JP2022175390A - Watt-hour meter circuit breaker contact point state detection method and watt-hour meter circuit breaker drive circuit - Google Patents

Abstract

To provide a watt-hour meter contact point state detection method and a watt-hour meter circuit breaker drive circuit, capable of grasping the accurate number of times of opening/closing operation by detecting a state of a contact point of a circuit breaker.SOLUTION: A watt-hour meter circuit breaker drive circuit for performing supply/interception of power of a power system to loads 1L, 2L by a movable contact point 15b performing opening operation and closing operation to a fixed contact point 15a by supply or interception of a current to an exciting coil 11 comprises: a current sensor 4 that in the case of the movable contact point 15b shifting from the opening operation to the closing operation, acquires a first current waveform of the exciting coil 11 when the movable contact point 15b is changed over by a first drive signal and in the case of the movable contact point 15b performing the closing operation, acquires a second current waveform of the exciting coil 11 by a second drive signal; and a CPU 2 that on the basis of a difference between the first current waveform and the second current waveform detected by the current sensor 4, detects whether the closing operation of the movable contact point is performed.SELECTED DRAWING: Figure 2

Description

The present invention relates to a switch contact state detection method for a power meter and a switch drive circuit for the power meter.

As a conventional technique, for example, a method for detecting an abnormality in an electromagnetic relay is known, which is disclosed in Patent Document 1. A method for detecting an abnormality in an electromagnetic relay is such that a movable contact and a fixed contact are closed or opened by an electromagnetic force generated by supplying or interrupting current to an exciting coil.

A first transient response signal of the coil current of the excitation coil when the first detection pulse signal is supplied while the movable contact is not operating relative to the stationary contact, and the movable contact is operating relative to the stationary contact. state, based on at least one of the second transient response signal of the coil current when the second detection pulse signal is supplied, and the abnormal operation of the movable contact with respect to the fixed contact is detected.

A switch used in a watt-hour meter is provided between a power source and a load, and cuts off the supply of electric power to the load in a power system by opening and closing a movable contact. The movable contact repeatedly opens and closes many times with respect to the fixed contact.

Japanese Patent No. 5660236

However, the switch deteriorates as opening and closing operations increase. Therefore, it is necessary to keep track of the number of opening and closing operations. Software counts the number of open/close instructions, but the actual number of operations may differ from the number of open/close instructions. For this reason, it is desirable to detect the state of the contact of the switch in response to the opening/closing instruction and to accurately grasp the number of opening/closing operations.

SUMMARY OF THE INVENTION An object of the present invention is to provide a contact state detection method and a switch driving circuit for a switch of a watt-hour meter, which can detect the state of the contact of the switch and accurately grasp the number of switching operations.

In order to solve the above-mentioned problems, according to claim 1 of the present invention, the power load of the electric power system is transferred to the load of the electric power system by opening and closing the movable contact with respect to the fixed contact by supplying or cutting off the current to the exciting coil. A method for detecting a contact state of a switch of a power meter that cuts off the supply of electricity, wherein the movable contact is switched from the opening operation to the closing operation by the first drive signal. A first current waveform is acquired, and when the movable contact is closed, a second current waveform of the exciting coil is acquired by a second drive signal, and based on the difference between the first current waveform and the second current waveform. It is characterized by detecting whether or not the movable contact has been closed.

According to claim 2, a switch for a watt-hour meter that cuts off the supply of electric power to a load of an electric power system by opening and closing a movable contact with respect to a fixed contact by supplying or cutting off a current to an exciting coil. In the contact state detection method, when the movable contact is closed, a first current waveform of the excitation coil is obtained by a first drive signal, and when the movable contact is closed, a second drive signal is obtained. A second current waveform of the exciting coil is obtained, and whether or not the moving contact has been closed is detected based on a difference between the first current waveform and the second current waveform.

According to a third aspect of the present invention, there is provided a switch for a watt-hour meter that cuts off the supply of electric power to a load of an electric power system by opening and closing a movable contact with respect to a fixed contact by supplying or cutting off a current to an exciting coil. In the contact state detection method, a first current waveform of the exciting coil is acquired when the movable contact is switched by a first driving signal when the movable contact is in an opening operation from a closing operation, and the movable contact is opened. During operation, a second current waveform of the excitation coil is acquired by the second drive signal, and whether or not the movable contact has been opened is determined based on the difference between the first current waveform and the second current waveform. It is characterized by detecting.

