JP2002022792A - Withstand voltage testing device for insulating oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve responsiveness for desired voltage and improve precision, resolution, linearity and maintenance by replacing with a voltage regulator and a voltmeter device with electronic ones. SOLUTION: A switching power supply device 20 by which a voltage to be applied to the primary side of a step-up transformer 6 is formed detects an output error between the output of a switching power supply and the output of a sawtooth wave generation part 24 with a comparator 25 and outputs the detection signal to a PWM control part 22, whereby it controls the output voltage of a switching part 21 to increase in accordance with the increasing pattern of a sawtooth wave. A peak value for a switching output voltage is detected and held by a peak hold detector 31. The peak value is displayed on a digital display 32. When dielectric breakdown occurs in an insulating oil 2, an OCR 41 detects its condition to stop the operation of the switching power supply device 20 and print out a dielectric breakdown voltage with a printer 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a withstand voltage test apparatus for insulating oil used in transformers and the like.

[0001]

2. Description of the Related Art FIG. 1 is a block diagram of a conventional insulation oil withstand voltage test apparatus.

An insulating oil 2 to be measured is poured into an insulating oil cup (hereinafter referred to as an oil cup) 1.
In this state, a voltage sequentially boosted from 0 to 60 kv is applied to the spherical electrodes 3 set at a predetermined interval in the oil cup 1, and a voltage at the time when insulation breakdown occurs is measured as a breakdown voltage. . The boosting at this time is performed by the following configuration.

The voltage of the commercial power supply 4 is input to the primary side of a step-up transformer 6 via a voltage regulator 5, and a slide transformer of the voltage regulator 5 is driven by a motor 7. The voltmeter 8 is a pointer-type voltmeter having two needles (a meter needle and a measurement pointer). The two hands operate simultaneously until the voltage reaches the breakdown voltage, and when the voltage reaches the breakdown voltage, the measurement pointer is used. And the meter hand returns to zero. A resistor 9 for limiting overcurrent is connected in series with the electrode 3 on the secondary side of the step-up transformer 6.

With the above configuration, when the power switch 10 is turned on and the motor 7 is driven, the slide transformer of the voltage regulator 5 operates continuously, and the secondary output voltage V of the step-up transformer 6 is accordingly adjusted. Increases from 0v to 60kv. During this time, if the measured insulating oil 2 causes dielectric breakdown,
The circuit breaker 11 on the primary side of the step-up transformer 6 operates quickly to cut off the circuit. At this time, the measuring pointer of the voltmeter 8 indicates the value of the dielectric breakdown voltage. When performing the second test, the measuring pointer of the voltmeter 8 and the voltage regulator 5 are returned to zero, and the motor 7 is driven again to operate the slide transformer.

[0005]

However, the above-mentioned insulation oil withstand voltage test apparatus has the following disadvantages.

(1) Since the motor 7 is rotated to operate the slide transformer, the response for obtaining a desired voltage is not good.

(2) Since the pressure is increased by mechanical sliding of the slide transformer, accuracy, resolution, linearity, and maintainability are poor.

(3) Since the zero adjustment of the voltage adjusting device 5 and the voltmeter 8 is mechanical, it must be performed manually. In addition, it is necessary to return to zero for each test, and a measurement error occurs if this is neglected.

(4) The dielectric breakdown voltage indicated by the voltmeter 8 must be visually recorded each time. Skill is required because such zero point adjustment and visual observation each time are required for each test.

(5) Since the voltmeter 8 has two hands, the structure is complicated, and the voltmeter 8 is easily broken in a portable type.

An object of the present invention is to replace the voltage regulator 5 and the voltmeter 8 with electronic devices.
It is an object of the present invention to provide an insulating oil withstand voltage test device capable of eliminating the above-mentioned disadvantages.

[0012]

The present invention has the following arrangement to solve the above-mentioned problems.

