KR100724097B1 - On-site transportable instrument for test of watt-hour meter - Google Patents

Abstract

The present invention relates to a power meter test apparatus, and more particularly to a mobile power meter test apparatus for field testing. To this end, a transformer (VT) connected in parallel between the power transmission line and the wattmeter 10 of the instrument under test to reduce the voltage; An electronic standard power meter 80 connected to the transformer VT; A current supply means 30 which is connected to a transformer VT and supplies a current of the same phase by adjusting a phase with respect to the wattmeter 10 and the electronic standard wattmeter 80 of the device under test; An error detecting means (90) for detecting an error in the output of the meter (10) of the instrument under test with respect to the output of the electronic standard meter (80); and is provided with a current supply means (30), an electronic standard meter (80), and The error detecting means 90 is provided inside the movable case.

Power, Field, Mobile, Error Detection, Current Source, Phase

Description

On-site transportable instrument for test of watt-hour meter

1 is a schematic block diagram of a mobile power meter test apparatus for field tests according to the present invention;

FIG. 2 is an electronic circuit diagram of the electronic standard power meter 80 in the block diagram shown in FIG.

FIG. 3 is an electronic circuit diagram of a current supply source 30 having a phase adjusting function in the block diagram shown in FIG.

4 is an electronic circuit diagram of the error detector 90 in the block diagram shown in FIG.

FIG. 5 is a flowchart showing an operation sequence of the error detector 90 shown in FIG. 4;

6 is a graph showing a measurement error of the electronic standard power meter 80 for 10 A change in power factor 1, voltage 220 V, current 0.5 A for the power meter test apparatus according to the present invention,

7 is a graph showing a measurement error of the electronic standard power meter 80 for a 10 A change in power factor 0.5 (lead, lag), voltage 220 V, current 0.5 A for the power meter test apparatus according to the present invention.

8 is a photograph of the appearance of the electronic standard power meter 80 according to the present invention.

<Description of the symbols for the main parts of the drawings>

10: power meter (WHM) of the device under test,

20: load,

30: current supply source,

40: power supply,

50: level controller,

60: phase adjuster,

70: current amplifier,

80: TDM type electronic standard power meter,

90: error calculation and display unit (error detection unit),

100: field power meter tester,

110: range selector switch,

150: electronically compensated two-stage CT,

200: range selection switch.

The present invention relates to a power meter test apparatus, and more particularly to a mobile power meter test apparatus for field testing.

As the nation's economy grows and the standard of living of the people improves, the use of electricity is increasing every year due to the large size of electric equipment. The electricity meter used in the electricity trade is also expanding the metering range of the load current in response to the increasing power consumption. The electricity supply and demand meter mainly consists of three kinds of active electricity meter, reactive electricity meter, and maximum demand electricity meter, and the largest quantity is the induction type ordinary electricity meter, which is currently about 10 million units. The ordinary electricity meter has been remarkably changed to improve the performance as the demand for high precision to ensure the reliability of power consumption and the fairness of electricity transactions accompanying the development of various home appliances.

The electricity meter has been improved in the direction of low price, high precision, and durability thanks to the development of design technology as well as material technology, machining technology, measurement technology, and electronic technology. have. The development of the performance aspect of the inductive wattmeter includes the measurement accuracy, the range of load current that guarantees the measurement accuracy, and the durability.However, in recent years, the development and production of electronic wattmeters has been greatly limited due to the limitations in accuracy and multifunction in principle and structure. It is developing. In particular, the practical use of 0.5- and 1.0-class electronic wattmeters has been realized, and the electronic standard wattmeters of class 0.2 are also used for measurement and testing of wattmeters. In addition, the electronic meter is not only precise metering of the amount of power used, but also the use of semiconductor technology and computer technology, the meter reading is changing to a multi-functional metering metering such as automation, monitoring and control.

