Electricity meter with grid-side voltage sensing

Abstract

An electricity meter (400) is disclosed. The electricity meter (400) includes a power source (460) for supplying electrical energy to the measurement circuit (430), and a surge protection device (455) for protecting an input (VALINE, VCLINE) of the power source. The measurement circuit is configured to measure a voltage across the surge protection device. A corresponding method of operating an electricity meter is also disclosed, the method comprising configuring a measurement circuit to measure a voltage across a surge protection device, where the surge protection device is configured to protect an input of a power source configured to supply electrical energy to the measurement circuit.

Description

[0001] Related Applications

[0002] This application claims priority to UK patent application serial number 2214709.4 filed on October 6, 2022 and UK patent application serial number 2305776.3 filed on April 19, 2023, the entire contents of which are incorporated herein. Technical Field

[0003] The present disclosure belongs to the field of electric meters used for metering electricity consumption in residential and commercial places, for example. In particular, the present disclosure relates to electric meters with grid-side voltage sensing function. Background Art

[0004] An electric meter, also known in the art as an energy meter, power meter or watt-hour meter, is a device that measures the amount of electrical energy consumed by one or more electrically powered devices over a time interval, such as in a residence or business.

[0005] Electricity meters are often installed in a facility for billing and monitoring consumption. In some examples, the meters may be manually read periodically to determine the level of energy consumption. In other examples, advanced meters, referred to in the art as "smart meters," may be configured to communicate with utility providers (e.g., wirelessly) to provide energy consumption information and / or receive billing information and / or control signals.

[0006] Electricity, such as electrical energy, can be delivered to a location via a variety of available service types, such as: single-phase three-wire, commonly used in residential locations in the U.S.; three-phase four-wire star (Wye), commonly used in commercial locations in the U.S.; and three-phase three-wire delta, commonly used in industrial facilities in the U.S. As is well known in the art, and described in further detail below, the different service types have associated meter formats, such as 2S, 3S, 5S, etc.

[0007] Electricity meters must be designed to be safe and robust. For example, an electricity meter must be able to withstand significant electrical surges. In one example, a lightning strike may induce a significant voltage spike and / or current surge at the input of the electricity meter. In another example, a short circuit of one or more loads coupled to the electricity meter may induce a significant voltage spike and / or current surge.

[0008] Furthermore, in use, the meter must be able to monitor both the "load side" voltage and the "grid side" voltage. Specifically, a meter that implements a service disconnect switch between the load side and the grid side of the meter for selectively disconnecting the grid side power supply from the load side load may require accurate measurement of both the load side voltage and the grid side voltage before the power supply is reconnected.

[0009] The load side of an electricity meter may refer to the connection of the electricity meter to an electrical energy consuming load. The grid side of an electricity meter may refer to the connection of the electricity meter to a power supply line from a utility supplier (eg, from an electrical network).

[0010] To ensure adequate reliability of the meter, expensive components and considerable printed circuit board (PCB) spacing may be required to withstand large voltage surges on both the load-side voltage connection and the grid-side voltage connection, both of which the meter can measure. These characteristics may significantly increase the manufacturing cost of the meter.

[0011] It is therefore desirable to provide an electric meter that is relatively inexpensive to manufacture but is able to withstand large voltage surges on both the load-side voltage and the grid-side voltage while also enabling efficient metering of electric energy consumption and safe control of service disconnection functions.

[0012] It is therefore an object 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 disadvantages of the prior art. Summary of the invention

[0013] The present disclosure is in the field of electric meters for metering of electric power consumption, for example in residential and commercial premises. In particular, the present disclosure relates to electric meters with grid-side voltage sensing functionality.

[0014] According to a first aspect of the disclosure, there is provided an electric meter, the electric meter comprising: a power supply for supplying electric energy to a measurement circuit; and a surge protection device for protecting an input of the power supply. The measurement circuit is configured to measure a voltage across the surge protection device.

[0015] Advantageously, by implementing the measurement of the voltage across the surge protection device, the expensive resistor string typically dedicated to grid-side voltage measurement in prior art electricity meters can be eliminated, thereby reducing the overall manufacturing cost.

[0016] Instead, lower cost resistors can be placed across the surge protection device on the power supply to implement an alternative means of measuring the grid-side voltage.

[0017] In such a meter, voltage measurements for energy consumption metering purposes may instead be derived from a load-side resistor string that is otherwise used only to detect customer power generation.

[0018] Furthermore, advantageously, such a configuration enables the meter to maintain a reference to the grid side voltage even when the service disconnect switch is configured to disconnect the grid side from the load side. This may be particularly important for detecting co-generation scenarios, for example, when a user implements generation capability, since reconnection from the load side to the grid side during co-generation may result in catastrophic damage to the meter and / or may be dangerous.

[0019] By removing the expensive resistor strings on the grid side, the overall component count in the high voltage area of ​​the PCB within the meter can be reduced. In addition, board slots that may be required between voltage strings for electrical isolation purposes can also be removed.

[0020] This overall reduction in PCB space can help reduce the overall cost of the PCB through more efficient PCB panelization during manufacturing.

[0021] The surge protection device may include at least one of: a metal oxide varistor (MOV); a gas discharge tube (GDT); a transient voltage suppressor (TVS) diode; and / or a polymer positive temperature coefficient device (PPTC).

[0022] The input may include a first voltage input and a second voltage input. The surge protection device may be connected to a first node coupled to the first voltage input and a second node coupled to the second voltage input.

[0023] In some examples, multiple surge protection devices may be implemented. For example, in other embodiments falling within the scope of the present disclosure, more than two voltage inputs may be implemented. In some examples, each voltage input may be protected by at least one surge protection device.

[0024] In use, the first voltage input may comprise a first phase and the second voltage input may comprise a second phase that is out of phase with the first phase.

[0025] For example, the second phase may be anti-phase, ie, 180 degrees out of phase with the first phase.That is, in some embodiments, the meter may be configured for use with a single-phase, three-wire service type.

[0026] As described above, in other embodiments, more than two voltage inputs may be implemented. For example, in some embodiments, the meter may be configured for use with a three-phase, four-wire, star service type or a three-phase, three-wire, delta service type.

[0027] The electric meter may include a first voltage divider coupled to the first node and a second voltage divider coupled to the second node. The measurement circuit may be configured to measure a voltage at each of the first voltage divider and the second voltage divider to determine a voltage across the surge protection device.

[0028] The implementation of a voltage divider may provide an accurate, reliable means of measuring voltage, wherein the impedance of the voltage divider may be selected such that sufficient accuracy is provided without overloading the power supply line.

[0029] The first voltage divider and the second voltage divider may be configured to withstand a clamping voltage of the surge protection device.

[0030] That is, advantageously, the surge protection device can limit the magnitude of the surge across the power input. Thus, the first voltage divider and the second voltage divider need only be able to withstand the magnitude of the surge allowed by the surge protection device, rather than, for example, 10,000 volt protection or greater, which may otherwise be required to protect against surges caused by lightning strikes or the like.

