Usage of DC High Voltage Generator
When conducting capacitive load tests, be sure to connect a current limiting resistor.
1. Before use, check the integrity of the tester. The connecting cables should have no open circuits or short circuits, and the equipment should have no cracks or other damage.
2. Place the control box and the voltage doubling cylinder in appropriate positions, 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 all be connected separately to the ground terminal of the test object (i.e., single-point grounding). It is strictly forbidden to connect grounding wires in series. For this purpose, use the DHV dedicated grounding wire.
3. Set the power switch to the OFF position and check that the voltage regulator potentiometer is at zero. The overvoltage protection setting is generally 1.1 times the test voltage.
4. Perform a no-load voltage increase to verify that the overvoltage protection setting is sensitive.
5. Turn on the power switch. At this time, the red light is on, indicating that the power is connected.
6. Press the green button, then the green light is on, indicating that the high voltage is connected.
7. Adjust the voltage regulator potentiometer smoothly in the clockwise direction. The output voltage starts to increase from zero. After reaching the required voltage, record the ammeter reading for the specified time, and check whether there are any abnormal phenomena or sounds in the control box and the high-voltage output line.
8. Decrease the voltage, return the voltage regulator potentiometer 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 test object. After confirming that the tester has no abnormal conditions through inspection, you can start the leakage and DC withstand voltage test on the test object. Connect the test object and grounding wire correctly, and after checking, turn on the power.
10. Increase the voltage to the required voltage or current. The voltage increase speed should be about 3-5 kV/s of test voltage. For large capacitive test objects, monitor that the charging current of the ammeter does not exceed the maximum charging current of the tester. For small capacitive test objects such as zinc oxide arresters and magnetic blow arresters, first increase to 95% of the required voltage (current), then slowly and carefully increase to the required voltage (current). Then read the voltage (current) value from the digital display. If you need to perform a 0.75UDC-1mA measurement on a zinc oxide arrester, first increase to the UDC1mA voltage value, then press the yellow button. At this time, the voltage drops to 75% of the original value and remains in this state. At this point, you can read the current. After the measurement, turn the voltage regulator potentiometer counterclockwise back to zero, and press the green button. To increase the voltage again, press the red button.
If necessary, use an external high-voltage divider to compare with the voltage on the control box.
11. After the test, decrease the voltage and turn off the power.
12. Several measurement methods
1) For general measurement, after connecting the wires, first leave the wire connecting the test object suspended, increase to the test voltage, and read the corona and stray current I during the no-load test. Then connect the test object, increase to the test voltage, and read the total current I1. The leakage current of the test object: Io = I1 - I'.
2) When it is necessary to measure the leakage current of the test object, a high-voltage microammeter should be connected in series on the high-voltage side (see figure below).
The microammeter must have a metal shield and should be connected to the test object using a shielded wire. The shield lead of the high-voltage lead should be tightly connected to the shield of the meter terminal. If the surface of the test object is contaminated, to eliminate the influence of surface leakage current, you can tightly wrap a bare metal flexible wire around the high-potential end of the test object for a few turns and connect it to the shield of the high-voltage lead (see figure below).