In Korea, the production of meter was started from around 1962 to the production of type I instruments, and developed in 1975 as type II instruments. Was type III. In the 1990s, the era of type IV instruments began, and now it is the era of mixed type III, IV and electronic meters. The instrument will gradually change its error with age over time. The secular variation of the instrument is closely related to the instrument management method, and there is a certification system as the instrument's life management method. In the case of Type III, the validity period of the instrument is 7 years, and the effective instrument is to be adjusted and recalibrated.

Although it varies from country to country, the United States has two types of certifications: 8 years, 20 years in the UK, 16 years in Germany, 7 years in Japan and 10 years in Japan, and 10 years in France, 15 years in Switzerland, 18 years in Norway and 5 years in China. . In general, industrialized industrialized countries have a long validity period, while industrialized countries have a shorter validity period due to the reliability of the instrument. In Korea, both mechanical and electronic electricity meters are superior in performance and reliability in comparison with the past.

In fact, when the validity period of the test is reached, the meter that collects the electricity meter and undergoes a certain test such as an error test is determined to be repaired or discarded. In this process, instruments that have no problem in terms of performance can be reused. If this can be determined through direct testing in the field, it can be determined that effective countermeasures against human and economic loss can be prepared.

Accordingly, the present invention has been made to solve the above problems, and a first object of the present invention is to provide a mobile power meter test apparatus for field testing that can determine the availability of a power meter on-line.

As described above, an object of the present invention is a transformer (VT) connected in parallel between the power line and the meter of the meter under test (10) to reduce the voltage;

An electronic standard power meter 80 connected to the transformer VT;

A current supply means 30 which is connected to a transformer VT and supplies a current of the same phase by adjusting a phase with respect to the wattmeter 10 and the electronic standard wattmeter 80 of the device under test;

And error detecting means (90) for detecting an error in the output of the meter of the instrument under test with respect to the output of the electronic standard meter (80).

The current supply means 30, the electronic standard power meter 80 and the error detection means 90 can be achieved by a field tester mobile power meter test apparatus, characterized in that provided in the movable case.

The error detecting means 90 preferably further includes display means for displaying the detected error.

In addition, the error detection means 90 is more preferably to detect the rotational speed of the disc with an optical sensor when the power meter 10 of the device under test is mechanical, and count the output signal of the optical sensor in a pulse waveform.

Further, the error detection means 90 is more preferably counted by using an infrared pulse sensor when the power meter 10 of the device under test is electronic.

In addition, the current supply means 30,

A level controller 50 connected to the transformer VT to adjust the magnitude of the voltage;

A phase adjuster 60 connected in series with the level controller 50;

A current amplifier 70 connected in series with the phase adjuster 60;

A current transformer (CT) having a secondary side connected between the wattmeter 10 of the instrument under test and the electronic standard wattmeter 80, and one end of the primary side connected to the current amplifier 70;

The range selection switch 110 and the electronic amplifier A6 connected in series between the other end of the primary side and the current amplifier 70 may be most suitable.

In addition, another current transformer CT1 connected in series to the secondary side of the current transformer CT for precise current supply and measurement;

Another current transformer (CT1) further includes an electronic amplifier (A7) for amplifying the primary output signal,

It may be most appropriate that the signal amplified by the electron amplifier A7 is fed back to the electron amplifier A4.

Here, the range selection switch 110 may be connected to one of 0.1, 1, 5, 10 A.

Other objects, specific advantages and novel features of the invention will become more apparent from the following detailed description and the preferred embodiments described in conjunction with the accompanying drawings.

The invention will now be described in detail with reference to the accompanying drawings, in which preferred embodiments are shown.

The test device was developed in three parts: electronic standard power meter, current source with adjustable phase change, and error detector. The electronic standard meter is developed by TDM (Time Division Multiplier) method and the accuracy is better than 0.1%. The current source converts the voltage supplied to the power meter under test into a low voltage through a transformer, and then develops a current source 30 using a phantom load method to output up to 10 A. The error detector indicates an error by comparing the outputs of the electronic standard meter 80 and the power meter 10 under test and determines whether the meter 10 is through this value. The error detector 90 uses a sensor that can sense the rotation or pulse of the meter under test 10 so that both the mechanical and the electronic meter can be tested.

