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How to connect the DC high voltage generator?

time:2021/2/19   source:华天电力  reading:675 time

When the DC high voltage generator is used as a capacitive load, it should be connected to a current-limiting resistor

1 The tester should be checked for its integrity before use, the connecting cable should not be broken or short-circuited, and the equipment should be free from damage such as cracks.

2. Place the chassis and the pressure doubler in a suitable position and connect the power cord, cable and grounding wire respectively. The protective grounding wire, working grounding wire and the grounding wire of the discharge rod should be connected to the ground wire of the test product separately (ie One point ground). It is strictly forbidden to connect the ground wires in series with each other. For this reason, DHV ground wire should be used.

3. Place the power switch in the off position and check that the potentiometer should be in the zero position. The overvoltage protection setting value is generally 1.1 times of the test voltage.

4. No-load boost to verify whether the overvoltage protection setting is sensitive.

5. Turn on the power switch, the red light is on at this time, indicating that the power is on.

6. Press the green button, the green light is on, indicating that the high voltage is on.

7. Gently adjust the potentiometer in a clockwise direction, and the output terminal will start to boost from zero. After reaching the required voltage, record the reading of the ammeter within the specified time, and check the control box and high-voltage output line for abnormal phenomena and noise.

8. Step down and reset the voltage regulator to zero, then press the red button to cut off the high voltage and turn off the power switch.

9. Perform leakage and DC withstand voltage tests on the sample. After the inspection test is performed to confirm that the tester has no abnormal conditions, the leakage and DC withstand voltage test of the sample can be started. Connect the test product, ground wire, etc., and turn on the power after the inspection is correct.

10. Boost to the required voltage or current. The boost speed is suitable for the test voltage of 3-5kV per second. For the large-capacitance test product, it is necessary to monitor that the charging current of the ammeter does not exceed the charging current of the tester. For small capacitor samples such as zinc oxide arresters and magnetic blown arresters, first increase to 95% of the required voltage (current), and then slowly and carefully increase to the required voltage (current). Then read the voltage (current) value from the digital display. When you need to measure 0.75UDC-1mA on the zinc oxide arrester, first increase to the UDC1mA voltage value, and then press the yellow button, the voltage will drop to 75% of the original at this time, and keep this state. The current can be read at this time. After the measurement, the potentiometer returns to zero counterclockwise and press the green button. Press the green button when you need to boost again.

DC Hipot Tester.png

If necessary, use an external high voltage divider to compare the voltage on the control box.

11. After the test, reduce the voltage and turn off the power supply.

12. Several measurement methods

a. In general measurement, when the wire is connected, first suspend the wire connecting the test product, raise it to the test voltage and then read the corona and stray current I during the dry test, and then connect the test product to the test voltage. Take the total current I1; the leakage current of the sample: Io=I1—I'

b. When the leakage current of the tested product needs to be measured, a high-voltage microammeter should be connected in series on the high-voltage side

c. When the ground terminal of the sample such as zinc oxide and magnetic blower arrester can be detached, the method of connecting an ammeter to the bottom of the sample (ground potential side) can also be used for measurement. When you want to eliminate the influence of the leakage current on the surface of the test product, you can use a soft bare copper wire to wind a few turns on the ground potential end of the test product and connect it with the shield of the shield wire (see the figure below)

13. For small capacitor samples such as zinc oxide arresters, the discharge time is generally very fast through the pressure measuring resistor. For large capacitor test products such as cables, the voltage of the test product is generally self-discharged to less than 20% of the test voltage, and then discharged through the matching discharge rod. After the test product is fully discharged, the grounding wire is hung up before the removal of the high-voltage lead and the replacement of the wiring work are allowed.

14. Operation after protection action

During use, if the green light is off, the red light is on, and the voltage drops, it is the relevant protection action. The power switch should be turned off at this time, and the panel indicators are off. Return the electric potentiometer to the zero position. After one minute, the low-voltage capacitor in the standby mode is fully discharged before allowing the power switch to be turned on again. The no-load test can be performed again and the boost test can be performed again after finding the situation.

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