This morning, a customer called to inquire: 'After completing the AC voltage withstand test, when I use a grounding discharge rod to contact the test object, I can hear a' pop 'discharge sound.'. Why is this? ”During the communication with this client, Ms. Han, the engineer learned that the other party's testing personnel had previously conducted a DC withstand voltage test, but when inserting the short-circuit rod into the silicon stack afterwards, it was not tightened in place (i.e. the silicon stack was not short circuited). Xiao Han did not check this before conducting the AC withstand voltage test and increased the voltage (several thousand volts). After the voltage was reduced and the power was cut off, novice Xiao Han, out of caution, used a grounded discharge rod to touch the test sample and heard the discharge sound. Xiao Han was grateful that he had "taken the extra step" and avoided danger. Out of fear, Xiao Han called to inquire. The engineer emphasized that before using a test transformer with DC output function (such as YD (JZ) or YDC (JZ) type) for AC withstand voltage testing, it is necessary to confirm that the silicon stack is short circuited by a short-circuit rod to avoid accidental increase of DC high voltage and failure to perform grounding discharge after power failure, which may cause electric shock accidents. If discharge sound is heard inside the high-voltage bushing during the boost test, it should be alerted. This is because the short-circuit rod is not tightened properly (i.e. the silicon stack is not short circuited), and the test sample is charged with DC voltage. After reducing the voltage and cutting off the power, the grounding discharge rod should be used to fully release the charge that may remain on the capacitive test sample to avoid electric shock accidents. Before use, the resistance range of a multimeter can be used to measure the resistance value between high voltage head A and high voltage tail X (usually several thousand ohms to tens of thousands of ohms, with no difference between forward and reverse directions). To confirm that the high-voltage silicon stack is reliably short circuited.