The on-site electricity meter test apparatus basically consists of an electronic standard electricity meter 80, a current supply source 30 that can adjust a phase change, and an error detector 90. As shown in FIG. 1, the input voltage of the power meter (WHM) 10 of the instrument under test remains connected to the transmission line, and the input current portion is connected to the current transformer CT, which is an output element of the current supply source 30. The current supplied from the current transformer CT is connected to the input current terminal of the electronic standard power meter 80 through the input current terminal of the meter 10 of the instrument under test. The amount of power supplied to the wattmeter 10 of the meter under test is calculated by multiplying the power line voltage supplied from the transmission line, the current supplied from the current supply source 30, the power factor by the phase adjuster 60, and the use time. Is output. The amount of power WHM (Wh) supplied to the wattmeter 10 of the device under test is [Equation 1].

Where V is the power line voltage and cos φ and t represent the power factor and the time when power is supplied by the phase adjuster 60, respectively. The output amount is supplied to the error detector 90 through a sensor attached to the meter 10 of the instrument under test, and indicates the degree of error compared to the output of the electronic standard meter 80. If the meter 10 of the instrument under test is mechanical, it is output by the number of revolutions of the disc, and if it is a digital meter, it is converted into pulses and output.

The amount of power supplied to the electronic standard meter 80 should also be the same as the amount of power supplied to the meter (WHM) 10 of the instrument under test. The current supplied from the transmission line is converted into a small signal voltage Va in the transformer VT and used as the current signal source of the current supply source 30, and then to the measured input voltage Va of the electronic standard power meter 80 (Va = V / n). Used. The power amount STD (Wh) supplied to the electronic standard power meter 80 is shown in [Equation 2].

Where n represents the ratio of the primary and secondary windings. And by definition, the error in power is expressed as:

When the transformer (VT) is ideal, the power supplied to the electronic standard power meter 80 and the power supplied to the power meter (WHM) 10 of the device under test is represented by [Equation 1] and [Equation 2] [Equation 3] ]

By multiplying the output ratio of the electronic standard power meter 80 by (1 / n) by the winding ratio n of the transformer, a measurement error value in an ideal case may be obtained.

Hereinafter, an electronic standard power meter according to the present invention will be described. Current inputs typically use a current transformer (CT) for electronic power measurements. Since the current transformer CT has to wind a large number of coils, a large error occurs even when the burden is small. This is because the CT internal burden cannot be ignored. Using a two-stage current transformer (CT) can solve the problem caused by the internal burden of the current transformer (CT). There are two causes of errors in the CT.

One of them is magnetizing current and the other is caused by incomplete coupling between primary and secondary windings. The first error can be greatly reduced by applying two-stage current transformer (CT) technology, but the second problem can be solved only by using two-stage current transformer (CT) based on electronic compensation. Current transformer CT implemented in one embodiment of the present invention uses a feedback winding to reduce the loss caused by the input current. Current transformer CT is composed of primary winding, secondary sensing winding, feedback winding, and amplifier that amplifies the signal sensed from sensing winding and supplies it to feedback winding.The voltage across load resistance is the output of current transformer CT. do.

Although the input current is not sufficiently delivered to the secondary side due to the core shunt loss impedance of the current transformer CT, the loss is compensated for through the feedback winding, the electron amplifier, the active filter, and the compensation coil. Therefore, it is possible to compensate for the loss caused by the shunt loss impedance by achieving a magnetic balance inside the current transformer CT and to improve the reduction of the voltage generated by the load resistance.

2 is a block diagram of an electronic standard power meter applied in an embodiment of the present invention. As shown in FIG. 2, an electronically compensated two-stage current transformer (CT) 150, a power measurement circuit for multiplying the current, the voltage, and the phase between the voltage and the current by a TDM method, and a pulse generation to indicate an amount of power. It consists of a circuit. The current and voltage input terminal of the power measurement circuit uses electronically compensated two-stage current transformer (CT) using electronic amplifiers (A5, A6) for current measurement, and voltage measurement using resistance and current amplifier (A1). .

