modifier 1 14 can lead to the determination of tamper / fault states. It is also not necessary to discuss the power flow, as the invention works by comparing differences in load current 106 to determine if the meter 102 is functioning as expected. In examples with an ideal sinusoidal supply voltage, changing the amplitude changes the rms value in the same proportion. It will be understood that in other embodiments, it may be that the amplitude and / or rms value may be modified.

[0121] In Figure 1 , the amplitude / rms value of the load current 106 can be increased by the load current modifier 114, in Figure 2 the amplitude / rms of the load current 106 can be decreased, and in Figure 3, the load current modifier 114 is operable to increase and decrease the amplitude / rms value of the load current 106. For the example of Figure 4, the load current modifier 214 is arranged as per Figure 1 (first, current sink mode), but downstream and remote of the meter 102, but in other examples of the system 200, the arrangement of Figure 2 (second, current source mode) could be employed by the load current modifier 214, (again, downstream and remote from the meter 102). It will be understood that in yet further examples of the Figure 4 system 200, it may be desirable to connect the load current modifier 214 within the meter, which may be a temporary connection, by opening the meter 102 and making the connection to the terminals 214a, or by connecting to the terminals of the meter 102.

[0122] In the examples of Figure 1 and Figure 3 the load current modifier 114 is configured to provide the modified current flow component entirely within the meter 102. In these examples, no current flow from the load current modifier 114 flows out of the load outputs 1 10, although it will be understood that current is drawn from the line side via the line inputs 108.

[0123] In each of Figures 1 , 2, and 3 the load current modifier 1 14 is configured in a single current mode (first, sink mode for Figure 1 ; second, source mode for Figure 2, third, current loop mode for Figure 3). In other examples, the load current modifier 1 14 may be operable to switch between current modes. Using Figure 3 as an example, this could be modified such that if the current flow through the first terminals 1 14a’ is switched off, current flows through the second terminals 1 14a”, which is a first, sink mode. Likewise, if the current flow is through the first terminals 114a’ but not the second terminals 114a”, this is also a first, sink mode. Whereas if current flow is through both the first and second sets of terminals 1 14a’, 114a”, this is the third, current loop mode.

[0124] Figure 5 shows the load current modifier 1 14 of Figure 1 , configured in the first, current sink mode. The examples of Figure 5 to 8 each represent a possible implementation of the load current modifier 114, which are purely examples, and it will be understood that many other suitable implementations are possible besides those shown in Figures 5 to 8. The load current modifier 1 14 comprises a switching device 1 14c for selectively activating and controlling the modification to the load current 106. In the examples described here, the switching device 1 14c is a TRI AC, with a load resistor 1 14b and a control resistor 114d. A control 1 14f (which may be a connection to the processor 1 16) is shown schematically for controlling the TRI AC 1 14c. Advantageously, only two main power components are required, the switching device 114c and the load resistor 114b, and because the switching device 1 14c does not need to be active for a long period of time, the power rating of the TRI AC 1 14c and load resistor 1 14b are not overly restrictive. For example, for a current flow of approximately 110mA at 240V through the TRIAC 114c and the load resistor 1 14b, a 0.25 W, 2.2 KOhm, + / -5% resistor may be sufficient, although this is an example and other components may be used. This therefore offers a low cost addition to the meter 102. Similar advantages can be obtained from other configurations of the load current modifier 1 14.

[0125] The switching device 114c is configured to switch and control the flow of current across the terminals 1 14a of the current modifier 114. Current flow for Figure 1 & Figure 5 is through one terminal 114a, through the TRI AC 1 14c, through the load resistor 114b, and through the other terminal 114a. Of course the current flow alternates for ac, with this direction of current flow being purely explanatory.

[0126] Figure 6 depicts the load current modifier 114 of Figure 2, configured in the current source mode, with most of the same components as Figure 5 with the exception of a current source 114e in place of the load resistor 1 14b. Any suitable current source can be employed for this purpose.

