If a power cable fails, it can cause large-scale power outages, greatly disrupting normal life and production. Therefore, it is essential to quickly determine the fault length of the cable and then repair it. Using the high-voltage impulse flash method with a cable fault tester to measure the fault length is a very effective approach. This article uses the YTC630Acable fault tester as an example to provide a brief explanation.
Instrument Wiring:
The operator connects the wiring as shown in the figure above, applying a high-voltage, high-current pulse signal to the faulty phase of the cable, causing the fault point to fully discharge. At the moment of discharge, the main unit obtains the reflected echo through the high-voltage impulse flash sampler. By analyzing the reflected echo, the operator can measure the fault length of the cable.
Wiring Method: Connect as shown in the figure above. The following precautions should be noted:
Step 1: Use the four high-voltage wires ABCD provided with the equipment to connect the transformer, pulse capacitor, high-voltage discharge sphere gap, and faulty cable as shown in Figure 2.10.
Step 2: The red clip (C wire) must only be connected to the faulty phase. If connected to a healthy phase, it may either damage the cable or fail to discharge.
Step 3: If the transformer is an AC/DC test transformer, the short-circuit rod of the transformer must be removed and set aside.
Step 4: Ensure the ground wire of the power control box is properly connected.
Step 5: Before raising the voltage, adjust the high-voltage discharge sphere gap to an appropriate distance. The distance between sphere centers of 1mm corresponds to a breakdown voltage of 3KV (generally adjust this distance to 5-6mm). Once the voltage is raised, if adjustment of the high-voltage discharge sphere gap is needed, first cut off the 220V power supply, then use a discharge rod to fully discharge the capacitor. Prevent residual charge from harming personnel!
Step 6: Use the high-voltage impulse flash wire to connect the main unit's signal interface and the high-voltage impulse flash sampler. The sampler should be placed as close as possible to the "D" connection wire in the figure above, making it easier to receive the fault signal.
Step 7: Before disconnecting wires, always cut off the 220V power supply first, then use a discharge rod to fully discharge the capacitor. Ensure there is no residual charge on the capacitor before starting to disconnect wires.
Step 8: During high-voltage discharge, both the fault point and the high-voltage discharge sphere gap will produce intense spark discharges. Do not use this equipment in flammable gas environments. Also, ensure that there are no flammable gases or materials near the entire cable location.
Operation Steps:
Step 1: Start the main unit by pressing and holding the "Power" switch on the panel until the pulse/flash indicator light turns on.
Step 2: The software starts automatically. Click the "Reset" button on the panel to reset the internal test circuit.
Step 3: In the lower left corner of the software, make the following settings:
"Sampling Mode Setting" select "High-Voltage Impulse Flash".
"Test Range" select based on the approximate length of the cable, similar to selecting the range on a multimeter.
"Test Speed/Test Distance" select "Test Distance", and also select the cable type.
Step 4: Notify the cable terminal operator to open this phase.
Step 5: Press the "Sample" button; the main unit is now waiting for high-voltage discharge.
Step 6: Slowly turn the voltage control knob of the power control box of the high-voltage discharge generator clockwise. Simultaneously monitor the output voltage on the voltmeter. When a clear discharge sound is heard from the high-voltage discharge sphere gap, stop adjusting the voltage control knob. At this point, the high-voltage discharge generator will discharge again after 2-3 seconds, and this cycle repeats.
Step 7: When a periodic waveform appears on the main unit's screen, click the "Temporary Store" button once; the waveform is copied to the waveform analysis area.
Step 8: (Note: The original text seems to be cut off here. Based on typical procedures, the next step would be to analyze the waveform to determine the fault distance. However, as the original text is incomplete, we cannot provide a translation for the missing part.)
