JPS5948659A - Multiplexing measuring apparatus of electric circuit - Google Patents

Abstract

PURPOSE:To enable the calculation of various electric amounts, by applying operation treatment to the measured value stored in a memory apparatus connected to the A/D converter of a sampling circuit for measuring instantaneous values of the voltage and the current of an electric circuit. CONSTITUTION:When the memory program of the memory part 10 of a central operation treatment apparatus 5 is started, instantaneous data intake treatment is selected. When this treatment is finished, the calculations of active power P and reactive power Q are performed. The signals exhibiting the calculated powers P, Q are stored in the predetermined address in the memory part 10. Thereafter, the calculation treatments of a voltage effective value V and a current effective value I are performed. The signals exhibiting the calculated effective values V, I are stored in the predetermined address in the memory part 10. In the next step, the calculation treatments of frequency (f) and a phase angle theta are performed. The frequency (f) and the phase angle theta subjected to averaging treatment are stored in the predetemined address in the memory 10. In the stage of the next data output, calculated various electrical amounts are sent out of a multiplexing measuring apparatus as an output signal S.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multiplex measuring device for electrical circuits, and in particular, for measuring electrical quantities such as voltage, current, active power, reactive power, frequency, and phase angle of single-phase or three-phase AC power equipment. This invention relates to a multiplex measurement device that performs measurements and calculations.

Here, the term "electrical path" refers to all or part of a circuit through which electricity is conducted.

Conventionally, active power and reactive power of AC power transmission lines, etc.

To measure frequency, phase difference, etc., measure the output of the instrument transformer and current transformer using a wattmeter and a reactive current (1), respectively.
Hey ^^ The wattmeter was connected to the frequency meter and phase meter. This conventional method requires (1) dedicated lead wires for each measurement element, which makes wiring work troublesome, and (2)) input to the instrument for each measurement element, which requires conversion to instrumentation. (2) Analog type meters cause errors due to temperature characteristics and linearity. Easy to understand: When using a filter to remove the effects of harmonics, etc., it is necessary to adjust the capacitors and resistors on-site to adjust the time constant, etc., and it is difficult to completely remove ripples. There were drawbacks such as:

It is therefore an object of the present invention to overcome the above-mentioned drawbacks of the prior art. To achieve this objective, the electrical circuit multiplexing measuring device according to the present invention digitally converts the instantaneous values of the voltage and current of the electrical circuit and stores it in a storage device, and uses these digital values to calculate the effective values of the voltage and current. , calculate active/reactive power, frequency, phase angle, etc. according to the definition. This calculation uses arithmetic means such as a microprocessor. The application of the multiplex measurement device according to (2) of the present invention is not limited to only AC circuits, but can also be used for multiplex measurement of DC circuits by connecting it to the output of an instrument transducer, etc. of a DC circuit. You can also do it.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 1st
In one embodiment of the present invention shown in the figure, the circuit multiplexing measurement device 1 includes an input transformer that transforms inputs 7 from a potential transformer PT, a current transformer OT, etc. to a voltage suitable for processing by an electronic circuit. a microprocessor that performs arithmetic processing on the signals from the transformer circuit TiO2, the analog manual conversion circuit AlO3 and the frequency input conversion circuit FIO4 connected to the output side of the transformer circuit 2, and the circuits 3 and 4 to generate an output signal S. Or it has a central processing unit 5. The illustrated central processing unit 5 includes a control calculation section 9 and a storage section 10 . The analog input conversion circuit 3 illustrated in FIG. 2 has three elements, namely, a sample hold 6, a multiplexer 7, and an analog/digital conversion circuit 8, which operate under the control of the central processing unit 50 control calculation section 9. For example, the sample hold 6 performs PT in response to a signal from the control calculation section 9.
The input signal from the OT and the input transformer circuit 2 is sampled at an appropriate frequency, for example, 8 times per cycle. The multiplexer 7 sequentially converts the output of the sample hold 6 into signals and applies them to the analog-to-digital conversion circuit 8. The output signal of the analog-to-digital conversion circuit 8 is a digital signal representing voltage and current, and is stored at an address in the storage section 10 designated by the control calculation section 9.

The calculation processing for the digital measurement values stored in the storage unit 10 will be explained with reference to the flowchart of FIG. When the program stored in the storage unit 10 of the central processing unit 5 is started at block ``beginning'', the program switch indicated by block 11 first selects the instantaneous data acquisition process indicated by block 12. This instantaneous data acquisition process is the process already explained with reference to FIG. When this process is completed, the program advances to logical decision block 11α, but since the process is not completed at this stage, program switch 1
1 to block 13, active power P and reactive power Q
Calculate.

In the illustrated embodiment, the active power P is calculated from the measured instantaneous values of the voltage and current of the three-phase circuit using the dual force meter method using the following equation.

P4= PI3 X If 10P3□xI3 here, P
I3 is the instantaneous voltage value between wires 1 and 2 of the three-phase three-wire line, P3
2 is a signal that indicates the instantaneous value of the voltage between wires 3 and 2, ■1 is the instantaneous value of the current on wire 1, and ■3 is the signal that indicates the instantaneous value of the current on wire 3, and n indicates the order of the samples as a serial number. In the subscript, n from 1 to 8 indicates the measured value of the first cycle.
6 to 6 indicate the measured values of the second cycle, and so on, and K1 is a constant determined by the sampling frequency, the number of cycles included in the calculation of equation (1), and the required output scale.