[0127] Figure 7 shows the load current modifier 114 of Figure 3, configured in the third, current loop mode. In this example, a transformer 1 14g is used as the load element to facilitate current flow in both directions through the current sensor module 104.

[0128] In the current sink examples, such as Figure 5, the expected additional current flow can be calculated by Ohm’s law across the load resistor 1 14b, and for the current source examples, such as Figure 6, a current sensor can be included within the load current modifier 1 14 to measure the current. It will be understood by those of skill in the art that there are numerous ways in which the modified current component, provided by the load current modifier 1 14, can be measured.

[0129] In other examples, the tamper detection system 100 is operable to both detect tamper / faults and to modify the power factor of the load downstream of the line inputs 108 of the meter 102 by the load current modifier 114 being operable to modify the power factor of the load. Typically, this is done by using a load capacitor 1 14h with the switching element 1 14c, with or in place of the resistive load 1 14b, to activate power flow through a reactive load (the load capacitor 1 14h) to modify the power factor. An example is shown in Figure 8. To detect tampering, the TRIAC 1 14c can be switched on and off in the usual way as per the examples of Figure 1 to 3, and when not detecting tampering, the TRIAC 1 14c will be activated to “switch in” the reactive load to balance or alter the power factor. This is useful for industrial inductive loads, but it will be appreciated that if the load is capacitive, an inductive reactive load can be included in the load current modifier 1 14 instead of a capacitive load. Whilst examples using a single load resistor 1 14b / capacitor 1 14h have been described, it will be understood that any combination of active / passive components can be used with the load current modifier 1 14 as required, such as a capacitor bank, one or more transistors, a plurality of transformers, etc. To carry out a tamper / fault detection analysis, the processor 116 is operable to determine when the load current 106 is at a first, unmodified state using the received load current data. Typically, the processor 116 will be configured to determine if the first, unmodified load current is within a predetermined threshold, such as varying by about 5% or less, or about 2% or less, or about 1 % or less. In practice, this may occur during periods of steady, low power usage, such as late at night. In some examples, an algorithm may know when certain appliances are drawing current in a known manner and therefore recognize that the load current is in a first, unmodified state, which in such examples may be considered a background load current state. The modification to the load current 106 by the load current modifier 114 is a second, modified current state. The processor 1 16 is configured to run a load current modification automatically when the load current 106 is at the first, unmodified state and it will be understood that the number of load current modifications carried out, or when the load current modification is carried out, can be predetermined or selected, such as once per day, or monthly, or in response to user input. If the test is set to be run once per day, the processor 116 may be configured to detect first, unmodified state load current within certain times, or to sample periodically, or in other ways.

[0130] In the examples illustrated and described here, the processor 1 16 is configured to obtain a plurality of samples of the first, unmodified state load current 106 to determine when to apply the modified current (from the load current modifier 1 14) to carry out the tamper detection analysis. The processor 116 is configured to wait a predetermined interval between obtaining the samples of the first, unmodified state load current, and is configured to obtain a plurality of samples of the modified current. For example, the processor 1 16 may obtain 5 or 10 samples of the first, unmodified state current over a particular time period, and modify and sample the current 5 or 10 times over another time period. In some examples, the sampling of the first, unmodified state load current happens first, then the modification and sampling of the modified current, whereas in other examples, it may be desirable to interleave the first, unmodified state periods and the current modification periods. It will be understood that the design of the first, unmodified state sampling and current modification and sampling can be tailored as required. The processor 116 averages the obtained first, unmodified state samples and the modified current samples, but any suitable data processing can be employed. In some examples, the further device would carry out the data processing.

