JPH03223679A - Watthour meter with automatic output pulse width switching type transmitter - Google Patents

Abstract

PURPOSE:To obtain a watthour meter wherefrom an output pulse can always be transmitted as a pulse of an optimum pulse width, by providing a means of determining a maximum pulse width which can secure the ratio between ON and OFF times of the output pulse. CONSTITUTION:When V/A is 110V/5A, a set transformation ratio 200, a multiplying factor 1 and a pulse weighting multiplying factor 1/100 in a three-phase three-wire system, for instance, output pulses per one hour in the case of a rated load are 19.060 and an input range is 19.060X1.5=28.590, since it is allowed to be 1.5 times at the maximum. A pulse period in this case is 3,600divided by 28.590=126ms, and therefore a microcomputer unit 7 makes determination that the regulation of the pulse period being 144ms or above is not met when an ON time is 120ms and an OFF time 24ms or above. Since the pulse period is 126ms as calculated in the above, the regulation is determined to be met when the ON time is 60ms and the OFF time 66ms. Thereby the output pulses can be optimized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to an improvement in a power meter with a transmitting device that transmits an output pulse.

(Background of the Invention) Electronic watt-hour meters are installed in the homes of electricity consumers to measure the amount of electricity used by the consumers, and also emit output pulses to transmit the measurement data to remote management offices, etc. Equipped with functions.

When transmitting and receiving pulses, the pulse width of each pulse should be wide in order for the pulse multiplier to measure the pulses reliably, and in order to improve the resolution of the data signal to be transmitted and received, It is desirable that the range of change in the number of pulses is wide.

Therefore, if the pulse constant of the pulse to be transmitted and received is known in advance, data signals can be reliably transmitted and received by using pulses with an appropriate pulse width and appropriate frequency, but electronic power When setting the pulse weight magnification in a wide range from 1/1 to 1/100 like a meter, and measuring a wide range from zero load power to rated load power, and transmitting and receiving as pulses proportional to that, If only one type of pulse width is used, depending on the measurement conditions and the amount of electricity to be measured, it may not be possible to satisfy the absolute condition for a pulse that the pulse width is smaller than the pulse period.
A situation may occur in which the output pulse is always on and is not output as an apparent upper pulse.

In other words, the pulse width normally used in a power meter is
When the pulse weight magnification is 1/1 and 1/10, JI
It is set so that there is no problem with the function up to 300% of the rating specified in S.

The specified error for input current according to JIS is up to 1.2 times. Since an over-input range of about 1.5 times is normally permissible, it is necessary to assume that the number of output pulses based on the IT result satisfies these ranges.

For example, in a three-phase, three-wire power meter with a rating of 110 V and 15 A, the set transformation ratio is 200 and the pulse weight multiplier is 1/100.
When transmitting and receiving pulses (pulse width: on time: 120 ms, off time: 24 ms, which is 20% of the on time), the number of output pulses per hour for the rating in this case is approximately 19.060 pulses. However, if the input range is allowed to be 1.5 times the rated value, the number of output pulses corresponding to the maximum load power will be approximately 28.590 pulses, so the pulse period will be approximately 126 ms, which is the specified pulse period. >120+24 (ms) cannot be satisfied,
Since data cannot be transmitted or received near the maximum load power amount, the pulse width must be 100 ms or less in order to prevent errors from occurring.

Therefore, in order to avoid such errors in pulse transmission and reception, even at the maximum number of pulses per unit time that can be transmitted and received, that is, at the maximum pulse frequency,
It is only necessary to set the pulse width to be smaller than the pulse period in advance so that transmission and reception can be performed, but this can be done automatically under various setting conditions and weighing data can always be output using pulses with the optimal pulse width. The development of a power meter with a transmitter was expected.

(Objective of the Invention) An object of the present invention is to solve the above-mentioned problems and provide a watthour meter with an output pulse width automatic switching type transmitting device that can always transmit an output pulse as a pulse with an optimal pulse width.

(Features of the Invention) In order to achieve the above object, the present invention provides a discriminating means for discriminating the maximum pulse width that can ensure the ratio of on/off times of output pulses among a plurality of predetermined pulse widths. Then, an output pulse having the pulse width determined by the determining means is emitted, ! A pulse width control means for controlling the device is provided, so that when a small pulse weight multiplier is set, that is, when there is a high possibility that the period of the output pulse becomes small, for example, with a pulse width of 120 rns, the output If the pulse on/off time ratio cannot be maintained,
It is characterized in that the pulse width is automatically switched to 60ms.