The above equation (1) indicates the effective power P obtained by performing averaging processing over 16 cycles twice on the instantaneous power value calculated by the dual force meter method.

It is known that the reactive power Q can be obtained by suitably phase-shifting the instantaneous values of voltage and current and then performing arithmetic processing according to equation (1).

Block 14 in FIG. 3 represents the averaging processing part in equation (1), and the active power P and reactive power Q calculated in this way.
A signal representing the value is stored at a predetermined address in the storage section 10 of the central processing unit 5.

After that, the program proceeds to the judgment block 11α again, but since the processing is not completed, the program switch 11 is switched to block 15, and the effective voltage value ■ and the effective current value ■
Proceed to the calculation process.

In the illustrated embodiment, the effective voltage value ■ is calculated using the following equation.

■i: P12×P12 Here, K2 is a constant determined by the sampling frequency, the number of cycles included in the calculation of equation (2), and the required output scale.

The above equation (2) indicates a value obtained by averaging the effective voltage value twice over 16 cycles according to the definition.

The effective value of the current is (2) with respect to the instantaneous value of the measured current.
) can be obtained by performing arithmetic processing according to the formula.

Block 16 in FIG. 3 represents the averaging processing part in equation (2), and the signals representing the voltage effective value ■ and current effective value ■ thus calculated are stored at a predetermined address in the storage unit 10 of the central processing unit 5. is stored in

After processing block 16, the program returns to decision block 1.
1α, but since the process is not completed, the program switch 11 is switched to block 17 and the process proceeds to calculation of the frequency f and phase angle θ.

The frequency f is determined by, for example, measuring the period T of the voltage by counting clock pulses in the frequency input conversion circuit 4 shown in FIG. It is obtained by calculating the reciprocal 1/T. Therefore, the frequency f can be calculated r times in one cycle.

The phase angle θ is determined by adding the voltages of different lines to the frequency input conversion circuit FIO shown in FIG. It can be calculated by comparing it with the cycle measurement value T described in 1. using a processing program.

Block 18 in FIG. 3 shows a process of averaging the frequency f and phase angle θ thus calculated over, for example, 16 cycles. The averaged frequency f and phase angle θ are stored at a predetermined address in the storage device 10 of the central processing unit 5.

After processing block 18 4, the program judges decision block 1
The process proceeds to step 1α, but since the processing is not completed, the program switch 11 is switched to block 19 and the process proceeds to data output.

At the data output stage, the active power P, reactive power Q, voltage effective value ■, current effective value, frequency f, phase angle θ, etc. calculated by the above processing are sent to the output signal S shown in FIGS. 1 and 2. It is sent out from the multiplexed measuring device l as a.

After sending the data, the program executes the logic judgment block 11α
When the program advances to ``End'', the process is completed, so the program switch 11 is set to the block 12 position, and the process proceeds to ``End''. Thereafter, if the program is started after a predetermined period of time, the above calculation will be repeated.

As shown in the calculations above, the input elements P12, P32, necessary for each calculation of active/reactive power, effective voltage, frequency, and phase,
The input element I0.13 required for each calculation of active power, reactive power, and effective current can be shared.

The present invention is not limited to the above embodiments; for example, it is possible to take in the voltage and current of a DC circuit, the voltage and current of a sirinuta circuit, etc. as the input signal (7).
It is also possible to calculate DC power, voltage/current distortion factor, firing angle, etc. as the output signal S. It is also possible to sequentially send out the output signals without storing them according to the calculations.

The effects of the present invention are listed below.

(1) Calculations of electrical quantities by the central processing unit are performed according to theoretical formulas using digital signals, so calculation errors are extremely small.

(2) All possible processing can be performed on the information contained in the input. That is, the maximum possible output information can be obtained with the minimum input information.

(3) Dedicated measuring instruments such as a wattmeter, reactive wattmeter, power factor meter, phase meter, voltmeter/ammeter with effective value display can be omitted.

(4) High-speed conversion is possible because alternating current ripples can be removed in one cycle.

(5) Since digital signals are output, it is convenient for automatic control and transmission.

(6) It is possible to multiplex and process inputs from a large number of electrical circuits, etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of an input analog circuit, and FIG. 3 is a flowchart of a program for arithmetic processing. 1...Multiple measurement device, 2...Heka transformer circuit,
3... Analog input conversion circuit, 4... Frequency input conversion circuit, 5... Central processing unit, 6... Sample hold, 7... Multiplexer, 8.
...Analog-digital converter, 9...Control calculation section. 10...Storage section. Patent applicant Okura Electric Co., Ltd. Patent application agent Tsugube Ichitoshin (11) Figure 2

Claims (1)

[Claims] a sampling circuit that measures instantaneous values of voltage and current in an electric circuit; a storage device connected to the sampling circuit via an analog-to-digital converter; and a computer that performs arithmetic processing on the measured values stored in the storage device A multiplex measurement device for electric circuits, which is equipped with arithmetic means for calculating various electrical quantities of electric circuits.