[0131] The processor 1 16 is configured to measure the difference between the amplitude / rms values of the modified load current 106 and the first, unmodified state load current 106. The processor 116 has a stored, expected difference value between the modified load current 106 and the first, unmodified state load current 106. In other examples, the processor 116 may obtain the expected value, e.g. by requesting it over a network. The processor 1 16 is configured to compare the measured difference and the expected difference of the modified and first, unmodified state load currents 106. The processor 1 16 then determines the tamper or fault state based on the comparison of the measured difference and the expected difference of the modified and first, unmodified state load currents 106. In other examples, the processor 1 16 may transmit the required data to the further device for the further device to carry out the determination of the tamper / fault states, which may include transmitting load current data, expected difference value, the measured difference, and any other required data, such as voltages. It will be understood that in some examples, the further device may have stored expected values, rather than receiving them from the processor 116.

[0132] In some examples, the processor 116 is configured to adjust the expected current difference over time, to compensate for component degradation, such as the drift in capacitor value over time as the capacitor ages. Other compensation methods may be employed, and this example is merely illustrative of why the expected current difference value may change over time.

[0133] It will be understood that for different first, unmodified state load current values, the processor 1 16 works out different expected values for the difference in modified current to the first, unmodified state value. This might be represented in a look-up table or in any suitable fashion. In some examples, the further device may calculate the expected values.

[0134] In some examples, the processor 1 16 may include a flag that a tamper or fault state is possibly present. That is, rather than inferring that it is present, the flag may be that further investigation is required, or the like.

[0135] Turning now to the tamper or fault states, in the embodiments of Figures 1 to 8 these include all of the following:

[0136] (i) A no tamper / fault state, which is when the measured current difference is equal to the expected current difference or within a tolerance (e.g. within 5%, or 2%, or 1 %);

[0137] (ii) A first tamper / fault state, which is when the measured current difference is zero or within a tolerance (e.g. within 5%, or 2%, or 1 %). The processor infers at least one of: that the sensor module (or at least one sensor element thereof) has an open circuit or short circuit tamper / fault, manufacturing fault, or loss / corruption of meter calibration data. (iii) A second tamper / fault state, which is when the measured current difference is non-zero and less than the expected current difference (e.g. within 5%, or 2%, or 1 %). The processor infers that at least one of: the possibility of an added parallel / series component (e.g. a resistor) to the current sensor module 104 (or to at least one sensor element 104a thereof); one or more line inputs 108 of the meter 102 connected directly to one or more of the load outputs 110 of the meter 102 to bypass the meter 102; or loss / corruption of meter calibration data.

[0138] (iv) A third tamper / fault state, which is when the measured current difference is nonzero and more than the expected current difference (e.g. within 5%, or 2%, or 1%). The processor infers at least one of: loss / corruption of meter calibration data.

[0139] It will be understood that in other examples, the number and nature of the tamper / fault states may be different. The numbering of the tamper / fault states is purely for explanatory purposes and does not attribute a preferred hierarchy or required number of tamper / fault states. In other examples, the further device and / or the processor may determine the tamper / fault states.

[0140] The processor 116 is configured to determine the tamper or fault state by selecting from the possible tamper / fault states above, and flags the selected tamper / fault state with an inference of the possible or likely cause of the tamper / fault state, which can include more than one possible cause. The tamper detection system 100 is configured to transmit the determined tamper / fault state (determined by the processer) to any suitable device, such as the further device, which may be a computing device, networked device, server or the like. For example, the tamper detection system 100 may transmit the tamper / fault state (and the inference of the cause) over the same communication system used to transmit meter data from the meter 102 to the utility provider. In some examples, such as that of Figure 4, the tamper detection system 200 may use a different communication channel, such as a cell / mobile telephone network, or other wireless / wired communication means. In the examples of Figure 1 to 3, the processor 1 16 autonomously carries out tamper detection analysis, autonomously determines the tamper / fault state, and autonomously transmits the tamper / fault state (and inference of the cause). In the example of Figure 4, the processor 216 carries out the test in response to user input, but it will be understood that the system 200 of Figure 4 could in some examples be configured for autonomous testing. In the example of Figure 4, the load current modifier 214 is configured by the processor 216 to modify the load current 106 for one cycle of the supply (for a 60Hz supply, one cycle is 1 / 60 seconds), but in other examples the load current modifier 214 could be configured to modify the load current 106 for a different period of time. For example, the load current modifier 214 could modify the load current 106 for any timed duration or any number of line cycles, which could be a fractional line cycle, such as 1 / 10 of a line cycle or the like. It is thought to be advantageous to modify the load current 106 for a short period of time, such as 100 cycles or less, as this will have a negligible effect on the metered power consumption.

