Electricity meter that detects grid-side voltage

Abstract

An electric power meter (400) is disclosed. The electric power meter (400) includes a power supply (460) for powering a measurement circuit (430) and a surge protector (455) for protecting inputs (VA_LINE, VC_LINE) to the power supply. The measurement circuit is configured to measure a voltage across the surge protector. A corresponding method of operating the electric power meter is also disclosed, the method including configuring the measurement circuit to measure a voltage across the surge protector. The surge protector is configured to protect an input to the power supply configured to power the measurement circuit.

Description

[Technical Field]

[0001] Related Applications This application claims priority to UK Patent Application Serial No. 2214709.4, filed October 6, 2022, and UK Patent Application Serial No. 2305776.3, filed April 19, 2023, both of which are incorporated herein by reference in their entireties.

[0002] Technical Field of the Disclosure The present disclosure is in the field of electric power meters for measuring electric power consumption, such as in residential and commercial premises installations. The present disclosure particularly relates to electric meters with grid-side voltage sensing capability. [Background technology]

[0003] An electricity meter (also known in the art as an electricity meter, electrical power meter, electric meter, or electrical meter) is a device that measures the amount of electricity consumed by one or more powered devices over a defined time interval, such as in a residential or commercial premises installation.

[0004] Electricity meters are typically installed on premise equipment for the purposes of billing and monitoring consumption. In some instances, electricity meters may be read manually and periodically to determine a predetermined level of electricity consumption. In other instances, advanced electricity meters, known in the art as "smart meters," may be configured to communicate, e.g., wirelessly, with a utility to provide electricity consumption information and / or receive billing information and / or control signals.

[0005] Electricity, e.g., power, may be transmitted to a premises installation over a range of available service types, such as single-phase, three-wire, commonly used in residential premises installations in the U.S., three-phase, four-wire, Y, commonly used in commercial premises installations in the U.S., and three-phase, three-wire, Delta, commonly used in industrial installations in the U.S. As is known in the art and described in more detail below, different service types have associated electricity meter styles, e.g., 2S, 3S, 5S, etc. Summary of the Invention [Problem to be solved by the invention]

[0006] Electricity meters must be designed to be safe and robust. For example, electricity meters must be able to withstand substantial electrical surges. In one example, a lightning strike can cause a substantial voltage spike and / or current surge at the input to the electricity meter. In another example, a short circuit in one or more loads connected to the electricity meter can cause a substantial voltage spike and / or current surge.

[0007] Furthermore, in use, the electricity meter must be capable of monitoring both "load-side" and "grid-side" voltages. In particular, electricity meters that implement a service disconnect switch between the load and grid sides of the electricity meter to selectively disconnect power on the grid side from a load on the load side may require accurate measurements of both the load-side and grid-side voltages before reconnecting power.

[0008] The load side of the power meter may refer to the connection of the power meter to a load that consumes power. The grid side of the power meter may refer to the connection of the power meter to a power line from a utility, e.g., from a power grid.

[0009] To ensure sufficient reliability of the electricity meter, expensive components and significant printed circuit board (PCB) spacing may be required to withstand large voltage surges on both the load-side and grid-side voltage connections, where both the load-side and grid-side voltages may be measured by the electricity meter. Such features may contribute substantially to the manufacturing cost of the electricity meter.

[0010] It is therefore desirable to provide a relatively low-cost manufactured electricity meter that can withstand large voltage surges on both the load-side and grid-side voltages while allowing for effective measurement of power consumption and safe control of service disconnect functions.

[0011] It is therefore an object of at least one embodiment of at least one aspect of the present disclosure to avoid or at least mitigate at least one of the above-mentioned disadvantages of the prior art. [Means for solving the problem]

[0012] The present disclosure is in the field of electric power meters for measuring electric power consumption, such as in residential and commercial premises installations. The present disclosure particularly relates to electric meters with grid-side voltage sensing capability.

[0013] According to a first aspect of the present disclosure, there is provided an electricity meter comprising a power supply for supplying power to a measurement circuit, and a surge protector for protecting an input to the power supply, the measurement circuit being configured to measure a voltage across the surge protector.

[0014] Advantageously, by performing the measurement of voltage across the surge protector, the expensive resistor strings typically dedicated to grid-side voltage measurements in prior art power meters are eliminated, thereby reducing overall manufacturing costs.

[0015] Alternatively, a lower cost resistor may be placed across the surge protector in the power supply, allowing an alternative means of measuring the grid side voltage.

[0016] In such electricity meters, the voltage measurement intended for measuring power consumption may alternatively come from a load-side resistive string that could be used only to detect customer generation.

[0017] Moreover, advantageously, such a configuration allows the power meter to maintain a reference to the grid-side voltage even when the service disconnect switch is configured to disconnect the load side from the grid side. This can be particularly important for detecting cogeneration scenarios, such as when a user implements power generation capabilities, because reconnecting the load side to the grid side while cogeneration is in progress can result in catastrophic damage to the power meter and / or be dangerous.

[0018] By eliminating expensive resistor strings on the grid side, the overall component count in the high voltage area of ​​the PCB in the power meter can be reduced, and board slots that may be required between voltage strings for electrical isolation purposes can also be eliminated.

[0019] Such an overall reduction in PCB space can help reduce the overall cost of a PCB by more efficiently penalizing the PCB during manufacturing.

[0020] The surge protection device may comprise at least one of a Metal-Oxide Varistor (MOV), a Gas Discharge Tube (GDT), a Transient Voltage Suppressor (TVS) diode, and / or a Polymeric Positive Temperature Coefficient Device (PPTC).

[0021] The input may comprise a first voltage input and a second voltage input, and the surge protector may be connected to a first node connected to the first voltage input and a second node connected to the second voltage input.

[0022] In some embodiments, multiple surge protectors may be implemented, e.g., more than two voltage inputs may be implemented in other embodiments within the scope of this disclosure, and in some embodiments, each voltage input may be protected by at least one surge protector.

[0023] In use, the first voltage input may comprise a first phase and the second voltage input may comprise a second phase different from the first phase.

[0024] For example, the second phase may be out of phase, e.g., 180 degrees out of phase with respect to the first phase. That is, in some embodiments, the electricity meter may be configured for use with a single-phase, three-wire service type.

[0025] As previously mentioned, in other embodiments, more than two voltage inputs may be implemented. For example, in some embodiments, the electricity meter may be configured for use with a three-phase, four-wire, wye service type or with a three-phase, three-wire, delta service type.

[0026] The power meter may include a first voltage divider connected to the first node and a second voltage divider connected to the second node, and the measurement circuit may be configured to measure the voltage at each of the first and second voltage dividers to determine the voltage across the surge protector.

[0027] The voltage divider embodiment may provide an accurate and reliable means for measuring voltage, where the resistor values ​​of the voltage divider may be selected to provide sufficient accuracy without excessive loading of the power line.

[0028] The first and second voltage dividers may be configured to withstand a clamping voltage of the surge protector.