According to a fourth aspect of the present invention, there is provided a switch for a watt-hour meter that cuts off the supply of electric power to a load of an electric power system by opening and closing the movable contact with respect to the fixed contact by supplying or cutting off the current to the excitation coil. In the contact state detection method, when the movable contact is in an opening operation, a first current waveform of the exciting coil is obtained when the movable contact is switched by a first driving signal, and when the movable contact is in the opening operation. obtaining a second current waveform of the excitation coil by a second drive signal, and detecting whether or not the movable contact has been opened based on the difference between the first current waveform and the second current waveform; characterized by

In claim 5, it is determined whether or not the amplitude value of at least one of the first current waveform and the second current waveform exceeds a predetermined value, and the amplitude value of the current waveform exceeds the predetermined value. If the state continues for a predetermined time, it is determined to be abnormal.

According to a sixth aspect of the present invention, when the current value of the first current waveform and the current value of the second current waveform are below a threshold value, it is determined that the movable contact cannot be opened or closed. do.

According to a seventh aspect of the present invention, there is provided a switch drive for a watt-hour meter that cuts off the supply of electric power to a load of an electric power system by opening and closing the movable contact with respect to the fixed contact by supplying or cutting off the current to the excitation coil. A circuit for acquiring a first current waveform of the excitation coil when the movable contact is switched by a first drive signal when the movable contact is in the closing operation from the opening operation, and when the movable contact is in the closing operation a current sensor for acquiring a second current waveform of the excitation coil by a second drive signal, and determining whether or not the movable contact has been closed based on the difference between the first current waveform and the second current waveform; and an opening/closing operation detection unit for detecting.

According to claim 1, the difference between the first current waveform due to the first drive signal when the movable contact moves from opening to closing and the second current waveform due to the second drive signal when the moving contact closes is Based on this, it is detected whether or not the movable contact has been closed. That is, by detecting the state of the contact of the switch, the number of switching operations can be accurately grasped.

According to claim 2, the movable contact is based on the difference between the first current waveform due to the first drive signal when the movable contact is closed and the second current waveform due to the second drive signal when the movable contact is closed. Detects whether the closing action of is performed. That is, by detecting the state of the contact of the switch, the number of switching operations can be accurately grasped.

According to claim 3, the difference between the first current waveform due to the first driving signal when the movable contact is operated from closing to opening and the second current waveform due to the second driving signal when the movable contact is opened is Based on this, it is detected whether or not the movable contact has been opened. That is, by detecting the state of the contact of the switch, the number of switching operations can be accurately grasped.

According to claim 4, the movable contact is based on the difference between the first current waveform due to the first drive signal when the movable contact is opened and the second current waveform due to the second drive signal when the movable contact is opened. Detects whether an opening operation has been performed. That is, by detecting the state of the contact of the switch, the number of switching operations can be accurately grasped.

According to claim 5, when the state in which the amplitude value of the current waveform exceeds a predetermined value continues for a predetermined time, it can be determined that the switch is abnormal.

According to claim 6, when the current value of the first current waveform and the current value of the second current waveform are below the threshold, it can be determined that the movable contact cannot be opened or closed.

According to claim 7, the same effect as the effect of claim 1 can be obtained.