[0031] Various embodiments of the voltage divider may be implemented. For example, at least one of the first voltage divider and the second voltage divider may include: a resistor voltage divider; a capacitor voltage divider or an inductor voltage divider.

[0032] In some embodiments, the electric meter may include a first linear transformer coupled to the first node and a second linear transformer coupled to the second node. The measurement circuit may be configured to measure a voltage at each of the first linear transformer and the second linear transformer to determine a voltage across the surge protection device.

[0033] That is, the linear transformer may provide a replacement for one or both voltage dividers, thereby providing the measurement circuit with an alternative means of determining the voltage across the surge protection device.

[0034] The electricity meter may also include a surge protection element between the first voltage input and the first node.

[0035] The surge protection element may be a resistor.

[0036] In some embodiments, the measurement circuit may include a processor configured to: obtain a sample of the measured voltage across the surge protection device; detect the start time of a time period in which the measured voltage across the surge protection device is distorted; obtain a current value at the power input terminal during the time period; determine a voltage drop across the surge protection device during the time period using the current value; and modify the sample of the measured voltage across the surge protection device obtained during the time period based on the voltage drop across the surge protection device during the time period.

[0037] The electric meter may further comprise a current sensing device arranged to output said current value. Advantageously, an accurate current value at the input terminal of the power supply during the time period may be obtained. The current sensing device may be connected between the first node and the input terminal.

[0038] Alternatively, the current value may be pre-stored in a memory accessible to 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 for a current sensing device, thereby saving PCB space. The processor may be configured to retrieve the current value from the memory based on the operating mode of the meter.

[0039] In some embodiments, the measurement circuit may include a processor configured to: obtain a sample of the measured voltage across the surge protection device; detect a start time of a time period of distortion of the measured voltage across the surge protection device; determine a voltage peak value during the time period of distortion using: (i) the measured voltage across the surge protection device at the start of the time period of distortion, and (ii) a time between a zero crossing point of the measured voltage across the surge protection device and the start time of the time period of distortion of the measured voltage across the surge protection device; and modify the sample of the measured voltage across the surge protection device obtained during the time period based on the voltage peak value.

[0040] The power supply may include at least one rectifier and / or regulator circuit configured to supply electrical energy to the measurement circuit.

[0041] For example, the power supply may include a rectifier (eg, a bridge rectifier) ​​configured to provide a DC output from an AC input at the power supply input.

[0042] The power supply can provide alternating current or rectified direct current to one or more regulators. For example, one or more regulators can be configured to provide a voltage range suitable for the operation of different components of the smart meter. As a non-limiting example, the power supply can be configured to provide a 24 volt DC supply for the actuator of the service disconnect switch, a 5 volt DC supply for the transceiver driver, and a relatively low voltage 3.3 volt DC supply for the microprocessor circuit, etc.

[0043] The electricity meter may include an actuatable switch for selectively coupling a grid-side input of the electricity meter with a load-side output of the electricity meter.

[0044] Such an actuatable switch may be referred to in the art as a “service disconnect switch.” As further described below, in an embodiment, the service disconnect switch may be operated under remote control (eg, by a utility provider) to connect or disconnect the load side from the grid side at the site.

[0045] The measurement circuit may be configured to measure a load-side voltage at a load-side output of the actuatable switch.

[0046] Measuring the load-side voltage allows detecting co-generation activities, for example by using generators or solar panels, before reconnecting the load side to the grid side via the service disconnect switch, thus increasing the safety level of the meter operation.

[0047] The measurement circuit may be configured to measure a load-side current at a load-side output of the actuatable switch.

[0048] The voltage across the surge protection device may correspond to the voltage at the grid-side input of the actuatable switch.

[0049] Before reconnecting the load side to the grid side via the service disconnect switch, a comparison of the grid side and load side voltages may be performed to increase the safety level of the meter operation. This comparison may be performed by processing circuitry within the meter, or by one or more remote devices, such as networked devices operated by a utility provider.

[0050] The electric meter may include a control circuit.

[0051] The control circuitry may include one or more processors.

[0052] The measurement circuit 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 circuit. The analog front end may be configured to perform analog measurements of load-side and / or grid-side voltages and / or currents and convert these measurements into digital signals for transmission to the control circuit.

[0053] The electric meter may include a communication circuit. For example, the electric meter may include a transceiver configured to communicate with a remote device. In an example, the communication circuit may be configured as a node in a mesh network including a plurality of electric meters. In an example, the communication circuit may be configured to transmit data to a utility provider, wherein the data may relate to power consumption and / or voltage levels on the grid side and / or the load side of the electric meter. In an example, the communication circuit may also be configured to receive a signal or data for controlling the operation of a service disconnect switch.

[0054] The control circuit may be configured to selectively actuate the actuatable switch based at least in part on: a voltage at a grid-side input measured by the measurement circuit; a load-side voltage measured by the measurement circuit; and / or data received by the communication circuit.

[0055] Advantageously, the control circuit, or a remote device in communication with the control circuit, may be able to identify any co-generation activity prior to configuring an actuatable switch (eg, a service disconnect switch) to reconnect the load side and the grid side of the meter.

[0056] According to a second aspect of the present disclosure, a method of operating an electric meter is provided. The method includes configuring a measurement circuit to measure a voltage across a surge protection device, wherein the surge protection device is configured to protect an input of a power supply configured to supply power to the measurement circuit.

[0057] The method may include selectively operating an actuatable switch of the electricity meter.The switch may be configured to selectively couple a grid-side input of the electricity meter to a load-side output of the electricity meter.

[0058] Selective actuation of the actuatable switch may be based at least in part on: a voltage at a grid-side input measured by a measurement circuit; a load-side voltage measured by a measurement circuit; and / or data received by a communication circuit of the meter.

[0059] The method may include identifying a co-generation scenario based on a load-side voltage and a voltage at the grid-side input when the actuatable switch is configured to decouple a grid-side input of the meter from a load-side output of the meter.