(Embodiment of the invention) 1st rI! J is a block diagram of a watt-hour meter with an automatic output pulse width switching type transmitter, which is an embodiment of the present invention.

FIG. 2 is a diagram of a power distribution system of a power meter with an automatic output pulse width switching type transmitter.

As shown in FIG. 2, the power meter 1 with automatic output pulse width switching type transmitter includes an external voltage transformer PT installed at the input end of the consumer's load 2.

A voltage and a current proportional to the load voltage and load current are input from the secondary sides of the current transformer CT and the current transformer CT, respectively. In this case, the transformation ratio of the potential transformer FT and current transformer CT is called a composite transformation ratio, and the transformation ratio of the potential transformer PT and the current transformer CT
It is expressed as the product of the current transformation ratio of .

The output of the voltage transformer PT and the output of the current transformer CT are manually input to the measuring section 3 shown in the block diagram of the power meter 1 with automatic output pulse width switching double-multiplying device in FIG.

FIG. 3 is a block diagram showing details of the measuring section 3. As shown in FIG.

As shown in FIG. 3, the output voltage V of the potential transformer PT, which is proportional to the load voltage, is connected to the output current I of the current transformer CT, which is proportional to the load current. are respectively input to the current transformer CT2 of the measuring section 3.

The outputs of the potential transformer PT2 and the current transformer CT2 are multiplied by a multiplier 4 and converted into a voltage value proportional to the load power, and then sent to a voltage-frequency converter 5 and a voltage comparator 6.
is man-powered.

The voltage-frequency converter 5 generates pulses with a frequency proportional to the load power. By integrating these pulses, a value proportional to the amount of electric power can be obtained. The number of pulses per unit electric energy is called the Cabal constant. For example, the pulse constant of the voltage-frequency converter 5 is 1,800.0 OOP/lJh, that is,
It takes a value like 500P/kWs.

The voltage comparator 6 is only for detecting reverse current,
In the case of a reverse current, the current phase rotation of the current transformer CT2 is opposite to that in the case of a positive current, and in this case, the output voltage of the multiplier 4 becomes negative, so this is detected by the voltage comparator 6, Output as a reverse current signal. These two signals are input manually to the microcomputer section 7.

And a power meter with output pulse width automatic switching type transmitter 1
In this case, the voltage and current (
Set the rated values of the input voltage and input current (input voltage and input current) of the measuring section 3, and use the set transformation ratio setting switch 9 to set the above-mentioned composite transformation ratio according to the standards of the external instrument transformer PT and current transformer CT to be used. Set a three-digit set metamorphic ratio divided by the multiplication factor,
The multiplication factor to be used (1°10
100, etc.) and set the output pulse weight magnification to 1/1.1/
10. Select 17 from 1/100, and these setting conditions are respectively input to the microcomputer section 7.

Pulse weight means that one output pulse is connected to the voltage transformer P.
It represents how many kWh actually corresponds to T and the primary side of the current transformer CT, and is expressed using the unit of kWh/P.

It is the reciprocal of the pulse constant (P/kWh).

In addition, the pulse output selection switch 12 allows the transmitter 1
Select the pulse output method in step 5.

That is, as for the output method, a relay contact output outputs a DC pulse by connecting and disconnecting a relay, and a photocoupler output has an isolated output via a photocoupler. In addition to this output, there is also a calibration pulse output.

Hh, kvarh, kVAh changeover switch 13 is used to set the measurement type of active energy, reactive energy, and apparent energy. (In the following explanation, it is assumed that 1 kWh of active power is measured.) The microcomputer section 7 calculates constants for each rating determined according to the voltage and current ratings set by the rating setting switch 8, and the set transformation ratio setting switch 9. The frequency division value of the input cavus is calculated from the set metamorphic ratio and the output pulse weight multiplier set by the pulse weight multiplier setting switch 11.

Further, the microcomputer section 7 has a built-in pulse counter, and the pulse counter counts the input pulses, and when the counted pulses match the frequency division value, one output pulse is transmitted.

