KR100849480B1 - Apparatus and method for detecting the current transformer's coil disconnection of electronic electricity meters - Google Patents

Abstract

An apparatus and a method for detecting coil disconnection of a current transformer of an electronic electricity meter are provided to exactly meter used power in a three-phase electricity meter by detecting disconnection of secondary coils of one or a plurality of three phases. An apparatus for detecting coil disconnection of an electronic electricity meter includes a disconnection detection device(700), a control device, and a relay unit(500). The disconnection detection device detects and outputs disconnection of a secondary coil through a voltage signal of a current transformer(400) according to a control signal. The control device outputs the control signal to the disconnection detection device according to a detection period of the voltage signal and displays to a user whether the disconnection generates according to the disconnection detection result of the disconnection detection device. The relay unit outputs the voltage signal to a switching path according to the control signal.

Description

Apparatus and method for detecting the current transformer's Coil disconnection of electronic electricity meters}

The present invention relates to a current transformer coil disconnection detection device and method of an electronic wattmeter, and more particularly, to an apparatus and method for detecting coil disconnection of a current transformer for detecting the magnitude of the current signal in the wattmeter.

Until now, mechanical watt-hour meters have been mainly used to measure the use of electric energy in homes, shops and factories. This mechanical wattmeter uses mechanical rotational number difference as an indicator, so even if there is a power failure during use, the numeric indicator shows the value measured so far so that the weighing value can be checked.

However, in recent years, as the power generation of the industry and electricity consumption increase, the effective power amount (kWh), reactive power amount (kVARh), power factor and time of use metering are also remote metered with one meter. There is a demand for electronic electricity meters having a multi-function such as a meter reading system. Therefore, the electronic wattmeter has recently been used a lot, and this electronic wattmeter has a disadvantage in that the metered value inside the meter cannot be checked unless power is supplied due to a power failure. Therefore, the devising of device and method that can check the weighing data even in case of power failure is being studied.

Thus, an example of an electronic electricity meter is disclosed by following Document 1.

The technique disclosed in Document 1 relates to an electronic power meter, and it is described that the weighing data can be checked even during a power failure by a combination of a power supply and an operation switch input signal.

That is, the technique disclosed in Document 1 is composed of a power supply circuit section 10, a power / frequency conversion section 20 and a digital circuit section 30 as shown in FIG.

The power circuit unit 10 is a part that receives the AC power from the power supply side to rectify and converts the DC power into the required DC voltage. The primary side is connected to the power supply sides 1S and 2S, and its output is connected to the power supply circuit 12. Is connected in series to convert the AC power supply voltage to a predetermined small voltage, and rectifies the AC voltage of several to several tens of volts to convert the DC power, which is the operating power of each circuit component constituting the electricity meter. And a power failure circuit 13 for supplying auxiliary power for maintaining a clock function in case of power failure.

In addition, the power / frequency converter 20 is connected in parallel with the power supply side (1S, 2S) in series with the voltage signal converter 21, the power supply side (1S) for outputting a signal corresponding to the input voltage Multiplied by the current signal converter 22 for outputting a voltage signal proportional to the induced current coupled to the power, the output signal of the voltage signal converter 21 and the current signal converter 22 to calculate power A multiplier 23 for outputting (power = voltage x current) and then outputting the multiplier 23 to a frequency converter 24 for generating a frequency signal proportional to the power and outputting the frequency signal to the digital circuit unit 30. It is composed.

In addition, as shown in FIG. 2, the current signal converter 22 winds the secondary coil 222 around a ring-shaped core 221 such as a magnetic material, permalloy, and impregnates it. After the output terminals (k, l) are made in the current transformer (220), the terminal resistors (226) are connected to both ends of the output terminals (k, l) from the outside, and the current line 223 is formed in the center hole of the ring-shaped iron core (221). The secondary side current 225 is configured such that current as much as the number of turns of the primary side current secondary coil is passed through the primary side current 224 to flow therethrough.

The digital circuit unit 30 performs the measurement and calculation through the frequency output from the frequency converter 24 of the power / frequency converter 20, and accordingly performs the overall control device 31, the Oscillation circuit 32 for supplying the oscillation frequency required for the central processing unit 31 to operate through the crystal connection terminal of the central processing unit 31, for storing the data measured and calculated in the central processing unit 31 EEPROM 33, which is a memory, an operation switch 34 for inputting necessary data from a power meter such as time and date, and an external control signal output unit for outputting signals for remote meter reading, load blocking, and printer output of data ( 35) a power monitoring circuit 36 and an electrical user that monitor the state of AC power and extend the life of the battery so that the central processing unit 31 can operate in a power save mode in case of power failure. It is configured to data display unit (37) consisting of a LCD (LCD) to display the weight data.