[0060] The above content of the invention is intended to be exemplary and non-limiting only. The present disclosure includes one or more corresponding aspects, embodiments or features, existing alone or in various combinations, whether or not specifically described (including claimed) in that combination or alone. It should be understood that the features defined above according to any aspect of the present disclosure or the features below related to any specific embodiment of the present disclosure can be used alone or in combination with any other defined features in any other aspect or embodiment of the present disclosure, for, or to form further aspects or embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0062] Figure 1 A block diagram of a prior art electric meter connected in series with a load is described, the electric meter having a 2S form;

[0063] Figure 2 Another example of a prior art electricity meter is described;

[0064] Figure 3 An example of a prior art circuit from an electric meter is described;

[0065] Figure 4 An electric meter according to an embodiment of the present disclosure is described, wherein a measurement circuit is configured to measure a voltage across a surge protection device;

[0066] Figure 5 An example of a circuit from an electric meter according to an embodiment of the present disclosure is described;

[0067] Figure 6 An alternative example of a circuit from an electric meter according to another embodiment of the present disclosure is described;

[0068] Figure 7 Shown in Figure 5 The distorted grid-side voltage waveform measured in the circuit shown;

[0069] Figure 8 The grid-side voltage waveform appearing on the grid is shown;

[0070] Fig. 9 Describes the Figure 4 A schematic block diagram of an analog front-end circuit used in a measurement circuit;

[0071] Fig.10a is to show that when the processor of the analog front-end circuit knows Figure 5 A flowchart of a method that the processor may perform when the current at the power input terminal of the circuit is measured;

[0072] Fig.10b Shown in Figure 5 Example current waveforms at the power supply input of the illustrated circuit;

[0073] Fig.11 is to show that when the analog front-end circuit processor does not know Figure 5 A flowchart of a method that the processor may perform when the current at the power input terminal of the circuit is measured;

[0074] Fig.12 is a flow chart showing a method that a processor of an analog front end circuit may execute to detect the onset of distortion caused by clipping; and

[0075] Fig.13 Shown in Figure 5 A distorted grid-side voltage waveform measured in a circuit, and a second-order derivative waveform calculated from the distorted grid-side voltage waveform. DETAILED DESCRIPTION

[0076] Figure 1 A block diagram of a prior art electricity meter 100 is depicted. For purposes of illustration, the prior art electricity meter 100 is configured as a 2S form service type electricity meter, which is a meter configured for single phase three wire service.

[0077] A prior art electric meter 100 is installed in series with a load 105, which for purposes of illustrating a residential load is depicted as a house.

[0078] In use, the high voltage power line 110 can provide power supply from the grid (ie, from a utility company). The transformer 115 can reduce the voltage on the power line 110 to a voltage suitable for the load 105, such as 240 volts or 110 volts, or similar values.

[0079] In the example electric meter 100, the first input terminal 120a is connected to a power supply voltage having a first phase from the transformer 115, and the second input terminal 120c is connected to a power supply voltage having a second phase from the transformer 115. The second phase is out of phase with the first phase. For example, the second phase can be in reverse phase, such as 180 degrees out of phase with the first phase. The first input terminal 120a may be referred to in the art as a "Phase A" input. The second input terminal 120c may be referred to in the art as a "Phase C" input.

[0080] The first output terminal 140 a and the second output terminal 140 c are connected to the load 105 , and thus can provide power to the load 105 .

[0081] The example electric meter 100 includes a first actuable switch S1 and a second actuable switch S2. The first actuable switch S1 can selectively disconnect / connect a first grid-side input terminal 120a from a first load-side output terminal 140a. The second actuable switch S2 can selectively disconnect / connect a second grid-side input terminal 120c from a second load-side output terminal 140c.

[0082] In use, the first actuatable switch S1 and the second actuatable switch S2 may be collectively referred to as "service disconnect switches" and may be configured to selectively connect / disconnect the load side and the grid side of the electric meter 100. That is, the first actuatable switch S1 may selectively couple the first input terminal 120a with the first output terminal 140a, and the second actuatable switch S2 may selectively couple the second input terminal 120c with the second output terminal 140c.

[0083] The example electricity meter 100 includes a measurement circuit 130. The measurement circuit 130 includes an analog front end (in Figure 1 The measurement circuit 130, in particular the AFE, may include an analog-to-digital converter, an anti-aliasing filter, etc. The analog front end may be communicatively coupled to the control circuit and / or the processing circuit (not shown). As further described below, the analog front end may be configured to perform analog measurements of the grid-side voltage and / or the load-side voltage and / or current, and convert these measurements into digital signals for transmission to the control circuit.

[0084] The “Phase A” input voltage level at the first input 120a (eg, at the grid side of the first actuatable switch S1 ) may be measured by the measurement circuit 130 (eg, by sensing a voltage across a resistor string (not shown) at a first node 135a coupled to the first input 120a ).

[0085] The “Phase C” input voltage level at the second input 120c (eg, at the grid side of the second actuatable switch S2) may be measured by the measurement circuit 130 (eg, by sensing a voltage across a resistor string (not shown) at a second node 135c coupled to the second input 120c).

[0086] The “Phase A” output voltage level at the first output terminal 140a (eg, at the load side of the first actuatable switch S1) may be measured by the measurement circuit 130 (eg, by sensing a voltage across a resistor string (not shown) at a third node 145a coupled to the first output terminal 140a).

[0087] The “Phase C” output voltage level at the second output terminal 140c (e.g., at the load side of the second actuatable switch S2) can be measured by the measurement circuit 130 (e.g., by sensing the voltage across a resistor string (not shown) at a fourth node 145c coupled to the second output terminal 140c).

[0088] The electric meter 100 further comprises a first current transformer 150a for providing a signal corresponding to the “phase A” current on the load side of the first actuatable switch S1 to the measurement circuit 130 .

[0089] The electricity meter 100 further comprises a second current transformer 150 c for providing a signal corresponding to the phase C current on the load side of the second actuatable switch S2 to the measurement circuit 130 .

[0090] Figure 2 A more detailed example of a prior art electricity meter 200 is depicted, which generally corresponds to Figure 1 2S form electricity meter 100 is shown in FIG. 1 , but specific components of electricity meter 200 are shown in greater detail.

[0091] The prior art electricity meter 200 is installed in series between the grid 215 and the load 205 .

[0092] In the example electricity meter 200 , the first input 220 a is connected to a supply voltage having a first phase from the grid 215 , and the second input 220 c is connected to a supply voltage having a second phase from the grid 215 , where the second phase is out of phase with the first phase.

[0093] The first input terminal 220 a and the second input terminal 220 c may be provided at a service entrance of the electric meter 200 .

[0094] The first input 220a may be referred to in the art as a "Phase A" input. The second input 220c may be referred to in the art as a "Phase C" input.

[0095] The first output terminal 240 a and the second output terminal 240 c are connected to the load 205 , and thus can provide power to the load 205 .

[0096] The example electric meter 200 includes a service disconnect switch 295 that can selectively disconnect / connect the grid 215 from the load 205 .

[0097] The electric meter 200 includes an actuator 265 , which may include, for example, a solenoid or the like, for actuating a service disconnect switch 295 .

[0098] The example electric meter 200 includes a measurement circuit 230. The measurement circuit 230 includes an analog front end 270. The measurement circuit 230, and in particular the analog front end 270, may include an analog-to-digital converter, an anti-aliasing filter, etc. In an example, the analog front end 270 is communicatively coupled to a digital circuit 275. The analog front end 270 may be configured to perform analog measurements of grid-side voltage and load-side voltage and current, and convert these measurements into digital signals for processing by the digital circuit 275. In some examples, data corresponding to the processed measurements may be transmitted to a remote device, such as another electric meter in a mesh network, via the digital circuit 275, which may include, for example, a communication circuit of a transceiver.