[0029] That is, advantageously, the surge protector may limit the magnitude of a surge across the input to the power supply. In this way, the first and second voltage dividers only need to withstand the magnitude of a surge that can be tolerated by the surge protector, rather than the 10,000 volts or more that might be required to protect against a surge caused by, for example, a lightning strike.

[0030] Various embodiments of the voltage dividers may be implemented. For example, at least one of the first and second voltage dividers may comprise a resistive voltage divider, a capacitive voltage divider, or an inductive voltage divider.

[0031] In some embodiments, the power meter may include a first linear transformer connected to a first node and a second linear transformer connected to a second node, and the measurement circuit may be configured to measure a voltage at each of the first and second linear transformers to determine a voltage across the surge protector.

[0032] That is, the linear transformer may provide an alternative to one or both voltage dividers, thereby providing the measurement circuit with an alternative means for determining the voltage across the surge protector.

[0033] The power meter may further include a surge protection element between the first voltage input and the first node.

[0034] The surge protection element may be a resistor.

[0035] In some embodiments, the measurement circuitry comprises: taking a sample of the measured voltage across the surge protection device; Detecting when a time period of distortion in the measured voltage across the surge protector begins; obtaining a current value at the input terminals of the power supply during a time period; Using the current value to determine the voltage drop across the surge protector during the time period; Correcting samples of the measured voltage across the surge protector taken during the time period based on the voltage drop across the surge protector during the time period. The device may include a processor configured to:

[0036] The power meter may further comprise a current sensing device configured to output a current value. Advantageously, thereby, an accurate current value at the input terminals of the power supply during a time period may be obtained. The current sensing device may be connected between the first node and the input terminals.

[0037] Alternatively, the current value may be pre-stored in a memory accessible by the processor, and the processor is configured to obtain the current value by retrieving the current value from the memory. Advantageously, this avoids the need to have a current sensing device, thus saving PCB space. The processor may be configured to retrieve the current value from the memory based on the operating mode of the power meter.

[0038] In some embodiments, the measurement circuitry comprises: taking a sample of the measured voltage across the surge protection device; Detecting when a time period of distortion in the measured voltage across the surge protector begins; determining a peak voltage during the distortion time period using (i) the measured voltage across the surge protector when the distortion time period begins, and (ii) the time between a zero crossing of the measured voltage across the surge protector and when the distortion time period of the measured voltage across the surge protector begins; Correcting samples of the measured voltage across the surge protector taken during the time period based on the peak voltage. The device may include a processor configured to:

[0039] The power supply may comprise at least one rectifier and / or regulator circuit configured to supply power to the measurement circuit.

[0040] For example, the power supply may include a rectifier, such as a bridge rectifier, configured to provide a DC output from an AC input at the input to the power supply.

[0041] The power supply may provide AC or rectified DC to one or more regulators. For example, the one or more regulators may be configured to provide a range of voltages suitable for operation of different components of the smart meter. As a non-limiting example, the power supply may be configured to provide 24 volts DC to an actuator for a service disconnect switch, 5 volts DC to a transceiver driver, relatively low voltage 3.3 volts DC to a microprocessor circuit, etc.

[0042] The power meter may include an actuatable switch for selectively connecting the grid-side input of the power meter to the load-side output of the power meter.

[0043] Such an actuatable switch may be known in the art as a "service disconnect switch." In embodiments, as described in more detail below, the service disconnect switch may be operated under remote control, such as by a utility, to connect or disconnect the load side from the grid side in a premises installation.

[0044] The measurement circuit may be configured to measure a load-side voltage at a load-side output of the actuatable switch.

[0045] Measuring the load side voltage allows for the detection of cogeneration activity, such as by using a generator or solar panels, before reconnecting the load side to the grid side via a service disconnect switch, thereby increasing the safety level of the electricity meter's operation.

[0046] The measurement circuit may be configured to measure the load-side current at the load-side output of the actuatable switch.

[0047] The voltage across the surge protector may correspond to the voltage at the grid-side input of the actuatable switch.

[0048] A comparison of the grid-side and load-side voltages may be performed before reconnecting the load side to the grid side with a service disconnect switch, improving the safety level of the electricity meter's operation. Such a comparison may be performed by processing circuitry within the electricity meter or by one or more remote devices, such as networked devices operated by the utility.

[0049] The electricity meter may include a control circuit.

[0050] The control circuitry may include one or more processors.

[0051] The measurement circuitry may include an analog front end, which may include an analog-to-digital converter, an anti-aliasing filter, etc. The analog front end may be communicatively coupled to the control circuitry. The analog front end may be configured to perform analog measurements of load-side and / or grid-side voltages and / or currents and convert such measurements to digital signals for communication to the control circuitry.

[0052] The power meter may include communications circuitry. For example, the power meter may include a transceiver configured to communicate with a remote device. In an embodiment, the communications circuitry may be configured as a node in a mesh network comprising a plurality of power meters. In an embodiment, the communications circuitry may be configured to transmit data to a utility, and such data may relate to power consumption and / or voltage levels on the grid side and / or the load side of the power meter. In an embodiment, the communications circuitry may be configured to receive signals or data for controlling operation of a service disconnect switch.

[0053] The control circuitry may be configured to selectively actuate the actuatable switch based at least in part on a voltage at the grid-side input measured by the measurement circuitry, a load-side voltage measured by the measurement circuitry, and / or data received by the communication circuitry.

[0054] Advantageously, the control circuit, or a remote device in communication with the control circuit, may be able to identify any cogeneration activity before configuring an operable switch, e.g., a service disconnect switch, to reconnect the load side of the power meter to the grid side.

[0055] According to a second aspect of the present disclosure, there is provided a method of operating an electricity meter, the method including configuring a measurement circuit to measure a voltage across a surge protector, the surge protector configured to protect an input to a power source configured to power the measurement circuit.

[0056] The method may include selectively operating an enable switch of the electricity meter. The enable switch may be configured to selectively connect a grid-side input of the electricity meter to a load-side output of the electricity meter.

[0057] The selective activation of the operable switch may be based at least in part on a voltage at the grid-side input measured by the measurement circuitry, a load-side voltage measured by the measurement circuitry, and / or data received by the communication circuitry of the electricity meter.

[0058] The method may include identifying a cogeneration scenario based on a load-side voltage and a voltage at the grid-side input while the actuatable switch is configured to decouple the grid-side input of the electricity meter from the load-side output of the electricity meter.