It is a figure which shows the switch of the watt-hour meter which concerns on the 1st Embodiment of this invention. It is a figure which shows the switch drive circuit of the watt-hour meter which concerns on the 1st Embodiment of this invention. 4 is a flow chart showing state detection/abnormality detection of the contact of the switch of the watt-hour meter according to the first embodiment of the present invention. FIG. 4 is a diagram showing a current waveform when switching from opening operation to closing operation of the switch of the watt-hour meter according to the first embodiment of the present invention and a current waveform in a stable state during the closing operation; 2 is a diagram showing a current waveform in a closing operation of the switch of the watt-hour meter according to the first embodiment and a current waveform in a stable state during the closing operation; FIG. 4 is a flowchart illustrating detection of a closing operation of a switch of the watt-hour meter according to the first embodiment of the present invention; FIG. 4 is a diagram showing a current waveform when switching from a closing operation to an opening operation of the switch of the watt-hour meter according to the first embodiment of the present invention and a current waveform in a stable state during the opening operation; FIG. 4 is a diagram showing a current waveform when the switch of the watt-hour meter according to the first embodiment of the present invention switches from an opening operation to an opening operation and a current waveform in a stable state after the operation; 4 is a flowchart illustrating detection of a closing operation of a switch of the watt-hour meter according to the first embodiment of the present invention; FIG. 7 is a diagram showing a current waveform when the switch of the watt-hour meter according to the second embodiment of the present invention is abnormal. 9 is a flow chart of abnormality detection of a switch of a watt-hour meter according to a second embodiment of the present invention; FIG. 10 is a diagram showing current waveforms from closing operation to opening operation during contact welding of the switch of the watt-hour meter according to the third embodiment of the present invention;

DESCRIPTION OF THE PREFERRED EMBODIMENTS A contact state detection method for a switch of a watt-hour meter and a switch according to an embodiment of the present invention will be described below in detail with reference to the drawings.
(First embodiment)
FIG. 1 shows a configuration diagram of a switch of a power meter according to the first embodiment. The watt-hour meter detects the system voltage and current of the power system, and calculates power based on the detected voltage and current. The watt-hour meter includes a switch 1 as shown in FIG.

As shown in FIG. 2, the switch 1 consists of a latching relay and is provided between the power supply side 1S and the load 1L. cut off the supply of

The switch 1, as shown in FIG. The contact 15 consists of a fixed contact 15a and a movable contact 15b.

An excitation coil 11 is wound around a U-shaped iron core 12 , and a permanent magnet 13 is inserted through a gap portion of the iron core 12 . The S pole of the permanent magnet 13 and the contact 15 are connected by a connecting portion 14 . The contact 15 consists of a fixed contact 15 a and a movable contact 15 b connected by a connecting portion 14 .

When an exciting current is passed through the exciting coil 11 in one direction, an electromagnetic force is generated, and the electromagnetic force generates an N pole on one side of the gap of the iron core 12 and an S pole on the other side of the gap. Therefore, the N pole of the permanent magnet 13 is attracted to the S pole of the gap portion, and the S pole of the permanent magnet 13 is attracted to the N pole of the gap portion. Therefore, the movable contact 15b is closed with respect to the fixed contact 15a.

On the other hand, when an exciting current is passed through the exciting coil 11 in the direction opposite to the one direction, an S pole is generated in one gap portion of the core 12 and an N pole is generated in the other gap portion. Therefore, the N pole of the permanent magnet 13 is separated from the N pole of the gap portion, and the S pole of the permanent magnet 13 is separated from the S pole of the gap portion. Therefore, the movable contact 15b opens with respect to the fixed contact 15a.

FIG. 2 is a diagram showing a switch drive circuit of the watt hour meter according to the first embodiment of the present invention. The switch driving circuit drives the switch 1 and includes the switch 1, a CPU 2, a triac 3, and current sensors 4 and 5. The CPU 2 successively outputs the drive signal to the triac 3 twice to cause the excitation coil 11 to flow an excitation current, thereby switching the contact 15 .

A series circuit of a triac 3, an exciting coil 11, and a current sensor 4 is connected between the power supply side 1S and the power supply side 2S. The current sensor 4 detects the current flowing through the exciting coil 11 and outputs the detected current to the CPU 2 as a transient response signal. The CPU 2 AD (analog-digital) converts the two current waveforms from the current sensor 4 and compares the two digital signals, thereby determining the switching operation state of the movable contact 15b with respect to the fixed contact 15a of the contact 15 by software. .

The current sensor 5 is connected in series with the switch 1 between the power supply side 1S and the load 1L. The current sensor 5 detects current flowing from the power supply side 1S to the load 1L while the contact is closing. As the current sensors 4 and 5, there are magnetic sensors, current transformers (ct), and the like. Moreover, as the current sensor 4, a chip resistor (shunt resistor) that can be mounted on a substrate is preferable from the viewpoint of cost and manufacturability.
(Basic principle of contact state detection method for switch of electric energy meter)
The method for detecting the contact state of the switch 1 of the watt-hour meter detects the opening or closing state of the contact 15 of the switch 1 from the waveform of the current flowing through the excitation coil 11 that changes according to the state of the contact 15 of the switch 1 . When the open state (closed state) of the contact 15 is switched to the closed state (open state), the polarity of the electromagnet composed of the exciting coil 11 and the iron core 12 is reversed to generate a back electromotive force due to self induction. Therefore, the current flowing through the exciting coil 11 is reduced compared to when the contact 15 is stable.