Referring to the operation of the current transformer in the conventional electronic wattmeter configured as described above are as follows.

3 is a circuit diagram showing a simple electrical connection of the current transformer of the conventional electronic watt-hour meter.

As shown in FIG. 3, a current transformer is a type of transformer that converts a large current flowing from the primary side of the current signal converter 22 into a small current that an electronic component can process. = Secondary current × secondary winding number, i.e. I ₁ × N ₁ = I ₂ × Since _{N 2, I 2 = I 1} × a (N ₁ / N ₂₎ is satisfied is because one organic 2 by the primary current side current relationship is connected to the output ends (k, l) of the coil When flowing through the termination resistor 226, the voltage V _I obtained at both ends of V _IP and V _IN is obtained as V _I = R × I ₂ = R × I ₁ × (N ₁ / N ₂ ).

Subsequently, the voltage V _I and the voltage signal detected by the voltage signal converter 21 are applied to the multiplier 23 to calculate power. In this case, the frequency signal is generally referred to as a meter constant and is referred to as a meter constant (pulse / kWh). It is expressed in units.

The multiplier 23 multiplies (power = voltage x current) to calculate power using these signals and then supplies its output to the frequency converter 24, which is proportional to the power. A frequency signal is generated and output to the digital circuit unit 30. Accordingly, the central processing unit 31 of the digital circuit unit 30 counts the frequency signal input and performs a metering and arithmetic operation in which the amount of power used is converted to 1 kWh when the number of pulses equal to the instrument constant is accumulated, and then the EEPROM 33 At the same time, the weighing data is displayed on the data display unit 37 for the user to view.

[Document 1] Korean Utility Model Registration Publication No. 0273234 (Registered on April 11, 2002)

However, in the technique disclosed in Document 1, the secondary coil 222 is disconnected within the current transformer 220 due to overcurrent or other accumulated electrical factors during use of the current transformer as shown in FIG. 4. If a case occurs, even if the primary side current 224 flows a lot, the secondary side current 225 is not induced. That is, when the secondary current I ₁ is '0', V _I = R × I ₂ = R × 0 = 0 [V], and power (P) = V × 0 = 0 [W]. There was a problem such as not accurately weighing.

An object of the present invention is to solve the problems described above, it is possible to periodically detect whether disconnection occurs in the secondary coil of the current transformer to be able to send a display and warning messages to the outside.

Another object of the present invention is to enable the detection of disconnection of one or a plurality of secondary coils in three phases in a three-phase electricity meter so as to accurately measure the amount of power used.

In order to achieve the above object, a first feature of the present invention is an electronic wattmeter having a current transformer for outputting a voltage signal proportional to an induced current, the disconnection of the secondary coil through the voltage signal of the current transformer according to a control signal Control means for outputting a control signal to the disconnection detection means according to the detection cycle of the disconnection detection means for detecting the presence and output of the voltage signal of the current transformer, and displaying the presence or absence of disconnection to the user according to the disconnection detection result of the disconnection detection means It will include.

According to a second aspect of the present invention, in the first aspect, the disconnection detecting means includes: a relay unit for outputting a voltage signal of the current transformer to a switching path according to a control signal; And a disconnection detecting unit for detecting the disconnection of the current transformer through a voltage signal input from the relay unit by the control of the relay driving unit.

According to a third aspect of the present invention, in the second aspect, the relay unit outputs a voltage signal of the current transformer to a switching path according to a control signal, and controls a switch contact of the relay by the driving power to output a path. It is to include a woman coil to change.

According to a second aspect of the present invention, in the second aspect, the relay driver includes a transistor for applying or blocking driving power to the excitation coil by a control signal, and the transistor from the counter electromotive force when the driving power to the excitation coil is cut off. It includes a diode to protect.

In a second aspect of the present invention, in the second aspect, the disconnection detecting unit includes a photocoupler that outputs a low signal when a voltage signal is input from the relay unit, and outputs a high signal when it is not input.

A sixth aspect of the present invention is the second aspect of the present invention, wherein the disconnection detecting unit includes a Schmitt-trigger inverter that outputs a low signal when the voltage signal is input from the relay unit and a high signal when the voltage signal is small. will be.