(1) An insulating oil cup in which an insulating oil to be measured is injected and a measuring electrode is disposed therein, and a transformer for applying a high voltage to the measuring electrode, the primary of the transformer. A voltage applied to the primary side of a transformer is formed by a switching power supply output in an insulating oil withstand voltage test device that sequentially increases a voltage applied to a side and detects a voltage when the insulating oil breaks down as a dielectric breakdown voltage. Then, an error output between the output and the sawtooth signal is fed back to the switching power supply control unit to continuously increase the switching power supply output, and a switching power supply output peak value is held and displayed. A digital display; and a load current detector for detecting a load current of a switching power supply output, wherein the switching power supply device detects the load current detector. There when it becomes a certain level or more, characterized by stopping the operation of the switching power supply device.

In this configuration, an error output between the input voltage to the primary side of the transformer and the sawtooth signal is fed back to the switching power supply control section to obtain a switching power supply output, which is used as the input voltage on the primary side of the transformer. Therefore, the response is extremely good, and the applied voltage on the primary side of the transformer rises so as to almost completely match the slope of the sawtooth signal. For this reason, the rising pattern of the voltage on the secondary side of the transformer can be an arbitrary pattern by selecting or changing the shape of the sawtooth wave.

Also, by using a digital display for holding the peak value of the output of the switching power supply,
The correct dielectric breakdown voltage can be stored without causing a visual error.

The operation of the switching power supply is automatically stopped when the detected value of the load current detector becomes equal to or more than a predetermined value. In this case, a structure like a conventional circuit breaker is not required. Therefore, the configuration is simple.

(2) An openable and closable cover for covering the opening of the insulating oil cup, and a protection switch for outputting an operation stop signal of the switching power supply when the cover does not cover the opening. Have.

According to the present invention, when the cover is open, the protection switch does not operate the switching power supply, so that the safety can be improved.

[0019]

FIG. 2 is a block diagram showing an insulating oil withstand voltage test apparatus according to an embodiment of the present invention.

The switching power supply device 20 includes a switching unit 21, a PWM control unit 22, and an output voltage detection unit 23.
And a saw-tooth wave generator 24 and a comparator 25.
The switching unit 21 converts the AC voltage into a DC voltage.
An output voltage detecting unit 23 detects an effective value of the output voltage, and a saw-tooth wave generating unit 24 generates a saw-tooth wave. . The comparator 25 compares the output voltage of the switching unit 21 with the sawtooth wave of the sawtooth wave generation unit 24,
The error output is output to the PWM control unit 22. The PWM control unit 22 outputs a PWM signal corresponding to the output of the comparator 25 to the switching unit 21, whereby the output voltage of the switching unit 21 increases along the sawtooth wave.

A variable resistor 26 is connected to the saw-tooth wave generator 24 for changing the shape of the saw-tooth wave including its inclination. By adjusting the variable resistor 26, the slope of the sawtooth wave, that is, the output voltage rising speed of the switching unit 21 can be freely set.

The output voltage of the switching power supply 20 is P
The voltage is stepped down by a T (transformer) 30 and a peak hold detector 31 holds the peak value of the voltage. The peak value of the peak held is displayed on the digital display 32. Note that the peak hold detector 31 is not the actual high voltage on the secondary side of the step-up transformer 6 but the PT (transformer) 3.
0, the stepped down voltage is detected.
2 indicates a value obtained by multiplying the peak-held value by the winding ratio between the PT (transformer) 30 and the step-up transformer 6, and the displayed value matches the voltage on the secondary side of the step-up transformer 6. Like that. Reference numeral 41 denotes a current detector (OCR) connected in series to the primary side of the step-up transformer 6. When a current value equal to or higher than a predetermined value is detected, it is determined that insulation breakdown of the insulating oil 2 has occurred. A signal is output to the device 20 and the printer 33. Upon receiving this signal, the switching power supply device 20 stops operating and sets the switching output to zero. When the printer 33 receives the signal, it prints the voltage value displayed on the digital display 32. At this time, the voltage value displayed on the digital display 32 is the dielectric breakdown voltage.

