JPH0259484B2 - - 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 provided for improving the power factor in a power consumer.

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 such an automatic power factor control device, it is common to check each part upon initial operation. Conventionally, checking a sensor requires an inspection device, which is troublesome.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an automatic power factor control device that can automatically check the sensor during initial operation.

To achieve this objective, the present invention provides a sensor for detecting a voltage signal representing a load voltage and a current signal representing a load current, including a first square wave converter for converting the voltage signal into a square wave, and a first square wave converter for converting the voltage signal into a square wave; It is equipped with a second rectangular wave converter that converts the signal into a rectangular wave, and a frequency converter that converts the current signal into a frequency, and upon initial operation, the current signal is transferred to the second rectangular wave converter and the frequency converter. A switching means for inputting a voltage signal instead, and a sensor abnormality display when the outputs of the first rectangular wave converter, the second rectangular wave converter, and the frequency converter to which the voltage signal is input deviate from their respective specified values. The present invention is characterized in that it is provided with a sensor check means for commanding the sensor check means, and a sensor abnormality display means for displaying a sensor abnormality according to a command from the sensor check 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 32 lights up when the sensor is on the advance side or the advance side of the appropriate range, and also lights up to indicate sensor abnormality during initial operation.The control status indicator 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 36 lights up when the capacitor is turned on.
~38 are manual switches that turn on and off the capacitors, and 39~41 are the 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 detects the zero-crossing point and current value of a voltage signal representing the load voltage input from the potential transformer 43 and a current signal representing the load current input from the current transformer 45. An output relay 46 is provided for each capacitor.

Details of the sensor 45 are shown in FIG. A first square wave converter 47 is connected to the instrument transformer 43 .
A current-voltage converter 48 is connected to the current transformer 44, and its output side is connected to a frequency converter 49 and a second rectangular wave converter 50 via a contact A of a changeover switch S. The changeover switch S normally closes to the contact A side, and upon initial operation, closes to the contact B side by a switching signal sent from the central processing unit 42, and converts the frequency converter 49 and the second square wave converter 50 into an instrument transformer. It is connected to the device 43 by switching. _t1 to _t4
is a connection terminal to the central processing unit 42.

First, when the power switch (not shown) is turned on for the first time after installation, the frequency determination and sensor check programs shown in FIG. 5 are executed. When the switching signal is sent from the central processing unit 42 to the sensor 45 and the switching switch S is closed to the contact B side, the voltage signal V output from the instrument transformer 43 is transferred to the first rectangular wave converter 47. The second rectangular wave converter 50 converts the rectangular wave Pv and the rectangular wave Pi shown in FIG. It is sent to the central processing unit 42 via t ₂ to _{t 4} .

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, in block a, the half wavelengths Tv and Ti of the rectangular wave Pv and the rectangular wave Pi are measured, respectively. If these measurements are within the 50Hz specification, the power frequency is set to 50Hz and 60Hz.
If it is within the Hz specified value, the power supply frequency will be set to 60Hz. When the measured value of the half-wavelength Tv does not match any of the specified values, it is determined that the first square wave converter 47 is abnormal, and the delay side control status indicator lights 28 to
31 is turned on. When the measured value of the half wavelength Ti does not match any of the specified values, it is determined that the second rectangular wave converter 50 is abnormal, and the control status indicator light 29 on the delayed side of the appropriate range is turned on. Next, it is checked whether the phase difference between the rectangular wave Pv and the rectangular wave Pi is within a specified value close to zero, and if it is outside the specified value, the first rectangular wave converter 47 or the second rectangular wave converter 50 is It is determined that there is an abnormality, and the control status indicator lights 28 and 29 are turned on at the same time. Furthermore, it is checked whether the output of the frequency converter 49 is within the specified value, and if it is out of the specified value, it is determined that the frequency converter 49 is abnormal, and the control status indicator light 30 on the advance side of the appropriate range is turned on. let Finally, close the changeover switch S to the contact A side, and switch the instrument transformer 43 of the sensor 45.
and check the wiring to current transformer 44. If the wiring is normal, the rectangular wave of the first rectangular wave converter 47 rises between the rectangular waves of the second rectangular wave converter 50, so watch the rise of both rectangular waves, and if there is a wiring error, check the leading side. The control status indicator light 31 is turned on. Through the operations described above, during initial operation, automatic setting of the power supply frequency and automatic checking of the sensor 45 are simultaneously performed.

It should be noted that since the current-voltage converter 48 rarely experiences failures, checking is omitted in this embodiment.

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. A current value is detected by counting the frequency output from the frequency converter 49 of the sensor 45 for one second, for example, and then an average value (effective value) of this current value over several tens of seconds is calculated.
The phase difference is detected in the central processing unit 42 based on the zero-crossing point of the rectangular wave output from the first rectangular wave converter 47 and the second rectangular wave converter 50 of the sensor 45 for each cycle of the power supply frequency, Similarly, the average value over several tens of seconds is calculated.
These correspond to block d in FIG. 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 or off the capacitor, and the energized or de-energized state of the output relay 46 is maintained as it is. be done. 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, and for example,
It completes in about 10 cycles. 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 light 28
31 are also used as sensor abnormality display means, but sensor abnormality display means may also be provided separately. Further, the changeover switch S corresponding to the changeover means of the present invention does not necessarily need to be provided inside the sensor 45 as shown in FIG.

As explained 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 includes a first rectangular wave converter that converts the voltage signal into a rectangular wave, and a first rectangular wave converter that converts the voltage signal into a rectangular wave; It is equipped with a second rectangular wave converter that converts the signal into a rectangular wave, and a frequency converter that converts the current signal into a frequency, and upon initial operation, the current signal is transferred to the second rectangular wave converter and the frequency converter. A switching means for inputting a voltage signal instead, and a sensor abnormality display when the outputs of the first rectangular wave converter, the second rectangular wave converter, and the frequency converter to which the voltage signal is input deviate from their respective specified values. Since the sensor check means for commanding the sensor check means and the sensor abnormality display means for displaying the sensor abnormality according to the command from the sensor check means are provided, it is possible to automatically check the sensor at the time of initial operation.

[Brief explanation of the drawing]

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 circuit diagram showing an example of a sensor according to an embodiment of the present invention, FIG. 5 is a flowchart of a frequency determination and sensor check program, FIG. 6 is a waveform diagram showing a voltage signal and a rectangular wave, and FIG. 7 is an automatic control This is a flowchart of a 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, 47 ... First square wave converter, 49 ... Frequency converter, 50 ... Second square wave converter, a to h ...Function block, S...Selector switch, V...Voltage signal, Pv, Pi...Square wave.

Claims (1)

[Claims] 1. 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, wherein the sensor includes a first rectangular wave converter that converts the voltage signal into a rectangular wave; It is equipped with a second rectangular wave converter that converts a current signal into a rectangular wave, and a frequency converter that converts the current signal into a frequency, and upon initial operation, the current signal is transmitted to the second rectangular wave converter and the frequency converter. a switching means for inputting a voltage signal instead of the voltage signal; and when the outputs of the first rectangular wave converter, the second rectangular wave converter, and the frequency converter to which the voltage signal is inputted deviate from their respective specified values,
An automatic power factor control device comprising: a sensor check means for commanding a sensor abnormality display; and a sensor abnormality display means for displaying a sensor abnormality according to a command from the sensor check means.