[0141] In the example of Figure 4, the tamper detection system 200 is formed in a discrete tamper detection device 201 separate to the meter 102. The tamper detection device 201 includes a casing 203 for the components thereof. In other examples, the system 200 may be implemented in more than one casing 203 (e.g. one for the load current modifier 214 and one for the current sensor module 204 and processor 216 and other main components).

[0142] The tamper detection system 200 of Figure 4 is a portable, hand-held system 200, implemented in a small, portable casing 203 that can easily be carried by hand.

[0143] In the example of Figure 4, the current sensor module 204, the load current modifier 214, the processor 216, and the communication unit 207 are located within the casing 203. The system 200 of Figure 4 is designed to be used by a meter inspection professional to carry out tamper / fault detection on a plurality of meters 102, whereas the system 100 of Figures 1 to 3 is designed to be embedded within the meter 102 for the long term, to mitigate the need for in-person inspection.

[0144] The electrical power meter 102 of Figures 1 to 4 includes a load current switch 124 (an example of a service disconnect switch) operable to interrupt the supply of current between the line inputs 108 and the load outputs 1 10.

[0145] The tamper detection system 100 of Figures 1 to 3 includes line side and load side voltage sensors 126 located within the meter 102, which obtain voltage measurements from the voltage sense lines 122a, 122b. In the example of Figure 4, the tamper detection device 201 obtains any required voltage data direct from the meter 102 (via the voltage sensors 126), although it will be understood that in some examples the tamper detection system 200 may include its own voltage sensors if necessary.

[0146] The tamper detection system 100 of Figures 1 to 3 comprises a power supply 128 drawn from the plurality of line side voltage sense lines 122a. The tamper detection device 201 of Figure 4 comprises its own power supply 228, including a battery, but other means of powering the device 201 can be used.

[0147] In the examples of Figure 1 to 3, the electrical meter 102 is configured to amend the total metered energy usage to account for power consumption of the load current modifier 1 14. This includes subtracting at least some of the energy consumed by the load current modifier 114 from the total metered energy usage. In other examples the tamper detection system 200, may carry out this function rather than the electrical meter 102, which might include transmitting data to a utility provider.

[0148] Although the disclosure has been described in terms of embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure, which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in any embodiments, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.

[0149] REFERENCE NUMERALS

[0150] 100 T amper detection system 200 T amper detection system

[0151] 102 Electrical power meter 201 T amper detection device

[0152] 104 Current sensor module 35 203 Casing

[0153] 104a Current sensing transformer 204 Current sensor module

[0154] 106 Load current 207 Communication unit

[0155] 108 Line input 207a Wireless connection

[0156] 110 Load output 214 Load current modifier

[0157] L1 Phase line 40 214a Terminals

[0158] L2 Phase line 216 Processor

[0159] 112 Neutral line 228 Power supply

[0160] 114 Load current modifier

[0161] 114a Terminals

[0162] 114a’ First terminals 45

[0163] 114a” Second terminals

[0164] 114b Load resistor

[0165] 114c Switching device

[0166] 114d Control resistor

[0167] 114e Current source 50

[0168] 114f Control

[0169] 114g T ransformer

[0170] 114h Capacitor

[0171] 116 Processor

[0172] 118 Housing 55

[0173] 120 Meter power line

[0174] 122a Line side voltage sense lines

[0175] 122b Load side voltage sense lines

[0176] 124 Load current switch

[0177] 126 Voltage sensors 60

[0178] 128 Power supply

[0179] 130 External power supply lines

Claims

1. CLAIMS:1 . A tamper detection system for an electrical power meter, the system comprising: a current sensor module operable to measure at least a portion of a load current between a line input and a load output of the electrical power meter; and a load current modifier operable to modify the load current.