Reference numeral 40 denotes a reset switch, and reference numeral 42 denotes a start switch. When the start switch is pressed after the reset switch 40 is pressed, the test starts. That is, the display of the digital display 32 is reset, and the operation of the switching power supply device 20 is started.

The oil cup 1 is provided with an openable / closable cover 50 for covering the upper opening thereof.
Protection switch 5 that turns on when 0 does not cover the opening
1 is attached. When the protection switch 51 is on, the switching power supply 20 is stopped. Therefore, with the cover 50 closed,
When the start switch 42 is pressed, the test starts. However, the test does not start when the start switch 42 is pressed while the cover 50 is open. Thereby, it is possible to prevent a dangerous state in which the opening of the oil cup 1 is exposed while the high voltage is applied to the electrode 3.

By manipulating the variable resistor 26 connected to the sawtooth wave generator 24, the waveform of the sawtooth wave can be changed. It is also possible to store the sawtooth wave of the shape and to select any one of them by the operation element.

Next, the operation of the above device will be described with reference to FIG. FIG. 3 is a flowchart showing the operation of the entire apparatus.

After the connection of the power supply / control cable, etc. is completed,
When the insulating oil 2 to be measured as a sample is set in the oil cup 1 (steps 100 and 101), the cover 50 is manually closed (step 102). continue,
When the power switch 10 is turned on and the power is turned on (step 103), a test is possible. When the start switch 42 is pressed after the reset switch 40 is pressed, the test starts (steps 104 and 105).
The switching power supply 20 starts operating, and its switching output voltage continuously increases. When the insulation breakdown occurs in the insulating oil 2 when the voltage rises to a certain voltage,
The OCR 41 detects a sudden rise in the current and sends a signal to the switching power supply device 20 and the printer 33. In addition,
The digital display 32 continuously displays the voltage applied between the electrodes 3 while updating the display value until this time. Upon receiving the signal from the OCR 41, the switching power supply device 20 stops the switching operation and makes the output voltage zero. At this time, since the peak hold detector 31 holds the peak value immediately before that, the display data of the digital display 32 indicates the breakdown voltage. Further, the output from the OCR 41 allows the printer 3
3 prints the breakdown voltage displayed on the digital display 32.

With the above operation, one test is completed, the breakdown voltage is printed on the printer 33, and the breakdown voltage is displayed on the digital display 32 (steps 106 to 108). When performing the second test, the cover 50 is opened (Step 120), and the sample (insulating oil 2) is gently stirred with a glass rod or the like to remove foreign substances such as soot adhering to the electrode surface. After confirming that there are no air bubbles (Steps 121 and 122), the cover 50 is closed (Step 123), and Step 104 and the subsequent steps are executed again. Hereinafter, the same operation is performed, and the digital display 32 is operated.
Displays the second test result, and the printer 33 outputs the second test result. The number of tests at this time is, for example, In JISC2101 (electrical insulating oil test method), the above test is repeated five times for one sample.
When all the tests are completed (step 109), the power switch 20 is turned off and the process ends.

As is apparent from the above operation, when performing a withstand voltage test of the insulating oil, it is only necessary to press the start switch 42. Since the switching power supply 20 is used for increasing the voltage, the response and the accuracy of the increase are increased. Is very good. In addition, since the digital display 32 is used as the display, the display accuracy is high, and the numbers are not erroneously recognized. Further, when the second test is performed, zero point adjustment (return to zero) as in the related art is not required at all, so that the operability is excellent and the skill is not required.
Furthermore, since it does not have a structure that is vulnerable to external force unlike a two-needle voltmeter, there is an advantage that there is no possibility of breakage even in a portable type.

The switching power supply 20 is provided with a saw-tooth wave generator 24 and a variable resistor 26 for changing the shape of the saw-tooth wave. It is easy to make the ascending pattern any pattern. Further, since the switching power supply device has extremely high responsiveness, even if there is a load change or an input voltage change, the stability of the output voltage change pattern is not impaired, and the reproducibility for each test is extremely high.

Further, since the protection switch 51 is provided, the high voltage portion is not exposed to the outside.

