JP7664082B2 - Electronic power meter - Google Patents

Description

The present invention relates to an electronic watt-hour meter equipped with a switch control unit that controls the opening and closing of a switch that switches the load current on and off.

Conventionally, an example of this type of electronic watt-hour meter is the watt-hour meter disclosed in Patent Document 1.

This electricity meter includes a plurality of switches that open and close electric circuits, a current detection unit, a calculation unit, and a switch control unit. The calculation unit calculates the deterioration level of each switch based on the current detected by the current detection unit before or during driving of each switch from a closed state to an open state. The switch control unit determines which of the plurality of switches is to be driven first from a closed state to an open state based on the deterioration level of each switch, and drives the plurality of switches based on the determination result.

This electricity meter can reduce the variation in contact deterioration among multiple switches.

JP 2019-203790 A

However, with the conventional electronic electricity meters described above, although it is possible to suppress the variation in deterioration of the contacts among multiple switches, it is difficult to suppress the deterioration of the contacts themselves.

The present invention has been made to solve such problems,
A voltage measurement unit that measures a voltage supplied to a consumer;
A current measuring unit that measures a current supplied to a consumer;
an AD conversion unit that performs AD conversion on the voltage measured by the voltage measurement unit and the current measured by the current measurement unit;
A calculation unit that calculates power consumed by a consumer from the current and voltage converted by the AD conversion unit;
a voltage zero-crossing time point detection unit that detects a zero-crossing time point of a voltage supplied to a consumer from a voltage value AD-converted by the AD conversion unit;
a current zero-crossing time point detection unit that detects a zero-crossing time point of a current supplied to a consumer from a current value that is AD converted by the AD conversion unit or from an instantaneous power factor that is calculated by the active power and reactive power that are calculated by the calculation unit;
a switch control unit that controls the opening and closing of a switch that switches on and off the current supplied to the consumer by a control signal that is output to the switch;
an operation time measurement unit that measures an operation time from when a control signal is output from the switch control unit until the switch is mechanically operated based on a current value that is AD converted by the AD conversion unit;
Regardless of the type of load installed at the consumer's premises, the electronic watt-hour meter is configured to output a control signal from the switch control unit at a timing when the switch closes before the operation time measured by the operation time measurement unit is earlier than the voltage zero-cross point detected by the voltage zero-cross point detection unit, at a timing when overflow current no longer flows through the switch , and at a timing when the switch opens before the operation time measured by the operation time measurement unit is earlier than the current zero-cross point detected by the current zero-cross point detection unit, at a timing when no arc is generated in the switch, thereby suppressing deterioration of the switch contacts themselves .

According to this configuration, when the switch is closed, the control signal output timing adjustment unit causes the switch control unit to output a control signal to the switch before the operating time measured by the operating time measurement unit is greater than the zero-cross point of the voltage detected by the voltage zero-cross point detection unit. Therefore, when the switch contacts are closed, no voltage is applied to the load connected to the electronic watt-hour meter. As a result, no overflow current flows between the contacts when the switch is closed, and the switch contacts do not weld due to the overflow current.

In addition, the control signal output timing adjustment unit causes the switch control unit to output a control signal to the switch before the operating time measured by the operating time measurement unit is greater than the zero-cross point of the current detected by the current zero-cross point detection unit when the switch is opened. Therefore, when the switch is opened, the contacts are opened without current flowing between the contacts of the switch. Because the contacts do not interrupt the current when the switch is opened, the contacts are opened without generating an arc that occurs between the contacts when current is interrupted. Therefore, the switch can be operated without incurring damage to the contacts themselves due to arcing or damage to mechanical components around the contacts due to arc heat.

The present invention provides an electronic watt-hour meter that can suppress deterioration of the contacts themselves.

1 is a block diagram of an electronic watt-hour meter according to an embodiment of the present invention; 4 is a graph for explaining an operation time of a switch calculated by an operation time measurement unit from a current value AD-converted by an AD conversion unit constituting the electronic watt-hour meter shown in FIG. 1 . 1 is a block diagram of an external measuring device provided outside an electronic watt-hour meter according to an embodiment for measuring an operation time of a switch, and the electronic watt-hour meter;

Next, we will explain how to implement the electronic watt-hour meter according to the present invention.

Figure 1 is a block diagram of an electronic power meter (hereinafter referred to as smart meter) 2 according to one embodiment of the present invention, which includes a built-in switch 1 that switches the load current I on and off. In this embodiment, the smart meter 2 is illustrated as a single-phase two-wire type, but the phase wire type of the smart meter 2 is not limited to a single-phase two-wire type, and may be a single-phase three-wire type or a three-phase three-wire type, etc.