According to a seventh aspect of the present invention, in the case of a periodic determination step of determining whether or not a preset detection cycle is set after initialization, and a detection result of the determination result of the periodic determination step, an instantaneous current value is read to determine whether the instantaneous current value is less than a set value. If the current value determination step to determine, if the current value determination step is less than the set value, the disconnection determination step for determining whether the current transformer is disconnected and if the current transformer is disconnected, the disconnection message is transmitted to the user. And the disconnection display step of updating and storing the read instantaneous current value to '0' at the same time.

In the seventh aspect of the present invention, in the seventh aspect, the instantaneous current value is read when the instantaneous current value is greater than or equal to a predetermined value as a result of the determination in the current value determination step or when it is not a disconnection as a result of the determination in the disconnection determination step. It is stored as it is.

A ninth aspect of the present invention is the seventh aspect, wherein the disconnection determining step is normal when the level of the voltage signal to be applied is not '0', and is secondary if the level of the voltage signal to be applied is '0'. And determining the disconnection of the coil.

A tenth aspect of the present invention is the seventh aspect, wherein the disconnection determining step compares the applied voltage signal with a reference signal to determine that the signal is normal when the reference signal is greater than or equal to the reference signal, and that the disconnection of the secondary coil is less than the reference signal. It is to include a step.

An eleventh aspect of the present invention is the tenth aspect, wherein the reference signal is in the range of the driving power level of the analog-to-digital converter ADC.

As described above, according to the current transformer coil disconnection detecting apparatus and method of the electronic watt-hour meter according to the present invention, when the current transformer secondary coil disconnection occurs in single-phase and three-phase wattmeter, it detects the non-quantity or under-metering by disconnection By preventing it, the effect that the accurate power consumption can be metered is obtained.

In addition, according to the coil disconnection detection device and method of the electronic watt-hour meter according to the present invention, the effect of minimizing the performance of unnecessary detection operation by performing the detection of the disconnection in the secondary coil of the current transformer only when it is less than the periodic and set value, not in real time. Obtained.

Briefly describing the present invention, the present invention includes a power supply circuit unit 100, a power signal conversion unit 200, and a digital circuit unit 300. In particular, the power signal conversion unit 200 is provided with disconnection detecting means for periodically detecting the disconnection of the secondary side of the current transformer 400, thereby preventing the non-metering or under-measurement due to disconnection in advance, thereby making it an energy efficient electronic power meter. Management of the

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. In addition, in describing this invention, the same code | symbol is attached | subjected and the repeated description is abbreviate | omitted.

5 is a block diagram briefly showing an overall configuration of an electronic watt hour meter according to an embodiment of the present invention.

As shown in FIG. 5, the electronic wattmeter includes a power circuit unit 100, a power signal converter 200, a digital circuit unit 300, and a data display unit 390, of which the power circuit unit 100 is a power source side. Power supply circuit 110 for converting into DC voltage, which is the operating power of each circuit component constituting the electricity meter, rectified by receiving AC power input from the power supply and an electrostatic compensation unit for supplying auxiliary power for maintaining a clock function in case of power failure ( 120).

In addition, the power signal conversion unit 200 is connected in parallel with the power supply side (1S, 2S) and connected in series with the voltage signal conversion unit 210, the power supply side (1S) for outputting a signal corresponding to the input voltage Frequency, instantaneous voltage, instantaneous current, using the current signal converter 220 and the output signal of the voltage signal converter 210 and the current signal converter 220 for outputting a voltage signal proportional to the induced current It is composed of a power measurement unit 230 for calculating the phase angle and instantaneous power of the voltage and current.

In addition, the digital circuit unit 300 performs the measurement and calculation through the signal output from the power measurement unit 230 of the power signal conversion unit 200, and accordingly performs the overall control unit 310, An oscillation circuit 320 for supplying an oscillation signal necessary for the central processing unit 310 to operate through a crystal connection terminal of the central processing unit 310, and storing data measured and calculated by the central processing unit 31. Non-volatile memory 330, operation switch 340 for inputting the data required in the electricity meter, such as time, date, time and date, day of the week and leap year used to generate a reference time for the instrument operation RTC (Real Time Clock, 350), optical / modem communication unit 360 which performs communication for setting and reading data from an external PC, for blocking of load, printer output of data, warning message, etc. A control signal output unit 370 for outputting a call, a power monitoring circuit 380 for monitoring the state of the AC power to extend the life of the battery so that the central processing unit 310 can operate in a power saving mode in case of power failure The data display unit 390 is configured of an LCD to display the weighing data to the user alternately.