[0059] The foregoing summary is intended to be merely illustrative and non-limiting. The present disclosure includes one or more corresponding aspects, embodiments, or features, whether specifically described (including in the claims) in combination or separately, separately or in various combinations. It should be understood that the features defined above for any aspect of the present disclosure, or the features defined below for any particular embodiment of the present disclosure, may be utilized alone or in combination with any other defined feature in any other aspect or embodiment, or to form further aspects or embodiments of the present disclosure. [Brief explanation of the drawings]

[0060] [Figure 1] 1 shows a block diagram of a prior art power meter connected in series with a load, the power meter having a 2S format. [Figure 2] 1 shows a further example of a prior art electricity meter. [Figure 3] 1 shows an example of a circuit from a prior art electricity meter. [Figure 4] 1 illustrates an electricity meter having a measurement circuit configured to measure a voltage across a surge protector according to an embodiment of the present disclosure. [Figure 5] 1 illustrates an example of a circuit from a power meter, according to an embodiment of the present disclosure. [Figure 6] 10 illustrates an alternative example of a circuit from a power meter according to a further embodiment of the present disclosure. [Figure 7] 6 shows a distorted grid-side voltage waveform measured in the circuit of FIG. 5. [Figure 8] 1 shows a grid-side voltage waveform generated in the grid. [Figure 9] 5 shows a schematic block diagram of an analog front-end circuit that can be used in the measurement circuit of FIG. 4. [Figure 10a] 6 is a flow chart illustrating a method that may be performed by a processor of an analog front-end circuit when the processor has knowledge of the current at the input terminals of the power supply of the circuit of FIG. 5. [Figure 10b] 6 shows an example current waveform at the input terminal of the power supply of the circuit of FIG. 5. [Figure 11] 6 is a flow chart illustrating a method that may be performed by a processor of an analog front-end circuit when the processor does not have knowledge of the current at the input terminals of the power supply of the circuit of FIG. 5. [Figure 12] 10 is a flowchart illustrating a method that may be performed by a processor of an analog front-end circuit to detect when distortion from clipping begins. [Figure 13] 6 shows a distorted grid-side voltage waveform measured in the circuit of FIG. 5 and a second-order derivative waveform calculated from the distorted grid-side voltage waveform. DETAILED DESCRIPTION OF THE INVENTION

[0061] These and other aspects of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings.

[0062] 1 shows a block diagram of a prior art power meter 100. For purposes of illustration, the prior art power meter 100 is configured as a Type 2S service type power meter, which is a meter configured for use with single-phase three-wire service.

[0063] A prior art power meter 100 is installed in series with a load 105, shown as a residential load for purposes of illustrating a residential load.

[0064] In use, the high voltage power line 110 may receive power from the grid, i.e., from a utility company. The transformer 115 may step down the voltage at the power line 110 to a voltage suitable for use by the load 105, such as 240 volts or 110 volts.

[0065] In the exemplary power meter 100, the first input terminal 120a is connected to a supply voltage from the transformer 115 having a first phase, and the second input terminal 120c is connected to a supply voltage from the transformer 115 having a second phase. The second phase is different from the first phase. For example, the second phase may be out of phase, e.g., 180 degrees out of phase with respect to the first phase. The first input terminal 120a may be known in the art as the “phase A” input. The second input terminal 120c may be known in the art as the “phase C” input.

[0066] The first output terminal 140a and the second output terminal 140c are connected to the load 105 and are therefore capable of supplying power to the load 105.

[0067] The exemplary power meter 100 includes a first actuatable switch S1 and a second actuatable switch S2. The first actuatable switch S1 can selectively disconnect / connect the first load-side output terminal 140a to the first grid-side input terminal 120a. The second actuatable switch S2 can selectively disconnect / connect the second load-side output terminal 140c to the second grid-side input terminal 120c.

[0068] In use, the first actuatable switch S1 and the second actuatable switch S2, which may be collectively known as "service disconnect switches," may be configured to selectively connect / disconnect the load side from the grid side of the power meter 100. That is, the first actuatable switch S1 may selectively connect the first input terminal 120a to the first output terminal 140a, and the second actuatable switch S2 may selectively connect the second input terminal 120c to the second output terminal 140c.

[0069] The exemplary power meter 100 includes measurement circuitry 130. The measurement circuitry 130 includes an analog front end (AFE), denoted as "AFE" in FIG. 1 . The measurement circuitry 130, and in particular the AFE, may include an analog-to-digital converter, an anti-aliasing filter, etc. The AFE may be communicatively coupled to control circuitry and / or processing circuitry (not shown). The AFE may be configured to perform analog measurements of grid-side voltages and / or load-side voltages and / or currents and convert such measurements to digital signals for communication to the control circuitry, as described further below.

[0070] The “phase A” input voltage level at the first input terminal 120a, for example, on the grid side of the first operable switch S1, may be measured by the measurement circuit 130, such as by detecting the voltage across a resistor string (not shown) at a first node 135a connected to the first input terminal 120a.

[0071] The "phase C" input voltage level at the second input terminal 120c, for example, on the grid side of the second operable switch S2, may be measured by the measurement circuit 130, such as by detecting the voltage across a resistor string (not shown) at a second node 135c connected to the second input terminal 120c.

[0072] The “Phase A” output voltage level at the first output terminal 140a, e.g., at the load side of the first operable switch S1, may be measured by the measurement circuit 130, such as by detecting the voltage across a resistor string (not shown) at a third node 145a connected to the first output terminal 140a.

[0073] The "phase C" output voltage level at the second output terminal 140c, for example, at the load side of the second operable switch S2, may be measured by the measurement circuit 130, such as by detecting the voltage across a resistor string (not shown) at a fourth node 145c connected to the second output terminal 140c.

[0074] The power meter 100 also includes a first current transformer 150a for providing a signal to the measurement circuit 130 corresponding to the "phase A" current on the load side of the first operable switch S1.

[0075] The power meter 100 also includes a second current transformer 150c for providing a signal to the measurement circuit 130 corresponding to the phase C current on the load side of the second operable switch S2.

[0076] FIG. 2 shows a more detailed example of a prior art power meter 200 that generally corresponds to the Type 2S power meter 100 of FIG. 1, but shows certain components of the power meter 200 in greater detail.

[0077] A prior art power meter 200 is installed in series between a grid 215 and a load 205 .

[0078] In the exemplary power meter 200, the first input terminal 220a is connected to a supply voltage from the grid 215 having a first phase, and the second input terminal 220c is connected to a supply voltage from the grid 215 having a second phase, where the second phase is different from the first phase.

[0079] The first input terminal 220a and the second input terminal 220c may be provided at the service entrance of the electricity meter 200.

[0080] The first input terminal 220a is sometimes known in the art as the "Phase A" input. The second input terminal 220c is sometimes known in the art as the "phase C" input.

[0081] The first output terminal 240a and the second output terminal 240c are connected to the load 205 and are therefore capable of supplying power to the load 205.

[0082] The exemplary power meter 200 includes a service disconnect switch 295 that can selectively disconnect / connect the grid 215 from the load 205 .

[0083] The power meter 200 includes an actuator 265 , which may include, for example, a solenoid for actuating a service disconnect 295 .

