JPH0259483B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an automatic power factor control device that controls turning on and off of a capacitor installed in a power consumer for improving the power factor.

Automatic power factor control devices turn on or turn off capacitors in order to appropriately compensate for delayed reactive power generated by loads, and are increasingly being used by large customers such as factories. ing. In conventional automatic power factor control devices, the power frequency was manually set to match the commercial frequency at the installation location. Therefore, if you forget to set the power supply frequency at the time of initial operation, there is a risk that normal operation will not be performed.

The purpose of the present invention is to solve the above-mentioned problems and provide an automatic power factor control device that can automatically set the power frequency to match the commercial frequency of the installation location at the time of initial operation, and can also check the sensor at the same time. It is to provide.

In order to achieve this object, the present invention includes a sensor that detects a voltage signal representing a load voltage and a current signal representing a load current, and includes a voltage sensor unit that converts the voltage signal into a rectangular wave. When the measured value matches one of the commercial frequencies, the power frequency is set to that commercial frequency, and when the measured value does not match any of the commercial frequencies, a sensor error display is commanded. The present invention is characterized in that it is provided with a frequency determining means for determining a frequency, and a sensor abnormality display means for displaying a sensor abnormality according to a command from the frequency determining means.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a circuit diagram showing a typical installation example of an automatic power factor control device. A transaction meter current transformer 2 is connected to the distribution line 1, and further connected to a management meter transformer 5 via a disconnector 3 and a main disconnector 4. The load (not shown) is the branch breaker 6 to 8.
and are connected via transformers 9-11. Capacitors 12 to 14 for power factor improvement are connected to switches 15 to 17.
and are connected via series reactors 18-20. Discharge resistor 2 in parallel with capacitors 12 to 14
1 to 23 are connected. The input side of the automatic power factor control device 24 is connected to the management instrument transformer 5,
Its output side is connected to a controller 25. Controller 2
5 drives the switches 15 to 17 to open and close, and the output means of the automatic power factor control device 24 directly drives the switches 15 to 17.
It is not necessary if 5 to 17 can be controlled.

FIG. 2 shows a front panel 27 of an automatic power factor control device 26, which is one embodiment of the present invention. 28~
31 is the reactive power on the lag side, the lag side in the appropriate range,
The control status indicator light 32 lights up when the sensor is on the advance side and the forward side of the appropriate range, and simultaneously lights up to indicate sensor abnormality during initial operation, and 32 is set to either automatic mode, manual mode, or test mode. Mode setting switches 33 to 35 are provided for each capacitor, and an indicator light that lights up when the capacitor is turned on.
36 to 38 are manual switches that turn on and off capacitors, 39 to 41 are capacitor capacities (unit:
This is a capacitor capacity setting device that sets the VA).

As shown in FIG. 3, the main part of the automatic power factor control device 26 is composed of a central processing unit 42. The configuration of the central processing unit 42 is equivalently represented by its functional blocks a to h. The automatic power factor control device 26 includes a voltage transformer 43 and a current transformer 44, which are connected to the management voltage transformer 5. The sensor 45 receives a voltage signal (fourth
The voltage sensor section 45A converts the voltage signal (Fig. The current sensor section 45B detects the zero-crossing point of the current signal. An output relay 46 is provided for each capacitor.

First, when the power switch (not shown) is turned on for the first time after installation, the frequency determination program shown in FIG. 5 is executed. Voltage sensor section 45
At A, the voltage signal V (FIG. 4) is converted into a rectangular wave P and output to the central processing unit 42. In general, the commercial frequency of power systems is very stable, and the deviation per cycle is said to be about ±0.2Hz. Converting this deviation into time is ±80μS
(50Hz), ±55μS (60Hz), and can be treated as a stable signal source. Therefore, the half wavelength of the rectangular wave P is measured in block a, and if it is within the 50Hz specified value, the power supply frequency is set to 50Hz, and 60Hz is set.
If it is within the specified value, the power supply frequency will be set to 60Hz. When the measured value does not match any specified value, it is determined that the sensor 45 is abnormal, and all the control status indicator lights 28 to 31 are turned on at the same time.
Thereby, at the time of initial operation, automatic setting of the power supply frequency and checking of the sensor 45 are performed simultaneously.