The switch 1 has contacts 1a and 1b that connect and disconnect the load current I supplied from the smart meter 2 to the consumer's load 4. The smart meter 2 has power supply terminals 1S and 2S to which an AC power supply 3 is connected, and load terminals 1L and 2L to which a load 4 such as an electric water heater is connected. The switch 1 is located inside the smart meter 2 between the power supply terminal 1S and the load terminal 1L, and the load current I flowing through the switch 1 and the load 4 is detected by the current sensor 5. The load current I detected by the current sensor 5 is input to a current measurement unit 7 in the central control circuit 6 and measured by the current measurement unit 7.

The voltage applied from the AC power source 3 to the power source terminals 1S, 2S and supplied to the consumer's load 4 is input to the voltage measurement unit 10 in the central control circuit 6 via the protection circuit 8 and the step-down circuit 9. The protection circuit 8 protects the central control circuit 6 from surge voltages and the like, and the step-down circuit 9 steps down the AC voltage output from the AC power source 3 to a level suitable for voltage measurement in the voltage measurement unit 10. The voltage measurement unit 10 measures the voltage supplied to the consumer's load 4 from this stepped-down voltage.

In the central control circuit 6, the voltage measured by the voltage measuring unit 10 and the current measured by the current measuring unit 7 are AD converted by the AD conversion unit 11, converting the analog signals into digital signals. The calculation unit 12 calculates the power consumed by the consumer's load 4 from the digital values of the current and voltage AD converted by the AD conversion unit 11. In this embodiment, the calculation unit 12 calculates the active power, reactive power, etc., and displays them on a display unit (not shown).

The opening and closing of the switch 1 is controlled by a control signal s output to the switch 1 by the switch control circuit 13 constituting the switch control unit. The operation time measurement unit 14 in the central control circuit 6 measures the operation time from when the control signal s is output from the switch control circuit 13 until the switch 1 mechanically operates, from the current value AD converted by the AD conversion unit 11. Specifically, the operation time measurement unit 14 measures the operation time T1 from when the control signal s is output from the switch control circuit 13 until the opening and closing mechanism that opens and closes the contacts 1a and 1b of the switch 1 completes its operation and the contacts 1a and 1b are mechanically closed, and the operation time T2 until opening, from the current value AD converted by the AD conversion unit 11.

2(a) and (b) show the current waveform of the load current I obtained by plotting the current value converted by the AD converter 11. The horizontal axis of the graphs represents the passage of time t in digital values (not shown), and the vertical axis represents the magnitude of the current value I in digital values (not shown). The graph shown in FIG. 2(a) shows the change in the current waveform of the load current I when the switch 1 transitions from an open state in which the contacts 1a and 1b of the switch 1 are open to a closed state in which the contacts 1a and 1b of the switch 1 are closed. The graph shown in FIG. 2(b) shows the change in the current waveform of the load current I when the switch 1 transitions from a closed state to an open state.

In addition, time t0 in each graph indicates the timing when control signal s is output from the switch control circuit 13, and time t1 in the graph in FIG. 1(a) indicates the timing when contacts 1a, 1b are mechanically closed and current begins to flow through the switch 1. Therefore, the period T1 from time t0 to t1 in the graph in FIG. 1(a) represents the operating time T1 from when control signal s is output from the switch control circuit 13 to the switch 1 to when contacts 1a, 1b of the switch 1 are mechanically closed.

In addition, time t2 in the graph in FIG. 2(b) indicates the timing when contacts 1a and 1b mechanically open and the current flowing through switch 1 is interrupted. Therefore, the period T2 from time t0 to t2 in the graph in FIG. 2(b) represents the operating time T2 from when control signal s is output from switch control circuit 13 to switch 1 until contacts 1a and 1b of switch 1 mechanically open.

The central control circuit 6 has a memory unit 16 that stores information, and the operation times T1 and T2 measured by the operation time measurement unit 14 are stored in the memory unit 16 by the operation time measurement unit 14. During operation of the smart meter 2, the operation time measurement unit 14 monitors the phase state and frequency of the load current I and the load voltage, and automatically measures the operation times T1 and T2 each time the switch control circuit 13 controls the opening and closing of the switch 1, and stores the new operation times T1 and T2 obtained each time they are measured in the memory unit 16. When the smart meter 2 is manufactured, the switch 1 is opened and closed with the load current I flowing through the smart meter 2, and the operation times T1 and T2 are automatically measured by the operation time measurement unit 14 and stored in the memory unit 16.