[0099] Grid voltage sensing circuit 280G, denoted as V_SENSE GRID , configured to determine the voltage on the first input terminal 220a and the second input terminal 220c, thereby providing a grid-side voltage measurement. The grid voltage sensing circuit 280G can be implemented using a relatively expensive resistor string (not shown), which will be referred to below. Figure 3 Such expensive resistor strings can withstand considerable voltage spikes and current surges (such as may be caused by lightning strikes). Such resistor strings can significantly increase the overall manufacturing cost of the meter 200. The grid voltage sensing circuit 280G is coupled to the analog front end 270 to enable measurement of the grid side voltage.

[0100] and Figure 1 Similar to the electric meter 100 in FIG. 1 , the electric meter 200 also includes a load voltage sensing circuit 280L, denoted as V_SENSE LOAD , for sensing the voltage across the load 205 on the load side of the service disconnect switch 295. The load voltage sensing circuit 280L is also coupled to the analog front end 270 to enable measurement of the load side voltage. The load voltage sensing circuit 280L can also implement a relatively expensive resistor string.

[0101] The “Phase A” current flowing from the first input terminal 220a to the load 205 can be measured using the first current sensing circuit 290a to determine the power consumption of the load 205, denoted as I_SENSEPHASE_A The first current sensing circuit 290 a may include a current transformer. The first current sensing circuit 290 a is coupled to the measurement circuit 230 (eg, to one or more ADC channels of the analog front end 270 ).

[0102] The “Phase C” current flowing from the second input terminal 220c to the load 205 can be measured using the second current sensing circuit 290c to determine the power consumption of the load 205, denoted as I_SENSE PHASE_A The second current sensing circuit 290 c may include a current transformer. The second current sensing circuit 290 c is coupled to the measurement circuit 230 (eg, to one or more ADC channels of the analog front end 270 ).

[0103] The electric meter 200 includes a power supply 260. The power supply 260 receives power from the power 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 electric meter 200. In an example, the power supply 260 provides power to the actuator 265. The power supply 260 also provides power to the measurement circuit 230. In an 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 (e.g., a bridge rectifier) ​​configured to provide a direct current output from an alternating current input at the input of the power supply 260. The power supply 260 may include one or more regulators configured to provide a voltage range suitable for the operation of different components of the smart meter. For example, power supply 260 may be configured to provide a 24 V DC power supply to actuator 265 , a 5 V DC power supply to analog front end 270 , and a 3.3 V DC power supply to microprocessor circuits in digital circuit 275 .

[0104] Figure 3 An example of a circuit 300 from a prior art electricity meter (eg, electricity meter 100 , 200 ) having a 2S format is described.

[0105] The input terminal 320c may correspond to Figure 1 and Figure 2 A further input terminal 320n is also described which may be coupled to a neutral line when in use.

[0106] 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 used to measure the voltage at input 320c.

[0107] A resistor string 345c including resistors R1 to R6 is coupled to the input terminal 320c. In use, the voltage across the resistor string R1 to R6 can be used to measure the voltage at the input terminal 320c (e.g., on the grid side of the service disconnect switch 295 in the electric meter 200). Such a resistor string 345c may be expensive to implement and may occupy a large amount of PCB space, resulting in cost and product form factor limitations.

[0108] Will understand, Figure 3 The circuit 300 in FIG. 3 is provided for exemplary purposes only, and different meter formats may implement different resistor string configurations. For example, for a "single" phase format such as a 2S meter format, resistors R7 to R12 may be set. For a "multi-phase" meter format such as a 12S meter format, resistors R1 to R6 may be set. In addition, for the 12S meter format, resistors R7 to R11 may be set to a 0 ohm value to tie the other input terminal 320n coupled to the neutral line to AGND. Thus, different meter formats may implement different configurations of relatively expensive resistor strings.

[0109] Figure 4 An electric meter 400 according to an embodiment of the present disclosure is described, wherein a measurement circuit 430 is configured as an electric meter to measure a voltage across a surge protection device 455 of a power source 460 .

[0110] The electric meter 400 is installed in series between the power grid 415 and the load 405. In this example electric meter 400, a first input terminal 420a is connected to a power supply voltage having a first phase from the power grid 415, and a second input terminal 420c is connected to a power supply voltage having a second phase from the power grid 415, wherein the second phase is out of phase with the first phase. The first input terminal 420a and the second input terminal 420c may be provided at a service entrance of the electric meter 400.

[0111] The first input 420a may be referred to in the art as a "Phase A" input. The second input 420c may be referred to in the art as a "Phase C" input.

[0112] The first output terminal 440 a and the second output terminal 440 c are connected to the load 405 , and thus can provide power to the load 405 .

[0113] The example electric meter 400 includes a service disconnect switch 495 that can selectively disconnect / connect the grid 415 from the load 405 .

[0114] The electric meter 400 includes an actuator 465 , which may include, for example, a solenoid, for actuating a service disconnect switch 495 .

[0115] The example electric 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 an 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 voltage and load-side voltage and current, and convert these measurements into digital signals for processing by the digital circuit 475. In some examples, data corresponding to the processed measurements may be transmitted to a remote device, such as another electric meter in a mesh network, via the digital circuit 475, which may include, for example, a communication circuit of a transceiver.

[0116] and Figure 2 Similar to the electric meter 200 in FIG. 1 , the electric meter 400 includes a load voltage sensing circuit 480L, denoted as V_SENSE LOAD , for sensing the voltage across the load 405 on the load side of the service disconnect switch 495. The load voltage sensing circuit 480L is also coupled to the analog front end 470 to enable measurement of the load side voltage. The load voltage sensing circuit 480L can also implement a relatively expensive resistor string.

[0117] The “Phase A” current flowing from the first input terminal 420a to the load 405 can be measured using the first current sensing circuit 490a to determine the power consumption of the load 205, denoted as I_SENSE PHASE_A The first current sensing circuit 490 a may include a current transformer. The first current sensing circuit 490 a is coupled to the measurement circuit 430 (eg, to one or more ADC channels of the analog front end 270 ).

[0118] The “Phase C” current flowing from the second input terminal 420c to the load 405 can be measured using the second current sensing circuit 490c to determine the power consumption of the load 405, denoted as I_SENSE PHASE_A The second current sensing circuit 490 c may include a current transformer. The second current sensing circuit 490 c is coupled to the measurement circuit 430 (eg, to one or more ADC channels of the analog front end 470 ).