The TDM method consists of a pulse-width modulation circuit (PWM) and a pulse-height modulation circuit (PHM). The pulse-width-height multiplier is based on an input voltage (e) that adjusts the sequential pulse width, or duty cycle, and another input voltage (i) that is made proportional to the magnitude of the sequential pulse. A low pass filter is used to obtain the DC component of the sequential pulse. The output of the low pass filter is obtained with a DC output proportional to the product of e and i. The electronic standard meter manufactured here was developed and used as a standard meter with 0.1% accuracy by improving the Tomota-Sugiyama-Yamaguchi multiplication circuit with 0.2% accuracy.

It operates in the input voltage range 120, 240 V, input current range 0.1, 1, 5, 10 A and the output is pulsed. The instrument constant is 10 pulses / kWh. The instrument constant is the value of the output pulse determined by the magnitude of the input voltage and current and becomes pulse / Ws at 240 V, 5 A (1200 W). The output pulse in this embodiment is an open collector system, and the external input voltage is 5V to 30V DC. And the characteristic about the amount of power is measured according to IEC 1036.

Hereinafter, the current supply source 30 according to the present invention will be described. A self-adjustable current supply source 30 is called a transconductance amplifier, which supplies a current proportional to the input voltage and independent of the voltage of the load 20 stage. Such current sources are useful for calibration and testing of instruments where a stable current source is required. Precision power calibration and test techniques have recently focused on stable voltage and current amplification to provide phantom load source power to the equipment under test. Especially in calibrations or tests that require power factor adjustment, the phase shift problem is solved by using a quiescent power source.

In order to supply an electric current capable of adjusting the phase with the same phase to the wattmeter 10 and the electronic standard wattmeter 80 of the device under test, a current source using a load-bearing power source was manufactured as shown in FIG. 3. The voltage Va converted through the transformer VT is converted into a current in the electron amplifier A1 and functions as a level controller 50 for controlling the magnitude of the voltage by amplifying the voltage in the electron amplifier A2. The electronic amplifier A3, the resistance of the input terminal, and the capacitor function as a phase adjuster 60 to adjust the phase. Here, the phase refers to the phase between the voltage and the current supplied to the meter 10 of the meter under test and the electronic standard meter 80. The meter error test shall be fixed at power factor pf = 1 and pf = 0.5.

The input signal of the electronic amplifier A4 compensates for the slight phase change and amplitude difference between the output signal of the electronic amplifier A3 and the output current I. The phase and amplitude of the output current through the current transformer CT1 are compensated for. Measure The power amplifier (A5) has four LM12 (National semiconductor, 150 W) electronic amplifiers connected in parallel. The quiescent load output current is 0.1, 1, 2, or 2 on the secondary side of the current transformer CT according to the selection of the range selection switch 200. 5 and 10 A are output. The current transformer CT causes phase and amplitude changes between the primary and secondary due to incomplete coupling between the magnetizing current and the primary and secondary windings. For precise current supply and measurement, a compensation current transformer CT1 is added to the secondary side of the current transformer CT to sense a change in output and feed it back to the electronic amplifiers A7 and A4 to compensate.

Hereinafter, an error detector 90 according to the present invention will be described. The error detector 90 compares the outputs of the electronic standard wattmeter 80 and the power meter 10 under test to indicate an error. The error detector 90 determines the quality of the wattmeter through this value. The error detector 90 uses an optical sensor that can sense the rotation or pulse of the meter under test so that both mechanical and electronic meters can be tested. 4 is an electronic circuit diagram of the error detector 90. As shown in FIG. 4, when the power meter under test 10 is a mechanical type, the rotation speed of the disc is detected by an optical sensor, and a pulse corresponding to the detected rotation speed is supplied to CON4. The waveform is shaped at U3A and supplied to microprocessor AT89C51 pin 12. CON3 receives the reference pulse output from the electronic standard meter 80 and connects it to AT89C51 pin 14 and pin 15. The maximum frequency of pulses that can be accepted at CON4 is 60 MHz and the maximum frequency of pulses that can be accepted at CON3 is 100 MHz. The switches shown on the right side of FIG. 4 are keys for inputting the function of the error detector 90. If the power meter 10 under test is electronic, it is detected through a pulse sensor (IR sensor).

