AC/DC high-voltage test transformer

ACHigh voltage test transformerDetailed Introduction

1ACHigh voltage test transformerOverview:

lightweightACThe lightweight AC/DC high-voltage test transformer is a new type of product produced based on the national standard ZBK-41006-89, which has been greatly improved on the basis of similar products according to the "Test Transformer" standard of the Ministry of Mechanical and Electrical Engineering. This series of products has the characteristics of small size, light weight, compact structure, complete functions, strong universality, and easy use. Specially suitable for conducting insulation strength tests on various high-voltage electrical equipment, electrical components, and insulation materials under frequency or DC high voltage in power systems, industrial and mining enterprises, scientific research departments, etc. It is an important equipment in high-voltage testing.

2、 Usage:

The current limiting resistor R1 in the power frequency withstand voltage test should be selected based on the rated capacity of the test transformer. When the rated output current on the high-voltage side is between 100-300MA, it can be taken as 0.5-1 Ω/V (test voltage); When the rated output current on the high-voltage side is above 1A, 1 Ω/V (test voltage) can be taken. Commonly used as current limiting resistors, the length of the pipe can be considered as 150KV/m, and the pipe and thickness should have sufficient heat capacity (water resistance liquid preparation method: distilled water is added to an appropriate amount of copper sulfate to make various different negative values).

Ball gap and protective resistance: When the voltage exceeds the set value of the ball gap (usually 110% -120% of the test voltage), the ball gap discharges to protect the test sample. The ball gap protection resistor can be selected according to 1 Ω/V (test voltage).

In the power frequency withstand voltage test, the measurement of voltage (instrument voltage) on the low voltage side is not very accurate. The reason is that the test transformer has leakage reactance, and there must be voltage drop or capacitance rise on this leakage reactance, which causes the voltage on the test sample to be lower or higher than the voltage reflected on the low voltage side measurement voltmeter. During the power frequency withstand voltage test, the voltage on the test object is higher than the output voltage of the test transformer, which is known as the capacitance rise phenomenon. During the induction withstand voltage test. The leakage reactance of the test transformer must have a voltage drop. In order to accurately measure the voltage applied to the test sample, an RCF resistive capacitive voltage divider is often connected to the high voltage side to measure the voltage.

IIIACPrecautions for operating the power frequency withstand voltage test:

(1) Test personnel should divide their work and clarify their methods among themselves. And there are dedicated personnel to monitor on-site safety and observe the status of the test samples.

(2) The test sample should be cleaned and dried to avoid damage to the test sample and errors caused by the experiment.

(3) For large-scale experiments, aerial lift tests should generally be conducted. Step up the voltage to the test voltage when the test sample is not connected, calibrate various meters, and adjust the gap.

(4) The boosting speed cannot be too fast and sudden boosting must be prevented. For example, if the voltage regulator suddenly closes when it is not at zero position, the power cannot be suddenly cut off. Generally, the voltage regulator should be tripped when it drops to zero position.

(5) When the voltage rises to the test voltage, start timing. After 1 minute, quickly drop below 1/3 of the test voltage before turning on the power supply.

(6) During the boost or withstand voltage test, if any of the following abnormal conditions are found, the voltage should be immediately reduced, the power should be cut off, the test should be stopped, and the cause should be identified: ① The pointer of the voltmeter swings greatly; ② Discovering insulation burning or smoking; ③ There is abnormal sound inside the test sample.

(7) Before and after the withstand voltage test, the insulation resistance should be measured to check the insulation condition.

In the leakage test, the current limiting resistor R1 is selected at the rated output voltage, and the short-circuit current at the output terminal does not exceed the rectified current of the high-voltage silicon stack. When the rectified current of the voltage silicon stack is 100mA, the current limiting cathode used in the 60KV test device is selected according to R1=60/0,1=600K Ω. The current limiting resistor should be selected according to R1=60/01=600K Ω, and it should have sufficient capacity and surface discharge distance. The high-voltage filter capacitor C1 is generally selected between 0.01-0.1HF. When the capacitance of the test sample is large, C1 can be omitted.