[0119] The electric meter 400 includes a power supply 460. The power supply 460 receives power from the power 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 electric meter 400. In an example, the power supply 460 provides power to the actuator 465. The power supply 460 also provides power to the measurement circuit 430. In an example, 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 (e.g., a bridge rectifier) ​​configured to provide a direct current output from an alternating current input at the input of the power supply 460. The power supply 460 may include one or more regulators configured to provide a voltage range suitable for the operation of different components of the smart meter. For example, power supply 460 may be configured to provide a 24 V DC power supply to actuator 465 , a 5 V DC power supply to analog front end 470 , and a 3.3 V DC power supply to microprocessor circuits in digital circuit 475 .

[0120] A surge protection device 455 is provided at the input of the power supply 460. The surge protection device 455 is configured to protect the input of the power supply from surges in voltage and / or current caused by lightning strikes, short circuits, and the like.

[0121] In a preferred embodiment, the surge protection device 455 can be implemented as a metal oxide varistor (MOV). In other embodiments, the surge protection device can include at least one of the following: a gas discharge tube (GDT); a transient voltage suppressor (TVS) diode; and / or a polymer positive temperature coefficient device (PPTC).

[0122] Although reference is made to a single surge protection device 455, it will be appreciated that multiple surge protection devices may be implemented in embodiments falling within the scope of the present disclosure.

[0123] Surge protection device 455 may limit the voltage seen at the power input.

[0124] Grid voltage sensing circuit 480G, denoted as V_SENSE GRID , configured to determine the voltage across the surge protection device 455, thereby providing a grid-side voltage measurement.

[0125] As referenced below Figure 5 Described in detail, Figure 2 The grid voltage sensing circuit 280G in the Figure 4 In the embodiment of the present invention, the grid voltage sensing circuit 480G does not require an expensive resistor string.

[0126] The grid voltage sensing circuit 480G is coupled to the analog front end 470 to implement the measurement of the grid side voltage. By implementing the measurement of the grid side voltage across the surge protection device 455, the expensive resistor string (e.g., Figure 3 The resistor strings 345 a and 345 c described in will be removed to reduce the overall manufacturing cost of the electricity meter 400.

[0127] That is, because the surge protection device 455 limits the voltage at the power input, the grid voltage sensing circuit 480G only needs to be able to withstand the maximum voltage allowed by the surge protection device 455 .

[0128] In such an electric meter 400, voltage measurements for power consumption metering can be derived from the load-side resistor string using a load voltage sensing circuit 480L that is otherwise used only to detect customer power generation.

[0129] In use, the measurement circuit 430 may be configured to measure the voltage across the surge protection device 455 to provide an indication of the grid-side voltage.

[0130] In use, operation of the service disconnect switch 495 to selectively couple the grid-side input of the meter with the load-side output of the meter may be based on the grid-side voltage measured across the surge protection device 455 .

[0131] That is, selective actuation of service disconnect switch 495 may be based at least in part on: a voltage at a grid-side input measured by measurement circuit 430 ; a load-side voltage measured by measurement circuit 430 ; and / or data received by communication circuitry of electric meter 400 .

[0132] In certain examples, when actuatable switch 495 is configured to decouple the grid-side input of meter 400 from the load-side output of the meter, a cogeneration scenario may be identified based on a comparison of the load-side voltage and the voltage at the grid-side input.

[0133] Figure 5 Described is a method for generating a signal from an electric meter (e.g., Figure 4 An example of a circuit 500 of an electric meter 400 ).

[0134] exist Figure 5 In the example circuit of , “VA_LINE” represents an input coupled to a first input terminal (eg, first input terminal 420 a ), and “VC_LINE” represents an input coupled to a second input terminal (eg, second input terminal 420 c ).

[0135] The first output, denoted as "U1", may be an input to a measurement circuit, such as measurement circuit 430. The second output, denoted as "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 of measurement circuit 430.

[0136] In the example circuit, the power supply 560 is implemented as a bridge rectifier. That is, the power supply 560 can be configured to provide DC power for other features of the meter. In the example, the power supply 560 can correspond to Figure 4 The power supply of the electric meter is 460.

[0137] A surge protection device 555 is provided across the power input. In the example circuit 500, the surge protection device 555 is implemented as a varistor, such as an MOV. The surge protection device 555 may correspond to Figure 4 The surge protection device 455 of the electricity meter 400.

[0138] In the example circuit 500, a grid voltage sensing circuit 580G is provided. The grid voltage sensing circuit 580G may correspond to Figure 4 The grid voltage sensing circuit 480G of the electric meter 400. The surge protection device 555 is coupled to the first node 505a and the second node 505c of the grid voltage sensing circuit 580G.

[0139] The first voltage divider 510a is coupled to the first node 505a and the second voltage divider 510c, and the second voltage divider 510c is coupled 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. Therefore, the measurement circuit 430 having U1 and U3 as inputs can be configured to measure the voltage at each of the first voltage divider 510a and the second voltage divider 510c to determine the voltage across the surge protection device 555.

[0140] In the example circuit 500, a surge protection element in the form of resistor R36 502 is included as an additional lightning surge resistor. Figure 5 As shown, resistor R36 502 is placed between the first voltage input (VA_LINE) and the first node (505a). Resistor R36 502 is placed before the surge protection device 555 to limit the current flowing into the surge protection device 555 when a surge event occurs. Resistor R36 502 can be, for example, between 47 and 100 ohms. The rating of resistor R36 502 can be, for example, between 2 and 5 watts.

[0141] In the example circuit 500, resistor R3 is included as a balancing resistor to account for the supply current draw that offsets the AGND point of the 2S meter.

[0142] although Figure 5 The first voltage divider 510a and the second voltage divider of the circuit 500 are resistive voltage dividers, and it will be understood that in other embodiments, other types of voltage dividers may be implemented. For example, in an embodiment, one or both of the first voltage divider 510a and the second voltage divider 510c may be implemented as a capacitive voltage divider or an inductive voltage divider. In addition, in another example, one or both of the first voltage divider 510a and the second voltage divider 510c may be replaced by a linear transformer to determine the voltage across the surge protection device 555.

[0143] Figure 6 A method for using an electric meter (e.g. Figure 4 An example of an alternative circuit 600 for the electric meter 400 in FIG.

[0144] Features of circuit 600 generally correspond to features of circuit 500 and therefore are not described in further detail for the sake of brevity.

[0145] However, with Figure 5 Compared with the circuit 500 in Figure 6 In the circuit 600 of FIG. 5 , resistor R36 502 is replaced by a surge protection element in the form of an inductor, designated “L36” 602. Advantageously, inductor L36 602, which replaces resistor R36 502, may also be used to limit surge current and may reduce distortion of the measured voltage due to any current draw by power supply 660.