2. The tamper detection system of claim 1 , wherein the tamper detection system comprises a processor configured to receive load current data from the current sensor module.

3. The tamper detection system of claim 2, wherein the processor is configured, based at least in part on received load current and modified load current data, to determine a tamper or fault state of the meter.

4. The tamper detection system of claim 2 or claim 3, wherein the processor is configured to transmit the received load current data to a further device, such as a computing device, a networked device, a server, or the like, and wherein the further device is configured to determine the tamper or fault state of the meter.

5. The tamper detection system of any preceding claim, wherein the load current modifier is located within, or integrated with the electrical meter.

6. The tamper detection system of any of claims 1 to 4, wherein the load current modifier is separately formed to the electrical meter.

7. The tamper detection system of any preceding claim, wherein the current sensor module is located within, or integrated with the electrical meter.

8. The tamper detection system of any of claims 1 to 6, wherein the current sensor module is separately formed from the electrical meter.

9. The tamper detection system of any preceding claim, wherein the current sensor module is configured to measure at least a portion of the load current directly.

10. The tamper detection system of any of claims 1 to 6, 8 or 9, wherein the current sensor module is operable to measure at least a portion of the load current by obtaining data from the electrical meter.1 1 . The tamper detection system of any of claims 2 to 10, wherein the processor is operable to control the load current modifier.

12. The tamper detection system of any preceding claim, wherein the meter comprises at least one meter power line between a line input and a load output thereof, and wherein the load current modifier is connectable or connected to at least one, or a plurality of meter power lines to modify the current flow thereof.

13. The tamper detection system of any preceding claim, wherein the load current modifier is connectable to one or more, or a plurality of electrical supply lines external to the meter.

14. The tamper detection system of claim 12 or claim 13, when dependent on claim 12, wherein the meter comprises at least one of: a plurality of load side voltage sense lines configured to measure a voltage at or adjacent to the load output(s) of the meter; and a plurality of line side voltage sense lines configured to measure a voltage at or adjacent to the line input(s) of the meter.

15. The tamper detection system of claim 14, wherein the load current modifier is connectable or connected to the plurality of load side voltage sense lines and / or to the plurality of line side voltage sense lines.

16. The tamper detection system of any preceding claim, wherein the load current modifier is operable to modify at least one of: the amplitude, rms value, and phase.

17. The tamper detection system of claim 16, wherein the load current modifier is operable to increase or decrease at least one of: the amplitude, rms value and phase.

18. The tamper detection system of any preceding claim, wherein the load current modifier is configurable or configured in one or more current modes, or operable between two or more current modes.

19. The tamper detection system of claim 18, wherein the current modes comprise at least one of: a first, current sink mode, a second, current source mode, and a third, current loop mode.

20. The tamper detection system of any preceding claim, wherein the load current modifier is configured to provide the modified current flow at least partially within the meter, or entirely within the meter.21 . The tamper detection system of any preceding claim, wherein the tamper detection system is operable to modify the power factor of the load downstream of the line input(s) of the meter, or downstream of the load output(s) of the meter.

22. The tamper detection system of claim 21 , wherein the load current modifier is configured to activate power flow through a reactive load, such as a capacitive or inductive load, to modify the power factor of the load.

23. The tamper detection system of any of claims 2 to 22, wherein the processor is operable to determine when the load current is in a first, unmodified state, by using the received load current data.

24. The tamper detection system of claim 23, wherein the processor is configured to modify the load current at least once within a set time period when the load current is in the first, unmodified state.