In addition, the current signal conversion unit 220 is composed of a relay unit 500, a relay driver 600 and a disconnection detection unit 700, as shown in Figure 6, the double relay unit 500 is a magnetic material permalloy The output terminal k of the current transformer 400 wound around the secondary coil 420 on a ring-shaped core 410, such as permalloy, is connected to the relays RY1 increasingly (3, 6). The contacts 3 and 6 are normally connected to the contacts 2 and 7 through the switch 510, respectively, and the contacts 2 and 7 are respectively connected to the terminals V _IP and V _IN of the power measurement unit 230. Connect.

In addition, the relay driver 600 connects the current limiting resistor R2 to the output terminal CT_CHK of the central processing unit 310 and the base of the transistor TR1 in series, and the emitter of the transistor TR1 is grounded. At the same time, the collector is connected in series with the control terminal 8 of the excitation coil 520 of the relay unit 500 and at the same time a diode for protecting the transistor TR1 from back EMF when the power supply to the excitation coil 520 is cut off. Connect to (D1).

In addition, the disconnection detecting unit 700 connects the current limiting resistor R3 connected in series to the relay contacts 4 and 7 of the relay unit 500 to one side of the light emitting device of the photocoupler PT1 in series. In addition, one side of the light receiving element of the photocoupler PT1 is connected in series to a resistor R4 connected in series to the power supply voltage Vcc and a terminal CT_STS of the central processing unit 310.

In addition, in the embodiment of the present invention, the photocoupler is applied as the disconnection detecting means, but the same result can be obtained by using the Schmitt trigger inverter instead of the photocoupler.

Referring to the drawings the operation of the embodiment according to the present invention configured as described above is as follows.

7 is a flowchart illustrating a disconnection detection process of a current transformer according to an embodiment of the present invention.

As shown in FIG. 7, after performing a general initialization operation such as initial condition adjustment for a normal operation of the electronic watt-hour meter, the power measurement unit 230 is provided through the voltage signals output from the voltage signal converter 210 and the current signal converter 220. When the result of the calculation is transferred to the central processing unit 310, the central processing unit 310 accumulates this to determine whether the detection period is set in the middle of performing integration (step 100). For example, if it is set to every 5 minutes, it is determined whether the time is an integer multiple of 5 minutes.

In the case of the detection result of the step (Step 100), the instantaneous current value calculated by the current measuring unit 230 is read to determine whether the instantaneous current value is less than the set value (Step 200 to 300).

At this time, if the current value is higher than the current meter of the watt-hour meter, the instantaneous current value currently read is stored in the nonvolatile memory 330 and the disconnection detection operation is terminated (Step 400). If less, the operation of determining whether the secondary coil of the current transformer 400 is disconnected (step 500).

That is, the CPU 310 outputs a control signal (high signal) to the transistor TR1 of the relay driver 600 through the terminal CT_CHK, as shown in FIG. 8, and accordingly, the transistor TR1. ) Is turned on to allow current to flow in the excitation coil 520 of the relay unit 500. The excitation coil 520 has a magnetic property as a current is applied, thereby switching the switch 510 of the relay RY1 from the contacts 2 and 7 to the contacts 4 and 5, respectively.

By the contact switching operation of the relay RY1, a voltage signal is inputted to the light emitting device of the photocoupler PT1 of the disconnection detecting means 700, and the light receiving device is turned on to thereby turn on the terminal of the central processing unit 310. 'L' signal is inputted to CT_STS).

Therefore, when the output signal of the disconnection detecting means 700 is low (L), the central processing unit 310 determines that the disconnection is not a disconnection. However, as shown in FIG. When disconnection occurs in the difference coil, since there is no voltage signal applied to the light emitting device of the photocoupler PT1, the light receiving device of the photocoupler PT1 is turned off, and thus the central processing unit 310 A high signal is input to the central processing unit 310 so that the disconnection occurs in the secondary coil of the current transformer 400.

In the case where the central processing unit 310 determines that the current transformer 400 is disconnected, a disconnection message is displayed on the data display unit 390 and, if necessary, transmitted to the user through the external control signal output unit 370. The current read instantaneous current value is updated to '0' and stored (Step 600).

In addition, since the disconnection detecting means 700 is used for the purpose of TTL level conversion, the photocoupler PT1 is not intended for isolation between the primary side and the secondary side. Compares the voltage signal and the reference signal through the relay unit 500 and outputs a 'low' signal when the reference signal is higher than the reference signal and a 'high' signal when the reference signal is lower than the reference signal. The signal is set to the drive power level range (1.5 to 3.3V) of the analog-to-digital converter (ADC).

Therefore, the central processing unit 310 determines the normal or disconnection through the output signal (low signal or high signal) of the Schmitt trigger inverter.