In order to utilize this principle, the state of the contact 15 is discriminated by software by inputting the drive signal twice in succession, AD-converting the respective current waveforms, and comparing them. This detection method can absorb the effects of individual differences in the excitation coil 11 and changes due to temperature. This example will be described using a current waveform during AC (alternating current) driving. The state of the contact 15 can be similarly detected in the case of DC (direct current) drive. Furthermore, since it is easy to control the pulse width of the exciting current in the case of DC driving, the state of the contact 15 can be detected by applying a drive signal that does not operate the contact 15 .
(software processing)
FIG. 3 is a flowchart showing state detection/abnormality detection of the contact 15 of the switch of the watt-hour meter according to the first embodiment. The switch drive circuit of the watt-hour meter shown in FIG. 2 executes state detection/abnormality detection processing of the contact 15 during opening/closing operation of the contact 15 or periodically.

First, when the CPU 2 applies the drive signal to the triac 3 two times in succession, the excitation current flows through the excitation coil 11 two times in succession. The current sensor 4 measures two successive currents flowing through the exciting coil 11 (step S11).

Next, the CPU 2 AD-converts the two current waveforms from the current sensor 4 and compares the two digital signals to determine the contact state, that is, the contact closing or opening operation by software (step S12). . The determination process includes a method of comparing a current value with a threshold at a certain time, a method of comparing an integral value of a certain interval, and a similarity of current waveforms. The CPU 2 configures an opening/closing operation detection unit that detects the opening operation or closing operation of the contact.

If there is no abnormality in the state of the contact 15 (step S13), the CPU 2 stores the state of the opening or closing operation of the contact 15 in the memory (step S14). Then, the CPU 2 updates the threshold used for determining the contact state (step S15).

By periodically updating the threshold, it is possible to absorb the effects of aging and the installation environment. Also, when making a judgment using the above detection method, by comparing the contact state recorded in the memory at the time of initialization of the watt hour meter or at the time of the previous operation, it is confirmed whether there is a mismatch with the memory information. can be done.

On the other hand, in step S13, if the state of the contact 15 is abnormal, the CPU 2 notifies the abnormal state (step S16).
(Contact state detection method)
Next, a method for detecting the contact state of the switch of the watt hour meter will be described. In the method of detecting the contact state of the switch of the watt hour meter, the supply or interruption of current to the exciting coil 11 causes the movable contact 15b to open and close with respect to the fixed contact 15a, thereby detecting the power supply to the load of the electric power system. Cut off the supply.
(Detection of contact closing operation)
First, the closing operation of the contact 15 will be described with reference to FIGS. 4 to 6. FIG. When the movable contact 15b changes from the opening operation to the closing operation, the CPU 2 applies the first drive signal to the exciting coil 11 via the triac 3. FIG.

The current sensor 4 acquires a first current waveform of the exciting coil 11 when the movable contact 15b is switched from the opening operation to the closing operation by the first drive signal. When the movable contact 15b is closed, the current sensor 4 acquires the second current waveform of the excitation coil 11 by the second drive signal. As shown in FIG. 4, the CPU 2 closes the movable contact 15b because the difference between the amplitude value of the first current waveform and the amplitude value of the second current waveform from the current sensor 4 is equal to or greater than a predetermined value. I judge that. That is, by detecting the state of the contact of the switch, the number of switching operations can be accurately grasped.

Also, the case where the movable contact 15b is already closed will be described with reference to the flow chart of FIG. The CPU 2 sends the first wave of the closing control signal to the excitation coil 11 via the triac 3 (step S21).

The current sensor 4 starts measuring the current (transient response signal) flowing through the exciting coil 11 (step S22). The switch starts the closing operation of the contact 15 (step S23).