25. The tamper detection system of any of claims 2 to 24, wherein the processor is operable to run a load current modification automatically and / or in response to user input.

26. The tamper detection system of any of claims 23 to 25, wherein the processor is configured to measure the difference between the modified current and the first, unmodified state load current, and wherein the processor is configured to obtain or store an expected difference value between the modified current and the first,unmodified state current, and wherein the processor is configured to compare the measured difference and the expected difference of the modified and first, unmodified state load currents, and wherein the processor is configured to determine the tamper or fault state based on the comparison of the measured difference and the expected difference of the modified and first, unmodified state load currents.

27. The tamper detection system of any of claims 23 to 26, wherein the processor is configured to transmit first, unmodified state load current data to the further device, and wherein the further device is configured to measure the difference between the modified current and the first, unmodified state load current, and wherein the processor is configured to transmit the expected difference value between the modified current and the first, unmodified state current to the further device, and wherein the further device is configured to determine the tamper or fault state based on the comparison of the measured difference and the expected difference of the modified and first, unmodified state load currents.

28. The tamper detection system of claim 26 or claim 27, wherein the tamper or fault state includes at least one of:(I) a no tamper / fault state, which may be when the measured current difference is equal to the expected current difference or within a tolerance (such as within 5%, or 2%, or 1%);(ii) a first tamper / fault state, which may be when the measured current difference is zero or within a tolerance (such as within 5%, or 2%, or 1 %), and wherein the processor or further device infers at least one of: that the sensor module (or at least one sensor element thereof) has an open circuit or short circuit tamper / fault, manufacturing fault, or loss / corruption of meter calibration data;(iii) a second tamper / fault state, which may be when the measured current difference is non-zero and less than the expected current difference (e.g. within 5%, or 2%, or 1 %), and wherein the processor or further device infers that at least one of: the possibility of an added parallel / series component to the sensor module or to at least one sensor element thereof; one or more line inputs of the meter connected directly to one or more of the load outputs of the meter to bypass the meter; or loss / corruption of meter calibration data; and(iv) a third tamper / fault state, which may be when the measured current difference is nonzero and more than the expected current difference (e.g. within5%, or 2%, or 1 %), and wherein the processor or further device infers at least one of: loss or corruption of meter calibration data.

29. The tamper detection system of any of claims 2 to 28, wherein the processor is configured to flag a tamper / fault state with an inference of the possible or likely cause of the tamper / fault state.

30. The tamper detection system of any preceding claim, wherein the tamper detection system is configured to transmit the determined tamper / fault state to the further device.31 . The tamper detection system of claim 30, wherein the processor is configured to autonomously carry out tamper detection and to autonomously determine the one or more tamper / fault states and to be configured to autonomously transmit, send, or otherwise report the tamper / fault state to the further device.

32. The tamper detection system of any of claims 1 to 4, 6, or 8 to 31 , wherein the tamper detection system is separately formed from the electrical meter in a discrete tamper detection device.

33. The tamper detection system of claim 32, wherein the tamper detection device is portable.

34. A tamper detection method for an electrical power meter, the method comprising: measuring at least a portion of a load current between a line input and a load output of the electrical power meter; modifying the load current; and measuring the modified load current.

35. An electrical power meter comprising a tamper detection system, the tamper detection system comprising: a current sensor module operable to measure at least a portion of a load current between a line input and a load output of the electrical power meter; and a load current modifier operable to modify the load current.

36. A tamper detection system for an electrical power meter, the system comprising:a tamper detection device comprising: a current sensor module operable to measure at least a portion of a load current between a line input and a load output of the electrical power meter; and a load current modifier operable to modify the load current.

37. A tamper detection kit for an electrical power meter, the kit comprising: a current sensor module operable to measure at least a portion of a load current between a line input and a load output of the electrical power meter; and a load current modifier operable to modify the load current.

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