[0084] The exemplary power meter 200 includes measurement circuitry 230. Measurement circuitry 230 includes analog front end 270. Measurement circuitry 230, and particularly analog front end 270, may include analog-to-digital converters, anti-aliasing filters, etc. In this example, analog front end 270 is communicatively coupled to digital circuitry 275. Analog front end 270 may be configured to perform analog measurements of grid-side and load-side voltages and currents and convert such measurements to digital signals for processing by digital circuitry 275. In some examples, data corresponding to the processed measurements may be communicated to remote devices, such as other power meters in a mesh network, by digital circuitry 275, which may include communication circuitry such as a transceiver.

[0085] The grid voltage detection circuit 280G, designated V_SENSEGRID, is configured to determine the voltage at each of the first and second input terminals 220a, 220c, thereby providing a grid-side voltage measurement. The grid voltage detection circuit 280G may be implemented using a relatively expensive resistor string (not shown), which will be described in more detail below with reference to FIG. 3. Such an expensive resistor string may be able to withstand substantial voltage spikes and current surges, such as those that may be incurred due to a lightning strike. Such a resistor string may contribute substantially to the overall cost of manufacturing the power meter 200. The grid voltage detection circuit 280G is connected to the analog front end 270 to enable measurement of the grid-side voltage.

[0086] 1, power meter 200 also includes a load voltage detection circuit 280L, designated V_SENSELOAD, for detecting the voltage across load 205 on the load side of service disconnect switch 295. Load voltage detection circuit 280L is connected to analog front end 270 and allows for measurement of the load side voltage. Load voltage detection circuit 280L may also be implemented with a relatively expensive resistor string.

[0087] The "phase A" current flowing from the first input terminal 220a to the load 205 may be measured using a first current sensing circuit 290a, denoted I_SENSEPHASE_A, to determine the power consumption by the load 205. The first current sensing circuit 290a may comprise a current transformer. The first current sensing circuit 290a is connected to the measurement circuit 230, for example, to one or more ADC channels of the analog front end 270.

[0088] The "phase C" current flowing from the second input terminal 220c to the load 205 may be measured using a second current sensing circuit 290c, denoted I_SENSEPHASE_C, to determine the power consumption by the load 205. The second current sensing circuit 290c may include a current transformer. The second current sensing circuit 290c is connected to the measurement circuit 230, for example, to one or more ADC channels of the analog front end 270.

[0089] The power meter 200 includes a power supply 260. The power supply 260 receives power from the grid 215 via a first input terminal 220a and a second input terminal 220c. The power supply 260 provides power to the components of the power meter 200. In this example, the power supply 260 provides power to an actuator 265. The power supply 260 also provides power to the measurement circuit 230. In this example, the power supply 260 may include at least one rectifier and / or regulator circuit configured to provide power to the measurement circuit 230 and the actuator 265. For example, the power supply 260 may include a rectifier, such as a bridge rectifier, configured to provide a DC output from an AC input at the input to the power supply 260. The power supply 260 may include one or more regulators configured to provide a range of voltages suitable for operation of different components of the smart meter. As an example, power supply 260 may be configured to provide 24 volts DC to actuator 265, 5 volts DC to analog front end 270, and 3.3 V DC to microprocessor circuitry within digital circuitry 275.

[0090] FIG. 3 shows an example of a circuit 300 from a prior art electricity meter having a 2S format, such as electricity meters 100 and 200.

[0091] Input terminal 320c may correspond to second input terminal 120c, 220c in Figures 1 and 2. Also shown is a further input terminal 320n which, in use, may be connected to the neutral conductor.

[0092] Output 325c may be an input to a measurement circuit, for example, output 325c may be an input to an anti-aliasing filter of an ADC to measure the voltage at input terminal 320c.

[0093] A resistor string 345c comprising resistors R1-R6 is connected to input terminal 320c. In use, the voltage across resistor string R1-R6 may be used to measure the voltage at input terminal 320c, for example, on the grid side of service disconnect switch 295 of power meter 200. Such a resistor string 345c can be expensive to implement, can consume substantial PCB space, and can incur cost and product form factor limitations.

[0094] It will be appreciated that the circuit 300 of FIG. 3 is provided for illustrative purposes only, and that different meter formats may implement different resistor string configurations. For example, for a "single" phase format, such as a 2S meter format, resistors R7-R12 may be provided. For a "multi-phase" meter format, such as a 12S meter format, resistors R1-R6 may be provided. Additionally, for a 12S meter format, resistors R7-R11 may be provided with a value of 0 ohms, connecting a further input terminal 320n connected to neutral to AGND. Thus, different meter formats may implement different configurations of relatively expensive resistor strings.

[0095] FIG. 4 illustrates an electricity meter 400 according to an embodiment of the present disclosure, where a measurement circuit 430 is configured to measure the voltage across a surge protector 455 of a power source 460 .

[0096] The power meter 400 is installed in series between the grid 415 and the load 405. In the exemplary power meter 400, the first input terminal 420a is connected to a supply voltage from the grid 415 having a first phase, and the second input terminal 420c is connected to a supply voltage from the grid 415 having a second phase, where the second phase is different from the first phase. The first input terminal 420a and the second input terminal 420c may be provided at a service entrance of the power meter 400.

[0097] The first input terminal 420a may be known in the art as the "phase A" input. The second input terminal 420c may be known in the art as the "phase C" input.

[0098] The first output terminal 440a and the second output terminal 440c are connected to the load 405 and are therefore capable of providing power to the load 405.

[0099] The exemplary power meter 400 includes a service disconnect switch 495 that can selectively disconnect / connect the grid 415 from the load 405 .

[0100] The power meter 400 includes an actuator 465 , which may include, for example, a solenoid for actuating the service disconnect 495 .

[0101] The exemplary power meter 400 includes a measurement circuit 430. The measurement circuit 430 includes an analog front end 470. The measurement circuit 430, and in particular the analog front end 470, may include an analog-to-digital converter, an anti-aliasing filter, etc. In this example, the analog front end 470 is communicatively coupled to a digital circuit 475. The analog front end 470 may be configured to perform analog measurements of grid-side and load-side voltages and currents and convert such measurements to digital signals for processing by the digital circuit 475. In some examples, data corresponding to the processed measurements may be communicated to remote devices, such as other power meters in a mesh network, by the digital circuit 475, which may include communication circuitry such as a transceiver.

[0102] 2, power meter 400 includes a load voltage detection circuit 480L, designated V_SENSELOAD, for detecting the voltage across load 405 on the load side of service disconnect switch 495. Load voltage detection circuit 480L is connected to analog front end 470 and allows for measurement of the load side voltage. Load voltage detection circuit 480L may also implement a relatively expensive resistor string.

[0103] The "phase A" current flowing from the first input terminal 420a to the load 405 may be measured using a first current sense circuit 490a, denoted I_SENSEPHASE_A, for purposes of determining power consumption by the load 205. The first current sense circuit 490a may comprise a current transformer. The first current sense circuit 490a is connected to the measurement circuit 430, for example, to one or more ADC channels of the analog front end 470.