[0146] In this regard, the inventors have identified methods of compensating for distortion in the measured voltage in the example circuit 500 in which a surge protection element is employed. These methods are particularly advantageous when the surge protection element is in the form of a surge resistor R36 502. As power is drawn into the power supply 560, a voltage drop occurs across the surge resistor R36 502 due to the peak of the grid-side voltage as the grid-side voltage begins to conduct through the diode of the power supply 560 and then recharges the bulk capacitor (not shown in the figure), which results in distortion in the sensed grid-side voltage that does not accurately reflect the voltage on the grid. The bulk capacitor is not shown in the figure, but can be placed Figure 5 and Figure 6 Between TP6 and TP7 in the

[0147] Figure 7 Shows that it can be Figure 55. The distorted grid-side voltage waveform 700 measured by the grid voltage sensing circuit 580G in FIG. As shown in the figure, due to the power drawn by the power source 560, the distorted grid-side voltage waveform 700 experiences a clipping effect during the distorted time period Tp.

[0148] Figure 8 800 is a grid-side voltage waveform that appears on the grid. Figure 8 In comparison, it can be seen from the distorted grid-side voltage waveform 700 that due to the distortion introduced by resistor R36 502, the peak voltage V pk Not accurately sensed by the grid voltage sensing circuit 580G.

[0149] Fig. 9 Describes the Figure 4 The schematic block diagram of the analog front-end circuit 970 used in the measurement circuit of the embodiment of the present invention to realize the measurement of the grid side voltage. The analog front-end circuit 970 may correspond to Figure 4 The analog front end circuit 470 of the electricity meter 400 is shown.

[0150] like Fig. 9 As shown, the first output "U1" and the second output "U3" are processed before being supplied in digital form to the processor 906. The first output "U1" and the second output "U3" may optionally be supplied as inputs to anti-aliasing filters 902, 912 before being supplied to respective analog-to-digital converters (ADCs) 904, 914.

[0151] According to an embodiment of the present disclosure, the processor 906 is arranged to process the digital first output “ U1 ” and second output “ U3 ” sense outputs conveying the grid side voltage to compensate for the distortion introduced by the surge resistor R36 502 .

[0152] The functions of the processor 906 described herein can be implemented by being stored on a memory (e.g., memory 910) including one or more storage media, and being arranged for code (e.g., instructions) executed on a processor including one or more processing units. The storage medium may be integrated into the processor 906 and / or separated from the processor 906. The code is configured to perform operations consistent with the embodiments discussed herein when extracted from the memory and executed on the processor. When the instructions are executed by the processor, the processor may be caused to perform any method described herein. These instructions may be provided on a non-temporary computer-readable medium. These instructions may be provided on a carrier of a programmed memory such as a disk, CD-ROM or DVD-ROM, such as a read-only memory (firmware), or on a data carrier such as an optical or electrical signal carrier. Alternatively, it is not excluded that some or all of the functions of the processor 906 are implemented in a dedicated hardware circuit (e.g., ASIC, simple circuit, gate circuit, logic circuit, and / or configurable hardware circuit, such as FPGA).

[0153] In some embodiments of the present disclosure, the processor 906 is arranged to use knowledge of the current at the input of the power supply 560 to compensate for the distortion introduced by the surge resistor R36 502. In other embodiments, the processor 906 is arranged to compensate for the distortion introduced by the surge resistor R36 502 without knowledge of the current at the input of the power supply 560. The input of the power supply 560 mentioned above may correspond to Figure 5 Input terminal 590 or input terminal 595 shown in .

[0154] First reference Fig.10a , describes an embodiment in which the processor 906 is arranged to use knowledge of the current at the input of the power supply 560 to compensate for the distortion introduced by the surge resistor R36 502 .

[0155] Fig.10a is a flow chart illustrating a method 1000 that may be performed by the processor 906 of the analog front end circuit 970 .

[0156] like Fig.10a As shown, in step S1002, the processor 906 obtains a voltage sample (measured grid-side voltage waveform) across the surge protection device 555 based on receiving the digital first output "U1" and the second output "U3". The measured grid-side voltage waveform can be obtained by Figure 5 Measured by the grid voltage sensing circuit 580G.

[0157] In step S1004, the processor 906 detects the time t (eg, Figure 7The processor 906 may use a variety of techniques to perform step S1004. An example technique is described below with reference to Fig.12 A more detailed description is given.

[0158] In step S1006, the processor 906 obtains the current (I PS ).

[0159] In some embodiments, the circuit 500 includes a circuit operable to measure a current (I PS ) of the current sensing device. In these embodiments, the processor 906 obtains the current (I PS ). The current sensing device can be a resistor, a Hall effect current sensor, or a magnetoresistive sensor.

[0160] The input terminal of the power supply 560 may correspond to Figure 5 590 shown in . In order to ensure that all power supply currents at the input terminal 590 of the power supply 560 are measured, the current sensing device is preferably located between the first node 505a and the input terminal 590 of the power supply 560 (for example, the current sensing device can be located at the node TP2, or between the nodes TP2 and TP4 of the circuit 500). In some embodiments, the current sensing device can be placed in series with the differential mode choke L24. The circuit 500 may include a differential mode choke L24 to prevent the conducted emissions generated by the power supply 560 from flowing back to the power grid. In other embodiments, the current sensing device can be placed in series with one or both of the resistors R684 and R685, or replace one or both of the resistors R684 and R685. In a further embodiment, the current sensing device may correspond to a combination of a differential mode inductor L24 and resistors R684 and R685 in parallel.

[0161] The input terminal of the power supply 560 may correspond to Figure 5 Specifically, the current sensing device can be located between the second node 505c and the input terminal 595 of the power supply 560 (eg, the current sensing device can be located at the node TP5).

[0162] Fig.10b The current (I PS )1050.

[0163] In other embodiments, the processor 906 obtains the current (I PS Specifically, the memory may store one or more predefined current profiles, the predefined current profiles including the expected current (I PS ) is related to the data of the grid-side voltage change over time. Each of the one or more predefined current profiles may be associated with an operating mode of the meter (e.g., a radio transmission operating mode, a service disconnection operating mode, a transmitter in a receiving mode, or a firmware update mode), and the processor 906 may be configured to retrieve the predefined current profile corresponding to the operating mode of the meter. In these embodiments, it will be appreciated that the current (I PS ) is not measured. Instead, the processor 906 is configured to determine the current (I PS ). Fig.10b The current (I PS ) 1050. In these embodiments, the processor 906 may perform step S1006 before, during, or after the distorted time period Tp expires.

[0164] In step S1008, processor 906 uses (i) the current (I PS ), and (ii) the impedance of the surge resistor R36 502 to determine the voltage drop across the surge resistor R36 502 during the distorted time period Tp (e.g., using the equation V=IR). It will be appreciated that the voltage drop across the surge resistor R36 502 will vary during the distorted time period Tp.

[0165] In step S1010, the processor 906 is configured to modify the samples of the measured voltage across the surge protection device 555 acquired during the distorted time period Tp based on the voltage drop across the surge protection device during the distorted time period Tp. That is, for each sample of the measured voltage across the surge protection device 555 acquired during the distorted time period Tp, the processor 906 is configured to compensate for the distortion by adding the voltage drop that occurred when the sample was acquired to the measured voltage to accurately reflect the voltage that appears on the power grid.