Next, the CPU 2 sends out the second wave of the close control signal to the excitation coil 11 via the triac 3 (step S24).

The switch starts the closing operation of the contact 15 (step S25), and then finishes measuring the current flowing through the exciting coil 11 (step S26). Then, the CPU 2 determines that there is no difference between the amplitude value of the first current waveform and the amplitude value of the second current waveform from the current sensor 4 in the same stable state as shown in FIG. 5 (step S27). ). As a result, it can be seen that the movable contact 15b of the contact 15 is closing. That is, by detecting the state of the contact of the switch, the number of switching operations can be accurately grasped.
(Detection of contact opening operation)
Next, the opening operation of the contact 15 will be described with reference to FIGS. 7 to 9. FIG. When the movable contact 15b changes from the closing operation to the opening operation, the CPU 2 applies the first drive signal to the exciting coil 11 via the triac 3. FIG.

The current sensor 4 acquires the first current waveform of the exciting coil 11 when the movable contact 15b switches from the closed operation to the open operation by the first drive signal. When the movable contact 15b is opened, the current sensor 4 acquires the second current waveform of the excitation coil 11 by the second drive signal. As shown in FIG. 7, the CPU 2 opens the movable contact 15b because the difference between the amplitude value of the first current waveform and the amplitude value of the second current waveform from the current sensor 4 is equal to or greater than a predetermined value. I judge that. That is, by detecting the state of the contact of the switch, the number of switching operations can be accurately grasped.

Also, the case where the movable contact 15b is already open will be described with reference to the flow chart of FIG. The CPU 2 sends the first wave of the open control signal to the excitation coil 11 via the triac 3 (step S31).

The current sensor 4 starts measuring the current (transient response signal) flowing through the exciting coil 11 (step S32). The switch starts opening the contact 15 (step S33).

Next, the CPU 2 sends out the second wave of the open control signal to the exciting coil 11 via the triac 3 (step S34).

The switch starts opening the contact 15 (step S35), and then finishes measuring the current flowing through the exciting coil 11 (step S36). Then, the CPU 2 determines that the amplitude value of the first current waveform from the current sensor 4 and the amplitude value of the second current waveform from the current sensor 4 are not different from each other in the same stable state as shown in FIG. 8 (step S37). ). As a result, it can be seen that the movable contact 15b of the contact 15 is being opened. That is, by detecting the state of the contact of the switch, the number of switching operations can be accurately grasped.
(Second embodiment)
The switch of the watt-hour meter according to the second embodiment of the present invention determines that there is an abnormality when current continues to flow to the CPU 2 .

FIG. 10 is a diagram showing a current waveform when the switch of the watt-hour meter according to the second embodiment of the present invention is abnormal. The abnormality detection of the switch will be described with reference to the flow chart of FIG. 11 .

First, the CPU 2 sends a drive signal to the exciting coil 11 via the triac 3 . The current sensor 4 measures the current flowing through the exciting coil 11 (step s41). The CPU 2 determines whether the amplitude value of the current waveform from the current sensor 4 has exceeded a predetermined value (step S42).

The CPU 2 determines that the current waveform is abnormal when the amplitude value of the current waveform exceeds a predetermined value for a predetermined period of time, as in the current waveform shown in FIG. 10 (step S43). Furthermore, the CPU 2 cancels the abnormal state (step S44).
(Third embodiment)
If the contacts cannot be opened due to contact welding, etc., or if the contacts cannot be closed due to mechanical problems, the first drive signal does not change the contact state. Therefore, when the drive signal is applied to the exciting coil 11 two times in succession, a waveform is obtained when the current decreases.

At this time, there is no difference between the two current waveforms, but as shown in FIG. 12, both current values are lower than the current values shown in FIGS. 7 and 8 (both are different from the stable state). . Therefore, the CPU 2 can determine that the contact 15 cannot be opened or closed when the current value is below the threshold value. In this case, too, the polarity is simply reversed, so it can be determined whether the contact 15 is open or closed.

Further, there is a case where the contact 15 cannot be closed due to the disconnection of the connecting portion 14 for interlocking with the rotation of the permanent magnet 13 for some reason. Since the current waveform of the excitation coil 11 does not change from the current waveform during normal operation, abnormality detection cannot be performed.