FIG. 4 shows a modification of the sawtooth wave generator 24 of FIG. The sawtooth wave generating section 24 'stores one to three sawtooth wave patterns, and any one of the sawtooth wave patterns is selected by the pattern selection operator 26'. For example, if the sawtooth wave of the second pattern is selected, the switching output voltage rises rapidly, and if the third pattern is selected, the switching output voltage rises slowly. Any increase pattern can be set by increasing or changing the storage pattern. Furthermore, it is possible to set not only a rising pattern but also a falling pattern.

[0033]

According to the present invention, the following effects can be obtained.

(1) The switching power supply 20 allows the voltage rising pattern at the time of boosting to be a rising pattern that changes linearly more preferably as a test voltage, instead of a step-like shape.

(2) Since the switching power supply device 20 is used, the responsiveness is good and a desired voltage can be obtained immediately. Further, since the response is extremely high, even if there is a load fluctuation or an input voltage fluctuation, the stability of the output voltage change pattern is not impaired, and the reproducibility for each test is extremely high.

(3) Since a digital display is used, a reading error of the breakdown voltage is eliminated, and the rising voltage changes linearly, so that the resolution is improved and the measurement accuracy of the breakdown voltage is improved.

(4) Since zero point adjustment as in the prior art is unnecessary, the operation is simple and no skill is required.

(5) Since there are no mechanical parts, the maintainability is good and the weight of the entire apparatus can be reduced.

(6) Since the protection switch is provided, it is possible to prevent the high voltage portion from being exposed to the outside, thereby improving safety.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a conventional insulation withstand voltage test apparatus.

FIG. 2 is a configuration diagram of an insulating oil withstand voltage test apparatus according to an embodiment of the present invention.

FIG. 3 is a flowchart illustrating the operation of the apparatus.

FIG. 4 is a modified example of a saw-tooth wave generator.

[Explanation of symbols]

 1-oil cup 2-insulating oil 3-spherical electrode 6-step-up transformer 20-switching power supply 32-digital display 41-OCR (current detector)

Continued on the front page (72) Eiji Hayamizu 4-1-2, Hirano-cho, Chuo-ku, Osaka City, Osaka Prefecture Inside Osaka Gas Co., Ltd. (72) Inventor Shuichi Nihei 1-2-43, Ningyo, Konosu-shi, Saitama ( 72) Inventor Yukihiko Inagaki 1-7-31 Nishinomiyahara, Yodogawa-ku, Osaka City Inside Izumi Electric Co., Ltd. (72) Inventor Kiyoshi Horii 1-31 Nishimiyahara, Yodogawa-ku, Osaka City Inside Izumi Electric F-term (reference) 2G015 AA02 BA01 BA03 BA04 BA06 CA05

Claims (3)

[Claims] 1. A primary side of a transformer, comprising: an insulating oil cup into which an insulating oil to be measured is injected, and a measuring electrode disposed therein; and a transformer for applying a high voltage to the measuring electrode. In the insulation oil withstand voltage test device that detects the voltage when the insulation oil breaks down by sequentially increasing the voltage applied to the insulation oil as a breakdown voltage, the voltage applied to the primary side of the transformer is formed by the switching power supply output. A switching power supply device for continuously increasing the switching power supply output by feeding back an error output between the output and the sawtooth signal to the switching power supply control unit; and a digital device for holding and displaying the peak value of the switching power supply output. An indicator, and a load current detector for detecting a load current of a switching power supply output, wherein the switching power supply device detects a load value of the load current detector. When it becomes a certain level or more, characterized by stopping the operation of the switching power supply apparatus, insulating oil dielectric strength test device. 2. An openable and closable cover for covering an opening of the insulating oil cup, and a protection switch for outputting an operation stop signal of the switching power supply when the cover does not cover the opening. The insulation oil withstand voltage test device according to claim 1, comprising: 3. The insulation oil withstand voltage test device according to claim 1, wherein the switching power supply device includes an operator for selecting or changing a shape of the sawtooth signal.