[0166] Step S1008 may be performed dynamically during the distorted time period Tp. Alternatively, step S1008 may be performed after the distorted time period Tp expires. Step S1010 may be performed dynamically during the distorted time period T. Alternatively, step S1010 may be performed after the distorted time period Tp expires.

[0167] refer to Fig.11 Referring to the flowchart shown in , an embodiment in which the processor 906 is arranged to compensate for the distortion introduced by the surge resistor R36 502 when it has no knowledge of the current at the input of the power supply 560 is now described.

[0168] Fig.11 is a flow chart illustrating a method 1100 that may be performed by the processor 906 of the analog front end circuit 970 .

[0169] like Fig.11 As shown, in step S1102, the processor 906 obtains a voltage sample (measured grid-side voltage waveform) across the surge protection device 555 based on receiving the digital first output "U1" and the second output "U3". The measured grid-side voltage waveform can be obtained by Figure 5 The grid voltage is measured by the grid voltage sensing circuit 580G.

[0170] In step S1104, the processor 906 detects the time t (eg, Figure 7 The processor 906 may use a variety of techniques to perform step S1004. An example technique is described below with reference to Fig.12 A more detailed description is given.

[0171] In step S1106, the processor 906 is configured to determine the voltage V across the surge protection device 555 at the time t when the grid-side voltage waveform distortion period Tp begins. t .

[0172] In step S1108, the processor 906 is configured to use the voltage V t and time t to determine the voltage peak value V during the distorted time period Tp pk (The peak voltage V pk It can be a positive voltage peak or a negative voltage peak). The voltage peak V pk The portion of the grid-side voltage sample measured during the distorted time period Tp that is clipped due to the distortion introduced by the resistor R36 502. Specifically, the processor 906 can convert the voltage V t and time t should be applied to the following formula to determine the peak voltage V pk :

[0173] V pk =V t / arcsine(2πf*t)

[0174] Wherein f is the fundamental frequency of the measured grid-side voltage. As explained below, the fundamental frequency f may be detected during step S1104 as part of the process of detecting the time t at which the distorted time period Tp begins. Alternatively, the processor 906 may be configured to detect the fundamental frequency f as a separate step from step S1104.

[0175] In step S1110, the processor 906 is configured to pk The samples of the measured voltage across the surge protection device 555 taken during the distorted time period Tp are modified to compensate for the distortion introduced by the surge resistor R36 502 .

[0176] For example, processor 906 may use a curve fitting technique to determine the respective voltages that need to be added to the samples of the measured voltage during the distorted time period Tp to accurately reflect the voltage present on the grid using: (i) samples of the measured voltage across surge protection device 555 taken before the distorted time period Tp; (ii) the voltage peak value V pk ; and (iii) a sample of the measured voltage across the surge protection device 555 taken after the distorted time period Tp.

[0177] For each sample of the measured voltage across the surge protection device 555 taken during the distorted time period Tp, the processor 906 may be configured to compensate for the distortion by adding the voltage (determined for that sample using curve fitting techniques) to the measured voltage to accurately reflect the voltage appearing on the grid.

[0178] Fig.12 is a flowchart showing a method that the processor 906 of the analog front end circuit 970 may execute in steps S1004 and / or S1104 to detect the time t at which the distortion time period Tp of the grid-side voltage waveform starts.

[0179] In step S1202 , the processor 906 is configured to process samples of the voltage across the surge protection device 555 (the measured grid-side voltage waveform) to detect the fundamental frequency f.

[0180] In step S1204, the processor 906 is configured to process samples of the voltage across the surge protection device 555 (the measured grid-side voltage waveform) to detect the zero-crossing point of the fundamental frequency (for example, the point where the sign of the measured grid-side voltage waveform changes, represented by the crossing point of the X-axis (zero value) in the measured grid-side voltage waveform).

[0181] In step S1206 , the processor 906 is configured to calculate the second-order derivative of the measured grid-side voltage waveform to generate a second-order derivative curve, and detect a clipping point in the measured grid-side voltage waveform when the first peak of the second-order derivative curve appears (after zero crossing).

[0182] In step S1208 , the processor 906 is configured to measure the time t from the zero crossing point of the fundamental frequency to the first peak of the second-order derivative curve to determine the time t when the distorted time period Tp of the grid-side voltage waveform starts.

[0183] It will be appreciated that other methods may be used to detect the time when the time period Tp of distortion of the grid side voltage waveform begins.

[0184] Fig.13 Shown in Figure 5 The distorted grid-side voltage waveform 700 that can be measured in the grid voltage sensing circuit 580G is shown. As shown in the figure, the distorted grid-side voltage waveform 700 experiences a clipping effect due to the power being drawn by the power source 560 during the distorted time period Tp. Fig.13 Also shown is a second derivative curve 1300 that processor 906 may calculate. Fig.13 The first peak 1302 of the second-order derivative curve, the time t from the zero crossing point of the fundamental frequency to the first peak 1302 of the second-order derivative curve, and the distorted time period Tp are shown. Although the present disclosure has been described according to the specific embodiments described above, it should be understood that these embodiments are merely illustrative and the claims are not limited to these embodiments. Those skilled in the art will be able to make modifications and substitutions that are deemed to fall within the scope of the appended claims in light of the present disclosure. Each feature disclosed or shown in this specification may be incorporated into any embodiment, either alone or in any appropriate combination with any other features disclosed or shown herein.