[0104] The "phase C" current flowing from the second input terminal 420c to the load 405 may be measured using a second current sensing circuit 490c, denoted I_SENSEPHASE_C, to determine the power consumption by the load 405. The second current sensing circuit 490c may include a current transformer. The second current sensing circuit 490c is connected to the measurement circuit 430, for example, to one or more ADC channels of the analog front end 470.

[0105] The power meter 400 includes a power supply 460. The power supply 460 receives power from the grid 415 via a first input terminal 420a and a second input terminal 420c. The power supply 460 provides power to the components of the power meter 400. In an embodiment, the power supply 460 provides power to an actuator 465. The power supply 460 also provides power to the measurement circuit 430. In an embodiment, the power supply 460 may include at least one rectifier and / or regulator circuit configured to provide power to the measurement circuit 430 and the actuator 465. For example, the power supply 460 may include a rectifier, such as a bridge rectifier, configured to provide a DC output from an AC input at the input to the power supply 460. The power supply 460 may include one or more regulators configured to provide a range of voltages suitable for operation of different components of the smart meter. As one example, power supply 460 may be configured to provide 24 volts DC to actuator 465, 5 volts DC to analog front end 470, and 3.3 volts DC to microprocessor circuitry within digital circuitry 475.

[0106] At the input to the power supply 460, a surge protector 455 is provided. The surge protector 455 is configured to protect the input to the power supply from voltage and / or current surges that may be caused by lightning strikes, short circuits, and the like.

[0107] In one preferred embodiment, the surge protector 455 may be implemented as a metal oxide varistor (MOV). In other embodiments, the surge protector may comprise at least one of a gas discharge tube (GDT), a transient voltage suppression (TVS) diode, and / or a polymer positive temperature coefficient device (PPTC).

[0108] Although a single surge protector 455 is referenced, it will be understood that multiple surge protectors may be implemented in embodiments within the scope of the present disclosure.

[0109] A surge protector 455 may limit the voltage appearing at the input of the power supply.

[0110] A grid voltage detection circuit 480G, designated V_SENSEGRID, is configured to determine the voltage across the surge protector 455, thereby providing a grid-side voltage measurement.

[0111] Unlike the grid voltage detection circuit 280G of FIG. 2, in the embodiment of FIG. 4, the grid voltage detection circuit 480G does not require expensive resistor strings, as will be described in more detail below with reference to FIG.

[0112] Grid voltage detection circuit 480G is connected to analog front end 470 and enables measurement of grid-side voltage. By performing the grid-side voltage measurement across surge protector 455, expensive resistor strings typically dedicated to grid-side voltage measurement in prior art power meters 100, 200, such as resistor strings 345a and 345c shown in FIG. 3, may be eliminated, reducing the overall manufacturing cost of power meter 400.

[0113] That is, because surge protector 455 limits the voltage at the input of the power supply, grid voltage detection circuit 480G only needs to withstand the maximum voltage allowed by surge protector 455.

[0114] In such a power meter 400, voltage measurements for purposes of measuring power consumption may be derived from the load side resistor string, using a load voltage detection circuit 480L that was intended to be used only for detecting customer generation.

[0115] In use, the measurement circuit 430 may be configured to measure the voltage across the surge protector 455 to provide information indicative of the grid-side voltage.

[0116] In use, operation of the service disconnect switch 495 , which selectively connects the grid-side input of the power meter to the load-side output of the power meter, may be based on the grid-side voltage measured across the surge protector 455 .

[0117] That is, the selective activation of the service disconnect switch 495 may be based at least in part on the voltage at the grid-side input measured by the measurement circuitry 430, the load-side voltage measured by the measurement circuitry 430, and / or data received by the communication circuitry of the power meter 400.

[0118] In some embodiments, a cogeneration scenario may be identified based on a comparison of the load-side voltage and the voltage at the grid-side input while the actuatable switch 495 is configured to decouple the grid-side input of the power meter 400 from the load-side output of the power meter.

[0119] FIG. 5 illustrates an example of a circuit 500 from an electric power meter, such as electric power meter 400 of FIG. 4, according to an embodiment of the present disclosure.

[0120] 5, "VA_LINE" represents the input connected to a first input terminal, e.g., first input terminal 420a, and "VC_LINE" represents the input connected to a second input terminal, e.g., second input terminal 420c.

[0121] A first output, designated "U1," may be an input to a measurement circuit, such as measurement circuit 430. A second output, designated "U3," may be an input to a measurement circuit, such as measurement circuit 430. In use, U1 and U3 may be inputs to an ADC anti-aliasing filter in measurement circuit 430.

[0122] In the exemplary circuit, power supply 560 is implemented as a bridge rectifier. That is, power supply 560 may be configured to provide direct current to other features of the power meter. In one embodiment, power supply 560 may correspond to power supply 460 of power meter 400 of FIG. 4.

[0123] A surge protector 555 is provided across the input of the power supply. In the exemplary circuit 500, the surge protector 555 is implemented as a varistor, e.g., an MOV. The surge protector 555 may correspond to the surge protector 455 of the power meter 400 of FIG. 4.

[0124] In the exemplary circuit 500, a grid voltage detection circuit 580G is provided. The grid voltage detection circuit 580G may correspond to the grid voltage detection circuit 480G of the power meter 400 of Figure 4. A surge protector 555 is connected to a first node 505a and a second node 505c of the grid voltage detection circuit 580G.

[0125] The first voltage divider 510a is connected to the first node 505a, and the second voltage divider 510c is connected to the second node 505c. The first output "U1" is the divided voltage from the first voltage divider 510a. The second output "U3" is the divided voltage from the second voltage divider 510c. Thus, the measurement circuit 430, having U1 and U3 as inputs, may be configured to measure the voltages at the first and second voltage dividers 510a, 510c, respectively, to determine the voltage across the surge protector 555.

[0126] In the exemplary circuit 500, a surge protection element in the form of resistor R36 502 is included as additional lightning surge resistance. As shown in FIG. 5, resistor R36 502 is placed between the first voltage input (VA_LINE) and a first node (505a). Resistor R36 502 is placed before the surge protector 555 to limit the current flowing into the surge protector 555 in the event of a surge event. Resistor R36 502 may be, for example, between 47 and 100 ohms. Resistor R36 502 may have a rating of, for example, between 2 and 5 watts.

[0127] In the exemplary circuit 500, resistor R3 is included as a balancing resistor to account for the flow of power supply current that shifts the AGND point of the 2S meter.

[0128] 5 are resistive dividers, it will be understood that in other embodiments, other types of voltage dividers may be implemented. For example, in embodiments, one or both of the first and second voltage dividers 510a, 510c may be implemented as capacitive or inductive voltage dividers. Furthermore, in still further embodiments, one or both of the first and second voltage dividers 510a, 510c may be replaced with a linear transformer to determine the voltage across the surge protector 555.

[0129] FIG. 6 illustrates one example of an alternative circuit 600 from an electric power meter, such as electric power meter 400 of FIG. 4, according to an embodiment of the present disclosure.