In block b, timekeeping is performed by using the power supply frequency as a clock pulse.

To explain the operation when the automatic mode is set by the mode setting switch 32, execution of automatic control processing is instructed in block c of FIG. The automatic control process is performed as shown in the flowchart of FIG. Current sensor section 45B of sensor 45
For example, a current value is output every second, and the central processing unit 42 calculates the average value (effective value) of the current value over several tens of seconds. The phase difference is detected in the central processing unit 42 based on the zero cross point outputted every cycle of the power supply frequency from the voltage sensor section 45A and current sensor section 45B of the sensor 45, and the average value over several tens of seconds is simultaneously calculated. be done. These are block d in Figure 3.
corresponds to The load voltage is treated as a constant that does not vary, and the reactive power is calculated from the current value and the phase difference. This calculation requires only a few cycles of the power supply frequency and corresponds to block e in FIG. In block f, a load current pattern for one or two days is created by storing current values, and day and night are divided according to the load current pattern. In block g, different appropriate ranges are set for day and night. If the calculated reactive power is within the set appropriate daytime range or nighttime range, it is determined that it is unnecessary to turn on and off the capacitor, and the output relay 46 is energized and
The de-energized state is maintained as it is. If the reactive power is out of the appropriate daytime range or nighttime range, it is determined that it is necessary to turn on or turn off the capacitor, and the output relay corresponding to the capacitor in the order to be turned on or turned off is energized. or de-energized. This stage corresponds to block h in Figure 3,
For example, it ends in about 10 cycles of the power supply frequency. As a result, if the reactive power falls within the appropriate range, the control status indicator light 29 or 30 lights up.

In the illustrated embodiment, the control status indicator lamp is also used as the sensor abnormality display means, but the sensor abnormality display means may be provided separately.

As described above, according to the present invention, a sensor that detects a voltage signal representing a load voltage and a current signal representing a load current is provided with a voltage sensor unit that converts the voltage signal into a rectangular wave, and the sensor detects the voltage signal representing the load voltage and the current signal representing the load current. When the measured value matches one of the commercial frequencies, the power frequency is set to that commercial frequency, and when the measured value does not match any of the commercial frequencies, a sensor error display is commanded. Since we have provided a frequency determination means for determining the frequency of the sensor and a sensor abnormality display means for indicating the sensor abnormality based on the command from the frequency determination means, the power supply frequency can be automatically set to match the commercial frequency of the installation location at the time of initial operation, and at the same time the sensor A check can be performed.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a typical installation example of an automatic power factor control device, Fig. 2 is a front view showing a front panel of an embodiment of the present invention, Fig. 3 is a block diagram, and Fig. 4 is a circuit diagram showing a typical installation example of an automatic power factor control device. a waveform diagram showing a voltage signal and a square wave;
FIG. 5 is a flowchart of the frequency determination program, and FIG. 6 is a flowchart of the automatic control processing program. 12-14... Capacitor, 15-17... Switch, 26... Automatic power factor control device, 28-31...
...Control status indicator light, 42...Central processing unit, 45...Sensor, 45A...Voltage sensor unit,
a~h...Function block, V...Voltage signal, P...
...Square wave.

Claims (1)

[Claims] 1. In an automatic power factor control device equipped with a sensor that detects a voltage signal representing a load voltage and a current signal representing a load current, the sensor is provided with a voltage sensor unit that converts the voltage signal into a rectangular wave, Measures the wavelength of the wave, and when the measured value matches one of the commercial frequencies, sets the power frequency to that commercial frequency, and displays a sensor abnormality display when the measured value does not match any of the commercial frequencies. An automatic power factor control device comprising a frequency determining means for issuing a command, and a sensor abnormality display means for displaying a sensor abnormality according to a command from the frequency determining means.