[0185] Reference numerals list

[0186] 100 Electricity Meter

[0187] 105 Load

[0188] 110 Power cord

[0189] 115 Transformer

[0190] 120a First input terminal

[0191] 120c Second input terminal

[0192] 130 Measurement circuit

[0193] 135a First Node

[0194] 135c Second Node

[0195] 140a First output terminal

[0196] 140c Second output terminal

[0197] 145a Third Node

[0198] 145c Fourth Node

[0199] 150a First current transformer

[0200] 150c Second current transformer

[0201] 200 Electricity Meter

[0202] 205 Load

[0203] 215 Power Grid

[0204] 220a First input terminal

[0205] 220c Second input terminal

[0206] 230 Measurement circuit

[0207] 240a First output terminal

[0208] 240c Second output terminal

[0209] 260 Power Supply

[0210] 265 Actuator

[0211] 270 Analog Front End

[0212] 275 Digital Circuits

[0213] 280G Grid Voltage Sensing Circuit

[0214] 280L Load Voltage Sensing Circuit

[0215] 290a First current sensing circuit

[0216] 290c Second current sensing circuit

[0217] 295 Service Disconnect Switch

[0218] 300 Circuits

[0219] 320a First input terminal

[0220] 320c Second input

[0221] 325a First output

[0222] 325c Second output

[0223] 345a First resistor string

[0224] 345c Second resistor string

[0225] 400 Electricity Meter

[0226] 405 Load

[0227] 415 Power Grid

[0228] 420a First input terminal

[0229] 420c Second input terminal

[0230] 430 Measurement Circuit

[0231] 440a First output terminal

[0232] 440c Second output

[0233] 455 Surge Protection Device

[0234] 460 Power Supply

[0235] 465 Actuator

[0236] 470 Analog Front End

[0237] 475 Digital Circuits

[0238] 480G Grid Voltage Sensing Circuit

[0239] 480L Load Voltage Sensing Circuit

[0240] 490a First current sensing circuit

[0241] 490c Second current sensing circuit

[0242] 495 Service Disconnect Switch

[0243] 500 Circuits

[0244] 502 Surge protection element

[0245] 505a First Node

[0246] 505c Second Node

[0247] 510a First voltage divider

[0248] 510c Second voltage divider

[0249] 555 Surge Protection Device

[0250] 560 Power Supply

[0251] 590 Input

[0252] 595 Input

[0253] 660 Power Supply

[0254] 602 Surge protection element

[0255] 700 Distorted grid-side voltage waveform

[0256] 800 Grid-side voltage waveform

[0257] 902 Anti-aliasing filter

[0258] 904 Analog-to-Digital Converter

[0259] 906 processor

[0260] 910 Memory

[0261] 912 Anti-aliasing filter

[0262] 914 Analog-to-digital converter

[0263] 970 Analog Front End Circuit

[0264] 1050 Current

[0265] 1300 Second derivative curve

[0266] 1302 First Peak

Claims

1. An electric meter (400), comprising: a power supply (460, 560, 660) for supplying electrical energy to the measurement circuit (430); as well as A surge protection device (455, 555) for protecting the input of the power supply; The measurement circuit is configured to measure a voltage across the surge protection device.

2. The electric meter (400) according to any preceding claim, wherein the surge protection device (455, 555) comprises at least one of the following: Metal oxide varistors (MOVs); Gas discharge tube (GDT); Transient Voltage Suppressor (TVS) diodes; and / or Polymer Positive Temperature Coefficient Device (PPTC).

3. The electric meter (400) of claim 1 or 2, wherein the input comprises a first voltage input (VA_LINE) and a second voltage input (VC_LINE), and wherein the surge protection device (455, 555) is connected to a first node (505a) coupled to the first voltage input and a second node (505c) coupled to the second voltage input.

4. The electric meter (400) according to claim 3, wherein: In use, the first voltage input (VA_LINE) has a first phase and the second voltage input (VC_LINE) has a second phase that is out of phase with the first phase.

5. The electric meter (400) of claim 3 or 4, comprising a first voltage divider (510a) coupled to the first node (505a) and a second voltage divider (510c) coupled to the second node (505c), wherein the measurement circuit (430) is configured to measure the voltage at each of the first voltage divider and the second voltage divider to determine the voltage across the surge protection device (455, 555).

6. The electric meter (400) according to claim 5, wherein: The first voltage divider and the second voltage divider (510a, 510c) are configured to withstand a clamping voltage of a surge protection device (455, 555); as well as At least one of the first voltage divider and the second voltage divider includes: a resistor voltage divider; a capacitor voltage divider; or an inductor voltage divider.

7. The electric meter (400) of claim 3 or 4, comprising a first linear transformer coupled to the first node (505a) and a second linear transformer coupled to the second node (505c), wherein the measurement circuit (439) is configured to measure a voltage at each of the first linear transformer and the second linear transformer to determine a voltage across the surge protection device (455, 555).

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

9. The electric meter (400) of claim 8, wherein the surge protection element is a resistor.

10. The electric meter (400) according to claim 8 or 9, wherein the measurement circuit (430) comprises a processor, the processor being configured to: obtaining a sample of the measured voltage across the surge protection device; a start time of a time period for detecting distortion of the measured voltage across the surge protection device; obtaining a current value at an input terminal of the power supply during the time period; determining a voltage drop across the surge protection device during the time period using the current value; as well as Samples of the measured voltage across the surge protection device taken during the time period are modified based on the voltage drop across the surge protection device during the time period.

11. The electric meter (400) of claim 10, further comprising a current sensing device arranged to output the current value.

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

13. The electric meter (400) according to claim 10, wherein the current value is pre-stored in a memory accessible to the processor, and the processor is configured to obtain the current value by retrieving the current value from the memory.

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

15. The electric meter (400) according to claim 8 or 9, wherein the measurement circuit (430) comprises a processor, the processor being configured to: obtaining a sample of the measured voltage across the surge protection device; a start time of a time period for detecting distortion of the measured voltage across the surge protection device; determining a voltage peak value during the distorted time period using: (i) the measured voltage across the surge protection device at the start of the distorted time period, and (ii) a time between a zero crossing of the measured voltage across the surge protection device and a start time of the distorted time period of the measured voltage across the surge protection device; as well as Samples of the measured voltage across the surge protection device taken during the time period are modified based on the voltage peak.

16. The electricity meter (400) of any preceding claim, wherein the power supply (460, 560, 660) comprises at least one rectifier and / or regulator circuit configured to supply electrical energy to the measurement circuit (430).

17. An electricity meter (400) as claimed in any preceding claim, comprising an actuatable switch for selectively coupling a grid-side input of the electricity meter with a load-side output of the electricity meter.

18. The electric meter (400) according to claim 17, wherein: The measurement circuit (430) is configured to measure a load-side voltage at the load-side output of the actuatable switch (495); the measurement circuit being configured to measure a load-side current at the load-side output of the actuatable switch; as well as The voltage across the surge protection device (455, 555) corresponds to the voltage at the grid-side input of the actuatable switch.

19. The electric meter (400) of claim 18, comprising a control circuit (475) and a communication circuit, wherein the control circuit (475) is configured to selectively actuate the actuatable switch (495) based at least in part on: The voltage at the grid-side input measured by the measurement circuit (430); The load side voltage measured by the measurement circuit; and / or data received by the communications circuit.

20. A method of operating an electric meter (400), the method comprising configuring a measurement circuit (430) to measure a voltage across a surge protection device (455, 555), wherein the surge protection device is configured to protect an input of a power source (460, 560, 660) configured to supply power to the measurement circuit.

21. The method of claim 20, comprising selectively operating an actuatable switch (495) of the electric meter, wherein the actuatable switch is configured to selectively couple a grid-side input of the electric meter with a load-side output of the electric meter.

22. A method according to claim 21, wherein the selective actuation of the actuatable switch (495) is based at least in part on: the voltage at the grid-side input measured by the measurement circuit (430); the load-side voltage measured by the measurement circuit; and / or data received by the communication circuit of the meter.

23. The method of claim 21, comprising identifying a co-generation scenario based on the load-side voltage and the voltage at the grid-side input when the actuatable switch (495) is configured to decouple the grid-side input of the meter from the load-side output of the meter.

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