[0130] The features of circuit 600 generally correspond to those of circuit 500 and therefore, for the sake of brevity, will not be described in further detail.

[0131] 5, in circuit 600 of FIG. 6, resistor R36 502 is replaced with a surge protection element in the form of an inductor designated "L36" 602. Advantageously, inductor L36 602 instead of resistor R36 502 may be used to limit surge currents and may reduce distortion in the measured voltage due to any current flow in power supply 660.

[0132] In this regard, the inventors have identified methods for compensating for distortions in the measured voltage in the exemplary circuit 500 in which surge protection elements are used. These methods are particularly advantageous when the surge protection element has the form of surge resistor R36 502. When power is drawn to the power supply 560, grid-side voltage peaks cause a voltage drop across surge resistor R36 502, which begins to conduct through the diode of the power supply 560 and then charges a large capacitor (not shown), which causes distortions in the detected grid-side voltage that are not an accurate reflection of the voltage at the grid. A large capacitor, not shown, may be placed between TP6 and TP7 in FIGS. 5 and 6.

[0133] Figure 7 shows a distorted grid-side voltage waveform 700 that may be measured by the grid voltage detection circuit 580G of Figure 5. As shown, the distorted grid-side voltage waveform 700 suffers from clipping during the time period Tp of the distortion due to the power being drawn by the power supply 560.

[0134] 8 shows a grid-side voltage waveform 800 generated in the grid. Comparing with FIG. 8, the distorted grid-side voltage waveform 700 shows that the peak voltage Vpk of the grid-side voltage is not accurately detected by the grid voltage detection circuit 580G due to the distortion introduced by the resistor R36 502.

[0135] Figure 9 shows a schematic block diagram of an analog front-end circuit 970 that may be used in the measurement circuit of Figure 4 to enable measurement of the grid-side voltage. The analog front-end circuit 970 may correspond to the analog front-end circuit 470 of the power meter 400 of Figure 4.

[0136] 9, the first output "U1" and the second output "U3" are processed before being provided in digital form to a processor 906. The first output "U1" and the second output "U3" may optionally be provided as inputs to anti-aliasing filters 902, 912 before being provided to respective analog-to-digital converters (ADCs) 904, 914.

[0137] According to an embodiment of the present disclosure, the processor 906 is arranged to process the detected outputs of the digital first output “U1” and second output “U3” carrying the grid-side voltage to compensate for distortion introduced by the surge resistor R36 502.

[0138] The functionality of the processor 906 described herein may be implemented as code (e.g., instructions) stored on a memory (e.g., memory 910) comprising one or more storage media and configured to execute on a processor comprising one or more processing units. The storage medium may be integrated with the processor 906 and / or separate. The code, when retrieved from the memory and executed on the processor, is configured to perform operations according to the embodiments described herein. When executed by the processor, the instructions may cause the processor to perform any of the methods described herein. These instructions may be provided on a non-transitory computer-readable medium. These instructions may also be provided on a carrier such as a disk, CD- or DVD-ROM, a programmed memory such as a read-only memory (firmware), or a data carrier such as an optical carrier or an electrical signal carrier. Alternatively, it is not excluded that some or all of the functionality of the processor 906 may be implemented as dedicated hardware circuits (e.g., one or more ASICs, simple circuits, gates, logic, and / or configurable hardware circuits such as FPGAs).

[0139] In some embodiments of the present disclosure, the processor 906 is configured to compensate for the distortion introduced by the surge resistor R36 502 using knowledge of the current at the input terminals of the power supply 560. In other embodiments, the processor 906 is configured to compensate for the distortion introduced by the surge resistor R36 502 without knowledge of the current at the input terminals of the power supply 560. The input terminals of the power supply 560 mentioned above may correspond to the input terminals 590 or the input terminals 595 shown in FIG.

[0140] We will first describe an embodiment in which processor 906 is configured to compensate for distortion introduced by surge resistor R36 502 using knowledge of the current at the input terminals of power supply 560, with reference to the flowchart shown in FIG. 10a.

[0141] FIG. 10 a is a flow chart illustrating a method 1000 that may be performed by the processor 906 of the analog front-end circuit 970 .

[0142] 10a, in step S1002, the processor 906 obtains a sample of the voltage (measured grid-side voltage waveform) across the surge protector 555 based on receiving the digital first output "U1" and second output "U3." The measured grid-side voltage waveform may be measured by the grid voltage detection circuit 580G of FIG.

[0143] In step S1004, processor 906 detects the time t at which a time period Tp of distortion in the grid-side voltage waveform begins (the distortion shown in FIG. 7). Various techniques may be used by processor 906 to perform step S1004. One exemplary technique is described in more detail below with reference to FIG. 12.

[0144] In step S1006, the processor 906 obtains the current (IPS) at the input terminals of the power source 560 during the time period Tp of the grid-side voltage distortion.

[0145] In some embodiments, circuit 500 includes a current sensing device operable to measure the current (IPS) at the input terminals of power supply 560. In these embodiments, processor 906 obtains the current (IPS) based on receiving a measurement signal output by the current sensing device. The current sensing device may be a resistor, a Hall effect current sensor, or a magnetoresistive sensor.

[0146] The input terminal of the power supply 560 may correspond to the input terminal 590 shown in FIG. 5. To ensure that all supply current at the input terminal 590 of the power supply 560 is measured, a current sensing device is preferably located between the first node 505a and the input terminal 590 of the power supply 560 (e.g., the current sensing device may be located at node TP2 or between nodes TP2 and TP4 of the circuit 500). In some embodiments, the current sensing device may be placed in series with the differential choke L24. The differential choke L24 may be included in the circuit 500 to prevent conducted radiation originating from the power supply 560 from flowing back onto the grid. In other embodiments, the current sensing device may be placed in series with or instead of one or both of the resistors R684 and R685. In still further embodiments, The current sensing device may correspond to the combination of differential mode inductor L24 in parallel with resistors R684 and R685.

[0147] The input terminal of the power supply 560 may correspond to the input terminal 595 shown in Figure 5. In particular, a current sensing device may be located between the second node 505c and the input terminal 595 of the power supply 560 (e.g., the current sensing device may be located at node TP5).

[0148] FIG. 10b shows the current (IPS) 1050 at the input terminals of the power supply 560, which may be measured by the current sensing device described above.

[0149] In other embodiments, the processor 906 obtains the current (IPS) based on pre-stored characterization data stored in a memory (e.g., memory 910). In particular, the memory may store one or more pre-defined current profiles including data about how the current (IPS) is expected to change over time with respect to the grid-side voltage. Each of the one or more pre-defined current profiles may be associated with an operating mode of the power meter (e.g., a wireless transmit operating mode, a service-disconnected operating mode, a transmitter in receive mode, or a firmware update mode), and the processor 906 may be configured to retrieve the pre-defined current profile corresponding to the operating mode of the power meter. It will be appreciated that in these embodiments, the current (IPS) is not measured. Instead, the processor 906 is configured to determine the current (IPS) based on the detected grid-side voltage and the pre-defined current profile. FIG. 10b illustrates the current (IPS) 1050 at the input terminals of the power source 560, which may be obtained from a pre-defined current profile, as described above. In these embodiments, the processor 906 may perform step S1006 before, during, or after the distortion time period Tp.