In this embodiment, the timing t0 at which the control signal s is output from the switch control circuit 13 is adjusted by the control signal output timing adjustment unit 15. When the switch 1 is closed, the control signal output timing adjustment unit 15 causes the switch control circuit 13 to output the control signal s to the switch 1 before the operation time T1 stored in the memory unit 16 and the zero cross point of the voltage detected by the voltage zero cross point detection unit 17. When the switch 1 is opened, the control signal s is output from the switch control circuit 13 to the switch 1 before the operation time T2 stored in the memory unit 16 and the zero cross point of the current detected by the current zero cross point detection unit 18.

The voltage zero-cross time detection unit 17 detects the zero-cross time of the voltage supplied to the consumer's load 4 from the voltage value AD-converted by the AD conversion unit 11. The current zero-cross time detection unit 18 detects the zero-cross time of the load current I supplied to the consumer's load 4 from the current value AD-converted by the AD conversion unit 11. Alternatively, the delay of the current phase with respect to the voltage phase is calculated from the instantaneous power factor calculated by the active power and reactive power calculated by the calculation unit 12, and the zero-cross time of the load current I supplied to the consumer's load 4 is detected from this delay. If the smart meter 2 is a three-phase three-wire system, the zero-cross time of the voltage and current is detected for each phase, and the above-mentioned operation times T1 and T2 are measured for each phase and stored in the memory unit 16. At this time, when the delay of the current phase is viewed from the instantaneous power factor, the delay of the current phase with respect to the voltage phase is calculated for each phase from the instantaneous power factor calculated by the active power and reactive power for each phase calculated by the calculation unit 12.

According to the smart meter 2 of this embodiment, as described above, when the switch 1 is closed, the control signal output timing adjustment unit 15 causes the switch control circuit 13 to output the control signal s to the switch 1 before the operation time T1 stored in the memory unit 16 from the zero-cross point of the voltage detected by the voltage zero-cross point detection unit 17. When the smart meter 2 is a three-phase three-wire system, this control signal s is output for each phase to the switch 1 provided for each phase. Therefore, when the contacts 1a and 1b of the switch 1 are closed, no voltage is applied to the load 4 connected to the smart meter 2. Therefore, when the switch 1 is closed, no overflow current flows between the contacts 1a and 1b, and the contacts 1a and 1b of the switch 1 do not weld due to the overflow current.

In addition, the control signal output timing adjustment unit 15 causes the switch control circuit 13 to output the control signal s to the switch 1 at the time of opening the switch 1, before the zero cross point of the current detected by the current zero cross point detection unit 18 and the operation time T2 stored in the memory unit. In this case, if the smart meter 2 is a three-phase three-wire type, the control signal s is output for each phase to the switch 1 provided for each phase. Therefore, when the switch 1 is opened, the contacts 1a and 1b are opened without current flowing between them. Therefore, since the contacts 1a and 1b do not interrupt the current when opened, the switch 1 opens the contacts 1a and 1b without generating an arc that occurs between the contacts 1a and 1b when the current is interrupted. Therefore, the switch 1 can be operated without causing damage to the contacts 1a and 1b themselves due to the arc and damage to the mechanical parts around the contacts 1a and 1b due to the arc heat.

As a result, it is possible to provide a smart meter 2 that can control the opening and closing of the switch 1 without causing deterioration of the contacts 1a and 1b themselves.

In addition, in the smart meter 2 of this embodiment, as described above, the operation time measurement unit 14 measures the operation times T1, T2 each time the switch control circuit 13 controls the opening and closing of the switch 1, and stores the new operation times T1, T2 obtained each time the measurement is performed in the memory unit 16. The control signal output timing adjustment unit 15 causes the switch control circuit 13 to output a control signal s based on the new operation times T1, T2 stored in the memory unit 16.

The operating times T1, T2 of the switch 1 stored in the memory unit 16 are therefore updated to the latest ones in accordance with the changes over time of the switch 1 due to continued use of the smart meter 2 and the effects on the switch 1 of changes in the external environment, such as the ambient temperature of the smart meter 2. For this reason, the output timing of the control signal s to the switch control circuit 13 is always adjusted optimally by the control signal output timing adjustment unit 15 in accordance with the time of operation of the smart meter 2 and the external environment in which the smart meter 2 is placed. For this reason, the opening and closing of the contacts 1a, 1b of the switch 1 is always performed at optimal timing, effectively suppressing deterioration of the contacts 1a, 1b themselves.