As mentioned above, although the invention made by this inventor was demonstrated concretely according to the said Example, this invention is not limited to the said Example, The Schmitt trigger which is not a photocoupler as a disconnection detection means in the range which does not deviate from the summary, Of course, it can be changed in various ways such as using an inverter.

1 is a block diagram briefly showing the overall configuration of a conventional electronic electricity meter.

Figure 2 is a circuit diagram showing a brief configuration of a conventional current signal converter.

3 is a circuit diagram showing a simple electrical connection of the current transformer of the conventional electronic watt-hour meter.

4 is a circuit diagram schematically showing disconnection in a current transformer of a conventional electronic wattmeter.

5 is a block diagram briefly showing an overall configuration of an electronic wattmeter in accordance with an embodiment of the present invention.

6 is a circuit diagram showing a configuration of a current signal conversion unit according to an embodiment of the present invention.

7 is a flowchart illustrating a disconnection detection process of a current transformer according to an embodiment of the present invention.

8 is a circuit diagram showing the operation in the case of not the electrical disconnection of the current transformer according to an embodiment of the present invention.

9 is a circuit diagram illustrating a detection operation during electrical disconnection of a current transformer according to an exemplary embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100: power circuit unit 200: power signal conversion unit

220: current signal conversion unit 230: power measurement unit

300: digital circuit unit 310: central processing unit (CPU)

400: current transformer 420: secondary coil

500: relay unit 510: switch

520: coil coil 600: relay drive unit

700: disconnection detection unit RY1: relay

TR1: Transistor PT1: Photocoupler

Claims (11)

An electronic wattmeter having a current transformer for outputting a voltage signal proportional to the induced current, Disconnection detection means for detecting and outputting the disconnection of the secondary coil through the voltage signal of the current transformer according to the control signal; And control means for outputting a control signal to the disconnection detecting means according to the detection period of the voltage signal of the current transformer, and displaying the disconnection to the user according to the disconnection detecting result of the disconnection detecting means, The disconnection detecting means includes a relay unit for outputting a voltage signal of the current transformer to a switching path according to a control signal, The relay unit A relay for outputting a voltage signal of the current transformer to a switching path according to a control signal; The coil disconnection detection device of the electronic watt-hour meter, characterized in that it comprises an excitation coil for controlling the switch contact of the relay by a drive power source to change the output path. According to claim 1, wherein the disconnection detecting means A relay driver for controlling an output path by applying the driving power to the relay unit when a control signal is input from the control unit; And a disconnection detection unit for detecting the disconnection of the current transformer through the voltage signal input from the relay unit under the control of the relay driving unit. delete The method of claim 2, wherein the relay driving unit A transistor for applying or blocking driving power to the excitation coil by a control signal; And a diode for protecting the transistor from back electromotive force when the driving power is cut off to the excitation coil. According to claim 2, wherein the disconnection detection unit And a photocoupler for outputting a low signal when the voltage signal is input from the relay unit and for outputting a high signal when the voltage signal is not input. According to claim 2, wherein the disconnection detection unit And a Schmitt-triggered inverter for outputting a low signal when the voltage signal is input from the relay unit and a high signal when the voltage signal is smaller than the reference value. Period judging step of determining whether or not the preset detection cycle after initialization, A current value judging step of judging whether the instantaneous current value is less than a set value by reading the instantaneous current value in the detection period of the determination result of the periodic judging step; The disconnection determination step of determining whether the current transformer is disconnected when the current value determination step is less than the set value; In the case of disconnection of the current transformer as a result of the determination of the disconnection determination step, the disconnection display step of transmitting a disconnection message to the user and updating and storing the read instantaneous current value to '0' includes the coil of the electronic power meter. Disconnection detection method. The method of claim 7, wherein If the instantaneous current value is greater than the set value as the determination result of the current value determination step or if the disconnection determination step is not disconnection, the current reading instantaneous current value is stored as it is. . The method of claim 7, wherein the disconnection determining step If the level of the applied voltage signal is not '0' is normal, if the level of the applied voltage signal is '0' coil disconnection detection of the electronic power meter, characterized in that it comprises the step of determining the disconnection of the secondary coil Way. The method of claim 7, wherein the disconnection determining step And comparing the applied voltage signal with a reference signal to determine that the signal is normal when the reference signal is greater than or equal to the reference signal, and determining that the secondary coil is disconnected when the reference signal is less than the reference signal. The method of claim 10, The reference signal is a coil disconnection detection method of an electronic power meter, characterized in that the drive power level range of the analog-to-digital converter (ADC).

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