What is the difference between DC withstand voltage and AC withstand voltage

1. Voltage application method：

• DC withstand voltage test is a DC test voltage applied to the insulation of electrical equipment, which is higher than its rated working voltage by a certain value and lasts for a certain period of time.

• The AC withstand voltage test is to apply an AC test voltage much higher than the rated voltage to the insulation of electrical equipment and maintain it for a certain period of time.

2. Voltage distribution and investigation direction：

• In the DC withstand voltage test, the voltage is distributed according to the resistance, and the insulation strength of the equipment can only be evaluated in one direction.

• Communication withstand voltage can examine the two polarities of the equipment, and the voltage distribution is closer to the actual operating conditions of the equipment.

3. Test procedure：

• DC withstand voltage needs to be gradually pressurized, and insulation problems can be discovered during the pressurization process. After the test is completed, discharge is also required.

• AC withstand voltage does not require gradual voltage increase, and the test voltage is generally higher than the operating voltage. After passing the test, the equipment will have a larger safety margin.

4. Destructive to insulation：

• Due to the fact that insulation under DC voltage does not produce dielectric loss, the damage to insulation is minimal, and the required testing equipment capacity is also small, making it easy to carry.

• The damage to insulation caused by AC withstand voltage is relatively greater because the test current is capacitive current and requires high-capacity testing equipment.

5. Scope and Limitations of Application：

• Although the DC withstand voltage test can discover some insulation weaknesses, due to the fact that the insulation of most power equipment is composed of composite dielectrics, their weaknesses may not be effectively detected under the action of DC voltage. Especially in recent years, experimental and operational experience has shown that DC withstand voltage cannot effectively detect insulation defects in certain types of cables (such as XLPE cables), and may even cause potential insulation hazards.

• The AC withstand voltage test is more in line with the electrical conditions that power equipment can withstand during operation, and can more effectively identify the insulation strength of power equipment.

In summary, both DC withstand voltage and AC withstand voltage have their own characteristics and applicable ranges. When choosing which type of withstand voltage test to use, it is necessary to comprehensively consider the specific equipment and test purpose.