However, in this situation, the conductors leading to the contacts 15 are normally under stress and in a neutral state if unsupported. If a switch whose neutral state is "closed" is adopted, the watt-hour meter detects the current between 1S and 1L shown in FIG.

Therefore, the abnormality can be detected by the current sensor 5 from the fact that the current flows between 1S and 1L after the open command. If the neutral state is "open", it cannot be determined, but it is possible to know the suspicion of abnormality from the opposite way of thinking.

1 switch 2 CPU
3 Triacs 4, 5 Current sensor 11 Exciting coil 12 Iron core 13 Permanent magnet 14 Connecting part 15 Contact 15a Fixed contact 15b Movable contact

Claims (7)

A contact state detection method for a switch of a power meter that cuts off the supply of electric power to a load of an electric power system by opening and closing the movable contact with respect to the fixed contact by supplying or cutting off the current to the exciting coil. There is
Acquiring a first current waveform of the exciting coil when the movable contact is switched by a first drive signal when the movable contact is in an opening operation to a closing operation;
Acquiring a second current waveform of the excitation coil by a second drive signal when the movable contact is in a closing operation;
A contact state detection method for a switch of a watt hour meter, comprising detecting whether or not the movable contact has been closed based on a difference between the first current waveform and the second current waveform. A contact state detection method for a switch of a power meter that cuts off the supply of electric power to a load of an electric power system by opening and closing the movable contact with respect to the fixed contact by supplying or cutting off the current to the exciting coil. There is
Acquiring a first current waveform of the excitation coil by a first drive signal when the movable contact is in a closing operation;
Acquiring a second current waveform of the excitation coil by a second drive signal when the movable contact is in a closing operation;
A contact state detection method for a switch of a watt hour meter, comprising detecting whether or not the movable contact has been closed based on a difference between the first current waveform and the second current waveform. A contact state detection method for a switch of a power meter that cuts off the supply of electric power to a load of an electric power system by opening and closing the movable contact with respect to the fixed contact by supplying or cutting off the current to the exciting coil. There is
Acquiring a first current waveform of the exciting coil when the movable contact is switched by a first drive signal when the movable contact is switched from a closing operation to an opening operation;
Acquiring a second current waveform of the excitation coil by a second drive signal when the movable contact is in an opening operation,
A contact state detection method for a switch of a watt-hour meter, comprising detecting whether or not the movable contact has been opened based on a difference between the first current waveform and the second current waveform. A contact state detection method for a switch of a power meter that cuts off the supply of electric power to a load of an electric power system by opening and closing the movable contact with respect to the fixed contact by supplying or cutting off the current to the exciting coil. There is
acquiring a first current waveform of the exciting coil when the movable contact is switched by a first drive signal when the movable contact is in an opening operation;
Acquiring a second current waveform of the excitation coil by a second drive signal when the movable contact is in an opening operation,
A contact state detection method for a switch of a watt-hour meter, comprising detecting whether or not the movable contact has been opened based on a difference between the first current waveform and the second current waveform. Determining whether or not the amplitude value of at least one of the first current waveform and the second current waveform exceeds a predetermined value, and the state in which the amplitude value of the current waveform exceeds the predetermined value continues for a predetermined time. 5. The method of detecting a contact state of a switch for a watt hour meter according to claim 1, wherein if it is, it is determined that there is an abnormality. 1. When the current value of the first current waveform and the current value of the second current waveform are below a threshold value, it is determined that the movable contact cannot be opened or closed. 5. The method for detecting a contact state of a switch of a power meter according to any one of claims 4 to 5. A switch drive circuit for a watt-hour meter that cuts off the supply of electric power to a load of an electric power system by opening and closing the movable contact with respect to the fixed contact by supplying or cutting off the current to the exciting coil,
Obtaining a first current waveform of the excitation coil when the movable contact is switched by a first driving signal when the movable contact is in the opening operation to the closing operation, and obtaining a second current waveform when the movable contact is in the closing operation. a current sensor that acquires a second current waveform of the excitation coil by a signal;
A switch drive circuit for a watt-hour meter, comprising: a switch drive circuit for a watt-hour meter, comprising: a switch drive detector for detecting whether or not the movable contact has been closed based on a difference between the first current waveform and the second current waveform. .

Images