5 is a flowchart illustrating a process of error operation and display of the error detector 90. As shown in Figure 5, the frequency of the output pulse of the power meter for test 10 is about 0.01 ~ 1 Hz, if more than a few Hz can be adjusted through a frequency divider. Frequency distribution is software-adjusted and configured for distribution up to 1:10, 1: 100, 1: 1,000, 1: 10,000, 1: 100,000. Calculate the instrument constant and reset number (Reset No) of the power meter under test 10 and set it to N. Next, the number of reference pulses Nr of the electronic standard watt-hour meter 80 is counted, and N and Nr are calculated by Equation (3) in the microprocessor as an error.

Hereinafter, the electronic standard power meter 80 will be described. The configuration of the mobile power meter tester for field test of the present invention that satisfies the characteristics recommended in the standard of IEC 1036 will be described. 6 is a graph showing the results of the error measured while varying the voltage 220 V, the power factor 1, and the current from 0.1 A to 10 A. FIG. 7 is a graph showing the results of the error measured while varying the voltage 220 V, power factor 0.5 (lag), 0.5 (lead), and current 0.1 A to 10 A. FIG. Power and energy calibrator (Rotek: 8000), power and energy standard (Radian research: RD31, accuracy 0.005%), error calculation and display unit 90 are used for the characterization.

The IEC limits shown in FIGS. 6 and 7 (pf = 1, pf = 0.5) indicate the upper and lower limits of the error specified in IEC 1036, and the characteristics of the developed electronic standard meter 80 in the middle. . Generally, the calibration system is manufactured so that the input voltage of the standard power meter is 220 or 240 V and the input current is 5 A. The maximum voltage and current measurement range is set to 20% of the nominal range. Supply voltage, current and phase by Power and energy calibrator (Rotek: 8000), and connect power and energy standard (Radian research: RD31) and our electronic standard meter 80 in series with current and voltage in parallel Each output was measured by the error calculation and display unit 90.

As can be seen from the experimental example of Figure 6 and 7, the error from 0.1 A to 10 A showed better than ± 0.05%. These results are regarded as belonging to an accuracy class 0.1 (± 0.1%) when comparing the error limits specified in IEC 1036. 8 is an example of an appearance photograph of the electronic standard power meter 80 according to the present application.

Hereinafter, specific experimental data of the current supply source 30 will be described. Configuration and performance of the current supply source 30 according to an embodiment of the present application is as follows. E.g:

1) Maximum output current at CT primary: 5 Arms

2) Maximum output current at CT 2nd order: 10 Arms

3) Output frequency: 30 Hz ~ 1 kHz

4) Compliance Voltage: 3 Vrms (at 5 A)

5) Output offset current ≤ 0.2 mA

6) Phase shift (between input voltage and output current): 181 deg (60 Hz)

In order to evaluate short-term stability, a power and energy standard (Radian research: RD31, accuracy 0.005%) was used. After preheating for 2 hours, amplitude stability was less than 0.005% and phase stability was 80 μrad over 5 minutes.

Hereinafter, specific data of the error detector 90 will be described. Power and energy standard (Rotek MSB 100, accuracy 0.005%) and power and energy calibrator (Rotek: 8000) were used to measure the characteristics of the error detector 90 of the present application. Rotek: 8000 is used to supply voltage 220 V, current 5 A, power factor 1 to the MSB100 and output pulses of the MSB100 to CON3 and CON4 of the error detector 90 simultaneously. The signal supplied to CON4 was supplied through a frequency divider of 1: 100,000, and a virtual test was performed with the output pulse of the power meter 10 under test.

As a result of testing the error according to the flowchart shown in FIG. 5, the measurement error was 0%. And the same result was obtained with power factor 0.5 (lead, lag). According to the results of this experiment, it can be seen that the error of the error detector 90 itself is 0%.