[0150] In step S1008, the processor 906 determines the voltage drop across the surge resistor R36 502 during the distortion time period Tp (e.g., using the formula V=IR) using (i) the current (IPS) at the input terminals of the power supply 560 during the distortion time period Tp and (ii) the resistance value of the surge resistor R36 502. It will be appreciated that the voltage drop across the surge resistor R36 502 changes during the distortion time period Tp.

[0151] In step S1010, processor 906 is configured to modify samples of the measured voltage across surge protector 555 taken during the time period of distortion Tp based on the voltage drop occurring across the surge protector during the time period of distortion Tp. That is, for each sample of the measured voltage across surge protector 555 taken during the time period of distortion Tp, processor 906 is configured to compensate for the distortion by adding to the measured voltage the voltage drop that occurred when the sample was taken to accurately reflect the voltage occurring on the grid.

[0152] Step S1008 may be performed dynamically during the time period Tp of distortion. Alternatively, step S1008 may be performed after the end of the time period Tp of distortion. Step S1010 may be performed dynamically during the time period Tp of distortion. Alternatively, step S1010 may be performed after the end of the time period Tp of distortion.

[0153] We will now describe, with reference to the flowchart shown in FIG. 11, an embodiment in which the processor 906 is configured to compensate for the distortion introduced by the surge resistor R36 502 without knowledge of the current at the input terminals of the power supply 560.

[0154] FIG. 11 is a flowchart illustrating a method 1100 that may be performed by the processor 906 of the analog front-end circuit 970.

[0155] 11, in step S1102, the processor 906 obtains a sample of the voltage (measured grid-side voltage waveform) across the surge protector 555 based on receiving the digital first output "U1" and second output "U3." The measured grid-side voltage waveform may be measured by the grid voltage detection circuit 580G of FIG.

[0156] In step S1104, processor 906 detects the time t at which a time period Tp of distortion in the grid-side voltage waveform begins (the distortion shown in FIG. 7). Various techniques may be used by processor 906 to perform step S1004. One exemplary technique is described in more detail below with reference to FIG. 12.

[0157] In step S1106, the processor 906 is configured to determine the voltage Vt across the surge protector 555 at time t when the time period Tp of distortion of the grid-side voltage waveform begins.

[0158] In step S1108, the processor 906 is configured to use the voltage Vt and the time t to determine a peak voltage Vpk (which can be a positive or negative peak voltage) during the time period Tp of the distortion, where Vpk is the clipped peak voltage of the measured grid-side voltage sample during the time period Tp of the distortion due to the distortion introduced by the resistor R36 502. In particular, the processor 906 may apply the values ​​of the voltage Vt and the time t to the following equation to determine the peak voltage Vpk:

[0159] Vpk=Vt / arcsine(2πf*t)

[0160] where f is the fundamental frequency of the measured grid-side voltage. As described below, the fundamental frequency f may be detected during step S1104 as part of the process of detecting the time t at which the time period Tp of distortion begins. Alternatively, the processor 906 may be configured to detect the fundamental frequency f as a step separate from step S1104.

[0161] In step S1110, the processor 906 is configured to modify samples of the measured voltage across the surge protector 555 taken during the time period Tp of distortion based on the peak voltage Vpk to compensate for the distortion introduced by the surge resistor R36 502.

[0162] For example, the processor 906 may use curve fitting techniques to determine the voltages that need to be added to the measured voltage samples during the distortion time period Tp to accurately reflect the voltages occurring on the grid using (i) samples of the measured voltage across the surge protector 555 taken before the distortion time period Tp, (ii) the peak voltage Vpk, and (iii) samples of the measured voltage across the surge protector 555 taken after the distortion time period Tp.

[0163] For each sample of the measured voltage across the surge protector 555 taken during the distortion time period Tp, the processor 906 may be configured to compensate for the distortion by adding a voltage (determined using curve fitting techniques for that sample) to accurately reflect the voltage occurring at the grid.

[0164] FIG. 12 is a flow chart illustrating a method that may be performed by the processor 906 of the analog front-end circuitry 970 in steps S1004 and / or S1104 to detect the time t at which the time period Tp of distortion in the grid-side voltage waveform begins.

[0165] In step S1202, the processor 906 is configured to process samples of the voltage across the surge protector 555 (the measured grid-side voltage waveform) to detect the fundamental frequency f.

[0166] In step S1204, the processor 906 is configured to process samples of the voltage across the surge protector 555 (the measured grid-side voltage waveform) to detect zero crossings of the fundamental frequency f (e.g., points at which the measured grid-side voltage changes sign, represented by crossings of the X-axis (zero value) in the measured grid-side voltage waveform).

[0167] In step S1206, the processor 906 is configured to calculate a second derivative of the measured grid-side voltage waveform to generate a second derivative curve, and detect a clipping point in the measured grid-side voltage waveform when the first peak of the second derivative curve (after the zero crossing) occurs.

[0168] In step S1208, the processor 906 is configured to measure the time t from the zero crossing of the fundamental frequency to the first peak of the second derivative curve to determine the time t at which the time period Tp of the distortion of the grid-side voltage waveform begins.

[0169] It will be appreciated that other methods may be used to detect when the time period Tp of grid-side voltage waveform distortion begins.

[0170] FIG. 13 illustrates a distorted grid-side voltage waveform 700 that may be measured by the grid voltage detection circuit 580G of FIG. 5. As illustrated, the distorted grid-side voltage waveform 700 is subject to clipping during the time period Tp of distortion due to the power being drawn by the power supply 560. FIG. 13 also illustrates a second derivative curve 1300 that may be calculated by the processor 906. FIG. 13 illustrates the first peak 1302 of the second derivative curve, the time t from the zero crossing of the fundamental frequency to the first peak 1302 of the second derivative curve, and the time period Tp of distortion. While the present disclosure has been described with respect to specific embodiments, such as those described above, it should be understood that these embodiments are exemplary only and that the claims are not limited to these embodiments. Those skilled in the art will be able to make modifications and variations in light of this disclosure that are intended to be within the scope of the appended claims. Each feature disclosed or illustrated herein may be incorporated into any embodiment, either alone or in any suitable combination with any other feature disclosed or illustrated herein. [Explanation of symbols]