4、 Operation and precautions for leakage test

(1) Before the experiment, it is necessary to check whether the test object is powered off, grounded and discharged, and whether all external connections are wiped clean. It is necessary to strictly prevent the test voltage from being applied to the human working area.

(2) After connecting the wiring of the testing device, it should be rechecked and confirmed to be correct before applying pressure. Special attention should be paid to checking the safety distance between high-voltage equipment and leads, ground, and operators, and whether the shell of the tested object is reliably grounded. The test should be conducted according to the safety regulations.

(3) For large capacity equipment, the voltage should be slowly increased to prevent the charging current of the test sample from burning out the microampere. If necessary, pressure should be applied in stages, and the stable readings of the microampere meter at each voltage level should be read separately.

(4) During the testing process, the test object, testing device, and microampere should be closely monitored. In case of any abnormal phenomena such as breakdown or flicker, the voltage should be immediately reduced, the power should be cut off, and the cause should be identified and recorded in detail.

(5) After the experiment is completed, the voltage should be reduced and the power should be cut off. The test object and the test device itself should be fully discharged.

5、 Precautions

1. Connect the working circuit according to the experiment you conducted. The shell of the test transformer and the shell of the operating system must be reliably grounded, and the x-end (high-voltage tail) of the high-voltage winding of the test transformer and the F-end of the measuring winding must be reliably grounded.

2. When conducting a cascade test, the X end of the low voltage winding, the F end for measuring winding resistance, and the X end (high voltage tail) of the high voltage winding of the second and third stage test transformers are all connected to the outer shell of the current stage test transformer. The outer shells of the second and third stage test transformers must be grounded through insulation brackets.

3. Before turning on the power, the voltage regulator of the operating system must be set to zero before the power can be turned on, closed, and the boost can begin.

4. Starting from scratch, increase the pressure of the rotating regulator handwheel uniformly. The boosting methods include: fast boosting method, which is the 20S step-by-step boosting method; Slow boost method, i.e. 60S step-by-step boost method; The extremely slow boost method is available for selection. Starting from zero, the voltage is raised to 75% of your desired rated test voltage using a certain boosting method and speed. Then, at a rate of 2% per second, the rated test voltage is raised from zero to your desired rated test voltage using a certain boosting method and speed. Pay close attention to the readings of the measuring instruments and the condition of the test sample. If any abnormality is found in the indication of the measuring instrument or the condition of the test object during the boosting process or the testing process, the voltage should be immediately reduced, the power should be cut off, and the situation should be investigated.

5. After the experiment is completed, the voltage regulator should be returned to zero at a constant speed within a few seconds, and then the power should be cut off.

6. This product may be used beyond its rated parameters. Unless necessary for testing, full voltage power on or off is never allowed.

7. When using this product for high-voltage testing, in addition to being familiar with this instruction, it is also necessary to strictly follow the relevant national standards and operating procedures. Reference can be made to GB311-83 "Insulation Coordination and High Voltage Testing Techniques for High Voltage Transmission and Transformation Equipment"; Preventive Testing Regulations for Electrical Equipment, etc.

6、 Main Technical Parameters Table of Test Transformer

（1） Lightweight AC/DC test transformer (see Table 1)

（2） Lightweight AC test transformer (see Table 2)

Table 1: Lightweight AC/DC Test Transformers

Note: This series of products includes 200V series taps, which can be cascaded with two or three units to form high voltages of AC 100KV, 150KV, 200KV, 300KV, DC 140KV, 210 KV, 280 KV, 420 KV. And according to user needs, 5-15 KV medium voltage taps can be extracted from the high-voltage winding for AC withstand voltage testing of the high-voltage machine. And special specifications of test transformers can be customized.

Table 2: Lightweight AC Test Transformers

7、 Product attachments:

1 user manual, 1 product qualification certificate, 1 factory test report, 1 set of test wires

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