Furthermore, the microcomputer section 7 also includes a measurement value counter that counts these output pulses.

Then, the display 14 displays operation display, load status display,
Electric energy meter 1 with output pulse width automatic switching type transmitter, including no-load display, measured value display, reverse current display, transmitted pulse display, kWh, kvarh, kVAh display, and multiplication factor display.
The operating status and load status of the unit are displayed.

Transmission device i! 15 is controlled by the microcomputer section 7 and outputs a pulse having a pulse width that meets the conditions set by the pulse weight magnification setting switch 11 in an output format selected by the pulse output selection switch 12.

Figure 4 shows watt-hour meter 1 with automatic output pulse width switching type transmitter.
FIG. 4 is a flowchart illustrating the automatic output pulse width switching operation of the microcomputer section 7, and an example of the automatic output pulse width switching operation of the microcomputer section 7 will be explained with reference to FIG.

As an example, a case will be described in which a three-phase three-wire system is used, with a rating of 110 V and 15 A, a set transformation ratio of 200, a multiplication factor of 1, and a pulse weighting factor of 1/l OO.

Assuming that the input caballus constant for the human caballus from the measurement unit 3 is 1.800.0OOP/kWh=500P/kWs, in the main routine of FIG. 4(a), when the setting conditions are determined in step 1, in step 2, The ratio of the output pulse constant to the human power pulse constant, that is, the frequency division value of the output pulse to the human power pulse is determined by setting a predetermined constant for each rating to 18.0 to give an appropriate frequency division value depending on the rating.
Assuming 00, dividing value = (18,000/200) x (100/
100) = 90. Note that the output pulse constant is now 20, Rolo OF/kWh.

In step 3, the rated power of a three-phase three-wire system with a 10V15A rating is 13x 11OVx 5A = 0.953kW, so the output pulse per hour at the rated load is 1,800.000 x O,953x (1/90)
x 19.060 pulses, and the human power range is rated at 1
．． Since up to 5 times is allowed, 19.060X1.5 = 28.590.

The pulse period in this case is 3600+ 28,590- 126m5, so
On time 120m5. It is determined that the off-time is 24m5 or more and the pulse period does not satisfy the regulation of 144+ns or more. Therefore, proceed from step 3 to step 7.

In step 7, if the pulse width is 60m5, the on-time is 60m5. Off time 12m5 or more, pulse period? 2ms
It is determined whether the above regulations are satisfied or not, but the pulse period is as calculated above! , 26a+s, so
On time 60m5. It is determined that the off time is 66Ills and satisfies the regulation.

As mentioned above, the pulse width is 120m5 and 601m5.
11s in advance, and by steps 3 and 7, turn on/off.
Determine the maximum pulse width that can ensure the off-time ratio.

In the above example, 60 IIls is determined to be the maximum pulse width. The functional part of the microcomputer unit 7 that performs steps 3 and 7 corresponds to the determining means of the present invention.

Every time a pulse is input from the measuring section 3, the input pulse interrupt routine shown in FIG. Then, the process returns to the main routine shown in FIG. 4(a). In step 8, when the count value of the pulse counter becomes equal to the frequency division value (=90), in step 9, the on-time is 60m5. One pulse with an off time of 12IIIs or more is sent to the transmitting device 15, and the transmitting device ft15 is made to output a transmitting pulse with a pulse width of 60 m5. At the same time, display] 4 to 60m
Display the transmission pulse number 5. In step IO, the pulse counter is reset. The pulse counter functions as a frequency divider, and every time 90 human pulses are counted, the microcomputer section 7 outputs one pulse ('!) from the transmitting device 15. The functional part of the computer section 7 corresponds to the pulse width control means of the present invention.

If the rating, set transformation ratio, and multiplication factor are the same as in the above case, and the pulse weight multiplier is set to 1/IQ, the frequency division value = (18,000/200) x (100/
10) = 900 and is calculated in step 2.

In step 3, the number of output pulses per hour when the load is three times the rated load is calculated to be 5.718 pulses, and the pulse period is calculated to be 63 buttons S.

Therefore, the on time is 120m5. It is determined that the off time is 510 m5 and satisfies the regulations, and the process proceeds to step 4. In step 4, the count value of the pulse counter becomes the frequency division value (・900)
When it becomes equal to , in step 5, the transmitting device 15 is controlled to output a transmitting pulse with a pulse width of 120 m5.