The field power meter test apparatus 100 according to the present invention basically consists of an electronic standard power meter 80, a current supply source 30 that can adjust a phase change, and an error detector 90, and measured respective characteristics. Each device was combined to test the characteristics of the overall field meter test device 100. The test was measured using an on-site electricity meter tester and a power and energy standard (Radian research: RD31, accuracy 0.005%). Table 1 shows the uncertainty of the system used for the characteristic evaluation of the electricity meter test apparatus 100.

number Measurement element Uncertainty One Electronic standard meter error 0.1% 2 Amplitude Ratio Short-term Stability of Current Supply 0.005% 3 Phase ratio short-term stability of current supply 0.008% 4 Error in error detector 0 % 5 Power and power standards (RD31) 0.01% 6 Short-term stability of the power and power calibrator (ROTEK8000) 0.002% 7 Factor due to repeated measurement 0.01% Composite uncertainty About 0.1% Extended Uncertainty (k = 2) 0.2%

Therefore, according to one embodiment of the present invention as described above, it is possible to test the characteristics of the electricity meter on-line in the field, and by determining the acceptance by directly testing the electricity meter expired in the field in the field, human and economic It is a great help in value judgment. The test apparatus of the present invention is divided into an electronic standard power meter 80, a current supply source 30 that can adjust a phase change, an error detector 90, and the like. The test apparatus includes a voltage of 240 V, a current of 0.1 to 10 A, and a power factor. It can be seen that it has excellent performance with a measurement range of 1, 0.5 (lead, lag) and an uncertainty of 0.2% at a confidence level of about 95% (k = 2).

Therefore, it can be used to test and calibrate the electronic power converter for remote meter reading by using the electronic standard power meter in the field, and can also be used as a power source for testing the power meter, the voltmeter, and the ammeter by using the current source that can adjust the phase change. Can be.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it will be readily apparent to those skilled in the art that various other modifications and variations can be made without departing from the spirit and scope of the invention. It is obvious that all modifications fall within the scope of the appended claims.

Claims (7)

A transformer (VT) connected in parallel between the power transmission line and the wattmeter 10 of the device under test to reduce the voltage; An electronic standard electricity meter 80 connected to the transformer VT; A current supply means 30 connected to the transformer VT and supplying a current having the same phase by adjusting a phase with respect to the power meter 10 and the electronic standard power meter 80 of the instrument under test; Error detecting means (90) for detecting an error in the output of the power meter (10) of the instrument under test with respect to the output of the electronic standard power meter (80); And Display means for displaying an error detected by the error detection means (90), The error detecting means 90 detects the rotational speed of the disc with an optical sensor when the power meter 10 of the device under test is mechanical, counts the output signal of the optical sensor as a pulse waveform, If the electricity meter 10 is an electronic counting using an infrared pulse sensor, The current supply means 30, A level controller 50 connected to the transformer VT to adjust the magnitude of the voltage; A phase adjuster 60 connected in series with the level controller 50; A current amplifier 70 connected in series with the phase adjuster 60; A current transformer (CT) having a secondary side connected between the wattmeter (10) of the instrument under test and the electronic standard wattmeter (80), and one end of the primary side connected with the current amplifier (70); And a range selection switch 110 and an electronic amplifier A6 connected in series between the other end of the primary side and the current amplifier 70. Wherein the current supply means 30, the electronic standard power meter (80) and the error detection means (90) is a mobile power meter test apparatus for a field test, characterized in that provided in the movable case. delete delete delete delete The method of claim 1, Another current transformer CT1 connected in series to the secondary side of the current transformer CT for precise current supply and measurement; The another current transformer (CT1) further comprises an electronic amplifier (A7) for amplifying the primary output signal, The mobile amplification tester for field test, characterized in that the signal amplified by the electronic amplifier (A7) is fed back to the electronic amplifier (A4). According to claim 1, wherein the range selector switch 110 is a portable power meter tester for field test, characterized in that the connection with one of 0.1, 1, 5, 10A.

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