In the above embodiment, the case where the operating time of the switch 1 is measured inside the smart meter 2 has been described. However, before the smart meter 2 is shipped from the factory, an external operating time measuring device 20 as manufacturing equipment shown in the block diagram of FIG. 3 may be connected to the smart meter 2 so that the operating time of the switch 1 can be measured outside the smart meter 2 as well. In FIG. 3, parts that are the same as or equivalent to those in FIG. 1 are given the same reference numerals and their description will be omitted.

In this case, the external measuring device 20 also includes a current measuring unit 7', a voltage measuring unit 10', an AD conversion unit 11', a calculation unit 12', an operation time measuring unit 14', a voltage zero crossing time detection unit 17', and a current zero crossing time detection unit 18' similar to those built into the smart meter 2. The voltage measuring unit 10' is supplied with the voltage supplied to the load 4 by the step-down circuit 9' after being stepped down, and the current measuring unit 7' is supplied with the current detected by the current sensor 5 in the smart meter 2. A control signal s output by the switch control circuit 13 of the smart meter 2 is then supplied to the operation time measuring unit 14', and the operation times T1 and T2 of the switch measured by the operation time measuring unit 14' are stored in the memory unit 16 of the smart meter 2 in the same manner as in the smart meter 2. By including the voltage zero crossing time detection unit 17' and the current zero crossing time detection unit 18', the voltage waveform and current waveform of the load 4 can be confirmed by the calculation of the calculation unit 12'.

By providing such an external operating time measuring device 20 as manufacturing equipment, the current measuring unit 7', voltage measuring unit 10', AD conversion unit 11', calculation unit 12', operating time measuring unit 14', voltage zero cross point detection unit 17', and current zero cross point detection unit 18' that constitute the external operating time measuring device 20 can be made highly accurate, and the operating time measuring unit 14' can measure the operating time of the switch 1 in detail with high accuracy. Therefore, based on the highly accurate operating times T1 and T2 stored in the memory unit 16, the control signal output timing adjustment unit 15 can output the control signal s from the switch control circuit 13 at a more accurate timing.

In addition, the smart meter 2 according to the above embodiment has been described as having a built-in switch 1, but the switch 1 may be provided outside the smart meter 2. Even when the switch 1 is provided outside the smart meter 2 in this manner, the same effects as those of the above embodiment are achieved, and deterioration of the contacts 1a and 1b of the switch 1 themselves can be suppressed regardless of the installation location where the switch 1 is provided.

In addition, the operation time measurement unit 14, the control signal output timing adjustment unit 15, the voltage zero cross time detection unit 17, and the current zero cross time detection unit 18, which constitute the control device of the switch 1, can be configured either by software control processing using a computer program or by hardware configuration of an electronic circuit.

1...switch 1a, 1b...contacts 2...electronic watt-hour meter (smart meter)
3 AC power supply 4 Load 5 Current sensor 6 Central control circuit 7 Current measurement section 10 Voltage measurement section 11 AD conversion section 12 Calculation section 13 Switch control circuit (switch control section)
14: Operation time measurement section 15: Control signal output timing adjustment section 16: Storage section 17: Voltage zero cross point detection section 18: Current zero cross point detection section 20: External operation time measurement device

Claims (1)

A voltage measurement unit that measures a voltage supplied to a consumer;
A current measuring unit that measures a current supplied to a consumer;
an AD conversion unit that performs AD conversion on the voltage measured by the voltage measurement unit and the current measured by the current measurement unit;
A calculation unit that calculates power consumed by a consumer from the current and voltage converted by the AD conversion unit;
a voltage zero-cross time point detection unit that detects a zero-cross time point of a voltage supplied to a consumer from a voltage value AD converted by the AD conversion unit;
a current zero-crossing time point detection unit that detects a zero-crossing time point of a current supplied to a consumer from a current value that is AD converted by the AD conversion unit or from an instantaneous power factor that is calculated by the active power and reactive power that are calculated by the calculation unit;
a switch control unit that controls the opening and closing of a switch that switches on and off the current supplied to the consumer by a control signal output to the switch;
an operation time measurement unit that measures an operation time from when the control signal is output from the switch control unit until the switch is mechanically operated based on a current value that is AD converted by the AD conversion unit;
and a control signal output timing adjustment unit that causes the switch control unit to output the control signal at a timing when the switch is closed and before the operation time measured by the operation time measurement unit is before the zero cross point of the voltage detected by the voltage zero cross point detection unit, at a timing when an overflow current no longer flows through the switch , and when the switch is opened and before the operation time measured by the operation time measurement unit is before the zero cross point of the current detected by the current zero cross point detection unit, at a timing when an arc is no longer generated in the switch , regardless of the type of load installed in the consumer's premises, thereby suppressing deterioration of the contacts of the switch themselves .

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