JP3871100B2 - Power monitoring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power monitoring apparatus for monitoring power consumption of a commercial frequency power supply used in a factory or a general household.
[0002]
[Prior art]
Conventionally, when the center collects measured power data, a dedicated communication line has been installed. FIG. 4 shows an example. In the figure, 1 is a power line, 2 is PT, 3 is CT, 4 and 5 are level converters, 6 is power measuring means, 7 is conversion means, 8 is a modulation device, 9 is a communication line, and level converter 4 5, the power measuring means 6, the converting means 7, and the modulating device 8 constitute a power monitoring device 10. FIG. 5 shows a case where the power monitoring apparatus 10 having these configurations is installed in the distribution system, and the data measured for each load 11 branched from the power line 1 is the controller at the center via the communication line 9. Sent to 12.
[0003]
[Problems to be solved by the invention]
As described above, conventionally, when data of measured power is transmitted, a communication line dedicated to data communication is required, and thus there is a problem that an installation cost and a maintenance cost of a signal line are excessive.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, as shown in FIG. 1, the invention according to claim 1 is a first method for level-converting the PT2 installed on the power line 1, the CT3 installed on the power line, and the output of the PT2. a level converter 4, and the second level converter 5 for level converting the output of the CT3, power to measure the power value using the output of the first level converter 4 and the second level converter 5 and measuring means 6, the converter 7 for converting the measured power value to the transmission data, modulates the transmission data is converted, a modulator 8 for inputting superimposed on the power line 1 through the PT2, the It is provided.
[0005]
Further , the invention according to claim 2 is the power monitoring device according to claim 1, wherein between the PT 2 and the first level converter 4 and between the CT 3 and the second level converter 5. As shown in FIG. 2, low-pass filters 13 and 14 are connected .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to FIG.
In this embodiment, a PT2 for drawing a voltage value from the power line 1 and a CT3 for drawing a current value are provided. Since the frequency of the power line 1 is as low as commercial frequencies of 50 Hz and 60 Hz, the signals of PT2 and CT3 are input to the level converters 4 and 5 via the low-pass filters 13 and 14, respectively. The characteristics of the low-pass filters 13 and 14 are appropriate so as to remove a high-frequency transmission signal (for example, 150 kHz) superimposed on the power line 1.
[0008]
The output of the level converter 4 is input to an AD converter built in the microcomputer 16. The level converters 4 and 5 are realized by operational amplifiers, and are adjusted so that the signals of PT2 and CT3 can be converted to a voltage range V _pp = 5 V that can be AD converted by the AD converter. Here, the power measuring means 6 is realized by an internal program of the microcomputer 16. That is, the instantaneous power can be calculated by multiplying the voltage and current values taken by the AD converter. The effective power value can be measured by averaging the instantaneous power for one cycle.
[0009]
The AD conversion timing is set to a constant period (for example, 10 kHz) by a timer function in the microcomputer 16. In order to take the average of the instantaneous power for one cycle, the number of samplings in one cycle is required. In order to obtain the number of samplings in one cycle, there are a method for obtaining the number of samplings between the zero-cross points of the signal (the point at which the sign of the AD converted value changes from “−” to “+”), and the frequency in advance because it is a commercial frequency. There is a method of determining the number of times of sampling because it is determined.
[0010]
In this embodiment, a case where a commercial frequency of 50 Hz is sampled at 10 kHz is taken as an example, and the number of samples in one cycle is 200 times. That is, in the case of this example, the effective power value can be obtained by calculating the sum of the calculated instantaneous power for 200 samples and dividing by 200. This calculated value is stored in a memory on the microcomputer 16 as a measured effective power value. Next, the effective power value stored in the memory is read, output as a transmission signal, and sent to the modulation circuit 17.
[0011]
The modulation circuit 17 modulates a transmission signal with a signal having a frequency higher than the commercial frequency (for example, 150 kHz), and a power line through a clamp diode 18 for protection, a limiter resistor 19 and a transformer (PT 2 in the figure). 1 superimposes the transmission signal. By sharing the transformer with PT2, the cost can be reduced.
[0012]
Next, the case where the measured power effective value is transmitted will be described with reference to the power monitoring system of FIG. In the figure, the power of each load 11 is monitored by polling each power monitoring device 10 from the controller 12 and requesting a measured value. Each power monitoring device 10 has an individual address such as # 0 to # 2, and when the controller 12 receives a data request for the address of its own station, the measured power effective value is transmitted. To do.
[0013]
Therefore, the transmission / reception selection signal in the microcomputer 16 of FIG. 2 is normally set to reception, and when a request is made for the address of the own station (reception signal input port), the transmission / reception selection signal Is switched to transmission. Then, effective power value data is transmitted from the transmission signal output port of the microcomputer 16. Here, a UART port built in the microcomputer 16 is used as the transmission signal output port and the reception signal input port.
[0014]
Further, the modulation circuit 17 can be easily realized by using an IC that realizes power line communication such as LM1893 manufactured by National Semiconductor, for example. In this case, for example, data can be transmitted by FSK modulation of 150 kHz, and communication can be performed at a transmission rate as low as about 360 baud.
[0015]
Therefore, in the present invention, when configuring a power monitoring device, by superimposing a transmission signal on the power line to be monitored, the communication line for transmitting the power data can be omitted, and the installation cost and maintenance cost of the communication line can be eliminated. The effect of being able to be obtained. Further, the transformer for superimposing the transmission signal also serves as a power measurement transformer, so that an effect of reducing the cost of the transformer can be obtained.
[0016]
【The invention's effect】
As described above, according to the present invention, since the power line is used as the communication line, there is an effect that the installation cost of the communication line and the maintenance cost of the communication line become unnecessary.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of the present invention.
FIG. 2 is a diagram showing an embodiment of the present invention.
FIG. 3 is a diagram showing an embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a conventional example.
FIG. 5 is a diagram illustrating a conventional example.
[Explanation of symbols]
1 Power line 2 PT
3 CT
4 1st level converter 5 2nd level converter 6 Electric power measurement means 7 Conversion means 8 Modulator
10 Power monitoring device
11 Load
12 Controller
13,14 Low-pass filter
16 Micro computer
17 Modulation circuit
18 Clamp diode
19 Limiter resistance

Claims (2)

PT installed on the power line,
And CT installed in the power line,
A first level converter for level converting the output of the PT;
A second level converter for level converting the output of the CT;
Power measuring means for measuring a power value using outputs of the first level converter and the second level converter;
Conversion means for converting the measured power value into transmission data;
Modulates transmission data is converted, a modulation device for inputting superimposed on the power line via the PT,
A power monitoring apparatus comprising: The power monitoring device according to claim 1,
Between the PT and the first level converter, and, between the CT and the second level converter, power monitoring apparatus characterized by connecting a low-pass filter.

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