Incidentally, if any of the pulses 1111120m5.60m5 is invalid, an error is displayed on the display 14 in step 11.

In this way, it is possible to automatically output a transmission pulse with the most appropriate pulse width according to the set conditions.

In the flowchart of FIG. 4 explained above, the on-time of the output pulse is set to two types, 120a+s and 60m5, but the output pulse width can be further switched in multiple stages such as 30m5.15as, and As for the pulse width, any pulse width may be adopted.

In the case of Figure 4, even if the power is used up to 150% of the rated load at a pulse weight multiplier of 1/100 and up to 300% at a pulse weight multiplier of 1/1.1/10, the off time of the output pulse is the on time. However, since it is not always used near the rated load, Figure 5 shows an example in which the pulse width is changed according to the actual current load condition. Shown below.

In FIG. 5, steps 1 and 2 are the same as in FIG. 4, and the frequency division value is 90. When there is a human caballus,
In step 12, the count value of the pulse counter is +1.
At the same time, in step 13, the manual pulse frequency r is detected from the time interval with the previous pulse. In step 3, if the pulse weight magnification is 1/100, the input range is allowed up to 1.5 times, so the input pulse frequency r is multiplied by 1.5 and divided by the frequency division value. Calculate the number of output pulses per second. That is, by taking fxl, the frequency divided by 5,000, and the reciprocal of this (frequency divided value/1.5f), the pulse period can be obtained. For example, in the case of 1/2 of the rated load, the input pulse frequency is 19,060 x 90÷
2+ 3.600! =, 23B P/S, so
The output pulse period is 90/(238Xl, 5) = 252m5. This has an on time of 120 m5 and an off time of 132 m5.
Therefore, it is determined that the specification is satisfied. Therefore, the transmitting device 15 is configured to output a transmitted pulse with a pulse width of 120 m5.
control.

(Effects of the Invention) As described above, according to the present invention, the determining means determines the maximum pulse width among a plurality of predetermined pulse widths that can ensure the ratio of the on/off time of the output pulse. and a pulse width control means for controlling the transmitting device to transmit an output pulse having the pulse width determined by the discriminating means. If there is a high possibility that the cycle will become small, for example, if the ratio of the on/off time of the output pulse cannot be ensured with a pulse width of 120 m5, the pulse width will be automatically switched to 60 ms, so the output pulse It is possible to provide a watt-hour meter with an output pulse width automatic switching type transmitter that can always transmit a pulse with an optimal pulse width.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a power meter with an automatic output pulse width switching type transmitter, which is an embodiment of the present invention, and FIG. 2 is a block diagram of a power meter with an automatic output pulse width switching type transmitter in the power distribution system. The wiring diagram, Figure 3, is a block diagram showing the measurement section of the power meter with automatic output pulse width switching type transmitter, Figure 4.
FIG. 5 and FIG. 5 are flowcharts illustrating two examples of automatic output pulse switching operations of a power consumption meter with an automatic output pulse width switching type transmitting device. 131. Power meter with output pulse automatic switching type transmitter, 3
10. Measuring unit, 4110 multiplier, 5. . , voltage-frequency converter, 60. . Voltage comparator, 751.
Microcomputer Department, 811. Rating setting switch,
911. Setting transformation ratio setting switch, 10, Multiplication factor selection switch, 11. ,,Pulse weight magnification setting switch, 1
21. . Pulse output selection switch, 13. , ,
kWh, kvarh, kVAh changeover switch, 14.
,,Display device,15. , , Transmitter, PT, , Potential transformer, PT2. , , Potential transformer, CT, , , Current transformer, CT2. ,,Current transformer.

Claims (1)

[Claims] (1) A watt-hour meter with a transmitting device, comprising a transmitting device that transmits an output pulse with a frequency proportional to the measured electric power, and a pulse weighting factor setting means for setting a pulse weighting factor of the output pulse, which A determining means for determining the maximum pulse width that can ensure a ratio of on/off time of the output pulse among a plurality of predetermined pulse widths, and transmitting an output pulse having the pulse width determined by the determining means. A watt-hour meter with an output pulse width automatic switching type transmitting device, characterized in that a pulse width control means for controlling the transmitting device as described above is provided.