[0171] 100 Electricity Meter 105 Load 110 Power line 115 Transformer 120a First input terminal 120c Second input terminal 130 Measurement circuit 135a First Node 135c Second Node 140a First output terminal 140c Second output terminal 145a Third Node 145c Fourth Node 150a First current transformer 150c Second Current Transformer 200 Electricity Meter 205 Load 215 grid 220a First input terminal 220c Second input terminal 230 Measurement circuit 240a First output terminal 240c Second output terminal 260 Power supply 265 Actuator 270 Analog Front End 275 Digital Circuits 280G Grid voltage detection circuit 280L Load voltage detection circuit 290a First current detection circuit 290c Second Current Detector Circuit 295 Service Disconnect Switch 300 circuits 320a First input terminal 320c Second Input Terminal 325a First Output 325c Second Output 345a First resistor string 345c Second resistor string 400 Electricity Meter 405 Load 415 Grid 420a First input terminal 420c Second Input Terminal 430 Measurement circuit 440a First output terminal 440c Second output terminal 455 Surge Protector 460 power supply 465 Actuator 470 Analog Front End 475 Digital Circuits 480G Grid Voltage Detection Circuit 480L Load voltage detection circuit 490a First current detection circuit 490c Secondary Current Detector Circuit 495 Service Disconnect Switch 500 circuits 502 Surge protection element 505a First node 505c Second node 510a First voltage divider 510c Second Voltage Divider 555 Surge Protector 560 power supply 590 input terminal 595 input terminal 660 power supply 602 Surge protection element 700 Distorted grid-side voltage waveform 800 Grid side voltage waveform 902 Anti-aliasing Filter 904 Analog / Digital Converter 906 processor 910 memory 912 Anti-aliasing Filter 914 Analog / Digital Converter 970 Analog Front-End Circuit 1050 current 1300 Second Derivative Curve 1302 First Peak

Claims

1. a power supply (460, 560, 660) for supplying power to the measurement circuit (430); a surge protection device (455, 555) for protecting the input to the power supply; the measurement circuitry is configured to measure a voltage across the surge protector; Electricity meter (400).

2. The surge protection device (455, 555) is Metal oxide varistors (MOVs), Gas discharge tubes (GDTs), Transient voltage suppression (TVS) diodes, and / or Polymer Positive Temperature Coefficient Device (PPTC) comprising at least one of: The electricity meter (400) of claim 1.

3. the inputs comprising a first voltage input (VA_LINE) and a second voltage input (VC_LINE); The surge protector (455, 555) is connected to a first node (505a) connected to the first voltage input and to a second node (505c) connected to the second voltage input. The electricity meter (400) of claim 1 or 2.

4. In use, the first voltage input (VA_LINE) has a first phase and the second voltage input (VC_LINE) has a second phase different from the first phase. The electricity meter (400) of claim 3.

5. The power meter (400) comprises a first voltage divider (510a) connected to a first node (505a) and a second voltage divider (510c) connected to a second node (505c); The measurement circuit (430) is configured to measure the voltage at each of the first and second voltage dividers to determine the voltage across the surge protector (455, 555). The electricity meter (400) of claim 3 or 4.

6. - said first and second voltage dividers (510a, 510c) are configured to withstand the clamping voltage of said surge protection device (455, 555); at least one of the first and second voltage dividers comprises a resistive, capacitive or inductive voltage divider; The electricity meter (400) of claim 5.

7. The electricity meter (400) comprises a first linear transformer connected to a first node (505a) and a second linear transformer connected to a second node (505c); The measurement circuit (430) is configured to measure a voltage at each of the first and second linear transformers to determine a voltage across the surge protector (455, 555). The electricity meter (400) of claim 3 or 4.

8. a surge protection element (502, 602) between the first voltage input (VA_LINE) and the first node (505a); An electricity meter (400) according to any one of claims 3 to 7.

9. The surge protection element is a resistor. The electricity meter (400) of claim 8.

10. The measuring circuit (430) obtaining a sample of the measured voltage across the surge protector; Detecting when a time period of distortion in the measured voltage across the surge protector begins; obtaining a current value at an input terminal of the power supply during the time period; using the current value to determine a voltage drop across the surge protector during the time period; modifying samples of measured voltage across the surge protector taken during the time period based on the voltage drop across the surge protector during the time period; a processor configured to: The electricity meter (400) of claim 8 or 9.

11. further comprising a current detection device configured to output the current value; The electricity meter (400) of claim 10.

12. the current sensing device is connected between the first node (505a) and the input terminal; The electricity meter (400) of claim 11.

13. the current value is pre-stored in a memory accessible by the processor, and the processor is configured to retrieve the current value from the memory. The electricity meter (400) of claim 10.

14. the processor is configured to retrieve the current value from the memory based on an operational mode of the power meter; The electricity meter (400) of claim 13.

15. The measuring circuit (430) obtaining a sample of the measured voltage across the surge protector; Detecting when a time period of distortion in the measured voltage across the surge protector begins; (i) determining a peak voltage during the distortion time period using the measured voltage across the surge protector when the distortion time period begins, and (ii) the time between a zero crossing of the measured voltage across the surge protector and when the distortion time period of the measured voltage across the surge protector begins; modifying samples of the measured voltage across the surge protector taken during the time period based on the peak voltage; a processor configured to: The electricity meter (400) of claim 8 or 9.

16. the power supply (460, 560, 660) comprises at least one rectifier and / or regulator circuit configured to supply power to the measurement circuit (430); An electricity meter (400) according to any one of claims 1 to 15.

17. an actuatable switch (495) for selectively connecting a grid-side input of the power meter to a load-side output of the power meter; An electricity meter (400) according to any one of the preceding claims.

18. the measurement circuit (430) is configured to measure a load-side voltage at a load-side output of the actuatable switch (495); the measurement circuitry is configured to measure a load-side current at a load-side output of the actuatable switch; the voltage across the surge protector (455, 555) corresponds to the voltage at the grid-side input of the actuatable switch; The electricity meter (400) of claim 17.

19. The power meter (400) includes a control circuit (475) and a communication circuit; The control circuit (475) the voltage at the grid-side input measured by said measurement circuit (430); the load-side voltage measured by the measuring circuit, and / or Data received by the communication circuit configured to selectively activate the actuatable switch (495) based at least in part on The electricity meter (400) of claim 18.

20. A method of operating an electricity meter (400), comprising: The method includes configuring a measurement circuit (430) to measure a voltage across a surge protector (455, 555); the surge protector is configured to protect an input to a power source (460, 560, 660) configured to power the measurement circuit; method.

21. The method includes selectively operating an enable switch (495) of the electricity meter; the actuatable switch (495) is configured to selectively connect a grid-side input of the power meter to a load-side output of the power meter; 21. The method of claim 20.

22. Selectively activating the actuatable switch (495) comprises: the voltage at the grid-side input measured by said measurement circuit (430); the load-side voltage measured by the measuring circuit, and / or Data received by the communication circuit of the electricity meter Based at least in part on 22. The method of claim 21.

23. identifying a cogeneration scenario based on the load-side voltage and a voltage at the grid-side input of the power meter (400) while the actuatable switch (495) is configured to decouple the grid-side input of the power meter (400) from the load-side output of the power meter (400); Including, 22. The method of claim 21.

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